JP4134314B2

JP4134314B2 - Method for producing conductive powder

Info

Publication number: JP4134314B2
Application number: JP2002269084A
Authority: JP
Inventors: 剛聡藤野; 辰美稲村; 義史堀川
Original assignee: Dowa Electronics Materials Co Ltd
Current assignee: Dowa Electronics Materials Co Ltd
Priority date: 2002-09-13
Filing date: 2002-09-13
Publication date: 2008-08-20
Anticipated expiration: 2022-09-13
Also published as: JP2004111106A

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３価元素を含有してなり且つＩｎ、Ｓｎ及び該３価元素の総モル数に対してＳｎが０ . ５〜１５モル％、該３価元素が０ . ０１〜１５モル％含有され、ＣＩＥ１９７６Ｌ＊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の青系色調を有する導電性粉末の製造にあたり、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液温４５℃以下で予備中和し、該予備中和された液にさらにアルカリを添加して液温５０℃以上で中和することにより得られた沈殿を加熱処理することによって導電性粉末を製造する方法；第２に、Ｓｎ含有Ｉｎ酸化物中にＩｎ以外の３価元素を含有してなり且つＩｎ、Ｓｎ及び該３価元素の総モル数に対してＳｎが０ . ５〜１５モル％、該３価元素が０ . ０１〜１５モル％含有され、ＣＩＥ１９７６Ｌ＊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の青系色調を有する導電性粉末の製造にあたり、ＩｎとＳｎを含有する酸性溶液にアルカリを添加して液温４５℃以下で予備中和し、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液温５０℃以上で中和することにより得られた沈殿を加熱処理することによって導電性粉末を製造する方法；第３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１または２に記載の方法；第４に、Ｓｎ含有Ｉｎ酸化物中にＩｎ以外の３価元素を含有してなり且つＩｎ、Ｓｎ及び該３価元素の総モル数に対してＳｎが０ . ５〜１５モル％、該３価元素が０ . ０１〜１５モル％含有され、ＣＩＥ１９７６Ｌ＊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の青系色調を有する導電性粉末の製造にあたり、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液温１０〜９０℃で中和することにより得られた沈殿を加熱処理することによって導電性粉末を製造する方法；第５に、前記中和後液のｐＨが６〜１２である第４記載の方法；第６に、前記加熱処理温度が３００〜１０００℃である第１〜５のいずれかに記載の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、ＣＩＥ１９７６Ｌ＊ａ＊ｂ＊色空間とは、国際照明委員会（ＣＩＥ）が１９７６年にＣＩＥＸＹＺ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、ＣＩＥ１９７６Ｌ＊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_２Ｏ２１．１９ｇ、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]
BACKGROUND OF THE INVENTION
The present invention relates to a tin-containing indium oxide (represented as Sn-containing In oxide, 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]
Sn-containing In oxides are 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 producing these conductive films include 1) those by sputtering, 2) those that apply ITO particles, and 3) those that apply mixed particles of metal and ITO.
[0003]
Among these, for the conductive coating film, a conductive path is formed by contact between ITO particles. Therefore, the shape of the particles that can easily obtain this conductive path is, for example, particles such as flakes, rods, needles, and plates. Thus, it is possible to improve the conductivity, and attempts to obtain these various particle shapes have been made (for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4). reference.).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-232920
[Patent Document 2]
JP 7-235214 A
[Patent Document 3]
JP-A-8-217446
[Patent Document 4]
Japanese Patent Laid-Open No. 6-80422
[0005]
[Problems to be solved by the invention]
However, the sputtering method of 1) above is excellent in properties such as conductivity and transmittance, but it requires expensive equipment such as a vacuum device in the manufacturing process, resulting in high cost. 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 coating film according to the above 2) and 3) is used for an electromagnetic wave shielding film of a cathode ray tube, but its conductivity is still lower than that of the film obtained by the sputtering method of the above 1). The fact is that there is a limitation.
[0006]
Furthermore, the improvement in the shape of the conductive powder particles alone improves the electrical conductivity, but cannot achieve optical properties such as transmittance. In particular, a lot of scattered light is generated, and the haze of the coating film (diffuse transmission of direct transmitted light). There is a problem that the ratio of light) is large, or conversely, even if the transmittance is sufficient, there are problems such as insufficient conductivity and lack of electromagnetic shielding properties.
[0007]
Accordingly, an object of the present invention is to provide a conductive powder comprising a Sn-containing In oxide having a low-cost coating type and excellent conductivity and transmission characteristics, a method for producing the same, and a conductive paint using the same. And providing a conductive coating film.
[0008]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have weakened tin-containing indium hydroxide (indicated as Sn-containing In hydroxide) in which a trivalent element other than In is added. It has been found that the ITO particles subjected to heat treatment (sometimes referred to as firing) in a reducing atmosphere can improve conductivity and transmission characteristics and achieve the above-mentioned object.
[0009]
  That is, the present invention firstly,The Sn-containing In oxide contains a trivalent element other than In, and Sn is 0 with respect to the total number of moles of In, Sn, and the trivalent element. . 5 to 15 mol%, the trivalent element is 0 . In the CIE 1976 L * a * b * color space, the lightness index L * value is 25 to 85, and both the chromaticness index a * value and b * value are −1. . 0 to -40 . In the production of conductive powder having a blue color tone of 0In addition, an alkali is added to the acidic solution containing In, Sn and the trivalent element and pre-neutralized at a liquid temperature of 45 ° C. or lower, and an alkali is further added to the pre-neutralized liquid to a liquid temperature of 50 ° C. or higher. A method for producing a conductive powder by heat-treating a precipitate obtained by neutralization with a second;The Sn-containing In oxide contains a trivalent element other than In, and Sn is 0 with respect to the total number of moles of In, Sn, and the trivalent element. . 5 to 15 mol%, the trivalent element is 0 . In the CIE 1976 L * a * b * color space, the lightness index L * value is 25 to 85, and both the chromaticness index a * value and b * value are −1. . 0 to -40 . In the production of conductive powder having a blue color tone of 0Then, an alkali is added to an acidic solution containing In and Sn and pre-neutralized at a liquid temperature of 45 ° C. or lower, and the trivalent element and alkali are further added to the pre-neutralized liquid to a liquid temperature of 50 ° C. or higher. A method for producing a conductive powder by heat-treating a precipitate obtained by neutralization with a third; third, the pH of the pre-neutralized solution is 2-3, and the pH of the post-neutralized solution Is 7-12As described in the first or secondMethod; Fourth,The Sn-containing In oxide contains a trivalent element other than In, and Sn is 0 with respect to the total number of moles of In, Sn, and the trivalent element. . 5 to 15 mol%, the trivalent element is 0 . In the CIE 1976 L * a * b * color space, the lightness index L * value is 25 to 85, and both the chromaticness index a * value and b * value are −1. . 0 to -40 . In the production of conductive powder having a blue color tone of 0The conductive powder is produced by heating the precipitate obtained by adding the trivalent element-containing solution and the acidic solution containing In and Sn to the alkali and neutralizing at a liquid temperature of 10 to 90 ° C. Method: Fifth, the pH of the solution after neutralization is 6-124th describedMethod; Sixth, the heat treatment temperature is 300 to 1000 ° C.Any one of 1-5A method is provided.
[0010]
DETAILED DESCRIPTION OF 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 these In, Sn, and trivalent elements. It is contained in mol%, more preferably 0.8 to 10 mol%. This is because if the Sn content is less than 0.5 mol%, the conductivity is lowered, while if it exceeds 15 mol%, the conductivity is also lowered. Further, the trivalent element is preferably contained in an amount of 0.01 to 15 mol% with respect to the total number of moles of In, Sn, and trivalent elements, although the more preferable range varies depending on the type of element. This is because if the content of the trivalent element is less than 0.01 mol%, the conductivity is lowered, while if it exceeds 15 mol%, the conductivity is also lowered. Here, the trivalent element used in the present invention may be Al, Ga, Tl or the like of the same group as In, or may be rare earth Y, La, Nd, Eu, Gd, Dy, Ho, Er, Yb, or the like. Furthermore, 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 elements and the more preferable addition range that is optimal depending on the type of the element, is unclear at present.
[0011]
For the blue color tone of the conductive powder according to the present invention, the lightness index L * value is preferably in the CIE (International Lighting Commission) 1976 established L * a * b * color space (measurement light source C: color temperature 6774K). 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 is practically impossible to achieve with the manufacturing method of the present invention. In addition, the chromaticness index a * value and b * value in the above are preferably both −1.0 to −40.0, and more preferably −2.5 to −30.0. This is because when the chromaticness index a * value and b * value are less than −1.0, the color becomes dull and lacks vividness. This is because it cannot be realized.
[0012]
The CIE 1976 L * a * b * color space is a CIE XYZ color system converted by the International Commission on Illumination (CIE) in 1976, and a constant distance within the color system is almost perceived by any color region. The color space is determined so as to have a uniform rate difference. Further, the lightness index L * value, chromaticness index a * value, and b * value are quantities determined by an orthogonal coordinate system in the CIE 1976 L * a * b * color space, and the following formulas (A) to ( C).
L * = 116 (Y / Y₀)^1/3-16 (A)
a * = 500 [(X / X₀)^1/3-(Y / Y₀)^1/3  ] (B)
b * = 200 [(Y / Y₀)^1/3-(Z / Z₀)^1/3  ] (C)
However, X / X₀, Y / Y₀, Z / Z₀> 0.008856, X, Y, Z are tristimulus values of the object color, X₀, Y₀, Z₀Is the tristimulus value of the light source that illuminates the object color.₀= 100.
[0013]
The characteristically conductive ITO powder of the present invention is a solution of In hydrochloric acid (nitric acid, sulfuric acid, etc.) containing a trivalent element and Sn as a starting solution, and NaOH, KOH, NH.₄OH or NH₄HCO₃Of the In hydroxide containing Sn and the trivalent element by performing a neutralization treatment over time after the temperature was raised to 50 ° C. or higher after preliminary neutralization at a liquid temperature of 45 ° C. or less with an alkali solution such as After obtaining a precipitate and pre-baking the precipitate at a temperature of 300 ° C. or lower in the air or the like, or without performing pre-baking, the precipitate can be obtained by performing a heat treatment at a temperature of 300 to 1000 ° C. Further, without adding the trivalent element from the beginning, for example, it may be added together with the alkaline solution after the temperature rise. Alternatively, the acidic solution is not neutralized with an alkaline solution, but a solution containing a trivalent element and an In acidic solution containing Sn are not particularly heated in the middle of the alkaline solution. A short-time reverse neutralization treatment at a temperature of 0 ° 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., more preferably 15 to 25 ° C. The post-reaction solution is preferably pH 2-3. This preneutralization treatment is intended to generate fine particle nuclei. Subsequent neutralization treatment is performed by raising the temperature of the post-reaction solution in 30 minutes to 2 hours and raising the temperature to 50 ° C. or higher, preferably 80 to 95 ° C. to grow the fine particle nuclei. Thus, a rod-like, needle-like or plate-like hydroxide is produced. The neutralized solution is preferably pH 7-12. Pre-neutralization neutralization rate (the ratio of the amount of In precipitated by pre-neutralization when the total In amount is 1), temperature, pH, etc. can control the particle shape, and pre-neutralization By adjusting the time zone and the temperature range during neutralization, hydroxide particles having a desired particle size and shape can be produced relatively uniformly.
[0015]
Neutralization treatment is performed in a higher temperature bath than pre-neutralization treatment, and it takes 50 minutes or more only by neutralization operation, and takes 2-3 hours when the temperature rise time is included, but water consisting of rod-like, needle-like or plate-like particles Oxide powder is obtained, and this is fired to obtain rod-like, needle-like oxide particles having excellent conductivity. In the neutralization method in which an acidic solution is added to the alkaline solution, the neutralization time is a short time of 0.5 to 15 minutes, but the crystal powder becomes spherical or granular powder particles.
[0016]
The obtained In hydroxide containing the trivalent element and Sn is fired, dehydrated and decomposed, and sintered to obtain granular, spherical, rod-like, needle-like or similar oxide powder particles. Obtainable. The firing atmosphere is a weak reducing atmosphere with an inert gas containing water vapor or an inert gas containing water and a reducing gas such as ammonia. That is, the particles after the dehydration decomposition of the hydroxide have poor crystallinity, and the conductivity becomes low unless the crystals are grown. In order to promote the sintering, it is desirable to add water vapor to the firing atmosphere and to contain reducing ammonia or hydrogen gas in order to increase the conductivity.
[0017]
The heat treatment temperature is set according to the size, shape, and firing atmosphere gas of the hydroxide particles, but the higher the heat treatment temperature, the more water vapor, the stronger the reducing property, the more the sintering proceeds, and the resulting oxidation The shape anisotropy of the product particles is lowered. The firing temperature is preferably 300 to 1000 ° C, more preferably 300 to 700 ° C. Crystallization of the hydroxide particles can be promoted by firing at the above temperature and atmosphere to maintain the shape anisotropy, and the desired oxide particles can be obtained. However, decomposition of the hydroxide is insufficient at temperatures below 300 ° C., and when it exceeds 1000 ° C., it becomes difficult to maintain the shape anisotropy of the hydroxide particles, and there is much aggregation due to interparticle sintering. Thus, dispersibility is reduced.
[0018]
The In oxide powder particles containing trivalent elements 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, more preferably 50 nm or less. Thus, the oxide powder particles have a needle-like, rod-like or plate-like shape, and the major axis / minor axis diameter ratio is preferably 1.5 to 10, and more preferably 3 to 10.
Further, in the In oxide powder containing spherical or granular trivalent elements and Sn, the particle diameter is preferably 200 nm or less, and more preferably 100 nm or less.
[0019]
When the long axis diameter of the In oxide powder particles containing the trivalent element and Sn exceeds 500 nm, visible light scattering occurs, and optical characteristics such as transmittance deteriorate. In particular, when the major axis diameter is 200 nm or less, the scattering of visible light is further suppressed. On the other hand, if the minor axis diameter exceeds 100 nm, the degree of contact between the particles is low, and the coating film conductivity is low. In particular, when the minor axis diameter is 50 nm or less, the coating film conductivity is further improved. When the axial ratio of the major axis diameter to the minor axis diameter is out of the range of 1.5 to 10, the conductivity, dispersibility, and intra-crystallinity are deteriorated. In the case of In oxide powder particles containing spherical or granular trivalent elements and Sn, the resistance value may increase in terms of the degree of contact between the particles. In particular, the diameter is 200 nm or less, preferably 100 nm or less. To do. The preferable crystallite diameter Dx calculated from the half width of the (222) plane by X-ray diffraction is preferably 150 mm or more from the viewpoint of conductivity.
[0020]
In oxide powder containing the above trivalent element and Sn is dispersed in a solvent to form a paint, 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 as a coating method. As a solvent, an organic solvent such as alcohol, ketone or ether, a surfactant, a coupling agent or the like as a dispersant is added, and a dispersing device such as a bead mill. Use to disperse. Further, a binder serving as a binder may be added, or a binder may be formed and fixed after coating film formation.
[0021]
【Example】
EXAMPLES The present invention will be described in more detail with reference to the following 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 wt% of In was made 2.9 L with pure water, and 5.4 g of stannic chloride and 1.5 g of aluminum nitrate. The solution was placed in a glass beaker. 108.2 g of 48% NaOH solution is diluted with 890 g of pure water, and this alkaline solution is added to the acidic solution. First, an alkaline solution is first added to an acidic solution having a liquid temperature of 20 ° C. for 15 minutes to pre-neutralize to pH 3. Next, the liquid temperature is raised to 90 ° C., and the remaining alkali 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. A transmission electron micrograph (referred to as a TEM photograph) of this Sn, Al-containing In hydroxide is shown in FIG. 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 major axis diameter / minor axis diameter was 5.4.
[0023]
Next, this Sn, Al-containing In hydroxide was put in a tubular furnace, and 1.5 vol. % Water vapor and 0.05 vol. % NH₃N containing gas₂Firing 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. The major axis diameter is 150.16 nm, the minor axis diameter is 33.36 nm, and the major axis diameter / short. The shaft diameter ratio was 4.50. The major axis diameter and minor axis diameter were obtained by measuring the major axis diameter and minor axis diameter of 50 particles in the TEM photograph with calipers, and converting the magnification to obtain the average value. Further, the axial ratio was calculated from the ratio of the major axis diameter to 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 the L * a * b * color space defined by CIE (1976). And b * value had a blue color tone of −9.67. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 22.5 m.²/ G. Crystallite diameter D_xWas 180cm.
[0024]
6 g of this powder, 18 g of a solvent (ethanol) and 0.3 g of an anionic surfactant as a dispersing agent are placed in a planetary ball mill (Fricche P-5 type, container capacity 80 mL, PSZ 0.3 mm ball) for 30 minutes at a rotation speed of 300 rpm. Rotate, add colloidal silica and ethanol to this dispersion, create a paint with an ITO powder content of 2%, a silica content of 2% and the balance ethanol, and spin coat on a glass plate, The film was dried at 200 ° C. for 30 minutes to produce a transparent conductive film having a thickness of 0.3 μm. When the resistance value of the prepared film was measured, the resistance value was 1.40 kΩ / □. When the transmittance was measured with 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 as a starting solution, and charged into a glass beaker. 800 g of hydrochloric acid solution containing 18 wt% In is made 1.5 L with pure water, and SnCl₄・ 5H₂21.19 g of O and 0.70775 g of chloroauric acid tetrahydrate were added as a mixed solution to the alkaline solution adjusted to 50 ° C. and added to the alkaline solution 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, Sn-containing In hydroxide was put in a tubular furnace, and 1.5 vol. % Water vapor and 0.05 vol. % NH₃N containing gas₂Firing was performed at 600 ° C. for 2 hours in a gas atmosphere. The resulting spherical Au, 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 the L * a * b * color space defined by CIE (1976). It had a blue 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 1-point method, it was 26.0 m.²/ G. The crystallite diameter Dx was 240 mm.
[0027]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 1.59 kΩ / □. When the transmittance was measured with 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. Subsequently, 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 diameter of 45 nm. The obtained granular Bi, Sn-containing In oxide particles have a lightness index L * value of 63.54 and a chromaticness index a * value of −7 in the CIE established (1976) L * a * b * color space. It had a blue hue with a .59 and b * value of -7.21. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 27.5 m.²/ G. The crystallite diameter Dx was 221 mm.
[0029]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance of the prepared film was measured, the resistance value was 2.43 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 96.28%, and a good transparent conductive film was obtained.
[0030]
[Example 4] Instead of aluminum nitrate, iron oxide (Fe₂O₃) A Sn and Fe-containing In hydroxide was obtained under the same conditions as in Example 1 except that 0.14 g was added. Subsequently, the same baking as Example 1 was performed and Sn and Fe containing In oxide powder were obtained. The obtained Sn, Fe-containing In oxide powder particles are rod-like particles having a major axis diameter of 141.6 nm, a minor axis diameter of 32.07 nm, and a major axis / minor axis ratio of 4.42. In the established (1976) L * a * b * color space, the lightness index L * value is 69.85, the chromaticness index a * value is -4.42, and the b * value is -8.16. Was. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 20.3 m.²/ G. The crystallite diameter Dx was 205 mm.
[0031]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 1.70 kΩ / □. When the transmittance was measured with 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 indium nitrate solution containing 100 g / L indium was used instead of indium chloride solution, and 0.45 g of thallium oxide was added instead of aluminum nitrate. As a result, an In hydroxide containing Sn and Tl was obtained. Subsequently, the same baking as Example 1 was performed and Sn and Tl containing In oxide powder was obtained. 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 ratio of major axis diameter / minor axis diameter 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 18.7 m.²/ G. The crystallite diameter Dx was 162 mm.
[0033]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared 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 / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 92.09%, and a good transparent conductive film was obtained.
[0034]
[Example 6] A Sn and Nd-containing In hydroxide was obtained by treating under the same conditions as in Example 1 except that 0.2 g of neodymium oxide was added instead of aluminum nitrate. Subsequently, the same baking as Example 1 was performed and Sn and Nd containing In oxide powder was obtained. The obtained Sn and Nd-containing In oxide powder particles were rod-like particles having a major axis diameter of 117.7 nm, a minor axis diameter of 36.91 nm, and a major axis / minor axis ratio of 3.19. This particle has 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 23.2 m.²/ G. The crystallite diameter Dx was 181 mm.
[0035]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 1.99 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 98.25%, and a good transparent conductive film was obtained.
[0036]
[Example 7] Al, Fe, and Sn-containing In hydroxides were obtained by the same treatment as in Example 1 except that 0.15 g of iron oxide was added instead of reducing aluminum nitrate to 0.65 g. Subsequently, the same baking as in Example 1 was performed to obtain an Al, Fe, Sn-containing In oxide powder. The obtained Sn, Al, 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 ratio of major axis diameter / minor axis diameter of 4.45. It was. This particle has 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 24.5 m.²/ G. The crystallite diameter Dx was 172 mm.
[0037]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 1.59 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 96.01%, and a good transparent conductive film was obtained.
[0038]
Example 8 Sn and Al-containing In hydroxides were treated under the same conditions as in Example 1 except that sodium aluminate was used instead of aluminum nitrate and neutralized with an alkaline solution in which sodium aluminate was dissolved. Obtained. Subsequently, the same baking as Example 1 was performed and Sn and Al containing In oxide powder was obtained. 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 major axis / minor axis ratio of 3.85. . This particle has 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 21.93 m.²/ G. The crystallite diameter Dx was 190 mm.
[0039]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 1.78 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 95.27%, and a good transparent conductive film was obtained.
[0040]
[Example 9] A Sn and Y-containing In hydroxide was obtained under the same conditions as in Example 1 except that 0.55 g of yttrium chloride hexahydrate was added instead of aluminum nitrate. Subsequently, the same baking as Example 1 was performed and Sn and Y containing In oxide powder were obtained. The obtained Sn, 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 23.56 m.²/ G. The crystallite diameter Dx was 198 mm.
[0041]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared 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 with a spectrophotometer, the transmittance was 98.23%, and a good transparent conductive film was obtained.
[0042]
[Example 10] A Sn and Al-containing In hydroxide was obtained under the same conditions as in Example 2 except that 2.7 g of aluminum nitrate nonahydrate was added instead of chloroauric acid. Next, the same firing 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 diameter 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 29.0 m.²/ G. The crystallite diameter Dx was 207 mm.
[0043]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 2.38 kΩ / □. Further, when the transmittance was measured with 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 no trivalent element other than In was added. The mixture was neutralized, filtered, dehydrated and dried to obtain Sn-containing In hydroxide. A TEM photograph of this Sn-containing In hydroxide is shown in FIG.
[0045]
Next, this Sn-containing In hydroxide was fired under the same conditions as in Example 1 to obtain a Sn-containing In oxide. A TEM photograph of this Sn-containing In oxide is shown in FIG. This Sn-containing In oxide was acicular 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. This particle has 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 23.7 m.²/ G. The crystallite diameter Dx was 214 mm.
[0046]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 3.67 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 97.20%. The coating film in the case of the Sn-containing In oxide powder of Comparative Example 1 in which no trivalent element other than In was added showed a significantly high resistance value.
[0047]
[Comparative Example 2] A hydrochloric acid acidic solution 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 the hydrochloric acid acidic solution to perform preliminary neutralization. Thereafter, neutralization was performed by raising the liquid temperature, and filtration, dehydration and drying were performed to obtain Pd and Sn-containing In hydroxide. A TEM photograph of this Pd, Sn-containing In hydroxide is shown in FIG.
[0048]
Next, this Pd, Sn-containing In hydroxide was fired under the same conditions as in Example 1 to obtain Pd, Sn-containing In oxide. A TEM photograph of this Pd, Sn-containing In oxide is shown in FIG.
The Pd and Sn-containing In oxide powder particles did not retain the needle shape of hydroxide, and were granular with a major axis diameter of 45.9 nm, a minor axis diameter of 30.77 nm, and an axial ratio of 1.49. This particle has 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 20.5 m.²/ G. The crystallite diameter Dx was 232 mm.
[0049]
Using this Pd, Sn-containing In oxide powder, a transparent conductive film having a film thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 6.43 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 92.23%. There was no addition of trivalent elements other than In, and the coating film in the case of the Pd, Sn-containing In oxide powder of Comparative Example 2 to which divalent palladium was added showed a remarkably high resistance value.
[0050]
[Comparative Example 3] A Sn-containing In hydroxide was obtained by treatment under the same conditions as in Example 2 except that no trivalent element other than In was added. Subsequently, the same baking 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. This particle has 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 CIE established (1976) L * a * b * color space. It had a blue color tone. When the specific surface area of the obtained powder was measured by the BET 1-point method, it was 28.0 m.²/ G. The crystallite diameter Dx was 240 mm.
[0051]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was prepared in the same manner as in Example 1. When the resistance value of the prepared film was measured, the resistance value was 4.81 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 97.02%. The coating film in the case of the Sn-containing In oxide powder of Comparative Example 3 containing no trivalent element other than In exhibited a remarkably high resistance value.
[0052]
【The invention's effect】
According to the present invention, a trivalent element having a low resistance value and an excellent transmittance by an efficient manufacturing method in which a Sn-containing In hydroxide containing a trivalent element other than In is fired in a weak reducing atmosphere or the like. The Sn-containing In oxide powder containing ITO (ITO powder), the conductive paint and the conductive coating film can be obtained.
[Brief description of the drawings]
1 is a TEM photograph of Al, Sn-containing In hydroxide powder in Example 1. FIG.
2 is a TEM photograph of Al and Sn-containing In oxide powder obtained by firing the Al and Sn-containing In hydroxide powder of FIG. 1. FIG.
3 is a TEM photograph of Sn-containing In hydroxide powder in Comparative Example 1. FIG.
4 is a TEM photograph of Sn-containing In oxide powder obtained by firing the Sn-containing In hydroxide powder of FIG. 3. FIG.
5 is a TEM photograph of Pd, Sn-containing In hydroxide powder in Comparative Example 2. FIG.
6 is a TEM photograph of Pd, Sn-containing In oxide powder obtained by firing the Pd, Sn-containing In hydroxide powder of FIG. 5. FIG.

Claims

Ｓｎ含有Ｉｎ酸化物中にＩｎ以外の３価元素を含有してなり且つＩｎ、Ｓｎ及び該３価元素の総モル数に対してＳｎが０ . ５〜１５モル％、該３価元素が０ . ０１〜１５モル％含有され、ＣＩＥ１９７６Ｌ＊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の青系色調を有する導電性粉末の製造にあたり、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液温４５℃以下で予備中和し、該予備中和された液にさらにアルカリを添加して液温５０℃以上で中和することにより得られた沈殿を加熱処理することによって導電性粉末を製造する方法。 Sn-containing In oxide and and also contains a trivalent element other than In the In, Sn and Sn based on the total moles of the trivalent element is from 0.5 to 15 mol%, the trivalent element is 0 In the CIE 1976 L * a * b * color space, the lightness index L * value is 25 to 85, and both the chromaticness index a * value and the b * value are −1.0 . -40. in the production of the conductive powder having a bluish color tone of 0, an in, by adding an alkali to an acidic solution containing Sn and the trivalent element pre neutralized at a liquid temperature of 45 ° C. or less,該予Btsutyuu A method of producing a conductive powder by heat-treating a precipitate obtained by further adding an alkali to the summed liquid and neutralizing at a liquid temperature of 50 ° C. or higher.

Ｓｎ含有Ｉｎ酸化物中にＩｎ以外の３価元素を含有してなり且つＩｎ、Ｓｎ及び該３価元素の総モル数に対してＳｎが０ . ５〜１５モル％、該３価元素が０ . ０１〜１５モル％含有され、ＣＩＥ１９７６Ｌ＊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の青系色調を有する導電性粉末の製造にあたり、ＩｎとＳｎを含有する酸性溶液にアルカリを添加して液温４５℃以下で予備中和し、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液温５０℃以上で中和することにより得られた沈殿を加熱処理することによって導電性粉末を製造する方法。 Sn-containing In oxide and and also contains a trivalent element other than In the In, Sn and Sn based on the total moles of the trivalent element is from 0.5 to 15 mol%, the trivalent element is 0 In the CIE 1976 L * a * b * color space, the lightness index L * value is 25 to 85, and both the chromaticness index a * value and the b * value are −1.0 . -40. 0 in the production of the conductive powder having a bluish color tone, pre neutralized at a liquid temperature of 45 ° C. or less by adding an alkali to an acidic solution containing in and Sn, to the pre-neutralized solution Further, a method for producing a conductive powder by heat-treating a precipitate obtained by adding the trivalent element and alkali and neutralizing at a liquid temperature of 50 ° C. or higher.

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、請求項１または２に記載の方法。 The method according to claim 1 or 2, wherein the pre-neutralized solution has a pH of 2 to 3, and the post-neutralized solution has a pH of 7 to 12.

Ｓｎ含有Ｉｎ酸化物中にＩｎ以外の３価元素を含有してなり且つＩｎ、Ｓｎ及び該３価元素の総モル数に対してＳｎが０ . ５〜１５モル％、該３価元素が０ . ０１〜１５モル％含有され、ＣＩＥ１９７６Ｌ＊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の青系色調を有する導電性粉末の製造にあたり、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液温１０〜９０℃で中和することにより得られた沈殿を加熱処理することによって導電性粉末を製造する方法。 Sn-containing In oxide and and also contains a trivalent element other than In the In, Sn and Sn based on the total moles of the trivalent element is from 0.5 to 15 mol%, the trivalent element is 0 In the CIE 1976 L * a * b * color space, the lightness index L * value is 25 to 85, and both the chromaticness index a * value and the b * value are −1.0 . -40. in the production of the conductive powder having a bluish color tone 0, by neutralizing by adding an acidic solution containing the trivalent element-containing solution and in and Sn in an alkali at a liquid temperature of 10 to 90 ° C. A method for producing a conductive powder by heat-treating the obtained precipitate.

前記中和後液のｐＨが６〜１２である、請求項４記載の方法。 The method according to claim 4 , wherein the post-neutralization solution has a pH of 6-12.

前記加熱処理温度が３００〜１０００℃である、請求項１〜５のいずれかに記載の方法。 The method in any one of Claims 1-5 whose said heat processing temperature is 300-1000 degreeC.