JP3694900B2 - Method for producing silica-based coating - Google Patents
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Description
【０００１】
【産業上の利用分野】
本発明は、シリカ被膜、炭化水素などの疎水性官能基を有するシリカ被膜、及びド−プドシリカ被膜の製造方法に関する。このようなシリカ被膜は、絶縁性、耐殺傷性、アルカリ溶出防止性などに優れ、撥水性コ−テイング膜や光導波路など機能膜として利用できる。
【０００２】
【従来の技術】
炭化水素基を含有するシリカ、いわゆるシリコ−ンの被膜を湿式で形成する方法として、アルキルシリコンアルコキシドからなる調製液を基材に塗布し、乾燥し、膜形成する方法が一般に行われている。また、特開昭５７−１９６７４４号公報、特開平４−１６５０５号公報などには、過飽和状態までシリカが溶解したケイフッ酸、あるいはケイフッ化アンモニウム溶液に基材を入れ、溶液中でシリカ被膜を形成する、いわゆる液相析出法が開示されている。
【０００３】
【発明が解決しようとする課題】
従来のアルコキシドの塗布法では、乾燥収縮による割れの発生、膜質の緻密性、基材との密着性などがしばしば問題になると言われてきた。また、従来の液相析出法では、過飽和状態までシリカが溶解した溶液を必要とするため、使用する溶液がケイフッ酸、あるいはケイフッ化アンモニウム溶液に限定されていた。本発明は、これらの問題を回避するため、新規な成膜方法を提供することを目的とするものである。
【０００４】
【課題を解決するための手段】
本発明者らは、シリカ系被膜の新しい形成方法について鋭意検討を行った結果、炭化水素、弗素および水素などの疎水性官能基を有するケイ酸が溶液中で基材表面に析出し、被膜を形成することを見出だし本発明に到達した。すなわち、本発明は、炭化水素、弗素および水素の中から選ばれる少なくとも１種以上の疎水性官能基を有するケイ酸を含む水系溶液に、基材を浸漬または接触させ保持することにより、溶液中で基材表面に該疎水性官能基を含むシリカを膜として析出させ、被膜を形成することを特徴とする、シリカ系被膜の製造方法である。また本発明は、上述の方法で得られたシリカ系被膜を焼成することにより、疎水性官能基を除去した、シリカ被膜または金属元素含有シリカ被膜とすることを特徴とするシリカ系被膜の製造方法である。以下、本発明をさらに詳細に説明する。
【０００５】
本発明でいう疎水性官能基とは、炭化水素、弗素、及び水素の中から選ばれる。炭化水素基としては、例えば、メチル、エチル、プロピル、ブチルなどのアルキル基、ビニルなどのアリ−ル基、フェニルなどの芳香族基などが挙げられる。これら疎水性官能基を有するケイ酸とは、一般式ＸＳｉ（ＯＨ）3（Ｘは炭化水素、弗素または水素を示す。以下同じ。）で表示される一官能性シロキサンを主体とするものが代表的であるが、これに加えて、Ｘ2Ｓｉ（ＯＨ）2で表される二官能性のものや、Ｓｉ（ＯＨ）4で表される官能基のないものを一部含んでいても構わない。また、これらモノマ−だけでなく、これらモノマ−が疎水性官能基を残したまま重合してポリマ−の形態となったものでもよい。
【０００６】
このようなケイ酸を含む溶液は、最も簡単には、例えばＲnＳｉ（ＯＲ）4-n［１≦ｎ≦２］、ＦnＳｉ（ＯＲ）4-n［１≦ｎ≦３］、およびＨnＳｉ（ＯＲ）4-n［１≦ｎ≦３］（ただしＲは炭化水素基、Ｆは弗素、Ｈは水素である）で表されるアルコキシシラン化合物を水に添加し、攪拌し、加水分解反応を進めることにより得られる。特に、アルコキシシラン化合物として、ＲＳｉ（ＯＲ）3、ＦＳｉ（ＯＲ）3、およびＨＳｉ（ＯＲ）3は、水による加水分解反応が速く、室温で短時間攪拌することにより反応が進行するため、好ましいものである。
【０００７】
ただし、炭化水素基Ｒがフェニル基などの親水性に乏しい場合は、アルコキシシランと溶媒である水との混合が進みにくくなるので、水にエタノ−ルなどのアルコ−ルを添加した後、攪拌して加水分解を進めることが好ましい。また、ＦＳｉ（ＯＲ）3、ＨＳｉ（ＯＲ）3は水による加水分解が速すぎるため、やはりエタノ−ルなどアルコ−ルで希釈した後、水に添加し、混合することが好ましい。ただし、このようなアルコ−ルが相当量含まれる水系溶媒とする場合でも、その添加量は５０ｖｏｌ％以下としなければ、被膜形成が困難となる。
【０００８】
本発明のケイ酸溶液を得るその他の方法としては、ＲＳｉＣｌ3などのアルキルクロロシランを水に加え、加水分解する方法があげられる。また、メチル基を有するケイ酸の稀薄溶液が市販されており、それを用いることもできる。
【０００９】
疎水性官能基を有するケイ酸の溶液濃度は、ＳｉＯ2換算で０．００５〜０．５ｍｏｌ／ｌの範囲にすることが好ましい。０．００５ｍｏｌ／ｌ未満では、ケイ酸の液中密度が小さすぎて、基材表面への膜の析出が認めにくい。また、ケイ酸の濃度が増加するにつれて、基材表面での膜形成のみならず、液中でのコロイド粒子の凝集も増し、沈殿を生成したり、基材表面に付着したりする現象が見られる。ケイ酸の濃度をさらに高くしても、膜形成に預からない沈殿凝集粒子が増えるだけの状態を示し始める。従って、ケイ酸濃度の上限を設けることは難しいが、そのような状態が激しくならない濃度は、ＳｉＯ2換算で０．５ｍｏｌ／ｌ以下である。通常は、０．０１〜０．１ｍｏｌ／ｌの範囲が適当であり、さらに好ましくは、０．０２〜０．０６ｍｏｌ／ｌの範囲である。
【００１０】
本発明の被膜形成プロセスは、基本的には、上記の成膜用溶液に基材を浸漬し、所定温度に保持しておくだけでなされる。被膜は時間経過とともに、溶液中で基材表面に次第に厚く形成されていく。被膜形成を促進するために、基材を浸漬した溶液は通常、室温以上の温度に加温した状態で保持される。その際、液の蒸発を防ぐため、容器を密閉することが好ましい。また、溶液を攪拌したり、時間経過とともに減っていく溶液中のケイ酸を補給するため、溶液を循環系にすることも好ましい方法である。
【００１１】
基材としては、ガラス、プラスティック、金属などあらゆる種類のものを用いることができる。
【００１２】
炭化水素基を有するシリカ被膜を形成するために、成膜用溶液として、上記炭化水素基を有するケイ酸と水、アルコールなどの溶媒のみを含む溶液を使用しても勿論構わないが、この溶液に弗素化合物を溶解することにより、被膜形成を最も促進することができる。弗素化合物としては、水に溶解性をもつ物ならいかなるものでも使用できるが、特にＮＨ4Ｆ、ＫＦ、ＮａＦ、Ｈ2ＳｉＦ6、（ＮＨ4）2ＳｉＦ6が好ましい。ＨＦはシリカ系物質を溶かすため、溶液中に含まれるケイ酸を溶かすに相当する量以上に添加することはできないが、ごく微量の添加は膜形成を促進する。溶液中の弗素化合物の濃度は、Ｆ濃度として０．８〜３．５ａｔｍ／ｌの範囲が好ましく、さらに、好ましくは１．０〜２．５ａｔｍ／ｌの範囲である。
【００１３】
成膜液のｐＨは、フッ化アンモニウム系で６〜７．５、フッ化カリウム、フッ化ナトリウム系で８〜９、ケイフッ化アンモニウム系で３〜４、ケイフッ酸系で３以下である。特にフッ化アンモニウム、フッ化カリウム系は中性付近にあり、取扱いが容易である。
【００１４】
炭化水素基を有するシリカ被膜の形成を促進させるもう一つの方法は、炭化水素基を有するケイ酸と水を含む溶液に、酸、アルカリ、及び／または無機塩を添加する方法である。酸またはアルカリを触媒として添加する方法では、例えば、ＨＣｌ、ＨＮＯ3などの酸の場合、０．００３〜０．０２ｍｏｌ／ｌ、アンモニアなどのアルカリの場合も同程度の微量で十分成膜を行うことができる。しかしながら、最も効果的で好ましいのは、ＨＣｌを１〜２ｍｏｌ／ｌと高濃度添加する方法である。酸性側では、膜の密着性がよくなるので、特に酸を添加することが好ましい。また、ＮＨ4Ｃｌ、ＮＨ4Ｆ、ＫＣｌ、ＫＦ、ＮａＣｌなどの無機塩の場合は、０．００３〜０．０３ｍｏｌ／ｌ程度の微量の添加で成膜可能であるが、１ｍｏｌ／ｌ程度の大量の添加を行っても構わない。
【００１５】
以上記載した炭化水素を有するケイ酸溶液を加温して保持すると、ケイ酸コロイドの凝集により、液の濁りが増す場合がある。この凝集コロイドは、膜形成に関与しないばかりか、膜表面に付着するため、膜面の平滑性を悪くする。従って、この場合、調製した液を室温〜８０℃で０．１〜数十間保持することにより、凝集コロイド粒子の生成をほぼ終了させ、これを分離し、残液で成膜処理することがよい。たとえば、メチルケイ酸とフッ化アンモニウムからなる液では、６０℃で２〜４時間程度保持すれば、凝集コロイド粒子の生成はほぼ終了時点に達する。凝集粒子を分離する方法として、通常、フィルタ−による濾過が適する。フィルタ−の孔径は０．１μｍ以上であることが好ましい。
【００１６】
凝集粒子の分離によって、成膜に供する液中のＳｉＯ2濃度は、調製液に比較して当然減少するが、０．０１〜０．０４ｍｏｌ／ｌの範囲にあれば、特に問題はない。この範囲に収まるように、保持時間と温度を選べば良い。
【００１７】
疎水性官能基として弗素または水素を有するケイ酸溶液は、ＦまたはＨを有するシリコンアルコキシド、たとえば、ＦＳｉ（ＯＣＨ3）3、ＦＳｉ（ＯＣ2Ｈ5）3、ＨＳｉ（ＯＣＨ3）3、ＨＳｉ（ＯＣ2Ｈ5）3などのアルコキシドを水に添加し、攪拌すればよい。この場合、すでに述べたように、アルコ−ルで薄めて、水に添加することが好ましい。溶媒としては、水以外に、水／アルコ−ル混和溶液、シリカが飽和溶解したＮＨ4 Ｆ溶液などが使用できる。
【００１８】
本発明の製造方法のもう一つは、金属元素含有シリカ被膜に関する。すなわち、疎水性官能基を有するケイ酸溶液に、加水分解する性質をもつ金属フッ化物を添加し、上述の成膜処理を行うことにより、金属元素を含有したシリカ被膜を形成する方法である。加水分解する性質をもつ金属フッ化物として、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｂ、Ｔａ、Ｓｂ、Ｐｂ、Ｓｎなどのフッ化物が存在する。特に、ＴｉＦ4、ＳｂＦ3、ＳｎＦ2およびＮｂＦ5が好ましい。成膜用溶液は、例えば最も簡単には、ＣＨ3Ｓｉ（ＯＣＨ3）3などのアルキルアルコキシドを水に添加し、数時間攪拌し、加水分解させた後、金属フッ化物を加え、混合溶解させればよい。
【００１９】
添加する金属フッ化物の濃度は、形成しようとする膜組成に応じて決定されるが、成膜用溶液の組成と膜組成は、通常同じにならない。膜に含有される金属元素は、溶液中の組成より多くなる傾向がある。たとえばスズの場合、溶液組成を原子比Ｓｎ／Ｓｉ＝１／１０にすると膜組成はＳｎ／Ｓｉ＝１／３程度となる。またチタンの場合、溶液組成Ｔｉ／Ｓｉ＝１／１０にすると、膜組成はＴｉ／Ｓｉ＝２／１程度となる。通常、シリカ被膜への金属ド−プ量は１〜２０モル％の範囲であるので、溶液組成として金属元素／Ｓｉ原子比を１／２０〜１／１００の範囲として行えばよい。
【００２０】
成膜処理は、溶液に基材を浸漬し、通常、室温から１００℃までの温度に保持することにより行われる。この加温は、溶液中のケイ酸の重合反応を高め、膜形成を促すためになされる。特に好ましい温度は、３０〜７０℃である。その場合、膜形成速度は、５〜５０ｎｍ／ｈ程度である。加圧容器を用いれば、勿論、１００℃以上の温度に保持しても構わない。
【００２１】
本発明で得られる析出被膜は、疎水性官能基を含有したシリカ被膜である。たとえば、メチル基を有するケイ酸から得られた被膜は、通常、１０〜１６モル％のＣＨ3を含有するシリカ被膜となる。また、弗素または水素を有するケイ酸から得られた被膜は、１〜５モル％の弗素または水素を有するシリカ被膜となる。また、メチル基を有するケイ酸と金属フッ化物を含む溶液から得られた被膜は、通常、メチル基と少量の弗素および金属元素を含有する被膜となる。これら炭化水素、弗素、水素は、ケイ素原子に結合した状態で含有されていると推定される。
【００２２】
この析出被膜は、加熱することにより、疎水性官能基成分が除去されたシリカ被膜に容易に変換し得る。たとえば、メチルなど炭化水素基を有するシリカ被膜は、大気中、５００℃以上の焼成で炭素分のないシリカ被膜となる。また、弗素を含むシリカ被膜は、大気中、３００℃以上の焼成でほぼ弗素のないシリカとなる。
【００２３】
本発明で成膜を可能とならしめている物質は、疎水性官能基をもつケイ酸である。この物質が水溶液中に稀薄濃度存在する場合、基材表面でのケイ酸の重合が被膜を形成する形で促進されるためと推定される。したがって、疎水性官能基をもたないケイ酸では成膜は不可能である。また、本発明は従来の液相析出法と異なり、過飽和状態までシリカが溶解した溶液を必要とせず、従って、過飽和状態を作り出すための添加剤の投与も必要としない。
【００２４】
【実施例】
以下、実施例によって、本発明をさらに説明する。しかし本発明は、これら実施例にのみ限定されるものではない。
【００２５】
（実施例１）
出発液として、メチルトリメトキシシラン（ＣＨ3Ｓｉ（ＯＣＨ3）3）を純水に添加し、４時間攪拌混合して得た４ｗｔ％溶液、フッ化アンモニウム試薬を純水に溶解した３６％ＮＨ4Ｆ溶液、および純水を用いた。メチルトリメトキシシラン溶液を純水で薄め、そこにＮＨ4Ｆ溶液を投入するという操作で、表１に示す組成の液を調製した。これら調製液を、それぞれ表１に示す条件で保持した。その後、孔径０．２μｍのフィルタ−を用いて、凝集コロイド粒子を分離し、成膜用の液を得た。各製膜用液中のＳｉ濃度及びｐＨは表１に示す通りであった。これらの液を、一旦減圧にし、液中のガスを追い出した後、基材として、ソ−ダライムガラス板とシリコンウエハ−を液中に浸漬し、密封カバ−をつけて、６０℃の恒温槽に入れ、表１に示す時間保持した。その後、基材を取り出し、水で洗浄し、乾燥した。基材表面には膜が形成されており、膜厚をＳＥＭ観察により求めた。得られた結果を表１にまとめて示す。
【００２６】
【表１】
（実施例２）
実施例１で得られたシリコンウエハ−基板上の膜を赤外吸収スペクトルにより分析した。Ｓｉ−Ｏ結合に基づく吸収とＳｉ−ＣＨ3結合に起因する吸収が観察され、シリコ−ン系の膜が形成されていることが判った。また、ＥＳＣＡによる分析の結果、主成分として、Ｓｉ、Ｏ、Ｃが検出された。Ｃ含量は、表１のＮｏ１の試料で１５ａｔｍ％、Ｎｏ１２で１２ａｔｍ％であった。これらの結果から得られた膜は、メチル基を含む酸化ケイ素（シリコ−ン）であることが確認された。
【００２８】
（実施例３）
市販シリカゾル（商品名「セラメ−トＣ−１００」）とＮＨ4Ｆ溶液及び純水を用いて、表２に示す組成の調製液を作成した。調製液を６０℃で２ｈ保持することにより、凝集粒子を生成させ、それを孔径０．２μｍのフィルタ−で分離した液を成膜用液とした。基材として、ソ−ダライムガラス、シリコンウエハーを用い、４０℃で成膜処理を行った。基材上には、緻密な膜が形成さており、実施例２と同様の分析の結果、シリコ−ン系被膜と確認された。結果をまとめて表２に示す。
【００２９】
【表２】
（実施例４）
出発液として、メチルトリエトキシシランを純水に添加し１５時間攪拌して得た４％溶液、フッ化カリウム試薬を純水に溶解した４５％溶液、および純水を用いた。メチルトリエトキシシラン液を純水で薄めた液を攪拌し、そこにＫＦ溶液を投入するという操作で、表３に示す組成の液を調製した。これら調製液を表３に示す条件で保持した。以下、実施例１と同様の方法で、フィルター瀘過及び減圧処理した後、表３に示す製膜処理条件で成膜を行い、膜厚をＳＥＭ観察により求めた。また得られた膜について、実施例２と同様の分析を行い、シリコ−ン系被膜であることを確認した。さらに、膜中にはカリウムがまったく含まれないこともＥＳＣＡ分析の結果、判った。結果を表３に示す。
【００３１】
【表３】
（実施例５）
実施例１のソ−ダライムガラス基板上のシリコーン系被膜（表１のＮｏ１）を大気中で、２００、３００、４００、又は５００℃で各１時間焼成した。ＥＳＣＡによる分析の結果、３００℃までの膜にはＣ成分が含まれるが、それ以上の温度では、Ｃがまったく含まれないシリカ系被膜となることがわかった。実施例４のシリコンウエハー上の試料（表３のＮｏ１）をＨｅ中で、４００、５００、又は６００℃で各１時間焼成した。ＩＲによる分析の結果、６００℃でシリカ系被膜になることが判った。焼成した膜は、割れの発生を伴わない、緻密なものであった。
【００３３】
（実施例６）
ケイフッ化アンモニウム溶液（濃度１ｍｏｌ／ｌ）１００ｍｌ中に、メチルトリメトキシシランを純水中で加水分解した４ｗｔ％溶液９ｍｌを加えた。液を減圧にし、脱気した後、基材としてシリコンウエハ−とソ−ダライムガラスを浸漬し、６０℃で２０ｈ保持し成膜処理した。基材表面には、厚み０．６μｍの膜が形成されており、実施例２と同様の分析の結果、シリコ−ン系膜であることが判った。
【００３４】
（実施例７）
４０℃の恒温槽に保ったケイフッ化水素酸溶液（濃度２ｍｏｌ／ｌ）１００ｍｌ中に、メチルトリメトキシシランを純水中で加水分解した４ｗｔ％溶液９ｍｌを加え、攪拌した。そこに、基材としてシリコンウエハ−とソ−ダライムガラスを浸漬し、４０℃で２０ｈ保持し成膜処理した。基材表面には、厚み０．５μｍの膜が形成されており、実施例２と同様の分析の結果、Ｃ成分が極めて少ない酸化ケイ素膜であることが判った。
【００３５】
（実施例８）
ＣＨ3Ｓｉ（ＯＣＨ3）3４０ｇを純水１０００ｍｌに入れ５時間攪拌し加水分解して得たケイ酸溶液、濃塩酸および純水を用い、それぞれの量を、１１ｍｌ／１０ｍｌ／７９ｍｌ、１１ｍｌ／２０ｍｌ／６９ｍｌおよび１１ｍｌ／３０ｍｌ／５９ｍｌの割合で混合した３種の溶液を調製した。一旦減圧して脱気した後基材として、シリコンウエハ−とソ−ダライムガラスを各溶液に浸漬し、６０℃で２０ｈ保持し成膜処理した。各基材表面には膜が形成されており、膜の厚みはＳＥＭ観察より約０．４μｍであると判った。また、赤外線吸収スペクトルとＥＳＣＡによる分析の結果、この膜はＣＨ3基を有する酸化ケイ素（シリコ−ン）であることが判った。
【００３６】
（実施例９）
ＣＨ3Ｓｉ（ＯＣＨ3）3の加水分解液と、添加剤として１．０モル／リットルのＨＣｌ溶液、１．６モル／リットルのＮＨ3 水の一方或いは両方を用いて、表４Ｎｏ１−５の調製液を調製した。これらの調製液各１００ｍｌを用い、実施例１と同様にして成膜実験を行い、シリコ−ン被膜が形成されていることを確認した。以上の結果を表４のＮｏ１〜５に示す。
【００３７】
【表４】
（実施例１０）
ＣＨ3Ｓｉ（ＯＣ2Ｈ5）3とＳｉ（ＯＣＨ3）4をモル比３：１で水に加えた溶液と、添加剤として１．６モル／リットルのＮＨ3溶液、２．３モル／リットルのＨＦ溶液、および１．０モル／リットルのＨＮＯ3溶液とを用いて、表４のＮｏ６−８の調製液を調製した。各々の液１００ｍｌに、基材としてソ−ダライムガラス板を浸漬し、３０℃で、４０時間保持した後、基材を取りだし、水で洗浄し、乾燥させ、基材上に膜が形成されていることを確認した。膜厚をＳＥＭ観察から求めた。以上、得られた結果を表４のＮｏ６〜８に示す。
【００３９】
（実施例１１）
オルガノシロキサンを含む市販シリカゾル（商品名セラメ−トＣ−１００）と添加剤としてＮＨ3、ＨＣｌ、ＨＦを使用して、表５の初期調製液を調製した後調製液を表５に記載の温度、時間で放置し、初期沈殿を発生させた。その液を孔径０．２μｍのフィルタ−に通し、沈殿を除去した。瀘液を調製液としてソーダライムガラス又はシリコンウエハーの基材を浸漬し、６０℃で１５時間保持し、シリコ−ン系膜の形成を行った。以上の結果を表５のＮｏ１〜６に示す。
【００４０】
【表５】
（実施例１２）
添加剤として、１ｍｏｌ／ｌの濃度に調製したＮＨ4Ｆ溶液、ＮＨ4Ｃｌ溶液ＫＦ溶液、ＫＣｌ溶液、およびＮａＣｌ溶液を用いた以外は、実施例１０と同様の方法で表６の初期調製液を調製し、表６に記載の温度、時間で放置し、初期沈殿を発生させた。その液を実施例１０と同様にして瀘過し、瀘液を調製液としてソーダライムガラスを６０℃、２０時間浸漬し、表６のＮｏ１〜９の結果を得、シリコ−ン膜の形成を確認した。
【００４２】
【表６】
（実施例１３）
ＣＨ3ＳｉＣｌ3を水に吸収させ、加水分解した溶液（Ｓｉ濃度０．２モル／リットル）をケイ酸溶液として用いた以外は、実施例１１と同様の方法で表７の初期調製液を調製し、表７に記載の時間、温度で放置し、初期沈殿を発生させた。その液を実施例１１と同様にして瀘過し、瀘液を調製液としてソーダライムガラスを７０℃、１５時間浸漬し、表７のＮｏ１〜４の結果を得、シリコ−ン膜の形成を確認した。
【００４４】
【表７】
（実施例１４）
実施例８で出発液として用いたケイ酸溶液をＳｉ濃度０．１５ｍｏｌ／ｌとなるよう純水で薄め、８０℃で２０時間保持した。これにより、液の濁りが増加したので、孔径０．２μｍのフィルタ−で凝集沈殿を除去した。除去後の瀘液中のＳｉ濃度は、０．１２ｍｏｌ／ｌとなった。この瀘液に基材としてスライドガラスを液面に垂直となるように浸漬した。容器を密閉後、再び８０℃で２０時間保持した。これにより、スライドガラス上にシリコ−ン膜が形成できた。
【００４６】
（実施例１５）
実施例８で得られたガラス基板上のシリコ−ン被膜を大気中５００℃で１時間焼成した。ＥＳＣＡによる分析の結果、ＳｉとＯのみが検出され、ＣＨ成分が除去されたシリカ膜になることが判った。
【００４７】
（実施例１６）
試薬フルオロトリエトキシシラン、ＦＳｉ（ＯＣ2Ｈ5）3０．５４ｇをエタノ−ル１０ｍｌに溶かし、それを水９０ｍｌに攪拌しながら添加した。液は懸濁したが、３０分間静置した。その後、基材として、シリコン基板とソ−ダライムガラス板を浸漬し、密封した。それを４０℃に保持した恒温槽に入れ、４０時間放置した。一方、同様にして、保持温度を７０℃とし、２４時間放置する実験も行った。それぞれの放置後、基材を液から取り出し、水で洗浄し、乾燥させた。保持温度にかかわらず、シリコン基板、ソ−ダライムガラスのどちらの基材上にも、薄膜が形成されていた。
【００４８】
シリコン上の薄膜の赤外吸収スペクトルを測定した結果、ＳｉＯ2に特有な吸収が見られた。またＥＳＣＡにより分析した結果、Ｓｉ：３３ａｔｍ％、Ｏ：６５ａｔｍ％、Ｆ：２ａｔｍ％の値が得られた。これらの結果から、少量の弗素を含む二酸化ケイ素の薄膜が得られていることがわかった。またＳＥＭ観察によって膜を観察した結果、膜厚は、保持温度４０℃で０．３μｍ，７０℃で０．２μｍであることがわかった。
【００４９】
（実施例１７）
試薬トリメトキシシラン、ＨＳｉ（ＯＣＨ3）3０．４９ｇをエタノ−ル２０ｍｌに溶かし、それを水８０ｍｌに攪拌しながら添加した。液は懸濁したが、３０分間静置した。その後、基材としてシリコン基板とソ−ダライムガラス板を浸漬し、密封した。それを６０℃に保持した恒温槽に入れ、４０時間放置した。放置後、基材を液から取り出し、水で洗浄し、乾燥させた。シリコン、ソ−ダライムどちらの基材上にも、多孔質の薄膜が形成されていた。
【００５０】
シリコン上の薄膜の赤外吸収スペクトルを測定した結果、ＳｉＯ2に特有な吸収が見られた。また、ＥＳＣＡにより分析した結果、Ｓｉ：３５ａｔｍ％、Ｏ：６５ａｔｍ％の値が得られた。これらの結果から、二酸化ケイ素の薄膜が得られていることがわかった。またＳＥＭ観察によって膜を観察した結果、膜厚は、０．２μｍであることがわかった。
【００５１】
（実施例１８）
出発液として、メチルトリメトキシシラン（ＣＨ3Ｓｉ（ＯＣＨ3）3）を純水に添加し、４時間攪拌混合した４ｗｔ％溶液と、ＴｉＦ4試薬、および純水を用いた。メチルトリメトキシシラン溶液を純水で薄め、攪拌しながら、そこに、ＴｉＦ4を所定量投入し、さらに攪拌するという操作で、表８に示す組成の液を調製した。これらの液を、一旦減圧にし、液中のガスを追い出した後、基材として、石英ガラス板とシリコンウエハ−を液中に浸漬し、密封カバ−をつけて、６０℃の恒温槽に入れ、１５時間保持した。その後、基材を取り出し、水で洗浄し、乾燥した。
【００５２】
基材表面には膜が形成されており、膜厚をＳＥＭ観察により求めた。またシリコンウエハ−基板上に形成された膜を、赤外吸収スペクトルにより分析したところ、Ｓｉ−Ｏ結合に基づく吸収と、Ｓｉ−ＣＨ3結合に起因する吸収とが観察され、炭化水素基含有シリカ被膜が形成されていることが判った。また、ＥＳＣＡによる分析の結果、主成分としてＳｉ、Ｔｉ、Ｏ、Ｃが検出され、さらにＮｏ．１の被膜ではＦが検出された。結果を表８に示す。表中、ｎ．ｄ．は検出されないことを示す。膜組成は表８に示す通りであり、Ｔｉがド−プされていることが判った。
【００５３】
【表８】
（実施例１９）
ＴｉＦ4試薬をＳｎＦ2試薬に代えた以外は、実施例１８と同様の方法で膜形成を行った。基材表面には膜が形成されており、膜圧をＳＥＭ観察により求めた。またシリコンウエハー基板上に形成された膜を、赤外吸収スペクトルにより分析したところ、Ｓｉ−Ｏ結合に基づく吸収と、Ｓｉ−ＣＨ3結合に起因する吸収とが観察され、炭化水素含有シリカ被膜が形成されていることが判った。また、ＥＳＣＡによる分析の結果、主成分としてＳｉ、Ｓｎ、Ｏ、Ｃが検出され、さらにＮｏ．１の被膜ではＦが検出された。結果を表９に示す。表中、ｎ．ｄ．は検出されないことを示す。膜組成は表９に示す通りであり、Ｓｎがド−プされていることが判った。
【００５５】
【表９】
（実施例２０）
実施例１８、１９で得られた石英ガラス板上の膜を大気中、８００℃で、１時間、焼成した。得られた膜をＥＳＣＡにより分析した結果、Ｃ、Ｆはまったく検出されず、実施例１８で得られた膜を焼成したものからは、Ｓｉ、Ｏ、Ｔｉのみが検出され、実施例１９で得られた膜を焼成したものからは、Ｓｉ、Ｏ、Ｓｎのみが検出された。ド−プ元素であるＴｉ、ＳｎのＳｉに対するモル比はそれぞれ焼成前と同じであった。このことから、ＴｉあるいはＳｎがド−プされ、炭化水素基を含まないシリカ膜であることが判った。
【００５７】
（実施例２１）
ビニルトリメトキシシランＣＨ2 ＣＨＳｉ（ＯＣＨ3）3、トリフルオロプロピルトリメトキシシランＣＦ3ＣＨ2ＣＨ2Ｓｉ（ＯＣＨ3）3、水及びフッ化アンモニウムを用いて、ビニルトリメトキシシラン０．０３ｍｏｌ／ｌ及びフッ化アンモニウム１．５ｍｏｌ／ｌを含む溶液、ならびにトリフルオロプロピルメトキシシラン０．０３ｍｏｌ／ｌ及びフッ化アンモニウム１．５ｍｏｌ／ｌを含む溶液をそれぞれ調製した。各溶液をガラス製ビ−カ−に入れ、攪拌しながら６０℃に加熱し、１５時間保持した。保持後、溶液を排出し、ビ−カ−の内面に被膜が形成されていることを確認した。ビ−カ−の一部を切り出し、ＩＲスペクトルを測定した結果、それぞれビニル基を含むシリカ被膜、トリフルオロプロピル基を含むシリカ被膜であることがわかった。
【００５８】
【発明の効果】
本発明は、液相中でシリカ系被膜を直接形成する方法を提供する。本法の特徴として、低温で膜形成できる、大面積の膜形成が容易である、一度に大量の膜付けが行える、任意形状の表面に膜形成可能、さらに、製造装置が簡便なものとなるなどが挙げられる。従って、工業上、価値ある方法となる。[0001]
[Industrial application fields]
The present invention relates to a silica coating, a silica coating having a hydrophobic functional group such as a hydrocarbon, and a method for producing a doped silica coating. Such a silica film is excellent in insulating properties, kill resistance, alkali elution prevention properties, and the like, and can be used as a functional film such as a water-repellent coating film or an optical waveguide.
[0002]
[Prior art]
As a method for wet-forming a silica-containing silica, that is, a so-called silicon film, a method of forming a film by applying a preparation solution comprising an alkyl silicon alkoxide to a substrate and drying it is generally performed. Further, in Japanese Patent Laid-Open Nos. 57-196744 and 4-16505, etc., a silica coating is formed in a solution by placing the substrate in silicic hydrofluoric acid or ammonium silicofluoride solution in which silica is dissolved to a supersaturated state. A so-called liquid phase precipitation method is disclosed.
[0003]
[Problems to be solved by the invention]
In the conventional alkoxide coating method, it has been said that the occurrence of cracks due to drying shrinkage, the denseness of the film quality, the adhesion to the base material, and the like often become problems. In addition, since the conventional liquid phase precipitation method requires a solution in which silica is dissolved to a supersaturated state, the solution to be used is limited to silicic acid or ammonium silicofluoride solution. An object of the present invention is to provide a novel film forming method in order to avoid these problems.
[0004]
[Means for Solving the Problems]
As a result of intensive studies on a new method for forming a silica-based coating, the present inventors have found that silicic acid having a hydrophobic functional group such as hydrocarbon, fluorine and hydrogen is deposited on the substrate surface in a solution, and the coating is formed. The present invention has been found out. That is, the present invention provides a solution in which a substrate is immersed in or brought into contact with an aqueous solution containing silicic acid having at least one hydrophobic functional group selected from hydrocarbon, fluorine and hydrogen. The method for producing a silica-based film is characterized in that silica containing the hydrophobic functional group is deposited as a film on the surface of the substrate to form a film. Further, the present invention provides a method for producing a silica-based film, wherein the silica-based film obtained by the above-described method is baked to obtain a silica film or a metal element-containing silica film from which hydrophobic functional groups have been removed. It is. Hereinafter, the present invention will be described in more detail.
[0005]
The hydrophobic functional group referred to in the present invention is selected from hydrocarbons, fluorine, and hydrogen. Examples of the hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, and butyl, aryl groups such as vinyl, and aromatic groups such as phenyl. These silicic acids having a hydrophobic functional group are represented by the general formula XSi (OH) Three (X is a hydrocarbon, fluorine or hydrogen. The same shall apply hereinafter.) 2 Si (OH) 2 A bifunctional compound represented by the formula: Si (OH) Four It may contain a part of those having no functional group. In addition to these monomers, those monomers may be polymerized in the form of a polymer by leaving a hydrophobic functional group.
[0006]
Such a solution containing silicic acid is most simply, for example, R n Si (OR) 4-n [1 ≦ n ≦ 2], F n Si (OR) 4-n [1 ≦ n ≦ 3] and H n Si (OR) 4-n It is obtained by adding an alkoxysilane compound represented by [1 ≦ n ≦ 3] (where R is a hydrocarbon group, F is fluorine, and H is hydrogen) to water, stirring, and proceeding with a hydrolysis reaction. . In particular, as an alkoxysilane compound, RSi (OR) Three , FSi (OR) Three , And HSi (OR) Three Is preferable because the hydrolysis reaction with water is fast and the reaction proceeds by stirring for a short time at room temperature.
[0007]
However, when the hydrocarbon group R is poor in hydrophilicity such as a phenyl group, mixing of alkoxysilane and water as a solvent is difficult to proceed. Therefore, after adding an alcohol such as ethanol to water, stirring is performed. It is preferable to proceed with hydrolysis. FSi (OR) Three , HSi (OR) Three Since water is hydrolyzed too quickly, it is preferably diluted with alcohol such as ethanol and then added to water and mixed. However, even when an aqueous solvent containing a considerable amount of such an alcohol is used, it is difficult to form a film unless the amount added is 50 vol% or less.
[0008]
Other methods for obtaining the silicic acid solution of the present invention include RSiCl. Three The method of adding alkyl chlorosilanes, such as these, to water and hydrolyzing is mentioned. In addition, dilute solutions of silicic acid having a methyl group are commercially available and can be used.
[0009]
The solution concentration of silicic acid having a hydrophobic functional group is SiO 2 2 It is preferable to make it the range of 0.005-0.5 mol / l in conversion. If it is less than 0.005 mol / l, the density of silicic acid in the liquid is too small, and deposition of a film on the substrate surface is difficult to be recognized. In addition, as the concentration of silicic acid increases, not only film formation on the substrate surface, but also aggregation of colloidal particles in the liquid increases, and a phenomenon is observed in which precipitation occurs and adheres to the substrate surface. It is done. Even if the concentration of silicic acid is further increased, it begins to show a state where only precipitated aggregated particles that are not deposited in film formation increase. Therefore, it is difficult to set the upper limit of the silicic acid concentration, but the concentration at which such a state does not become intense is SiO 2 2 It is 0.5 mol / l or less in terms of conversion. Usually, the range of 0.01 to 0.1 mol / l is appropriate, and more preferably 0.02 to 0.06 mol / l.
[0010]
The film forming process of the present invention is basically carried out simply by immersing the substrate in the film forming solution and keeping it at a predetermined temperature. As time passes, the coating is gradually formed thicker on the surface of the substrate in the solution. In order to promote film formation, the solution in which the base material is immersed is usually held in a state heated to a temperature of room temperature or higher. At that time, it is preferable to seal the container in order to prevent evaporation of the liquid. It is also a preferable method to make the solution into a circulation system in order to stir the solution or to replenish silicic acid in the solution that decreases with time.
[0011]
As the substrate, all kinds of materials such as glass, plastic and metal can be used.
[0012]
Of course, in order to form a silica coating having hydrocarbon groups, a solution containing only the hydrocarbon group-containing silicic acid and a solvent such as water or alcohol may be used as the film-forming solution. The film formation can be most promoted by dissolving the fluorine compound. Any fluorine compound can be used as long as it is soluble in water. Four F, KF, NaF, H 2 SiF 6 , (NH Four ) 2 SiF 6 Is preferred. Since HF dissolves silica-based materials, it cannot be added beyond the amount corresponding to dissolving silicic acid contained in the solution. However, addition of a very small amount promotes film formation. The concentration of the fluorine compound in the solution is preferably in the range of 0.8 to 3.5 atm / l as the F concentration, more preferably in the range of 1.0 to 2.5 atm / l.
[0013]
The pH of the film-forming solution is 6 to 7.5 for ammonium fluoride, 8 to 9 for potassium fluoride and sodium fluoride, 3 to 4 for ammonium silicofluoride, and 3 or less for silicofluoric acid. In particular, ammonium fluoride and potassium fluoride are near neutral and easy to handle.
[0014]
Another method for promoting the formation of a silica coating having hydrocarbon groups is to add an acid, alkali, and / or inorganic salt to a solution containing silicic acid having hydrocarbon groups and water. In the method of adding an acid or alkali as a catalyst, for example, HCl, HNO Three In the case of an acid such as 0.003 to 0.02 mol / l, an alkali such as ammonia can be sufficiently formed with a small amount of the same degree. However, the most effective and preferable method is to add HCl at a high concentration of 1 to 2 mol / l. On the acidic side, since the adhesion of the film is improved, it is particularly preferable to add an acid. NH Four Cl, NH Four In the case of inorganic salts such as F, KCl, KF, and NaCl, a film can be formed by adding a small amount of about 0.003 to 0.03 mol / l, but a large amount of about 1 mol / l may be added. Absent.
[0015]
When the silicic acid solution having hydrocarbons described above is heated and held, the turbidity of the liquid may increase due to aggregation of the silicic acid colloid. This aggregated colloid not only does not participate in film formation but also adheres to the film surface, thus deteriorating the smoothness of the film surface. Therefore, in this case, by maintaining the prepared liquid at room temperature to 80 ° C. for 0.1 to several tens, the formation of the aggregated colloidal particles is almost completed, and this can be separated and subjected to film formation with the remaining liquid. Good. For example, in a liquid composed of methyl silicic acid and ammonium fluoride, the aggregated colloidal particles almost reach the end point when kept at 60 ° C. for about 2 to 4 hours. As a method for separating the agglomerated particles, filtration with a filter is usually suitable. The pore diameter of the filter is preferably 0.1 μm or more.
[0016]
By separating the aggregated particles, the SiO in the liquid used for film formation 2 The concentration naturally decreases as compared with the preparation solution, but there is no particular problem if it is in the range of 0.01 to 0.04 mol / l. What is necessary is just to select holding time and temperature so that it may fall in this range.
[0017]
Silicic acid solutions having fluorine or hydrogen as the hydrophobic functional group can be used for silicon alkoxides with F or H, for example FSi (OCH Three ) Three , FSi (OC 2 H Five ) Three , HSi (OCH Three ) Three , HSi (OC 2 H Five ) Three The alkoxide such as can be added to water and stirred. In this case, as already described, it is preferable to dilute with alcohol and add to water. As the solvent, in addition to water, a water / alcohol mixed solution, NH in which silica is saturated and dissolved Four F solution etc. can be used.
[0018]
Another of the production methods of the present invention relates to a metal element-containing silica coating. That is, it is a method of forming a silica film containing a metal element by adding a metal fluoride having a hydrolyzing property to a silicic acid solution having a hydrophobic functional group and performing the above-described film forming treatment. Fluorides such as Ti, V, Cr, Mn, Fe, Co, Nb, Ta, Sb, Pb, and Sn exist as metal fluorides having the property of hydrolyzing. In particular, TiF Four , SbF Three , SnF 2 And NbF Five Is preferred. The film-forming solution is, for example, the simplest, CH Three Si (OCH Three ) Three After adding an alkyl alkoxide such as water to water, stirring for several hours and hydrolyzing, a metal fluoride may be added and mixed and dissolved.
[0019]
The concentration of the metal fluoride to be added is determined according to the film composition to be formed, but the composition of the film-forming solution and the film composition are usually not the same. The metal element contained in the film tends to be larger than the composition in the solution. For example, in the case of tin, when the solution composition is the atomic ratio Sn / Si = 1/10, the film composition becomes about Sn / Si = 1/3. In the case of titanium, when the solution composition Ti / Si = 1/10, the film composition is about Ti / Si = 2/1. Usually, since the amount of metal doping to the silica coating is in the range of 1 to 20 mol%, the metal composition / Si atomic ratio may be set in the range of 1/20 to 1/100 as the solution composition.
[0020]
The film forming process is performed by immersing the base material in a solution and maintaining the temperature usually from room temperature to 100 ° C. This heating is performed in order to enhance the polymerization reaction of silicic acid in the solution and promote film formation. A particularly preferable temperature is 30 to 70 ° C. In that case, the film formation rate is about 5 to 50 nm / h. Of course, if a pressurized container is used, it may be maintained at a temperature of 100 ° C. or higher.
[0021]
The deposited film obtained in the present invention is a silica film containing a hydrophobic functional group. For example, a film obtained from silicic acid having a methyl group is usually 10 to 16 mol% CH. Three A silica coating containing A film obtained from silicic acid having fluorine or hydrogen is a silica film having 1 to 5 mol% of fluorine or hydrogen. A film obtained from a solution containing silicic acid having a methyl group and a metal fluoride is usually a film containing a methyl group, a small amount of fluorine, and a metal element. These hydrocarbons, fluorine and hydrogen are presumed to be contained in a state bonded to silicon atoms.
[0022]
This deposited film can be easily converted into a silica film from which the hydrophobic functional group component has been removed by heating. For example, a silica coating having a hydrocarbon group such as methyl becomes a silica coating free from carbon by firing at 500 ° C. or higher in the atmosphere. Further, the silica coating containing fluorine becomes silica substantially free of fluorine when fired at 300 ° C. or higher in the atmosphere.
[0023]
The substance that enables film formation in the present invention is silicic acid having a hydrophobic functional group. When this substance is present in a dilute concentration in an aqueous solution, it is presumed that the polymerization of silicic acid on the surface of the substrate is promoted in the form of a film. Therefore, film formation is impossible with silicic acid having no hydrophobic functional group. Further, unlike the conventional liquid phase precipitation method, the present invention does not require a solution in which silica is dissolved to a supersaturated state, and therefore does not require the administration of an additive for creating the supersaturated state.
[0024]
【Example】
Hereinafter, the present invention will be further described by way of examples. However, the present invention is not limited only to these examples.
[0025]
(Example 1)
As a starting solution, methyltrimethoxysilane (CH Three Si (OCH Three ) Three 4 wt% solution obtained by adding the mixture to pure water and stirring and mixing for 4 hours, 36% NH in which an ammonium fluoride reagent is dissolved in pure water Four F solution and pure water were used. Dilute the methyltrimethoxysilane solution with pure water and add NH Four A liquid having the composition shown in Table 1 was prepared by the operation of adding the F solution. These preparation solutions were each held under the conditions shown in Table 1. Thereafter, the agglomerated colloidal particles were separated using a filter having a pore diameter of 0.2 μm to obtain a liquid for film formation. Table 1 shows the Si concentration and pH in each film-forming solution. These liquids are once depressurized and the gas in the liquids is expelled. Then, a soda lime glass plate and a silicon wafer are immersed in the liquid as a base material, a sealed cover is attached, and a constant temperature of 60 ° C. It put into the tank and hold | maintained for the time shown in Table 1. Thereafter, the substrate was taken out, washed with water and dried. A film was formed on the substrate surface, and the film thickness was determined by SEM observation. The obtained results are summarized in Table 1.
[0026]
[Table 1]
(Example 2)
The film on the silicon wafer-substrate obtained in Example 1 was analyzed by infrared absorption spectrum. Absorption based on Si-O bond and Si-CH Three Absorption due to binding was observed, and it was found that a silicon-based film was formed. As a result of analysis by ESCA, Si, O, and C were detected as main components. The C content was 15 atm% for the sample No. 1 in Table 1 and 12 atm% for No12. The film obtained from these results was confirmed to be silicon oxide containing a methyl group.
[0028]
(Example 3)
Commercially available silica sol (trade name “Ceramate C-100”) and NH Four A preparation solution having the composition shown in Table 2 was prepared using the F solution and pure water. By holding the prepared liquid at 60 ° C. for 2 hours, aggregated particles were generated, and a liquid obtained by separating the aggregated particles with a filter having a pore diameter of 0.2 μm was used as a film forming liquid. As a base material, soda lime glass and a silicon wafer were used, and film formation was performed at 40 ° C. A dense film was formed on the substrate. As a result of the same analysis as in Example 2, it was confirmed that the film was a silicon-based film. The results are summarized in Table 2.
[0029]
[Table 2]
(Example 4)
As a starting solution, a 4% solution obtained by adding methyltriethoxysilane to pure water and stirring for 15 hours, a 45% solution in which a potassium fluoride reagent was dissolved in pure water, and pure water were used. A liquid having a composition shown in Table 3 was prepared by stirring a liquid obtained by diluting a methyltriethoxysilane liquid with pure water and adding a KF solution thereto. These preparation solutions were maintained under the conditions shown in Table 3. Then, after filtering and reducing pressure by the same method as in Example 1, film formation was performed under the film forming conditions shown in Table 3, and the film thickness was determined by SEM observation. The obtained film was analyzed in the same manner as in Example 2 to confirm that it was a silicon-based film. Furthermore, as a result of ESCA analysis, it was found that no potassium was contained in the film. The results are shown in Table 3.
[0031]
[Table 3]
(Example 5)
The silicone-based film (No. 1 in Table 1) on the soda lime glass substrate of Example 1 was baked at 200, 300, 400, or 500 ° C. for 1 hour in the air. As a result of analysis by ESCA, it was found that the film up to 300 ° C. contained a C component, but at a temperature higher than that, a silica-based film containing no C was obtained. The sample (No. 1 in Table 3) on the silicon wafer of Example 4 was baked in He at 400, 500, or 600 ° C. for 1 hour each. As a result of IR analysis, it was found that a silica-based film was formed at 600 ° C. The fired film was dense without cracking.
[0033]
(Example 6)
9 ml of a 4 wt% solution obtained by hydrolyzing methyltrimethoxysilane in pure water was added to 100 ml of an ammonium silicofluoride solution (concentration: 1 mol / l). After depressurizing and degassing the liquid, a silicon wafer and soda lime glass were immersed as a substrate, and the film was processed by holding at 60 ° C. for 20 hours. A film having a thickness of 0.6 μm was formed on the surface of the substrate, and as a result of the same analysis as in Example 2, it was found that the film was a silicon-based film.
[0034]
(Example 7)
9 ml of a 4 wt% solution obtained by hydrolyzing methyltrimethoxysilane in pure water was added to 100 ml of a hydrosilicofluoric acid solution (concentration 2 mol / l) kept in a constant temperature bath at 40 ° C. and stirred. A silicon wafer and soda lime glass were immersed therein as a base material, and the film was formed by holding at 40 ° C. for 20 hours. A film having a thickness of 0.5 μm was formed on the surface of the substrate. As a result of the same analysis as in Example 2, it was found that the film was a silicon oxide film with very little C component.
[0035]
(Example 8)
CH Three Si (OCH Three ) Three 40 g was put in 1000 ml of pure water and stirred for 5 hours to hydrolyze, using a silicic acid solution, concentrated hydrochloric acid and pure water, and the amounts were 11 ml / 10 ml / 79 ml, 11 ml / 20 ml / 69 ml and 11 ml / 30 ml / Three kinds of solutions mixed at a ratio of 59 ml were prepared. Once depressurized by depressurization, a silicon wafer and soda lime glass were immersed in each solution as a base material and kept at 60 ° C. for 20 hours for film formation. A film was formed on the surface of each substrate, and the thickness of the film was found to be about 0.4 μm by SEM observation. As a result of analysis by infrared absorption spectrum and ESCA, this film was found to be CH Three It was found to be a silicon oxide having a group.
[0036]
Example 9
CH Three Si (OCH Three ) Three And a 1.0 mol / liter HCl solution, 1.6 mol / liter NH as additives. Three The preparation liquid of Table 4 No1-5 was prepared using one or both of water. Using 100 ml of each of these prepared solutions, a film formation experiment was performed in the same manner as in Example 1, and it was confirmed that a silicon film was formed. The above results are shown in Nos. 1 to 5 in Table 4.
[0037]
[Table 4]
(Example 10)
CH Three Si (OC 2 H Five ) Three And Si (OCH Three ) Four With a molar ratio of 3: 1 to water and 1.6 mol / liter NH as additive. Three Solution, 2.3 mol / liter HF solution, and 1.0 mol / liter HNO Three Using the solution, a preparation solution of No. 6-8 in Table 4 was prepared. A soda lime glass plate is immersed in 100 ml of each liquid as a base material and kept at 30 ° C. for 40 hours, and then the base material is taken out, washed with water and dried to form a film on the base material. Confirmed that. The film thickness was determined from SEM observation. The obtained results are shown in Nos. 6 to 8 in Table 4.
[0039]
(Example 11)
Commercial silica sol containing organosiloxane (trade name Ceramate C-100) and NH as additive Three After preparing the initial preparation liquid shown in Table 5 using HCl, HF, the preparation liquid was allowed to stand at the temperature and time shown in Table 5 to cause initial precipitation. The liquid was passed through a filter having a pore diameter of 0.2 μm to remove the precipitate. A soda lime glass or silicon wafer base material was immersed in the prepared solution as a preparation solution and held at 60 ° C. for 15 hours to form a silicon-based film. The above results are shown in Nos. 1 to 6 in Table 5.
[0040]
[Table 5]
(Example 12)
NH prepared at a concentration of 1 mol / l as an additive Four F solution, NH Four Except for using Cl solution KF solution, KCl solution, and NaCl solution, prepare the initial preparation liquid of Table 6 in the same manner as in Example 10, and leave it at the temperature and time described in Table 6 to precipitate the initial precipitate. Generated. The solution was filtered in the same manner as in Example 10, soda lime glass was immersed at 60 ° C. for 20 hours using the filtrate as a preparation solution, and the results of Nos. 1 to 9 in Table 6 were obtained to form a silicon film. confirmed.
[0042]
[Table 6]
(Example 13)
CH Three SiCl Three Was prepared in the same manner as in Example 11 except that a hydrolyzed solution (Si concentration 0.2 mol / liter) was used as the silicic acid solution. The mixture was allowed to stand at the temperature for the time described in 1. to cause initial precipitation. The solution was filtered in the same manner as in Example 11, soda lime glass was immersed at 70 ° C. for 15 hours using the filtrate as a preparation solution, and the results of Nos. 1 to 4 in Table 7 were obtained to form a silicon film. confirmed.
[0044]
[Table 7]
(Example 14)
The silicic acid solution used as the starting liquid in Example 8 was diluted with pure water so that the Si concentration was 0.15 mol / l, and kept at 80 ° C. for 20 hours. As a result, the turbidity of the liquid increased, and the aggregated precipitate was removed with a filter having a pore diameter of 0.2 μm. The Si concentration in the filtrate after the removal was 0.12 mol / l. A slide glass as a base material was immersed in the liquid so as to be perpendicular to the liquid surface. After sealing the container, it was kept again at 80 ° C. for 20 hours. As a result, a silicon film could be formed on the slide glass.
[0046]
(Example 15)
The silicon film on the glass substrate obtained in Example 8 was baked at 500 ° C. for 1 hour in the air. As a result of analysis by ESCA, it was found that only a Si and O were detected and a silica film from which a CH component was removed was obtained.
[0047]
(Example 16)
Reagents Fluorotriethoxysilane, FSi (OC 2 H Five ) Three 0.54 g was dissolved in 10 ml of ethanol and added to 90 ml of water with stirring. The liquid was suspended but allowed to stand for 30 minutes. Thereafter, as a base material, a silicon substrate and a soda lime glass plate were immersed and sealed. It was put in a thermostat kept at 40 ° C. and left for 40 hours. On the other hand, an experiment was also conducted in which the holding temperature was set to 70 ° C. and left for 24 hours. After each standing, the substrate was removed from the solution, washed with water and dried. Regardless of the holding temperature, a thin film was formed on either the silicon substrate or the soda lime glass.
[0048]
As a result of measuring the infrared absorption spectrum of the thin film on silicon, SiO 2 Absorption peculiar to was observed. As a result of ESCA analysis, values of Si: 33 atm%, O: 65 atm%, and F: 2 atm% were obtained. From these results, it was found that a silicon dioxide thin film containing a small amount of fluorine was obtained. As a result of observing the film by SEM observation, it was found that the film thickness was 0.3 μm at a holding temperature of 40 ° C. and 0.2 μm at 70 ° C.
[0049]
(Example 17)
Reagents Trimethoxysilane, HSi (OCH Three ) Three 0.49 g was dissolved in 20 ml of ethanol and added to 80 ml of water with stirring. The liquid was suspended but allowed to stand for 30 minutes. Thereafter, a silicon substrate and a soda lime glass plate were immersed as a base material and sealed. It was put in a thermostat kept at 60 ° C. and left for 40 hours. After standing, the substrate was taken out of the liquid, washed with water and dried. A porous thin film was formed on both silicon and soda lime substrates.
[0050]
As a result of measuring the infrared absorption spectrum of the thin film on silicon, SiO 2 Absorption peculiar to was observed. Further, as a result of analysis by ESCA, values of Si: 35 atm% and O: 65 atm% were obtained. From these results, it was found that a silicon dioxide thin film was obtained. As a result of observing the film by SEM observation, it was found that the film thickness was 0.2 μm.
[0051]
(Example 18)
As a starting solution, methyltrimethoxysilane (CH Three Si (OCH Three ) Three ) In pure water and mixed with stirring for 4 hours, and TiF Four Reagents and pure water were used. While diluting the methyltrimethoxysilane solution with pure water and stirring, there is TiF. Four A liquid having the composition shown in Table 8 was prepared by adding a predetermined amount of and stirring the mixture. These liquids are once depressurized and the gases in the liquids are purged. Then, as a base material, a quartz glass plate and a silicon wafer are immersed in the liquids, and a sealing cover is attached, and they are placed in a constant temperature bath at 60 ° C. For 15 hours. Thereafter, the substrate was taken out, washed with water and dried.
[0052]
A film was formed on the substrate surface, and the film thickness was determined by SEM observation. Further, when the film formed on the silicon wafer-substrate was analyzed by infrared absorption spectrum, absorption based on the Si—O bond and Si—CH Three Absorption due to bonding was observed, and it was found that a silica coating containing a hydrocarbon group was formed. As a result of analysis by ESCA, Si, Ti, O, and C were detected as main components. F was detected in the coating of 1. The results are shown in Table 8. In the table, n. d. Indicates not detected. The film composition was as shown in Table 8, and it was found that Ti was doped.
[0053]
[Table 8]
(Example 19)
TiF Four Reagent as SnF 2 A film was formed in the same manner as in Example 18 except that the reagent was used. A film was formed on the surface of the substrate, and the film pressure was determined by SEM observation. Further, when the film formed on the silicon wafer substrate was analyzed by infrared absorption spectrum, absorption based on the Si—O bond and Si—CH Three Absorption due to bonding was observed, and it was found that a hydrocarbon-containing silica film was formed. As a result of analysis by ESCA, Si, Sn, O, and C were detected as main components. F was detected in the coating of 1. The results are shown in Table 9. In the table, n. d. Indicates not detected. The film composition was as shown in Table 9, and it was found that Sn was doped.
[0055]
[Table 9]
(Example 20)
The films on the quartz glass plates obtained in Examples 18 and 19 were baked at 800 ° C. for 1 hour in the air. As a result of analyzing the obtained film by ESCA, C and F were not detected at all, and only Si, O, and Ti were detected from those obtained by baking the film obtained in Example 18, and obtained in Example 19. From the fired film, only Si, O, and Sn were detected. The molar ratios of the doping elements Ti and Sn to Si were the same as before firing. From this, it was found that the silica film was doped with Ti or Sn and contained no hydrocarbon group.
[0057]
(Example 21)
Vinyltrimethoxysilane CH 2 CHSi (OCH Three ) Three , Trifluoropropyltrimethoxysilane CF Three CH 2 CH 2 Si (OCH Three ) Three , A solution containing 0.03 mol / l vinyltrimethoxysilane and 1.5 mol / l ammonium fluoride using water and ammonium fluoride, and 0.03 mol / l trifluoropropylmethoxysilane and 1.5 mol ammonium fluoride Each solution containing 1 / l was prepared. Each solution was placed in a glass beaker, heated to 60 ° C. with stirring, and held for 15 hours. After holding, the solution was discharged, and it was confirmed that a film was formed on the inner surface of the beaker. As a result of cutting out a part of the beaker and measuring the IR spectrum, it was found that the film was a silica film containing a vinyl group and a silica film containing a trifluoropropyl group.
[0058]
【The invention's effect】
The present invention provides a method for directly forming a silica-based coating in the liquid phase. As a feature of this method, a film can be formed at a low temperature, a large area film can be easily formed, a large amount of film can be formed at a time, a film can be formed on a surface of an arbitrary shape, and a manufacturing apparatus can be simplified. Etc. Therefore, it is an industrially valuable method.
Claims (8)
ＲｎＳｉ（ＯＲ）４−ｎ［１≦ｎ≦２］、
ＦｎＳｉ（ＯＲ）４−ｎ［１≦ｎ≦３］、または
ＨｎＳｉ（ＯＲ）４−ｎ［１≦ｎ≦３］
（ただし、Ｒは炭化水素基、Ｆは弗素、Ｈは水素を示す）。 The method for producing a silica-based film according to claim 2 , wherein the following compound is used as the alkoxysilane having a hydrophobic functional group:
RnSi (OR) 4-n [1 ≦ n ≦ 2],
FnSi (OR) 4-n [1 ≦ n ≦ 3] or HnSi (OR) 4-n [1 ≦ n ≦ 3]
(However, R represents a hydrocarbon group, F represents fluorine, and H represents hydrogen).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09964794A JP3694900B2 (en) | 1993-05-31 | 1994-05-13 | Method for producing silica-based coating |
Applications Claiming Priority (9)
| Application Number | Priority Date | Filing Date | Title |
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| JP12892093 | 1993-05-31 | ||
| JP13046493 | 1993-06-01 | ||
| JP24921893 | 1993-10-05 | ||
| JP5-249218 | 1993-11-26 | ||
| JP5-128920 | 1993-11-26 | ||
| JP29628993 | 1993-11-26 | ||
| JP5-130464 | 1993-11-26 | ||
| JP5-296289 | 1993-11-26 | ||
| JP09964794A JP3694900B2 (en) | 1993-05-31 | 1994-05-13 | Method for producing silica-based coating |
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| JP3694900B2 true JP3694900B2 (en) | 2005-09-14 |
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| JP3760493B2 (en) * | 1995-09-21 | 2006-03-29 | 東亞合成株式会社 | Solid silica derivative and method for producing the same |
| JP3760498B2 (en) * | 1996-01-24 | 2006-03-29 | 東亞合成株式会社 | Si-H bond-containing silica derivative fine particles and method for producing the same |
| JP3887851B2 (en) * | 1996-10-04 | 2007-02-28 | 昭和電工株式会社 | Composition for forming silica film and method for forming silica film |
| US6852299B2 (en) | 2000-04-28 | 2005-02-08 | Mitsui Chemicals, Inc. | Water-repellent porous silica, method for preparation thereof and use thereof |
| KR100981575B1 (en) * | 2006-07-10 | 2010-09-10 | 주식회사 엘지화학 | Antireflective coating composition with excellent stain resistance |
| JP4683021B2 (en) * | 2007-08-02 | 2011-05-11 | トヨタ自動車株式会社 | Catalyst support for forming fuel cell electrode and method for producing polymer electrolyte fuel cell |
| KR102603146B1 (en) * | 2021-07-23 | 2023-11-17 | 한국기계연구원 | Coating method for water repellent surface |
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