JP4368447B2 - Manufacturing method of glass substrate for magnetic disk - Google Patents

Description

但し、
【００４９】
【数２】

ここで、ｎはＡＦＭのデータポイント数、Ｚｉはｉ番目のＡＦＭのデータ値を表す。
【００５０】
また、このときの測定領域のデータポイント数は６５５３６点（縦又は横の辺の長さ当たり２５６点）以上で定義されるものとする。
なお、この発明の磁気ディスク用ガラス基板は、Ｒａが０．４〜３．０ｎｍであり、ＡＲが１４以下である。このガラス基板は、ＣＳＳ方式はもちろんのこと、磁気ディスク停止時に磁気ヘッドが磁気ディスクと非接触な位置に格納されるランプロード方式又は磁気ヘッドが磁気ディスクに常時接触しているコンタクト方式の磁気記録装置への利用に適しており、高密度化と粘着の問題を同時に解決することができる。
【００５１】
次に、ガラス基板材料を構成するガラスの組成について説明する。
基板材料としてのガラスは、アルミノシリケートガラス、結晶化ガラス、ソーダライムガラス等のいずれも使用されるが、それらのうちモル％で表して次のような組成を有するアルミノシリケートガラスが好適である。このアルミノシリケートガラスは、基板材料表面にアスペリティを有しない微細な凹凸を形成することができるからである。
【００５２】
酸化珪素（ＳｉＯ₂ ） ４０〜７２％、
酸化アルミニウム（Ａｌ₂ Ｏ₃ ） ０．５〜２５％、
酸化リチウム（Ｌｉ₂ Ｏ） ０〜２２％、
酸化ナトリウム（Ｎａ₂ Ｏ） ０〜１４％、
酸化カリウム（Ｋ₂ Ｏ） ０〜１０％、
Ｒ₂ Ｏ ２〜３０％
但し、Ｒ₂ Ｏ＝Ｌｉ₂ Ｏ＋Ｎａ₂ Ｏ＋Ｋ₂ Ｏ
酸化マグネシウム（ＭｇＯ） ０〜２５％、
酸化カルシウム（ＣａＯ） ０〜２５％、
酸化ストロンチウム（ＳｒＯ） ０〜１０％、
酸化バリウム（ＢａＯ） ０〜１０％、
ＲＯ ０〜４０％
但し、ＲＯ＝ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ
酸化チタン（ＴｉＯ₂ ） ０〜１０％
酸化ジルコニウム（ＺｒＯ₂ ） ０〜１０％
以上の成分の合計が９５％以上
このような組成を有するガラスは、フロート法により製造可能で、溶融温度が低く、化学強化処理後の耐水性や耐候性が良好で、しかも金属製品と組み合わせて使用可能な膨張係数を有する。フロート法は、溶融スズを収容し、上部空間を還元性雰囲気とした高温のバス中へ、一端から溶融ガラスを流入し、他端からガラスを引き延ばして板状のガラスを製造する方法である。このフロート法によれば、得られるガラスは両面が平行でゆがみがなく、表面光沢があるとともに、多量生産が可能で、板幅の変更も容易であり、自動化を図ることも容易である。
【００５３】
前記のようなガラス組成において、ＳｉＯ₂ はガラスの主要成分であり、必須の構成成分である。その含有量が４０重量％未満の場合、強化処理のためのイオン交換後の耐水性が悪化し、７２重量％を越える場合、ガラス融液の粘性が高くなりすぎ、溶融や成形が困難になるとともに、膨張係数が小さくなりすぎる。
【００５４】
Ａｌ₂ Ｏ₃ はイオン交換速度を速くし、イオン交換後の耐水性を向上させるために必要な成分である。その含有量が０．５重量％未満の場合、そのような効果が不十分であり、２５重量％を越える場合、ガラス融液の粘性が高くなりすぎ、溶融や成形が困難になるとともに、膨張係数が小さくなりすぎる。
【００５５】
Ｌｉ₂ Ｏはイオン交換を行うための必須の構成成分であるとともに、溶解性を高める成分である。その含有量が２２重量％を越える場合、イオン交換後の耐水性が悪化するとともに、液相温度が上がり、成形が困難となる。
【００５６】
Ｎａ₂ Ｏは溶解性を高める成分である。その含有量が１４重量％を越える場合、イオン交換後の耐水性が悪化する。また、Ｋ₂ Ｏは溶解性を高める成分であり、その含有量が１０重量％を越える場合、イオン交換後の表面圧縮応力が低下する。
【００５７】
さらに、上記Ｌｉ₂ Ｏ、Ｎａ₂ Ｏ及びＫ₂ Ｏの合計Ｒ₂ Ｏが２重量％未満の場合、ガラス融液の粘性が高くなりすぎ、溶融や成形が困難となるとともに、膨張係数が小さくなりすぎ、３０重量％を越える場合、イオン交換後の耐水性が悪化する。
【００５８】
ＭｇＯは溶解性を高める成分であり、２５重量％を越える場合、液相温度が上がり、成形が困難になる。ＣａＯは溶解性を高める成分であるとともに、イオン交換速度を調整するための必須成分である。その含有量が２５重量％を越える場合、液相温度が上がり、成形が困難になる。ＳｒＯは溶解性を高める成分であるとともに、液相温度を下げるのに有効な成分である。その含有量が１０重量％を越える場合、ガラスの密度が大きくなるとともに、製造コストが上昇する。ＢａＯは溶解性を高める成分であるとともに、液相温度を下げるのに有効な成分である。その含有量が１０重量％を越える場合、ガラスの密度が大きくなるとともに、製造コストが上昇する。
【００５９】
さらに、上記ＭｇＯ、ＣａＯ、ＳｒＯ及びＢａＯの合計ＲＯが、４０重量％を越える場合、液相温度が上がり、成形が困難となる。
ＴｉＯ₂ が１０重量％を越える場合、ガラス素地の品質が悪化するとともに、製造コストが上昇する。ＺｒＯ₂ が１０重量％を越える場合、ガラス素地の溶融温度又は粘性が上昇し、ガラス基板材料の製造が困難になりやすい。
【００６０】
前記ガラスは、磁気ディスク用基板として要求される強度を維持するため、その表面に化学強化処理が施されていることが望ましい。この化学強化処理は、ガラスがその組成中に含まれる一価の金属イオンよりイオン半径が大きな一価の金属イオンを含有する溶融塩中に浸漬され、ガラス中の金属イオンと溶融塩中の金属イオンとがイオン交換されることにより行われる。
【００６１】
例えば、ガラス基板を加熱された硝酸カリウム溶液中に浸漬することにより、ガラス基板表面近傍のナトリウムイオンがそれより大きなイオン半径を有するカリウムイオンに置き換えられ、その結果圧縮応力が作用してガラス基板表面が強化される。また、ガラス基板を硝酸銀（０. ５〜３％）と硝酸カリウム（９７〜９９. ５％）の混合溶液中に、３０分から１時間浸漬してもよい。それにより、銀イオンがガラス基板表面に速やかに浸透され、ガラス基板表面の強化が促進される。また、硝酸銀と硝酸カリウムの混合溶液に代えて、硝酸カリウムと硝酸ナトリウムの混合溶液を使用することができる。
【００６２】
以上のように、この実施形態によれば、次のような効果が発揮される。
・ 実施形態の磁気ディスク用ガラス基板によれば、基板材料の磁気記録表面をスクラブエッチングすることにより、アスペリティを含まない微細な凹凸を有するガラス基板が簡単に得られる。このため、磁気ヘッドのグライドヒットを防止できるとともに、磁気ヘッドの損傷を防止できる。
【００６３】
・ 実施形態の磁気ディスク用ガラス基板によれば、基板素材として前述した特定組成を有するアルミノシリケートガラスを用いることにより、アスペリティが存在しない微細な凹凸を容易かつ確実に形成することができる。
【００６４】
・ 実施形態の磁気ディスク用ガラス基板によれば、アルミノシリケートガラスは溶解温度が低く、成形性に優れているため、ガラス基板材料をフロート法により容易に製造でき、得られたガラス基板は、高平坦性を有する品質の高いものである。
【００６５】
・ 実施形態の磁気ディスク用ガラス基板の製造方法によれば、基板材料の磁気記録表面を酸性処理剤の存在下に、摩擦体としてのパッドによってスクラブエッチングすることにより、基板材料の表面にアスペリティが存在しないように微細な凹凸を有する基板を歩留りを向上させて容易に得ることができる。
【００６６】
・ 実施形態の磁気ディスク用ガラス基板の製造方法によれば、酸性処理剤として、フッ酸、硫酸、リン酸、硝酸及びヘキサフルオロ珪酸から選択される少なくとも１種の酸を使用することにより、ガラスに対する腐食性が大きいため、スクラブエッチングを効果的に行うことができる。
【００６７】
・ 実施形態の磁気ディスク用ガラス基板の製造方法によれば、パッドが基板材料よりも硬度が小さく、かつ酸性処理剤に対する耐酸性を有することにより、基板材料を傷付けることなく、しかも酸性処理剤によって損傷を受けることなく、微細な凹凸を形成することができる。
【００６８】
・ 実施形態の磁気ディスク用ガラス基板の製造方法によれば、スクラブエッチングは酸性処理剤の濃度が０．０１〜１重量％、温度が５〜６０℃及び処理時間が１〜３００秒の条件下で行われる。このため、適切な条件にてアスペリティを含まない微細な凹凸を効率的に形成することができる。
【００６９】
【実施例】
次に、実施例及び比較例を挙げ、前記実施形態をさらに具体的に説明する。
（実施例１）
次のような組成（モル％）を有するアルミノシリケートガラス製の基板材料表面をスクラブエッチングした。
【００７０】
ＳｉＯ₂ ６６％、Ａｌ₂ Ｏ₃ １０％、Ｌｉ₂ Ｏ ７％、Ｎａ₂ Ｏ １０％、ＭｇＯ ３％、ＣａＯ ４％。
化学強化された直径２．５インチのアルミノシリケートガラス基板材料の表面を精密研磨した後、純水を用いてスクラブ洗浄した。次いで、０．１重量％濃度のフッ酸水溶液中（３５℃）にてスクラブエッチングしながら１．５分間浸漬した後に引き上げ、さらにｐＨ１２の水酸化カリウム溶液に２．５分間浸漬した後引き上げた。その後、再度純水を用いてスクラブ洗浄した。
【００７１】
スクラブエッチングは、次のようにして行った。図１及び図２に示すように、パッド１１はガラス基板材料１２よりも大きな円盤状に形成され、その上下両面には斜め放射状に延びる１２本のスクラブ用突条１３が設けられている。この突条１３によりフッ酸水溶液がよく攪拌されるようになり、新鮮なフッ酸水溶液が基板材料１２に供給され易くなる。このパッド１１は、ポリビニルアルコール製のスポンジ〔多孔質体、鐘紡（株）の商品名ベルクリン〕により形成されている。基板材料１２とパッド１１とはパッド１１のスクラブ用突条１３が基板材料１２の磁気記録表面１２ａに摺接するように図４（ｂ）の如く、それぞれモータにより逆方向に回転駆動される。それにより、基板材料１２の磁気記録表面１２ａがパッド１１のスクラブ用突条１３の表面で一定間隔をおいて周期的にスクラブされる。パッド１１の回転数は１００ｒｐｍである。フッ酸水溶液に基板材料１２を浸漬すると同時にパッド１１を接触させ、パッド１１を引き上げるまでスクラブし続ける。
【００７２】
この操作後、磁気記録表面１２ａの縦、横１０μｍの領域をＡＭＦにより測定したところ、その磁気記録表面１２ａには等方的かつ凹部又は凸部の間に実質的に平坦な部分を有さない連続形状をなす微小凹凸が形成されていた。この微小凹凸の三次元的に定義した平均面粗さ（Ｒａ）は１．０ｎｍであり、振幅は１０ｎｍであり、代表的な周期は０．３μｍであった。また、アスペリティレシオ（ＡＲ＝Ｒｚ／Ｒａ）は１０であった。
【００７３】
次に、上記のようにして得られたガラス基板の表面に、スパッタリングによって順次チタン（Ｔｉ）−ケイ素（Ｓｉ）シード層（２５ｎｍ）、クロム（Ｃｒ）−モリブデン（Ｍｏ）下地層（２５ｎｍ）、コバルト（Ｃｏ）−ニッケル（Ｎｉ）−クロム（Ｃｒ）−タンタル（Ｔａ）磁性層（２０ｎｍ）、炭素（Ｃ）保護層（１０ｎｍ）を形成した。その後、潤滑剤としてパーフルオロポリエーテル系のものを塗布して潤滑層（２ｎｍ）を形成し、磁気ディスクとした。
【００７４】
この磁気ディスクにおける潤滑層表面の三次元的に定義した平均面粗さ（Ｒａ）は１．０ｎｍであり、振幅は１０ｎｍであった。すなわち、基板表面に形成した微小凹凸がそのまま潤滑層表面まで残っていた。
【００７５】
得られた磁気ディスクをランプロード方式のハードディスク装置のスピンドルに装着し、３６００ｒｐｍで回転させ、またＡＥセンサ付きの磁気ヘッドを浮上させたままでシーク動作を行い、ＡＥセンサの出力をモニターした。その結果、シーク動作を行っても磁気ヘッドと磁気ディスクとが激しく衝突したことを示すＡＥセンサの出力は認められず、磁気ヘッドのグライドエラーもなかった。また、フライングハイトを１５ｎｍに設定してグライドテストを行ったところ、グライドヒットは生じなかった。さらに、１０万回のシーク動作を繰り返したが、ヘッドクラッシュは生じなかった。
（比較例１）
化学強化された２．５インチのアルミノシリケートガラス基板の表面を精密研磨した後、純水を用いてスクラブ洗浄した。次いで、０．００５重量％濃度のフッ酸水溶液中にて揺動しながら３０分間浸漬した後に引き上げ、さらにｐＨ１２の水酸化カリウム溶液に２．５分間浸漬した後引き上げた。
【００７６】
その後、再度純水を用いてスクラブ洗浄した。この操作後、ガラス基板の表面の縦、横１０μｍの領域をＡＭＦにより測定したところ、その表面には高さが数ｎｍ〜十数ｎｍのアスペリティが離散的に多数存在する微小凹凸が形成されていた。この微小凹凸の三次元的に定義した平均面粗さ（Ｒａ）は１．０ｎｍであったが、アスペリティが存在しているため、振幅や代表的な周期を評価することができなかった。また、アスペリティレシオ（ＡＲ＝Ｒｚ／Ｒａ）は１６．７であった。
【００７７】
次に、上記のようにして得られたガラス基板の表面に、スパッタリングによって順次チタン（Ｔｉ）−ケイ素（Ｓｉ）シード層（２５ｎｍ）、クロム（Ｃｒ）−モリブデン（Ｍｏ）下地層（２５ｎｍ）、コバルト（Ｃｏ）−ニッケル（Ｎｉ）−クロム（Ｃｒ）−タンタル（Ｔａ）磁性層（２０ｎｍ）、炭素（Ｃ）保護層（１０ｎｍ）を形成した。その後、潤滑剤としてパーフルオロポリエーテル系のものを塗布して潤滑層（２ｎｍ）を形成し、磁気ディスクとした。
【００７８】
この磁気ディスクにおける潤滑層表面の三次元的に定義した平均面粗さ（Ｒａ）は１．０ｎｍであり、Ｒａ／Ｒｚ比は０．０６であった。すなわち、基板表面に形成したアスペリティを含む微小凹凸がそのまま潤滑層表面まで残っていた。
【００７９】
得られた磁気ディスクをランプロード方式のハードディスク装置のスピンドルに装着し、３６００ｒｐｍで回転させ、またＡＥセンサ付きの磁気ヘッドを浮上させたままでシーク動作を行い、ＡＥセンサの出力をモニターした。その結果、シーク動作を行ったとき磁気ヘッドと磁気ディスクとが激しく衝突したことを示すＡＥセンサの出力が多数認められた。また、１０万回のシーク動作を繰り返したところ、途中でヘッドクラッシュが生じた。
（実施例２）
前記実施例１において、フッ酸溶液中でのガラス基板を２０分間スクラブエッチングした。その他は実施例１と同様に操作した。
【００８０】
その結果、ガラス基板の平均面粗さ（Ｒａ）は１．５ｎｍであり、アスペリティレシオ（ＡＲ＝Ｒｚ／Ｒａ）は１０であった。また、実施例１と同様に磁気ヘッドの損傷やグライドエラーは生じなかった。さらに、１０万回のシーク動作を繰り返したが、ヘッドクラッシュは生じなかった。
【００８１】
なお、前記実施形態を以下のように変更して具体化してもよい。
・ 前記微細な凹凸をガラス基板のＣＳＳゾーンにのみ設けてもよい。
このように構成した場合、ＣＳＳゾーン以外の部分を鏡面状に保つことが可能なため、磁気ディスクメディアとした場合、磁気ヘッドの低浮上化が可能になり、磁気ディスク装置の高記録密度化を達成することができる。
【００８２】
・ 前記実施例のパッド１１に設けたスクラブ用突条１３をパッド１１の磁気記録表面１２ａのみ（片面のみ）に設けてもよい。
このように構成した場合、スクラブ用突条１３の構成を簡単にして容易に形成することができる。
【００８３】
・ 前記円柱状をなすパッド１１をテーパ状に形成したり、円筒状に形成したりしてもよい。
・ 前記スクラブ用突条１３の断面形状を、半円状、三角形状等にしてもよい。
【００８４】
また、前記実施形態より把握される技術的思想について以下に記載する。
【００８５】
・ 前記酸性処理剤には、キレート剤及び界面活性剤の少なくとも１種の添加剤が配合される請求項３に記載の磁気ディスク用ガラス基板の製造方法。
【００８６】
このように構成した場合、基板材料に対するスクラブエッチングの性能を向上させることができる。
【００８７】
・ 前記スクラブエッチングは、パッドを回転又は回転かつ公転させることにより行われるものである請求項１から請求項４のいずれか一項に記載の磁気ディスク用ガラス基板の製造方法。
【００８８】
この方法によれば、ガラス基板材料の磁気記録表面に対するスクラブエッチングを容易に、しかも有効に行うことができる。
・ 前記スクラブエッチングは、パッドを回転させながら揺動させることにより行われるものである請求項１から請求項４のいずれか一項に記載の磁気ディスク用ガラス基板の製造方法。
【００８９】
この方法によれば、ガラス基板材料の磁気記録表面に対するスクラブエッチングを容易に、しかも有効に行うことができる。
【００９０】
【発明の効果】
この発明は以上のように構成されているため、次のような効果を奏する。
請求項１に記載の発明の磁気ディスク用ガラス基板の製造方法によれば、基板表面にアスペリティが存在しないように微細な凹凸を形成することができ、磁気ヘッドのグライドヒットを防止することができるとともに、磁気ヘッドの損傷を防止できる磁気ディスク用ガラス基板を歩留りを向上させて容易に得ることができる。
【００９１】
請求項２に記載の発明の磁気ディスク用ガラス基板の製造方法によれば、請求項１に記載の発明の効果に加え、酸性処理剤として、フッ酸、硫酸、リン酸、硝酸及びヘキサフルオロ珪酸から選択される少なくとも１種の酸を使用することにより、ガラスに対する腐食性が大きいため、スクラブエッチングを効果的に行うことができる。
【００９２】
請求項３に記載の発明の磁気ディスク用ガラス基板の製造方法によれば、請求項１又は請求項２に記載の発明の効果に加え、パッドが基板材料よりも硬度が小さく、かつ酸性処理剤に対する耐酸性を有することにより、基板材料を傷付けることなく、しかも酸性処理剤によって損傷を受けることなく、微細な凹凸を形成することができる。
【００９３】
請求項４に記載の発明の磁気ディスク用ガラス基板の製造方法によれば、請求項１〜請求項３のいずれかに記載の発明の効果に加え、スクラブエッチングは酸性処理剤の濃度が０．０１〜１重量％、温度が５〜６０℃及び処理時間が１〜３００秒の条件下で行われる。このため、適切な条件にてアスペリティを含まない微細な凹凸を効率的に形成することができる。
【図面の簡単な説明】
【図１】 実施例におけるスクラブエッチングの状態を示す平面図。
【図２】 図１の２−２線における断面図。
【図３】 （ａ）はスクラブエッチング用の円柱状をなすパッドを示す斜視図、（ｂ）はパッドを回転させてスクラブエッチングする状態を示す平面図、（ｃ）は（ｂ）の状態からさらにガラス基板材料の半径方向に揺動させる状態を示す平面図。
【図４】 （ａ）はスクラブエッチング用の円板状をなすパッドを示す斜視図、（ｂ）はパッドを回転させてスクラブエッチングする状態を示す平面図、（ｃ）は（ｂ）の状態からさらにガラス基板材料の半径方向に揺動させる状態を示す平面図、（ｄ）は（ｃ）の状態からさらにガラス基板材料の周りを公転する状態を示す平面図。
【符号の説明】
１１…摩擦体としてのパッド、１２…ガラス基板材料、１２ａ…磁気記録表面。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a glass substrate for a magnetic disk used in a magnetic disk device for storing data in a personal computer or the like.PlankIt relates to a manufacturing method. More specifically, a glass substrate for a magnetic disk in which fine irregularities are formed on the surface by scrub etching the surface of the substrate.PlankIt relates to a manufacturing method.
[0002]
[Prior art]
In general, in a fixed magnetic disk apparatus, a CSS (Contact Start Stop) in which the magnetic head contacts the disk surface when the disk is stationary, and the magnetic head slides while contacting the disk surface when the disk is started and stopped. Many mechanisms called methods are used.
[0003]
In this CSS system, moderately fine surface irregularities (called textures) are formed on the disk to prevent stiction (adhesion) that occurs when the disk is started and stopped and to reduce frictional force. Has been. The unevenness is formed on the entire surface or a part of the magnetic recording surface on which the magnetic layer of the disk is formed. When the unevenness is formed only in a part (CSS zone), the magnetic head moves (glide) to the CSS zone where the unevenness is formed at an appropriate time during the CSS operation. Further, even when the power is turned off while the disk is rotating, the disk moves to the CSS zone.
[0004]
In particular, when unevenness is formed only in a part, the remaining part can maintain a mirror-like smoothness, so that the magnetic head can be lowered. Therefore, it is suitable for increasing the recording density of the magnetic disk device.
[0005]
By the way, a so-called aluminum substrate in which an aluminum (Al) -magnesium (Mg) alloy substrate is subjected to nickel (Ni) -phosphorus (P) plating has been widely used as the disk substrate. As a method of applying a texture to the aluminum substrate, it has been widely performed to concentrically damage the substrate with a polishing tape. However, with this method, when further lowering of the magnetic head is required, it is difficult to achieve both prevention of stiction and reduction of frictional force.
[0006]
Therefore, for example, in Japanese Patent Laid-Open No. 10-134348, a magnetic layer and a protective layer are sequentially formed on a glass substrate, and the surface of the protective layer is etched to form irregularities on the surface of the protective layer. Techniques to do this are disclosed.
[0007]
In this prior art, irregularities are formed by etching on the surface of the protective layer provided on the most surface side on the glass substrate. This unevenness is the maximum surface roughness R_maxIs precisely polished so as to be 30 angstroms.
[0008]
Japanese Patent Application Laid-Open No. 7-153059 discloses a technique for forming irregularities directly on the glass substrate surface by etching the glass substrate surface with a mixed solution of potassium fluoride and hydrofluoric acid. In the example of this publication, irregularities having a protrusion height of 130 to 400 angstroms (Å) are formed by measurement with a stylus type surface roughness meter (trade name “Taristep” manufactured by Rank Taylor Bobson).
[0009]
[Problems to be solved by the invention]
However, when the irregularities are formed by etching, convex portions (asperities) that protrude beyond the average height of the convex portions may occur discretely. In the prior art, the unevenness is formed on the surface of the glass substrate or the protective layer located on the outermost surface, and asperity exists there. When such asperity exists, the magnetic head causes a glide hit, which causes a decrease in yield when manufacturing a magnetic disk, and causes a head crush in an actual magnetic disk device. Therefore, when the unevenness is formed on the surface of the glass substrate or the protective layer by the etching process, it is required to prevent the occurrence of asperity as described above.
[0010]
  The present invention has been made paying attention to the problems existing in the prior art as described above. The purpose is to form a glass substrate for a magnetic disk that can form fine irregularities so that there is no asperity on the substrate surface, prevent glide hit of the magnetic head, and prevent damage to the magnetic head.BoardAn object of the present invention is to provide a method of manufacturing a glass substrate for a magnetic disk that can be easily obtained by improving the yield.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, the glass substrate for a magnetic disk of the invention according to claim 1In the manufacturing method, after the surface of the chemically reinforced aluminosilicate glass substrate material is precisely polished, the magnetic recording surface of the glass substrate material is in the presence of an acidic treatment agent and is larger in disk shape than the glass substrate material as a friction body. And scrubbing with a pad provided with scrubbing protrusions extending radially on both surfaces thereof, thereby forming fine irregularities so that asperity does not occur on the magnetic recording surface of the glass substrate material. Is.
[0012]
  The method for producing a glass substrate for a magnetic disk according to claim 2 comprises:In the invention according to claim 1, the acidic treatment agent is at least one acid selected from hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, and hexafluorosilicic acid.
[0013]
  The method for producing a glass substrate for a magnetic disk according to claim 3 comprises:In the invention according to claim 1 or 2, the pad has hardness lower than that of the glass substrate material and has acid resistance against the acid treatment agent.
[0014]
  The method for producing a glass substrate for a magnetic disk according to claim 4 comprises:The scrub etching according to any one of claims 1 to 3, wherein the scrub etching has a concentration of an acidic treatment agent of 0.01 to 1% by weight, a temperature of 5 to 60 ° C, and a treatment time of 1 to 300. It is performed under the condition of seconds.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The glass substrate for a magnetic disk is such that fine irregularities are continuously formed isotropically on the magnetic recording surface side of the glass substrate material, and the irregularities do not include asperity. The irregularities are formed by scrub etching the magnetic recording surface of the substrate material.
[0017]
On the glass substrate, a glass substrate for a magnetic disk is formed by sequentially providing an underlayer for improving magnetic properties, a magnetic medium layer, a protective layer, and a lubricating layer. A plurality of intermediate films may be further formed between the glass substrate and the underlayer for the purpose of further improving the magnetic characteristics and improving the adhesive force.
[0018]
A glass substrate for a magnetic disk is manufactured by scrubbing a magnetic recording surface of a glass substrate material with a pad as a friction body in the presence of an acidic treatment agent. The acidic treating agent is preferably at least one acid selected from hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, and hexafluorosilicic acid. Since this acidic treatment agent is highly corrosive to glass, scrub etching can be performed effectively. In addition, in order to improve the scrub etching performance, this acidic treatment agent contains at least one additive of a chelating agent such as ethylenediaminetetraacetic acid (EDTA) or nitrotriacetic acid (NTA) and a surfactant as necessary. You may mix | blend. The amount of the additive is usually in the range of 0.001 to 10% by weight in the treatment agent.
[0019]
The following three methods are mentioned as a supply method of the acidic processing agent to the glass substrate material surface.
(1) A method of completely or partially immersing a glass substrate material in an acidic treatment agent.
(2) A method of injecting or spraying an acidic treatment agent from a hole such as a nozzle onto the surface of a glass substrate material.
(3) A method of supplying the acidic treatment agent to the surface of the glass substrate material through a pad impregnated with the acidic treatment agent in advance.
[0020]
Among these methods, the method (1) is desirable for minimizing the scattering and volatilization of the acidic treatment agent, and fine irregularities are formed so that there is no asperity on the surface of the glass substrate material. In order to achieve this, it is desirable to adopt the method (3).
[0021]
The pad is preferably made of an organic material such as a synthetic resin, an inorganic material, a metal material, or a composite material thereof having a hardness lower than that of the substrate material and having acid resistance against an acidic treatment agent and causing no corrosion or dissolution. As shown in FIG. 3A, the pad 11 is formed in a columnar shape, for example, and its length is set to a length substantially corresponding to the length obtained by subtracting the inner diameter from the outer diameter of the glass substrate material 12. As shown in FIG. 3B, the pad 11 is disposed so as to extend in the radial direction of the substrate material 12, and the pad 11 also rotates so as to be in sliding contact with the surface of the rotating substrate material 12. Alternatively, as shown in FIG. 3C, the pad 11 swings in the radial direction of the substrate material 12 in the state of FIG. At this time, the surface of the substrate material 12 is rubbed with the outer peripheral surface of the pad 11.
[0022]
Further, as shown in FIG. 4A, the pad 11 is formed in a disc shape, and the size thereof is substantially the same as that of the substrate material 12. Then, as shown in FIG. 4B, the pad 11 is placed so as to be in sliding contact with the surface of the rotating substrate material 12 and rotates in the opposite direction to the substrate material 12. As shown in FIG. 4C, the pad 11 swings in the radial direction of the substrate material 12 in the state of FIG. Further, as shown in FIG. 4D, in the state of FIG. 4B, the pad 11 revolves on the substrate material 12 as shown by a two-dot chain line. At this time, the surface of the substrate material 12 is rubbed with the main surface of the pad 11.
[0023]
Further, in either case of FIG. 3 and FIG. 4, the substrate material 12 may rotate following the rotation or revolution of the pad 11. Further, the substrate material 12 is fixed and does not need to rotate at all. In addition, the substrate material 12 may be driven by a motor or the like and rotate regardless of the movement of the pad 11.
[0024]
The surface shape of the pad is fibrous, bulk, bulky, porous, or a composite shape thereof. The pad may have any shape as long as it can scrub a substrate material having a diameter of 0.8 to 3.5 inches, but the following shape is desirable.
[0025]
That is, in the case of a disk shape, the diameter is 20 to 150 mm and the thickness is 3 to 20 mm. If the thickness of the pad is less than 3 mm, the rigidity is insufficient, uniform contact between the pad and the substrate becomes difficult, and asperity is likely to occur. On the other hand, if the thickness is greater than 20 mm, the effect cannot be expected even though the pad manufacturing cost increases.
[0026]
In addition, irregularities having an arbitrary shape and size may be formed on the surface of the disk, and a hole for fixing the pad to the rotating shaft may be provided at the center of the disk. In the case of a cylindrical shape, the diameter is 8 to 40 mm and the height is 10 to 100 mm. In addition, irregularities having an arbitrary shape and size may be formed on the peripheral surface of the cylinder, and a hole for fixing the pad to the rotating shaft may be provided in the center of the cylinder in the axial direction.
[0027]
Contact pressure between pad and glass substrate is 1 to 5000 g / cm²Is preferable, particularly when the pad is disk-shaped, it is 100 to 400 g / cm.²Is preferred. This contact pressure is 1 g / cm²As it becomes smaller, it takes time to remove asperity, while 5000 g / cm.²If it is larger, contact scratches may occur on the substrate surface. Further, the rotational speed of the pad is preferably 20 to 4000 rpm, particularly preferably 20 to 500 rpm when the pad is disk-shaped, and more preferably 200 to 2000 rpm when the pad is cylindrical. This is because the contact with the substrate is likely to be non-uniform if the rotational speed of the pad is too low or too high. The contact time between the pad and the substrate material is preferably 1 to 300 seconds.
[0028]
As for the scrub etching conditions, when the acidic treatment agent is hydrofluoric acid, the concentration is preferably 0.01 to 1% by weight, the temperature is 5 to 60 ° C., and the treatment time is 1 to 300 seconds. When the concentration is lower than 0.01% by weight, the reaction rate is slow and impractical. On the other hand, when the concentration is higher than 1% by weight, foreign substances are likely to be generated on the substrate surface, and the scrub etching apparatus is significantly corroded. Further, in order to lower the temperature below 5 ° C., a large cooling device is separately required. On the other hand, when the temperature is higher than 60 ° C., volatilization is remarkably difficult to control the concentration, and exhaust equipment is required.
[0029]
When the acidic treating agent is a mixed solution of hydrofluoric acid and sulfuric acid, the concentration of hydrofluoric acid is 0.01 to 1% by weight, the concentration of sulfuric acid is 0.01 to 1% by weight, and the mixing ratio of hydrofluoric acid and sulfuric acid The (weight ratio) is preferably 1: 100 to 100: 1, the temperature is 5 to 60 ° C., and the treatment time is 1 to 300 seconds. In these cases, you may mix | blend the said additive with an acidic processing agent. Furthermore, it is preferable to set conditions such that the type, concentration and temperature of the acidic treatment agent are such that the pH at which elution or dissolution of the elements constituting the glass becomes remarkable is 3 or less, preferably 2 or less. However, when the pH is smaller than 0, the same problem as in the case where the concentration of the acidic treatment agent is too high is likely to occur.
[0030]
After scrub etching in the presence of an acidic treatment agent, an immersion treatment with an alkaline treatment agent is performed. By performing this treatment, it is possible to prevent foreign substances made of an alkali metal salt from being deposited on the substrate surface. That is, the durability of the substrate can be improved. As the alkaline treatment agent, at least one kind of alkali metal salts such as potassium hydroxide, phosphates, silicates, aqueous ammonia, and the like is used. Moreover, the additive mentioned above can also be mix | blended with this alkaline processing agent. Further, the type, concentration and temperature of the alkaline treatment agent are silicon dioxide (SiO2) which is the main component constituting the glass.₂It is preferable to set the conditions so that the pH at which the dissolution of) becomes remarkable is 9 or more, preferably 11 or more.
[0031]
By the way, in the field of surface science, it is generally known that the composition, structure, and the like differ in some form between the outermost surface layer and the bulk layer on the solid surface. The present inventors considered that there is some difference between the outermost surface layer and the bulk layer with respect to the glass substrate, and conducted various experiments. For example, an etching process was performed while changing the polishing and storage conditions of the glass substrate, and the state of the substrate surface after the process was observed. Through these experiments, it was found that the state of the substrate surface was different for each condition. From the results of the experiment, the present inventors have found that, at a depth of about several tens to 1000 nm from the outermost surface of the glass substrate, a mechanically altered layer due to mechanical distortion during polishing, a cleaning agent and a substrate before etching It has been estimated that a chemically altered layer due to ion exchange with the storage atmosphere is unevenly present.
[0032]
Therefore, the occurrence of asperity when etching is performed is that the uneven presence of the altered layer present on the surface of the substrate material as described above appears as a local difference on the surface of the substrate material in the etching process. Conceivable.
[0033]
Other causes of asperity include insoluble or hardly soluble foreign substances that are generated when the acidic treating agent reacts with glass. In this case, insoluble or hardly soluble foreign matter itself becomes asperity, or due to the masking effect of foreign matter in etching, the height difference due to etching occurs between the portion where the foreign matter is attached and the portion where the foreign matter is not attached. It is also possible that it will occur.
[0034]
In order to suppress these occurrences and form asperities without asperities, a method of etching the surface of the substrate material while rubbing with a pad made of resin or the like and having a hardness lower than that of the substrate material, that is, scrub etching is effective. is there.
[0035]
There are three reasons for this.
1) By using an appropriate processing agent for the substrate material and performing scrub etching under appropriate conditions, irregularities having a desired roughness can be formed.
[0036]
2) Since the concentration of the treatment agent in the vicinity of the top of the asperity is higher than the portion where no asperity is formed, the etching reaction proceeds selectively, and the generation of asperity is suppressed.
[0037]
3) Foreign matter present on the surface of the substrate material is removed by mechanical force due to friction with the pad.
In scrub etching on the surface of the substrate material, the diffusion constant of the reaction component of the substrate material and the acidic treatment agent, and the initial concentration of the reaction component are constant at any position near the surface of the substrate material regardless of the presence or absence of asperity. . However, the vicinity of the top of the asperity is selective because the contact pressure with the pad is higher (or the number of times of contact) is higher than other substrate material surfaces, so the concentration of reaction components is high, that is, the etching rate is high. Etching is likely to occur, and it is considered that the growth of asperity is hindered.
[0038]
Asperity has been described above. Specifically, when an arbitrary area on the surface of the substrate material is measured with an atomic force microscope (AFM), it is in a protrusion having an average height that occupies most of the measurement surface. A protrusion that is relatively high compared to a protrusion that is discrete and partially present and has an average height.
[0039]
Here, the asperity when the protrusion X having the height h2 larger than h1 exists in the protrusion group having the average height h1 will be considered.
As a method of defining asperity most easily, there is a method of determining it by an absolute value of height. That is, the degree of the relative height of the protrusion X with respect to the protrusion group having the average height h1 is determined by taking the ratio of the height h2 of a certain protrusion X and the average height h1 of the protrusion. The Accordingly, the degree of height of the protrusion X (hereinafter, abbreviated as asperity ratio, AR) is expressed by the following formula (1).
[0040]
AR = h2 / h1 (1)
However, AR in equation (1) is for each asperity. On the other hand, there are often one or more asperities on the surface of the substrate material, and it is generally difficult to determine h1 and h2 of each protrusion. Therefore, in order to easily obtain the AR value, the h1 and h2 values may be approximated using standardized known parameters.
[0041]
Here, it is considered that Ra (average surface roughness) is the most suitable parameter for h1, and Rz (ten-point average surface roughness) is the most suitable parameter for h2. When these parameters are used, AR is expressed by the following equation (2).
[0042]
AR = Rz / Ra (2)
Note that Rmax (maximum surface roughness) may be used as a parameter approximating the h2 value. However, when there are a plurality of asperities within the measurement range, the presence of the asperity having the second and subsequent heights is AR. It should be noted that the value is not reflected. Further, the reciprocal of the AR value, 1 / AR = Ra / Rz, can be used as an index representing the height uniformity of the protrusions.
[0043]
If h2 is limited to a specific protrusion, the variation becomes large depending on the measurement method and the measurement location and does not serve as an index. Therefore, Rz is introduced. There are often one or more asperities with different heights in the measurement surface, and focusing on only one asperity has the effect of variations in height depending on the measurement location, and the highest asperity height is achieved. When AR is calculated using this, the variation becomes large. Therefore, by introducing Rz, the average value of the asperities having the height from the highest asperity to the fifth is taken as the representative asperity height of the measurement surface. Thereby, it is possible to reduce variations in the AR value depending on the measurement method and measurement location.
[0044]
Further, if h2 is limited to only the highest protrusion in the measurement surface, the value of h2 / h1 is 10/3 = 3.3 even in the following cases 1) to 3) where the height and density of asperity are different. There is a disadvantage that it ends up.
[0045]
1) There is one 10 nm protrusion in the average protrusion of h1 = 3 nm.
2) There are seven 10 nm protrusions in the average protrusion of h1 = 3 nm.
3) In the average protrusion of h1 = 3 nm, there are one protrusion of 10 nm and three protrusions of 6 nm.
[0046]
Such a contradiction can be considerably reduced by introducing Rz.
The definition of Rz is expressed by the following formula within the measurement range.
Rz = average of the highest 5 points-average of the lowest 5 points
Therefore, if there is no deep pit that will be counted in the lowest five points in the measurement surface, or if the pit depth does not affect the numerical value, Rz is the fifth highest protrusion from the highest protrusion. It becomes an index that approximately represents the average value of the heights up to.
[0047]
In the present invention, the roughness including asperity is measured by measuring the substrate surface by the tapping mode AFM. The roughness including the asperity is defined in a range where the measurement region is vertical and horizontal 5 μm to vertical and horizontal 20 μm. The average surface roughness Ra and the ten-point average surface roughness Rz used when calculating the AR value and the 1 / AR value are the center line average roughness Ra and the ten-point average roughness Rz defined in JIS B0601. It is expanded to three dimensions so that it can be applied to the measurement surface, and is defined as the following equation (1).
[0048]
[Expression 1]

However,
[0049]
[Expression 2]

Here, n represents the number of AFM data points, and Zi represents the data value of the i-th AFM.
[0050]
In addition, the number of data points in the measurement area at this time is defined as 65536 points (256 points per length of the vertical or horizontal side) or more.
The glass substrate for a magnetic disk according to the present invention has an Ra of 0.4 to 3.0 nm and an AR of 14 or less. This glass substrate is not only a CSS method, but also a ramp-load method in which the magnetic head is stored in a non-contact position when the magnetic disk is stopped, or a contact type magnetic recording in which the magnetic head is always in contact with the magnetic disk. It is suitable for use in equipment and can solve the problems of high density and adhesion at the same time.
[0051]
Next, the composition of the glass constituting the glass substrate material will be described.
As the substrate material, any of aluminosilicate glass, crystallized glass, soda lime glass, and the like is used. Of these, aluminosilicate glass having the following composition expressed in mol% is preferable. This is because this aluminosilicate glass can form fine irregularities having no asperity on the surface of the substrate material.
[0052]
Silicon oxide (SiO₂40-72%,
Aluminum oxide (Al₂O_Three) 0.5-25%,
Lithium oxide (Li₂O) 0-22%,
Sodium oxide (Na₂O) 0-14%,
Potassium oxide (K₂O) 0-10%,
R₂O 2-30%
However, R₂O = Li₂O + Na₂O + K₂O
Magnesium oxide (MgO) 0-25%,
Calcium oxide (CaO) 0-25%,
Strontium oxide (SrO) 0-10%,
Barium oxide (BaO) 0-10%,
RO 0-40%
However, RO = MgO + CaO + SrO + BaO
Titanium oxide (TiO₂0-10%
Zirconium oxide (ZrO₂0-10%
95% or more of the above ingredients
Glass having such a composition can be produced by a float process, has a low melting temperature, good water resistance and weather resistance after chemical strengthening treatment, and has an expansion coefficient that can be used in combination with metal products. The float method is a method for producing a plate-like glass by containing molten tin and flowing molten glass from one end into a high-temperature bath in which the upper space is a reducing atmosphere and stretching the glass from the other end. According to this float method, the obtained glass is parallel to both sides, is not distorted, has a surface gloss, can be mass-produced, can easily change the plate width, and can be easily automated.
[0053]
In the glass composition as described above, SiO₂Is a major component of glass and an essential component. When the content is less than 40% by weight, the water resistance after ion exchange for the strengthening treatment is deteriorated, and when it exceeds 72% by weight, the viscosity of the glass melt becomes too high, and melting and molding become difficult. At the same time, the expansion coefficient becomes too small.
[0054]
Al₂O_ThreeIs a component necessary for increasing the ion exchange rate and improving the water resistance after ion exchange. When the content is less than 0.5% by weight, such an effect is insufficient. When the content exceeds 25% by weight, the viscosity of the glass melt becomes too high, and it becomes difficult to melt and mold and expand. The coefficient is too small.
[0055]
Li₂O is an essential component for performing ion exchange and is a component that enhances solubility. If the content exceeds 22% by weight, the water resistance after ion exchange deteriorates, the liquidus temperature rises, and molding becomes difficult.
[0056]
Na₂O is a component that enhances solubility. When the content exceeds 14% by weight, the water resistance after ion exchange deteriorates. K₂O is a component that enhances solubility, and when the content exceeds 10% by weight, the surface compressive stress after ion exchange decreases.
[0057]
Furthermore, the above Li₂O, Na₂O and K₂O total R₂If O is less than 2% by weight, the viscosity of the glass melt becomes too high, making melting and molding difficult, and the expansion coefficient becomes too small. If it exceeds 30% by weight, the water resistance after ion exchange deteriorates. To do.
[0058]
MgO is a component that enhances solubility, and when it exceeds 25% by weight, the liquidus temperature rises and molding becomes difficult. CaO is a component that enhances solubility and is an essential component for adjusting the ion exchange rate. If the content exceeds 25% by weight, the liquidus temperature rises and molding becomes difficult. SrO is a component that increases solubility and is an effective component for lowering the liquidus temperature. When the content exceeds 10% by weight, the density of the glass increases and the production cost increases. BaO is a component that increases solubility and is an effective component for lowering the liquidus temperature. When the content exceeds 10% by weight, the density of the glass increases and the production cost increases.
[0059]
Furthermore, when the total RO of MgO, CaO, SrO and BaO exceeds 40% by weight, the liquidus temperature rises and molding becomes difficult.
TiO₂When the content exceeds 10% by weight, the quality of the glass substrate deteriorates and the production cost increases. ZrO₂When the content exceeds 10% by weight, the melting temperature or viscosity of the glass substrate increases, and the production of the glass substrate material tends to be difficult.
[0060]
In order to maintain the strength required for the magnetic disk substrate, the glass is preferably subjected to a chemical strengthening treatment on the surface thereof. In this chemical strengthening treatment, the glass is immersed in a molten salt containing a monovalent metal ion having an ionic radius larger than that of the monovalent metal ion contained in the composition, and the metal ion in the glass and the metal in the molten salt This is performed by ion exchange with ions.
[0061]
For example, by immersing a glass substrate in a heated potassium nitrate solution, sodium ions in the vicinity of the glass substrate surface are replaced with potassium ions having a larger ionic radius, and as a result, compressive stress acts to Strengthened. Further, the glass substrate may be immersed in a mixed solution of silver nitrate (0.5 to 3%) and potassium nitrate (97 to 99.5%) for 30 minutes to 1 hour. Thereby, silver ions are rapidly penetrated into the glass substrate surface, and the strengthening of the glass substrate surface is promoted. Moreover, it can replace with the mixed solution of silver nitrate and potassium nitrate, and can use the mixed solution of potassium nitrate and sodium nitrate.
[0062]
As described above, according to this embodiment, the following effects are exhibited.
According to the glass substrate for a magnetic disk of the embodiment, a glass substrate having fine irregularities not including asperity can be easily obtained by scrub etching the magnetic recording surface of the substrate material. For this reason, a glide hit of the magnetic head can be prevented, and damage to the magnetic head can be prevented.
[0063]
-According to the glass substrate for magnetic discs of the embodiment, by using the aluminosilicate glass having the specific composition described above as the substrate material, it is possible to easily and reliably form fine irregularities without asperity.
[0064]
-According to the glass substrate for magnetic disk of the embodiment, since the aluminosilicate glass has a low melting temperature and excellent formability, the glass substrate material can be easily manufactured by the float process. High quality with flatness.
[0065]
According to the method for manufacturing a glass substrate for a magnetic disk of the embodiment, the surface of the substrate material has asperity by scrub etching the magnetic recording surface of the substrate material with a pad as a friction body in the presence of an acidic treatment agent. A substrate having fine unevenness so that it does not exist can be easily obtained with improved yield.
[0066]
According to the method for manufacturing a glass substrate for a magnetic disk of the embodiment, by using at least one acid selected from hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, and hexafluorosilicic acid as an acidic treatment agent, glass Because of its high corrosiveness to scrubbing, scrub etching can be performed effectively.
[0067]
According to the method for manufacturing a glass substrate for a magnetic disk of the embodiment, the pad has a hardness smaller than that of the substrate material and has acid resistance against the acid treatment agent, so that the substrate material is not damaged and the acid treatment agent is used. Fine irregularities can be formed without being damaged.
[0068]
-According to the method for manufacturing a glass substrate for a magnetic disk of the embodiment, scrub etching is performed under conditions where the concentration of the acidic treatment agent is 0.01 to 1% by weight, the temperature is 5 to 60 ° C, and the treatment time is 1 to 300 seconds. Done in For this reason, the fine unevenness | corrugation which does not contain an asperity on appropriate conditions can be formed efficiently.
[0069]
【Example】
Next, the embodiment will be described more specifically with reference to examples and comparative examples.
Example 1
The surface of the substrate material made of aluminosilicate glass having the following composition (mol%) was scrub etched.
[0070]
SiO₂  66%, Al₂O_Three  10% Li₂O 7%, Na₂O 10%, MgO 3%, CaO 4%.
The surface of the chemically strengthened aluminosilicate glass substrate material having a diameter of 2.5 inches was precisely polished and then scrubbed with pure water. Next, the film was dipped for 1.5 minutes while being scrubbed and etched in a 0.1 wt% concentration hydrofluoric acid aqueous solution (35 ° C.), and further dipped for 2.5 minutes in a pH 12 potassium hydroxide solution and then pulled. Thereafter, scrub cleaning was again performed using pure water.
[0071]
Scrub etching was performed as follows. As shown in FIGS. 1 and 2, the pad 11 is formed in a disk shape larger than the glass substrate material 12, and twelve scrub ridges 13 extending obliquely radially are provided on both upper and lower surfaces thereof. The ridge 13 allows the aqueous hydrofluoric acid solution to be well stirred, and the fresh aqueous hydrofluoric acid aqueous solution is easily supplied to the substrate material 12. The pad 11 is made of a sponge made of polyvinyl alcohol [porous body, trade name Berklin, manufactured by Kanebo Co., Ltd.]. As shown in FIG. 4B, the substrate material 12 and the pad 11 are rotationally driven in opposite directions by motors so that the scrub protrusion 13 of the pad 11 is in sliding contact with the magnetic recording surface 12a of the substrate material 12, respectively. As a result, the magnetic recording surface 12a of the substrate material 12 is periodically scrubbed at regular intervals on the surface of the scrubbing protrusion 13 of the pad 11. The rotation speed of the pad 11 is 100 rpm. The substrate material 12 is immersed in the hydrofluoric acid aqueous solution, and at the same time the pad 11 is brought into contact, and scrubbing is continued until the pad 11 is pulled up.
[0072]
After this operation, the area of 10 μm in length and width of the magnetic recording surface 12a was measured by AMF. The magnetic recording surface 12a was isotropic and did not have a substantially flat portion between the concave or convex portions. A minute unevenness having a continuous shape was formed. The three-dimensionally defined average surface roughness (Ra) of the fine irregularities was 1.0 nm, the amplitude was 10 nm, and the typical period was 0.3 μm. The asperity ratio (AR = Rz / Ra) was 10.
[0073]
Next, on the surface of the glass substrate obtained as described above, a titanium (Ti) -silicon (Si) seed layer (25 nm), a chromium (Cr) -molybdenum (Mo) underlayer (25 nm), sequentially by sputtering, A cobalt (Co) -nickel (Ni) -chromium (Cr) -tantalum (Ta) magnetic layer (20 nm) and a carbon (C) protective layer (10 nm) were formed. Thereafter, a perfluoropolyether-based lubricant was applied as a lubricant to form a lubricating layer (2 nm), thereby obtaining a magnetic disk.
[0074]
The average surface roughness (Ra) defined three-dimensionally on the surface of the lubricating layer in this magnetic disk was 1.0 nm, and the amplitude was 10 nm. That is, minute irregularities formed on the surface of the substrate remained as it was on the surface of the lubricating layer.
[0075]
The obtained magnetic disk was mounted on the spindle of a ramp load type hard disk device, rotated at 3600 rpm, and a seek operation was performed with the magnetic head with the AE sensor floating, and the output of the AE sensor was monitored. As a result, even when the seek operation was performed, the output of the AE sensor indicating that the magnetic head and the magnetic disk collided violently was not recognized, and there was no glide error of the magnetic head. Further, when a glide test was performed with the flying height set to 15 nm, no glide hit occurred. Furthermore, although the seek operation was repeated 100,000 times, no head crash occurred.
(Comparative Example 1)
The surface of the chemically strengthened 2.5-inch aluminosilicate glass substrate was precisely polished, and then scrubbed with pure water. Next, it was lifted after being immersed for 30 minutes while swinging in an aqueous hydrofluoric acid solution having a concentration of 0.005% by weight, and further pulled for 2.5 minutes after being immersed in a potassium hydroxide solution having a pH of 12.
[0076]
Thereafter, scrub cleaning was again performed using pure water. After this operation, a vertical and horizontal area of 10 μm on the surface of the glass substrate was measured by AMF. As a result, minute irregularities having a discrete number of asperities with a height of several nanometers to several tens of nanometers were formed on the surface. It was. The three-dimensionally defined average surface roughness (Ra) of the fine irregularities was 1.0 nm, but because of the presence of asperity, the amplitude and representative period could not be evaluated. The asperity ratio (AR = Rz / Ra) was 16.7.
[0077]
Next, on the surface of the glass substrate obtained as described above, a titanium (Ti) -silicon (Si) seed layer (25 nm), a chromium (Cr) -molybdenum (Mo) underlayer (25 nm), sequentially by sputtering, A cobalt (Co) -nickel (Ni) -chromium (Cr) -tantalum (Ta) magnetic layer (20 nm) and a carbon (C) protective layer (10 nm) were formed. Thereafter, a perfluoropolyether-based lubricant was applied as a lubricant to form a lubricating layer (2 nm), thereby obtaining a magnetic disk.
[0078]
The average surface roughness (Ra) defined three-dimensionally on the surface of the lubricating layer in this magnetic disk was 1.0 nm, and the Ra / Rz ratio was 0.06. That is, minute irregularities including asperities formed on the substrate surface remained as it was on the surface of the lubricating layer.
[0079]
The obtained magnetic disk was mounted on the spindle of a ramp load type hard disk device, rotated at 3600 rpm, and a seek operation was performed with the magnetic head with the AE sensor floating, and the output of the AE sensor was monitored. As a result, a large number of outputs from the AE sensor indicating that the magnetic head and the magnetic disk collided violently when the seek operation was performed. Further, when the seek operation was repeated 100,000 times, a head crash occurred midway.
(Example 2)
In Example 1, the glass substrate in the hydrofluoric acid solution was scrubbed for 20 minutes. The other operations were the same as in Example 1.
[0080]
As a result, the average surface roughness (Ra) of the glass substrate was 1.5 nm, and the asperity ratio (AR = Rz / Ra) was 10. Further, as in Example 1, the magnetic head was not damaged or glide error occurred. Furthermore, although the seek operation was repeated 100,000 times, no head crash occurred.
[0081]
The embodiment may be embodied by changing as follows.
-You may provide the said fine unevenness | corrugation only in the CSS zone of a glass substrate.
When configured in this way, the portion other than the CSS zone can be kept in a mirror surface, so that when the magnetic disk medium is used, the magnetic head can be lowered and the recording density of the magnetic disk device can be increased. Can be achieved.
[0082]
The scrub protrusion 13 provided on the pad 11 of the above embodiment may be provided only on the magnetic recording surface 12a (only one side) of the pad 11.
When configured in this manner, the configuration of the scrub protrusion 13 can be simplified and easily formed.
[0083]
The pad 11 having the columnar shape may be formed in a taper shape or a cylindrical shape.
The cross-sectional shape of the scrub protrusion 13 may be a semicircular shape, a triangular shape, or the like.
[0084]
  The technical idea grasped from the embodiment is described below..
[0085]
  ・  The acidic treatment agent is mixed with at least one additive of a chelating agent and a surfactant.3The manufacturing method of the glass substrate for magnetic discs as described in any one of.
[0086]
  When configured in this manner, the scrub etching performance for the substrate material can be improved..
[0087]
  ・  The scrub etching is performed by rotating or rotating and revolving a pad.1Claims from4The manufacturing method of the glass substrate for magnetic discs as described in any one of these.
[0088]
  According to this method, scrub etching on the magnetic recording surface of the glass substrate material can be easily and effectively performed.
  The scrub etching is performed by rocking while rotating the pad.1Claims from4The manufacturing method of the glass substrate for magnetic discs as described in any one of these.
[0089]
According to this method, scrub etching on the magnetic recording surface of the glass substrate material can be easily and effectively performed.
[0090]
【The invention's effect】
  Since this invention is comprised as mentioned above, there exist the following effects.
  A glass substrate for a magnetic disk according to claim 1Manufacturing methodAccording to the above, it is possible to form fine irregularities so that there is no asperity on the substrate surface, prevent glide hit of the magnetic head and prevent damage to the magnetic headEasily obtain a glass substrate for magnetic disk with improved yieldbe able to.
[0091]
  According to the method for manufacturing a glass substrate for a magnetic disk of the invention according to claim 2,In addition to the effect of the invention according to claim 1, by using at least one acid selected from hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid and hexafluorosilicic acid as an acidic treatment agent, the corrosiveness to glass can be obtained. Since it is large, scrub etching can be performed effectively.
[0092]
  According to the method for manufacturing a glass substrate for a magnetic disk of the invention according to claim 3,In addition to the effects of the invention described in claim 1 or claim 2, the pad has a hardness lower than that of the substrate material and has acid resistance against the acid treatment agent, so that the substrate material is not damaged and the acid treatment agent is used. Fine irregularities can be formed without being damaged.
[0093]
  According to the method for manufacturing a glass substrate for a magnetic disk of the invention according to claim 4,In addition to the effects of the invention according to any one of claims 1 to 3, scrub etching has an acid treatment agent concentration of 0.01 to 1% by weight, a temperature of 5 to 60 ° C., and a treatment time of 1 to 300 seconds. Performed under the conditions of For this reason, the fine unevenness | corrugation which does not contain an asperity on appropriate conditions can be formed efficiently.
[Brief description of the drawings]
FIG. 1 is a plan view showing a state of scrub etching in an embodiment.
FIG. 2 is a cross-sectional view taken along line 2-2 in FIG.
3A is a perspective view showing a cylindrical pad for scrub etching, FIG. 3B is a plan view showing a state in which scrub etching is performed by rotating the pad, and FIG. 3C is a view from the state of FIG. 3B. Furthermore, the top view which shows the state rock | fluctuated in the radial direction of glass substrate material.
4A is a perspective view showing a disc-shaped pad for scrub etching, FIG. 4B is a plan view showing a state of scrub etching by rotating the pad, and FIG. 4C is a state of FIG. 4B. The top view which shows the state which rocks | fluctuates further in the radial direction of glass substrate material from FIG. 2, (d) is a top view which shows the state which revolves around the glass substrate material further from the state of (c).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Pad as friction body, 12 ... Glass substrate material, 12a ... Magnetic recording surface.

Claims (4)

After the surface of the chemically strengthened aluminosilicate glass substrate material is precisely polished, the magnetic recording surface of the glass substrate material is formed in a disk shape larger than the glass substrate material as a friction body in the presence of an acidic treatment agent. A glass substrate for a magnetic disk in which fine irregularities are formed so that asperity does not occur on the magnetic recording surface of the glass substrate material by scrub etching with a pad provided with scrub protrusions extending radially on both surfaces thereof Manufacturing method. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the acidic treatment agent is at least one acid selected from hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, and hexafluorosilicic acid. 3. The method of manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the pad has a hardness lower than that of the glass substrate material and has acid resistance against an acidic treatment agent. The scrub etching is performed under conditions where the concentration of the acidic treatment agent is 0.01 to 1 wt%, the temperature is 5 to 60 ° C, and the treatment time is 1 to 300 seconds. The manufacturing method of the glass substrate for magnetic discs as described in any one.

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