JP2005022155A - Antistatic molded object and antistatic coating - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、帯電防止性能に優れた成型体及び帯電防止塗料に関する。
【０００２】
【従来の技術】
近年、半導体製造を中心とする電気電子産業や食品産業、医薬産業等においては、僅かな塵や埃等の異物混入等が品質管理上の問題となるため、工程によっては塵や埃の極めて少ないクリーン環境の中で行われるが、このようなクリーン環境の維持には、塵や埃を吸着する静電気の発生が支障となるため、クリーン環境内で使用する物品には帯電防止性能が要求される。また、電機部品等では静電気による機能破壊等が起こりやすいという問題があるため、同様に帯電防止性能が要求される。
【０００３】
物品、特に合成樹脂成型品に帯電防止性能を付与する方法としては、物品を構成する素材にカーボンブラック、金属粉末、導電性金属酸化物等の導電性フィラー、界面活性剤等を添加する方法や、物品表面に導電性フィラーを含有する帯電防止層や界面活性剤からなる帯電防止層を設ける方法等が挙げられる。しかしながら、上記の各方法にはそれぞれ問題があった。即ち、物品を構成する素材に導電性フィラーを添加する方法では、良好な帯電防止性能を得るためには多量の導電性フィラーを添加しなければならず、結果として、物品の成型性が低下したり、物品が不透明になったり、物品に自由に着色できない等の問題があった。また、物品を構成する素材に界面活性剤を添加する方法では、導電性が低く充分な帯電防止性能が得られない上に、帯電防止性能が雰囲気の湿度の影響を受けやすいという欠点があった。
【０００４】
また、物品表面に界面活性剤からなる帯電防止層を設ける方法では、帯電防止性能が不充分であるうえに、水やアルコールによる洗浄で界面活性剤からなる帯電防止層が消失したり、摩擦等により取れ易く耐久性に欠ける等の問題があった。
【０００５】
一方、物品の表面に導電性フィラーを含有する帯電防止層を設ける方法としては、例えば、導電性金属酸化物系微粒子を含有する帯電防止塗料を物品の表面に塗布する方法が挙げられる。しかし、微小な粒子を多量に含有する塗料はチキソトロピックな性状を示すため、平滑な塗膜の形成を阻害し、透明性が必要な物品への適用には制約があった。即ち、表面平滑性と透明性とを向上させるためには、ロールコーター等を用いて強いせん断力を与えながら塗布する必要があるため、塗布方法が制限されたり、塗布後にバフ研磨（特許文献１参照）や鏡面ホットプレス（特許文献２参照）等の別途の後工程を設けることが必要であった。
【０００６】
また、このような方法は板状やフィルム状の平坦な物品には有効であるが、凹凸があったり、曲面を有していたり、容器状である等の複雑な３次元形状の成型体等においては、ロールコーター等によるせん断を与えながらの塗布やバフ研磨等の後処理が困難で、透明性、表面平滑性、耐久性に優れた帯電防止性成型体は得られていなかった。
【０００７】
一方、上記の様な複雑な形状の帯電防止成型体を製造する方法としては、予め表面に帯電防止層を設けた板を、プレス成型したり、真空成型する等の方法が一般的であるが、表面に帯電防止層を設けた板を成型する際には、変形を受ける部位の帯電防止層が変形に追随できず、帯電防止性能が低下してしまうという問題があった。
【０００８】
【特許文献１】
特公昭６３−３３７７８号公報
【特許文献２】
特公平６−１５０７１号公報
【０００９】
【発明が解決しようとする課題】
本発明は、上記現状に鑑み、帯電防止塗料を基材に塗布するのみで得られ、表面が平滑で基材の透明性や発色を損なうことなく、帯電防止性に優れた帯電防止成型体を提供することを目的とし、特に凹凸を有する三次元形状のような複雑な形状の基材に帯電防止層が形成された帯電防止成型体を提供することを目的とする。
本発明は、また、塗装が容易で後処理を必要とせず、透明性、表面平滑性、帯電防止性に優れた帯電防止性塗料を提供することも目的とする。
【００１０】
【課題を解決するための手段】
本発明は、導電性金属酸化物を含有する帯電防止塗料からなる帯電防止層を基材の表面上に有し、表面抵抗値が１×１０４〜１×１０９ Ω／□であり、且つ、表面粗さ（Ｒａ）が５〜５０ｎｍである帯電防止成型体である。
以下に本発明を詳述する。
【００１１】
本発明の帯電防止成型体は、導電性金属酸化物を含有する帯電防止塗料からなる帯電防止層を基材の表面上に有するものである。
上記帯電防止塗料としては特に限定されないが、例えば、導電性金属酸化物微粒子、バインダー樹脂、及び、有機溶剤を含有する塗料が好適に用いられる。
【００１２】
上記導電性金属酸化物微粒子としては、例えば、アンチモンを含有する導電性酸化錫、インジウム錫酸化物等の酸化錫が挙げられるが、なかでも、アンチモンを含有する導電性酸化錫が好ましい。また、上記導電性金属酸化物微粒子としては、透明微粒子の表面に導電性金属酸化物層が形成された複合微粒子を用いることもできる。このような複合微粒子としては、例えば、硫酸バリウムの微粒子表面にアンチモンを含有する導電性酸化錫からなる層が形成された導電性微粒子が市販されている。
【００１３】
上記帯電防止塗料に添加する導電性金属酸化物微粒子としては、塗料中で微分散させる必要があるため、塗料に添加する前の平均粒子径が１００ｎｍ以下であり、好ましくは５０ｎｍ以下のものが好適に用いられる。上記帯電防止塗料中における導電性金属酸化物微粒子は、平均粒子径が１００ｎｍ以下であり、且つ、粒子径が２００ｎｍ以上のものの含有量が導電性金属酸化物微粒子の総量に対して１０重量％以下となるように分散されている。導電性金属酸化物微粒子の平均粒子径が１００ｎｍを超える場合や、粒子径が２００ｎｍ以上のものの含有量が１０重量％を超える場合には、塗膜の表面が荒れて、均一な厚みを有し表面が平滑な帯電防止層が得られにくい。特に、基材が着色されていたり、透明であったりする場合には、得られた帯電防止層が不透明であると、得られた帯電防止成型体の色は不鮮明になったり、不透明となる。なお、上記帯電防止塗料中における導電性金属酸化物微粒子の平均粒子径は、帯電防止塗料を溶剤で希釈し光散乱法により求められた値であり、１次粒子と凝集体との両方を含む平均粒子径である。また、粒子径が２００ｎｍ以上である導電性金属酸化物微粒子には、１次粒子が複数個凝集した凝集体も含まれる。より好ましい平均粒子径は５０ｎｍ以下であり、粒子径が２００ｎｍ以上のもののより好ましい含有量は５重量％以下である。
【００１４】
上記帯電防止塗料の導電性金属酸化物微粒子含有量は、塗料の固形分中の５０〜８０重量％であることが好ましい。５０重量％未満であると、帯電防止性能が不足することがあり、８０重量％を超えて配合しても、配合量に見合った帯電防止性能は得られず、また、平均粒子径を１００ｎｍ以下となるように分散させるのが困難になる。
【００１５】
上記バインダー樹脂としては特に限定されず、例えば、塩化ビニル系樹脂、ポリエステル樹脂、アクリル樹脂等のラッカータイプの塗料バインダーとして一般的に使われている樹脂や、紫外線硬化樹脂、熱硬化樹脂等の反応性樹脂が挙げられる。
【００１６】
上記有機溶剤としては、上記バインダー樹脂を溶解する溶剤であり、且つ、上記導電性金属酸化物微粒子の分散性を阻害しない溶剤であれば特に限定されず、例えば、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等のケトン類；酢酸エチル、酢酸ブチル等の酢酸エステル類；トルエン、キシレン等の芳香族炭化水素化合物等が挙げられる。これらの溶剤は、バインダー樹脂の種類や塗装性等の要求に応じて適宜選択されれば良く、単独で用いられてもよく、２種以上が併用されてもよい。
【００１７】
上記帯電防止塗料の固形分濃度は、１〜２０重量％であることが好ましい。１重量％未満であると、塗料の付着量を多くする必要があり、塗料が流動し過ぎてタレ等の不具合を生じる。一方、２０重量％を超えると、チキソトロピックな性状が強く現れ、塗膜表面が荒れ、均一な厚みを有し表面が平滑な帯電防止層が得られず、特にスプレー方式で塗装する場合、飛沫痕により塗膜表面に凹凸等が生じ、帯電防止層の透明性が損なわれる。固形分濃度を１〜２０重量％にすることにより、バフ仕上げ等の後処理をしなくとも、透明で表面の平滑な帯電防止層が得られる。より好ましい下限は５重量％であり、より好ましい上限は１０重量％である。なお、上記固形分とは、主に上記バインダー樹脂と上記導電性金属酸化物微粒子とを意味する。
【００１８】
上記帯電防止塗料は、粘度が５〜３０ｃｐｓであることが好ましい。５〜３０ｃｐｓであると、スプレー方式により塗布しやすい。なお、上記粘度は、２０℃において、ローターＮｏ．２、回転数５０ｒｐｍの条件でＢ型粘度計により測定される値である。
このような帯電防止塗料もまた、本発明の１つである。
【００１９】
本発明の帯電防止成型体の帯電防止層は、例えば、上記帯電防止塗料を基材表面に塗布することにより形成される。
上記帯電防止塗料を基材表面に塗布する方法としては特に限定されず、例えば、刷毛を用いる方法、スプレー法、ディッピング法、ロールコート法、バーコード法、ドクターブレード法等が挙げられる。基材が、板状、シート状、フィルム状等の比較的単純な形状を有する場合は、上記のいずれの塗工方法によっても良好な帯電防止層が得られるが、基材が、表面に凹凸があったり、曲面を有していたり、容器状である等の複雑な凹凸を有する三次元形状体である場合には、スプレー法によることが好ましい。スプレー法は基材が複雑な形状であっても、比較的容易に塗膜の厚みを均一にすることができる。このため、スプレー法によれば、均一な厚さの塗膜を得ることができるので、バフ仕上げ等の後処理をしなくとも、帯電防止塗料をスプレー塗布することのみにより、透明で表面が平滑な帯電防止層を形成することができる。
【００２０】
上記帯電防止層の厚みとしては特に限定されないが、塗膜乾燥後の厚みが０．２〜１０μｍであることが好ましい。０．２μｍ未満であると、帯電防止層の表面が基材の表面状態に影響されて平滑性に劣るものとなり、帯電防止性能が不充分となる。一方、１０μｍを超えると、帯電防止層の透明性が低下する。
【００２１】
本発明の帯電防止成型体の基材としては特に限定されず、例えば、ポリエチレン樹脂、ポリプロピレン樹脂等のポリオレフィン系樹脂；塩化ビニル系樹脂、アクリル樹脂、ポリカーボネート樹脂、ポリスチレン樹脂、ポリエチレンテレフタレート等のポリエステル樹脂等の熱可塑性樹脂や、フェノール樹脂、エポキシ樹脂等の熱硬化性樹脂を含む合成樹脂類や、ガラス等の無機物類等からなる成型体が挙げられ、用途に応じて適宜選択されれば良いが、軽量であること、成型性等の点から、合成樹脂類からなる成型体が好ましい。
【００２２】
上記基材は、板状やフィルム状であってもよいが、上記基材が曲面や折れ曲がった部位等の凹凸を有する三次元形状体である場合に、特に本発明が好適に用いられる。
上記基材の成型法としては特に限定されず、例えば、射出成型、真空成型、押出成型、プレス成型等が挙げられる。
【００２３】
本発明の帯電防止成型体は、表面抵抗値が１×１０４〜１×１０９ Ω／□である。１×１０４Ω／□未満であると、帯電防止性能には問題がないが、用途によっては導電性が高すぎて、例えば、半導体デバイスの容器の場合、放電現象が起こってデバイスを破壊する等の不都合があり、一方、１×１０９Ω／□を超えると、帯電防止性能が不充分となる。なお、上記表面抵抗値は、ＪＩＳ Ｋ ６９１１に基づいて求められる値であるが、本発明の帯電防止成型体の形状が複雑な場合は、高抵抗計を用いて電極間の抵抗を測定し、表面抵抗値に換算することにより求められる。
【００２４】
本発明の帯電防止成型体は、表面粗さ（Ｒａ）が５〜５０ｎｍである。５ｎｍ未満であると、表面仕上げ等の後工程が必要となり、５０ｎｍを超えると、帯電防止成型体の透明性が低下したり、平滑な表面が得られない等の問題が生じる。なお、上記表面粗さ（Ｒａ）は、ＪＩＳ Ｂ ０６０１に基づいて求められる算術平均粗さである。
【００２５】
本発明の帯電防止成型体は、透明性が求められる場合には、ヘイズ値が１０％以下であることが好ましい。１０％を超えると、帯電防止成型体の透明性が低下する。より好ましい上限は５％である。本発明の帯電防止成型体のヘイズ値は基材自体のヘイズ値の影響を受けるが、本発明の典型的な実施態様においては、本発明の帯電防止成型体のヘイズ値は基材のヘイズ値に対して３％以内の上昇に抑えられる。なお、上記ヘイズ値は、ＪＩＳ Ｋ ７１０５に基づいて求められる値である。
【００２６】
本発明の帯電防止成型体は、全光線透過率が８４％以上であることが好ましい。８４％未満であると、用途によっては、帯電防止成型体の透明性が充分でないことがある。全光線透過率を８４％以上とするためには、上記基材として、ＰＭＭＡ等のアクリル系樹脂や、ＰＣ等のポリカーボネート系樹脂等の透明樹脂からなる成型体を用いることが好ましい。帯電防止成型体の全光線透過率もヘイズ値と同様に、基材の全光線透過率の影響を受けるが、本発明の典型的な実施態様においては基材の全光線透過率に対して１０％以内の低下に抑えることができる。なお、上記全光線透過率は、上記ヘイズ値と同様に、ＪＩＳ Ｋ ７１０５に基づいて求められる値である。
【００２７】
本発明の帯電防止成型体の用途としては特に限定されないが、例えば、ウェハー容器、フォトマスク容器、半導体等の精密製造装置の扉やカバー、照明カバー等が好適に挙げられる。
【００２８】
従来は、導電性金属酸化物微粒子を分散させた塗料を塗布する場合、特にスプレー方式による場合に、透明で、表面が平滑な塗膜が得られにくいのが一般的である。この理由としては、例えば、次のような事柄が考えられる。
【００２９】
第一の理由は、導電性金属酸化物微粒子の凝集体粒子径が大きいことである。透明な帯電防止塗料には１次粒子の平均粒子径が数十ｎｍ程度の導電性金属酸化物微粒子が用いられるが、上記導電性金属酸化物微粒子を１次粒子にまで分散させるのは非常に困難であり、通常は、多数の１次粒子が凝集した凝集体として存在する。上記凝集体の粒子径が大きいと光の散乱が増加したり塗膜表面に凹凸が生じたりして、透明で平滑な塗膜が得られない。更に、スプレー塗装の場合、飛沫が空中を飛ぶ際に空気と激しく接触し、気化潜熱を奪われたり吸湿したりすることに起因して、導電性金属酸化物微粒子は更に大きな凝集体を生成し、塗膜の透明性や平滑性を損ねてしまう傾向がある。
【００３０】
第二の理由は、スプレー飛沫が基材表面に付着した後、充分に平滑化されずに乾燥固化してしまうために、塗膜表面に凹凸の飛沫痕が残ってしまうためである。塗膜表面に飛沫痕が残りやすいことはスプレー塗装一般に当てはまることであるが、導電性金属酸化物微粒子を多量に含有する帯電防止塗料においてはその傾向が著しい。その理由としては、塗料がチキソトロピック性を有するためと考えられる。
【００３１】
これに対して、本発明においては、帯電防止塗料の固形分濃度を低くし、且つ、帯電防止塗料中の導電性金属酸化物微粒子として、平均粒子径が１００ｎｍ以下で、且つ、粒子径が２００ｎｍ以上のものの含有量が１０重量％以下であるものを使用することにより上記の問題が解消でき、スプレー塗装のみにより、後処理をしなくとも、透明性、表面平滑性に優れた帯電防止層を基材表面上に形成することができる。
【００３２】
【実施例】
以下に実施例を掲げて本発明を更に詳しく説明するが、本発明はこれら実施例のみに限定されるものではない。
【００３３】
＜実施例１＞
〔基材の作製〕
厚さ２ｍｍの透明アクリル板を真空成型法により曲率半径１０ｃｍのお椀形に成型した。成型後の透明アクリル樹脂からなる基材自体のヘイズ値は３％であり、全光線透過率は９１％であった。
【００３４】
〔帯電防止塗料の作製〕
直径０．３ｍｍのジルコニア製ビーズを充填したビーズミルに、シクロヘキサノン６３重量部、塩化ビニル系共重合体（日本ゼオン社製、商品名「ＭＲ−１１０」）１４重量部を入れ、回転数１００ｒｐｍで１０分間運転し、塩化ビニル系共重合体を溶剤中に溶解した。その後、アンチモンドープ酸化錫粉末（三菱マテリアル社製、商品名「Ｔ−１」；１次粒子径２０ｎｍ）２３重量部を、少量づつ添加した。添加後、回転数を２３００ｒｐｍに上げ、４時間攪拌して帯電防止塗料原液を得た。得られた塗料原液をシクロヘキサノンで希釈し、固形分濃度が１０重量％の帯電防止塗料を得た。
【００３５】
〔基材への塗布〕
上記基材に、希釈した塗料をスプレー方式により塗布量が平均４０ｇ／ｍ２となるように塗布し、６０℃で２０分間温風乾燥して帯電防止成型体を得た。
【００３６】
＜実施例２＞
塗料の固形分濃度を３重量％とし、塗布量を１００ｇ／ｍ２としたこと以外は実施例１と同様にして帯電防止成型体を得た。
【００３７】
＜実施例３＞
塩化ビニル系共重合体の配合量を１２重量部とし、アンチモンドープ酸化錫粉末の配合量を２５重量部とし、塗料の固形分濃度を５重量％とし、塗料の塗布量を８０ｇ／ｍ２としたこと以外は実施例１と同様にして帯電防止成型体を得た。
【００３８】
＜実施例４＞
回転数２３００ｒｐｍでの攪拌時間を７時間としたこと以外は実施例１と同様にして帯電防止成型体を得た。
【００３９】
＜比較例１＞
〔帯電防止塗料の作製〕
回転数２３００ｒｐｍでの攪拌時間を３０分間としたこと以外は実施例１と同様にして帯電防止塗料を作製した。
【００４０】
〔基材への塗布〕
実施例１と同様にして帯電防止成型体を作製した後に、後処理としてバフ仕上げを行った。
【００４１】
＜比較例２＞
塗料の固形分濃度を３０重量％としたこと以外は実施例１と同様にして帯電防止成型体を得た。
【００４２】
＜比較例３＞
バフ仕上げを行わなかったこと以外は比較例１と同様にして帯電防止成型体を得た。
【００４３】
〔評価〕
各実施例及び比較例で得られた帯電防止塗料及び帯電防止成型体について下記の評価を行った。結果を表１に示した。
【００４４】
（酸化錫微粒子の粒子径）
帯電防止塗料をメチルエチルケトンにて希釈し、レーザー散乱法による粒度分布計（ＨＯＲＩＢＡ ＬＡ−９１０、堀場製作所社製）にて測定した。
【００４５】
（表面抵抗値）
高抵抗計（ＴＲ−３、東京エレクトロニック社製）を用いて、帯電防止成型体表面の５カ所の抵抗を測定し、表面抵抗値を求め、その範囲を表１に示した。
【００４６】
（表面粗さ（Ｒａ））
表面形状測定器（サーフコム４８０、東京精密社製）を用いて、帯電防止成型体の表面粗さ（Ｒａ）を求めた。
【００４７】
（ヘイズ値、全光線透過率）
帯電防止成型体から５ｃｍ×１０ｃｍ角の試験片をカットし、ヘイズメーター（ＮＤ−１００１ＤＰ、日本電色工業社製）を用いて、帯電防止成型体のヘイズ値及び全光線透過率を測定した。
【００４８】
（塗料の粘度）
２０℃において、ローターＮｏ．２、回転数５０ｒｐｍの条件で、Ｂ型粘度計（Ｂ８Ｈ、東京計器社製）を用いて測定した。
【００４９】
【表１】
【発明の効果】
本発明は、上述の構成よりなるので、帯電防止塗料を基材に塗布するのみで得られ、バフ仕上げ等の後処理を別途要することなく、基材が凹凸を有する複雑な三次元形状を有している場合であっても、帯電防止性、透明性、表面平滑性に優れる帯電防止成型体を提供することができ、得られた帯電防止成型体は、クリーンルーム内等において使用される設備や部品等に好適に使用される。
また、本発明の帯電防止塗料によれば、スプレー法等により基材に塗布するだけで、バフ仕上げ等の煩雑な後処理を要することなく、帯電防止性、透明性、平滑性に優れた塗膜を形成できるので、複雑な形状の成型体等の帯電防止に好適に使用される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molded article and an antistatic paint excellent in antistatic performance.
[0002]
[Prior art]
In recent years, in the electrical / electronic industry, food industry, pharmaceutical industry, etc. centering on semiconductor manufacturing, a slight amount of foreign matter such as dust and dirt has become a problem in quality control. Although it is performed in a clean environment, the maintenance of such a clean environment hinders the generation of static electricity that adsorbs dust and dirt, and therefore, antistatic performance is required for articles used in the clean environment. . In addition, since there is a problem that an electrical component or the like is liable to cause functional breakdown due to static electricity, antistatic performance is similarly required.
[0003]
As a method of imparting antistatic performance to an article, particularly a synthetic resin molded product, a method of adding a conductive filler such as carbon black, metal powder, or conductive metal oxide, a surfactant, or the like to a material constituting the article, And a method of providing an antistatic layer containing a conductive filler or an antistatic layer made of a surfactant on the surface of the article. However, each of the above methods has problems. That is, in the method of adding a conductive filler to the material constituting the article, a large amount of conductive filler must be added in order to obtain good antistatic performance, resulting in a decrease in the moldability of the article. Or the article becomes opaque, or the article cannot be colored freely. In addition, the method of adding a surfactant to the material constituting the article has the disadvantages that the electroconductivity is low and sufficient antistatic performance cannot be obtained, and that the antistatic performance is easily affected by the humidity of the atmosphere. .
[0004]
In addition, in the method of providing an antistatic layer made of a surfactant on the surface of the article, the antistatic performance is insufficient, and the antistatic layer made of the surfactant disappears by washing with water or alcohol, or friction, etc. There was a problem that it was easy to remove and lacked durability.
[0005]
On the other hand, as a method of providing an antistatic layer containing a conductive filler on the surface of an article, for example, a method of applying an antistatic coating containing conductive metal oxide-based fine particles to the surface of the article can be mentioned. However, since a paint containing a large amount of fine particles exhibits thixotropic properties, formation of a smooth coating film is obstructed and application to articles requiring transparency is restricted. That is, in order to improve surface smoothness and transparency, it is necessary to apply a strong shearing force using a roll coater or the like, so that the application method is limited, or buffing is performed after application (Patent Document 1). For example, it is necessary to provide a separate post-process such as a mirror hot press (see Patent Document 2).
[0006]
In addition, such a method is effective for flat articles such as plates and films, but has a complicated three-dimensional shape such as irregularities, curved surfaces, container shapes, etc. However, post-treatment such as coating or buffing while applying shear with a roll coater or the like is difficult, and an antistatic molded article excellent in transparency, surface smoothness, and durability has not been obtained.
[0007]
On the other hand, as a method for producing an antistatic molded body having a complicated shape as described above, methods such as press molding or vacuum molding of a plate provided with an antistatic layer on the surface in advance are generally used. When molding a plate provided with an antistatic layer on the surface, there is a problem that the antistatic layer in the part subjected to deformation cannot follow the deformation and the antistatic performance is lowered.
[0008]
[Patent Document 1]
Japanese Patent Publication No. 63-33778 [Patent Document 2]
Japanese Examined Patent Publication No. 6-15071
[Problems to be solved by the invention]
In view of the above situation, the present invention provides an antistatic molded article that is obtained by simply applying an antistatic coating to a substrate, has a smooth surface, and does not impair the transparency and color development of the substrate. An object of the present invention is to provide an antistatic molded body in which an antistatic layer is formed on a substrate having a complicated shape such as a three-dimensional shape having irregularities.
Another object of the present invention is to provide an antistatic coating that is easy to paint, does not require post-treatment, and has excellent transparency, surface smoothness, and antistatic properties.
[0010]
[Means for Solving the Problems]
The present invention has an antistatic layer made of an antistatic paint containing a conductive metal oxide on the surface of a substrate, has a surface resistance value of 1 × 10 4 to 1 × 10 9 Ω / □, and The antistatic molded body having a surface roughness (Ra) of 5 to 50 nm.
The present invention is described in detail below.
[0011]
The antistatic molded body of the present invention has an antistatic layer made of an antistatic paint containing a conductive metal oxide on the surface of a substrate.
Although it does not specifically limit as said antistatic coating material, For example, the coating material containing electroconductive metal oxide microparticles | fine-particles, binder resin, and an organic solvent is used suitably.
[0012]
The conductive metal oxide fine particles include, for example, conductive tin oxide containing antimony and tin oxide such as indium tin oxide. Among them, conductive tin oxide containing antimony is preferable. As the conductive metal oxide fine particles, composite fine particles in which a conductive metal oxide layer is formed on the surface of transparent fine particles can also be used. As such composite fine particles, for example, conductive fine particles in which a layer made of conductive tin oxide containing antimony is formed on the surface of the fine particles of barium sulfate are commercially available.
[0013]
The conductive metal oxide fine particles added to the antistatic paint need to be finely dispersed in the paint, so that the average particle diameter before adding to the paint is 100 nm or less, preferably 50 nm or less. Used for. The conductive metal oxide fine particles in the antistatic coating have an average particle size of 100 nm or less, and the content of particles having a particle size of 200 nm or more is 10% by weight or less based on the total amount of the conductive metal oxide fine particles. It is distributed to become. When the average particle diameter of the conductive metal oxide fine particles exceeds 100 nm or the content of particles having a particle diameter of 200 nm or more exceeds 10% by weight, the surface of the coating film is rough and has a uniform thickness. It is difficult to obtain an antistatic layer having a smooth surface. In particular, when the substrate is colored or transparent, if the obtained antistatic layer is opaque, the color of the obtained antistatic molded product becomes unclear or opaque. The average particle diameter of the conductive metal oxide fine particles in the antistatic coating is a value obtained by diluting the antistatic coating with a solvent and obtained by a light scattering method, and includes both primary particles and aggregates. Average particle size. In addition, the conductive metal oxide fine particles having a particle diameter of 200 nm or more include aggregates in which a plurality of primary particles are aggregated. A more preferable average particle diameter is 50 nm or less, and a more preferable content of those having a particle diameter of 200 nm or more is 5% by weight or less.
[0014]
The content of the conductive metal oxide fine particles in the antistatic coating is preferably 50 to 80% by weight in the solid content of the coating. If it is less than 50% by weight, the antistatic performance may be insufficient, and even if it exceeds 80% by weight, the antistatic performance corresponding to the blending amount cannot be obtained, and the average particle size is 100 nm or less. It becomes difficult to disperse so that
[0015]
The binder resin is not particularly limited. For example, a resin generally used as a lacquer type paint binder such as a vinyl chloride resin, a polyester resin, an acrylic resin, a reaction of an ultraviolet curable resin, a thermosetting resin, or the like. Resin.
[0016]
The organic solvent is not particularly limited as long as it is a solvent that dissolves the binder resin and does not inhibit the dispersibility of the conductive metal oxide fine particles. For example, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketones; acetates such as ethyl acetate and butyl acetate; aromatic hydrocarbon compounds such as toluene and xylene. These solvents may be appropriately selected according to requirements such as the type of binder resin and paintability, and may be used alone or in combination of two or more.
[0017]
The solid content concentration of the antistatic paint is preferably 1 to 20% by weight. If the amount is less than 1% by weight, it is necessary to increase the amount of the paint applied, and the paint will flow too much, causing problems such as sagging. On the other hand, when it exceeds 20% by weight, thixotropic properties appear strongly, the surface of the coating film becomes rough, and an antistatic layer having a uniform thickness and a smooth surface cannot be obtained. Unevenness or the like occurs on the surface of the coating film due to the marks, and the transparency of the antistatic layer is impaired. By setting the solid content concentration to 1 to 20% by weight, a transparent and smooth antistatic layer can be obtained without post-treatment such as buffing. A more preferred lower limit is 5% by weight, and a more preferred upper limit is 10% by weight. The solid content mainly means the binder resin and the conductive metal oxide fine particles.
[0018]
The antistatic paint preferably has a viscosity of 5 to 30 cps. When it is 5 to 30 cps, it is easy to apply by a spray method. The viscosity is 20 ° C. at rotor No. 2. It is a value measured by a B-type viscometer under the condition of a rotational speed of 50 rpm.
Such an antistatic coating is also one aspect of the present invention.
[0019]
The antistatic layer of the antistatic molded article of the present invention is formed, for example, by applying the above antistatic coating to the substrate surface.
The method for applying the antistatic coating to the substrate surface is not particularly limited, and examples thereof include a method using a brush, a spray method, a dipping method, a roll coating method, a barcode method, a doctor blade method, and the like. When the substrate has a relatively simple shape such as a plate shape, a sheet shape, or a film shape, a good antistatic layer can be obtained by any of the above coating methods. In the case of a three-dimensional shape having complicated irregularities such as a curved surface, a curved surface, or a container shape, it is preferable to use a spray method. In the spray method, even if the substrate has a complicated shape, the thickness of the coating film can be made relatively easy. Therefore, according to the spray method, a coating film having a uniform thickness can be obtained, so that a transparent and smooth surface can be obtained only by spraying an antistatic paint without performing post-treatment such as buffing. A simple antistatic layer can be formed.
[0020]
Although it does not specifically limit as thickness of the said antistatic layer, It is preferable that the thickness after coating-film drying is 0.2-10 micrometers. When the thickness is less than 0.2 μm, the surface of the antistatic layer is affected by the surface state of the base material, resulting in poor smoothness and insufficient antistatic performance. On the other hand, when it exceeds 10 μm, the transparency of the antistatic layer is lowered.
[0021]
The base material of the antistatic molded body of the present invention is not particularly limited, and examples thereof include polyolefin resins such as polyethylene resins and polypropylene resins; polyester resins such as vinyl chloride resins, acrylic resins, polycarbonate resins, polystyrene resins and polyethylene terephthalates. Molded bodies made of thermoplastic resins such as synthetic resins, thermosetting resins such as phenolic resins and epoxy resins, and inorganic materials such as glass, etc. may be selected as appropriate depending on the application. From the viewpoint of light weight and moldability, a molded body made of synthetic resins is preferable.
[0022]
The substrate may be in the form of a plate or a film, but the present invention is particularly suitably used when the substrate is a three-dimensional shape having irregularities such as a curved surface or a bent portion.
It does not specifically limit as a shaping | molding method of the said base material, For example, injection molding, vacuum molding, extrusion molding, press molding, etc. are mentioned.
[0023]
The antistatic molded article of the present invention has a surface resistance value of 1 × 10 4 to 1 × 10 9 Ω / □. If it is less than 1 × 10 4 Ω / □, there is no problem in antistatic performance, but depending on the application, the conductivity is too high. For example, in the case of a semiconductor device container, a discharge phenomenon occurs and the device is destroyed. On the other hand, if it exceeds 1 × 10 9 Ω / □, the antistatic performance becomes insufficient. In addition, although the said surface resistance value is a value calculated | required based on JISK6911, when the shape of the antistatic molding of this invention is complicated, the resistance between electrodes is measured using a high resistance meter, It is determined by converting to a surface resistance value.
[0024]
The antistatic molded article of the present invention has a surface roughness (Ra) of 5 to 50 nm. If the thickness is less than 5 nm, a post-process such as a surface finish is required. If the thickness exceeds 50 nm, problems arise such that the transparency of the antistatic molded article is lowered or a smooth surface cannot be obtained. In addition, the said surface roughness (Ra) is arithmetic mean roughness calculated | required based on JISB0601.
[0025]
The antistatic molded article of the present invention preferably has a haze value of 10% or less when transparency is required. If it exceeds 10%, the transparency of the antistatic molded article is lowered. A more preferred upper limit is 5%. Although the haze value of the antistatic molded body of the present invention is affected by the haze value of the base material itself, in a typical embodiment of the present invention, the haze value of the antistatic molded body of the present invention is the haze value of the base material. Against the rise of 3%. In addition, the said haze value is a value calculated | required based on JISK7105.
[0026]
The antistatic molded article of the present invention preferably has a total light transmittance of 84% or more. If it is less than 84%, the transparency of the antistatic molded body may not be sufficient depending on the application. In order to set the total light transmittance to 84% or more, it is preferable to use a molded body made of a transparent resin such as an acrylic resin such as PMMA or a polycarbonate resin such as PC as the base material. Similar to the haze value, the total light transmittance of the antistatic molded body is also affected by the total light transmittance of the base material. In a typical embodiment of the present invention, the total light transmittance is 10% of the total light transmittance of the base material. % Can be suppressed to a decrease of within%. In addition, the said total light transmittance is a value calculated | required based on JISK7105 similarly to the said haze value.
[0027]
Although it does not specifically limit as a use of the antistatic molding of this invention, For example, a door, a cover, a lighting cover, etc. of precision manufacturing apparatuses, such as a wafer container, a photomask container, and a semiconductor, are mentioned suitably.
[0028]
Conventionally, when a coating material in which conductive metal oxide fine particles are dispersed is applied, particularly when using a spray method, it is generally difficult to obtain a transparent and smooth coating film. As this reason, for example, the following matters can be considered.
[0029]
The first reason is that the aggregate particle diameter of the conductive metal oxide fine particles is large. Conductive metal oxide fine particles having an average primary particle diameter of about several tens of nanometers are used for transparent antistatic paints. However, it is extremely difficult to disperse the conductive metal oxide fine particles to primary particles. It is difficult and usually exists as an aggregate in which many primary particles are aggregated. If the particle size of the aggregate is large, light scattering increases or irregularities occur on the surface of the coating film, and a transparent and smooth coating film cannot be obtained. Furthermore, in the case of spray coating, the conductive metal oxide fine particles form larger aggregates due to the intense contact with air when the droplets fly through the air, depriving the latent heat of vaporization and absorbing moisture. The transparency and smoothness of the coating film tend to be impaired.
[0030]
The second reason is that after spray droplets adhere to the surface of the substrate, they are dried and solidified without being sufficiently smoothed, so that uneven droplet marks remain on the coating film surface. The fact that splash marks tend to remain on the surface of the coating film is generally applicable to spray coating, but the tendency is remarkable in antistatic coatings containing a large amount of conductive metal oxide fine particles. The reason is considered that the paint has thixotropic properties.
[0031]
In contrast, in the present invention, the solid content concentration of the antistatic paint is lowered, and the conductive metal oxide fine particles in the antistatic paint have an average particle diameter of 100 nm or less and a particle diameter of 200 nm. By using a material having a content of 10% by weight or less, the above-mentioned problems can be solved, and an antistatic layer excellent in transparency and surface smoothness can be obtained only by spray coating without any post-treatment. It can be formed on the substrate surface.
[0032]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
[0033]
<Example 1>
[Preparation of substrate]
A transparent acrylic plate having a thickness of 2 mm was molded into a bowl shape having a radius of curvature of 10 cm by vacuum molding. The base material itself made of a transparent acrylic resin after molding had a haze value of 3% and a total light transmittance of 91%.
[0034]
[Preparation of antistatic paint]
A bead mill filled with zirconia beads having a diameter of 0.3 mm is charged with 63 parts by weight of cyclohexanone and 14 parts by weight of a vinyl chloride copolymer (trade name “MR-110”, manufactured by Nippon Zeon Co., Ltd.). It was operated for a minute, and the vinyl chloride copolymer was dissolved in the solvent. Thereafter, 23 parts by weight of antimony-doped tin oxide powder (manufactured by Mitsubishi Materials Corporation, trade name “T-1”; primary particle diameter 20 nm) was added in small amounts. After the addition, the number of revolutions was increased to 2300 rpm, and the mixture was stirred for 4 hours to obtain an antistatic paint stock solution. The obtained paint stock solution was diluted with cyclohexanone to obtain an antistatic paint having a solid concentration of 10% by weight.
[0035]
[Application to base material]
The diluted coating material was applied to the substrate by a spray method so that the coating amount was 40 g / m 2 on average, and dried with warm air at 60 ° C. for 20 minutes to obtain an antistatic molded body.
[0036]
<Example 2>
An antistatic molded body was obtained in the same manner as in Example 1 except that the solid content concentration of the paint was 3% by weight and the coating amount was 100 g / m 2 .
[0037]
<Example 3>
The blending amount of the vinyl chloride copolymer is 12 parts by weight, the blending amount of the antimony-doped tin oxide powder is 25 parts by weight, the solid content concentration of the coating is 5% by weight, and the coating amount of the coating is 80 g / m 2 . Except that, an antistatic molded body was obtained in the same manner as in Example 1.
[0038]
<Example 4>
An antistatic molded body was obtained in the same manner as in Example 1 except that the stirring time at 2300 rpm was 7 hours.
[0039]
<Comparative Example 1>
[Preparation of antistatic paint]
An antistatic paint was prepared in the same manner as in Example 1 except that the stirring time at a rotational speed of 2300 rpm was 30 minutes.
[0040]
[Application to base material]
After producing an antistatic molded body in the same manner as in Example 1, buffing was performed as a post-treatment.
[0041]
<Comparative example 2>
An antistatic molded body was obtained in the same manner as in Example 1 except that the solid content concentration of the paint was 30% by weight.
[0042]
<Comparative Example 3>
An antistatic molded body was obtained in the same manner as in Comparative Example 1 except that buffing was not performed.
[0043]
[Evaluation]
The following evaluation was performed about the antistatic coating material and antistatic molding which were obtained by each Example and the comparative example. The results are shown in Table 1.
[0044]
(Particle diameter of tin oxide fine particles)
The antistatic paint was diluted with methyl ethyl ketone and measured with a particle size distribution meter (HORIBA LA-910, manufactured by Horiba, Ltd.) by a laser scattering method.
[0045]
(Surface resistance value)
Using a high resistance meter (TR-3, manufactured by Tokyo Electronic Co., Ltd.), the resistance at five locations on the surface of the antistatic molded body was measured to determine the surface resistance value. The range is shown in Table 1.
[0046]
(Surface roughness (Ra))
The surface roughness (Ra) of the antistatic molded body was determined using a surface shape measuring instrument (Surfcom 480, manufactured by Tokyo Seimitsu Co., Ltd.).
[0047]
(Haze value, total light transmittance)
A 5 cm × 10 cm square test piece was cut from the antistatic molded body, and the haze value and total light transmittance of the antistatic molded body were measured using a haze meter (ND-1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.).
[0048]
(Viscosity of paint)
At 20 ° C., rotor no. 2. Measurement was performed using a B-type viscometer (B8H, manufactured by Tokyo Keiki Co., Ltd.) under the condition of a rotation speed of 50 rpm.
[0049]
[Table 1]
【The invention's effect】
Since the present invention has the above-described configuration, it can be obtained only by applying an antistatic coating to the base material, and the base material has a complicated three-dimensional shape with unevenness without requiring post-treatment such as buffing. The antistatic molded body having excellent antistatic properties, transparency, and surface smoothness can be provided even when the antistatic molded body is used. It is suitably used for parts and the like.
Further, according to the antistatic coating material of the present invention, the coating material is excellent in antistatic property, transparency, and smoothness without applying a complicated post-treatment such as buffing only by applying to the substrate by a spray method or the like. Since a film can be formed, it is suitably used for preventing charging of a molded article having a complicated shape.
Claims (10)
前記導電性金属酸化物微粒子は、平均粒子径が１００ｎｍ以下で、且つ、粒子径が２００ｎｍ以上のものの含有量が１０重量％以下である
ことを特徴とする請求項１、２、３、４、５又は６記載の帯電防止成型体。The antistatic coating contains conductive metal oxide fine particles, a binder resin, and an organic solvent, has a solid content concentration of 1 to 20% by weight, and the conductive metal oxide fine particle content of the solid content is 50 to 50%. A paint that is 80% by weight,
The conductive metal oxide fine particles have an average particle size of 100 nm or less and a content of particles having a particle size of 200 nm or more is 10% by weight or less. The antistatic molded body according to 5 or 6.
固形分濃度が１〜２０重量％で、前記固形分の前記導電性金属酸化物微粒子含有量が５０〜８０重量％であり、
前記導電性金属酸化物微粒子は、平均粒子径が１００ｎｍ以下で、且つ、粒子径が２００ｎｍ以上のものの含有量が１０重量％以下である
ことを特徴とする帯電防止塗料。An antistatic paint containing conductive metal oxide fine particles, a binder resin, and an organic solvent,
The solid content concentration is 1 to 20% by weight, and the conductive metal oxide fine particle content of the solid content is 50 to 80% by weight,
The conductive metal oxide fine particles have an average particle size of 100 nm or less and a content of particles having a particle size of 200 nm or more is 10% by weight or less.
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| JP2003188380A JP4388768B2 (en) | 2003-06-30 | 2003-06-30 | Antistatic molded body |
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| JP2014072399A (en) * | 2012-09-28 | 2014-04-21 | Shin Etsu Chem Co Ltd | Cleaning method of storage container of precision substrate and manufacturing method of storage container |
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| JP2014072399A (en) * | 2012-09-28 | 2014-04-21 | Shin Etsu Chem Co Ltd | Cleaning method of storage container of precision substrate and manufacturing method of storage container |
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