JP2004182812A - Electrically conductive coating and method for forming electrically conductive coating film using the same - Google Patents
Electrically conductive coating and method for forming electrically conductive coating film using the same Download PDFInfo
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、導電性塗料及びそれを用いた導電性塗膜の形成方法並びに導電性塗膜を有する基材の製造方法に関し、特に、塗装適性に優れ、導電性と透明性が高いものに関する。
【０００２】
【従来の技術】
ブラウン管（ＣＲＴ）、液晶ディスプレイ（ＬＣＤ）等の表示機器の表示面、クリーンルーム等の窓材、ＩＣパッケージ等の包装材として用いられるガラス、プラスチックス、あるいは、オーバーヘッドディスプレイ（ＯＨＰ）、写真等に用いられるフィルムのような各種透明性基材は、一般的に絶縁体であり、静電気を帯び易い。このため、表面にゴミ、埃などが付着し易く、美観を損ねるばかりでなく、視認性の低下、製品への混入による不良品の発生、電子機器の誤動作等の問題が生じた。特に、電子機器の場合は、静電気自体も誤作動等の原因となった。また、近年パーソナルコンピューターやテレビの画面から発生する電磁波が、人体に与える影響が問題になっている。
【０００３】
そこで、帯電防止や電磁波遮蔽のために、導電性粒子を配合した導電性塗料を、基材表面に塗布することが、通常行われている。導電性粒子とてしては、平均粒子径が１〜１００ｎｍ程度の金属コロイド粒子と呼ばれる金属粒子（例えば、非特許文献１、特許文献１参照）や、比表面積が２０〜１５０ｍ２／ｇ程度の酸化スズ、酸化インジウム、酸化亜鉛等の導電性酸化物の微粒子が用いられている。金属コロイド粒子や導電性酸化物の微粒子は可視光を透過する性質を有し、前記の透明性基材に適しており、中でも金属コロイド粒子は導電性が非常に高いので、特に電磁波遮蔽に用いられ、導電性酸化物の微粒子は、低コストであるので、帯電防止に用いられるのが一般的である。
【０００４】
このような導電性粒子を用いた導電性塗料では、第一液が導電性粒子と分散媒を含み、実質的に硬化性成分を含まず、第二液に硬化性成分を含む二液性塗料として用いられており、導電性粒子として金属コロイド粒子を用いたもの（例えば、特許文献２参照）、導電性酸化物を用いたもの（例えば、特許文献３参照）等が知られている。これは、第一液を基材に塗布し、導電性粒子を含む層を形成した後、第二液を塗布して硬化性成分を硬化させ、導電性塗膜を得るもので、導電性粒子と基材との接点に、絶縁性の硬化性成分が介在し難く、導電経路が形成され易いため、導電性粒子の優れた導電性を発現させることができる。
【０００５】
【非特許文献１】
エム キャリー リー（Ｍ Ｃａｒｅｙ Ｌｅａ），「アメリカン ジャーナル オブ サイセンス」（Ａｍｅｒｉｃａｎ Ｊｏｕｒｎａｌ ｏｆ Ｓｃｉｅｎｃｅ），１８８９，第３７巻，Ｐ４７６−４９１
【特許文献１】
国際公開ＷＯ０２／１３９９９号パンフレット
【特許文献２】
特開２００１−６４５４０号公報（第１頁）
【特許文献３】
特願２００１−２１０３９７号明細書（特許請求の範囲）
【０００６】
【発明が解決しようとする課題】
しかしながら、前記従来技術の二液性導電性塗料で平滑性の優れた塗膜を得るには、スピンコートにより塗装する以外になく、このため、大量生産に適さず、また、大きい基材や複雑な形状の基材への塗装が困難である。一方、スピンコートにより塗装する以外の方法、すなわち一般的に工業塗装に用いられるスプレー塗装、ローラーコート、ディップコート、フローコート、ナイフコート、静電塗装、バーコート、ダイコート、ハケ塗り等の塗工方法では、二液性導電性塗料の分散媒が、通常、水を主成分としており、特に硬化性成分を含まない第一液の表面張力が大きいので、塗装適性が悪く、均一な膜厚の塗膜が得られず、色むらが生じて商品価値が低下するばかりでなく、所望の透明性や導電性が発現しないという問題がある。
【０００７】
本発明は以上に述べた従来技術の問題点を解決し、平滑性が優れ、優れた透明性、導電性を有する塗膜を、工業的、経済的に有利に形成することのできる導電性塗料及びその導電性塗料を用いた塗膜の形成方法並びに導電性塗膜を有する基材の製造方法を提供するものである。
【０００８】
【課題を解決するための手段】
本発明者は鋭意研究を重ねた結果、前記組成の二液性導電性塗料において、第一液に有機増粘剤を配合すると、塗装適性が改良できることを見出し、更には得られた塗膜が、優れた平滑性、透明性を有し、優れた導電性を有することを見出し、本発明を完成した。
【０００９】
すなわち本発明は、導電性粒子と水を主成分とする分散媒と有機増粘剤とを含む第一液、硬化性成分を含む第二液からなることを特徴とする導電性塗料である。
【００１０】
【発明の実施の形態】
本発明は導電性塗料であって、導電性粒子と水を主成分とする分散媒と有機増粘剤とを含む第一液、硬化性成分を含む第二液からなり、第一液には実質的に硬化性成分が含まれず、この第一液を基材に塗布し、導電性粒子を含む層を形成させ、次いで、導電性粒子を含む層の上に、硬化性成分を含む第二液を塗布し、硬化性成分を硬化させて導電性塗膜を得るものである。本発明では、第一液に有機増粘剤を配合し、塗装適性を改良することで、スピンコートを用いなくても、スプレー塗装、ローラーコート、ディップコート、フローコート、ナイフコート、静電塗装、バーコート、ダイコート、ハケ塗り等の一般的な塗工方法によっても、均一な膜厚の塗膜が得られる。このため、得られた塗膜は、色むらがほとんど生じず、透明性や導電性が優れたものとなる。また、大量生産のライン塗装に適し、大きい基材や複雑な形状の基材への塗装を可能にする。
【００１１】
本発明では有機増粘剤として、導電性粒子を含む第一液の粘度を一般的な塗工方法を用いることができる程度に大きくし、レオロジーなどの塗装適性を改良できるものを用いる。例えば、有機増粘剤として高分子のものを用いると、所望の効果が得られ易いので好ましく、５００００〜５０００００の範囲の平均分子量を有していれば、更に好ましい。特に、内部作用型と呼ばれる高分子は、導電性粒子の表面への吸着や化学結合がほとんど生じないので、有機増粘剤自体は絶縁性であっても、導電性の優れた塗膜を得ることができるので、これを用いるのが好ましい。第一液に用いる分散媒が水を主成分としているので、有機増粘剤も水溶性であれば好ましいが、例えば、ステアリン酸のように非水溶性であっても、アルコール等の親水性有機溶剤により、水と相溶化させて用いたり、乳化剤を用いて水に乳化させる等して、用いることもできる。
【００１２】
有機増粘剤の配合量は、第一液１００重量部に対し、０．０５〜８重量部の範囲が好ましく、前記範囲未満では本発明の効果が得られ難く、前記範囲を超えると、著しく増粘し却って塗装適性を低下させ易く、また、後述の加熱によって分解され難くなる。より好ましい配合量は、０．１〜４重量部の範囲である。また、導電性粒子１重量部に対する有機増粘剤の配合量は、０．１〜２０重量部の範囲が好ましい。より好ましい範囲は導電性粒子の種類によって異なるが、金属コロイド粒子の場合、０．７〜２０重量部の範囲である。
【００１３】
本発明で有機増粘剤として用いることのできる内部作用型の水溶性高分子としては、例えば、ヒドロキシエチルセルロース、カルボキシメチルセルロース、メチルセルロース、エチルセルロース等のセルロース系、ポリビニルアルコール、ポリビニルピロリドン等のビニル系、ポリアクリル酸ソーダ、ポリアクリル酸アンモニウム等のアクリル酸系等の合成高分子、ゼラチン、カゼイン、カゼイン酸ソーダ、カゼイン酸アンモニウム等のタンパク質系や、デンプン、デキストリン、アラビアゴム、寒天、アルギン酸ソーダ等の天然高分子等が挙げられ、これらの１種または２種以上を用いることができる。中でも、セルロース系、ビニル系は効果が高いので好ましく、ヒドロキシエチルセルロース、ポリビニルアルコール、ポリビニルピロリドンであれば更に好ましい。
【００１４】
導電性粒子としては、金属コロイド粒子や導電性酸化物等の公知のものを１種、あるいは２種以上を組み合わせて用いることができ、導電性塗料を用いる目的に応じて適宜選択できる。例えば、特に高い導電性を要する電磁波遮蔽用には金属コロイド粒子を、帯電防止には導電性酸化物を用いるのが好ましい。
【００１５】
本発明で用いる金属コロイド粒子には特に制限はなく、２種以上の金属コロイド粒子を混合して用いても良い。また、金属コロイド粒子を構成する金属にも特に制限はなく、１種の金属で構成されても、２種以上の金属の合金で構成されても良い。金属コロイド粒子を構成する金属は、周期表ＶＩＩＩ族（鉄、コバルト、ニッケル、ルテニウム、ロジウム、パラジウム、オスミウム、イリジウム、白金）及びＩＢ族（銅、銀、金）からなる群から選ばれる少なくとも１種であれば、導電性が高いので好ましく、中でも金、銀、白金、パラジウム、銅は特に導電性が高くより好ましい。金属コロイド粒子の平均粒子径は、１〜１００ｎｍ程度の一般的なものを用いることができ、優れた透明性を有することから、５〜５０ｎｍの範囲の平均粒子径を有する金属コロイド粒子が好ましい。第一液に含まれる金属コロイド粒子の量は、目的に応じて適宜設定するが、例えば、前記の電磁波遮蔽用であれば、硬化性成分１重量部に対し、金属コロイド粒子が０．０５〜０．５重量部の範囲である。
【００１６】
金属コロイド粒子は、その表面に保護コロイドを有していることが好ましく、保護コロイドの作用により、水を主成分とする分散媒中に安定した状態で分散できる。保護コロイドは金属コロイド粒子１重量部に対し、０．０５〜１．５重量部の範囲で含まれていれば、所望の分散安定性が得られるので好ましい。
【００１７】
保護コロイドとしては公知の化合物を用いることができ、例えば、クエン酸及びその誘導体、アニリン及びその誘導体、メルカプト酢酸、メルカプトプロピオン酸、チオジプロピオン酸、メルカプトコハク酸、チオ酢酸等の酸チオール類、メチルメルカプタン、エチルメルカプタン、プロピルメルカプタン、イソプロピルメルカプタン、ｎ−ブチルメルカプタン、アリルメルカプタン、ジメチルメルカプタン、メルカプトエタノール、アミノエチルメルカプタン、チオジエチルアミン等の脂肪族チオール類、シクロヘキシルチオール等の脂環式チオール類、チオフェノール等の芳香族チオール類等のチオール類、チオジエチレングリコール、チオジグリコール酸、エチレンチオグリコール等のチオグリコール類、チオホルムアミド等のチオアミド類、ジチオール類、チオン類、ポリチオール類、チオ炭酸類、チオ尿素類、硫化水素等のイオウ化合物及びそれらの誘導体等が挙げられ、これらを１種または２種以上を用いても良い。本発明では、保護コロイドとしてクエン酸、チオール類及びそれらの誘導体からなる群から選ばれる少なくとも１種が好ましい。
【００１８】
金属コロイド粒子は微粒子であり、表面エネルギーが非常に大きく、均一に分散させることが困難であるので、第一液を調製するには、予め金属コロイド粒子を分散媒に分散させた所謂金属コロイド溶液を用い、この金属コロイド溶液に分散媒等や各種の添加剤を加えることが好ましい。金属コロイド溶液の調製には、公知の方法を用いることができる。例えば、前記の非特許文献１に開示される、金属塩の水溶液に、保護コロイドとしてクエン酸またはその塩を加え、第一鉄イオン等の還元剤を添加した後、脱塩、濃縮する方法を用いても良い。あるいは、前記の特許文献１に記載される、保護コロイドとしての低分子量の硫黄化合物の存在下、分散媒中で金属塩を還元して、前記硫黄化合物を表面に有する金属コロイド粒子を生成させ、分散媒のｐＨを５以下にし、前記金属コロイド粒子を凝集させ濾別した後、濾別した金属コロイド粒子を、ｐＨを８〜１４の分散媒中に再度分散させる方法を用いても良い。
【００１９】
本発明で用いる導電性酸化物としては、公知のものを用いることができ、例えば酸化スズ、酸化インジウム、酸化亜鉛等が挙げられ、これらの１種または２種以上を用いることができる。導電性酸化物の表面には、分散性向上等の目的で、ケイ素、タングステン、ジルコニウム、アルミニウム等の酸化物または水和酸化物を、導電性酸化物の表面に被覆しても良い。第一液に含まれる導電性酸化物の量は、目的に応じて適宜設定するが、例えば、前記の帯電防止用であれば、第一液に０．５〜５０重量％の範囲で含まれているのが好ましく、０．５〜２０重量％の範囲がより好ましい。
【００２０】
導電性酸化物としては、例えば、酸化スズ、酸化インジウム、酸化亜鉛等の公知のものを用いることができる。前記の導電性酸化物の結晶中に、アンチモン、リン、フッ素、タングステン、タンタル、ガリウム、スズ、インジウム、アルミニウム等の異種元素を１種または２種以上ドープすると、導電性が更に高くなるので、これらを用いるのが好ましい。中でも酸化スズとアンチモン、リン、フッ素、タングステンまたはタンタル、酸化インジウムとスズ、及び、酸化亜鉛とフッ素、アルミニウム、ガリウム、インジウムまたはスズとの組み合わせが特に好ましい。これらの導電性酸化物または異種元素をドープした導電性酸化物は、１種で用いても良く、あるいは２種以上を組み合わせて用いることもできる。異種の元素のドープ量は、導電性酸化物の種類や用いる元素との組み合わせにもよるが、例えば、アンチモンをドープした酸化スズであれば、アンチモンがＳｂ２Ｏ３として０．５〜２０重量％の範囲で含まれるのが好ましく、より好ましくは８〜１５重量％の範囲であり、リンをドープした酸化スズであれば、リンがＰ２Ｏ５として０．３〜１５重量％の範囲で含まれるのが好ましく、より好ましくは０．５〜５重量％の範囲である。
【００２１】
導電性酸化物粒子の形状は、球状形状のほか、針状、棒状、紡錘状、樹枝状、板状等の異方性形状、粒塊状等の不定形形状等、特に制限はない。導電性酸化物の粒子径は、粒子形状によって異なるが、例えば、球状粒子であれば、平均粒子径が０．００５〜０．１μｍの範囲が好ましく、更に好ましくは０．０１〜０．０３μｍの範囲であり、針状粒子であれば、平均短軸径が０．００５〜０．１μｍ、平均長軸径が０．１〜１０μｍの範囲が好ましく、平均短軸径が０．０１〜０．０２μｍ、平均長軸径が０．２〜２μｍの範囲が更に好ましい。導電性酸化物粒子の比表面積は、２０〜３００ｍ２／ｇの範囲であれば、透明性が優れ、また表面エネルギーが大き過ぎず、分散が比較的容易であるので、これを用いるのが好ましく、比表面積が３０〜１３０ｍ２／ｇの範囲のものを用いるのが、更に好ましい。尚、比表面積はＢＥＴ法で測定したもので、粒子径はいずれも電子顕微鏡法による、５０％粒子径である。
【００２２】
導電性酸化物の調製には、公知の方法を適用でき、例えば、（１）導電性酸化物の金属種を含む化合物の中和生成物を、加熱焼成する方法、（２）前記金属種の塩化物の加水分解生成物を、加熱焼成する方法、等の方法が挙げられる。前記のケイ素、アルミニウム等の酸化物または水和酸化物を、表面に被覆する場合は、例えば、（１）や（２）の方法で得られた導電性酸化物をスラリー化し、被覆種の化合物を添加し中和すれば良い。異種の元素を粒子内部に含ませる場合は、例えば、（１）の方法においては、中和する際に、異種元素の化合物を加えて共沈させたり、（２）の方法においては、異種元素の塩化物を加え、共に加水分解しても良い。加熱焼成または表面被覆した後は、気流式粉砕機、衝撃式粉砕機、摩砕機等の粉砕機により、適宜粉砕する。
【００２３】
本発明における水を主成分とする分散媒とは、水を５０重量％以上、好ましくは８０重量％以上含む分散媒であり、水以外の成分としては、アルコール類、ケトン類等の親水性有機溶媒が、本発明の効果を損なわない範囲で含まれていても良い。
【００２４】
第一液には導電性粒子の分散安定性を高める目的で、更に有機分散剤が含まれていても良い。有機分散剤の配合量は、導電性粒子の種類によって異なるので、塗料組成に応じて適宜設定するが、一般的には導電性粒子１重量部に対し、０．０１〜０．５重量部の範囲が好ましい。有機分散剤は第４級アンモニウム塩等のカチオン系、カルボン酸塩、スルホン酸塩、硫酸エステル塩、リン酸エステル塩等のアニオン系、エーテル型、エーテルエステル型、エステル型、含窒素型等のノニオン系等の公知のものを用いることができる。
【００２５】
第一液は、導電性粒子を、水を主成分とする分散媒に、導電性粒子を予め分散させた分散体に、必要に応じて更に前記分散媒を添加して濃度調整し、有機増粘剤を添加したり、あるいは、有機増粘剤を予め添加した水を主成分とする分散媒に導電性粒子を分散させて得られる。導電性粒子として金属コロイド粒子を用いる場合には、前述のように、通常、金属コロイド溶液と呼ばれる分散体として提供されるので、これを用いることができる。
【００２６】
導電性酸化物を用いる場合には、等電点が酸性にあるものはアルカリ性の水に、等電点がアルカリ性にあるものは酸性の水に、分散安定化する性質を有しているので、導電性酸化物の等電点に応じて前記分散媒のｐＨを調整することで、分散させることができる。導電性酸化物の分散には、必要に応じてサンドミル、ラインミル、コロイドミル等の分散機を用いても良い。ｐＨ調整に用いる塩基性化合物としては、例えば水酸化ナトリウム、水酸化カリウム、水酸化カルシウム等のアルカリ金属またはアルカリ土類金属の水酸化物、アンモニア等のアンモニウム化合物、アミン類等が、酸性化合物としては例えば塩酸、硫酸、硝酸等の無機酸やギ酸、酢酸、プロピオン酸等の有機酸が挙げられる。充填剤、種々の添加剤、着色剤等は、導電性粒子の分散体、分散媒または調製した第一液などに適宜添加して配合することができる。
【００２７】
第二液に配合する硬化性成分としては、アルキルシリケート、アルキルチタネート等の無機系のものや、アクリル、アルキド、ポリエステル、ウレタン、エポキシ等の有機系のものを用いることができ、熱硬化性、常温硬化性、紫外線硬化性等いずれでも良い。紫外線硬化性成分を用いる際には、ベンゾイン系、アセトフェノン系、チオキサンソン系、パーオキシド系等の重合開始剤、アミン系、キノン系等の重合開始促進剤、熱重合禁止剤等を必要に応じて加えても良い。硬化性成分の配合量は、目的とする導電性塗膜の膜厚等に応じて、適宜設定することができる。第二液には、前記の硬化性成分や重合開始剤等以外に、通常、硬化性成分を溶解する溶剤が含まれる。
【００２８】
第一液及び第二液には、前記成分以外に、導電性や透明性を阻害しない範囲で、コロイダルシリカ、微粒子酸化チタン等の充填剤、種々の添加剤、着色剤が含まれていても良い。
【００２９】
次に、本発明は導電性塗膜の形成方法並びに導電性塗膜を有する基材の製造方法であって、本発明の導電性塗料の第一液を基材表面に塗布し、導電性粒子を含む層を形成させ、次いで、導電性粒子を含む層の上に、前記塗料の第二液を塗布した後、硬化性成分を硬化させるものである。本発明の方法では、均一な膜厚で平滑性の優れた塗膜を形成でき、且つ、導電経路が形成され易く、導電性と透明性が優れた塗膜が得られる。
【００３０】
本発明では第一液及び第二液を、従来の二液性導電性塗料のようにスピンコートで塗布する必要がなく、スプレー塗装、ローラーコート、ディップコート、フローコート、ナイフコート、静電塗装、バーコート、ダイコート、ハケ塗り等、汎用の塗工機を用いた塗工方法を適用できるので、導電性塗膜が工業的、経済的に有利に得られる。例えば、バーコーターで塗装した場合でも、金属コロイド粒子を用いた塗膜では、表面抵抗が１×１０４Ω／□以下、導電性酸化物を用いた塗膜では、表面抵抗が１×１０７Ω／□以下となり、透過率はいずれも６０％以上となる。第一液及び第二液の塗布膜厚には特に制限はないが、作業性やレべリング性を考慮すると、いずれも０．０１〜１０μｍの範囲とするのが好ましい。第二液を塗布する際には、塗工方法に応じ、適宜希釈して粘度を調整しても良い。
【００３１】
硬化性成分の硬化中または硬化後の少なくともどちらか一方で、塗膜を加熱すると、絶縁性の有機増粘剤が分解されるため、導電性がより阻害され難くなるので、好ましい方法である。加熱温度は用いる有機増粘剤の種類にもよるが、通常、１２０〜４５０℃の範囲で有機増粘剤は分解するので、前記範囲が好ましい。加熱には電気炉、ガス炉等、公知の機器を用いることができる。
【００３２】
硬化性成分を硬化させるには、硬化性成分の種類に応じ、加熱、常温静置、紫外線照射等の手段を用いる。加熱硬化は、耐熱性に優れたガラス、セラミックス等の無機系材料からなる基材に特に適しており、常温硬化、紫外線硬化は、耐熱性の低いプラスチックス等の有機系材料からなる基材に特に適している。硬化性成分として熱硬化性のものを用いると、加熱により硬化性成分の硬化と、前記の有機増粘剤の分解を、同時に行うことができるので好ましい。
【００３３】
本発明は前記のように種々の基材に適用できるので、これらの基材、特に透明性基材を用いた組成物の帯電防止や電磁波遮蔽に有用である。そのような組成物として、例えば、ブラウン管、液晶ディスプレイ等の表示機器、クリーンルームの窓材、電子部品包装材、オーバーヘッドディスプレイや写真等に用いられるフィルム、太陽電池、タッチパネルや液晶等に用いられる透明電極材料等が挙げられる。
【００３４】
【実施例】
以下に実施例を挙げて本発明を更に詳細に説明するが、本発明はこれらの実施例によって制限されるものではない。
【００３５】
金属コロイド溶液の調製（１）
クエン酸三ナトリウム水和物２００ｇ／リットル、硫酸鉄（ＩＩ）１００ｇ／リットルの濃度の水溶液１０００ミリリットルを撹拌しながら、９０ｇ／リットルの濃度の硝酸銀水溶液４００ミリリットルを、室温下で急速に添加することにより還元反応を行い、クエン酸三ナトリウムを表面に有する銀コロイド粒子を溶液中で生成させた。この溶液を限外濾過により、濾液の電気伝導度が１０μＳ／ｃｍ以下になるまで水洗した後、濃縮された溶液を、純水で固形分が５％になるように濃度を調整して銀コロイド溶液（試料ａ）を得た。
【００３６】
金属コロイド溶液の調製（２）
硝酸銀水溶液を塩化パラジウムとして４７．５ｇ／リットルの濃度の、塩化ナトリウムとして４０ｇ／リットルの濃度の水溶液に替えた以外は、試料ａと同様に濾過・水洗、濃度調整してパラジウムコロイド溶液（試料ｂ）を得た。
【００３７】
金属コロイド溶液の調製（３）
５０ミリモルの硝酸銀水溶液１０００ミリリットルを撹拌しながら、メルカプト酢酸３ｇを添加した後、アンモニア水（２６％）にて水溶液のｐＨを１０に調整した。この水溶液に４０ミリモルの水素化ホウ素ナトリウム水溶液５０ミリリットルを、室温下で急速に添加することにより還元反応を行い、メルカプト酢酸を表面に有する銀コロイド粒子を溶液中に生成させた。この溶液を硝酸（２０％）を用いてｐＨを３に調整し、銀コロイド粒子を沈降させた後、真空濾過により濾液の電気伝導度が１０μＳ／ｃｍ以下になるまで水洗した後、濾別して銀コロイド粒子の湿ケーキを得た。銀コロイド粒子の湿ケーキを、固形分が１０％になるように純水に添加し、撹拌しながらアンモニア水（２６％）にてｐＨを９に調整して再分散させ、銀コロイド溶液（試料ｃ）を得た。
【００３８】
金属コロイド溶液の調製（４）
２５ミリモルの塩化金酸水溶液１０００ミリリットルを撹拌しながら、３−メルカプトプロピオン酸１．５ｇを添加した後、アンモニア水（２６％）にて水溶液のｐＨを１０に調整した。この水溶液に１２０ミリモルのヒドラジン水溶液５０ミリリットルを、室温下で急速に添加することにより還元反応を行い、表面に３−メルカプト酢酸を有する金コロイド粒子を溶液中に生成させた。この溶液を塩酸（２０％）を用いてｐＨを３に調整し、金コロイド粒子を沈降させた後、試料ｃと同様に、濾過・洗浄、再分散させて金コロイド溶液（試料ｄ）を得た。
【００３９】
導電性酸化物の水分散体
球状アンチモン含有導電性酸化スズ（比表面積７０ｍ２／ｇ、平均粒子径０．０２μｍ）の水分散体ＳＮ−１００Ｄ（石原産業製、固形分濃度３０重量％）を、試料ｅとする。
【００４０】
実施例１〜５及び比較例１〜５
導電性塗料の調製
試料ａ〜ｅを用い、以下の処方１、２に従って塗料化し、本発明の導電性塗料（試料Ａ〜Ｅ）及び比較例の導電性塗料（試料Ｆ〜Ｊ）を得た。
【００４１】
（処方２）
＊第一液
試料ａ〜ｅ ８．０ ｇ
純水 ２０．０５ｇ
エチレングリコールモノブチルエーテル ５．０ ｇ
アセトアミド ６．０ ｇ
ＢＹＫ−１９０（有機分散剤：ビックケミー社製、有効成分４０％）０．０５ｇ
＊第二液
メチルシリケート５１
（無機硬化性成分：コルコート社製、固形分５１％） ４．６ ｇ
エタノール ９．０ ｇ
２−プロパノール ４６．８ ｇ
１−メトキシ−２−プロパノール １７３．０ ｇ
純水 １．０ ｇ
２０％塩酸 ０．０３ｇ
【００４３】
導電性塗膜の形成
一片７５ｍｍ、厚さ３ｍｍの正方形のガラス基板上に、試料Ａ〜Ｊの導電性塗料の第一液を＃１０バーコーターにて塗布し、１０分間風乾し、次いで、第二液を＃１０バーコーターにて塗布し、１０分間風乾した後、１５０℃で３０分間加熱して導電性塗膜を得た。
【００４４】
評価：表面抵抗、ヘーズ、透過率の測定、色むらの評価
得られた塗膜の表面抵抗を、表面抵抗計（ロレスタＧＰ型、三菱化学社製）を用い、ヘーズ及び透過率をヘーズメーター（ＤＨ−３００Ａ型、日本電色工業製）を用いて計測した。また塗膜の色むらを、目視判定により評価した。
【００４５】
結果を表１に示す。本発明の二液性導電性塗料は、従来の二液性導電性塗料と比較して、バーコーターで塗布しても導電性が高く、透明性に優れ、且つ、色むらのない塗膜が得られることが判る。
【００４６】
【表１】
【発明の効果】
本発明は、導電性粒子と水を主成分とする分散媒と有機増粘剤とを含む第一液、硬化性成分を含む第二液からなる二液性導電性塗料であって、第一液には実質的に硬化性成分が含まれず、この第一液を基材に塗布し、導電性粒子を含む層を形成させ、次いで、導電性粒子を含む層の上に、硬化性成分を含む第二液を塗布し、硬化性成分を硬化させて導電性塗膜を得るものであり、各種基材の帯電防止や電磁波遮蔽などの付与に有用である。
【００４８】
本発明では、第一液に有機増粘剤を配合し、塗装適性を改良することで、スピンコートを用いなくても、スプレー塗装、ローラーコート、ディップコート、フローコート、ナイフコート、静電塗装、バーコート、ダイコート、ハケ塗り等の一般的な塗工方法によっても、膜厚が均一で色むらがほとんど生じない導電性塗膜が工業的、経済的に有利に得られる。特に、本発明は大量生産のライン塗装に適し、大きい基材や複雑な形状の基材への塗装ができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a conductive paint, a method for forming a conductive coating film using the same, and a method for producing a substrate having a conductive coating film, and more particularly to a conductive paint having excellent coating suitability and high conductivity and transparency.
[0002]
[Prior art]
Used for display surfaces of display devices such as cathode ray tubes (CRTs) and liquid crystal displays (LCDs), window materials for clean rooms and the like, glass and plastics used as packaging materials for IC packages and the like, or overhead displays (OHPs) and photographs. Various transparent base materials such as a film to be obtained are generally insulators and are easily charged with static electricity. For this reason, dust and dust easily adhere to the surface, not only deteriorating the aesthetic appearance, but also causing problems such as reduced visibility, occurrence of defective products due to mixing with the product, and malfunction of electronic devices. In particular, in the case of an electronic device, static electricity itself also caused a malfunction or the like. In recent years, the influence of electromagnetic waves generated from the screen of a personal computer or a television on the human body has become a problem.
[0003]
Therefore, it is common practice to apply a conductive paint containing conductive particles to the surface of the base material in order to prevent static electricity and shield electromagnetic waves. Examples of the conductive particles include metal particles called metal colloid particles having an average particle diameter of about 1 to 100 nm (for example, see Non-Patent Document 1 and Patent Document 1) and a specific surface area of 20 to 150 m. 2 / G of conductive oxide particles such as tin oxide, indium oxide, and zinc oxide. Metal colloid particles and conductive oxide fine particles have the property of transmitting visible light and are suitable for the above-mentioned transparent base material. Among them, metal colloid particles have extremely high conductivity, and are particularly used for electromagnetic wave shielding. In addition, since the conductive oxide fine particles are inexpensive, they are generally used for antistatic.
[0004]
In a conductive paint using such conductive particles, the first liquid contains the conductive particles and the dispersion medium, is substantially free of a curable component, and is a two-pack paint containing a curable component in the second liquid. And those using metal colloid particles as conductive particles (for example, see Patent Document 2) and those using conductive oxide (for example, see Patent Document 3). This is to apply a first liquid to a substrate, form a layer containing conductive particles, and then apply a second liquid to cure a curable component to obtain a conductive coating film. An insulating curable component hardly intervenes at a contact point between the conductive particles and the base material, and a conductive path is easily formed, so that the conductive particles can exhibit excellent conductivity.
[0005]
[Non-patent document 1]
M Carey Lea, "American Journal of Science", 1889, Vol. 37, P476-491.
[Patent Document 1]
International Publication WO02 / 13999 pamphlet
[Patent Document 2]
JP 2001-64540 A (page 1)
[Patent Document 3]
Japanese Patent Application No. 2001-210397 (Claims)
[0006]
[Problems to be solved by the invention]
However, in order to obtain a coating film having excellent smoothness with the two-component conductive paint of the prior art, there is no other than coating by spin coating, and therefore, it is not suitable for mass production, and is not suitable for large substrates or complicated substrates. It is difficult to coat substrates with various shapes. On the other hand, a method other than spin coating, that is, coating such as spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating, bar coating, die coating, brush coating, etc. which are generally used for industrial coating. In the method, the dispersion medium of the two-component conductive paint is usually mainly composed of water, and particularly the surface tension of the first liquid containing no curable component is large. There is a problem that not only a coating film is not obtained, color unevenness occurs and commercial value is reduced, but also desired transparency and conductivity are not exhibited.
[0007]
The present invention solves the above-mentioned problems of the prior art, and has excellent smoothness, excellent transparency, and a conductive paint capable of forming an industrially and economically advantageous coating film having conductivity. And a method for forming a coating film using the conductive coating and a method for producing a substrate having the conductive coating.
[0008]
[Means for Solving the Problems]
The present inventor has conducted extensive studies and found that, in a two-component conductive paint having the above composition, when an organic thickener was added to the first liquid, the coating suitability could be improved. The present invention was found to have excellent smoothness and transparency, and excellent conductivity.
[0009]
That is, the present invention is a conductive paint comprising a first liquid containing conductive particles, a dispersion medium containing water as a main component, and an organic thickener, and a second liquid containing a curable component.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is a conductive paint, a first liquid containing a dispersion medium containing conductive particles and water as a main component and an organic thickener, a second liquid containing a curable component, the first liquid Substantially free of curable components, the first liquid is applied to a substrate to form a layer containing conductive particles, and then a second layer containing curable components is formed on the layer containing conductive particles. The liquid is applied and the curable component is cured to obtain a conductive coating film. In the present invention, by adding an organic thickener to the first liquid and improving coating suitability, spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating can be performed without using spin coating. A coating film having a uniform thickness can also be obtained by a general coating method such as bar coating, die coating, brush coating, and the like. For this reason, the obtained coating film has almost no color unevenness, and has excellent transparency and conductivity. In addition, it is suitable for mass production line coating, and enables coating on large substrates and substrates with complicated shapes.
[0011]
In the present invention, as the organic thickener, one that increases the viscosity of the first liquid containing the conductive particles to such an extent that a general coating method can be used and can improve coating suitability such as rheology is used. For example, it is preferable to use a polymer as the organic thickener because a desired effect is easily obtained, and it is more preferable that the organic thickener has an average molecular weight in the range of 50,000 to 500,000. In particular, a polymer called an internally acting type hardly causes adsorption or chemical bonding to the surface of the conductive particles, so that even if the organic thickener itself is insulative, a highly conductive coating film is obtained. It is preferable to use this. Since the dispersion medium used for the first liquid is mainly composed of water, it is preferable that the organic thickener is also water-soluble. For example, even if the organic thickener is insoluble in water such as stearic acid, a hydrophilic organic compound such as alcohol is used. It can also be used after being made compatible with water with a solvent or emulsified in water using an emulsifier.
[0012]
The compounding amount of the organic thickener is preferably in the range of 0.05 to 8 parts by weight, based on 100 parts by weight of the first liquid. It is easy to increase the viscosity and lower the coating suitability, and it is difficult to be decomposed by heating described later. A more preferred amount is in the range of 0.1 to 4 parts by weight. The compounding amount of the organic thickener per 1 part by weight of the conductive particles is preferably in the range of 0.1 to 20 parts by weight. The more preferable range depends on the type of the conductive particles, but in the case of metal colloid particles, the range is 0.7 to 20 parts by weight.
[0013]
Examples of the internal-acting water-soluble polymer that can be used as the organic thickener in the present invention include, for example, celluloses such as hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose; polyvinyl alcohols; Synthetic polymers such as acrylic acid such as sodium acrylate and ammonium polyacrylate; protein systems such as gelatin, casein, sodium caseinate and ammonium caseinate; and natural materials such as starch, dextrin, gum arabic, agar and sodium alginate Polymers and the like can be mentioned, and one or more of these can be used. Among them, cellulose-based and vinyl-based are preferred because they are highly effective, and hydroxyethyl cellulose, polyvinyl alcohol, and polyvinylpyrrolidone are more preferred.
[0014]
As the conductive particles, known ones such as metal colloid particles and conductive oxides can be used alone or in combination of two or more, and can be appropriately selected according to the purpose of using the conductive paint. For example, it is preferable to use metal colloid particles for shielding electromagnetic waves requiring particularly high conductivity, and to use a conductive oxide for antistatic.
[0015]
The metal colloid particles used in the present invention are not particularly limited, and two or more kinds of metal colloid particles may be mixed and used. The metal constituting the metal colloid particles is not particularly limited, and may be made of one kind of metal or an alloy of two or more kinds of metals. The metal constituting the metal colloid particles is at least one selected from the group consisting of group VIII of the periodic table (iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum) and group IB (copper, silver, gold). A species is preferred because of its high conductivity, and among them, gold, silver, platinum, palladium and copper are particularly preferred because of their high conductivity. The average particle diameter of the metal colloid particles may be a general one of about 1 to 100 nm, and metal colloid particles having an average particle diameter in the range of 5 to 50 nm are preferable because of excellent transparency. The amount of the metal colloid particles contained in the first liquid is appropriately set depending on the purpose. For example, in the case of the above-mentioned electromagnetic wave shielding, the metal colloid particles are contained in an amount of 0.05 to 1 part by weight of the curable component. The range is 0.5 parts by weight.
[0016]
The metal colloid particles preferably have a protective colloid on the surface, and can be stably dispersed in a dispersion medium containing water as a main component by the action of the protective colloid. It is preferable that the protective colloid is contained in the range of 0.05 to 1.5 parts by weight based on 1 part by weight of the metal colloid particles, since desired dispersion stability can be obtained.
[0017]
Known compounds can be used as the protective colloid, for example, acid thiols such as citric acid and derivatives thereof, aniline and derivatives thereof, mercaptoacetic acid, mercaptopropionic acid, thiodipropionic acid, mercaptosuccinic acid, and thioacetic acid; Methyl mercaptan, ethyl mercaptan, propyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, allyl mercaptan, dimethyl mercaptan, mercaptoethanol, aminoethyl mercaptan, aliphatic thiols such as thiodiethylamine, alicyclic thiols such as cyclohexyl thiol, thiol Thiols such as aromatic thiols such as phenol; thioglycols such as thiodiethylene glycol, thiodiglycolic acid and ethylene thioglycol; and thiols such as thioformamide. Earth, dithiols, thiones, polythiols, thiocarbonates, thioureas, include sulfur compounds and their derivatives etc., such as hydrogen sulfide, it may be used alone or in combination. In the present invention, as the protective colloid, at least one selected from the group consisting of citric acid, thiols and their derivatives is preferable.
[0018]
Since the metal colloid particles are fine particles, the surface energy is very large, and it is difficult to uniformly disperse the metal colloid particles. To prepare the first liquid, a so-called metal colloid solution in which the metal colloid particles are previously dispersed in a dispersion medium is used. It is preferable to add a dispersion medium and various additives to this metal colloid solution by using the following. Known methods can be used for preparing the metal colloid solution. For example, a method disclosed in Non-Patent Document 1 described above is a method of adding citric acid or a salt thereof as a protective colloid to an aqueous solution of a metal salt, adding a reducing agent such as ferrous ion, and then desalting and concentrating. May be used. Alternatively, a metal salt is reduced in a dispersion medium in the presence of a low-molecular-weight sulfur compound as a protective colloid described in Patent Document 1 to generate metal colloid particles having the sulfur compound on the surface, A method may be used in which the pH of the dispersion medium is adjusted to 5 or less, the metal colloid particles are aggregated and filtered, and then the filtered metal colloid particles are dispersed again in a dispersion medium having a pH of 8 to 14.
[0019]
As the conductive oxide used in the present invention, known oxides can be used, and examples thereof include tin oxide, indium oxide, and zinc oxide. One or more of these can be used. The surface of the conductive oxide may be coated with an oxide or a hydrated oxide such as silicon, tungsten, zirconium, or aluminum for the purpose of improving dispersibility or the like. The amount of the conductive oxide contained in the first liquid is appropriately set according to the purpose. For example, in the case of the above-described antistatic purpose, the amount contained in the first liquid is 0.5 to 50% by weight. And more preferably in the range of 0.5 to 20% by weight.
[0020]
As the conductive oxide, for example, known oxides such as tin oxide, indium oxide, and zinc oxide can be used. In the crystals of the conductive oxide, antimony, phosphorus, fluorine, tungsten, tantalum, gallium, tin, indium, doping with one or more different elements such as aluminum, the conductivity is further increased, It is preferable to use these. Among them, a combination of tin oxide and antimony, phosphorus, fluorine, tungsten or tantalum, a combination of indium oxide and tin, and a combination of zinc oxide and fluorine, aluminum, gallium, indium or tin are particularly preferable. These conductive oxides or conductive oxides doped with different elements may be used alone or in combination of two or more. The doping amount of the different element depends on the type of the conductive oxide and the combination with the element to be used. For example, in the case of tin oxide doped with antimony, antimony is made of Sb. 2 O 3 Is preferably in the range of 0.5 to 20% by weight, more preferably in the range of 8 to 15% by weight. 2 O 5 Is preferably in the range of 0.3 to 15% by weight, more preferably in the range of 0.5 to 5% by weight.
[0021]
The shape of the conductive oxide particles is not particularly limited, such as a spherical shape, an anisotropic shape such as a needle shape, a rod shape, a spindle shape, a dendritic shape, and a plate shape, and an irregular shape such as a granular mass. The particle diameter of the conductive oxide varies depending on the particle shape. For example, in the case of spherical particles, the average particle diameter is preferably in the range of 0.005 to 0.1 μm, more preferably 0.01 to 0.03 μm In the case of acicular particles, the average minor axis diameter is preferably in the range of 0.005 to 0.1 μm, the average major axis diameter is preferably in the range of 0.1 to 10 μm, and the average minor axis diameter is preferably in the range of 0.01 to 0.1 μm. More preferably, the average major axis diameter is in the range of 0.2 to 2 μm. The specific surface area of the conductive oxide particles is 20 to 300 m 2 / G is preferable because it is excellent in transparency, the surface energy is not too large, and the dispersion is relatively easy. Therefore, the specific surface area is 30 to 130 m. 2 / G is more preferably used. The specific surface area was measured by the BET method, and the particle diameter was 50% particle diameter by electron microscopy.
[0022]
Known methods can be applied to the preparation of the conductive oxide. For example, (1) a method in which a neutralized product of a compound containing a metal species of the conductive oxide is heated and calcined; A method of heating and baking the hydrolysis product of chloride, and the like. When the surface is coated with the above oxides or hydrated oxides of silicon, aluminum, etc., for example, the conductive oxide obtained by the method (1) or (2) is slurried and the compound of the coating species is slurried. May be added for neutralization. When different kinds of elements are contained inside the particles, for example, in the method (1), when neutralizing, a compound of a different kind of element is added to coprecipitate, or in the method (2), different kinds of elements are added. May be added and hydrolyzed together. After heating and sintering or surface coating, pulverization is appropriately performed by a pulverizer such as an air-flow type pulverizer, an impact type pulverizer, or a triturator.
[0023]
In the present invention, the dispersion medium containing water as a main component is a dispersion medium containing 50% by weight or more, preferably 80% by weight or more of water, and the components other than water include hydrophilic organic compounds such as alcohols and ketones. A solvent may be contained within a range that does not impair the effects of the present invention.
[0024]
The first liquid may further contain an organic dispersant for the purpose of enhancing the dispersion stability of the conductive particles. Since the amount of the organic dispersant varies depending on the type of the conductive particles, the amount is appropriately set according to the coating composition. A range is preferred. Organic dispersants include cations such as quaternary ammonium salts, anions such as carboxylate, sulfonate, sulfate and phosphate, ether-type, ether-ester-type, ester-type and nitrogen-containing-type. Known materials such as nonionics can be used.
[0025]
In the first liquid, the concentration of the conductive particles is adjusted by adding a dispersion medium, if necessary, to a dispersion in which the conductive particles are previously dispersed in a dispersion medium containing water as a main component. It is obtained by adding a thickener or dispersing conductive particles in a dispersion medium containing water as a main component to which an organic thickener is added in advance. When metal colloid particles are used as the conductive particles, they are usually provided as a dispersion called a metal colloid solution, as described above, and can be used.
[0026]
When a conductive oxide is used, those having an acidic isoelectric point in alkaline water, those having an alkaline isoelectric point in acidic water, and having a property of stabilizing dispersion, Dispersion can be achieved by adjusting the pH of the dispersion medium according to the isoelectric point of the conductive oxide. For dispersing the conductive oxide, a disperser such as a sand mill, a line mill, or a colloid mill may be used as necessary. Examples of the basic compound used for pH adjustment include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, and calcium hydroxide, ammonium compounds such as ammonia, amines, and the like, as acidic compounds. Examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as formic acid, acetic acid, and propionic acid. Fillers, various additives, coloring agents, and the like can be appropriately added and blended with the dispersion or dispersion medium of the conductive particles or the prepared first liquid.
[0027]
As the curable component to be blended in the second liquid, an inorganic one such as alkyl silicate or alkyl titanate, or an organic one such as acrylic, alkyd, polyester, urethane, or epoxy can be used. Any of room temperature curability, ultraviolet curability, etc. may be used. When using an ultraviolet curable component, a benzoin-based, acetophenone-based, thioxanthone-based, peroxide-based polymerization initiator, an amine-based, quinone-based polymerization initiation accelerator, a thermal polymerization inhibitor, etc. are added as necessary. May be. The compounding amount of the curable component can be appropriately set according to the intended thickness of the conductive coating film and the like. The second liquid generally contains a solvent that dissolves the curable component, in addition to the curable component and the polymerization initiator.
[0028]
In the first liquid and the second liquid, in addition to the above components, a filler such as colloidal silica, fine particle titanium oxide, various additives, and a coloring agent as long as the conductivity and transparency are not impaired. good.
[0029]
Next, the present invention relates to a method for forming a conductive coating film and a method for producing a substrate having a conductive coating film, wherein a first liquid of the conductive paint of the present invention is applied to the surface of a substrate, and the conductive particles Is formed, and then the curable component is cured after the second liquid of the paint is applied on the layer containing the conductive particles. According to the method of the present invention, a coating film having a uniform thickness and excellent smoothness can be formed, and a conductive path is easily formed, and a coating film having excellent conductivity and transparency can be obtained.
[0030]
In the present invention, there is no need to apply the first liquid and the second liquid by spin coating as in the conventional two-component conductive paint, and spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating Since a coating method using a general-purpose coating machine such as bar coating, die coating and brush coating can be applied, a conductive coating film can be obtained industrially and economically advantageously. For example, even when coated with a bar coater, a coating using metal colloid particles has a surface resistance of 1 × 10 4 Ω / □ or less, a coating using a conductive oxide has a surface resistance of 1 × 10 7 Ω / □ or less, and the transmittance is 60% or more in each case. The coating thickness of the first liquid and the second liquid is not particularly limited, but is preferably in the range of 0.01 to 10 μm in consideration of workability and leveling property. When applying the second liquid, the viscosity may be adjusted by appropriately diluting according to the coating method.
[0031]
When the coating film is heated at least during or after the curing of the curable component, the insulating organic thickener is decomposed, so that the conductivity is less likely to be hindered. Although the heating temperature depends on the type of the organic thickener used, the above range is preferable because the organic thickener is usually decomposed in the range of 120 to 450 ° C. Known equipment such as an electric furnace and a gas furnace can be used for heating.
[0032]
In order to cure the curable component, means such as heating, standing at room temperature, and ultraviolet irradiation are used according to the type of the curable component. Heat curing is particularly suitable for substrates made of inorganic materials such as glass and ceramics having excellent heat resistance. Room temperature curing and ultraviolet curing are particularly suitable for substrates made of organic materials such as plastics having low heat resistance. Especially suitable. It is preferable to use a thermosetting material as the curable component, since the curing of the curable component and the decomposition of the organic thickener can be simultaneously performed by heating.
[0033]
Since the present invention can be applied to various substrates as described above, it is useful for antistatic and electromagnetic wave shielding of a composition using these substrates, particularly a transparent substrate. As such a composition, for example, a display device such as a cathode ray tube, a liquid crystal display, a window material of a clean room, an electronic component packaging material, a film used for an overhead display or a photograph, a solar cell, a transparent electrode used for a touch panel, a liquid crystal, and the like. Materials and the like.
[0034]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
[0035]
Preparation of metal colloid solution (1)
While stirring an aqueous solution of trisodium citrate 200 g / l and an aqueous solution of iron (II) sulfate at a concentration of 100 g / l, rapidly add 400 ml of an aqueous solution of silver nitrate at a concentration of 90 g / l at room temperature. To produce silver colloid particles having trisodium citrate on the surface in the solution. The solution is washed with ultrafiltration until the filtrate has an electric conductivity of 10 μS / cm or less, and then the concentrated solution is adjusted with pure water to a concentration of 5% so as to have a solid content of 5%. A solution (sample a) was obtained.
[0036]
Preparation of metal colloid solution (2)
Except that the aqueous silver nitrate solution was replaced with an aqueous solution having a concentration of 47.5 g / l as palladium chloride and a concentration of 40 g / l as sodium chloride, filtration and washing with water and concentration adjustment were performed in the same manner as in sample a, and a palladium colloid solution (sample b ) Got.
[0037]
Preparation of metal colloid solution (3)
After stirring 3 g of mercaptoacetic acid while stirring 1000 ml of a 50 mmol silver nitrate aqueous solution, the pH of the aqueous solution was adjusted to 10 with aqueous ammonia (26%). A reduction reaction was performed by rapidly adding 50 milliliters of a 40 mmol aqueous solution of sodium borohydride to the aqueous solution at room temperature, to form silver colloid particles having mercaptoacetic acid on the surface. This solution was adjusted to pH 3 with nitric acid (20%) to precipitate silver colloid particles, washed with water until the electric conductivity of the filtrate became 10 μS / cm or less by vacuum filtration, and then separated by filtration. A wet cake of colloidal particles was obtained. The wet cake of silver colloid particles was added to pure water so as to have a solid content of 10%, and the pH was adjusted to 9 with ammonia water (26%) with stirring to redisperse the silver cake. c) was obtained.
[0038]
Preparation of metal colloid solution (4)
1.5 g of 3-mercaptopropionic acid was added while stirring 1000 ml of a 25 mmol aqueous solution of chloroauric acid, and the pH of the aqueous solution was adjusted to 10 with aqueous ammonia (26%). A reduction reaction was carried out by rapidly adding 50 milliliters of a 120 mmol aqueous hydrazine solution to the aqueous solution at room temperature to generate colloidal gold particles having 3-mercaptoacetic acid on the surface. This solution was adjusted to pH 3 with hydrochloric acid (20%) to precipitate the colloidal gold particles, and then filtered, washed and redispersed in the same manner as in sample c to obtain a gold colloid solution (sample d). Was.
[0039]
Aqueous dispersion of conductive oxide
Spherical antimony-containing conductive tin oxide (specific surface area 70m 2 / G, an average particle diameter of 0.02 μm) is used as a sample e. The aqueous dispersion SN-100D (manufactured by Ishihara Sangyo Co., Ltd., solid content concentration: 30% by weight).
[0040]
Examples 1 to 5 and Comparative Examples 1 to 5
Preparation of conductive paint
Using the samples a to e, a coating was prepared according to the following prescriptions 1 and 2 to obtain the conductive coatings of the present invention (samples A to E) and the conductive coatings of the comparative examples (samples F to J).
[0041]
(Prescription 2)
* First liquid
Samples a to e 8.0 g
Pure water 20.05g
Ethylene glycol monobutyl ether 5.0 g
Acetamide 6.0 g
0.05 g of BYK-190 (organic dispersant: manufactured by BYK Chemie, active ingredient 40%)
* Second liquid
Methyl silicate 51
(Inorganic curable component: manufactured by Colcoat, solid content 51%) 4.6 g
9.0 g of ethanol
46.8 g of 2-propanol
13.0 g of 1-methoxy-2-propanol
Pure water 1.0 g
0.03 g of 20% hydrochloric acid
[0043]
Formation of conductive coating
A first liquid of the conductive paint of each of the samples A to J was applied on a 75 mm piece, 3 mm thick square glass substrate with a # 10 bar coater, air-dried for 10 minutes, and then a second liquid was applied to a # 10 bar. After coating with a coater and air drying for 10 minutes, it was heated at 150 ° C. for 30 minutes to obtain a conductive coating film.
[0044]
Evaluation: Measurement of surface resistance, haze, transmittance, evaluation of color unevenness
The surface resistance of the obtained coating film was measured using a surface resistance meter (Loresta GP type, manufactured by Mitsubishi Chemical Corporation), and the haze and transmittance were measured using a haze meter (DH-300A type, manufactured by Nippon Denshoku Industries). . The color unevenness of the coating film was evaluated by visual judgment.
[0045]
Table 1 shows the results. The two-component conductive paint of the present invention has a high conductivity even when applied with a bar coater, is excellent in transparency, and has a coating film without color unevenness, as compared with a conventional two-component conductive paint. It turns out that it can be obtained.
[0046]
[Table 1]
【The invention's effect】
The present invention is a two-part conductive paint comprising a first liquid containing a conductive medium, a dispersion medium containing water as a main component, and an organic thickener, and a second liquid containing a curable component. The liquid does not substantially contain a curable component, and the first liquid is applied to a substrate to form a layer containing conductive particles, and then the curable component is placed on the layer containing conductive particles. A conductive coating film is obtained by applying a second liquid containing the composition and curing the curable component, and is useful for imparting antistatic properties to various substrates and providing electromagnetic shielding.
[0048]
In the present invention, by adding an organic thickener to the first liquid and improving coating suitability, spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating can be performed without using spin coating. Even by a general coating method such as bar coating, die coating, brush coating, etc., a conductive coating film having a uniform film thickness and almost no color unevenness can be obtained industrially and economically advantageously. In particular, the present invention is suitable for mass-production line coating, and is capable of coating large substrates and substrates having complicated shapes.
Claims (13)
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| WO2014116767A2 (en) * | 2013-01-25 | 2014-07-31 | Imra America, Inc. | Methods for preparing aqueous suspension of precious metal nanoparticles |
| US10184025B2 (en) | 2013-01-25 | 2019-01-22 | Imra America, Inc. | Methods for preparing aqueous suspension of precious metal nanoparticles |
| WO2014141787A1 (en) * | 2013-03-12 | 2014-09-18 | 富士フイルム株式会社 | Composition for forming electrically conductive film, and method for producing electrically conductive film using same |
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