JP3815226B2

JP3815226B2 - Polishing cloth

Info

Publication number: JP3815226B2
Application number: JP2001023472A
Authority: JP
Inventors: 武雄松名瀬; 幸二渡辺; 康二高階
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2001-01-31
Filing date: 2001-01-31
Publication date: 2006-08-30
Anticipated expiration: 2021-01-31
Also published as: JP2002224945A

Description

【０００１】
【発明の属する技術分野】
本発明は、記録メディアや集積回路基板の仕上げ用に用いられる高精密研磨用の研磨布に関する。さらに詳しくは、記録メディアの中でハードディスクのテキスチャリング用研磨布、ハードディスクの２次ポリッシュ用研磨布、集積回路基盤や精密機器などの仕上げ用研磨布に関する。
【０００２】
【従来の技術】
磁気ディスク等の記録媒体や集積回路基板（以下、被研磨物という）は、近年めざましい技術革新により高容量化、高記憶密度化の要求が高まり、このため各種基板面加工の高精度化が要求されている。このため、極細繊維を使用した研磨布が特開平６−２９５４３２号公報で開示され、直径５μｍ（約０．２５ｔｅｘ相当）以下の極細繊維を使用したテープ状の研磨布として開示されている。また、特開平１０−１８８２７２号公報では、同様の思想で０．１ｄｔｅｘ以下の極細繊維の織布、不織布、植毛、編組物のテープを用いる方法が開示されている。また、このような精密研磨方法として、被研磨物を平面の状態と垂直の状態で研磨する方法がある。水平な方法ではテーブル盤にシート状の研磨布を固定し、砥粒溶液を分散させながら被研磨物の研磨面を水平にして研磨し、垂直な場合では研磨装置に被研磨物表面を垂直方向にして取付け、砥粒スラリーを含浸した研磨布を供給し、ニップローラで加圧しながら被研磨物面を研磨する。これらの精密研磨方法による表面の加工技術水準は日進月歩で向上し、現在、表面の平均粗さは、１０Å以下の水準に達している。今後更に７Å以下のような高精度に安定して研磨可能な技術が期待され、この技術の核になる高精度な研磨布が求められている。
【０００３】
従来の極細繊維を含む研磨布（以下、従来の研磨布という）のように、極細繊維を使用しているだけでは限界に達しており、７Å以下の精度に対応可能な研磨布は困難であると考えられていた。このため、砥粒の大きさだけを非常に細かくする方法も検討されているが、砥粒だけを微細化しても、従来の研磨布を使用した場合、その微細な砥粒を十分に分散したり、保持したりできないので、微細な砥粒は凝集し易くかえって研磨精度を低下させるもので、安定した精度を得ることは非常に困難であった。また、初期で研磨できても、安定性が悪く短時間で研磨精度や研磨速度が低下しやすいという問題があった。
【０００４】
【発明が解決しようとする課題】
本発明は、被研磨物の表面を高精度に研磨可能な研磨布を提供せんとするものである。
【０００５】
【課題を解決するための手段】
本発明は、かかる課題を解決するため、次の構成を有する。すなわち、本発明の研磨布は、繊度０．３ｄｔｅｘ以下の極細合成繊維を少なくとも表面に含む研磨布であって、該繊維に対して−ＯＨ、−ＣＯＯＨ、−ＣＯＮＨ−、−ＳＯ₃の親水基を少なくとも１種以上含有する化合物が固着または共重合又はグラフト重合され、該繊維の親水化度が６０以上であることを特徴とするものである。
【０００６】
【発明の実施の形態】
本発明の研磨布の形態としては、特に限定されないが、極細繊維を少なくとも表面に含む布帛であればよく、不織布、極細繊維にエラストマーを含浸させるか接着させる複合材、織物、シート状、紙などを用いることができるが、研磨布の表面形態安定性の上で、不織布、複合材、織物の形態が好ましい。この形態の種類は研磨目的によって適宜選択される。
【０００７】
本発明において、０．３ｄｔｅｘ以下の極細繊維は例えば高分子刊行会１９９２年発行の「最新紡糸技術」で示唆される多島型（高分子配列体）、海島型、剥離型、多層型もしくはそれに類した方法でまず２成分からなる複合繊維を作製し、かかる複合繊維の一成分を溶解除去するか揉みや熱ショックで物理的に２成分間を剥離することによって目標とする０．３ｄｔｅｘ以下の極細繊維を得ることができる。この極細繊維に適用可能なポリマーは、ポリエステル系、ポリアミド、ポリフェニレンスルフィド系、ポリオレフィン系などの高分子から選択して用いることができるが、特にポリエステル系、ポリアミド系が均一な繊維径の極細繊維を得る点で好ましい。
【０００８】
本発明における研磨布用織物は、紡糸された極細繊維を通常の織機で織物にされ、研磨布用基材として用いる。
【０００９】
本発明における研磨布用不織布は、極細繊維（島成分）を含有したトウ状複合繊維に巻縮をかけ、ステープル状に切断し、乾式や湿式の方法でシート化する。更に必要に応じ、ニードルパンチやウォータージェットパンチなどで繊維を絡合させ不織布の構造とする。このようにして得られた複合繊維シートから溶媒で海成分を除去するか物理的な方法で割繊し、極細繊維からなる不織布を得ることができる。更に、接着成分を添加し、繊維間の絡合強力を向上することができる。不織布には接着成分を添加することが好ましいが、１０ｗｔ％以下添加することがより好ましく、５ｗｔ％以下添加することがさらに好ましい。
【００１０】
また本発明の研磨布の形態は、エラストマー高分子成分を極細繊維に含浸することによって得ることができる。エラストマー高分子成分としては、軟質系やゴム系高分子が好ましく、ウレタン系、シリコーン系、アクリル系、ＰＶＡ高分子であることがより好ましい。本発明において、エラストマー高分子成分は、研磨時の砥粒の保持、表面凹凸や振動吸収のためのクッション、繊維形態保持などの役目をするものである。複合繊維中の海成分のポリマーをアルカリで溶解する場合は、耐アルカリ性のエラストマーが好ましく、加工性やクッション性の観点からはウレタン系、ゴム系高分子エラストマーが好ましい。研磨時のクッション性は、研磨精度上重要で、繊維とエラストマーの割合や空隙率により、研磨精度や研磨目的によって適宜調節される。本発明において、エラストマー成分の含有量は、成型上１５〜８０ｗｔ％が好ましく、含有量によって研磨布の表面状態、空隙率、クッション性、硬度、強度などを調節することができる。本発明において研磨布の厚さは、製造時の加工し易さや研磨時の強度、耐摩耗性、吸水性、クッション性などの点から３ｍｍ以下が好ましく、１．０ｍｍ以下がより好ましい。エラストマー含浸基材を不織布だけでなく、織物、その他基材の親水化研磨布にも適用可能である。
【００１１】
本発明において、不織布あるいは複合材に、表面の起毛繊維を揃えるため、起毛加工やバフ加工を行うのが好ましい。起毛加工やバフ加工を行うことによって、表面の極細繊維は揃えられ、起毛繊維にネップ（団子状態）が発生しなくなり、長さも均一化される。この起毛繊維長は、団子状を避けるため０．５ｍｍ以下が好ましく、０．２ｍｍ以下がより好ましい。
【００１２】
また、本発明の研磨布の嵩密度は、０．２〜０．６ｇ／ｃｍ³が好ましく、更に、表面高精度面から０．３０〜０．４５の高密度であることがより好ましい。嵩密度は繊維の嵩密度、エラストマーの添加量、加工工程中のプレス条件などによって調節される。また、研磨布表面の平面性、高密度化、表面繊維の形態セット性向上などの点から、研磨布表面にカレンダー加工することが好ましい。
【００１３】
また、エラスマー樹脂は砥粒の分散性、表面繊維の親水性向を向上するためにも多孔性のものが好ましい。
【００１４】
本発明の親水化繊維は、高精度な研磨をするため、均一に親水化処理することが必要であり、このため、繊維内に親水成分が０．０１ｗｔ％以上３０ｗｔ％以下含まれることが必要である。０．１ｗｔ％以上であればより好ましい。また、３０ｗｔ％より多く含むと、表面の滑性、形態安定性が悪化するので好ましくない。
【００１５】
親水成分として、−ＯＨ、−ＣＯＯＨ、−ＣＯＮＨ−、−ＳＯ₃などの親水基を含有する化合物やその誘導体が好ましい。なかでも、アクリル酸系、グリコール系、ＰＶＡ系、セルロース系、シリコーン系、ウレタン系、親水基含有エステル系などが好ましい。親水成分の繊維への添加方法として、該成分の化学的な繊維へのグラフト重合、物理的な親水性化合物微粒子の繊維へのブレンドや繊維表面への吸着や固着などを用いることができる。繊維の親水化の具体的な方法には次のような各種方法を用いることができ、目的によって単独で用いたり、あるいは併用して用いることも可能である。
（Ａ）繊維表面に親水性分子をグラフト化する方法
（Ｂ）繊維高分子自身に親水性成分を共重合する方法
（Ｃ）繊維高分子自身に親水性高分子や無機物を配合する方法
（Ｄ）繊維表面をプラズマ放電やコロナ放電加工する方法
（Ｅ）繊維表面に親水性高分子を吸着（固着）する方法
（Ｆ）繊維を溶媒性または膨潤性溶媒性で処理する方法
例えば、（Ａ）法については、親水性ビニールモノマーをポリエステル繊維にグラフト化する方法が特開平６−１５８５４３号公報、また、親水性アクリル酸をポリアミド繊維にグラフト化する方法が特公昭６０−３４９７９号公報に開示されている。（Ｃ）法については、親水性ポリオキシアルキレングリコールや無機イオン性化合物などの配合による方法が特開昭５３−８０４９７号公報、特開昭６０−３９４１３号公報、特開平９−１３２２９号公報に開示されている。（Ｅ）法については、親水性のポリオールが繊維表面に吸着する方法が特開平６−１１５０５号公報に開示されている。
（Ｆ）法はフェノール、塩化メチレン、ベンジルアルコールなど溶媒性または膨潤性水溶液で処理する方法である。磁気記憶ディスクや精密電子部品用研磨布の繊維を親水化する場合は、金属イオンを含む化合物の使用を避けることが好ましい。
【００１６】
親水化は、加工段階も、親水成分の繊維成分ポリマーへの共重合法や添加法、紡糸時の親水成分の添加、紡糸で得られた繊維の親水化、織物、不織布、複合材状態での繊維表面の親水化などの方法があるが、研磨布の使用目的によって選ぶことができる。
【００１７】
以下、本発明において用いる親水化を処理が容易な（Ａ）法のグラフト化法により説明するが、この方法に限定されるものでなく、（Ｂ）〜（Ｆ）法の親水化を用いることももちろん可能である。
【００１８】
本発明者らは、表面の状態に影響を与える、従来の研磨布に使用されてきた極細合成繊維の親水性について検討した。ポリエステル繊維やポリアミド繊維の通常太さの２ｄｔｅｘ以上の場合、各々の親水化度は５や１０程度と低く親水性よりも疎水的である。（該親水性の定義は、後述実施例の評価方法で詳述するが、親水化度（α）で評価する。親水性が大な研磨布は、砥粒との親和性、分散、凝集の防止効果が向上し、砥粒の把持力や研磨屑除去能が向上する）
従来のポリエステル、ポリアミド繊維などの極細繊維も、０．２、０．０２ｄｔｅｘに極細化すると、親水化度が数１０程度まで若干向上するが十分な親水性が得られない。また、０．０２ｄｔｅｘ以下のような極細繊維は、均一な繊維を安定して製造できないだけでなく、表面積が大きくなりすぎて返って研磨布表面の繊維が収束し、見かけ上繊維が太くなり、砥粒の分散性、研磨精度が低下し易くなり、更に、被研磨物表面に傷（スクラッチ）が発生し、安定な研磨が困難である。繊維の極細化だけの手段では、今後の高精度な研磨が非常に困難になる。
【００１９】
そこで、本発明者らは、極細繊維の親水化を研磨布に適用し、特に研磨布表面の改善を図ることにした。
【００２０】
Ａ法のグラフト化によるポリエステル繊維、ポリアミド繊維の親水化の効果をみるため、繊度０．０２ｔｅｘの繊維を使用し、かつ繊維状態（かせ枠巻状態）で親水性成分をグラフト化処理した実施例を表１に示す。研磨布用の繊維の親水化度は、６０以上であることが必要で、１００以上が好ましい。また、親水化度の条件は親水化によって繊維が柔軟化し形態が不安定になるので、１０００以下が好ましく、５００以下がより好ましい。
【００２１】
親水化度の評価用研磨テープを後述する実施例６〜１５のように作製し、その親水化条件を表２に示した。本実施例ではアクリル酸のグラフト重合法で親水化を行い、親水性ポリエチレン系グリコールの吸着法による親水化も行った。また、織物、不織布、複合材（以下、３者全体を単に加工布という）に加工後、親水性化処理を行うことが形態安定化には好ましい。フィラメント状の繊維と加工布中の繊維では、親水化度が異なり、不織布、織物はフィラメントよりもやや良好であり、複合材はやや悪くなる。これは水分保持の形態的な影響や樹脂成分の影響が考えられる。後述する実施例１〜５と実施例６〜１５のフィラメントと加工布（繊維のタイプ、形態が同じ物どうしの比較）でも、比較例同様、不織布、織物はフィラメントよりもやや良好であり、複合材はやや悪くなる。しかし、各加工布の「表面の繊維」の親水化度は、このような加工布の形態にあまり影響されず、フィラメントの親水化度に近いものと考えられる。
【００２２】
次に、後述する実施例６〜１５、比較例４〜８で得られた研磨布を使用し、研磨性を後述研磨製の評価法で評価した。その親水性研磨布の研磨精度Ｒａ１、未親水性研磨布の研磨精度Ｒａ２を表３に示した。親水化研磨布の効果は、Ｒａ１とＲａ２との研磨精度差△Ｒａと研磨時被研磨物であるハードディスク用サブトレートの表面のスクラッチ傷数とスクラッチ減少数で現わされる。（該スクラッチ数は後述実施例で定義するが、研磨評価３０枚中でスクラッチが発生した枚数と傷の点数で評価する）
表３の実施例６〜１５に示すように、親水化研磨布の親水効果△Ｒａ（効果率）は実施例全体として１．２（１０％）〜２．９（３７％）と従来の研磨布に比較し、高精度化を可能にした。更に、親水化研磨布は、表３のスクラッチ数も未親水化研磨布に比べ、約半減し、安定した研磨が可能になった。
【００２３】
また実施例６〜１５の１０例中、表面粗さＲａ１が目標７Å以下になった例は６例と多くの例で達成できた。本発明の方法の親水化によって、安定で高精度な研磨が可能になっただけでなく、親水化度の調節によって、目的に応じた高精度用研磨布を作製できる。研磨布の親水化には、研磨布に含まれる極細繊維の親水化度が、６０以上が必要で、１００以上が好ましい。
【００２４】
親水化の効果は、研磨評価結果では加工状態（不織布、複合材、織物）の影響をあまり受けないが、これは研磨布全体の親水化の効果よりも研磨布表面の親水化が十分であれば高精度化の効果があることを示している。しかし、親水化（グラフト化）工程で、研磨布は柔軟化し形態保持性が低下するため、複合材が形態保持性の点では好ましい。不織布、織物の場合、接着剤の添加や固定高密度（目付）化が好ましい。親水化したどの加工研磨布も形態安定性に欠けるので、必要に応じてバッキング材としてフィルムや非親水性不織布と複合することが好ましく、基材をバッキング加工後、親水加工することが形態安定化に好ましい。
【００２５】
また、実施例１６〜２５のごとく、各加工布とも親水化度（アクリル酸濃度）が高い方が、表面精度Ｒａ１が低く、親水効果△Ｒａも大きく、高精度な研磨布には好ましく、スクラッチの発生数も少なくなり、高精度でも安定した研磨が可能になる。例えば、実施例２２の親水化度１７６の複合材タイプでは、表面粗さＲａ１が５．６Åと高精度になり、親水効率△Ｒａも２．９Åで親水効果率は３７％改善される。また、該実施例のスクラッチの発生数も未親水化研磨布の１１に比較し、５と少なく、半数以下の発生率に改善される。しかし、あまり高親水化すると研磨レート（単位時間当たりの研磨量）が小さくなるので、研磨目的によって、適切な親水化度を制御するのが好ましい。
【００２６】
親水化された不織布、織物においても複合材と同様に、高親水化度の研磨布の方が、各々実施例１６〜１９、２３，２４のごとく、未親水化研磨布に比較し高精度な研磨が可能で、スクラッチの発生数も少ない。
【００２７】
表３の実施例２０、２１のごとく、同じ複合材であっても親水化（グラフト条件同じ）が、不織布時に親水化した方が複合材の親水化よりもより好ましい。
【００２８】
実施例２１は、ウレタンを先に含浸した複合材を作製後、該基材を親水化（実施例１１）した複合材で、その親水化度は１０４である。実施例２０は、不織布時に親水化（実施例１７）後不織布にウレタンを含浸した複合材で、その親水化度は１２３（表２実施例１０）と親水化し易く、親水化の均一性も大である。また、表３の実施例２０、２１のように、研磨性は、不織布時の親水化複合材の方（実施例２０）が、複合材時の親水化（実施例２１）よりも、高精度（Ｒａ１：５．８Å、△Ｒａ：２．７Å）でスクラッチ発生数も４と非常に少なく好ましい。
【００２９】
実施例１５は、アクリル酸グラフト重合法でなく、ポリエステル繊維に親水性のエチレングリコール（ＰＥＧ）とポリエステル系高分子を共重合した高分子を繊維表面に吸着する方法で「複合材」を親水化した方法である。この実施条件では８０程度の親水化度があり、他のアクリル酸に比較しこの条件ではやや親水効果が低いが親水効果がある。また、実施例２５のごとく、その親水化度によって高精度で（Ｒａ１：７．８Å、△Ｒａ：１．３Å）でスクラッチ発生数も１３と未親水化複合材に比較し、４少なくなった。この結果、アクリル酸グラフト重合法以外の親水化方法によっても、高精度な研磨布の作製が可能になる。
【００３０】
更に、現在、研磨時の砥粒のメカニズムはよくわかっていないが、研磨布表面の繊維の親水化によって、０．３μm以下のような微粒の砥粒分散性が向上すると考えられる。最近の砥粒はさらに微粒子化し凝集し易く、凝集によって研磨時に被研磨物にスクラッチを発生し易い。研磨布表面の繊維の親水化によって、繊維と砥粒との親和性が増し、砥粒の分散性が向上し砥粒の凝集を防止できる効果もある。
【００３１】
また、親水化研磨布は砥粒や水の保持力が大で、表面の親水性繊維の砥粒との親和性との相乗効果で均一な研磨ができ、砥粒一定量当たりの研磨効率を増大できる。また、親水性研磨布の水の保持力は、被研磨物への研磨圧力を均一にする効果もある。被研磨物の表面は研磨時に相当の高速で回転しており圧力の変動がある。このような場合、研磨物表面の柔軟性が大きいほど圧力の分散性がよく、被研磨物に研磨布が均一に接触するだけでなく、ある程度の圧力の変動にも、親水化繊維のクッション効果で圧力変動を吸収することが可能である。
【００３２】
本発明の研磨布は、高精度なメディア材料（磁気ディスク、光ディスク、磁気ヘッド類など）のポリッシュ用、バリ取り用や仕上げ用研磨布、液晶材料、装置部品の仕上げ用研磨布、ＣＭＰの洗浄用、仕上げ用研磨布、カメラ、精密部品などのポリッシュ、仕上げ用研磨布など広い分野の研磨に適用できるが、特に記録媒体用のテキスチャリング用、ポリッシング用または電子部品の仕上げ用、バフ研磨に用いることが好ましい。
【００３３】
本発明における研磨方法は、例えば以下に述べるようにして行うことができる。
【００３４】
水平な方法ではテーブル盤にシート状の研磨布を固定し、その表面に砥粒溶液を供給し分散させながら被研磨物（磁気ディスクや集積回路板）の研磨面を水平にして研磨する。垂直な場合では研磨装置に被研磨物表面を垂直方向にして取付け、砥粒スラリーを含浸した研磨布を供給し、ニップローラで加圧しながら被研磨物表面を研磨する。
【００３５】
テキスチャリング条件は、被研磨物の種類（アルミニウムの燐酸ニッケルメッキやガラス、セラミックスなど）や研磨精度によって異なるが以下の通りである。研磨布は水平の場合、円形のシート状であり、垂直法の場合は通常５〜５０ｍｍ幅（多くは３５〜４５ｍｍ）のテープ状である。研磨物の種類、大きさ、スラリーの種類によって形状や表面状態の条件の異なるものが使用され、スラリーは、平均粒径０．３μ以下のアルミナやダイヤモンドを溶液に分散したものが用いられ被研磨物の種類や表面精度によって選択される。また、研磨布は安定した研磨をするためおよそ０．３〜３ｋｇ／ｃｍ²程度に調節された圧力で研磨されるのが好ましい。
【００３６】
【実施例】
以下、本発明を実施例によりさらに詳細に説明する。実施例で用いた評価法とその測定条件について以下に説明する。
１．親水化度
Ａ．繊維状（フィラメント、ステープル）の場合
繊維状の場合は、およそ直径３〜１０ｍｍ、長さ５０ｍｍ程度の束を作製後、直径、長さ、重量を測定し嵩密度ρを算出する。繊維束は、２００μmのステンレス線で束に膨れができない（圧縮をしない）程度にピッチ２〜５ｍｍで巻き付けて直径を測定する。
【００３７】
その束状繊維を約１ｇ採取し、１０５℃で４時間乾燥後、温度２０℃、相対湿度６５％中に２４時間以上放置しその重さ（Ｗ０）ｇを精秤する。その繊維を蒸留水中に１時間放置する。繊維を蒸留水から取りだし、１００メッシュ程度のステンレス金網のかごに入れ、遠心分離器で回転数２０００ｒｐｍで２分間脱水し、その繊維の重量（Ｗ１）ｇを精秤する（測定ｎ数３で平均する。また、ステンレス線を使用する場合はその重量を除去した重量で計算する）。見かけ親水化度α１は次式で現される。
【００３８】
α１=（Ｗ１−Ｗ０）／Ｗ０×１００
本発明の親水化度αは、該見かけ親水度α１を次式で嵩密度０．５５状態での親水度化度に換算し得られる。
【００３９】
α＝α１×ρ／０．５５
Ｂ．不織布、織物の場合
評価用試料の厚み、幅、長さを測定し嵩密度ρを算出する。その中から約１ｇの試料を採取し、その後上記繊維状な場合と同じ方法で見かけ親水化度を測定し、同様に見かけ密度換算し、親水化度αを得る。
【００４０】
Ｃ．複合材の場合
複合材のエラストマー（例えばウレタン）を良好溶媒で乾燥重量が平衡状態（重量誤差が３％以下）になるまで除去し、繊維成分の不織布を得る。該不織布の親水化度αを上記不織布項の親水化度と同様の方法で測定する。
２．親水効果
親水効果△αは、親水化繊維の親水化度α１と未親水化繊維α２から次式で定義する。繊維は同種類、同繊度のもので比較する。
【００４１】
△α=α１ーα２
３．研磨評価
研磨評価をハードディスクのテキスチャリング法で評価する。被研磨物は、市販の
アルミニュウーム板にＮｉ−Ｐメッキ後ポリッシュ加工した基板（サブストレート）を使用した。該サブストレートの表面の平均表面粗さは２．８Åである。研磨布の研磨評価条件は、平均粒径０．２μｍダイヤモンド径の遊離砥粒スラリーで４．５ｍｌ／分で滴下しサブストレートをテキスチャー装置に取付け、１０００ｒｐｍ回転させ、テープを６ｃｍ／分の速度で供給しながら振幅１ｍｍで３００回／分の横方向の振動を与える条件で評価した。評価するサブストレート数は、各評価研磨布について３０枚である。
４．表面粗さ（Ｒａ）
温度２０℃、相対湿度５０％、クリーン室に設置された防音装置付きＶｅｅｃｏ製原子間力原子顕微鏡（ＡＦＭ）に試料を取付け測定する。サンプル数３０枚の表面粗さを測定しその平均表面粗さＲａで現わす。各サンプルのディスクの半径の中央点２カ所を中心点を対称に選び、各点５μm×５μmの大きさで測定する。
５．研磨評価の親水効果及び効果率
親水化繊維を含んだ研磨布で研磨した表面粗さをＲａ１と未親水化繊維を含んだ研磨布で研磨表面粗さをＲａ２とする。該親水化研磨布と未親水化研磨布は、繊維は同種類、同繊度でかつ同タイプ（不織布、複合材、織物）の研磨布間で比較する。研磨評価の親水効果△Ｒａ、効果率γは次式で示される。
△Ｒａ＝Ｒａ２−Ｒａ１
γ＝△Ｒａ／Ｒａ２（％）
６．スクラッチ数
ＺＹＧＯ製干渉型顕微鏡で表面観察し、各サンプルの表面のスクラッチ数（Ｘ）を測定する。スクラッチは、０．１μm×１００μm以上の大きさのものをカウントする。サンプル数３０枚を測定し、傷の数による下記点数ｙから、スクラッチ数βを定義する。
【００４２】
【数１】

【００４３】
以下各実施例について説明する。サンプルＡ〜Ｄには実施例で使用する極細繊維、研磨布用の研磨布（織物、不織布、複合材）の製法を示した。
【００４４】
サンプルＡ
０．３ｄ以下のポリエステル（ＰＥＳ）、ポリアミド（ＰＡＭ）極細繊維をまず以下の方法で準備する。海成分にアルカリ可溶型共重合ポリエステル樹脂５０ｗｔ％、島成分にポリエチレンテレフタレート（ＰＥＴ）樹脂またはポリアミド（ＰＡＭ；６ナイロン）樹脂５０ｗｔ％を用い溶融紡糸で島成分の本数を調節し、７．２ｄｔｅｘ高分子配列体複合繊維（単に複合繊維という）を作製後延伸し２．４ｄｔｅｘの複合繊維を得られるようにした。該複合繊維をかせ枠に巻いた状態でアルカリ水溶液処理し海成分を除去し、ポリエステル、ポリアミドの極細繊維を得た。島成分の本数によって、脱海後０．０２ｄｔｅｘの極細繊維のフィラメントが得られた。
【００４５】
同様に、ポリアミドの島成分本数を変更し紡糸し、１２ｄｔｅｘの複合繊維を得た。この複合繊維を同様に延伸、脱海し、０．２ｄｔｅｘを得た。
【００４６】
サンプルＢ
サンプルＡで得たポリアミド該高分子配列体繊維を収束し１２０ｄｔｅｘのフィラメントを作製し、このフィラメントを朱子織りで製織し織物を得た。この織物をアルカリ水溶液で処理し、海成分を除去した結果、０．０２ｄｔｅｘのポリアミド繊維の織物を得た。
【００４７】
サンプルＣ
サンプルＡで得たポリエステル、ポリアミドの繊度２．４ｄｔｅｘの複合繊維をステープル化し、このステープル繊維をカード、クロスラップ、ニードルパンチの一連の工程で極細繊維不織布を作製した。この不織布をアルカリ水溶液で海成分を除去し、ポリエステル、ポリアミド極細繊維の２種類の不織布Ｃを得た。また、その見かけ密度を０．３２〜０．３５ｇ／ｃｍ3に調節した。
【００４８】
サンプルＤ
サンプルＣで得られた２種類の不織布基材Ｃにポリウレタンのジメチルフォルムアルデヒド（ＤＭＦ）溶液を含浸後湿式凝固し、２種類の複合材基材Ｄを得た。この複合材の表面をサンドペーパでバフ加工し表面が平滑な複合材を得た。
【００４９】
実施例１〜４
サンプルＡで得られた０．０２ｄｔｅｘのポリエステル、ポリアミド極細繊維フィラメントを「かせ状」の状態で、０．０５〜０．５％濃度のアクリル酸で過硫酸アンモニュームを触媒にしてグラフト重合後、水洗、風乾し、親水化された極細繊維を得た。その各々の繊維の親水化度αと親水効果△αを前述の該測定法で測定し、その結果を表１の実施例１〜５に示した。親水化度αは、７３〜１７６となり、各極細繊維は高親水化した。実施例３、４のようにグラフトが同じ場合、ポリエステル繊維よりポリアミド繊維の方が親水化され易い。また、ポリアミド繊維（実施例１〜３）において、高濃度アクリル酸でグラフト化した方が、高親水化される。
【００５０】
実施例５
サンプルＡで得られた０．０２ｄｔｅｘのポリエステル極細繊維を親水性のエチレングリコール（ＰＥＧ）とポリエステル系高分子を共重合した高分子の０．５％溶液で処理し、表面に吸着固定した。この繊維の親水化度αは８５で高親水化された。実施例１〜４のアクリル酸に比較しやや繊維の柔軟性がやや硬いが、親水性的に特に問題はなかった。
【００５１】
実施例６〜９
実施例１〜６の繊維の替わりに、サンプルＣで得られた２種類の不織布Ｃに０．０５〜０．５％濃度でアクリル酸を過硫酸アンモニュームを触媒にして同条件でグラフト重合後、水洗、風乾し、親水化不織布基材を得た。得られた不織布の親水化度を測定した結果、表２に示したように８５〜１８４と高親水性になった。該風乾された不織布を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し不織布タイプの研磨用テープを得た。
【００５２】
実施例１０
実施例７で得られた親水化不織布基材にポリウレタンのジメチルフォルムアルデヒド（ＤＭＦ）溶液を含浸後湿式凝固、水洗、風乾し複合材基材を得た。得られた不織布の親水化度を測定した結果、表２に示したように１２３と高親水性になった。該風乾された不織布を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し複合材タイプの研磨用テープを得た。
【００５３】
実施例１１、１２
サンプルＤで得られたポリアミド極細繊維からなる２種類の「複合材」に、０．２、０．５％濃度のアクリル酸で過硫酸アンモニュームを触媒にしてグラフト重合後、水洗、風乾し、親水化複合材基材を得た。得られた不織布の親水化度を測定した結果、表２「評価用研磨布の親水化度」に示したように１０４、１６２と高親水性になった。該風乾された複合材を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し２種類の「複合材タイプ」の研磨用テープを得た。
【００５４】
実施例１３、１４
サンプルＢで得られたポリアミド極細繊維の「織物」を０．２、０．５％濃度のアクリル酸で過硫酸アンモニュームを触媒にしてグラフト重合後、水洗、風乾し、親水化織物を得た。得られた不織布の親水化度を測定した結果、表２「評価用研磨布の親水化度」に示したように１１９、１８１と高親水性になった。該風乾された複合材を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し２種類の「織物タイプ」の研磨用テープを得た。
【００５５】
実施例１５
サンプルＤで得られた０．０２ｄｔｅｘポリエステル極細繊維の「複合材」を実施例５と同様に親水性のエチレングリコール（ＰＥＧ）とポリエステル系高分子を共重合した高分子の１３０℃の０．５％溶液中で処理し、表面に吸着固定した複合材を得た。得られた不織布の親水化度を測定した結果、表２「評価用研磨布の親水化度」に示したように８０と高親水性になった。該風乾された複合材を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し「複合材タイプ」の研磨用テープを得た。
【００５６】
実施例１６〜２５
実施例６〜１５で得られた各テープを前述の研磨評価方法で評価した表面粗さＲａ１、スクラッチ数の結果を表３に示した。形状タイプ、繊維の種類、繊度が同じ研磨布の表面粗さについて、各実施例の「親水性研磨布」と比較例の「未親水性研磨布」とを比較した結果の親水化効果△Ｒａ、効果率、スクラッチ減少数を示した。本発明の親水性研磨布は表３のように、不織布、複合材、織物のどのタイプにおいても、未親水性研磨布に比較し、高精度でスクラッチ数も少なくなった。表面粗さは５．６〜７．８Åと小さく、研磨の親水効果△Ｒａ（効果率）も１．２〜２．９Å（１０〜３７％）と研磨布の親水化の効果が認められた。また、目標の７Å以下の精度の研磨が、実施例１７、１８，２０，２１，２２，２４と１０例中６例可能になり、研磨目的によって親水化の条件を制御した高精度の研磨布が可能になる。また、スクラッチ数も４〜９個とおよそ３０〜７０％低下し、安定した研磨が可能になった。
【００５７】
比較例１〜３
最初に、実施例Ａで得た未親水化の従来極細繊維の親水化度を前述の測定方法で測定した。表１の比較例１〜３のように、０．２、０．０２ｄｔｅｘポリアミド（ＰＡＭ）「未親水化」繊維の親水化度は、各々１４、３８と小さく、０．０２ｔｅｘポリエステル（ＰＥＳ）繊維の親水化度は２７である。
【００５８】
比較例４、５
サンプルＣで得られたポリアミド、ポリエステルの２種類の未親水化不織布を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し、未親水性の２種類の不織布タイプの研磨用テープを得た。該未親水性不織布の繊維の親水化度は４７、３５とフィラメントの状態に比較しやや高い。不織布の方がフィラメントよりも形態的に水分の保持性が良いと考えられる。
【００５９】
比較例６、７
サンプルＤで得られたポリアミド、ポリエステルの２種類の複合材を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し、未親水性の２種類の複合材タイプの研磨用テープを得た。該未親水化の複合材の親水化度は３３、２２とフィラメントの状態に比較しやや低い。複合材の方がフィラメントよりも形態的に水分の保持性が悪く、エラストマー樹脂の完全親水性の妨害によると考えられる。
【００６０】
比較例８
サンプルＢで得られたポリアミド繊維織物を３８ｍｍ幅に切断し、蒸留水で洗浄後、風乾し、未親水性の織物タイプの研磨用テープを得た。該未親水化の複合材の親水化度は４３とフィラメントの状態に比較しやや高い。
【００６１】
比較例９〜１３
比較例４〜８で得られた研磨用テープを前述の研磨評価方法で評価した表面粗さＲａ、スクラッチ数の結果を表３に示した。表面粗さＲａ１は８．５〜９．１Åと大きく、スクラッチ数も１１〜１５と多かった。
【００６２】
【表１】

【００６３】
【表２】

【００６４】
【表３】

【００６５】
【発明の効果】
本発明によれば、研磨布繊維の高親水化によって、研磨精度の高精度化、被研磨物のスクラッチの低減を可能にした。また、従来の研磨布用繊維の極細化技術だけでは研磨精度に限界がみえ始め、今後の磁気ディスク等の記録媒体や集積回路基板の高精度化技術に課題があったが、該技術により更なる高精度化、高密度化が可能になる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polishing cloth for high-precision polishing used for finishing recording media and integrated circuit boards. More specifically, the present invention relates to a polishing cloth for hard disk texture, a polishing cloth for secondary polishing of a hard disk, and a polishing cloth for finishing an integrated circuit board, precision equipment, and the like among recording media.
[0002]
[Prior art]
In recent years, recording media such as magnetic disks and integrated circuit boards (hereinafter referred to as objects to be polished) have become increasingly demanded for higher capacity and higher storage density due to remarkable technological innovations. Has been. For this reason, an abrasive cloth using ultrafine fibers is disclosed in JP-A-6-295432, and is disclosed as a tape-like abrasive cloth using ultrafine fibers having a diameter of 5 μm (corresponding to about 0.25 tex) or less. Japanese Patent Laid-Open No. 10-188272 discloses a method using a woven fabric, non-woven fabric, flocking, and braided tape of ultrafine fibers of 0.1 dtex or less based on the same idea. As such a precision polishing method, there is a method of polishing an object to be polished in a state perpendicular to a planar state. In the horizontal method, a sheet-like polishing cloth is fixed to the table board, and the polishing surface of the object to be polished is leveled while dispersing the abrasive solution. Then, a polishing cloth impregnated with the abrasive slurry is supplied, and the surface of the object to be polished is polished while being pressed by a nip roller. The level of surface processing technology by these precision polishing methods has been improving steadily, and the average surface roughness has reached a level of 10 mm or less. In the future, a technique capable of stably polishing with a high accuracy of 7 mm or less is expected, and a high-precision polishing cloth that is the core of this technique is required.
[0003]
Like conventional abrasive cloths containing ultrafine fibers (hereinafter referred to as conventional abrasive cloths), the use of ultrafine fibers has reached its limit, and it is difficult to produce abrasive cloths that can handle an accuracy of 7 mm or less. It was thought. For this reason, a method of making the size of the abrasive grains very fine has been studied, but even if only the abrasive grains are miniaturized, when the conventional polishing cloth is used, the fine abrasive grains are sufficiently dispersed. In other words, it is difficult to obtain a stable accuracy because the fine abrasive grains tend to aggregate and lower the polishing accuracy. Further, even if the polishing can be performed at the initial stage, there is a problem that the stability is poor and the polishing accuracy and the polishing rate are likely to be lowered in a short time.
[0004]
[Problems to be solved by the invention]
The present invention provides a polishing cloth capable of polishing the surface of an object to be polished with high accuracy.
[0005]
[Means for Solving the Problems]
In order to solve this problem, the present invention has the following configuration. That is, The polishing cloth of the present invention is An ultrafine synthetic fiber with a fineness of 0.3 dtex or less At least on the surface A polishing cloth comprising -OH, -COOH, -CONH-, -SO _Three The compound containing at least one kind of hydrophilic group is fixed, copolymerized or graft polymerized, and the degree of hydrophilicity of the fiber is 60 or more. Characterized by It is.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The form of the polishing cloth of the present invention is not particularly limited, but is an ultrafine fiber As long as the fabric contains at least the surface, Nonwoven fabrics, composite materials in which elastomers are impregnated or adhered to ultrafine fibers, woven fabrics, sheet shapes, papers, and the like can be used, but in terms of surface morphology stability of the polishing cloth, the nonwoven fabrics, composite materials, and woven fabrics are preferable. . The type of this form is appropriately selected depending on the purpose of polishing.
[0007]
In the present invention, an ultrafine fiber of 0.3 dtex or less is, for example, a multi-island type (polymer array), a sea-island type, a peeling type, a multi-layer type, or the like suggested by “Latest Spinning Technology” published in 1992 by Kobunshi Kaikai First, a composite fiber composed of two components is prepared by a similar method, and a target of 0.3 dtex or less is obtained by dissolving or removing one component of the composite fiber by physically squeezing or peeling between the two components by heat shock. Extra fine fibers can be obtained. The polymer applicable to the ultrafine fibers can be selected from polymers such as polyester, polyamide, polyphenylene sulfide, and polyolefin, and in particular, polyester and polyamide are fine fibers having a uniform fiber diameter. It is preferable in terms of obtaining.
[0008]
In the woven fabric for abrasive cloth in the present invention, spun ultrafine fibers are made into a woven fabric by an ordinary loom and used as a substrate for the abrasive cloth.
[0009]
In the present invention, the nonwoven fabric for abrasive cloth is wound on a tow-like composite fiber containing ultrafine fibers (island components), cut into staples, and formed into a sheet by a dry or wet method. Further, if necessary, the fibers are entangled with a needle punch or a water jet punch to form a nonwoven fabric structure. By removing the sea component from the composite fiber sheet thus obtained with a solvent or splitting by a physical method, a nonwoven fabric made of ultrafine fibers can be obtained. Furthermore, an adhesive component can be added and the intertwining strength between fibers can be improved. An adhesive component is preferably added to the nonwoven fabric, more preferably 10 wt% or less, and even more preferably 5 wt% or less.
[0010]
Moreover, the form of the abrasive cloth of the present invention can be obtained by impregnating an ultrafine fiber with an elastomer polymer component. The elastomer polymer component is preferably a soft or rubber polymer, more preferably a urethane, silicone, acrylic or PVA polymer. In the present invention, the elastomeric polymer component plays a role of holding abrasive grains during polishing, cushioning for surface irregularities and vibration absorption, fiber shape maintenance and the like. When the sea component polymer in the composite fiber is dissolved with an alkali, an alkali-resistant elastomer is preferable, and from the viewpoint of processability and cushioning properties, a urethane-based or rubber-based polymer elastomer is preferable. The cushioning property at the time of polishing is important in terms of polishing accuracy, and is appropriately adjusted depending on the polishing accuracy and the purpose of polishing, depending on the ratio of fibers and elastomer and the porosity. In the present invention, the content of the elastomer component is preferably 15 to 80 wt% in terms of molding, and the surface state, porosity, cushioning property, hardness, strength, etc. of the polishing cloth can be adjusted by the content. In the present invention, the thickness of the polishing cloth is preferably 3 mm or less, more preferably 1.0 mm or less, from the viewpoints of ease of processing during production, strength during polishing, abrasion resistance, water absorption, cushioning properties, and the like. The elastomer-impregnated base material can be applied not only to non-woven fabrics but also to woven fabrics and other hydrophilized abrasive cloths.
[0011]
In the present invention, in order to align the raised fibers on the surface of the nonwoven fabric or the composite material, it is preferable to perform raising or buffing. By performing brushing or buffing, the ultrafine fibers on the surface are aligned, the nap (dumpling state) does not occur in the raised fibers, and the length is made uniform. The length of the raised fiber is preferably 0.5 mm or less, more preferably 0.2 mm or less in order to avoid dumpling.
[0012]
The bulk density of the polishing cloth of the present invention is 0.2 to 0.6 g / cm. ^Three Furthermore, it is more preferable that the density is 0.30 to 0.45 from the surface high-accuracy surface. The bulk density is adjusted by the fiber bulk density, the amount of elastomer added, the pressing conditions during the processing step, and the like. Moreover, it is preferable to carry out calendering on the surface of the polishing pad from the viewpoint of flatness of the surface of the polishing pad, higher density, and improvement of the shape setting of the surface fibers.
[0013]
The elastomer resin is preferably porous in order to improve the dispersibility of the abrasive grains and the hydrophilicity of the surface fibers.
[0014]
The hydrophilized fiber of the present invention needs to be uniformly hydrophilized in order to perform high-precision polishing. For this reason, it is necessary that the hydrophilic component is contained in the fiber in an amount of 0.01 wt% to 30 wt%. It is. If it is 0.1 wt% or more, it is more preferable. Moreover, when it contains more than 30 wt%, since the lubricity of a surface and form stability deteriorate, it is unpreferable.
[0015]
As hydrophilic components, —OH, —COOH, —CONH—, —SO _Three A compound containing a hydrophilic group, such as, or a derivative thereof is preferred. Of these, acrylic acid-based, glycol-based, PVA-based, cellulose-based, silicone-based, urethane-based, hydrophilic group-containing ester-based and the like are preferable. As a method for adding the hydrophilic component to the fiber, graft polymerization of the component to the chemical fiber, blending of the physical hydrophilic compound fine particles to the fiber, adsorption or fixing to the fiber surface, and the like can be used. The following various methods can be used as a specific method for hydrophilizing the fiber, and it can be used alone or in combination depending on the purpose.
(A) Method of grafting hydrophilic molecule on fiber surface
(B) Method of copolymerizing hydrophilic component on fiber polymer itself
(C) A method of blending a hydrophilic polymer or an inorganic substance with the fiber polymer itself
(D) A method of plasma discharge or corona discharge machining of the fiber surface
(E) Method of adsorbing (adhering) a hydrophilic polymer to the fiber surface
(F) Method of treating fiber with solvent or swellable solvent
For example, regarding the method (A), a method of grafting a hydrophilic vinyl monomer to a polyester fiber is disclosed in JP-A-6-158543, and a method of grafting hydrophilic acrylic acid to a polyamide fiber is disclosed in JP-B-60-34979. It is disclosed in the gazette. Regarding the method (C), a method using a blend of hydrophilic polyoxyalkylene glycol or inorganic ionic compound is disclosed in JP-A-53-80497, JP-A-60-39413, and JP-A-9-13229. It is disclosed. Regarding the method (E), JP-A-6-11505 discloses a method in which a hydrophilic polyol is adsorbed on the fiber surface.
Method (F) is a method of treating with a solvent or swellable aqueous solution such as phenol, methylene chloride, and benzyl alcohol. When hydrophilizing the fibers of a magnetic storage disk or polishing cloth for precision electronic parts, it is preferable to avoid the use of a compound containing metal ions.
[0016]
Hydrophilization is a process of copolymerization and addition of hydrophilic components to fiber component polymers, addition of hydrophilic components during spinning, hydrophilization of fibers obtained by spinning, woven fabrics, non-woven fabrics, and composite materials. Although there are methods such as hydrophilization of the fiber surface, it can be selected depending on the purpose of use of the polishing cloth.
[0017]
Hereinafter, the hydrophilization used in the present invention will be described by the grafting method of the method (A) which is easy to process, but is not limited to this method, and the hydrophilization of the methods (B) to (F) is used. Of course it is possible.
[0018]
The present inventors examined the hydrophilicity of ultrafine synthetic fibers that have been used in conventional polishing cloths, which affect the surface condition. When the polyester fiber or polyamide fiber has a normal thickness of 2 dtex or more, the degree of hydrophilization is as low as about 5 or 10 and is more hydrophobic than hydrophilic. (The definition of hydrophilicity will be described in detail in the evaluation method in Examples below, but is evaluated by the degree of hydrophilicity (α). A highly hydrophilic polishing cloth has an affinity for, dispersion, and aggregation with abrasive grains. The prevention effect is improved, and the gripping force of abrasive grains and the ability to remove abrasive debris are improved.)
When ultrafine fibers such as conventional polyester and polyamide fibers are made ultrafine to 0.2 and 0.02 dtex, the degree of hydrophilicity is slightly improved to about several tens, but sufficient hydrophilicity cannot be obtained. In addition, an ultrafine fiber of 0.02 dtex or less cannot be produced stably with a uniform fiber, but the surface area becomes too large and the fiber on the surface of the polishing cloth converges, apparently the fiber becomes thicker, The dispersibility of the abrasive grains and the polishing accuracy are liable to decrease, and scratches (scratches) are generated on the surface of the object to be polished, making it difficult to perform stable polishing. In the future, it is very difficult to polish with high accuracy by means of only ultrafine fiber.
[0019]
Therefore, the present inventors have applied the hydrophilization of ultrafine fibers to the polishing cloth to improve the polishing cloth surface in particular.
[0020]
Example of using a fiber having a fineness of 0.02 tex and grafting a hydrophilic component in a fiber state (skein frame winding state) in order to see the effect of hydrophilization of polyester fiber and polyamide fiber by grafting of method A Is shown in Table 1. The degree of hydrophilicity of the fibers for the polishing cloth needs to be 60 or more, and preferably 100 or more. Further, the condition of the degree of hydrophilicity is preferably 1000 or less, more preferably 500 or less, because the fiber becomes soft and the form becomes unstable due to hydrophilicity.
[0021]
A polishing tape for evaluation of the degree of hydrophilization was prepared as in Examples 6 to 15 described later, and the hydrophilization conditions are shown in Table 2. In this example, hydrophilicity was obtained by graft polymerization of acrylic acid, and hydrophilicity was also obtained by adsorption of hydrophilic polyethylene glycol. In addition, it is preferable to stabilize the form after processing into a woven fabric, a non-woven fabric, or a composite material (hereinafter, the whole of the three members is simply referred to as a processed cloth). The filamentous fibers and the fibers in the work cloth have different degrees of hydrophilicity, and the nonwoven fabric and the woven fabric are slightly better than the filament, and the composite material is slightly worse. This may be due to the morphological effect of moisture retention or the influence of the resin component. Even in the filaments and work cloths of Examples 1 to 5 and Examples 6 to 15 described later (comparison of the same fiber type and shape), the nonwoven fabric and the fabric are slightly better than the filaments as in the comparative example, and the composite The material is a little worse. However, the degree of hydrophilicity of the “surface fibers” of each work cloth is considered to be close to the degree of hydrophilicity of the filaments without being greatly affected by the form of such work cloth.
[0022]
Next, the polishing cloth obtained in Examples 6 to 15 and Comparative Examples 4 to 8, which will be described later, was used, and the polishing property was evaluated by an evaluation method made by polishing described later. Table 3 shows the polishing accuracy Ra1 of the hydrophilic polishing cloth and the polishing accuracy Ra2 of the non-hydrophilic polishing cloth. The effect of the hydrophilized polishing cloth is expressed by the difference in polishing accuracy ΔRa between Ra1 and Ra2, the number of scratches on the surface of the hard disk sub-tray as the object to be polished and the number of scratch reduction. (The number of scratches is defined in the examples below, but is evaluated by the number of scratches and the number of scratches in 30 polishing evaluations)
As shown in Examples 6 to 15 of Table 3, the hydrophilic effect ΔRa (effect ratio) of the hydrophilized polishing cloth is 1.2 (10%) to 2.9 (37%) as a whole example, and the conventional polishing. Compared to cloth, high accuracy is possible. Further, the number of scratches in Table 3 in the hydrophilized abrasive cloth was about half that in the non-hydrophilic abrasive cloth, and stable polishing was possible.
[0023]
Moreover, among 10 examples of Examples 6-15, the example whose surface roughness Ra1 became the target 7 mm or less was able to be achieved in 6 examples and many examples. The hydrophilization of the method of the present invention not only enables stable and high-precision polishing, but also makes it possible to produce a high-precision polishing cloth according to the purpose by adjusting the degree of hydrophilization. In order to make the polishing cloth hydrophilic, the degree of hydrophilicity of the ultrafine fibers contained in the polishing cloth needs to be 60 or more, preferably 100 or more.
[0024]
The effect of hydrophilization is not greatly affected by the processing state (nonwoven fabric, composite material, woven fabric) in the polishing evaluation results, but this should be sufficient to make the surface of the polishing cloth more hydrophilic than the effect of hydrophilization of the entire polishing cloth. This indicates that there is an effect of higher accuracy. However, in the hydrophilization (grafting) step, the polishing cloth is softened and the form retainability is lowered. Therefore, the composite material is preferable in view of form retainability. In the case of a non-woven fabric or a woven fabric, it is preferable to add an adhesive or increase the density (weight per unit area). Since any processed polishing cloth that has become hydrophilic lacks form stability, it is preferable to combine it with a film or non-hydrophilic non-woven fabric as a backing material if necessary, and form stabilization by hydrophilic processing after backing the substrate. Is preferred.
[0025]
Further, as in Examples 16 to 25, the higher the degree of hydrophilicity (acrylic acid concentration) of each processed cloth, the lower the surface accuracy Ra1 and the larger the hydrophilic effect ΔRa, which is preferable for a highly accurate polishing cloth. The number of occurrences is reduced, and stable polishing is possible even with high accuracy. For example, in the composite material type having a hydrophilization degree of 176 of Example 22, the surface roughness Ra1 is as high as 5.6 mm, the hydrophilic efficiency ΔRa is also 2.9 mm, and the hydrophilic effect rate is improved by 37%. In addition, the number of scratches in this example is as small as 5 compared with 11 of the non-hydrophilic polishing cloth, and the generation rate is improved to half or less. However, since the polishing rate (polishing amount per unit time) decreases when the hydrophilicity is too high, it is preferable to control an appropriate degree of hydrophilicity depending on the purpose of polishing.
[0026]
Also in the non-hydrophilic abrasive cloth, as in Examples 16 to 19, 23, and 24, the highly hydrophilic abrasive cloth is higher in the non-hydrophilic abrasive cloth as in the case of the composite material in the non-hydrophilic nonwoven cloth and the woven fabric. Polishing is possible and the number of scratches is small.
[0027]
As in Examples 20 and 21 in Table 3, it is more preferable to hydrophilize (same grafting conditions) even when the same composite material is made hydrophilic when the nonwoven fabric is used than to hydrophilize the composite material.
[0028]
Example 21 is a composite material in which the base material is first impregnated and then the base material is hydrophilized (Example 11), and the degree of hydrophilization is 104. Example 20 is a composite material in which the nonwoven fabric is hydrophilized (Example 17) and then the nonwoven fabric is impregnated with urethane. The degree of hydrophilicity is 123 (Table 10 Example 10), and the hydrophilicity is highly uniform. It is. In addition, as in Examples 20 and 21 of Table 3, the abrasiveness is higher in the non-woven fabric hydrophilized composite material (Example 20) than in the hydrophilized composite material (Example 21). (Ra1: 5.8 Å, ΔRa: 2.7 で), and the number of scratches generated is very small at 4, which is preferable.
[0029]
In Example 15, the “composite material” is hydrophilized not by the acrylic acid graft polymerization method, but by adsorbing a polymer obtained by copolymerizing hydrophilic ethylene glycol (PEG) and a polyester polymer to a polyester fiber to the fiber surface. It is the method. Under this implementation condition, there is a degree of hydrophilization of about 80. Under this condition, the hydrophilic effect is slightly lower than that of other acrylic acids, but there is a hydrophilic effect. Further, as in Example 25, the degree of hydrophilicity was high (Ra1: 7.8 mm, ΔRa: 1.3 mm), and the number of scratches was 13, which was 4 less than that of the non-hydrophilic composite material. . As a result, a highly accurate polishing cloth can be produced even by a hydrophilization method other than the acrylic acid graft polymerization method.
[0030]
Further, the mechanism of abrasive grains at the time of polishing is not well understood at present, but it is considered that the dispersibility of fine abrasive grains of 0.3 μm or less is improved by making the fibers of the polishing cloth hydrophilic. Recent abrasive grains are further finely divided and easily aggregated, and due to the aggregation, scratches are easily generated on an object to be polished. The hydrophilicity of the fibers on the surface of the polishing cloth increases the affinity between the fibers and the abrasive grains, improves the dispersibility of the abrasive grains, and has the effect of preventing the aggregation of the abrasive grains.
[0031]
In addition, the hydrophilic abrasive cloth has a large holding power for abrasive grains and water, and can be evenly polished due to the synergistic effect with the affinity of the hydrophilic fibers on the surface with abrasive grains. Can be increased. Further, the water holding power of the hydrophilic polishing pad has the effect of making the polishing pressure on the object to be polished uniform. The surface of the object to be polished is rotating at a considerably high speed during polishing, and the pressure varies. In such a case, the greater the flexibility of the surface of the polished material, the better the dispersibility of the pressure. It is possible to absorb pressure fluctuations.
[0032]
The polishing cloth of the present invention is used for polishing high-precision media materials (magnetic disks, optical disks, magnetic heads, etc.), deburring and finishing polishing cloths, liquid crystal materials, polishing cloths for finishing device parts, and CMP cleaning. It can be applied to polishing in a wide range of fields such as polishing cloth for finishing, finishing, camera, precision parts, polishing cloth for finishing, etc., especially for texturing for recording media, polishing for polishing or finishing electronic parts, buffing It is preferable to use it.
[0033]
The polishing method in the present invention can be performed, for example, as described below.
[0034]
In the horizontal method, a sheet-like polishing cloth is fixed to a table board, and the polishing surface of an object to be polished (magnetic disk or integrated circuit board) is polished while supplying and dispersing the abrasive solution on the surface. In the vertical case, the surface of the object to be polished is attached to the polishing apparatus in a vertical direction, a polishing cloth impregnated with abrasive slurry is supplied, and the surface of the object to be polished is polished while being pressed by a nip roller.
[0035]
Texturing conditions vary depending on the type of object to be polished (such as nickel phosphate plating of aluminum, glass, ceramics, etc.) and polishing accuracy, but are as follows. The polishing cloth is in the form of a circular sheet when horizontal, and is usually in the form of a tape having a width of 5 to 50 mm (mostly 35 to 45 mm) in the vertical method. Depending on the type, size, and type of the slurry, different shapes and surface conditions are used, and the slurry is made by dispersing alumina or diamond with an average particle size of 0.3μ or less in a solution. It is selected according to the type of object and the surface accuracy. Moreover, the polishing cloth is approximately 0.3 to 3 kg / cm for stable polishing. ² Polishing is preferably performed at a pressure adjusted to a degree.
[0036]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. The evaluation methods and measurement conditions used in the examples are described below.
1. Hydrophilization degree
A. For fibers (filaments, staples)
In the case of a fiber, a bundle having a diameter of about 3 to 10 mm and a length of about 50 mm is prepared, and then the diameter, length, and weight are measured to calculate the bulk density ρ. The diameter of the fiber bundle is measured by winding the fiber bundle with a pitch of 2 to 5 mm so that the bundle cannot be swollen (not compressed) with a 200 μm stainless steel wire.
[0037]
About 1 g of the bundled fiber is sampled, dried at 105 ° C. for 4 hours, then left in a temperature of 20 ° C. and a relative humidity of 65% for 24 hours or more, and the weight (W0) g is precisely weighed. The fiber is left in distilled water for 1 hour. The fiber is taken out from distilled water, placed in a stainless steel mesh cage of about 100 mesh, dehydrated with a centrifuge for 2 minutes at a rotational speed of 2000 rpm, and the weight (W1) g of the fiber is precisely weighed (measured n number 3 average) Also, when using stainless steel wire, calculate the weight after removing the weight). The apparent degree of hydrophilicity α1 is expressed by the following equation.
[0038]
α1 = (W1-W0) / W0 × 100
The degree of hydrophilicity α of the present invention can be obtained by converting the apparent degree of hydrophilicity α1 into the degree of hydrophilicity in the state where the bulk density is 0.55 by the following formula.
[0039]
α = α1 × ρ / 0.55
B. For non-woven fabrics and woven fabrics
The bulk density ρ is calculated by measuring the thickness, width, and length of the sample for evaluation. About 1 g of a sample is collected from the sample, and then the apparent degree of hydrophilicity is measured in the same manner as in the case of the fibrous material, and the apparent density is converted in the same manner to obtain the degree of hydrophilicity α.
[0040]
C. For composite materials
The elastomer (for example, urethane) of the composite material is removed with a good solvent until the dry weight is in an equilibrium state (weight error is 3% or less) to obtain a nonwoven fabric of fiber components. The degree of hydrophilicity α of the nonwoven fabric is measured by the same method as the degree of hydrophilicity of the above-mentioned nonwoven fabric term.
2. Hydrophilic effect
The hydrophilic effect Δα is defined by the following equation from the degree of hydrophilicity α1 of the hydrophilic fiber and the non-hydrophilic fiber α2. Compare fibers of the same type and the same fineness.
[0041]
△ α = α1-α2
3. Polishing evaluation
The polishing evaluation is evaluated by the hard disk texturing method. The object to be polished is commercially available
A substrate (substrate) that was polished after Ni-P plating on an aluminum plate was used. The average surface roughness of the surface of the substrate is 2.8 mm. The polishing cloth was evaluated for polishing conditions by adding a free abrasive slurry having an average particle size of 0.2 μm and a diamond diameter of 4.5 ml / min. Evaluation was performed under the condition of applying a lateral vibration of 300 times / min with an amplitude of 1 mm while feeding. The number of substrates to be evaluated is 30 for each evaluation polishing cloth.
4). Surface roughness (Ra)
A sample is attached to a Veeco atomic force atomic microscope (AFM) installed in a clean room with a temperature of 20 ° C. and a relative humidity of 50% and measured. The surface roughness of 30 samples is measured and expressed as the average surface roughness Ra. Two central points of the radius of the disk of each sample are selected symmetrically, and the measurement is performed at a size of 5 μm × 5 μm.
5). Hydrophilic effect and effectiveness of polishing evaluation
The surface roughness polished with the polishing cloth containing the hydrophilic fiber is Ra1 and the polishing surface roughness is Ra2 with the polishing cloth containing the non-hydrophilic fiber. The hydrophilized abrasive cloth and the non-hydrophilic abrasive cloth are compared between abrasive cloth of the same type, the same fineness, and the same type (nonwoven fabric, composite material, woven fabric). The hydrophilic effect ΔRa and the effect rate γ of the polishing evaluation are expressed by the following equations.
ΔRa = Ra2-Ra1
γ = ΔRa / Ra2 (%)
6). Number of scratches
The surface is observed with a ZYGO interference microscope, and the number of scratches (X) on the surface of each sample is measured. Scratches with a size of 0.1 μm × 100 μm or more are counted. The number of samples 30 is measured, and the number of scratches β is defined from the following score y according to the number of scratches.
[0042]
[Expression 1]

[0043]
Each example will be described below. Samples A to D show the production method of the ultrafine fibers used in the examples and the polishing cloth (woven fabric, nonwoven fabric, composite material) for the polishing cloth.
[0044]
Sample A
First, a polyester (PES) or polyamide (PAM) ultrafine fiber of 0.3 d or less is prepared by the following method. Adjust the number of island components by melt spinning using 50 wt% of alkali-soluble copolyester resin for sea component and 50 wt% of polyethylene terephthalate (PET) resin or polyamide (PAM; 6 nylon) resin for island component, 7.2 dtex A polymer array composite fiber (simply referred to as a composite fiber) was prepared and then stretched to obtain a 2.4 dtex composite fiber. In a state where the composite fiber is wound around a skein frame, it is treated with an alkaline aqueous solution to remove sea components, and polyester and polyamide ultrafine fibers are obtained. Depending on the number of island components, a filament of ultrafine fibers of 0.02 dtex was obtained after sea removal.
[0045]
Similarly, the number of polyamide island components was changed and spun to obtain 12 dtex composite fiber. This composite fiber was similarly stretched and desealed to obtain 0.2 dtex.
[0046]
Sample B
The polyamide polymer fiber obtained in Sample A was converged to produce a 120 dtex filament, and the filament was woven with satin weave to obtain a woven fabric. This fabric was treated with an alkaline aqueous solution to remove sea components. As a result, a polyamide fiber fabric of 0.02 dtex was obtained.
[0047]
Sample C
The polyester and polyamide composite fibers obtained in Sample A having a fineness of 2.4 dtex were stapled, and ultrafine fiber nonwoven fabrics were produced from the staple fibers by a series of steps of card, cross wrap and needle punch. The sea component was removed from this non-woven fabric with an alkaline aqueous solution to obtain two types of non-woven fabric C, polyester and polyamide ultrafine fibers. The apparent density was adjusted to 0.32 to 0.35 g / cm 3.
[0048]
Sample D
Two types of non-woven fabric base material C obtained in sample C were impregnated with a dimethylformaldehyde (DMF) solution of polyurethane and wet-solidified to obtain two types of composite base material D. The surface of this composite material was buffed with sandpaper to obtain a composite material with a smooth surface.
[0049]
Examples 1-4
After graft polymerization of 0.02 dtex polyester and polyamide ultrafine fiber filaments obtained in Sample A in a “skein-like” state with 0.05 to 0.5% concentration of acrylic acid and persulfate ammonium as a catalyst, Washed with water and air dried to obtain hydrophilic ultrafine fibers. The degree of hydrophilicity α and the hydrophilic effect Δα of each fiber were measured by the above-described measurement method, and the results are shown in Examples 1 to 5 in Table 1. The degree of hydrophilicity α was 73 to 176, and each ultrafine fiber was highly hydrophilic. When the grafts are the same as in Examples 3 and 4, the polyamide fiber is more easily hydrophilized than the polyester fiber. Moreover, in the polyamide fiber (Examples 1 to 3), the one that is grafted with high-concentration acrylic acid is made highly hydrophilic.
[0050]
Example 5
The polyester microfibers of 0.02 dtex obtained in Sample A were treated with a 0.5% solution of a polymer obtained by copolymerizing hydrophilic ethylene glycol (PEG) and a polyester polymer, and adsorbed and fixed on the surface. The fiber was hydrophilized with a degree of hydrophilicity α of 85. Compared with acrylic acid of Examples 1 to 4, the flexibility of the fibers was slightly hard, but there was no particular problem in terms of hydrophilicity.
[0051]
Examples 6-9
Instead of the fibers of Examples 1 to 6, after graft polymerization under the same conditions using acrylic acid at a concentration of 0.05 to 0.5% and persulfate ammonium as a catalyst in the two types of nonwoven fabric C obtained in Sample C , Washed with water and air-dried to obtain a hydrophilic nonwoven substrate. As a result of measuring the hydrophilization degree of the obtained nonwoven fabric, as shown in Table 2, it became highly hydrophilic with 85-184. The air-dried nonwoven fabric was cut into a width of 38 mm, washed with distilled water, and then air-dried to obtain a nonwoven fabric type polishing tape.
[0052]
Example 10
The hydrophilized nonwoven fabric substrate obtained in Example 7 was impregnated with a dimethylformaldehyde (DMF) solution of polyurethane, then wet coagulated, washed with water, and air dried to obtain a composite substrate. As a result of measuring the degree of hydrophilicity of the obtained nonwoven fabric, it became 123 and highly hydrophilic as shown in Table 2. The air-dried nonwoven fabric was cut into a width of 38 mm, washed with distilled water, and then air-dried to obtain a composite type polishing tape.
[0053]
Examples 11 and 12
Two types of “composites” made of polyamide ultrafine fibers obtained in Sample D were graft-polymerized with 0.2 and 0.5% concentration of acrylic acid using persulfate ammonium as a catalyst, then washed with water and air-dried. A hydrophilic composite substrate was obtained. As a result of measuring the hydrophilization degree of the obtained nonwoven fabric, it became 104,162 and highly hydrophilic as shown in Table 2 "Hydrophilicity of the abrasive cloth for evaluation". The air-dried composite material was cut into a width of 38 mm, washed with distilled water, and then air-dried to obtain two types of “composite type” polishing tapes.
[0054]
Examples 13 and 14
The “fabric” of the polyamide ultrafine fiber obtained in Sample B was graft-polymerized with 0.2 and 0.5% concentration of acrylic acid using persulfate ammonium as a catalyst, washed with water, and air-dried to obtain a hydrophilic fabric. . As a result of measuring the degree of hydrophilicity of the obtained nonwoven fabric, it became highly hydrophilic with 119 and 181 as shown in Table 2 “Hydrophilicity of abrasive cloth for evaluation”. The air-dried composite material was cut into a width of 38 mm, washed with distilled water, and then air-dried to obtain two types of “woven fabric type” polishing tapes.
[0055]
Example 15
The “composite material” of 0.02 dtex polyester ultrafine fiber obtained in Sample D was a polymer obtained by copolymerizing hydrophilic ethylene glycol (PEG) and a polyester polymer in the same manner as in Example 5 at 0.5 ° C. A composite material was obtained by treatment in a% solution and adsorbed and fixed on the surface. As a result of measuring the hydrophilization degree of the obtained nonwoven fabric, it became high hydrophilicity with 80 as shown in Table 2 "Hydrophilicity degree of abrasive cloth for evaluation". The air-dried composite material was cut into a width of 38 mm, washed with distilled water, and then air-dried to obtain a “composite material type” polishing tape.
[0056]
Examples 16-25
Table 3 shows the results of the surface roughness Ra1 and the number of scratches obtained by evaluating the tapes obtained in Examples 6 to 15 by the above-described polishing evaluation method. About the surface roughness of the polishing cloth having the same shape type, fiber type, and fineness, the hydrophilic effect ΔRa as a result of comparing the “hydrophilic polishing cloth” of each example and the “unhydrophilic polishing cloth” of the comparative example , The effectiveness rate, the number of scratch reduction. As shown in Table 3, the hydrophilic abrasive cloth of the present invention was highly accurate and reduced the number of scratches in all types of non-woven fabric, composite material, and woven fabric as compared with the non-hydrophilic abrasive cloth. The surface roughness was as small as 5.6 to 7.8 mm, and the hydrophilic effect ΔRa (effect ratio) of polishing was 1.2 to 2.9 mm (10 to 37%), and the effect of hydrophilizing the polishing cloth was recognized. . Further, the target precision of 7 mm or less can be polished in Examples 17, 18, 20, 21, 22, 24 and 6 out of 10 cases, and high-precision polishing cloth in which the conditions for hydrophilization are controlled according to the purpose of polishing. Is possible. Further, the number of scratches was reduced by about 30 to 70% to 4 to 9, and stable polishing became possible.
[0057]
Comparative Examples 1-3
First, the hydrophilization degree of the conventional non-hydrophilic ultrafine fiber obtained in Example A was measured by the above-described measurement method. As in Comparative Examples 1 to 3 in Table 1, the hydrophilicity of 0.2, 0.02 dtex polyamide (PAM) “unhydrophilized” fibers was as small as 14, 38 respectively, and 0.02 tex polyester (PES) fibers. The degree of hydrophilicity is 27.
[0058]
Comparative Examples 4 and 5
Two types of non-hydrophilic non-woven fabrics of polyamide and polyester obtained in Sample C were cut into a width of 38 mm, washed with distilled water, and then air-dried to obtain two non-hydrophilic non-woven fabric type polishing tapes. The degree of hydrophilicity of the fibers of the non-hydrophilic nonwoven fabric is 47 and 35, which is slightly higher than the filament state. It is considered that the nonwoven fabric has better moisture retention than the filament.
[0059]
Comparative Examples 6 and 7
Two types of composite materials of polyamide and polyester obtained in Sample D were cut into a width of 38 mm, washed with distilled water and air-dried to obtain two types of non-hydrophilic composite material type polishing tape. The degree of hydrophilicity of the non-hydrophilic composite material is slightly lower than that of the filaments 33 and 22. The composite material is morphologically poorer in moisture retention than the filament, and is considered to be due to the complete hydrophilicity of the elastomer resin.
[0060]
Comparative Example 8
The polyamide fiber fabric obtained in Sample B was cut to a width of 38 mm, washed with distilled water, and then air-dried to obtain a non-hydrophilic fabric-type polishing tape. The degree of hydrophilicity of the non-hydrophilic composite material is slightly higher than 43, which is a filament state.
[0061]
Comparative Examples 9-13
Table 3 shows the results of the surface roughness Ra and the number of scratches obtained by evaluating the polishing tapes obtained in Comparative Examples 4 to 8 by the above-described polishing evaluation method. The surface roughness Ra1 was as large as 8.5 to 9.1 mm, and the number of scratches was as large as 11 to 15.
[0062]
[Table 1]

[0063]
[Table 2]

[0064]
[Table 3]

[0065]
【The invention's effect】
According to the present invention, it is possible to increase the polishing accuracy and reduce scratches on the workpiece by increasing the hydrophilicity of the polishing cloth fibers. In addition, the conventional ultrafine fiber polishing technology has started to limit the polishing accuracy, and there are problems in the future of recording media such as magnetic disks and integrated circuit substrates. High accuracy and high density can be achieved.

Claims

A polishing cloth comprising at least a surface of ultrafine synthetic fiber having a fineness of 0.3 dtex or less, wherein the compound contains at least one or more hydrophilic groups of —OH, —COOH, —CONH—, and —SO ₃ with respect to the fiber. A polishing cloth, which is fixed, copolymerized or graft-polymerized, and the degree of hydrophilicity of the fiber is 60 or more.

2. The polishing cloth according to claim 1, wherein the polishing cloth is a non-woven fabric.

The polishing cloth according to claim 1, wherein the polishing cloth is a woven fabric.

The polishing cloth according to any one of claims 1 to 3, wherein the polishing cloth is a composite material comprising ultrafine fibers and an elastomer polymer component.

The abrasive cloth according to claim 1, wherein the bulk density of the abrasive cloth is 0.2 to 0.6 g / cm ³ .

The polishing cloth according to claim 1, wherein the surface of the polishing cloth is calendered.

The abrasive cloth according to any one of claims 1 to 6, wherein the abrasive cloth is used for texturing for a recording medium, for polishing, for finishing an electronic component, or for buffing.