JP4023013B2 - Surface modifier, magnetic recording medium, and magnetic recording apparatus - Google Patents

Description

【００４２】
表1の溶媒はいずれも双極子モーメントが1.0 Debye以上であり、且つ水酸基、或いはカルボキシル基を有しないものであった。次にAM2001を溶解しない溶媒を双極子モーメントの範囲と水酸基、或いはカルボキシル基の有無によって表2〜4に示す。まずAM2001を溶解しない溶媒のうち水酸基、或いはカルボキシル基を有しないものを表2に示す。
【００４３】
【表２】

【００４４】
【表３】

【００４５】
【表４】

【００４６】
表2の溶媒はいずれも双極子モーメントが0.6 Debye以下であった。
【００４７】
AM2001を溶解しない溶媒のうち水酸基、或いはカルボキシル基を有するものを表3に示す。AM2001は表2、表3に示す溶媒には不溶であり、AM2001と用いた溶媒を撹拌したものは放置すると2層に分離した。更にAM2001とは2層に分離せず混ざりあうものの完全には溶解せず混和する溶媒もあった。これらを表4に示す。表4の溶媒はいずれも双極子モーメントが0.6 Debyeより大きく且つ1.0 Debye以下であった。また分子内に水酸基、或いはカルボキシル基を有していなかった。抽出の際はまず良溶媒でAM2001を溶解し、更に貧溶媒を加えることで抽出物と非抽出物の2層に分かれさせる手順をとる。そのためAM2001抽出の際は良溶媒と貧溶媒の両方を用いることが必要となる。表1〜表4より良溶媒は双極子モーメントが1.0 Debye以上であり、且つ水酸基、或いはカルボキシル基を有しないものを選び、貧溶媒としては水酸基、或いはカルボキシル基を有するものか、水酸基、或いはカルボキシル基を有しない場合は双極子モーメントが0.6 Debye以下のものを選べばよいことがわかった。
【００４８】
次に精製方法を記述する。まず抽出操作を行う。
【００４９】
下式に示すAM2001（1重量部）
【００５０】
【化１】

【００５１】
に表5〜表10に示す種類の良溶媒を種々の重量加え、激しく撹拌する。
【００５２】
【表５】

【００５３】
【表６】

【００５４】
【表７】

【００５５】
【表８】

【００５６】
【表９】

【００５７】
【表１０】

【００５８】
これに表5〜表10に示す種類の貧溶媒を種々の重量加え、再び激しく撹拌後、数分間静置すると2層に分離しはじめた。12時間静置後、下層を採取し真空ポンプで減圧下、50℃で加熱し若干含まれている溶媒を揮発させる。こうして得られた非抽出物を化合物1から66とする。また化合物1から66の屈折率を表5〜表10に併記する。
【００５９】
この中で表5はAM2001に対して良溶媒として酢酸エチル（双極子モーメントが1.9Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）を種々の重量用いて抽出した際の非抽出物である。また表6はAM2001に対して良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）、或いはテトラヒドロフラン（双極子モーメントは1.6 Debye）、2-ブタノン（双極子モーメントは3.3 Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）、或いはn-ヘプタン（双極子モーメントは0 Debye）、n-オクタン（双極子モーメントは0 Debye）、トルエン（双極子モーメントは0.37 Debye）、o-キシレン（双極子モーメントは0.52 Debye）、1,2,3-トリメチルベンゼン（双極子モーメントは0.56 Debye）を種々の重量用いて抽出した際の非抽出物である。更に表7から表10はAM2001に対して良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）、或いはテトラヒドロフラン（双極子モーメントは1.6 Debye）、酢酸エチル（双極子モーメントが1.9Debye）、2-ブタノン（双極子モーメントは3.3 Debye）、貧溶媒として1-ペンタノール（双極子モーメントは0.89 Debye）、或いは2-オクタノール（双極子モーメントは1.6 Debye）、酢酸（双極子モーメントは2.0 Debye）、メタノール（双極子モーメントは2.9 Debye）、エタノール（双極子モーメントは3.0 Debye）、1,5−ペンタンジオール（双極子モーメントは3.8 Debye）、ペンタエチレングリコール（双極子モーメントは6.1 Debye）を種々の重量用いて抽出した際の非抽出物である。
【００６０】
次に減圧時加熱の精製操作を行う。AM2001（1重量部）と撹拌子をナス型フラスコに入れ、トラップを介して真空ポンプと接続する。トラップは液体窒素で冷却する。ナス型フラスコを油浴に浸し、引き続き撹拌子でナス型フラスコ内のAM2001の撹拌を始める。なお撹拌は内部を常圧に戻すまで続ける。内部を窒素ガスで置換した後真空ポンプで吸引を始める。ナス型フラスコ内は約0.02 Paに減圧する。次に油浴でナス型フラスコを80℃まで加熱する。するとナス型フラスコ中のAM2001の一部が揮発し始め、トラップ内に液体が溜まり始める。揮発がおさまった後加熱を停止し、ナス型フラスコを常温まで冷却する。ナス型フラスコを常圧に戻した後、撹拌を停止し、ナス型フラスコ内に残った液体を採取する。この液体を化合物67とする。化合物67の屈折率を測定したところ1.324であった。
【００６１】
次に末端にピペロニル基を有するパーフルオロポリエーテルを合成する。ピペロニルアルコール（15重量部）をピリジン（50重量部）に溶解し、これにp-トルエンスルホニルクロライド（20重量部）を加え、50℃で8時間撹拌する。冷却後、反応液を10重量％の塩酸（300重量部）に注ぐ。液性を確認し酸性でなければ酸性になるまで10重量％の塩酸を少しずつ加える。これを分液ロートに入れ、ジクロルメタン（300重量部）を加えた後、激しく撹拌し、そのまま放置すると2層に分かれる。下層のジクロルメタン層を分取し飽和食塩水で液性が中性になるまで洗浄する。無水硫酸ナトリウムで乾燥後、エバポレーターでジクロルメタンを揮発させる。これをシリカゲルカラムクロマトグラフィ（展開溶媒はn-ヘキサン：酢酸エチル＝2：1で精製し、ピペロニルアルコールの水酸基をトシル化した化合物（今後化合物68’と記述する）を20重量部得る。
【００６２】
次に末端に水酸基を有するパーフルオロポリエーテルの一つであるアウジモント社製のDOL-2000（20重量部）に5重量％の水酸化ナトリウムのメタノール溶液（16重量部）を加え、50℃で10分間撹拌後、エバポレーターでメタノールを揮発させる。これに化合物68’（6重量部）をジクロルメタン（30重量部）に溶解したものを加え、更に110℃で8時間撹拌する。冷却後、反応液に水（15重量部）、ジクロルメタン（15重量部）、3M社製PF-5052（100重量部）を加え激しく撹拌する。12時間放置後下層のPF-5052層を分取し、その中のPF-5052をエバポレーターで揮発させる。こうして末端の一部にピペロニル基を有するパーフルオロポリエーテル（20重量部）を得る。この化合物を今後化合物68（次式）と記述する。
【００６３】
【化２】

【００６４】
該化合物68の屈折率を測定したところ1.329であった。表1〜4に示す種々の溶媒に対する化合物68の溶解性を調べたところAM2001と同じ結果であった。
【００６５】
次に該化合物68をAM2001と同様に精製する。具体的には化合物68（1重量部）に表11〜16に示す種類の良溶媒を種々の重量加え、激しく撹拌する。これに表11〜表16に示す種類の貧溶媒を種々の重量加え、再び激しく撹拌後、数分間静置すると2層に分離しはじめる。12時間静置後、下層を採取し真空ポンプで減圧下、50℃で加熱し若干含まれている溶媒を揮発させる。こうして得られた非抽出物を化合物69から134とする。また化合物69から134の屈折率を表11〜表16に併記する。
【００６６】
【表１１】

【００６７】
【表１２】

【００６８】
【表１３】

【００６９】
【表１４】

【００７０】
【表１５】

【００７１】
【表１６】

【００７２】
この中で表11は化合物68に対して良溶媒として酢酸エチル（双極子モーメントが1.9Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）を種々の重量用いて抽出した際の非抽出物である。また表12は化合物68に対して良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）、或いはテトラヒドロフラン（双極子モーメントは1.6 Debye）、2-ブタノン（双極子モーメントは3.3 Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）、或いはn-ヘプタン（双極子モーメントは0 Debye）、n-オクタン（双極子モーメントは0 Debye）、トルエン（双極子モーメントは0.37 Debye）、o-キシレン（双極子モーメントは0.52 Debye）、1,2,3-トリメチルベンゼン（双極子モーメントは0.56 Debye）を種々の重量用いて抽出した際の非抽出物である。更に表13から表16は化合物68に対して良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）、或いはテトラヒドロフラン（双極子モーメントは1.6 Debye）、酢酸エチル（双極子モーメントが1.9Debye）、2-ブタノン（双極子モーメントは3.3 Debye）、貧溶媒として1-ペンタノール（双極子モーメントは0.89 Debye）、或いは2-オクタノール（双極子モーメントは1.6 Debye）、酢酸（双極子モーメントは2.0 Debye）、メタノール（双極子モーメントは2.9 Debye）、エタノール（双極子モーメントは3.0 Debye）、1,5−ペンタンジオール（双極子モーメントは3.8 Debye）、ペンタエチレングリコール（双極子モーメントは6.1 Debye）を種々の重量用いて抽出した際の非抽出物である。
【００７３】
次に減圧時加熱の精製操作を行う。化合物68（1重量部）と撹拌子をナス型フラスコに入れ、トラップを介して真空ポンプと接続する。トラップは液体窒素で冷却する。ナス型フラスコを油浴に浸し、引き続き撹拌子でナス型フラスコ内の化合物68の撹拌を始める。なお撹拌は内部を常圧に戻すまで続ける。内部を窒素ガスで置換した後真空ポンプで吸引を始める。ナス型フラスコ内は約0.02 Paに減圧する。次に油浴でナス型フラスコを80℃まで加熱する。するとナス型フラスコ中の化合物68の一部が揮発し始め、トラップ内に液体が溜まり始める。揮発がおさまった後加熱を停止し、ナス型フラスコを常温まで冷却する。ナス型フラスコを常圧に戻した後、撹拌を停止し、ナス型フラスコ内に残った液体を採取する。この液体を化合物135とする。化合物135の屈折率を測定したところ1.324であった。
【００７４】
上記操作で得られた化合物1〜135、及びAM2001を濃度が1000 ppmとなるように3M社製PF-5080で希釈した溶液を調製しておく。これを用いて磁気記録媒体を作製する。図1にその構成を示し、作製方法を以下に記述する。
【００７５】
直径3.5インチのAl合金製ディスク1の表面にNi-P層2（層厚：約15 μm）をメッキ法で形成する。次いでこの上にCr層3（層厚：約250 nm）、Ni-Co系磁性層4（層厚：約50 nm）、カーボン層5（層厚：約50 nm）をこの順にスパッタ蒸着法で形成した。このディスクを上記PF-5080溶液に1分間浸漬し、速度1 mm/s で引き上げた。その後常温で2時間放置してPF-5080を揮発させ、AM2001、及び上記抽出操作で作製した化合物1〜135からなる層6を表面に形成した磁気記録媒体を作製した。なお今後AM2001、或いは化合物1〜135からなる層6を潤滑層と記述する。この潤滑層の厚さは平均15Åである。
【００７６】
この磁気記録媒体の摺動特性をCSS試験法（コンタクトストップ法：試験機は小野田セメント（株）製）で評価した。条件は回転数：3600 rpm、1サイクル：30秒間、サイクル数：1000サイクル、ヘッド荷重：10 gであり、最終サイクルを終了し、6時間放置した後に再起動させた時の最大静止摩擦力を求めた。なお再起動時の回転数は1 rpmである。その結果、化合物1〜135を用いた磁気記録媒体の表面の摩擦力はいずれも8〜10 gの範囲であった。また上記抽出操作を全く行わないAM2001を塗布した磁気記録媒体の摩擦力を調べたところ9〜10 gであった。AM2001は磁気記録媒体用の潤滑剤として広く用いられているものであり、本発明の表面改質剤である化合物1〜135はAM2001とほぼ同様の摺動特性を示した。よって化合物1〜135は本発明の表面改質剤の特徴の１つである磁気記録媒体の潤滑剤としての特性を有していることが確かめられた。
【００７７】
次に上記磁気記録媒体を図2に示すハードディスクドライブにセットする。更にこのハードディスクドライブを構成物の一つとする図3の磁気記録装置によって上記磁気記録媒体を5400 rpm、或いは7200 rpmで200時間回転した後に10分間読み出しを行った。
【００７８】
すると化合物1〜135を塗布した磁気記録媒体のうち屈折率が1.324以下のものを塗布したものを装着した磁気記録装置ではどちらの回転数でもヘッドはクラッシュしなかったが、屈折率が1.324を超えるものを塗布したものを装着した磁気記録装置ではどちらの回転数でも読み出し開始後1分以内にヘッドがクラッシュし、読み出しが不可能となった。なお用いた化合物のうち屈折率が1.324以下のものは化合物1〜36、47〜52、67、69〜104、115〜120、135であり、屈折率が1.324を超えるものはAM2001、化合物37〜46、化合物53〜66、68、105〜114、121〜134である。ヘッドのクラッシュしなかったものは回転時の摩擦力が2 g以下であり、クラッシュしたものはいずれも回転時の摩擦力が5 g以上であり、摩擦力が高くなったことがヘッドクラッシュの原因となった。これら磁気記録媒体の200時間回転した後の潤滑層の厚さをIRの1300カイザーの吸光度から調べ、屈折率の同じ化合物ごとに潤滑層の平均の厚さを求めた結果を図4に示す。
【００７９】
各化合物からなる潤滑層の厚さはいずれもそれぞれの屈折率ごとの平均の厚さに対して±1Å以内の範囲に入っていた。屈折率が1.324以下の化合物からなる潤滑層は200時間回転後も初期膜厚の15Åの7割以上の11Å以上を確保していた。しかし屈折率が1.324より大きい化合物からなる潤滑層は200時間回転後、初期膜厚の4割以下の6Å以下になった。潤滑層が薄くなるということは媒体の回転によって潤滑層を構成している化合物が飛散するために起こる現象である。
【００８０】
6Å以下の平均膜厚になると表面上の部分的には化合物の全く存在しない箇所がでてくると考えられる。即ち潤滑層に部分的な欠陥が生じるためその潤滑性が大幅に低下しクラッシュを起こしたものと考えられる。
【００８１】
以上の結果より、ピペロニル基を有するパーフルオロポリエーテルを含有する表面改質剤において、該表面改質剤の屈折率が1.322以下であることを特徴とする表面改質剤は極めて低飛散性であるという効果が認められた。
【００８２】
またピペロニル基を有するパーフルオロポリエーテルが含有する膜を最外層として有することを特徴とする磁気記録媒体において、該パーフルオロポリエーテルの屈折率が1.322以下であることを特徴とする磁気記録媒体は200時間という長期の連続回転を行った後でも表面に十分な潤滑性を有するという効果が認められた。
【００８３】
更に情報の記録を行う磁気記録媒体と該磁気記録媒体への情報の書き込み・消去、及び該磁気記録媒体からの情報の読み出しを行うヘッドを有する磁気記録装置において、ピペロニル基を有するパーフルオロポリエーテルを含有する層が該磁気記録媒体の最表面にあり、且つ該パーフルオロポリエーテルの屈折率が1.322以下であることを特徴とする磁気記録装置は媒体を200時間という長期の連続回転を行った後でも情報の読み出しの際にヘッドがクラッシュせず正常な動作を行えるという効果が認められた。
【００８４】
なお使用したハードディスクの構成は以下の通りである。磁気記録媒体7が回転制御機構であるスピンドルモーター8の回転軸部分に固定されており、各磁気記録媒体7にはそれぞれ上面と下面とに記録・再生を行うための素子の組み込まれたヘッド9が設けられている。ヘッド9はヘッドサスペンション10を介してヘッド9の位置決め機構であるアクチュエーター11に接続されている。磁気記録媒体7、ヘッド9、ヘッドサスペンション10、アクチュエーター11は、メカニカルシール12によって外界から塵等が入り込まないように密封されている。磁気記録媒体と磁気記録装置の制御部（コントローラー）との情報信号のやりとり（転送）はヘッドとケーブル（データ信号転送用）13を介して行われる。アクチュエーターの制御はケーブル（アクチュエーター制御用）14を介し、スピンドルモーターの制御はケーブル（スピンドルモーター制御用）15を介して行われる。
【００８５】
また使用した磁気記録装置の構成は以下の通りである。ハードディスクドライブ16はケーブル（データ信号転送用、アクチュエーター制御用、スピンドルモーター制御用が一括して入っている）17を介してコントローラー18で制御される。コントローラーは電源ユニット19から電源ケーブル20を介して各々の部位を稼働させるための電気を得る。コントローラーは制御盤21で制御される。この間はケーブル22でつながっている。また装置の稼働状態はディスプレイ23によってモニターできる。コントローラーとディスプレイの間はケーブル24でつながっている。
【００８６】
【実施例２】
AM2001に対して良溶媒である双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、貧溶媒としてカルボキシル基、或いは水酸基を有する有機溶媒を用いて抽出した際の非抽出物を表7〜10に示す。
【００８７】
このうち表7に示されるのは良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）を種々の重量用いて抽出した際の非抽出物（化合物37〜43）である。表8に示されるのは良溶媒としてテトラヒドロフラン（双極子モーメントは1.6 Debye）を種々の重量用いて抽出した際の非抽出物（化合物44〜54）である。表9に示されるのは良溶媒として酢酸エチル（双極子モーメントは1.9 Debye）を種々の重量用いて抽出した際の非抽出物（化合物55〜60）である。表10に示されるのは良溶媒として2-ブタノン（双極子モーメントは3.3 Debye）を種々の重量用いて抽出した際の非抽出物（化合物61〜66）である。またこれらの化合物の抽出の際のAM2001の貧溶媒としては1-ペンタノール（双極子モーメントは0.89 Debye）、或いは2-オクタノール（双極子モーメントは1.6 Debye）、酢酸（双極子モーメントは2.0 Debye）、メタノール（双極子モーメントは2.9 Debye）、エタノール（双極子モーメントは3.0 Debye）、1,5−ペンタンジオール（双極子モーメントは3.8 Debye）、ペンタエチレングリコール（双極子モーメントは6.1 Debye）を用いた。
【００８８】
次に化合物67に対して良溶媒である双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、貧溶媒としてカルボキシル基、或いは水酸基を有する有機溶媒を用いて抽出した際の非抽出物を表13〜表16に示す。
【００８９】
このうち表13に示されるのは良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）を種々の重量用いて抽出した際の非抽出物（化合物105〜111）である。表14に示されるのは良溶媒としてテトラヒドロフラン（双極子モーメントは1.6 Debye）を種々の重量用いて抽出した際の非抽出物（化合物112〜122）である。表15に示されるのは良溶媒として酢酸エチル（双極子モーメントは1.9 Debye）を種々の重量用いて抽出した際の非抽出物（化合物123〜128）である。表16に示されるのは良溶媒として2-ブタノン（双極子モーメントは3.3 Debye）を種々の重量用いて抽出した際の非抽出物（化合物129〜134）である。またこれらの化合物の抽出の際のAM2001の貧溶媒としては1-ペンタノール（双極子モーメントは0.89 Debye）、或いは2-オクタノール（双極子モーメントは1.6 Debye）、酢酸（双極子モーメントは2.0 Debye）、メタノール（双極子モーメントは2.9 Debye）、エタノール（双極子モーメントは3.0 Debye）、1,5−ペンタンジオール（双極子モーメントは3.8 Debye）、ペンタエチレングリコール（双極子モーメントは6.1 Debye）を用いた。またそれぞれの化合物の屈折率を併記する。
【００９０】
まず屈折率測定の結果、表7〜表10に示される化合物37〜66のうち良溶媒としてテトラヒドロフラン、貧溶媒としてメタノールを組み合わせた場合の非抽出物（化合物47〜52）の屈折率は1.324であった。それ以外の組み合わせでは屈折率は1.325以上であった。
【００９１】
次に実施例1と同様の方法で作製した化合物37〜67、及び105〜135、AM2001（屈折率は1.328）、化合物68（屈折率は1.329）を塗布した磁気記録媒体表面を倍率1000倍の光学顕微鏡で観察したところ、これらの表面は平坦であり異物は観測されなかった。これらの磁気記録媒体を槽内部が70℃に調節された恒温槽に10時間放置後、その表面を観察した。結果を表17に示す。化合物37〜46、及び53〜66、68、105〜114、121〜134、AM2001を塗布した磁気記録媒体表面には面積が1〜100平方ミクロンメートル程度の大きさの斑点が1平方ミリメートルあたりおよそ1〜10個程度見られた。この斑点を顕微IRで分析すると1630カイザー近傍にベンゾキノンのカルボニル基由来と推定される吸収が観測された。しかし化合物47〜52、及び67、115〜120、135を塗布した磁気記録媒体表面は70℃の恒温槽に放置後も平坦であり、異物は観測されなかった。
【００９２】
次に上記の恒温槽による加熱を行った磁気記録媒体を実施例1と同様の磁気記録装置にセットして情報の読み出しを行ったところ、70℃の恒温槽に放置後も異物が観測されなかった化合物47〜52、及び67、115〜120、135を塗布した磁気記録媒体はエラーの発生がなかったが、残る化合物である化合物37〜46、及び53〜66、68、105〜114、121〜134、AM2001を塗布した磁気記録媒体はいずれも読み出しの際にエラーが発生した。エラーの発生した箇所の表面を調べたところいずれも恒温槽による加熱で発生した斑点の発生部分であった。
【００９３】
次に下地をスパッタ法で作製したカーボンから酸化珪素に代えた場合の加熱による表面の平滑性の変化の有無を調べた。実施例1で調製した化合物37〜67、及び105〜135、AM2001、化合物68のPF-5080溶液を磁気記録媒体作製の際と同様の方法で鏡面研磨した直径3.5インチのシリコンウエハーに塗布する。塗布表面を磁気記録媒体表面観察時と同様に光学顕微鏡で観察し、次に槽内部が70℃に調節された恒温槽に10時間放置後、再び表面を観察した。結果を表18に示す。磁気記録媒体表面観察時と同様に化合物47〜52、及び67、115〜120、135を塗布したシリコンウエハー表面は70℃の恒温槽に放置後も平坦であり異物は観測されなかった。しかし残る化合物である化合物37〜46、及び53〜66、68、105〜114、121〜134、AM2001を塗布したシリコンウエハー表面には面積が1〜100平方ミクロンメートル程度の大きさの斑点が1平方ミリメートルあたりおよそ1〜10個程度見られた。これら化合物はいずれも屈折率が1.324を超えるものである。この斑点を顕微IRで分析すると1630カイザー近傍にベンゾキノンのカルボニル基由来と推定される吸収が観測された。また恒温槽に放置する前、化合物37〜66、及び105〜134、AM2001、化合物68を塗布したシリコンウエハー表面の水との接触角は105〜110°であった。また化合物67と134の場合は100°であった。このうち化合物47〜52、及び67、115〜120、135を塗布したシリコンウエハーの接触角は80℃中に10時間放置後も変化がなかった。しかし残る化合物である化合物37〜46、及び53〜66、105〜114、121〜134、AM2001、化合物68を塗布したシリコンウエハーの接触角は70℃中に10時間放置後には88〜95°に低下した。なお化合物37〜66、及び105〜134、AM2001、化合物68を塗布する前の鏡面研磨した直径3.5インチのシリコンウエハーの接触角は約60°であった。
【００９４】
以上の結果より、屈折率1.322以下のピペロニル基を有するパーフルオロポリエーテルを含有する表面改質剤は同様の構造で屈折率が1.322より大きなものに比べて耐熱性もあるという効果が確認された。
【００９５】
また同じ屈折率1.324の値を示す場合でも減圧時加熱する方法で得られた化合物67、135に比べ、抽出法で得られた化合物47〜52、及び115〜120の方が表面の撥水性が高い。
【００９６】
この結果より、屈折率1.324以下のピペロニル基を有するパーフルオロポリエーテルを含有する表面改質剤の中でも該表面改質剤がテトラヒドロフランとメタノールをそれぞれピペロニル基を有するパーフルオロポリエーテルの0.5〜20倍の重量を用いて抽出した際の非抽出分からなることを特徴とするものは高い撥水性を持った表面を形成できるという効果が確認された。
【００９７】
【実施例３】
AM2001に対して良溶媒である双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、貧溶媒として双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒を用いて抽出した際の非抽出物を表5、6に示す。このうち表5に示されるのは良溶媒として酢酸エチル（双極子モーメントは1.9Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）を種々の重量用いて抽出した際の非抽出物（化合物1〜10）である。また表6に示されるのはAM2001に対して良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）、或いはテトラヒドロフラン（双極子モーメントは1.6 Debye）、2-ブタノン（双極子モーメントは3.3 Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）、或いはn-ヘプタン（双極子モーメントは0 Debye）、n-オクタン（双極子モーメントは0 Debye）、トルエン（双極子モーメントは0.37 Debye）、o-キシレン（双極子モーメントは0.52 Debye）、1,2,3-トリメチルベンゼン（双極子モーメントは0.56 Debye）を種々の重量用いて抽出した際の非抽出物（化合物11〜36）である。
【００９８】
また化合物68に対して良溶媒である双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、貧溶媒として双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒を用いて抽出した際の非抽出物を表11、12に示す。このうち表11は良溶媒として酢酸エチル（双極子モーメントは1.9Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）を種々の重量用いて抽出した際の非抽出物（化合物69〜78）である。また表12はAM2001に対して良溶媒としてクロロホルム（双極子モーメントは1.0 Debye）、或いはテトラヒドロフラン（双極子モーメントは1.6 Debye）、2-ブタノン（双極子モーメントは3.3 Debye）、貧溶媒としてn-ヘキサン（双極子モーメントは0 Debye）、或いはn-ヘプタン（双極子モーメントは0 Debye）、n-オクタン（双極子モーメントは0 Debye）、トルエン（双極子モーメントは0.37 Debye）、o-キシレン（双極子モーメントは0.52 Debye）、1,2,3-トリメチルベンゼン（双極子モーメントは0.56 Debye）を種々の重量用いて抽出した際の非抽出物（化合物79〜104）である。化合物1〜36、及び69〜104はいずれも屈折率が1.324以下である。
【００９９】
実施例1で作製した化合物1〜36、及び69〜104、AM2001、化合物68を塗布した磁気記録媒体表面を倍率1000倍の光学顕微鏡で観察したところ、この表面は平坦であり異物は観測されなかった。これらの磁気記録媒体を槽内部が80℃に調節された恒温槽に10時間放置後、その表面を観察した。なお比較のため実施例2で用いた化合物37〜67、及び105〜135を塗布した磁気記録媒体も上記化合物を塗布した磁気記録媒体と同様に80℃に調節された恒温槽に10時間放置後、その表面を観察した。結果を表17に示す。
【０１００】
AM2001、及び化合物37〜68、105〜135を塗布した磁気記録媒体表面には面積が1〜100平方ミクロンメートル程度の大きさの斑点が1平方ミリメートルあたりおよそ1〜10個程度見られた。この斑点を顕微IRで分析すると1630カイザー近傍にベンゾキノンのカルボニル基由来と推定される吸収が観測された。しかし化合物1〜36、及び69〜104を塗布した磁気記録媒体表面は80℃の恒温槽に放置後も平坦であり、異物は観測されなかった。
【０１０１】
次に上記の恒温槽による加熱を行った磁気記録媒体を実施例1と同様の磁気記録装置にセットして情報の読み出しを行ったところ、80℃の恒温槽に放置後も異物が観測されなかった化合物1〜36、及び69〜104を塗布した磁気記録媒体はエラーの発生がなかったが、残る化合物であるAM2001、及び化合物37〜68、105〜135を塗布した磁気記録媒体はいずれも読み出しの際にエラーが発生した。エラーの発生した箇所の表面を調べたところいずれも恒温槽による加熱で発生した斑点の発生部分であった。
【０１０２】
次に下地をスパッタ法で作製したカーボンから酸化珪素に代えた場合の加熱による表面の平滑性の変化の有無を調べた。実施例1で調製したAM2001、及び化合物1〜36、68〜104のPF-5080溶液を磁気記録媒体作製の際と同様の方法で鏡面研磨した直径3.5インチのシリコンウエハーに塗布する。塗布表面を磁気記録媒体表面観察時と同様に光学顕微鏡で観察し、次に槽内部が80℃に調節された恒温槽に10時間放置後、再び表面を観察した。なお磁気記録媒体の場合と同様、比較のため実施例2で用いた化合物37〜67、及び105〜135を塗布したシリコンウエハーも上記化合物を塗布したシリコンウエハーと同様に80℃に調節された恒温槽に10時間放置後、その表面を観察した。結果を表18に示す。
【０１０３】
化合物1〜36、及び69〜104を塗布したシリコンウエハー表面は80℃の恒温槽に放置後も平坦であり異物は観測されなかった。しかし残る化合物であるAM2001、及び化合物37〜68、105〜135を塗布したシリコンウエハー表面には面積が1〜100平方ミクロンメートル程度の大きさの斑点が1平方ミリメートルあたりおよそ1〜10個程度見られた。この斑点を顕微IRで分析すると1630カイザー近傍にベンゾキノンのカルボニル基由来と推定される吸収が観測された。また恒温槽に放置する前、用いた化合物を塗布したシリコンウエハー表面の水との接触角は100〜110°であった。このうち化合物1〜36、及び69〜104を塗布したシリコンウエハーの接触角は80℃中に10時間放置後も変化がなかった。しかし残る化合物であるAM2001、及び化合物37〜68、105〜135を塗布したシリコンウエハーの接触角は80℃中に10時間放置後には88〜95°に低下した。
【０１０４】
実施例2において、テトラヒドロフランとメタノールをそれぞれ該表面改質剤の0.5〜20倍の重量を用いて抽出した際の非抽出分である化合物47〜52、及び115〜120を塗布した磁気記録媒体、及びシリコンウエハーは70℃の耐熱温度のあることが確認された。しかし本実施例においてこれら化合物を塗布した磁気記録媒体、及びシリコンウエハーは80℃の耐熱性はないことがわかった。一方、双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒をそれぞれ該表面改質剤の0.5〜20倍の重量を用いて抽出した際の非抽出分である化合物1〜36、及び69〜104を塗布した磁気記録媒体、及びシリコンウエハーの方が耐熱性の高いということが確認された。
【０１０５】
以上より、屈折率1.322以下のピペロニル基を有するパーフルオロポリエーテルを含有する表面改質剤において、該表面改質剤が双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒をそれぞれピペロニル基を有するパーフルオロポリエーテルの0.5〜20倍の重量を用いて抽出した際の非抽出分からなることを特徴とするものは80℃中に放置されても塗布面は平坦性を保ち、且つ撥水性を保持するという効果を有する熱安定性の高い表面改質剤であることが認められた。
【０１０６】
また、支持体上に少なくとも1層以上の記録層を備え、該記録層、或いは該記録層の外側に備えた保護層表面に屈折率1.324以下のピペロニル基を有するパーフルオロポリエーテルが含有する膜を最外層として有することを特徴とする磁気記録媒体において、該パーフルオロポリエーテルが双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒をそれぞれピペロニル基を有するパーフルオロポリエーテルの0.5〜20倍の重量を用いて抽出した際の非抽出分からなることを特徴とするものは熱安定性が高く80℃中に放置されても読み出しの際のエラーの発生を起こすことがないという効果を有する磁気記録媒体であることが認められた。
【０１０７】
【実施例４】
実施例1と同じ方法で化合物1〜135とAM2001を塗布した磁気記録媒体を作製し、恒温槽の温度を90℃にする以外は実施例1と同様に恒温槽に10時間放置後、その表面を観察した。結果を表17に示す。
【０１０８】
【表１７】

【０１０９】
化合物4〜6、及び72〜74を塗布した磁気記録媒体表面は恒温槽に放置後も平坦であり異物は観測されなかった。しかし残る化合物であるAM2001、化合物1〜3、7〜71、75〜135を用いた磁気記録媒体は面積が1〜100平方ミクロンメートル程度の大きさの斑点が1平方ミリメートルあたりおよそ1〜10個程度見られた。この斑点を顕微IRで分析すると1630カイザー近傍にベンゾキノンのカルボニル基由来と推定される吸収が観測された。
【０１１０】
次に上記の恒温槽による加熱を行った磁気記録媒体を実施例1と同様の磁気記録装置にセットして情報の読み出しを行ったところ、化合物4〜6、及び72〜74を塗布した磁気記録媒体はエラーの発生が見られなかった。しかしAM2001、化合物1〜3、7〜71、75〜135を塗布した磁気記録媒体はいずれも読み出しの際にエラーが発生した。エラーの発生した箇所の表面を調べたところいずれも恒温槽による加熱で発生した斑点の発生部分であった。
【０１１１】
次に下地をスパッタ法で作製したカーボンから酸化珪素に代えた場合の加熱による表面の平滑性の変化の有無を調べた。実施例1と同じ方法で化合物1〜135とAM2001を塗布したシリコンウエハーを作製し、恒温槽の温度を90℃にする以外は実施例1と同様に恒温槽に10時間放置後、その表面を観察した。結果を表18に示す。
【０１１２】
【表１８】

【０１１３】
化合物4〜6、及び72〜74を塗布したシリコンウエハー表面は90℃の恒温槽に放置後も平坦であり異物は観測されなかった。しかし残る化合物であるAM2001、化合物1〜3、7〜71、75〜135を塗布したシリコンウエハー表面には面積が1〜100平方ミクロンメートル程度の大きさの斑点が1平方ミリメートルあたりおよそ1〜10個程度見られた。この斑点を顕微IRで分析すると1630カイザー近傍にベンゾキノンのカルボニル基由来と推定される吸収が観測された。また恒温槽に放置する前、用いた化合物を塗布したシリコンウエハー表面の水との接触角は100〜110°であった。このうち化合物4〜6、及び72〜74を塗布したシリコンウエハーの接触角は90℃中に10時間放置後も変化がなかった。しかし残る化合物であるAM2001、化合物1〜3、7〜71、75〜135を塗布したシリコンウエハーの接触角は90℃中に10時間放置後には88〜95°に低下した。
【０１１４】
実施例3において、該表面改質剤が双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒をそれぞれ該表面改質剤の0.5〜20倍の重量を用いて抽出した際の非抽出分からなることを特徴とする化合物1〜36、及び69〜104を塗布した磁気記録媒体、及びシリコンウエハーは80℃の耐熱温度のあることが確認されている。更に本実施例において化合物1〜36、及び69〜104のうち抽出の際、該表面改質剤1重量部に対して酢酸エチルを1重量部とn-ヘキサンを2.5〜6重量部を用いて抽出した際の非抽出分からなることを特徴とするもの（化合物4〜6、及び72〜74）は90℃の耐熱性のあることが確認された。
【０１１５】
以上より、屈折率1.322以下のピペロニル基を有するパーフルオロポリエーテルを含有する表面改質剤において、該表面改質剤がピペロニル基を有するパーフルオロポリエーテル1重量部に対して酢酸エチルを1重量部とn-ヘキサンを2.5〜6重量部を用いて抽出した際の非抽出分からなることを特徴とするものは90℃中に放置されても塗布面は平坦性を保ち、且つ撥水性を保持するという効果を有する熱安定性の高い表面改質剤であることが認められた。
【０１１６】
また、支持体上に少なくとも1層以上の記録層を備え、該記録層、或いは該記録層の外側に備えた保護層表面に屈折率1.322以下のピペロニル基を有するパーフルオロポリエーテルが含有する膜を最外層として有することを特徴とする磁気記録媒体において、該パーフルオロポリエーテルがピペロニル基を有するパーフルオロポリエーテル1重量部に対して酢酸エチルを1重量部とn-ヘキサンを2.5〜6重量部を用いて抽出した際の非抽出分からなることを特徴とするものは90℃中に放置されても塗布面は読み出しの際のエラーの発生を起こす斑点を生じないため熱安定性の高いという効果を有する磁気記録媒体であることが認められた。
【０１１７】
【実施例５】
実施例1と同じ方法で化合物1〜135とAM2001を塗布した磁気記録媒体を作製し、図2に示すハードディスクドライブにセットし、図3に示す構成の磁気記録装置によって種々の回転数で磁気記録媒体を10時間回転後、情報の読み出しを行った。なおヘッドと磁気記録媒体の平均距離は50 nmに設定した。結果を表19に示す。
【０１１８】
【表１９】

【０１１９】
従来の磁気記録装置の回転数である5400 rpmではいずれの化合物を用いた磁気記録媒体もエラーの発生はなかった。回転数7200 rpmでは化合物1〜36、47〜52、67、69〜104、115〜120、135を塗布した磁気記録媒体はエラーの発生は見られなかったが、AM2001、化合物37〜46、53〜66、68、105〜114、121〜134を塗布した磁気記録媒体は信号にエラーが発生した。回転数8400 rpmでは化合物1〜36、69〜104を塗布した磁気記録媒体はエラーの発生は見られなかったが、AM2001、化合物37〜68、105〜135を塗布した磁気記録媒体はいずれも読み出しの際にエラーが発生した。更に回転数9600 rpmでは化合物4〜6、72〜74を塗布した磁気記録媒体はエラーの発生は見られなかったが、AM2001、化合物1〜3、7〜71、75〜135を塗布した磁気記録媒体はいずれも読み出しの際にエラーが発生した。
【０１２０】
磁気記録媒体を装置からはずしその表面を観察したところエラーを生じたものはいずれも実施例1〜4の恒温槽による加熱で発生したものと同様の斑点が発生していた。またこの斑点の発生部分がエラーの発生した箇所と対応していた。
【０１２１】
これらを用いた表面改質剤の屈折率でみると以下のようになる。屈折率1.324以下の表面改質剤を用いた装置は回転数7200 rpmという高速での情報の読み出しが可能であるという効果が認められた。またその中で屈折率1.322以下の表面改質剤を用いた装置は回転数8400 rpmという高速での情報の読み出しが可能であるという効果が認められた。更にその中で屈折率1.315以下の表面改質剤を用いた装置は回転数9600 rpmという高速での情報の読み出しが可能であるという効果が認められた。
【０１２２】
続いて用いた磁気記録媒体の最表面層を形成している化合物の精製方法の違いで効果をまとめると以下のようになる。用いた表面改質剤が化合物47〜52、115〜120の場合の結果より、ピペロニル基を有するパーフルオロポリエーテルをテトラヒドロフランと、メタノールをそれぞれ該パーフルオロポリエーテルの0.5〜20倍の重量を用いて抽出した際の非抽出分からなる成分を磁気記録媒体表面に有する磁気記録装置は回転数7200 rpmを許容できるという効果が認められた。
【０１２３】
また用いた表面改質剤が化合物1〜36、69〜104の場合の結果より、ピペロニル基を有するパーフルオロポリエーテルを双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒と、双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒をそれぞれ該パーフルオロポリエーテルの0.5〜20倍の重量を用いて抽出した際の非抽出分からなる成分を磁気記録媒体表面に有する磁気記録装置は回転数8400 rpmを許容できるという効果が認められた。
【０１２４】
更に用いた表面改質剤が化合物4〜6、72〜74の場合の結果より、ピペロニル基を有するパーフルオロポリエーテルを双極子モーメントが1.0Debye以上であり且つカルボキシル基と水酸基を有しない有機溶媒として酢酸エチルをパーフルオロポリエーテルと同重量用い、双極子モーメントが0〜0.6 Debyeの範囲内にあり且つカルボキシル基と水酸基を有しない有機溶媒としてn-ヘキサンをパーフルオロポリエーテルの2.5〜6倍の重量用いて抽出した際の非抽出分からなる成分を磁気記録媒体表面に有する磁気記録装置は回転数9600 rpmを許容できるという効果が認められた。
【０１２５】
【発明の効果】
本発明により、末端にピペロニル基を有するパーフルオロポリエーテル構造を有する表面改質剤のうち、極めて低飛散性の表面改質剤を提供することが可能となった。加えて熱安定性、及び撥水性の高い表面改質剤を提供することも可能となった。
【０１２６】
また本発明により、長期の連続回転を行った後でも表面に十分な潤滑性を有する磁気記録媒体を提供することが可能となった。加えて熱安定性の高い磁気記録媒体を提供することも可能となった。
【０１２７】
更に本発明により、長期の連続回転を行ってもヘッドがクラッシュせず正常に動作する磁気記録装置を提供することが可能となった。
【図面の簡単な説明】
【図１】 実施例1で作製した磁気記録媒体の構成を示す断面模式図である。
【図２】 実施例1で作製した磁気記録装置内のハードディスクドライブの構成を示す断面模式図である。
【図３】 実施例1で作製した磁気記録装置の構成を示す模式図である。
【図４】 潤滑層を構成している化合物の屈折率と潤滑層の厚さの関係を示す図である。
【符号の説明】
1…Al合金製ディスク、2…Ni-P層、3…Cr層、4…Ni-Co系磁性層、5…カーボン層、6…表面改質剤からなる層、7…磁気記録媒体、8…スピンドルモーター、9…ヘッド、10…ヘッドサスペンション、11…アクチュエーター、12…メカニカルシール、13…ケーブル（データ信号転送用）、14…ケーブル（アクチュエーター制御用）、15…ケーブル（スピンドルモーター制御用）、16…ハードディスクドライブ、17…ケーブル（データ信号転送用、アクチュエーター制御用、スピンドルモーター制御用が一括して入っている）、18…コントローラー、19…電源ユニット、20…電源ケーブル、21…制御盤、22…ケーブル、23…ディスプレイ、24…ケーブル。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface modifier, a magnetic recording medium and a magnetic recording apparatus using the same, and more particularly to a surface modifier for the purpose of improving the thermal stability of a magnetic recording medium.
[0002]
[Prior art]
As the recording density of the magnetic recording apparatus increases, the distance between the recording medium and the head that transfers the recording between the recording medium and the recording medium decreases until it almost comes into contact. For this reason, a lubricating layer is provided on the surface of the recording medium for the purpose of suppressing wear during contact and sliding with the head. The lubricating layer is usually formed by applying a surface modifier having lubricity to the surface of a recording medium. At present, the surface modifier is mainly a derivative based on perfluoropolyether having a low scattering property and good sliding properties. In addition, a compound having a piperonyl group at the end of the chemical structure of the perfluoropolyether in order to enhance the adsorptivity to the recording medium surface is disclosed (Japanese Patent Laid-Open No. 61-4727).
[0003]
By the way, during continuous operation of the magnetic recording apparatus, the temperature of the recording medium in the apparatus and the storage portion of the head becomes considerably high due to a heat generation source such as a motor for rotating the recording medium. In the case of a magnetic recording device, the rotational speed is about 60 ° C. at 5400 rpm and about 70 ° C. at 7200 rpm, although it varies slightly depending on the device.
[0004]
In the future, the rotational speed tends to be further increased due to an increase in transfer speed, and the recording medium and the head will be exposed to higher temperatures. For this reason, it is desired that the surface modifier does not change so as to hinder the transfer of the information signal even if it is exposed to a high temperature for a long time. Specifically, it is required that the lubricating layer does not become thin and the constituent components of the lubricating layer do not denature. Further, the heat resistant temperature is required to be 70 ° C. for a 7200 rpm device, 80 ° C. for an 8400 rpm device, and 90 ° C. for a 9600 rpm device.
[0005]
[Problems to be solved by the invention]
Perfluoropolyether having a piperonyl group at the end changes its appearance from colorless and transparent to brown when left at 70 ° C. or higher for a long time. This is presumably because the cyclic ether moiety in the terminal piperonyl group is cleaved and oxidized to be converted into a benzoquinone derivative. When the recording medium coated with perfluoropolyether having a piperonyl group at the end is left at 70 ° C., the surface of the recording medium is observed with an optical microscope while irradiating visible light obliquely, and the size is about 1 to 100 square microns. Spots are seen. When this speckle is analyzed by microscopic IR, absorption that is thought to be derived from the stretching vibration of the carbonyl group of the benzoquinone derivative is observed. When information is transferred using a recording medium in which the spots are generated, an error occurs when reading the portion where the spots are present. This is considered to be caused by the fact that the heat generated when the head contacts the speckled part affects the readout signal. Therefore, there has been a demand for a highly heat-stable surface modifier that can withstand the heat generated with an increase in the number of revolutions in the future.
[0006]
  Further, when the magnetic recording medium is rotated at a high speed over a long period of time, the lubricant layer (lubricant layer) becomes thinner. This is because the lubricant is scattered. When the lubricant layer becomes thin, sufficient lubricity cannot be obtained, so that the medium is damaged and reading of recorded information is disturbed. Therefore, a lubricant that does not easily scatter has been demanded.
  An object of the present invention is to provide a surface modifying agent, a magnetic recording medium, and a magnetic recording apparatus that are made of a lubricant that has high thermal stability and is difficult to scatter.
[0007]
[Means for Solving the Problems]
  As a result of intensive studies on perfluoropolyethers having a piperonyl group at the end in order to solve the above-mentioned problems, we have found that those having a low refractive index have high thermal stability and low scattering properties. Specifically, the refractive index is 1.32.2When the following were used, it discovered that the said subject could be solved and came to the present invention.AndThose with a refractive index of 1.322 or less are more thermally stableButTo improveTheI found it. In order to obtain a low refractive index, it is effective to perform an extraction operation using an organic solvent, which will be described later. Particularly, as a method of reducing the refractive index to 1.322 or less, the dipole moment is 1.0 Debye or more and a carboxyl group and It has also been found effective to use an organic solvent having no hydroxyl group and an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and no hydroxyl group.
[0008]
In addition, perfluoropolyether having a piperonyl group at the terminal also has an effect of increasing the water repellency of the solid surface. However, if the solid on which the coating is applied is left in a place at a temperature of about 70 ° C. for a long time, the water repellency of the coated surface tends to decrease. However, by using a material having a low refractive index, it has become possible to prevent a decrease in water repellency.
[0009]
The gist of the present invention is described below.
[0010]
(1) Surface modifier containing perfluoropolyether having a piperonyl groupAnd
The perfluoropolyether is
The dipole moment is 1.0Debye An organic solvent having no carboxyl group and no hydroxyl group and a dipole moment 0 ~ 0.6Debye And an organic solvent having no carboxyl group and no hydroxyl group in the range of
The perfluoropolyether isRefractive index is 1.32.2A surface modifier characterized by:
[0011]
(2) In the perfluoropolyether having a piperonyl group described in (1), when the surface modifier extracts tetrahydrofuran and methanol using 0.5 to 20 times the weight of the perfluoropolyether having a piperonyl group, respectively. Consisting of non-extractedIs preferred.
[0012]
(3) In the surface modifier according to (1),The perfluoropolyether isAn organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and a hydroxyl group, and an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and a hydroxyl groupWhenEachSaidA surface modifier comprising a non-extracted portion when extracted using 0.5 to 20 times the weight of perfluoropolyether.
[0013]
(4) In the surface modifier according to (3),The perfluoropolyether is
SaidEthylacetate as an organic solvent with a dipole moment of 1.0 Debye or higher and no carboxyl and hydroxyl groupsLeUse
  SaidAs an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and no hydroxyl groupn- Using hexane,
  Using the same amount of ethyl acetate as the perfluoropolyether,
  Saidn-hexaneSaidUse 2.5 to 6 times the weight of perfluoropolyetherConsisting of non-extracted components
A surface modifier characterized by that.
[0014]
(5) At least one recording layer is provided on the support, and a film containing a perfluoropolyether having a piperonyl group is formed on the surface of the recording layer or a protective layer provided outside the recording layer. As a magnetic recording mediumBecause,
The perfluoropolyether is
The dipole moment is 1.0Debye An organic solvent having no carboxyl group and no hydroxyl group and a dipole moment 0 ~ 0.6Debye And an organic solvent having no carboxyl group and no hydroxyl group in the range of
And saidPerfluoropolyetherIsRefractive index is 1.32.2Is
A magnetic recording medium characterized by the above.
[0015]
(6) In the magnetic recording medium described in (5),SaidPerfluoropolyetherIs
  SaidAn organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and a hydroxyl group, and an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and a hydroxyl group, respectivelySaidA magnetic recording medium comprising a non-extracted portion when extracted with a weight of 0.5 to 20 times that of perfluoropolyether.
[0016]
(7) In the magnetic recording medium described in (6),The perfluoropolyether is
  The dipoleEthyl acetate as an organic solvent having a moment of 1.0 Debye or more and having no carboxyl group and no hydroxyl groupUse
  SaidN-Hexane as an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and no hydroxyl groupUse
  Using the same amount of ethyl acetate as the perfluoropolyether,
  Said n- HexaneUse 2.5 to 6 times the weight of perfluoropolyetherFrom the non-extracted portionA magnetic recording medium.
[0017]
(8) In a magnetic recording apparatus having at least a magnetic recording medium for recording information and a head for writing / erasing information on the magnetic recording medium and reading information from the magnetic recording medium,
  A layer containing a perfluoropolyether having a piperonyl group is on the outermost surface of the magnetic recording medium;
The perfluoropolyether is
The dipole moment is 1.0Debye An organic solvent having no carboxyl group and no hydroxyl group and a dipole moment 0 ~ 0.6Debye And an organic solvent having no carboxyl group and no hydroxyl group in the range of
And saidPerfluoropolyether has a refractive index of 1.32.2Is
A magnetic recording medium characterized by the above.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
(1) About the surface modifier of the present invention
(1-a) Purification method
First, purification of perfluoropolyether having a piperonyl group at the end of the present invention will be described. Examples of the purification include an extraction method and a method using heating under reduced pressure. First, the extraction method is described. The extraction method is performed by using a good solvent and a poor solvent for the perfluoropolyether having a piperonyl group. First, perfluoropolyether having a piperonyl group at the end is dissolved in a good solvent. Subsequently, when the poor solvent is put into a separating funnel and allowed to stand after stirring, it is separated into two layers in several hours. The lower layer is collected, and the mixed solvent contained is evaporated by an evaporator or a vacuum pump. The above operation is described as extraction in the present invention. It is assumed that the organic solvent used for extraction is liquid at room temperature.
[0019]
  Of the two layers produced by standing after stirring during the above operation, the upper layer is a layer composed mainly of a mixed solvent of an organic solvent, and the lower layer is a layer composed mainly of a perfluoropolyether having a piperonyl group. is there. This is because the specific gravity of the perfluoropolyether having a piperonyl group is larger than the specific gravity of the mixed solvent. In the present invention, perfluoropolyether having a piperonyl group contained in the upper layer is defined as an extractable portion, and perfluoropolyether having a piperonyl group contained in the lower layer is defined as a non-extractable portion. The refractive index of perfluoropolyether having a piperonyl group before extraction is 1.328-1.330. The refractive index of the extracted part was higher than this, and the non-extracted part was lower. In addition, the target refractive index of 1.32 can be obtained by adjusting the type and ratio of the extraction solvent.2A perfluoropolyether having the following piperonyl group can be obtained.
[0020]
As a solvent used for extraction, a solvent that is a good solvent and a poor solvent for AM2001 is used. Those with high polarity tend to be good solvents, and those with low polarity tend to be poor solvents. However, an organic solvent having a carboxyl group or a hydroxyl group has a high polarity but is a poor solvent and has the following problems. The polarity corresponds to the dipole moment, and the greater the dipole moment, the higher the polarity. It is desirable that the good solvent has a dipole moment of 1.0 Debye or more, and the poor solvent has a dipole moment of 0.6 Debye or less. Organic solvents having a dipole moment of 1.0 Debye or more and having no carboxyl group and no hydroxyl group include chloroform (1.0 Debye), tetrahydrofuran (1.6 Debye), ethyl acetate (1.9 Debye), pyridine (2.3 Debye), 2-butanone ( 3.3 Debye). These solvents dissolve partially or completely perfluoropolyethers having piperonyl groups. The organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and no hydroxyl group includes 1,2,3-trimethylbenzene (0.56 Debye), o-xylene (0.52 Debye), toluene (0.37 Debye), ethylbenzene (0.36 Debye), m-xylene (0.31 Debye), n-hexane (0 Debye), n-heptane (0 Debye), n-octane (0 Debye), benzene (0 Debye), p-xylene (0 Debye). These solvents hardly dissolve perfluoropolyethers having piperonyl groups. An organic solvent having a dipole moment exceeding 0.6 Debye and less than 1.0 Debye and having no carboxyl group and no hydroxyl group is miscible with perfluoropolyether having a piperonyl group. Therefore, the extraction operation is not suitable in the present invention because it is not divided into two layers. Solvents that fall within this category include cyclohexene (0.61 Debye), triethylamine (0.73 Debye), bromoform (0.92 Debye), isoamyl ether (0.98 Debye), and the like.
[0021]
In addition to the dipole moment, the boiling point and heat of vaporization are also points for selection as the solvent to be used. For example, if the boiling point is low, it is difficult to handle because it evaporates immediately. On the other hand, if it is high, it is difficult to remove with a vacuum pump or the like, and it may remain in the perfluoropolyether. Therefore, it is desirable that the solvent used has a boiling point of about 60 to 120 ° C.
[0022]
Solvents having a dipole moment of 1.0 Debye or higher and a boiling point in the range of 60 to 120 ° C include chloroform (61 ° C), tetrahydrofuran (65 to 66 ° C), ethyl acetate (77 ° C), pyridine (115 to 116 ° C) ), 2-butanone (80 ° C.) and the like.
[0023]
Solvents with dipole moments in the range of 0 to 0.6 Debye and boiling points in the range of 60 to 120 ° C include toluene (111 ° C), n-hexane (69 ° C), n-heptane (98 ° C), benzene (80 ° C.).
[0024]
On the other hand, if the heat of vaporization is too high, it is difficult to remove with a vacuum pump or the like and may remain in the perfluoropolyether. Therefore, the heat of vaporization of the solvent used is preferably about 35 kJ / mol or less. Solvents applicable to this include octane (35.0 kJ / mol), chloroform (29.4 kJ / mol), ethyl acetate (32.5 kJ / mol), tetrahydrofuran (35.0 kJ / mol), toluene (33.5 kJ / mol), etc. .
[0025]
By the way, examples of the organic solvent having a dipole moment of 1.0 Debye or more and having a hydroxyl group include methanol (2.9), ethanol (3.0), 1-propanol (3.1), 1-butanol (3.0) and the like. These solvents hardly dissolve perfluoropolyethers having piperonyl groups. That is, since these are poor solvents for AM2001, it is possible to use these solvents in place of an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and no hydroxyl group in performing the extraction operation. The refractive index of the obtained non-extracted product tends to increase. In these solvents, extraction using methanol and tetrahydrofuran as a good solvent for perfluoropolyether having a piperonyl group tends to have a lower refractive index than other solvent combinations. In addition, since it has a hydroxyl group, it is necessary to be careful because moisture taken in easily absorbs moisture and loses reproducibility of distribution equilibrium during extraction. In addition, these solvents have a relatively large heat of vaporization, so that they are difficult to remove with a vacuum pump or the like and may remain in the perfluoropolyether. For example, methanol is 35.3 kJ / mol, ethanol is 38.6 kJ / mol, 1-propanol is 41.0 kJ / mol, 1-butanol is 44.4 kJ / mol, and so on, and the heat of vaporization exceeds 35 kJ / mol.
[0026]
In addition to the extraction method described above, a method of obtaining a perfluoropolyether having a piperonyl group and having a refractive index of 1.324 or less includes a method of heating while reducing the pressure. Specifically, a perfluoropolyether having the same refractive index can be obtained by heating to 80 ° C. under a reduced pressure of 0.02 Pa. In this case, it is desirable to replace the container containing the perfluoropolyether having a piperonyl group with an inert gas such as nitrogen or argon before heating. This operation significantly suppresses the decomposition of the piperonyl group.
[0027]
(1-b) Application method
A method of applying the perfluoropolyether purified by the above method to a recording medium will be described. Since the thickness of the layer made of the surface modifier is about 0.5 to 5 nm, the film thickness may become too large if a bulk perfluoropolyether with a viscosity of about 0.01 Pa · s is applied at 30 ° C. is there. Therefore, at the time of coating, a solution dissolved in a solvent (a fluorine-containing solvent described later is appropriate) is used. However, the concentration varies depending on the application method and conditions.
[0028]
Examples of the coating method include a dip method and a spin coating method. In the dip method, the immersion time and the pulling speed, and in the spin coating method, the rotation speed and the rotation time are parameters for setting the concentration. If the concentration of the solution is the same, the dipping method tends to form a thicker lubricating layer as the immersion time is longer and the pulling speed is higher. However, depending on the solvent used, depending on the pulling speed, fine irregularities may be formed on the surface of the lubricating layer. In addition to the pulling speed, this affects not only the boiling point of the solvent used, the heat of evaporation, the environment during the coating operation (temperature, humidity, individual concentrations of contaminants such as oil mist and dust), and the like. In the spin coating method, the lubricant layer tends to be formed thicker as the rotation speed is lower and the rotation time is shorter. However, depending on the solvent used, fine irregularities may be formed on the surface of the lubricating layer depending on the rotation speed and rotation time. This is influenced by the boiling point, heat of evaporation, hygroscopicity, etc. of the solvent used in addition to the rotation speed and rotation time.
[0029]
The solvent to be used is selected from those that dissolve the perfluoropolyether purified by the above method. Specifically, fluorine-containing products such as FC-72, FC-84, FC-77, FC-75, PF-5080, PF-5052, HFE-7100, HFE-7200 manufactured by 3M, and Vertrel XF manufactured by Dupont A solvent is mentioned.
[0030]
(1-c) Applications
Examples of the use of the surface modifier include use as a surface modifier for improving the sliding characteristics of a magnetic recording medium in a magnetic recording apparatus. This is intended to reduce the coefficient of friction between the magnetic recording medium and the head, so that it can be used for other recording apparatuses that involve sliding between the recording medium and the head in addition to the magnetic recording medium. In addition, since it has a perfluoropolyether chain having water repellency and oil repellency, it can be used as a water repellant and oil repellant applied to a solid surface such as glass and metal.
[0031]
(2) Configuration of magnetic recording media
The magnetic recording medium of the present invention has at least one recording layer on a support, a protective layer thereon, and a film containing a perfluoropolyether having a piperonyl group thereon as an outermost layer. It is.
[0032]
Examples of the support include aluminum alloys, ceramics such as glass, polycarbonate, and the like. Especially in the case of glass, the content of sodium and potassium is higher than that of ordinary products for the purpose of increasing the hardness (those used for window glass and cups have a sodium content of about 5% and a potassium content of about 0 to 1%). Those having a large amount are suitable. However, considering the hardness and practicality, the sodium content is preferably about 10 to 20%, and the potassium content is preferably about 1 to 5%.
[0033]
Examples of the constituent material of the magnetic layer that is the recording layer of the magnetic recording medium include alloys centering on elements capable of forming a ferromagnetic material such as iron, cobalt, nickel, and oxides thereof. These are formed by plating or sputtering.
[0034]
Examples of the protective layer include carbon, SiC, and SiO2. These are mainly formed by sputtering.
[0035]
(3) Magnetic recording media / devices and their applications
In the magnetic recording apparatus of the present invention, the temperature in the hard disk drive is considerably increased by heat generated from the motor that rotates the magnetic recording medium. At this time, if a surface modifier that generates foreign matter on the surface due to the heat generation is applied to the magnetic recording medium, the impact caused by the collision between the foreign matter and the head increases, and this impact causes an error when reading information. There is a risk of causing it. Therefore, the surface modifier of the present invention is used in the magnetic recording apparatus of the present invention. The surface modifier of the present invention tends to have high thermal stability. For this reason, the recording medium coated with this material hardly generates foreign matter on the surface even in a high-temperature hard disk drive.
[0036]
The magnetic recording apparatus of the present invention can ensure a large recording capacity by stacking several magnetic recording media.
[0037]
Applications of the magnetic recording medium of the present invention include external memories such as electronic computers and word processors (specifically, hard disk devices and floppy disks). It is also applicable to various devices such as navigation systems, games, mobile phones, PHS, building crime prevention, internal / external memory of power plant management / control systems, etc.
[0038]
[Action]
Of the perfluoropolyethers having a piperonyl group of the present invention, those having a low refractive index tend to have low scattering properties and high thermal stability. In other words, the perfluoropolyether on the surface of the magnetic recording medium coated with this perfluoropolyether is hardly scattered or decomposed even in a hard disk drive at a high temperature. For this reason, it is difficult for the generation of foreign matters to the surface due to the decrease in the layer thickness accompanying the scattering of perfluoropolyether and the decomposition. Therefore, it is considered that a magnetic recording apparatus equipped with this magnetic recording medium does not cause a head crash or error during reading.
[0039]
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to these examples.
[0040]
[Example 1]
First, the solubility of AM2001 manufactured by Augmont, one of perfluoropolyethers having a piperonyl group at the terminal, in various solvents is examined. This is because a good solvent and a poor solvent are required for AM2001 during extraction. Table 1 shows the solvents for dissolving AM2001.
[0041]
[Table 1]

[0042]
All of the solvents in Table 1 had a dipole moment of 1.0 Debye or more and did not have a hydroxyl group or a carboxyl group. Next, solvents that do not dissolve AM2001 are shown in Tables 2 to 4, depending on the range of dipole moment and the presence or absence of hydroxyl groups or carboxyl groups. First, Table 2 shows solvents that do not dissolve AM2001 and do not have a hydroxyl group or a carboxyl group.
[0043]
[Table 2]

[0044]
[Table 3]

[0045]
[Table 4]

[0046]
All the solvents in Table 2 had a dipole moment of 0.6 Debye or less.
[0047]
Of the solvents that do not dissolve AM2001, those having a hydroxyl group or a carboxyl group are shown in Table 3. AM2001 was insoluble in the solvents shown in Tables 2 and 3, and the stirred mixture of AM2001 and the solvent used separated into two layers. In addition, there were some solvents that could be mixed with AM2001 without being separated into two layers, but mixed with each other. These are shown in Table 4. All the solvents in Table 4 had a dipole moment greater than 0.6 Debye and less than 1.0 Debye. Moreover, it did not have a hydroxyl group or a carboxyl group in the molecule. At the time of extraction, first, AM2001 is dissolved in a good solvent, and then a poor solvent is added to separate the extract into two layers of extract and non-extract. Therefore, it is necessary to use both good and poor solvents during AM2001 extraction. From Table 1 to Table 4, a good solvent has a dipole moment of 1.0 Debye or more and does not have a hydroxyl group or a carboxyl group, and the poor solvent has a hydroxyl group or a carboxyl group, a hydroxyl group, or a carboxyl group. When there is no group, it was found that the dipole moment should be 0.6 Debye or less.
[0048]
Next, the purification method will be described. First, an extraction operation is performed.
[0049]
AM2001 shown in the following formula (1 part by weight)
[0050]
[Chemical 1]

[0051]
Add various weights of the good solvents shown in Table 5 to Table 10 and stir vigorously.
[0052]
[Table 5]

[0053]
[Table 6]

[0054]
[Table 7]

[0055]
[Table 8]

[0056]
[Table 9]

[0057]
[Table 10]

[0058]
Various weights of the types of poor solvents shown in Table 5 to Table 10 were added to this, and after vigorous stirring, the mixture was allowed to stand for several minutes and then separated into two layers. After standing for 12 hours, the lower layer is collected and heated at 50 ° C. under reduced pressure with a vacuum pump to volatilize the contained solvent. The non-extracted product thus obtained is designated as compounds 1 to 66. The refractive indexes of compounds 1 to 66 are also shown in Tables 5 to 10.
[0059]
Table 5 shows that for AM2001, ethyl acetate (dipole moment is 1.9 Debye) as a good solvent and n-hexane (dipole moment is 0 Debye) as a poor solvent when extracted using various weights. It is a thing. Table 6 also shows that chloroform (dipole moment is 1.0 Debye) as a good solvent for AM2001, or tetrahydrofuran (dipole moment is 1.6 Debye), 2-butanone (dipole moment is 3.3 Debye), and n-hexane as a poor solvent. (Dipole moment is 0 Debye), or n-heptane (dipole moment is 0 Debye), n-octane (dipole moment is 0 Debye), toluene (dipole moment is 0.37 Debye), o-xylene (dipole) Moment is 0.52 Debye) and 1,2,3-trimethylbenzene (dipole moment is 0.56 Debye). Furthermore, Table 7 to Table 10 show that chloroform (dipole moment is 1.0 Debye), tetrahydrofuran (dipole moment is 1.6 Debye), ethyl acetate (dipole moment is 1.9 Debye), 2-butanone as a good solvent for AM2001. Dipole moment is 3.3 Debye), 1-pentanol (dipole moment is 0.89 Debye) as poor solvent, or 2-octanol (dipole moment is 1.6 Debye), acetic acid (dipole moment is 2.0 Debye), methanol (dipole) Extraction using 2.9 Debye), ethanol (dipole moment is 3.0 Debye), 1,5-pentanediol (dipole moment is 3.8 Debye), pentaethylene glycol (dipole moment is 6.1 Debye) using various weights It is a non-extracted product.
[0060]
Next, purification operation is performed by heating at reduced pressure. AM2001 (1 part by weight) and a stirring bar are placed in an eggplant type flask and connected to a vacuum pump via a trap. The trap is cooled with liquid nitrogen. The eggplant-shaped flask is immersed in an oil bath, and then stirring of AM2001 in the eggplant-shaped flask is started with a stirring bar. Stirring is continued until the inside is returned to normal pressure. After the inside is replaced with nitrogen gas, suction is started with a vacuum pump. The eggplant-shaped flask is evacuated to about 0.02 Pa. Next, the eggplant-shaped flask is heated to 80 ° C. in an oil bath. Then, a part of AM2001 in the eggplant-shaped flask starts to volatilize, and liquid begins to accumulate in the trap. After volatilization has stopped, heating is stopped and the eggplant-shaped flask is cooled to room temperature. After returning the eggplant type flask to normal pressure, stirring is stopped and the liquid remaining in the eggplant type flask is collected. This liquid is referred to as compound 67. The refractive index of Compound 67 was measured and found to be 1.324.
[0061]
Next, a perfluoropolyether having a piperonyl group at the terminal is synthesized. Piperonyl alcohol (15 parts by weight) is dissolved in pyridine (50 parts by weight), p-toluenesulfonyl chloride (20 parts by weight) is added thereto, and the mixture is stirred at 50 ° C. for 8 hours. After cooling, the reaction solution is poured into 10% by weight hydrochloric acid (300 parts by weight). Check the liquidity and add 10% by weight hydrochloric acid in small increments until it is acidic. This is put into a separatory funnel, dichloromethane (300 parts by weight) is added, and stirred vigorously. The lower dichloromethane layer is separated and washed with saturated saline until the liquid becomes neutral. After drying over anhydrous sodium sulfate, the dichloromethane is volatilized with an evaporator. This is purified by silica gel column chromatography (developing solvent is n-hexane: ethyl acetate = 2: 1) to obtain 20 parts by weight of a compound obtained by tosylating the hydroxyl group of piperonyl alcohol (hereinafter referred to as compound 68 ').
[0062]
Next, a 5% by weight sodium hydroxide methanol solution (16 parts by weight) was added to DOL-2000 (20 parts by weight) manufactured by Augmont, which is one of the perfluoropolyethers having a hydroxyl group at the end. After stirring for 10 minutes, methanol is volatilized with an evaporator. To this was added compound 68 '(6 parts by weight) dissolved in dichloromethane (30 parts by weight), and the mixture was further stirred at 110 ° C for 8 hours. After cooling, water (15 parts by weight), dichloromethane (15 parts by weight) and 3M PF-5052 (100 parts by weight) are added to the reaction mixture and vigorously stirred. After standing for 12 hours, the lower PF-5052 layer is collected, and the PF-5052 in it is volatilized with an evaporator. In this way, a perfluoropolyether (20 parts by weight) having a piperonyl group at a part of the terminal is obtained. This compound is hereinafter referred to as compound 68 (following formula).
[0063]
[Chemical 2]

[0064]
The compound 68 had a refractive index of 1.329. When the solubility of Compound 68 in various solvents shown in Tables 1 to 4 was examined, the results were the same as AM2001.
[0065]
The compound 68 is then purified as in AM2001. Specifically, various weights of the kinds of good solvents shown in Tables 11 to 16 are added to Compound 68 (1 part by weight) and vigorously stirred. Various weights of the poor solvents shown in Table 11 to Table 16 were added to this, and after vigorous stirring, the mixture was allowed to stand for several minutes and then separated into two layers. After standing for 12 hours, the lower layer is collected and heated at 50 ° C. under reduced pressure with a vacuum pump to volatilize the contained solvent. The non-extracted product thus obtained is referred to as compounds 69 to 134. Further, the refractive indexes of the compounds 69 to 134 are also shown in Tables 11 to 16.
[0066]
[Table 11]

[0067]
[Table 12]

[0068]
[Table 13]

[0069]
[Table 14]

[0070]
[Table 15]

[0071]
[Table 16]

[0072]
Among these, Table 11 shows the non-existence of compound 68 extracted with various weights of ethyl acetate (dipole moment 1.9 Debye) as a good solvent and n-hexane (dipole moment 0 Debye) as a poor solvent. It is an extract. Table 12 also shows that chloroform (dipole moment is 1.0 Debye), tetrahydrofuran (dipole moment is 1.6 Debye), 2-butanone (dipole moment is 3.3 Debye), n- Hexane (dipole moment is 0 Debye), n-heptane (dipole moment is 0 Debye), n-octane (dipole moment is 0 Debye), toluene (dipole moment is 0.37 Debye), o-xylene (dipole) The child moment is 0.52 Debye) and 1,2,3-trimethylbenzene (dipole moment is 0.56 Debye). Furthermore, Tables 13 to 16 show that chloroform (dipole moment is 1.0 Debye), tetrahydrofuran (dipole moment is 1.6 Debye), ethyl acetate (dipole moment is 1.9 Debye), 2-butanone as a good solvent for compound 68 (Dipole moment is 3.3 Debye), 1-pentanol (dipole moment is 0.89 Debye) as poor solvent, or 2-octanol (dipole moment is 1.6 Debye), acetic acid (dipole moment is 2.0 Debye), methanol ( Dipole moment is 2.9 Debye), ethanol (dipole moment is 3.0 Debye), 1,5-pentanediol (dipole moment is 3.8 Debye), pentaethylene glycol (dipole moment is 6.1 Debye) It is a non-extracted product when extracted.
[0073]
Next, purification operation is performed by heating at reduced pressure. Compound 68 (1 part by weight) and a stirring bar are placed in an eggplant type flask and connected to a vacuum pump through a trap. The trap is cooled with liquid nitrogen. The eggplant-shaped flask is immersed in an oil bath, and stirring of the compound 68 in the eggplant-shaped flask is started with a stirring bar. Stirring is continued until the inside is returned to normal pressure. After the inside is replaced with nitrogen gas, suction is started with a vacuum pump. The eggplant-shaped flask is evacuated to about 0.02 Pa. Next, the eggplant-shaped flask is heated to 80 ° C. in an oil bath. Then, a part of the compound 68 in the eggplant type flask starts to volatilize, and liquid starts to accumulate in the trap. After volatilization has stopped, heating is stopped and the eggplant-shaped flask is cooled to room temperature. After returning the eggplant type flask to normal pressure, stirring is stopped and the liquid remaining in the eggplant type flask is collected. This liquid is referred to as Compound 135. The refractive index of compound 135 was measured and found to be 1.324.
[0074]
A solution is prepared by diluting the compounds 1-135 obtained by the above operation and AM2001 with PF-5080 manufactured by 3M so that the concentration becomes 1000 ppm. Using this, a magnetic recording medium is produced. FIG. 1 shows the configuration and the manufacturing method is described below.
[0075]
A Ni-P layer 2 (layer thickness: about 15 μm) is formed on the surface of an Al alloy disk 1 having a diameter of 3.5 inches by plating. Next, a Cr layer 3 (layer thickness: about 250 nm), a Ni-Co magnetic layer 4 (layer thickness: about 50 nm), and a carbon layer 5 (layer thickness: about 50 nm) are sequentially deposited on this layer by sputtering. Formed. The disk was immersed in the PF-5080 solution for 1 minute and pulled up at a speed of 1 mm / s. Thereafter, it was allowed to stand at room temperature for 2 hours to volatilize PF-5080, and a magnetic recording medium having AM 2001 and a layer 6 composed of compounds 1-135 prepared by the above extraction operation formed on the surface was prepared. Hereinafter, AM2001 or the layer 6 composed of the compounds 1 to 135 will be referred to as a lubricating layer. This lubricating layer has an average thickness of 15 mm.
[0076]
The sliding characteristics of this magnetic recording medium were evaluated by the CSS test method (contact stop method: tester manufactured by Onoda Cement Co., Ltd.). The conditions are: Rotation speed: 3600 rpm, 1 cycle: 30 seconds, Cycle number: 1000 cycles, Head load: 10 g. The maximum static frictional force when restarting after leaving the last cycle for 6 hours Asked. In addition, the number of rotations at the time of restart is 1 rpm. As a result, the frictional force on the surface of the magnetic recording medium using compounds 1-135 was in the range of 8-10 g. The friction force of the magnetic recording medium coated with AM2001 without performing the above extraction operation was 9 to 10 g. AM2001 is widely used as a lubricant for magnetic recording media, and compounds 1-135, which are surface modifiers of the present invention, exhibited almost the same sliding characteristics as AM2001. Therefore, it was confirmed that the compounds 1 to 135 have characteristics as a lubricant for magnetic recording media, which is one of the characteristics of the surface modifier of the present invention.
[0077]
Next, the magnetic recording medium is set in the hard disk drive shown in FIG. Further, the above magnetic recording medium was rotated at 5400 rpm or 7200 rpm for 200 hours by the magnetic recording apparatus shown in FIG.
[0078]
Then, in the magnetic recording device equipped with the magnetic recording medium coated with compounds 1 to 135 and having a refractive index of 1.324 or less, the head did not crash at either rotation speed, but the refractive index exceeded 1.324. With a magnetic recording device equipped with a coated material, the head crashed within one minute after starting reading at either rotation speed, making reading impossible. Of the compounds used, those having a refractive index of 1.324 or less are compounds 1-36, 47-52, 67, 69-104, 115-120, 135, and those having a refractive index exceeding 1.324 are AM2001, compounds 37- 46, compounds 53-66, 68, 105-114, 121-134. Those that did not crash the head had a friction force of 2 g or less during rotation, and those that crashed had a friction force of 5 g or more during rotation. It became. The thickness of the lubricating layer after rotating for 200 hours of these magnetic recording media was examined from the absorbance of IR 1300 Kaiser, and the average thickness of the lubricating layer was determined for each compound having the same refractive index.
[0079]
The thickness of each lubricating layer made of each compound was within ± 1 mm with respect to the average thickness for each refractive index. The lubricating layer made of a compound having a refractive index of 1.324 or less secured 11% or more, which is 70% or more of the initial film thickness of 15 mm even after rotation for 200 hours. However, the lubricating layer made of a compound having a refractive index greater than 1.324 was less than 60% of the initial film thickness after rotation for 200 hours, and was less than 60%. The thinning of the lubricating layer is a phenomenon that occurs because the compound constituting the lubricating layer is scattered by the rotation of the medium.
[0080]
When the average film thickness is 6 mm or less, it is considered that a portion where no compound exists at all appears on the surface. In other words, it is considered that a partial defect occurs in the lubricating layer, so that the lubricity is greatly lowered and a crash occurs.
[0081]
  From the above results, in the surface modifier containing a perfluoropolyether having a piperonyl group, the refractive index of the surface modifier is 1.32.2The effect that the surface modifier characterized by the following is extremely low scattering property was recognized.
[0082]
  A magnetic recording medium comprising a film containing perfluoropolyether having a piperonyl group as an outermost layer, wherein the refractive index of the perfluoropolyether is 1.322The magnetic recording medium characterized by the following was found to have an effect that the surface had sufficient lubricity even after a long continuous rotation of 200 hours.
[0083]
  Further, a perfluoropolyether having a piperonyl group in a magnetic recording medium having a magnetic recording medium for recording information and a head for writing / erasing information to / from the magnetic recording medium and reading information from the magnetic recording medium Is a layer containing the outermost layer of the magnetic recording medium, and the refractive index of the perfluoropolyether is 1.32.2In the magnetic recording apparatus characterized by the following, it was confirmed that the head did not crash during the reading of information even after the medium was continuously rotated for a long time of 200 hours.
[0084]
The configuration of the used hard disk is as follows. A magnetic recording medium 7 is fixed to a rotating shaft portion of a spindle motor 8 that is a rotation control mechanism, and each magnetic recording medium 7 has a head 9 in which elements for recording / reproducing are incorporated on the upper surface and the lower surface, respectively. Is provided. The head 9 is connected to an actuator 11 that is a positioning mechanism of the head 9 via a head suspension 10. The magnetic recording medium 7, the head 9, the head suspension 10, and the actuator 11 are sealed by a mechanical seal 12 so that dust and the like do not enter from the outside. Information signals are exchanged (transferred) between the magnetic recording medium and the controller (controller) of the magnetic recording apparatus via a head and a cable (for data signal transfer) 13. The actuator is controlled via a cable (for actuator control) 14 and the spindle motor is controlled via a cable (for spindle motor control) 15.
[0085]
The configuration of the magnetic recording apparatus used is as follows. The hard disk drive 16 is controlled by a controller 18 via a cable 17 (for data signal transfer, actuator control, and spindle motor control in a lump). The controller obtains electricity for operating each part from the power supply unit 19 via the power cable 20. The controller is controlled by the control panel 21. The cable 22 is connected during this time. The operating state of the apparatus can be monitored by the display 23. A cable 24 is connected between the controller and the display.
[0086]
[Example 2]
Non-extraction when extraction is performed using an organic solvent having a dipole moment of 1.0 Debye or higher as a good solvent for AM2001 and having no carboxyl group and hydroxyl group, and an organic solvent having a carboxyl group or hydroxyl group as a poor solvent The products are shown in Tables 7-10.
[0087]
Among these, Table 7 shows non-extracted substances (compounds 37 to 43) obtained by extracting chloroform (dipole moment is 1.0 Debye) as a good solvent using various weights. Table 8 shows non-extracted materials (compounds 44 to 54) obtained by extracting tetrahydrofuran (dipole moment is 1.6 Debye) as a good solvent using various weights. Table 9 shows non-extracted compounds (compounds 55 to 60) obtained by extracting ethyl acetate (dipole moment is 1.9 Debye) as a good solvent using various weights. Table 10 shows non-extracts (compounds 61 to 66) obtained by extracting 2-butanone (dipole moment is 3.3 Debye) as a good solvent using various weights. Also, the poor solvent of AM2001 when extracting these compounds is 1-pentanol (dipole moment is 0.89 Debye), 2-octanol (dipole moment is 1.6 Debye), acetic acid (dipole moment is 2.0 Debye) , Methanol (dipole moment is 2.9 Debye), ethanol (dipole moment is 3.0 Debye), 1,5-pentanediol (dipole moment is 3.8 Debye), pentaethylene glycol (dipole moment is 6.1 Debye) .
[0088]
Next, when extraction was performed using an organic solvent having a dipole moment of 1.0 Debye or higher as a good solvent for compound 67 and having no carboxyl group and hydroxyl group, and an organic solvent having a carboxyl group or hydroxyl group as a poor solvent Table 13 to Table 16 show the non-extracts.
[0089]
Of these, Table 13 shows non-extracted substances (compounds 105 to 111) extracted with various weights of chloroform (dipole moment is 1.0 Debye) as a good solvent. Table 14 shows non-extracted substances (compounds 112 to 122) extracted with various weights of tetrahydrofuran (dipole moment is 1.6 Debye) as a good solvent. Table 15 shows non-extracted substances (compounds 123 to 128) extracted with various weights of ethyl acetate (dipole moment is 1.9 Debye) as a good solvent. Table 16 shows non-extracted substances (compounds 129 to 134) obtained by extracting 2-butanone (dipole moment is 3.3 Debye) as a good solvent using various weights. Also, the poor solvent of AM2001 when extracting these compounds is 1-pentanol (dipole moment is 0.89 Debye), 2-octanol (dipole moment is 1.6 Debye), acetic acid (dipole moment is 2.0 Debye) , Methanol (dipole moment is 2.9 Debye), ethanol (dipole moment is 3.0 Debye), 1,5-pentanediol (dipole moment is 3.8 Debye), pentaethylene glycol (dipole moment is 6.1 Debye) . The refractive index of each compound is also shown.
[0090]
First, as a result of the refractive index measurement, the refractive index of the non-extracted compound (compounds 47 to 52) when combining tetrahydrofuran as the good solvent and methanol as the poor solvent among the compounds 37 to 66 shown in Tables 7 to 10 is 1.324. there were. In other combinations, the refractive index was 1.325 or more.
[0091]
Next, the surface of the magnetic recording medium coated with compounds 37 to 67 and 105 to 135, AM2001 (refractive index of 1.328), and compound 68 (refractive index of 1.329) prepared by the same method as in Example 1 was multiplied by 1000 times. When observed with an optical microscope, these surfaces were flat and no foreign matter was observed. These magnetic recording media were left for 10 hours in a thermostatic chamber whose inside was adjusted to 70 ° C., and the surface was observed. The results are shown in Table 17. On the surface of the magnetic recording medium coated with compounds 37 to 46, 53 to 66, 68, 105 to 114, 121 to 134, AM2001, spots with a size of about 1 to 100 square microns are approximately per square millimeter. About 1-10 were seen. When this speckle was analyzed by microscopic IR, absorption estimated to originate from the carbonyl group of benzoquinone was observed in the vicinity of 1630 Kaiser. However, the surface of the magnetic recording medium coated with compounds 47 to 52, 67, 115 to 120, and 135 was flat even after being left in a constant temperature bath at 70 ° C., and no foreign matter was observed.
[0092]
Next, the magnetic recording medium heated in the thermostatic chamber was set in the same magnetic recording apparatus as in Example 1, and information was read out. No foreign matter was observed after being left in the thermostatic chamber at 70 ° C. The magnetic recording media coated with the compounds 47-52 and 67, 115-120, 135 had no error, but the remaining compounds 37-46, 53-66, 68, 105-114, 121 In the magnetic recording media coated with ~ 134 and AM2001, errors occurred during reading. When the surface of the location where the error occurred was examined, all were spots where spots were generated by heating in a thermostatic chamber.
[0093]
Next, the presence or absence of a change in surface smoothness due to heating when the base material was changed from carbon produced by sputtering to silicon oxide was examined. A PF-5080 solution of compounds 37 to 67 and 105 to 135, AM2001 and compound 68 prepared in Example 1 is applied to a 3.5-inch diameter silicon wafer mirror-polished in the same manner as in the production of the magnetic recording medium. The coated surface was observed with an optical microscope in the same manner as when observing the surface of the magnetic recording medium, and then the surface was again observed after being left for 10 hours in a thermostatic chamber adjusted to 70 ° C. inside. The results are shown in Table 18. Similar to the observation of the surface of the magnetic recording medium, the surface of the silicon wafer coated with compounds 47 to 52, 67, 115 to 120, and 135 was flat even after being left in a constant temperature bath at 70 ° C., and no foreign matter was observed. However, the remaining compound, compounds 37 to 46, and 53 to 66, 68, 105 to 114, 121 to 134, and AM2001 coated silicon wafer surface have 1 spot with a size of about 1 to 100 square microns. About 1-10 pieces were found per square millimeter. All of these compounds have a refractive index exceeding 1.324. When this speckle was analyzed by microscopic IR, absorption estimated to originate from the carbonyl group of benzoquinone was observed in the vicinity of 1630 Kaiser. Moreover, before leaving to stand in a thermostat, the contact angle with the water of the silicon wafer surface which apply | coated compound 37-66, 105-134, AM2001, and compound 68 with water was 105-110 degrees. In the case of compounds 67 and 134, the angle was 100 °. Among these, the contact angle of the silicon wafer coated with compounds 47 to 52 and 67, 115 to 120, 135 did not change even after being left at 80 ° C. for 10 hours. However, the contact angles of silicon wafers coated with compounds 37-46, 53-66, 105-114, 121-134, AM2001, and compound 68, which remain, are 88-95 ° after standing for 10 hours in 70 ° C. Declined. The contact angle of a 3.5-inch diameter silicon wafer mirror-polished before applying compounds 37 to 66 and 105 to 134, AM2001 and compound 68 was about 60 °.
[0094]
  From the above results, refractive index 1.322The following surface modifiers containing perfluoropolyethers having piperonyl groups have the same structure and a refractive index of 1.32.2The effect of having heat resistance compared to the larger one was confirmed.
[0095]
In addition, even when the same refractive index is 1.324, the compounds 47 to 52 and 115 to 120 obtained by the extraction method have a higher surface water repellency than the compounds 67 and 135 obtained by the heating method under reduced pressure. high.
[0096]
From this result, among the surface modifiers containing a perfluoropolyether having a piperonyl group having a refractive index of 1.324 or less, the surface modifier is tetrahydrofuran and methanol, respectively, 0.5 to 20 times the perfluoropolyether having a piperonyl group. It was confirmed that a material having a non-extracted portion when extracted using the weight of can form a surface having high water repellency.
[0097]
[Example 3]
An organic solvent that has a dipole moment of 1.0 Debye or higher as a good solvent with respect to AM2001 and does not have a carboxyl group and a hydroxyl group; Tables 5 and 6 show non-extracted materials when extracted using an organic solvent that does not contain. Of these, Table 5 shows non-extracted materials extracted with various weights of ethyl acetate (dipole moment is 1.9 Debye) as a good solvent and n-hexane (dipole moment is 0 Debye) as a poor solvent. (Compounds 1 to 10). Also shown in Table 6 are chloroform (dipole moment is 1.0 Debye) or tetrahydrofuran (dipole moment is 1.6 Debye), 2-butanone (dipole moment is 3.3 Debye), poor solvent for AM2001 as a good solvent. N-hexane (dipole moment is 0 Debye), n-heptane (dipole moment is 0 Debye), n-octane (dipole moment is 0 Debye), toluene (dipole moment is 0.37 Debye), o- This is a non-extracted product (compounds 11 to 36) when xylene (dipole moment is 0.52 Debye) and 1,2,3-trimethylbenzene (dipole moment is 0.56 Debye) are extracted using various weights.
[0098]
In addition, a dipole moment which is a good solvent for compound 68 is 1.0 Debye or more, an organic solvent having no carboxyl group and a hydroxyl group, and a dipole moment as a poor solvent is in the range of 0 to 0.6 Debye and a carboxyl group Tables 11 and 12 show non-extracted materials extracted with an organic solvent having no hydroxyl group. Of these, Table 11 shows non-extracted substances (compounds 69 to 69) extracted with various weights of ethyl acetate (dipole moment is 1.9 Debye) as a good solvent and n-hexane (dipole moment is 0 Debye) as a poor solvent. 78). Table 12 also shows chloroform as a good solvent for AM2001 (dipole moment is 1.0 Debye), tetrahydrofuran (dipole moment is 1.6 Debye), 2-butanone (dipole moment is 3.3 Debye), and n-hexane as a poor solvent. (Dipole moment is 0 Debye), or n-heptane (dipole moment is 0 Debye), n-octane (dipole moment is 0 Debye), toluene (dipole moment is 0.37 Debye), o-xylene (dipole) Moment is 0.52 Debye) and 1,2,3-trimethylbenzene (dipole moment is 0.56 Debye), which is a non-extracted product (compounds 79 to 104) extracted with various weights. Compounds 1-36 and 69-104 all have a refractive index of 1.324 or less.
[0099]
When the surface of the magnetic recording medium coated with compounds 1-36 and 69-104, AM2001, compound 68 prepared in Example 1 was observed with an optical microscope with a magnification of 1000 times, this surface was flat and no foreign matter was observed. It was. The surfaces of these magnetic recording media were observed after being left in a thermostatic chamber whose inside was adjusted to 80 ° C. for 10 hours. For comparison, the magnetic recording media coated with compounds 37 to 67 and 105 to 135 used in Example 2 were also left for 10 hours in a thermostatic chamber adjusted to 80 ° C. in the same manner as the magnetic recording media coated with the above compounds. The surface was observed. The results are shown in Table 17.
[0100]
On the surface of the magnetic recording medium coated with AM2001 and compounds 37 to 68 and 105 to 135, about 1 to 10 spots having a size of about 1 to 100 square microns were observed per square millimeter. When this speckle was analyzed by microscopic IR, absorption estimated to originate from the carbonyl group of benzoquinone was observed in the vicinity of 1630 Kaiser. However, the surface of the magnetic recording medium coated with compounds 1 to 36 and 69 to 104 was flat even after being left in a thermostatic bath at 80 ° C., and no foreign matter was observed.
[0101]
Next, when the magnetic recording medium heated in the thermostatic chamber was set in the same magnetic recording apparatus as in Example 1 and information was read out, no foreign matter was observed after being left in the thermostatic chamber at 80 ° C. The magnetic recording media coated with the compounds 1 to 36 and 69 to 104 had no error, but the remaining compound AM2001 and the magnetic recording media coated with the compounds 37 to 68 and 105 to 135 were all read out. An error occurred during When the surface of the location where the error occurred was examined, all were spots where spots were generated by heating in a thermostatic chamber.
[0102]
Next, the presence or absence of a change in surface smoothness due to heating when the base material was changed from carbon produced by sputtering to silicon oxide was examined. AM2001 prepared in Example 1 and a PF-5080 solution of compounds 1-36 and 68-104 are applied to a 3.5-inch diameter silicon wafer mirror-polished in the same manner as in the production of the magnetic recording medium. The coated surface was observed with an optical microscope in the same manner as when observing the surface of the magnetic recording medium, and then the surface was again observed after being left in a thermostatic chamber whose temperature was adjusted to 80 ° C. for 10 hours. As in the case of the magnetic recording medium, the silicon wafer coated with the compounds 37 to 67 and 105 to 135 used in Example 2 for comparison was also controlled at 80 ° C. in the same manner as the silicon wafer coated with the above compound. After standing in the bath for 10 hours, the surface was observed. The results are shown in Table 18.
[0103]
The surface of the silicon wafer coated with compounds 1-36 and 69-104 was flat after standing in a thermostatic bath at 80 ° C., and no foreign matter was observed. However, on the surface of the silicon wafer coated with AM2001, which is the remaining compound, and compounds 37 to 68 and 105 to 135, about 1 to 10 spots per square millimeter are observed with an area of about 1 to 100 square microns. It was. When this speckle was analyzed by microscopic IR, absorption estimated to originate from the carbonyl group of benzoquinone was observed in the vicinity of 1630 Kaiser. Moreover, before leaving to stand in a thermostat, the contact angle with the water of the silicon wafer surface which apply | coated the used compound was 100-110 degrees. Among these, the contact angle of the silicon wafer coated with compounds 1-36 and 69-104 did not change after being left at 80 ° C. for 10 hours. However, the contact angle of the remaining compound AM2001 and the silicon wafer coated with compounds 37 to 68 and 105 to 135 decreased to 88 to 95 ° after standing at 80 ° C. for 10 hours.
[0104]
In Example 2, a magnetic recording medium coated with compounds 47 to 52 and 115 to 120, which are non-extracted components when tetrahydrofuran and methanol are respectively extracted using 0.5 to 20 times the weight of the surface modifier, And it was confirmed that the silicon wafer had a heat-resistant temperature of 70 ° C. However, it was found that the magnetic recording medium coated with these compounds and the silicon wafer in this example were not heat resistant at 80 ° C. On the other hand, an organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and a hydroxyl group, and an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and a hydroxyl group, respectively Magnetic recording media coated with compounds 1-36 and 69-104, which are non-extracted components when extracted using 0.5 to 20 times the weight of the modifier, and silicon wafers have higher heat resistance Was confirmed.
[0105]
  From the above, refractive index 1.322In the following surface modifier containing a perfluoropolyether having a piperonyl group, the surface modifier has a dipole moment of 1.0 Debye or more, an organic solvent having no carboxyl group and no hydroxyl group, and a dipole moment It consists of a non-extracted portion when an organic solvent that is in the range of 0 to 0.6 Debye and does not have a carboxyl group and a hydroxyl group is extracted using 0.5 to 20 times the weight of perfluoropolyether having a piperonyl group. It was confirmed that the coating surface was a highly heat-stable surface modifier having the effects of maintaining flatness and water repellency even when left at 80 ° C.
[0106]
Further, a film comprising at least one recording layer on a support, and a perfluoropolyether having a piperonyl group having a refractive index of 1.324 or less on the surface of the recording layer or a protective layer provided outside the recording layer In the magnetic recording medium, wherein the perfluoropolyether has a dipole moment of 1.0 Debye or more, an organic solvent having no carboxyl group and no hydroxyl group, and a dipole moment of 0 to 0.6 Debye. What is characterized by consisting of a non-extracted portion when an organic solvent having no carboxyl group and no hydroxyl group is extracted using 0.5 to 20 times the weight of perfluoropolyether having a piperonyl group, A magnetic recording medium with high thermal stability that has the effect of not causing errors in reading even when left at 80 ° C. Was recognized.
[0107]
[Example 4]
A magnetic recording medium coated with compounds 1-135 and AM2001 was prepared in the same manner as in Example 1, and the surface was left in a thermostatic bath for 10 hours in the same manner as in Example 1 except that the temperature of the thermostatic bath was set to 90 ° C. Was observed. The results are shown in Table 17.
[0108]
[Table 17]

[0109]
The surface of the magnetic recording medium coated with compounds 4 to 6 and 72 to 74 was flat even after being left in a thermostatic bath, and no foreign matter was observed. However, the magnetic recording medium using AM2001, compounds 1-3, 7-71, 75-135, which is the remaining compound, has about 1-10 spots per square millimeter with an area of about 1-100 square microns. The degree was seen. When this speckle was analyzed by microscopic IR, absorption estimated to originate from the carbonyl group of benzoquinone was observed in the vicinity of 1630 Kaiser.
[0110]
Next, when the magnetic recording medium heated by the above-mentioned thermostat was set in the same magnetic recording apparatus as in Example 1 and information was read out, the magnetic recording coated with compounds 4 to 6 and 72 to 74 was performed. The medium did not show any errors. However, the magnetic recording media coated with AM2001, compounds 1-3, 7-71, 75-135 all produced errors during reading. When the surface of the location where the error occurred was examined, all were spots where spots were generated by heating in a thermostatic chamber.
[0111]
Next, the presence or absence of a change in surface smoothness due to heating when the base material was changed from carbon produced by sputtering to silicon oxide was examined. A silicon wafer coated with compounds 1-135 and AM2001 was prepared in the same manner as in Example 1, and the surface was left in the thermostatic bath for 10 hours in the same manner as in Example 1 except that the temperature of the thermostatic bath was 90 ° C. Observed. The results are shown in Table 18.
[0112]
[Table 18]

[0113]
The surface of the silicon wafer coated with compounds 4 to 6 and 72 to 74 was flat even after being left in a thermostatic bath at 90 ° C., and no foreign matter was observed. However, the surface of the silicon wafer coated with AM2001, compounds 1-3, 7-71, 75-135, which is the remaining compound, has spots of about 1 to 100 square microns on the surface, approximately 1 to 10 per square millimeter. About one was seen. When this speckle was analyzed by microscopic IR, absorption estimated to originate from the carbonyl group of benzoquinone was observed in the vicinity of 1630 Kaiser. Moreover, before leaving to stand in a thermostat, the contact angle with the water of the silicon wafer surface which apply | coated the used compound was 100-110 degrees. Of these, the contact angle of the silicon wafer coated with compounds 4 to 6 and 72 to 74 did not change even after being left at 90 ° C. for 10 hours. However, the contact angle of the silicon wafer coated with AM2001, compounds 1-3, 7-71, and 75-135, which remained, decreased to 88-95 ° after standing at 90 ° C for 10 hours.
[0114]
In Example 3, the surface modifier has a dipole moment of 1.0 Debye or more, an organic solvent having no carboxyl group and a hydroxyl group, a dipole moment in the range of 0 to 0.6 Debye, and a carboxyl group and a hydroxyl group. Recording medium coated with compounds 1-36 and 69-104, characterized by comprising non-extracted components when an organic solvent having no solvent is extracted using 0.5 to 20 times the weight of the surface modifier It has been confirmed that the silicon wafer has a heat resistant temperature of 80 ° C. Further, in the present example, during extraction of compounds 1-36 and 69-104, 1 part by weight of ethyl acetate and 2.5-6 parts by weight of n-hexane are used with respect to 1 part by weight of the surface modifier. It was confirmed that the compounds (compounds 4 to 6 and 72 to 74) characterized by being composed of non-extracted components at the time of extraction have a heat resistance of 90 ° C.
[0115]
  From the above, refractive index 1.322In the following surface modifier containing a perfluoropolyether having a piperonyl group, the surface modifier contains 1 part by weight of ethyl acetate and n-hexane with respect to 1 part by weight of the perfluoropolyether having a piperonyl group. What is composed of a non-extracted portion when extracted with 2.5 to 6 parts by weight is a heat having an effect of keeping the coated surface flat and maintaining water repellency even when left at 90 ° C. It was found to be a highly stable surface modifier.
[0116]
  Further, it comprises at least one recording layer on the support and has a refractive index of 1.32 on the surface of the recording layer or a protective layer provided outside the recording layer.2A magnetic recording medium comprising a film containing a perfluoropolyether having the following piperonyl group as an outermost layer, wherein the perfluoropolyether is acetic acid per 1 part by weight of the perfluoropolyether having a piperonyl group. What is composed of the non-extracted portion when extracted with 1 part by weight of ethyl and 2.5 to 6 parts by weight of n-hexane is that the coated surface does not cause an error during reading even if left at 90 ° C. It was confirmed that the magnetic recording medium had the effect of high thermal stability because it did not produce spots causing the occurrence.
[0117]
[Example 5]
A magnetic recording medium coated with compounds 1-135 and AM2001 was prepared in the same manner as in Example 1, set in the hard disk drive shown in FIG. 2, and magnetic recording was performed at various rotational speeds by the magnetic recording apparatus having the configuration shown in FIG. Information was read after rotating the medium for 10 hours. The average distance between the head and the magnetic recording medium was set to 50 nm. The results are shown in Table 19.
[0118]
[Table 19]

[0119]
At 5400 rpm, which is the rotational speed of the conventional magnetic recording apparatus, no error occurred in the magnetic recording medium using any compound. The magnetic recording medium coated with compounds 1-36, 47-52, 67, 69-104, 115-120, 135 did not show any error at 7200 rpm, but AM2001, compounds 37-46, 53 In the magnetic recording media coated with ~ 66, 68, 105 ~ 114, 121 ~ 134, an error occurred in the signal. No error occurred on magnetic recording media coated with compounds 1-36 and 69-104 at a rotational speed of 8400 rpm, but all magnetic recording media coated with AM2001, compounds 37-68, 105-135 read. An error occurred during Furthermore, at 9600 rpm, the magnetic recording media coated with compounds 4-6 and 72-74 showed no error, but magnetic recording coated with AM2001, compounds 1-3, 7-71, 75-135. An error occurred during reading of all the media.
[0120]
When the magnetic recording medium was removed from the apparatus and the surface thereof was observed, the same spots as those generated by heating in the thermostatic chambers of Examples 1 to 4 occurred. In addition, the spots where these spots occurred corresponded to the locations where errors occurred.
[0121]
The refractive index of the surface modifier using these is as follows. It was recognized that an apparatus using a surface modifier having a refractive index of 1.324 or less can read information at a high speed of 7200 rpm. Among them, an apparatus using a surface modifier having a refractive index of 1.322 or less was found to be able to read information at a high speed of 8400 rpm. Furthermore, among them, an apparatus using a surface modifier having a refractive index of 1.315 or less was recognized to be capable of reading information at a high speed of 9600 rpm.
[0122]
Subsequently, the effects are summarized by the difference in the purification method of the compound forming the outermost surface layer of the magnetic recording medium used. Based on the results when the surface modifiers used were compounds 47 to 52 and 115 to 120, the perfluoropolyether having a piperonyl group was used in tetrahydrofuran and methanol in a weight of 0.5 to 20 times that of the perfluoropolyether. It was confirmed that the magnetic recording apparatus having a component consisting of the non-extracted component at the time of extraction on the surface of the magnetic recording medium can tolerate a rotational speed of 7200 rpm.
[0123]
In addition, from the results when the surface modifier used is compounds 1-36 and 69-104, perfluoropolyether having a piperonyl group is an organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and no hydroxyl group And an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and no hydroxyl group, each of which is extracted using 0.5 to 20 times the weight of the perfluoropolyether. It was confirmed that the magnetic recording apparatus having the component on the surface of the magnetic recording medium can tolerate a rotational speed of 8400 rpm.
[0124]
Furthermore, from the results when the surface modifiers used were compounds 4 to 6 and 72 to 74, perfluoropolyether having a piperonyl group is an organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and hydroxyl group As the organic solvent, ethyl acetate is used in the same weight as perfluoropolyether, dipole moment is in the range of 0 to 0.6 Debye, and n-hexane is 2.5 to 6 times that of perfluoropolyether as an organic solvent having no carboxyl group and hydroxyl group. It was confirmed that the magnetic recording apparatus having a component consisting of non-extracted components when extracted using the weight of the magnetic recording medium on the surface of the magnetic recording medium can tolerate a rotational speed of 9600 rpm.
[0125]
【The invention's effect】
According to the present invention, it is possible to provide a surface modifier having a very low scattering property among surface modifiers having a perfluoropolyether structure having a piperonyl group at the terminal. In addition, it is possible to provide a surface modifier having high thermal stability and high water repellency.
[0126]
Further, according to the present invention, it is possible to provide a magnetic recording medium having sufficient lubricity on the surface even after long-term continuous rotation. In addition, it has become possible to provide a magnetic recording medium with high thermal stability.
[0127]
Furthermore, according to the present invention, it is possible to provide a magnetic recording apparatus that can operate normally without crashing the head even if it is continuously rotated for a long time.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the configuration of a magnetic recording medium produced in Example 1. FIG.
2 is a schematic cross-sectional view showing a configuration of a hard disk drive in the magnetic recording apparatus manufactured in Example 1. FIG.
3 is a schematic diagram showing a configuration of a magnetic recording apparatus manufactured in Example 1. FIG.
[Fig. 4] It is a figure which shows the relationship between the refractive index of the compound which comprises the lubricating layer, and the thickness of a lubricating layer.
[Explanation of symbols]
1 ... Al alloy disk, 2 ... Ni-P layer, 3 ... Cr layer, 4 ... Ni-Co magnetic layer, 5 ... carbon layer, 6 ... layer made of surface modifier, 7 ... magnetic recording medium, 8 ... spindle motor, 9 ... head, 10 ... head suspension, 11 ... actuator, 12 ... mechanical seal, 13 ... cable (for data signal transfer), 14 ... cable (for actuator control), 15 ... cable (for spindle motor control) , 16 ... Hard disk drive, 17 ... Cable (for data signal transfer, actuator control, spindle motor control), 18 ... Controller, 19 ... Power supply unit, 20 ... Power cable, 21 ... Control panel , 22 ... cable, 23 ... display, 24 ... cable.

Claims (7)

A surface modifier containing a perfluoropolyether having a piperonyl group ,
The perfluoropolyether is
Extracted with an organic solvent having no dipole moment to be and carboxyl group and a hydroxyl group at least 1.0Debye, and an organic solvent having no there and carboxyl group and a hydroxyl group dipole moment in the range of 0 ~ 0.6Debye, the It consists of the non-extracted portion when
The surface modifying agent, wherein the perfluoropolyether has a refractive index of 1.322 or less . The perfluoropolyether is
An organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and a hydroxyl group, and an organic solvent having the dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and a hydroxyl group, respectively. The surface modifier according to claim 1, comprising a non-extractable component when extracted with a weight of 0.5 to 20 times that of the perfluoropolyether. The perfluoropolyether is
Using ethyl acetate as an organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and no hydroxyl group,
N-hexane is used as the organic solvent in which the dipole moment is in the range of 0 to 0.6 Debye and does not have a carboxyl group and a hydroxyl group,
Using the same amount of ethyl acetate as the perfluoropolyether,
3. The surface modifier according to claim 2, comprising a non-extracted portion when the n-hexane is extracted by using 2.5 to 6 times the weight of the perfluoropolyether. A magnetic layer comprising at least one recording layer on a support, and a film containing a perfluoropolyether having a piperonyl group as an outermost layer on the surface of the recording layer or a protective layer provided outside the recording layer A recording medium,
The perfluoropolyether is
Extraction using an organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and a hydroxyl group, and an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and a hydroxyl group It consists of the non-extracted portion when
The perfluoropolyether has a refractive index of 1.322 or less. The perfluoropolyether is
An organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and a hydroxyl group, and an organic solvent having the dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and a hydroxyl group, respectively. 5. The magnetic recording medium according to claim 4, wherein the magnetic recording medium comprises a non-extracted portion extracted with a weight of 0.5 to 20 times that of the perfluoropolyether. The perfluoropolyether is
Using ethyl acetate as an organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and no hydroxyl group,
N-hexane is used as the organic solvent in which the dipole moment is in the range of 0 to 0.6 Debye and does not have a carboxyl group and a hydroxyl group,
Using the same amount of ethyl acetate as the perfluoropolyether,
The magnetic recording medium according to claim 5, comprising a non-extracted portion when the n-hexane is extracted by using 2.5 to 6 times the weight of the perfluoropolyether. In a magnetic recording apparatus having at least a magnetic recording medium for recording information and a head for writing / erasing information on the magnetic recording medium and reading information from the magnetic recording medium,
A layer containing a perfluoropolyether having a piperonyl group is on the outermost surface of the magnetic recording medium;
The perfluoropolyether is
Extraction using an organic solvent having a dipole moment of 1.0 Debye or more and having no carboxyl group and a hydroxyl group, and an organic solvent having a dipole moment in the range of 0 to 0.6 Debye and having no carboxyl group and a hydroxyl group It consists of the non-extracted portion when
The perfluoropolyether has a refractive index of 1.322 or less.

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