JP4447091B2 - Fluororesin, lubricant containing the same, and magnetic disk using the lubricant - Google Patents

Description

【００１４】
この式中のＲ¹ 、Ｒ² 、Ｒ³ は同一であっても異なっていてもよく、アルキル基、アルケニル基、アリール基、アラルキル基、あるいはこれらをハロゲン又は窒素で置換した基を表す。
【００１５】
好ましくは、Ｒ¹ 、Ｒ² 、Ｒ³ のうちの少なくとも一つは炭素数２〜２０のアルケニル基、炭素数６〜３０のアリール基、及び炭素数７〜３０のアラルキル基のうちから選ばれる。
【００１６】
好ましくは、Ｒ¹ 、Ｒ² 、Ｒ³ はフェニル基又はベンジル基である。
【００１７】
もう一つの態様において、本発明の弗素樹脂は、次の一般式により表され、合計して８個以上のπ電子を有する基を末端基として有するものである。
【００１８】
【化５】

【００１９】
この式中のＲ⁴ 、Ｒ⁵ 、Ｒ⁶ は、同一であっても異なっていてもよく、Ｈ又は有機基であって、Ｒ⁴ 、Ｒ⁵ 、Ｒ⁶ のうちの少なくとも一つは有機基である。
【００２０】
好ましくは、有機基は、アルキル基、アルケニル基、アリール基、アラルキル基、あるいはこれらをハロゲン又は窒素で置換した基でよい。
【００２１】
好ましくは、末端基には合計して１４個以上のπ電子が存在する。
【００２２】
好ましくは、上記の式（１）又は（２）で表される末端基を有する弗素樹脂はパーフルオロエーテル骨格を有する。
【００２３】
更にもう一つの態様において、本発明は上記の一般式（１）で表されるトリオルガノシリル基を末端基とする弗素樹脂を製造する方法を提供するものであり、この方法においては、末端に水酸基を有する弗素樹脂を、クロロシラン類、シリルアミン類又はシリルアミド類でシリル化する。
【００２４】
好ましくは、ＣＨ結合とＣＣｌ結合の一方又は両方を有し且つＣＦ結合を有する溶剤に、末端に水酸基を有する弗素樹脂とアミン系触媒を溶解させ、トリオルガノクロロシランを加えてシリル化するようにする。
【００２５】
もう一つ別の態様において、本発明は上記の弗素樹脂のいずれかを含む潤滑剤を提供する。
【００２６】
更に別の態様において、本発明は、上記の潤滑剤から形成した潤滑膜を表面に備えた磁気ディスクを提供する。
【００２７】
【発明の実施の形態】
本発明の弗素樹脂は、末端基（エンドキャップ基）として非極性基を有することを特徴とする。
【００２８】
本発明における非極性基の代表例は、トリオルガノシリル基である。一般に、末端トリオルガノシリル基がアルコキシ基等が存在することにより加水分解性であり、あるいは脱水縮合性であると、樹脂の保存安定性が低下するので、ここでのトリオルガノシリル基はそのような加水分解性又は脱水縮合性のないものでなければならない。本発明におけるトリオルガノシリル基は、次の一般式で表すことができる。
【００２９】
【化６】

【００３０】
この式中のＲ¹ 、Ｒ² 、Ｒ³ は同一であっても異なっていてもよく、アルキル基、アルケニル基、アリール基、アラルキル基、あるいはこれらをハロゲン又は窒素で置換した基を表す。アルキル基としては、炭素数１〜２０のもの、例えばメチル、エチル、プロピル、ブチル、ヘキシル、オクチル、ドデシル基その他を使用することができる。アルケニル基としては、炭素数２〜２０のもの、例えばビニル、アリル、イソプロペニル、ブテニル基その他を使用することができる。アリール基としては、炭素数６〜３０のもの、例えばフェニル、ナフチル、アントリル基その他を使用することができる。アラルキル基としては、炭素数７〜３０のもの、例えばベンジル、ジフェニルメチル、フェニルエチル基その他を使用することができる。
【００３１】
磁気ディスクへの潤滑膜の密着性には弗素樹脂の末端基に存在するπ電子が関与していることが見いだされたことは前述のとおりであるが、本発明の弗素樹脂の末端基として使用するトリオルガノシリル基にあっては、置換基Ｒ¹ 、Ｒ² 、Ｒ³ のうちの少なくとも一つはπ電子を有するものであるのが好ましく、すなわちＲ¹ 、Ｒ² 、Ｒ³ のうちの少なくとも一つは上述のアルケニル基、アリール基又はアラルキル基であるのが好ましい。一般には、末端基中のπ電子数が多いほど、塗布して形成した潤滑膜のディスク表面への密着性が向上するが、置換基の入手可能性の観点から、より好ましい置換基Ｒ¹ 、Ｒ² 、Ｒ³ はフェニル基又はベンジル基である。
【００３２】
一方、Ｒ¹ 、Ｒ² 、Ｒ³ がいずれもπ電子を含まないアルキル基である場合には、潤滑剤をディスク表面に塗布して形成した潤滑膜を加熱しあるいは放射線照射により処理することで、潤滑膜の密着性を改善することができる。
【００３３】
本発明における非極性末端基のもう一つの代表例は、下記の一般式で表され、合計して８個以上のπ電子を有するものである。
【００３４】
【化７】

【００３５】
この式中のＲ⁴ 、Ｒ⁵ 、Ｒ⁶ は、同一であっても異なっていてもよく、Ｈ又は有機基であって、Ｒ⁴ 、Ｒ⁵ 、Ｒ⁶ のうちの少なくとも一つは有機基である。有機基は、アルキル基、アルケニル基、アリール基、アラルキル基、あるいはこれらをハロゲン又は窒素で置換した基でよく、且つ、有機基のうちの少なくとも一つはπ電子を有し、末端基に存在するπ電子は合計して８個以上、好ましくは１４個以上になる。アルキル基としては、炭素数１〜２０のもの、例えばメチル、エチル、プロピル、ブチル、ヘキシル、オクチル、ドデシル基その他を使用することができる。アルケニル基としては、炭素数２〜２０のもの、例えばビニル、アリル、イソプロペニル、ブテニル基その他を使用することができる。アリール基としては、炭素数６〜３０のもの、例えばフェニル、ナフチル、アントリル基その他を使用することができる。アラルキル基としては、炭素数７〜３０のもの、例えばベンジル、ジフェニルメチル、フェニルエチル基その他を使用することができる。一般には、末端基中のπ電子数が多いほど、塗布して形成した潤滑膜のディスク表面への密着性が向上し、置換基Ｒ⁴ 、Ｒ⁵ 、Ｒ⁶ としては、末端基におけるπ電子の総数が８個以上となることを条件に、フェニル基、ベンジル基や、ナフチル基、アントリル基等を好ましく用いることができる。
【００３６】
本発明の弗素樹脂において用いる末端基は、従来用いられてきた極性基（オキソ酸基、水酸基、エステル基、エーテル基、カルボキシル基、ホルミル基など）と異なり、実質的に極性がないため、本発明の弗素樹脂では極性基の作用による潤滑剤の凝集が回避できる。また、本発明の弗素樹脂の末端基に存在するπ電子は、ディスク保護膜（特にダイヤモンドライクカーボンの保護膜）との相互作用のために、上記の如き極性基を導入することなしに、潤滑膜のディスクへの密着性を高めることができる。
【００３７】
弗素樹脂の骨格は特に限定されないが、炭素から構成された骨格、あるいは炭素のほかに酸素を含む骨格を有する弗素樹脂が好ましい。弗素樹脂の骨格炭素には弗素が結合している必要があり、弗素以外に、例えば水素（Ｈ）、塩素（Ｃｌ）、炭素数１〜５のアルキル基などが結合していてもよいが、骨格炭素に結合する置換基（水素を含む）のうちの５０％以上は弗素であることが好ましい。本発明では、弗素樹脂としてパーフロロ骨格又はパーフロロエーテル骨格を有するものを好ましく用いることができる。特に好ましい弗素樹脂は、パーフロロエーテル骨格を有する。また、弗素樹脂の骨格部分と末端基とは、通常酸素（Ｏ）原子を介して結合するが、骨格部分と末端基とが酸素原子を介さずに結合しているものも、本発明における弗素樹脂のカテゴリーに入るものである。従って、本発明における弗素樹脂は、上述の骨格の部分をＡで表し、末端基をＥで表して、下式により表すことができる。
Ｅ−Ｏ−Ａ−Ｏ−Ｅ （３）
又は
Ｅ−Ａ−Ｅ （４）
なお、ここでは線状構造フッ素樹脂の両末端をエンドキャップ（Ｅ）で置換したものを挙げているが、片末端構造や分岐状末端の樹脂も同様に用いることができる。
【００３８】
潤滑剤として磁気ディスクの表面に塗布後に、揮発等による膜厚の経時的な減少がなくしかも使用中の摩擦の作用で塗膜の一部が粉状の破片として失われることのない潤滑膜をディスク上に形成するために、本発明の弗素樹脂は特定の範囲内の分子量を有するべきである。上記の条件を満たすため、一般には、本発明の弗素樹脂は分子量が５００〜１０，０００程度であるのが好ましく、より好ましくは１０００〜５０００、最も好ましくは２０００〜３０００の分子量を有する。
【００３９】
本発明の弗素樹脂は、末端に例えば水酸基（ＯＨ）等の反応性の基を有する弗素樹脂を、末端基となる特定の基を有する物質と反応させて、弗素樹脂末端に適切な末端基を導入することで、容易に製造することができる。例えば、上記の式（１）で表されるトリオルガノシリル末端基を有する弗素樹脂は、末端に水酸基を有する弗素樹脂を、適切な末端基となる特定有機基を有するクロロシラン類、シリルアミン類、シリルアミド類等でシリル化することにより、簡単に製造することができる。この場合には、特にＣＨ結合とＣＣｌ結合の一方又は両方を有し且つＣＦ結合を有する溶剤に、末端に水酸基を有する弗素樹脂とアミン系触媒を溶解させ、トリオルガノクロロシラン加えてシリル化する方法を好ましく用いることができる。上記の条件を満たす溶剤の好ましい例として、１，１−ジクロロ−２，２，３，３，３−ペンタフルオロプロパンと１，３−ジクロロ−１，１，２，２，３−ペシタフルオロプロパンとの混合物のほか、スリーエム社製のＨＦＥ（ハイドロフルオロエーテル）、日本ゼオン社製のゼオローラ（Ｚｅｏｒｏｒａ）などを挙げることができる。アミン系触媒としては、トリエチルアミン、ピリジン等を用いることができる。また、上記の式（２）で表される有機末端基を有する弗素樹脂は、末端に水酸基を有する樹脂を適切な末端基となる特定有機基を有する物質と酸触媒の存在下で脱水縮合反応させる等の方法により、やはり簡単に製造することができる。
【００４０】
本発明の弗素樹脂を澗滑剤として用いる場合は、これを溶媒に溶解し、必要に応じて添加剤、界面活性剤を添加して、磁気ディスクに塗布することができる。塗布の手法は特に限定されないが、ディップコート法やスピンコート法を好ましく用いることができる。また、潤滑剤を塗布する表面の材質は特に限定されないが、本発明の潤滑剤はダイヤモンドライクカーボン（ＤＬＣ）膜に塗布するのが特に好ましい。特に高記録密度磁気ディスクの場合は、ＣＶＤ成膜した膜厚８ｎｍ以下のＤＬＣ膜を好ましく用いることができる。ＣＶＤ成膜は、スパッタ成膜より薄いＤＬＣ膜を供給できるため磁気スペーシングの短縮が可能であるが、得られる膜が薄いために、ＤＬＣ保護膜の下にある磁性体などの金属のマイグレーションの頻度が高くなる。そのようなＤＬＣ膜上に本発明の潤滑剤を塗布して潤滑膜を形成すれば、ＤＬＣ膜との高い密着性が得られる。その上、この潤滑膜は被覆性に優れ、下地のＤＬＣ膜を完全に覆うことになるので、環境中の湿分等に由来する汚染物を遮断する効果が高く、それにより、従来の潤滑膜を用いた場合よりも高温高湿下で優れた腐食耐性能力を有効に発揮でき、信頼性の高い高記録密度磁気ディスクを供給できる。
【００４１】
潤滑剤を塗布して形成したままの潤滑膜は、先に説明したように下地と完全に結合していないモバイル層を含んでいる。この層は、ディスクの回転によって生じる遠心力でディスクの周辺部に集まりやすく、この現象は、特に高記録密度用のディスクにおけるようにより高速でのディスクの回転が要求される場合に益々顕著となる。本発明の潤滑剤を用いて形成した潤滑膜の下地への密着性は高いため、モバイル層のディスク周辺への移動の度合いはそれほど大きくないが、特に高速回転の磁気ディスク及び磁気ディスク装置の場合に、この現象は厄介な問題の引き金となりかねない。本発明においては、特にこのような場合に、潤滑剤の塗布により形成した潤滑膜に、引き続き加熱又は放射線照射、あるいはその双方による架橋処理を施すことで、潤滑膜の下地への密着性を更に向上させることができる。言うまでもなく、この処理は、高速回転のディスクに必要とされるほどの密着性が必ずしも要求されるわけではない、もっと低速で回転するディスクに対しても有効なものである。また、この加熱あるいは放射線照射処理は、上記の一般式（１）で表されるトリオルガノシリル末端基におけるＲ¹ 、Ｒ² 、Ｒ³ がいずれもπ電子を含まないアルキル基である場合に、ディスク表面に形成した潤滑膜の密着性を改善するのに特に有効であることは、前述のとおりである。
【００４２】
図１に、本発明の磁気ディスク１０を模式的に示す。この磁気ディスク１０は、基板１１の上に下地膜１２、磁性材料膜１３、保護膜１４、及び潤滑膜１５を順次形成した積層構造を有する。基板１１は例えばアルミニウムやガラス等から製作される。下地膜１２はＮｉ−Ｐ、Ｎｉ−Ａｌ等で製作される。磁性材料膜１３は、例えばＣｏ、Ｃｒ等の金属、あるいはこれらを含む合金から作られる。保護膜１４は、一般にはダイヤモンドライクカーボンの膜であり、このほかに二酸化珪素（ＳｉＯ₂ ）などが用いられる場合もある。潤滑膜１５は本発明の潤滑剤から形成される。このような磁気ディスクの構造も、構成材料も、本発明による潤滑膜を除けば周知のものであり、ここで詳しく説明するには及ばない。
【００４３】
図２に、磁気ディスク装置２０を示す。この装置２０は、図１で説明した本発明の磁気ディスク１０を１枚以上含む。ディスク１０は、図示しない駆動装置により回転駆動され、スライダー２３に取り付けられた磁気ヘッド２１により記録データの書き込みと読み取りが行われる。磁気ヘッドの駆動はヘッド駆動装置２２によりなされる。磁気ディスク１０、ヘッド２１及びヘッド駆動装置２２は、図示しないエンクロージャー内に収容され、また磁気ディスク装置２０はやはり図示しないインタフェースによりほかの機器に接続される。このような磁気ディスク装置の構成も周知であり、ここで詳しく説明するには及ばない。
【００４４】
【実施例】
以下、本発明の実施例を示すが、本発明はこれらの実施例に限定されるものではない。
【００４５】
［実施例１］
この例では、弟素樹脂の合成を説明する。
還流塔、窒素バブリング管、撹拌棒、滴下ロートを取り付けた四つ口フラスコに、原料である末端水酸基を有するパーフロロポリエーテル（アウジモント社製のＺＤＯＬ４０００ｓ）を等量の１，１−ジクロロ−２，２，３，３，３−ペンタフルオロプロパンと１，３−ジクロロ−１，１，２，２，３−ペシタフルオロプロパンとの混合溶液（旭硝子社製ＡＫ−２２５）で希釈して入れ、末端水酸基に対して３倍モルの脱水ピリジンを加え、５０℃で窒素バブリングしながら撹拌し、滴下ロートから末端水酸基の３倍モルのトリフェニルクロロシラン（ＴＰｈ）を２倍量のＡＫ−２２５で希釈して滴下し、滴下後７０℃の温度で４時間撹拌し、シリル化反応を行った。次に、反応溶液が中性になるまで水洗し、更に酢酸ブチルで２回洗浄した後、ロータリーエバポレータで溶媒成分を蒸発させ、０．１μｍのメンブランフィルタで濾過を行った。ＮＭＲにて組成分折を行って、パーフロロポリエーテルの水酸基の９８％がシリル化されていることを確認した。
【００４６】
［実施例２］
実施例１のシリル化剤であるトリフェニルクロロシラン（ＴＰｈ）に代え、トリベンジルクロロシラン（ＴＢｚ）、アリルジメチルクロロシラン（ＡＤＭ）、ジメチルビニルクロロシラン（ＤＭＶ）、トリビニルクロロシラン（ＴＶｎ）、ジフェニルビニルクロロシラン（ＤＰＶ）、トリエチルクロロシラン（ＴＥｔ）を用いて、実施例１と同様に弗素樹脂を合成した。ＮＭＲにて組成分析を行ったところ、全ての樹脂において水酸基の９５％以上がシリル化されていることが確認された。
【００４７】
［実施例３］
実施例１と２で合成した弗素樹脂（全７種）の耐熱性を調べるために、熱重量分折により各樹脂の熱分解性試験を行った。測定は窒素雰囲気中で２０℃／ｍｉｎの昇温速度で行い、５％重量減少時の温度を表１に示した。表中に示した樹脂末端基は、末端のシリル化に用いたシリル化剤の符号と一致しており、例えばトリフェニルクロロシラン（ＴＰｈ）でシリル化した樹脂の末端基はＴＰｈで表示されている。
【００４８】
【表１】

【００４９】
［実施例４］
実施例１と２で合成した弗素樹脂（全７種）を、住友３Ｍ社製のＦＣ−７７溶媒に溶解した。Ｎｉ−Ｐメッキされたアルミニウム板を研磨し、テクスチャー処理して中心線粗さ（Ｒａ）を６．５ｎｍとした基板上に、ＤＣマグネトロンスパッタリングによりＡｒガス雰囲気中でＣｒ磁性層とＣｏＣｒＴａ系磁性層を形成し、そしてＣＶＤ法でダイヤモンドライクカーボン（ＤＬＣ）保護膜（膜厚８ｎｍ）を形成したディスクを用意した。これに、前述のＦＣ−７７溶媒に溶解した末端変性樹脂の潤滑剤７種をそれそれディップコート法で塗布して成膜した。比較のために、末端を変性せずに水酸基を持った弗素樹脂を使って、同様にディスク上に潤滑剤を成膜した。ディスク上の潤滑剤膜厚を赤外吸収スペクトルにて測定し、続いてこのディスクをＦＣ−７７溶媒に浸漬して、ディスクに結合していないモバイル層を溶解除去し、膜厚を再測定して、ボンド率（＝溶解後膜厚／初期膜厚）を測定した。更に、潤滑剤塗布後に低圧水銀ランプで５秒間表面を全面照射したディスクについて、同様にボンド率を測定した。得られた結果を表２に示す。表２に示した樹脂末端基は、表１と同じく用いたシリル化剤の符号と一致している。また、表２には末端基に存在するπ電子数も示されている。
【００５０】
【表２】

【００５１】
［実施例５］
Ｎｉ−Ｐメッキされたアルミニウム板を研磨し、テクスチャー処理して中心線粗さ（Ｒａ）を５ｎｍとした基板上に、ＤＣマグネトロンスパッタリングによりＡｒガス雲囲気中でＣｒ磁性層を５０ｎｍ、ＣｏＣｒＴａ系磁性層を４０ｎｍ順次形成後、その上にＤＬＣ保護膜を形成したディスクを用意した。このディスク表面に実施例４と同様に架橋潤滑膜（２．５ｎｍ厚）を形成した。得られた磁気ディスクについて、アルミナとＴｉＣとの焼結体からなる薄膜ヘッドを取り付けたスライダーを用い、スライダー浮上量０．１μｍ、ディスク回転数３６００ｒｐｍで１５秒稼動−１５秒停止のサイクル試験を行い、耐ＣＳＳ（コンタクト・スタート・ストップ）特性をディスク摩擦試験機で調べた。その結果を、摩擦係数が０．６に達した時のＣＳＳ回数として表３に示す。
【００５２】
【表３】

【００５３】
以上が本発明の実施形態の一例である。このほかにも、本発明の実施形態として考えられるものに、本発明の潤滑剤から形成した潤滑膜を備えた磁気ディスクを含む磁気ディスク装置が挙げられる。
【００５４】
【発明の効果】
以上説明したように、本発明により、ディスクとのボンド率が高く、摩擦、磨粍が少なく、かつ耐熱性とはっ水性（弗素樹脂ははっ水性の材料として知られている）が高い潤滑膜を供給することができる弗素樹脂を提供することが可能になった。この樹脂を磁気ディスク用潤滑剤として使用することにより、潤滑膜のモバイル層によるディスクの高速回転時の膜厚変動やヘッドクラッシュを防止でき、特に高温高湿環境での使用においても信頼性の著しく高い磁気ディスク及び磁気ディスク装置を供給することができる。
【図面の簡単な説明】
【図１】本発明の磁気ディスクを説明する図である。
【図２】磁気ディスク装置を説明する図である。
【符号の説明】
１０…磁気ディスク
１５…潤滑膜
２０…磁気ディスク装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel fluorine resin. This fluorine resin is particularly useful as a lubricant. More specifically, the present invention relates to a fluororesin-based lubricant for magnetic recording media, particularly a medium useful for preventing data destruction of recording media due to friction and wear between the magnetic disk media and the head of the magnetic recording apparatus, and The present invention relates to a magnetic disk using this lubricant.
[0002]
[Prior art]
2. Description of the Related Art Recently, in a magnetic disk device, as a drive device start / stop system, a magnetic head is brought into contact with the surface of a disk of a magnetic recording medium when the drive device is stopped, and the recording medium is rotated as the drive device is driven. With the slider mechanism, a contact start / stop (CSS) method has been mainstream, in which the magnetic head is lifted from the disk surface by a certain amount, and the magnetic head is brought into contact with the disk surface again by stopping the drive device. . In the CSS system, when the disk is restarted after the magnetic disk and the slider (head) have been in contact for a long time, the disk cannot be started due to high stiction, or both come in contact with the magnetic field. The recorded data may be destroyed (head crash) or the head or gimbal may be damaged. Since the surface roughness of the disk and the properties of the material greatly affect the occurrence of stiction, it is made of a specific fluorine-containing resin on a protective film (generally diamond-like carbon (DLC) or silicon dioxide) on the disk magnetic layer. It has been proposed to form a lubricant layer (US Pat. No. 3,778,308, US Pat. No. 4,267,238, US Pat. No. 4,268,556).
[0003]
The perfluoro resin compound that is currently used as a lubricant for magnetic disks is designed to have a highly polar functional group at the end of the resin structure in order to improve adhesion to the magnetic disk as a substrate. . For example, those in which an oxo acid group, a hydroxyl group, an ester group, and an ether group are directly bonded to the terminal of the perfluororesin skeleton are known.
[0004]
[Problems to be solved by the invention]
In recent years, along with the explosive spread of personal computers and higher performance, magnetic disk devices have increased in recording density and speed, and the distance between the head and the disk (flying height) has become shorter (lower). Or increasing the rotational speed of the disk. In particular, notebook computers and the like that are rapidly spreading recently have various usage environments from high temperature and high humidity to low temperature and low humidity, and it is necessary to suppress stiction even in these environments. In order to meet these demands and to improve the performance of magnetic disk devices, in recent magnetic disk devices, the performance of the lubricant on the disk surface has become more important than ever.
[0005]
The major problem with known magnetic disk lubricants is that they are designed to have a highly polar functional group at the end of the resin structure in order to increase the adhesion to the magnetic disk substrate. The adhesion to the disk actually obtained was insufficient, and since the polarity of the terminal group was large, the interaction between the terminal groups was large, so that the lubricant molecules were likely to aggregate.
[0006]
When the lubricant is applied to the surface of the magnetic disk, the above-mentioned polar group at the end of the lubricant molecule is adsorbed on the disk surface, so that the adhesion between the lubricant and the disk is maintained. However, in the case of a lubricant having poor adhesion, a large amount of a component that moves freely without being bonded to the disk (mobile 1) exists in the upper layer portion of the applied lubricant. This component layer (mobile layer) is pushed to the periphery of the disk by centrifugal force during high-speed rotation of the disk after starting the magnetic disk device, causing film thickness fluctuation in the radial direction of the disk and sticking to the head part. When the flying height is lowered, the head crashes.
[0007]
Aggregation of the lubricant causes deterioration of the film quality in a magnetic disk lubricating film that requires a uniform and ultra-thin film of a single molecule to several molecular layers. In magnetic disks, the uniformity of lubricant coating is extremely important. If so-called coating unevenness occurs, the flying characteristics and frictional characteristics of the head deteriorate, causing head crashes. This causes the problem that the impurities intrude into the inside of the medium and cause corrosion of the magnetic material.
[0008]
Furthermore, conventional lubricants have low heat resistance, and the lubricant decomposes due to frictional heat generated during heating and high-speed rotation of the magnetic disk, and the decomposed product deteriorates the friction characteristics and causes a head crash. There was also a problem.
[0009]
Accordingly, the present invention seeks to provide a fluorine resin suitable for use as a lubricant capable of supplying a lubricating film having high adhesion to the magnetic disk surface, low friction and wear, and good heat resistance. To do. Another object of the present invention is to provide a magnetic disk using this lubricant.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to improve the adhesion of a lubricating film based on a fluororesin to the magnetic disk surface, the inventors have successfully solved the above problem by introducing a specific functional group into the end group of the fluororesin. I found what I could do. That is, as a lubricant, a fluorine resin using a nonpolar group instead of a polar group such as an oxo acid group, a hydroxyl group, an ester group, an ether group, a carboxyl group, or a formyl group that has been conventionally used as a terminal group is used. It was found that the adhesion of the lubricating film to the surface of the magnetic disk was greatly improved when used. Furthermore, it has been found that the number of π electrons present in the nonpolar group is greatly involved in the adhesion of the lubricating film.
[0011]
Therefore, the fluororesin of the present invention has a nonpolar group as a terminal group (end cap group).
[0012]
In one embodiment, the fluorine resin of the present invention has a triorganosilyl group having no hydrolyzability or dehydration condensation property as a terminal group. The triorganosilyl group here can be represented by the following general formula.
[0013]
[Formula 4]

[0014]
R ¹ , R ² and R ^{3 in} this formula may be the same or different and each represents an alkyl group, an alkenyl group, an aryl group, an aralkyl group, or a group obtained by substituting these with a halogen or nitrogen.
[0015]
Preferably, at least one of R ¹ , R ² and R ³ is selected from an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, and an aralkyl group having 7 to 30 carbon atoms. .
[0016]
Preferably, R ¹ , R ² and R ³ are a phenyl group or a benzyl group.
[0017]
In another embodiment, the fluororesin of the present invention is represented by the following general formula, and has as a terminal group groups having a total of 8 or more π electrons.
[0018]
[Chemical formula 5]

[0019]
R ⁴ , R ⁵ and R ^{6 in} this formula may be the same or different, and are H or an organic group, and at least one of R ⁴ , R ⁵ and R ⁶ is an organic group. It is.
[0020]
Preferably, the organic group may be an alkyl group, an alkenyl group, an aryl group, an aralkyl group, or a group obtained by substituting these with a halogen or nitrogen.
[0021]
Preferably, there are a total of 14 or more π electrons in the terminal group.
[0022]
Preferably, the fluorine resin having a terminal group represented by the above formula (1) or (2) has a perfluoroether skeleton.
[0023]
In still another embodiment, the present invention provides a method for producing a fluororesin having a triorganosilyl group represented by the general formula (1) as a terminal group. A fluorine resin having a hydroxyl group is silylated with chlorosilanes, silylamines or silylamides.
[0024]
Preferably, a fluorine resin having a terminal hydroxyl group and an amine catalyst are dissolved in a solvent having one or both of a CH bond and a CCl bond and a CF bond, and triorganochlorosilane is added for silylation. .
[0025]
In another aspect, the present invention provides a lubricant comprising any of the fluororesins described above.
[0026]
In yet another aspect, the present invention provides a magnetic disk having a lubricating film formed from the above-mentioned lubricant on its surface.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
The fluororesin of the present invention is characterized by having a nonpolar group as a terminal group (end cap group).
[0028]
A representative example of the nonpolar group in the present invention is a triorganosilyl group. In general, if the terminal triorganosilyl group is hydrolyzable due to the presence of an alkoxy group or the like, or is dehydration-condensable, the storage stability of the resin is lowered. It must not be hydrolyzable or dehydrated. The triorganosilyl group in the present invention can be represented by the following general formula.
[0029]
[Chemical 6]

[0030]
R ¹ , R ² and R ^{3 in} this formula may be the same or different and each represents an alkyl group, an alkenyl group, an aryl group, an aralkyl group, or a group obtained by substituting these with a halogen or nitrogen. As the alkyl group, those having 1 to 20 carbon atoms such as methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl group and the like can be used. As the alkenyl group, those having 2 to 20 carbon atoms such as vinyl, allyl, isopropenyl, butenyl group and the like can be used. As the aryl group, those having 6 to 30 carbon atoms such as phenyl, naphthyl, anthryl group and the like can be used. As the aralkyl group, those having 7 to 30 carbon atoms such as benzyl, diphenylmethyl, phenylethyl group and the like can be used.
[0031]
As described above, the adhesion of the lubricating film to the magnetic disk was found to involve the π electrons present in the end group of the fluororesin, but it was used as the end group of the fluororesin of the present invention. In the triorganosilyl group, it is preferable that at least one of the substituents R ¹ , R ² , R ³ has π electrons, that is, of R ¹ , R ² , R ³ . At least one is preferably the alkenyl group, aryl group or aralkyl group described above. In general, the greater the number of π electrons in the terminal group, the better the adhesion of the lubricant film formed by coating to the disk surface. From the viewpoint of the availability of substituents, more preferred substituents R ¹ , R ² and R ³ are a phenyl group or a benzyl group.
[0032]
On the other hand, when all of R ¹ , R ² , and R ³ are alkyl groups that do not contain π electrons, a lubricating film formed by applying a lubricant to the disk surface is heated or treated by irradiation. The adhesion of the lubricating film can be improved.
[0033]
Another representative example of the nonpolar end group in the present invention is represented by the following general formula and has a total of 8 or more π electrons.
[0034]
[Chemical 7]

[0035]
R ⁴ , R ⁵ and R ^{6 in} this formula may be the same or different, and are H or an organic group, and at least one of R ⁴ , R ⁵ and R ⁶ is an organic group. It is. The organic group may be an alkyl group, an alkenyl group, an aryl group, an aralkyl group, or a group obtained by substituting these with a halogen or nitrogen, and at least one of the organic groups has a π electron and exists in the terminal group. The total number of π electrons is 8 or more, preferably 14 or more. As the alkyl group, those having 1 to 20 carbon atoms such as methyl, ethyl, propyl, butyl, hexyl, octyl, dodecyl group and the like can be used. As the alkenyl group, those having 2 to 20 carbon atoms such as vinyl, allyl, isopropenyl, butenyl group and the like can be used. As the aryl group, those having 6 to 30 carbon atoms such as phenyl, naphthyl, anthryl group and the like can be used. As the aralkyl group, those having 7 to 30 carbon atoms such as benzyl, diphenylmethyl, phenylethyl group and the like can be used. In general, the greater the number of π electrons in the terminal group, the better the adhesion of the coated lubricating film to the disk surface. The substituents R ⁴ , R ⁵ , and R ⁶ are π electrons in the terminal group. A phenyl group, a benzyl group, a naphthyl group, an anthryl group, or the like can be preferably used on the condition that the total number of is 8 or more.
[0036]
Unlike the conventional polar groups (oxo acid groups, hydroxyl groups, ester groups, ether groups, carboxyl groups, formyl groups, etc.), the terminal groups used in the fluororesin of the present invention are not substantially polar. In the fluorine resin of the invention, aggregation of the lubricant due to the action of the polar group can be avoided. In addition, the π electrons present in the terminal group of the fluororesin of the present invention can be lubricated without introducing a polar group as described above for interaction with the disk protective film (particularly diamond-like carbon protective film). The adhesion of the film to the disk can be improved.
[0037]
The skeleton of the fluorine resin is not particularly limited, but a fluorine resin having a skeleton composed of carbon or a skeleton containing oxygen in addition to carbon is preferable. It is necessary that fluorine is bonded to the skeleton carbon of the fluororesin. In addition to fluorine, for example, hydrogen (H), chlorine (Cl), an alkyl group having 1 to 5 carbon atoms, or the like may be bonded. 50% or more of the substituents (including hydrogen) bonded to the skeleton carbon are preferably fluorine. In the present invention, a fluororesin having a perfluoro skeleton or a perfluoro ether skeleton can be preferably used. Particularly preferred fluorine resins have a perfluoroether skeleton. In addition, the skeleton portion and the terminal group of the fluororesin are usually bonded via an oxygen (O) atom, but those having the skeleton portion and the terminal group bonded without an oxygen atom may also be used in the present invention. It is in the resin category. Therefore, the fluororesin in the present invention can be represented by the following formula, where the skeleton portion is represented by A and the terminal group is represented by E.
E-O-A-O-E (3)
Or E-A-E (4)
In addition, although the thing which substituted the both ends of the linear structure fluororesin with the end cap (E) is mentioned here, resin of a single terminal structure or a branched terminal can be used similarly.
[0038]
A lubricant film that does not lose its film thickness over time due to volatilization or the like after application to the surface of the magnetic disk as a lubricant, and in which a part of the coating film is not lost as powdered fragments due to friction during use. In order to form on a disc, the fluororesin of the present invention should have a molecular weight within a certain range. In order to satisfy the above conditions, in general, the fluorine resin of the present invention preferably has a molecular weight of about 500 to 10,000, more preferably 1000 to 5000, and most preferably 2000 to 3000.
[0039]
The fluororesin of the present invention is prepared by reacting a fluororesin having a reactive group such as a hydroxyl group (OH) at a terminal with a substance having a specific group serving as a terminal group, thereby providing an appropriate terminal group at the terminal of the fluororesin. By introducing, it can be manufactured easily. For example, the fluorine resin having a triorganosilyl terminal group represented by the above formula (1) is a fluorine resin having a hydroxyl group at the terminal, and chlorosilanes, silylamines, silylamides having a specific organic group as an appropriate terminal group. It can be easily produced by silylation with a kind or the like. In this case, a method in which a fluorine resin having a hydroxyl group at the terminal and an amine catalyst are dissolved in a solvent having one or both of a CH bond and a CCl bond and having a CF bond, and silylation is performed by adding triorganochlorosilane. Can be preferably used. Preferred examples of the solvent satisfying the above conditions include 1,1-dichloro-2,2,3,3,3-pentafluoropropane and 1,3-dichloro-1,1,2,2,3-pesitafluoro In addition to a mixture with propane, HFE (hydrofluoroether) manufactured by 3M, Zeorara manufactured by Nippon Zeon Co., Ltd., and the like can be used. As the amine catalyst, triethylamine, pyridine and the like can be used. The fluorine resin having an organic terminal group represented by the above formula (2) is a dehydration condensation reaction of a resin having a hydroxyl group at the terminal in the presence of a substance having a specific organic group as an appropriate terminal group and an acid catalyst. It can also be easily manufactured by a method such as
[0040]
When the fluororesin of the present invention is used as a lubricant, it can be dissolved in a solvent and, if necessary, an additive and a surfactant can be added and applied to a magnetic disk. The coating method is not particularly limited, but a dip coating method or a spin coating method can be preferably used. The material of the surface to which the lubricant is applied is not particularly limited, but the lubricant of the present invention is particularly preferably applied to a diamond-like carbon (DLC) film. Particularly in the case of a high recording density magnetic disk, a DLC film with a film thickness of 8 nm or less formed by CVD can be preferably used. CVD deposition can reduce the magnetic spacing because it can supply a thinner DLC film than sputter deposition. However, because the resulting film is thin, the migration of metals such as magnetic materials under the DLC protective film is difficult. Increases frequency. When the lubricant film of the present invention is formed on such a DLC film to form a lubricant film, high adhesion to the DLC film can be obtained. In addition, since this lubricating film has excellent coverage and completely covers the underlying DLC film, it has a high effect of blocking contaminants derived from moisture in the environment. Can effectively exhibit excellent corrosion resistance at high temperature and high humidity, compared to the case of using, and can supply a highly reliable high recording density magnetic disk.
[0041]
As described above, the lubricating film as formed by applying the lubricant includes the mobile layer that is not completely bonded to the base. This layer tends to collect at the periphery of the disk due to the centrifugal force generated by the rotation of the disk, and this phenomenon becomes more prominent especially when a higher-speed disk rotation is required, as in a high recording density disk. . Since the adhesion of the lubricating film formed using the lubricant of the present invention to the base is high, the degree of movement of the mobile layer to the periphery of the disk is not so great, but particularly in the case of a magnetic disk and a magnetic disk device that rotate at high speed. Moreover, this phenomenon can trigger troublesome problems. In the present invention, particularly in such a case, the lubricating film formed by applying the lubricant is subsequently subjected to crosslinking treatment by heating or radiation irradiation, or both, thereby further improving the adhesion of the lubricating film to the ground. Can be improved. Needless to say, this process is also effective for a disk rotating at a lower speed, which does not necessarily require the adhesion required for a disk rotating at a high speed. In addition, this heating or irradiation treatment is performed when R ¹ , R ² , and R ³ in the triorganosilyl end group represented by the general formula (1) are all alkyl groups that do not contain π electrons. As described above, it is particularly effective for improving the adhesion of the lubricating film formed on the disk surface.
[0042]
FIG. 1 schematically shows a magnetic disk 10 of the present invention. The magnetic disk 10 has a laminated structure in which a base film 12, a magnetic material film 13, a protective film 14, and a lubricating film 15 are sequentially formed on a substrate 11. The substrate 11 is made of, for example, aluminum or glass. The base film 12 is made of Ni—P, Ni—Al, or the like. The magnetic material film 13 is made of, for example, a metal such as Co or Cr, or an alloy containing these metals. The protective film 14 is generally a diamond-like carbon film, and in addition, silicon dioxide (SiO ₂ ) or the like may be used. The lubricating film 15 is formed from the lubricant of the present invention. The structure and constituent materials of such a magnetic disk are well known except for the lubricating film according to the present invention, and need not be described in detail here.
[0043]
FIG. 2 shows the magnetic disk device 20. The apparatus 20 includes one or more magnetic disks 10 of the present invention described with reference to FIG. The disk 10 is rotationally driven by a drive device (not shown), and recording data is written and read by a magnetic head 21 attached to the slider 23. The magnetic head is driven by a head driving device 22. The magnetic disk 10, the head 21, and the head driving device 22 are accommodated in an enclosure (not shown), and the magnetic disk device 20 is also connected to other devices through an interface (not shown). The configuration of such a magnetic disk device is also well known and will not be described in detail here.
[0044]
【Example】
Examples of the present invention will be described below, but the present invention is not limited to these examples.
[0045]
[Example 1]
In this example, the synthesis of a discotic resin is described.
A 4-necked flask equipped with a reflux tower, a nitrogen bubbling tube, a stirring rod, and a dropping funnel is charged with 1,1-dichloro-2 in an equivalent amount of perfluoropolyether having a terminal hydroxyl group (ZDOL4000s manufactured by Augmont) as a raw material. , 2,3,3,3-pentafluoropropane and 1,3-dichloro-1,1,2,2,3-pesitafluoropropane mixed solution (AK-225 manufactured by Asahi Glass Co., Ltd.) Add 3 times mole of dehydrated pyridine to the terminal hydroxyl group, stir while nitrogen bubbling at 50 ° C., and add 3 times mole of triphenylchlorosilane (TPh) of the terminal hydroxyl group from the dropping funnel with 2 times amount of AK-225. The solution was diluted and added dropwise, and after the addition, the mixture was stirred at a temperature of 70 ° C. for 4 hours to carry out a silylation reaction. Next, the reaction solution was washed with water until neutral, and further washed twice with butyl acetate, and then the solvent component was evaporated with a rotary evaporator and filtered with a 0.1 μm membrane filter. Compositional analysis was performed by NMR, and it was confirmed that 98% of the hydroxyl groups of perfluoropolyether were silylated.
[0046]
[Example 2]
Instead of triphenylchlorosilane (TPh), which is the silylating agent of Example 1, tribenzylchlorosilane (TBz), allyldimethylchlorosilane (ADM), dimethylvinylchlorosilane (DMV), trivinylchlorosilane (TVn), diphenylvinylchlorosilane ( Fluorine resin was synthesized in the same manner as in Example 1 using DPV) and triethylchlorosilane (TEt). When composition analysis was performed by NMR, it was confirmed that 95% or more of the hydroxyl groups were silylated in all the resins.
[0047]
[Example 3]
In order to examine the heat resistance of the fluororesins synthesized in Examples 1 and 2 (all 7 types), a thermal decomposability test of each resin was performed by thermogravimetric analysis. The measurement was performed at a rate of temperature increase of 20 ° C./min in a nitrogen atmosphere, and the temperature at 5% weight loss is shown in Table 1. The resin end groups shown in the table match the signs of the silylating agent used for terminal silylation. For example, the end groups of the resin silylated with triphenylchlorosilane (TPh) are represented by TPh. .
[0048]
[Table 1]

[0049]
[Example 4]
The fluorine resins (seven types in total) synthesized in Examples 1 and 2 were dissolved in FC-77 solvent manufactured by Sumitomo 3M. A Cr-magnetic layer and a CoCrTa-based magnetic layer are polished in a Ar gas atmosphere by DC magnetron sputtering on a substrate having a center line roughness (Ra) of 6.5 nm after polishing a Ni-P plated aluminum plate. Then, a disk on which a diamond-like carbon (DLC) protective film (film thickness: 8 nm) was formed by a CVD method was prepared. 7 types of terminal-modified resin lubricants dissolved in the above-mentioned FC-77 solvent were applied thereto by a dip coating method to form a film. For comparison, a lubricant film was similarly formed on the disk using a fluorine resin having a hydroxyl group without modifying the terminal. Measure the lubricant film thickness on the disk by infrared absorption spectrum, and then immerse this disk in FC-77 solvent to dissolve and remove the mobile layer not bonded to the disk, and re-measure the film thickness. Then, the bond ratio (= film thickness after dissolution / initial film thickness) was measured. Furthermore, the bond rate was measured in the same manner for the disk whose surface was entirely irradiated with a low-pressure mercury lamp for 5 seconds after applying the lubricant. The obtained results are shown in Table 2. The resin end groups shown in Table 2 coincide with the signs of the silylating agent used as in Table 1. Table 2 also shows the number of π electrons present in the terminal group.
[0050]
[Table 2]

[0051]
[Example 5]
A Ni-P plated aluminum plate is polished and textured to form a center line roughness (Ra) of 5 nm on a substrate with a Cr magnetic layer of 50 nm in a Ar gas cloud atmosphere by DC magnetron sputtering. A disk having a DLC protective film formed thereon after sequentially forming layers of 40 nm was prepared. A crosslinked lubricating film (2.5 nm thick) was formed on the disk surface in the same manner as in Example 4. The obtained magnetic disk was subjected to a cycle test of 15 seconds of operation and 15 seconds of stop at a slider flying height of 0.1 μm and disk rotation speed of 3600 rpm using a slider with a thin film head made of a sintered body of alumina and TiC. The CSS (contact start / stop) characteristics were examined with a disk friction tester. The results are shown in Table 3 as the number of CSS when the friction coefficient reached 0.6.
[0052]
[Table 3]

[0053]
The above is an example of an embodiment of the present invention. In addition to this, a magnetic disk device including a magnetic disk provided with a lubricating film formed from the lubricant of the present invention is considered as an embodiment of the present invention.
[0054]
【The invention's effect】
As described above, according to the present invention, a high bond rate with a disk, less friction and abrasion, and heat resistance and water repellency (fluorine resin is known as a water repellant material) are highly lubricated. It has become possible to provide a fluorine resin capable of supplying a film. By using this resin as a lubricant for magnetic disks, it is possible to prevent fluctuations in the film thickness and head crashes during high-speed rotation of the disk due to the mobile layer of the lubricating film. High magnetic disks and magnetic disk devices can be supplied.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a magnetic disk of the present invention.
FIG. 2 is a diagram illustrating a magnetic disk device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Magnetic disk 15 ... Lubrication film 20 ... Magnetic disk apparatus

Claims (7)

A triorganosilyl group having no hydrolyzability or dehydration condensation property represented by the following general formula:

(R ¹ , R ² and R ^{3 in} this formula may be the same or different, and represent an alkenyl group or a group obtained by substituting it with halogen or nitrogen )
Fluorine resins having as terminal groups. R ^1, R ^2, at least one of R ³ is selected from an alkenyl group having 2 to 20 carbon atoms, according to claim 1 wherein fluorine resin.   The fluorine resin according to claim 1 or 2, wherein the fluorine resin has a perfluoroether skeleton. The following general formula

(R ¹ , R ² and R ^{3 in} this formula may be the same or different, and represent an alkenyl group or a group obtained by substituting it with halogen or nitrogen)
A fluorine resin having a triorganosilyl group as a terminal group represented by formula (1), wherein the fluorine resin having a hydroxyl group at the terminal is silylated with chlorosilane, silylamine or silylamide to convert the general formula (1) into a terminal group. obtaining a fluorine resin to be, fluoric resin production method.   A fluorine resin having a hydroxyl group at the terminal and an amine-based catalyst are dissolved in a solvent having one or both of a CH bond and a CCl bond and having a CF bond, and triorganochlorosilane is added to form a fluorine resin having a hydroxyl group at the terminal. The method of claim 4, wherein the silylation is performed.   A lubricant comprising the fluorine resin according to any one of claims 1 to 3.   A magnetic disk provided with a lubricating film formed on the surface thereof from the lubricant according to claim 6.

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