JP4134313B2

JP4134313B2 - Method for producing conductive powder

Info

Publication number: JP4134313B2
Application number: JP2002214887A
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: 2002-07-24
Filing date: 2002-07-24
Publication date: 2008-08-20
Anticipated expiration: 2022-07-24
Also published as: JP2004055486A

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こ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おり、例えば、特開平７−２３２９２０号、特開平７−２３５２１４号、特開平８−２１７４４６号、特開平６−８０４２２号などが挙げられる。
【０００４】
【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ＩＴＯ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、特に経時変化は１０倍近い変化率を示すことがあり、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。
【０００５】
さらに、導電性粉末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。
【０００６】
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、特に、これらの特性の経時変化の少ないＳｎ含有Ｉｎ酸化物からなる導電材及びその製造方法並びに導電性塗料及び導電性塗膜を提供することにある。
【０００７】
【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、金（Ａｕ）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。）後、安定化処理することによって得られた赤系色調を有するＩＴＯ粒子が導電性及び透過特性に優れ、さらに、これらの特性の経時変化を抑止でき、上記の目的を達成できることを見出した。
【０００８】
すなわち、本発明は、第１に、Ｓｎ含有Ｉｎ酸化物中に３価Ａｕを含有してなり且つＩｎ、Ｓｎ及びＡｕの総モル数に対してＳｎが０ . ５〜１５モル％、Ａｕが０ . ０２〜５モル％であって、ＣＩＥ１９７６Ｌ＊ａ＊ｂ＊色空間における明度指数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の赤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アルカリおよび３価Ａｕ含有溶液を添加して液温５０℃以上で中和することにより得られたＡｕ、Ｓｎ含有Ｉｎ水酸化物の沈殿を加熱処理し、次いで、該加熱処理温度から室温まで大気雰囲気中で冷却する安定化処理を行うことを特徴とする導電性粉末の製造方法；第２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記載の導電性粉末の製造方法；第３に、Ｓｎ含有Ｉｎ酸化物中に３価Ａｕを含有してなり且つＩｎ、Ｓｎ及びＡｕの総モル数に対してＳｎが０ . ５〜１５モル％、Ａｕが０ . ０２〜５モル％であって、ＣＩＥ１９７６Ｌ＊ａ＊ｂ＊色空間における明度指数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の赤系色調を有する導電性粉末の製造にあたり、アルカリに３価Ａｕ含有溶液およびＩｎとＳｎを含有する酸性溶液を添加して液温１０〜７０℃で中和することにより得られたＡｕ、Ｓｎ含有Ｉｎ水酸化物の沈殿を加熱処理し、次いで、該加熱処理温度から室温まで大気雰囲気中で冷却する安定化処理を行うことを特徴とする導電性粉末の製造方法；第４に、前記中和後液のｐＨが６〜１２である第３記載の導電性粉末の製造方法；第５に、前記加熱処理温度が３００〜１０００℃である第１〜４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。
【０００９】
【発明の実施の形態】
本発明に係る導電性粉末にあっては、Ｉｎ、Ｓｎ及びＡｕ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２．０〜１０．０モル％含まれる。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とともに、明度指数Ｌ＊値が２５未満となって赤系色調が暗すぎるからである。また、Ｉｎ、Ｓｎ及びＡｕの総モル数に対してＡｕが好ましくは０．０２〜５モル％、更に好ましくは０．２〜１．０モル％含まれる。Ａｕの含有量が０．０２モル％未満では導電性が低下し、さらに赤系色調を達成できず、一方、５モル％を超えると明度指数Ｌ＊値が２５未満となって赤系色調が暗すぎるからである。
【００１０】
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）における明度指数Ｌ＊値は好ましくは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。
【００１１】
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。
【００１２】
本発明の特徴的な赤系色調を有しかつ経時変化の少ない導電性を有するＩＴＯ粉は、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う間にＡｕ含有溶液を添加することにより、Ｓｎ、Ａｕ含有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うか、または予備焼成を行うことなく３００〜１０００℃の温度で加熱処理し、次いで、大気雰囲気中での冷却による安定化処理を行うことより得ることができる。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、Ａｕ含有溶液および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１０〜７０℃の温度で添加する短時間の逆中和処理によってもよい。
【００１３】
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。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。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。
【００１４】
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、針状等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逆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粒子となる。
【００１５】
得られたＡｕ、Ｓｎ含有Ｉｎ水酸化物を焼成し、脱水分解、焼結を行うことによって前記水酸化物粒子の形状異方性を維持して棒状、針状または類似した形状の酸化物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。
【００１６】
加熱処理温度は、水酸化物のサイズ、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。
【００１７】
焼成して得られるＡｕ、Ｓｎ含有Ｉｎ酸化物粉は、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、棒状等の形状を有する酸化物粉であり、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Ａｕ、Ｓｎ含有Ｉｎ酸化物粉にあっては、粒径が２００ｎｍ以下であることが好ましく、１００ｎｍ以下がさらに好ましい。
【００１８】
Ａｕ、Ｓｎ含有Ｉｎ酸化物粉の長軸径は、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Ａｕ、Ｓｎ含有Ｉｎ酸化物にあっては、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。
【００１９】
本発明においては、特に、焼成して得られたＡｕ、Ｓｎ含有Ｉｎ酸化物粉を焼成温度から常温まで、大気雰囲気中において冷却して表面酸化させるという安定化処理を行うことを特徴とする。
金（Ａｕ）は、酸化処理を行ってもなお、酸化物Ａｕ_２Ｏ_３から単体のＡｕになろうとする傾向が強く、電気伝導の媒体となる電子を放出し易いため、粉体の電気伝導性が高くなり、特徴的に、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）における明度指数Ｌ＊値、クロマティクネス指数ａ＊値、ｂ＊値がそれぞれ、２５〜８５、＋１．０〜＋４０．０、＋１．０〜＋４０．０の赤系色調を有するものとなる。
【００２０】
また、特に、本発明の安定化処理においては、３００〜１０００℃の加熱処理後の高温から大気雰囲気中で冷却させるという酸化処理を実施するため、製造後の経時変化が殆どなく５０〜４００℃という製膜処理中の温度においても更に酸化されることがなく、品質が極めて安定したものになる。
なお、因みに、例えばクロマティクネス指数ａ＊値とｂ＊値がそれぞれ、＋１〜＋４０と−１〜−４０の粒子は紫系色調を有し、−１〜−４０と−１〜−４０の粒子は青系色調を有し、−１〜−４０と＋１〜＋４０の粒子は緑系色調を有する。
【００２１】
上記のＡｕ、Ｓｎ含有Ｉｎ酸化物粉を溶媒中に分散させて塗料化し、塗布後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、従来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、塗布成膜後バインダーを成膜して固定してもよい。
【００２２】
【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。
【００２３】
〔実施例１〕Ｉｎを１８ｗｔ％含有する塩酸溶液２００ｇを純水で２．９Ｌとし、さらに塩化第２スズ５．４ｇを混合してＩｎ、Ｓｎ含有酸性溶液とし、この酸性溶液を出発溶液としてガラスビーカーに仕込んだ。また、金０.３０ｇを王水に溶解し、Ａｕ含有溶液を作成した。
４８％ＮａＯＨ溶液１０８．２ｇを純水８９０ｇで希釈し、このアルカリ溶液をＩｎ、Ｓｎ含有酸性溶液に添加した。
先ず、はじめに液温２０℃のＩｎ、Ｓｎ含有酸性溶液に、アルカリ溶液を１５分間かけて添加しｐＨ３に予備中和した。次いで液温を９０℃まで上昇して残りのアルカリ溶液およびＡｕ含有溶液を４０分かけて添加した。最終のｐＨは１０．０であった。得られた液を濾過し、沈殿を脱水、乾燥して、Ａｕ、Ｓｎ含有Ｉｎ水酸化物の沈殿を得た。このＡｕ、Ｓｎ含有Ｉｎ水酸化物のＴＥＭ写真を図１に示す。このＳｎ、Ａｕ含有Ｉｎ水酸化物の長軸径は１３５ｎｍ、短軸径は２４ｎｍ、長軸径／短軸径の軸比は５．６であった。
【００２４】
次いで、このＡｕ、Ｓｎ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ガスの雰囲気中において、６００℃で２時間焼成した。この焼成物の焼成温度から室温までの冷却を大気中で行うことにより安定化処理を行った。これによって得られたＡｕ、Ｓｎ含有Ｉｎ酸化物粒子のＴＥＭ写真を図２として示した。このＡｕ、Ｓｎ含有Ｉｎ酸化物粒子は、長軸径が１２５．６３ｎｍ、短軸径は３１．７４ｎｍ、長軸径／短軸径の比は３．９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、倍率換算してその平均値を求めた。
さらに、軸比は前記の長軸径と短軸径の比率より算出した。得られた粉体の比表面積をＢＥＴ１点法により測定したところ、２６．８ｍ^２／ｇであった。また結晶子径Ｄｘは１８０Åであった。
【００２５】
このＡｕ、Ｓｎ含有Ｉｎ酸化物粉は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が７４．６６、クロマティクネス指数ａ＊値が＋１０．９９およびｂ＊値が＋１７．５７の赤系色調を示していた。
【００２６】
この粉末６ｇと溶剤（エタノール）１８ｇおよ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製し、ガラス板にスピンコートした後、２００℃で３０分間乾燥し、膜厚０．１μｍの透明導電性塗膜を作成した。作成した膜の抵抗値を測定したところ２．０１ｋΩ／□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９７．２２％であり、良好な透明導電性膜が得られた。このガラス板を温度６０℃、湿度９０％の恒温恒湿器に２４時間保存後に膜の抵抗値を測定したところ２．２３ｋΩ／□で、経時変化として１．１倍であり低い値であった。
【００２７】
〔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を混合してＩｎ、Ｓｎ含有酸性溶液として、２５℃に温度調節した。また、塩化金酸・四水和物２．８３１ｇを水に溶解し、Ａｕ含有溶液とした。この２つの溶液を別々に２５℃に温度調節した上記アルカリ溶液に添加した。最終のｐＨは９．５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。
【００２８】
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。この焼成物の焼成後から室温までの冷却を大気中で行うことにより安定化処理を行った。この得られた平均径４０ｎｍ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５５．９４、クロマティクネス指数ａ＊値が＋１２．５２およびｂ＊値が＋６．４８の赤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２２ｍ^２／ｇであった。また結晶子径Ｄｘは２１０Åであった。
【００２９】
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、抵抗値は２．１２ｋΩ／□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９８．０１％であり、良好な透明導電性膜が得られた。このガラス板を温度６０℃、湿度９０％の恒温恒湿器に２４時間保存後（以下単に、２４時間後という。）に膜の抵抗値を測定したところ２．３７ｋΩ／□で、経時変化として１．１倍であり低い値であった。
【００３０】
〔比較例１〕Ａｕ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。
【００３１】
次いで、大気放冷による安定化処理を行わない以外は実施例１と同様条件で、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３．８の針状粉であった。この得られた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の青系色調を示していた。
【００３２】
このＳｎ含有Ｉｎ酸化物粉末を用い、塗料を作成し、塗膜を作成した。膜の抵抗値は３．６７ｋΩ／□、透過率は９７．２０％であった。２４時間後の抵抗値は９．９０ｋΩ／□であり、経時変化は２．７倍であった。
このＡｕの添加がなく、安定化処理を行わないこの比較例１のＳｎ含有Ｉｎ酸化物粉の場合塗膜では抵抗値が高く、特に、顕著に大きい経時変化を示した。
【００３３】
〔比較例２〕Ａｕ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、大気放冷による安定化処理は行わない以外は実施例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酸化物粉は平均粒径が４５ｎｍの粒状粉であった。この得られた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６６．５３、クロマティクネス指数ａ＊値が−７．４３、ｂ＊値が−１１．８の青系色調を示していた。
【００３４】
この粉末により塗料を作成し、塗膜を作成し、その抵抗を測定したところ、４．８１ｋΩ／□で、透過率は９７．０２％であった。２４時間後の抵抗値は１４．１ｋΩ／□であり、経時変化は２．９倍であった。
Ａｕを含むことなく、安定化処理も行わないこの比較例２のＳｎ含有Ｉｎ酸化物粉の場合の塗膜では抵抗値が高く、特に、顕著に大きい経時変化を示した。
【００３５】
〔比較例３〕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と塩化金酸・四水和物２．８３１ｇを混合してＩｎ、Ｓｎ、Ａｕの混合溶液として、２５℃に温度調節した。この混合溶液を２５℃に温度調節した上記アルカリ溶液に添加した。最終のｐＨは９．５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。
次いで、この沈殿を管状炉に入れ、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時間焼成した後に、この雰囲気中のままでこの焼成物を室温まで冷却して、Ａｕ、Ｓｎ含有Ｉｎ酸化物粉を得た。このＡｕ、Ｓｎ含有Ｉｎ酸化物粉は平均径が４０ｎｍの粒状粉であった。また、この得られた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４６．１７、クロマティクネス指数ａ＊値が＋３．５５およびｂ＊値が−１４．７５の紫系色調を示していた。
【００３６】
この粉末による塗料で塗膜を作成し、その抵抗を測定したところ、２．０９ｋΩ／□で、透過率は９８．１５％であった。２４時間後の抵抗値は３．２１ｋΩ／□であり、経時変化は１．５倍であった。すなわち、塗膜の抵抗値は低いが、経時変化が大きいという問題がある。
【００３７】
【発明の効果】
本発明によれば、Ａｕを含有するＳｎ含有Ｉｎ水酸化物を弱還元雰囲気で焼成した後、焼成粉の冷却を大気中での放冷によって行うという効率的な製法により、赤系色調で抵抗値が低く、その経時変化率の少ないＡｕ、Ｓｎ含有Ｉｎ酸化物粉末（Ａｕ含有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Ａｕ、Ｓｎ含有Ｉｎ水酸化物粉のＴＥＭ像を示す写真である。
【図２】図１のＡｕ、Ｓｎ含有Ｉｎ水酸化物粉を焼成しかつ安定化処理して得られたＡｕ、Ｓｎ含有Ｉｎ酸化物粉のＴＥＭ像を示す写真である。
【図３】比較例１におけるＳｎ含有Ｉｎ水酸化物粉のＴＥＭ像を示す写真である。
【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像を示す写真である。[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 has been attempted to obtain these various particle shapes. For example, JP-A-7-232920, JP-A-7-235214, Examples include Kaihei 8-217446 and JP-A-6-80422.
[0004]
[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 production, and the cost is high, and in the ITO particle coating method of 2) Improvements in properties such as conductivity and transmittance are not always sufficient. Particularly, the change with time may show a change rate close to 10 times, and the mixed particle coating method of 3) is not always sufficient with the above properties.
In general, the conductive coating film according to the above 2) and 3) is used as an electromagnetic wave shielding film for a cathode ray tube. The fact is that there is a limitation.
[0005]
Furthermore, the improvement in the shape of the conductive powder alone improves the 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 transmitted light with respect to directly transmitted light). However, even if the transmittance is sufficient, there are problems such as insufficient conductivity and lack of electromagnetic shielding properties.
[0006]
Accordingly, an object of the present invention is to provide a conductive material composed of a Sn-containing In oxide that is a low-cost coating type and has excellent conductivity and transmission characteristics, in particular, these characteristics have little change over time, and a method for producing the same. And providing a conductive paint and a conductive coating film.
[0007]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have conducted a heat treatment (firing) on a tin-containing indium hydroxide added with gold (Au) (referred to as Sn-containing In hydroxide) in a weak reducing atmosphere. After that, the ITO particles having a red color tone obtained by the stabilization treatment are excellent in conductivity and transmission characteristics, and further, the change of these characteristics over time can be suppressed, thereby achieving the above object. I found out that I can do it.
[0008]
That is, according to the present invention, first, trivalent Au is contained in the Sn-containing In oxide, Sn is 0.5 to 15 mol%, and Au is the total number of moles of In, Sn and Au . from 0.02 to 5 and the mole%, CIE 1976 L * a * b * lightness L * value in the color space is 25 to 85, chromaticness indices a * value and b * both value +1. 0 ~ + 40.0 in the production of the conductive powder having a reddish 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 precipitate of Au and Sn-containing In hydroxide obtained by adding an alkali and trivalent Au-containing solution and neutralizing at a liquid temperature of 50 ° C. or higher is subjected to heat treatment, and then from the heat treatment temperature to room temperature. It is necessary to carry out a stabilization process that cools in the atmosphere. Method for producing a conductive powder and symptoms; Second, the pH of the pre-neutralization after fluid is 2-3, the conductive powder of the first described pH of the neutralizing solution after it is 7-12 manufacturing process;.. third, and in and also contains a trivalent Au in the Sn-containing in oxide and Sn based on the total mole number of Sn and Au 0 5 to 15 mol%, Au 0 02 a 5 mol%, a lightness index L * value in CIE 1976 L * a * b * color space is 25 to 85, chromaticness indices a * value and b * both values +1. 0 + 40. Au produced by adding a trivalent Au-containing solution and an acidic solution containing In and Sn to an alkali and neutralizing at a liquid temperature of 10 to 70 ° C. in the production of a conductive powder having a red color tone of 0 The precipitate of the Sn-containing In hydroxide is heat treated, and then the heat treatment temperature is reached. Method for producing a conductive powder which is characterized in that the stabilization process of cooling in the atmosphere to room temperature; the fourth, of the conductive powder of the 3 wherein pH of said neutralized solution after it is 6-12 Production method: Fifth, the method for producing a conductive powder according to any one of the first to fourth aspects , wherein the heat treatment temperature is 300 to 1000 ° C.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the conductive powder according to the present invention, Sn is preferably contained in an amount of 0.5 to 15 mol%, more preferably 2.0 to 10.0 mol%, based on the total number of moles of In, Sn and Au. . If the Sn content is less than 0.5 mol%, the conductivity decreases. On the other hand, if it exceeds 15 mol%, the conductivity also decreases, and the lightness index L * value is less than 25 and the red color tone is dark. It is because it is too much. Further, Au is preferably contained in an amount of 0.02 to 5 mol%, more preferably 0.2 to 1.0 mol%, based on the total number of moles of In, Sn and Au. If the Au content is less than 0.02 mol%, the conductivity is lowered, and further, a red color tone cannot be achieved. On the other hand, if the Au content exceeds 5 mol%, the lightness index L * value is less than 25 and the red color tone is reduced. Because it is too dark.
[0010]
The lightness index L * value in the L * a * b * color space (measurement light source C: color temperature 6774K) established by CIE (International Commission on Illumination) 1976 is preferably 25 to 85, more preferably 30 to 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 the method of the present invention cannot practically realize it. Further, the chromaticness index a * value and b * value in the above are both preferably +1.0 to +40.0, and more preferably +2.5 to +30.0. This is because if the chromaticness index a * value or b * value is less than +1.0, the color becomes dull and lacks vividness. On the other hand, if the value exceeds +40.0, there is no problem, but it is practically realized by the manufacturing method of the present invention. It is not possible.
[0011]
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 / 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 > 0.008856, X, Y, Z are tristimulus values of the object color, and X ₀ , Y ₀ , Z ₀ are the object colors. The tristimulus values of the illuminating light source are normalized to Y ₀ = 100.
[0012]
The ITO powder having the characteristic reddish color tone of the present invention and having conductivity with little change over time is obtained by using an In hydrochloric acid (which may be nitric acid, sulfuric acid, etc.) solution containing Sn as a starting solution. Contains Au during neutralization over time after pre-neutralization at a liquid temperature of 45 ° C. or lower with an alkali solution such as KOH, NH ₄ OH, or NH ₄ HCO ₃ and then raising the temperature to 50 ° C. or higher. By adding a solution, a precipitate of Sn, Au-containing In hydroxide is obtained, and this precipitate is pre-baked at a temperature of 300 ° C. or lower in the air or the like, or 300-1000 ° C. without pre-baking. It can obtain by performing the heat processing by this temperature, and then performing the stabilization process by cooling in air | atmosphere atmosphere. Alternatively, the acidic solution is not neutralized by an alkaline solution, but an Au-containing solution and an In acidic solution containing Sn are compared with an alkaline solution at a temperature of 10 to 70 ° C. without particularly raising the temperature in the middle. A short-time reverse neutralization treatment may be performed.
[0013]
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 shape can be controlled by 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 during neutralization, hydroxide particles having a desired particle size and shape can be produced relatively uniformly.
[0014]
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 it takes 2-3 hours if the temperature rise time is included, but hydroxide powder consisting of rod-like, needle-like particles, etc. This is fired to obtain rod-like or needle-like oxide particles having excellent conductivity. In the reverse neutralization method in which an acidic solution is added to an alkaline solution, the neutralization time is a short time of 0.5 to 15 minutes, but the crystal powder becomes spherical or granular particles.
[0015]
The obtained Au, Sn-containing In hydroxide is calcined, dehydrated, decomposed, and sintered to maintain the shape anisotropy of the hydroxide particles, and the rod-shaped, needle-shaped or similar shaped oxide particles Can be obtained. 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.
[0016]
The heat treatment temperature is set according to the size, shape, and firing atmosphere gas of the hydroxide. The higher the heat treatment temperature, the more water vapor, the stronger the reducing property, the more the sintering proceeds, and the resulting oxide The shape anisotropy of the is low. 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.
[0017]
Au, Sn-containing In oxide powder obtained by firing preferably has a major axis diameter of 500 nm or less, more preferably 200 nm or less, a minor axis diameter of 100 nm or less, more preferably 50 nm or less, The oxide powder has a rod-like shape, and the axial ratio of the major axis diameter / minor axis diameter is preferably 1.5 to 10, and more preferably 3 to 10. In addition, in the spherical or granular Au and Sn-containing In oxide powder, the particle size is preferably 200 nm or less, and more preferably 100 nm or less.
[0018]
When the major axis diameter of the Au and Sn-containing In oxide powder 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, 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 spherical or granular Au and Sn-containing In oxides, the resistance value may increase from the viewpoint of the degree of contact between the particles. In particular, the diameter is 200 nm or less, preferably 100 nm or less. 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.
[0019]
In the present invention, in particular, a stabilization treatment is performed in which the Au and Sn-containing In oxide powder obtained by firing is cooled in the air atmosphere from the firing temperature to room temperature to be surface oxidized.
Gold (Au) has a strong tendency to become single Au from the oxide Au ₂ O ₃ even after oxidation treatment, and easily emits electrons as a medium for electric conduction. The lightness index L * value, the chromaticness index a * value in the color space (measurement light source C: color temperature 6774K), characteristically, CIE (International Commission on Illumination) 1976 The b * values have a red color tone of 25 to 85, +1.0 to +40.0, and +1.0 to +40.0, respectively.
[0020]
In particular, in the stabilization treatment of the present invention, the oxidation treatment of cooling in the air atmosphere from the high temperature after the heat treatment at 300 to 1000 ° C. is carried out, so that there is almost no change with time after the production, and the temperature is 50 to 400 ° C. Even at the temperature during the film-forming process, it is not further oxidized and the quality becomes extremely stable.
Incidentally, for example, particles having a chromaticness index a * value and b * value of +1 to +40 and −1 to −40 have a purple color tone, and particles of −1 to −40 and −1 to −40, respectively. Has a blue color tone, and particles of -1 to -40 and +1 to +40 have a green color tone.
[0021]
A conductive film having high permeability can be obtained by dispersing the Au and Sn-containing In oxide powders in a solvent to form a paint, and volatilizing the solvent after application to fix the film. A conventional 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.
[0022]
【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.
[0023]
[Example 1] 200 g of a hydrochloric acid solution containing 18 wt% of In was made 2.9 L with pure water, and further 5.4 g of stannic chloride was mixed to form an acidic solution containing In and Sn. This acidic solution was used as a starting solution. Prepared in a glass beaker. Further, 0.30 g of gold was dissolved in aqua regia to prepare an Au-containing solution.
108.2 g of 48% NaOH solution was diluted with 890 g of pure water, and this alkaline solution was added to the acidic solution containing In and Sn.
First, an alkaline solution was added to an In and Sn-containing acidic solution having a liquid temperature of 20 ° C. over 15 minutes to pre-neutralize to pH 3. Next, the liquid temperature was raised to 90 ° C., and the remaining alkaline solution and Au-containing solution were added over 40 minutes. The final pH was 10.0. The obtained liquid was filtered, and the precipitate was dehydrated and dried to obtain a precipitate of Au and Sn-containing In hydroxide. A TEM photograph of this Au, Sn-containing In hydroxide is shown in FIG. The major axis diameter of the Sn, Au-containing In hydroxide was 135 nm, the minor axis diameter was 24 nm, and the major axis / minor axis ratio was 5.6.
[0024]
Next, this Au, Sn-containing In hydroxide was put in a tubular furnace, and 1.5 vol. % Water vapor and 0.05 vol. In% of NH ₃ _{N 2} in an atmosphere of a gas containing a gas, calcined for 2 hours at 600 ° C.. Stabilization was performed by cooling the fired product from the firing temperature to room temperature in the air. A TEM photograph of the Au and Sn-containing In oxide particles thus obtained is shown in FIG. The Au and Sn-containing In oxide particles were rod-shaped particles having a major axis diameter of 125.63 nm, a minor axis diameter of 31.74 nm, and a major axis / minor axis ratio of 3.9. The major axis diameter and the 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. It was 26.8 m < ² > / g when the specific surface area of the obtained powder was measured by the BET 1 point method. The crystallite diameter Dx was 180 mm.
[0025]
This Au, Sn-containing In oxide powder has a lightness index L * value of 74.66, a chromaticness index a * value of +10.99 and a b * value in the L * a * b * color space established by the CIE (1976). Showed a reddish color tone of +17.57.
[0026]
6 g of this powder, 18 g of solvent (ethanol), and 0.3 g of an anionic surfactant as a dispersing agent are placed in a planetary ball mill (Frichche P-5 type, container capacity 80 mL, PSZ 0.3 mm ball) and rotated at 300 rpm for 30 minutes. Rotate, add colloidal silica and ethanol to this dispersion, create a paint with ITO powder content of 2%, silica content of 2%, balance ethanol, and spin coat on glass plate, It dried at 200 degreeC for 30 minute (s), and produced the transparent conductive coating film with a film thickness of 0.1 micrometer. The resistance value of the prepared film was measured and found to be 2.01 kΩ / □. Further, when the transmittance was measured with a spectrophotometer, the transmittance was 97.22%, and a good transparent conductive film was obtained. When this glass plate was stored in a thermostat at a temperature of 60 ° C. and a humidity of 90% for 24 hours, the resistance value of the film was measured and found to be 2.23 kΩ / □, which was 1.1 times as a change with time and was a low value. .
[0027]
[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% of In was made 1.5 L with pure water, and 21.19 g of SnCl ₄ .5H ₂ O was further mixed to adjust the temperature to 25 ° C. as an In and Sn-containing acidic solution. Further, 2.831 g of chloroauric acid tetrahydrate was dissolved in water to obtain an Au-containing solution. The two solutions were added separately to the alkaline solution adjusted to 25 ° C. The final pH was 9.5. This was filtered, dehydrated and dried to obtain a precipitate of Au and Sn-containing In hydroxide.
[0028]
Next, this Au, Sn-containing In hydroxide was put in a tubular furnace, and 1.5 vol. % Water vapor and 0.05 vol. Baking was performed at 600 ° C. for 2 hours in an N ₂ gas atmosphere containing% NH ₃ gas. Stabilization was performed by cooling the fired product to room temperature after firing. The resulting spherical Au, Sn-containing In oxide particles having an average diameter of 40 nm have a lightness index L * value of 55.94 and a chromaticness index a * in the L * a * b * color space established by CIE (1976). It had a reddish shade with a value of +12.52 and a b * value of +6.48. It was 22 m < ² > / g when the specific surface area of the obtained powder was measured by the BET 1 point method. The crystallite diameter Dx was 210 mm.
[0029]
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) and rotated at 300 rpm for 30 minutes. 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 2.12 kΩ / □. When the transmittance was measured with a spectrophotometer, the transmittance was 98.01%, and a good transparent conductive film was obtained. When this glass plate was stored in a constant temperature and humidity chamber at 60 ° C. and 90% humidity for 24 hours (hereinafter simply referred to as 24 hours later), the resistance value of the film was measured and found to be 2.37 kΩ / □. The value was 1.1 times lower.
[0030]
[Comparative Example 1] A hydrochloric acid acidic solution was prepared under the same conditions as in Example 1 except that Au was not added. The alkaline solution was added to the hydrochloric acid acidic solution, and after preliminary neutralization, the liquid temperature was raised to neutralize. Then, filtration, dehydration and drying were performed to obtain Sn-containing In hydroxide. A TEM photograph of this Sn-containing In hydroxide is shown in FIG.
[0031]
Next, the Sn-containing In hydroxide was obtained by firing this Sn-containing In hydroxide under the same conditions as in Example 1 except that the stabilization treatment by air cooling was not performed. A TEM photograph of this Sn-containing In oxide is shown in FIG.
This Sn-containing In oxide was acicular powder having a major axis diameter of 156.66 nm, a minor axis diameter of 40.70 nm, and an axial ratio of 3.8. The obtained Sn-containing In oxide particles have a lightness index L * value of 76.82, a chromaticness index a * value of −8.27 and b in the L * a * b * color space defined by CIE (1976). * A blue color tone having a value of -4.05 was shown.
[0032]
Using this Sn-containing In oxide powder, a coating material was prepared and a coating film was prepared. The resistance value of the film was 3.67 kΩ / □, and the transmittance was 97.20%. The resistance value after 24 hours was 9.90 kΩ / □, and the change with time was 2.7 times.
In the case of the Sn-containing In oxide powder of Comparative Example 1 in which this Au was not added and the stabilization treatment was not performed, the coating film had a high resistance value, and in particular, showed a significantly large change with time.
[0033]
[Comparative Example 2] A Sn-containing In hydroxide was obtained by treatment under the same conditions as in Example 2 except that Au was not added. Subsequently, the same baking as Example 2 was performed except not performing the stabilization process by air cooling, and Sn containing In oxide powder was obtained. The obtained Sn-containing In oxide powder was a granular powder having an average particle diameter of 45 nm. The obtained Sn-containing In oxide particles had a lightness index L * value of 66.53, a chromaticness index a * value of −7.43, b in the L * a * b * color space established by CIE (1976), b. * A blue color tone having a value of -11.8 was indicated.
[0034]
A coating was prepared from this powder, a coating film was prepared, and the resistance was measured. As a result, it was 4.81 kΩ / □ and the transmittance was 97.02%. The resistance value after 24 hours was 14.1 kΩ / □, and the change with time was 2.9 times.
The coating film in the case of the Sn-containing In oxide powder of Comparative Example 2 that does not contain Au and does not perform the stabilization treatment has a high resistance value, and in particular, shows a significantly large change with time.
[0035]
[Comparative Example 3] 550 g of 25% ammonia water 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% of In is made 1.5 L with pure water, and 21.19 g of SnCl ₄ .5H ₂ O and 2.831 g of chloroauric acid tetrahydrate are mixed to mix In, Sn, and Au. As a solution, the temperature was adjusted to 25 ° C. This mixed solution was added to the alkaline solution whose temperature was adjusted to 25 ° C. The final pH was 9.5. This was filtered, dehydrated and dried to obtain a precipitate of Au and Sn-containing In hydroxide.
The precipitate was then placed in a tubular furnace and 1.5 vol. % Water vapor and 0.05 vol. After firing at 600 ° C. for 2 hours in an atmosphere of N ₂ gas containing 1% NH ₃ gas, the fired product was cooled to room temperature in this atmosphere, and Au, Sn-containing In oxide powder Got. This Au, Sn-containing In oxide powder was a granular powder having an average diameter of 40 nm. Further, the obtained Sn-containing In oxide particles had a lightness index L * value of 46.17, a chromaticness index a * value of +3.55 in the L * a * b * color space of CIE establishment (1976), and The b * value showed a purple color tone of -14.75.
[0036]
A coating film was prepared with this powder paint, and its resistance was measured. As a result, it was 2.09 kΩ / □ and the transmittance was 98.15%. The resistance value after 24 hours was 3.21 kΩ / □, and the change with time was 1.5 times. That is, the resistance value of the coating film is low, but there is a problem that the change with time is large.
[0037]
【The invention's effect】
According to the present invention, the Sn-containing In hydroxide containing Au is fired in a weak reducing atmosphere, and then the fired powder is cooled by being allowed to cool in the air, thereby being resistant to reddish color tone. The effect is that it is possible to obtain Au, Sn-containing In oxide powder (Au-containing ITO powder), a conductive paint and a conductive coating film having a low value and a low rate of change with time.
[Brief description of the drawings]
1 is a photograph showing a TEM image of Au, Sn-containing In hydroxide powder in Example 1. FIG.
2 is a photograph showing a TEM image of Au and Sn-containing In oxide powder obtained by firing and stabilizing the Au and Sn-containing In hydroxide powder of FIG. 1. FIG.
3 is a photograph showing a TEM image of Sn-containing In hydroxide powder in Comparative Example 1. FIG.
4 is a photograph showing a TEM image of Sn-containing In oxide powder obtained by firing the Sn-containing In hydroxide powder of FIG. 3. FIG.

Claims

Ｓｎ含有Ｉｎ酸化物中に３価Ａｕを含有してなり且つＩｎ、Ｓｎ及びＡｕの総モル数に対してＳｎが０ . ５〜１５モル％、Ａｕが０ . ０２〜５モル％であって、ＣＩＥ１９７６Ｌ＊ａ＊ｂ＊色空間における明度指数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の赤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アルカリおよび３価Ａｕ含有溶液を添加して液温５０℃以上で中和することにより得られたＡｕ、Ｓｎ含有Ｉｎ水酸化物の沈殿を加熱処理し、次いで、該加熱処理温度から室温まで大気雰囲気中で冷却する安定化処理を行うことを特徴とする導電性粉末の製造方法。 Sn content In contain trivalent Au in the oxide becomes and In, the Sn based on the total mole number of Sn and Au 0. 5 to 15 mol%, a Au is 0.02 to 5 mol% a lightness index L * value in CIE 1976 L * a * b * color space is 25 to 85, both chromaticness indices a * and b * values have +1. 0 + 40. 0 reddish shades In producing conductive powder , alkali is added to an acidic solution containing In and Sn and pre-neutralized at a liquid temperature of 45 ° C. or lower, and an alkali and trivalent Au-containing solution is further added to the pre-neutralized solution. Then, the precipitation of Au and Sn-containing In hydroxide obtained by neutralization at a liquid temperature of 50 ° C. or higher is heat-treated, and then a stabilization treatment is performed in which the precipitate is cooled from the heat treatment temperature to room temperature in an air atmosphere. Conductive powder manufacturing method characterized by .

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記載の導電性粉末の製造方法。The method for producing a conductive powder according to claim 1 , 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３価Ａｕを含有してなり且つＩｎ、Ｓｎ及びＡｕの総モル数に対してＳｎが０ . ５〜１５モル％、Ａｕが０ . ０２〜５モル％であって、ＣＩＥ１９７６Ｌ＊ａ＊ｂ＊色空間における明度指数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の赤系色調を有する導電性粉末の製造にあたり、アルカリに３価Ａｕ含有溶液およびＩｎとＳｎを含有する酸性溶液を添加して液温１０〜７０℃で中和することにより得られたＡｕ、Ｓｎ含有Ｉｎ水酸化物の沈殿を加熱処理し、次いで、該加熱処理温度から室温まで大気雰囲気中で冷却する安定化処理を行うことを特徴とする導電性粉末の製造方法。 Sn content In contain trivalent Au in the oxide becomes and In, the Sn based on the total mole number of Sn and Au 0. 5 to 15 mol%, a Au is 0.02 to 5 mol% a lightness index L * value in CIE 1976 L * a * b * color space is 25 to 85, both chromaticness indices a * and b * values have +1. 0 + 40. 0 reddish shades In production of conductive powder, Au and Sn-containing In hydroxides obtained by adding a trivalent Au-containing solution and an acidic solution containing In and Sn to an alkali and neutralizing at a liquid temperature of 10 to 70 ° C. A method for producing a conductive powder, comprising subjecting the precipitate to a heat treatment, and then performing a stabilization treatment of cooling from the heat treatment temperature to room temperature in an air atmosphere.

前記中和後液のｐＨが６〜１２である、請求項３記載の導電性粉末の製造方法。The manufacturing method of the electroconductive powder of Claim 3 whose pH of the said liquid after neutralization is 6-12.

前記加熱処理温度が３００〜１０００℃である、請求項１〜４のいずれかに記載の導電性粉末の製造方法。The manufacturing method of the electroconductive powder in any one of Claims 1-4 whose said heat processing temperature is 300-1000 degreeC.