JP4318835B2 - Magnetic recording medium and magnetic recording / reproducing apparatus - Google Patents

Description

【００２６】
また、レーザ光の波長としては、２００〜１１００ｎｍが好ましい。２００ｎｍ未満であると、オゾンの発生が懸念され、この発生を防ぐために、非酸素中突起状構造体１０を形成しなければならなくなり面倒となる。またレーザ光を発するレーザにはエキシマレーザなどの繰り返し性、安定性に劣るものが多く、形成される突起高さが不均一となり易く、さらにはコスト高となって好ましくない。また、波長が１１００ｎｍを越えると、金属への吸収が落ちるので、成膜層５上に、突起状構造体１０を形成することができなくなるので好ましくない。また、この範囲の波長のレーザは、ガラスに吸収され難いため、ガラス基板を基板１とする磁気記録媒体へのレーザ照射を行う場合には、特に適しているといえる。逆に、ガラスは、例えば、ＣＯ₂レーザの波長１０.６μｍのレーザに対しては、金属よりも吸収し易いため、パーティクルの発生が起こることもあるので、このような波長は適さない。
【００２７】
また、このようなレザー光を照射して磁気記録媒体６上に、突起状構造体１０を複数形成し、これらが識別記号、文字等のマーキングを構成するようにするには、磁気記録媒体６を回転させながら、パルスレーザ光を磁気記録媒体６の回転のＺ相信号に同期をとって照射することが好ましい。
このとき、磁気記録媒体６を回転させながら、磁気記録媒体６あるいは集光レンズのどちらかが、磁気記録媒体６の半径方向に移動することによって文字の印字を行うことが好ましい。磁気記録媒体６の回転方向だけでは一次元の移動であるので、磁気記録媒体６あるいは集光レンズのどちらかが、磁気記録媒体６の半径方向に移動することによって２次元の移動が可能になり、文字等の印字を行うことができる。
また、このときに用いる集光レンズとしては、凸レンズ、アクロマッティクレンズ、顕微鏡用対物レンズ等のいずれのものを使用してもかまわない。ただし、焦点距離が小さすぎると焦点深度がとれないので、好ましくなく、焦点距離が大きすぎると連続発振レーザでは加工できなくなるので、焦点範囲としては１０〜８０μｍが好ましい。
【００２８】
磁気記録媒体６を回転させる方法としては、モータなどを用いるのが好ましい。このモータとしては、ＤＣ（サーボ）モータ、ＡＣ（サーボ）モータ、ステッピングモータ等が挙げられる。このようなモータとしては、Ｚ相信号の出力が可能なものが好ましい。Ｚ相信号とは、回転軸１回転に対して１パルスの出力信号を出すものであり、この場合、レーザ照射位置の位置決めの原点用として用いることができる。また、位置決めの原点の役割を有する信号であれば、Ｚ信号の代わりとして使用することもできる。例えば、１回転あたり１０２４パルスが出力信号が出されるＡ相信号であれば、出力信号を１０２４回カウントすることにより原点信号として使用可能である。
【００２９】
次に、アルファベットのＡをマーキングとして磁気記録媒体上に印字する場合を例に挙げて本発明の磁気記録媒体の製造方法について説明する。
まず、文字情報を図３に示すように、ドットパターンとして表す。この場合は、アルファベットのＡを１０×１０のドットとして表した。
ついで、このドットパターンをデジタル信号に変換する。例えば、図４に示すように、図３におけるＡのドットパターンの黒部を１、白部を０として表す。
ついで、上記変換されたデジタル信号の一行をまとまった信号として、データゼネレータ等のパルス発信器に入力する。この場合、Ａを１０×１０のドットで表現しているので、１行が１０ビットのデジタル信号とされ、例えば、一行目００００１１００００、２行目が００００１１００００、３行目が０００１１１１０００というように、各行のデジタル信号がパルス発信器に入力される。
ついで、前記パルス発信器にシーケンスを作製し、１回トリガー信号が入力されると、１回につき一行のデジタル信号が出力されるようにする。さらに、１回トリガー信号が入力されると、次の行のデジタル信号が１回出力されるようにする。このプロセスは、文字等の情報が完結するまで繰り返される。例えば、この場合には、１０行目が終わるまで繰り返されることとなる。
このときのトリガー信号には、Ｚ相信号を用い、磁気記録媒体を回転させながら、集光レンズが一軸方向に移動するようにしてマーキングを行う。このとき、マーキング加工時のパルス幅は、上述の突起状構造物を作製するのに適した範囲とする。
【００３０】
このようにして、磁気記録媒体の一回転の原点位置に、上記デジタル信号の一行分が印字されることとなる。この各行のデジタル信号ごとに繰り返せば、文字等、この場合は、Ａを印字することができる。
このように、原点信号をトリガー信号に用いれば、原点位置と文字等の情報の一行分がほぼ同じ位置にくることになる。したがって、印字の行方向がずれるということがない。Ｚ相信号は磁気記録媒体が回転している間は、一回転に一回ずつ発生する。しかし、実際には、マーキングするのは、その間の一部の時間であるので、マーキングするだけのＺ相信号が発生するようにしなければならないが、これは、マーキングの間だけリレーがＯＮするようなシーケンサーにより容易に実現することができる。
仮に原点信号を用いずに、回転時間を推測してマーキングを施す方法であれば、回転のばらつきにより印字が行方向にずれてしまう。
【００３１】
一般的なレザーマーキング装置においては、文字等を直接表現するために、ガルバノミラーとｆθレンズを用いている。ガルバノミラーは、２枚のミラーで構成されており、２枚のミラーを制御することにより２次元の描写が可能になり、文字等を直接表現することができるものである。このガルバノミラーを用いると、レーザ光の集光レンズへの入射角度、入射位置は変化するため、通常用いられる集光レンズでは、同一表面上に焦点を結ぶことは困難である。この問題を解消するために用いられているのがｆθレンズであり、ｆθレンズの焦点距離を大きくすることによって、レーザ光の集光レンズへの入射角度、入射位置が変化しても、同一表面上に焦点を結ぶことを可能としている。
例えば、Ｙｆθレンズ（シグマ光機社製）では、焦点距離が３００、１５０、１００ｍｍと小さくなるにしたがい、走査距離がφ２４０、１２０、６０ｍｍと短くなってしまう。
【００３２】
このように、従来のレーザーマーキング装置において、連続発振レーザ光を外部変調装置を用いてパルス化して用いる場合には、そのピークパワーが小さいために、焦点距離の長いレンズを用いることができなかった。
しかしながら、上述の磁気記録媒体を回転させ、レーザ光を磁気記録媒体の回転のＺ相信号に同期をとってパルス発振させる方法であれば、このようなレーザ光を外部変調装置を用いてパルス化して用いる場合であっても、焦点距離の短い通常の集光レンズを用いても、正確に記号や文字等を印字することができる。
一般に、レーザテクスチャ法としては、パルスレーザ光が用いられている。
よって、例えば、レーザテクスチャ法に用いられるレーザ法をそのままレーザマーキングに用いることが可能となる。
このようにすれば、容易に上記マーキングを磁気記録媒体６に形成することができる。
【００３３】
このようなレーザ光を用いて磁気記録場板６表面上に突起状構造体１０を形成してマーキングをする磁気記録媒体の製造方法によれば、レーザ光の波長、パルス幅が最適のものに設定されているので、突起状構造体１０の凸部１１の高さ、凹部１２の深さ、形成位置等の設定を精度よく行うことができる。また、基本的にこの形成方法は乾式過程であるため、磁気記録媒体６への不純物の混入等を防ぐことができる。
また、このような磁気記録媒体６の製造方法においては、磁気記録媒体６を回転させ、レーザ光を磁気記録媒体６の回転のＺ相信号に同期をとってパルスレーザ光を照射することによって複数の突起状構造体１０を形成するものであるので、容易にかつ正確に、記号や文字などを示すマーキング７を、磁気記録媒体６上に形成することができる。
【００３４】
また、このような成膜後の磁気記録媒体６にマーキングを施す方法は、例えば、片面のみ記録面として使用可能な磁気記録媒体６で、その表面に、記録面と非記録面とを識別するために用いることができる。
通常の磁気記録媒体６には、記録容量を向上させるために、その両面に記録面が形成されている。しかし、製造後の磁気記録媒体６の中には、その片面が記録面として不良であるものが含まれている。この不良面をここでは非記録面としている。
上記磁気記録媒体６における記録面（正常面）と非記録面（不良面）とは、磁気記録媒体６製造後に行われる表面検査や、電磁変換特性検査等の試験によりその記録面の特性を調べることにより初めてわかるものである。よって、これら記録面と非記録面との識別のためのマーキングは、これらの検査の後、すなわち磁気記録媒体６製造後（磁性膜の成膜後）に行わなければならないものであり、本発明におけるマーキングの形成方法が好適に用いられる。
【００３５】
このような記録面と非記録面とを有する磁気記録媒体６に形成されるマーキング７は、磁気記録媒体の記録面、非記録面のどちらに形成しても構わない。
非記録面にマーキング７を形成する場合であれば、磁気記録媒体６の記録面の特性を阻害することなく、磁気記録媒体６の非記録面の任意の位置に、突起状構造体１０を形成することができ、その識別が容易となる。
また、記録面にマーキング７を形成する場合のその形成位置としては、例えば、図１に示すような磁気記録媒体６における非記録領域１０１が好ましく、特に、この例のように、非記録領域１０１の最内周領域１０２に形成されることが望ましい。このようにすれば、マーキング７を記録面に形成する場合であっても、磁気記録媒体６の記録特性を低下させることがない。
【００３６】
ところで、従来、このような片面のみ記録面として使用可能な磁気記録媒体６は、不良品として破棄されていた。
ところが、最近では、このような片面だけ使用可能な磁気記録媒体６であっても、実用可能とされる場合がでてきた。というのは、従来は、ハードディスクドライブ（ＨＤＤ）には、磁気記録媒体１枚あたり、２個の磁気記録ヘッドが用いられてきたため、磁気記録媒体６の両面を記録面に用いることにより記録容量の向上が図られてきたという事情があったが、近年のＨＤＤの記録密度の向上は目覚ましく、通常のパーソナルコンピュータ（ＰＣ）の用途では、磁気記録媒体６の片面を用いるだけで、必要な記録容量を満たしてしまうことが多くなってきているためである。
【００３７】
このような事情から、従来、磁気記録媒体製造後の検査の段階で、片方の記録面が不良であるために用いられなかった磁気記録媒体６であっても、片面の記録面が正常であれば、磁気記録媒体６として十分に用いることができると考えられる。よって、従来不良品として破棄されていた片面だけが正常の磁気記録媒体６を有効に利用することができれば、大幅なコスト削減が実現できるものである。
このような片面のみ記録面として良好である磁気記録媒体６を用いる場合、正常の記録面と、そうでない非記録面とを区別して用いることが必要とされる。
【００３８】
よって、上記マーキングが施された磁気記録媒体６であれば、磁気記録媒体６の記録面と、非記録面との識別が目視により容易にできる。よって、このような片面のみ使用可能な磁気記録媒体６を実用化することができる。これにより、磁気記録媒体６の製造コストを大幅に減少させることができるとともに、この片面のみ使用可能の磁気記録媒体６を磁気記録装置に用いれば、磁気記録再生装置のコストを下げることができる。
【００３９】
なお、本発明はこのような用途に限定されるものではなく、様々な用途のマーキング７に使用することができる。例えば、両面使用の磁気記録媒体６の製造番号や日付などの識別等にも用いることができる。
また、本発明は、ＣＳＳゾーンのない磁気記録媒体におけるマーキングにも用いることができる。
【００４０】
図９は、本発明の磁気記録媒体のマーキング装置の一実施形態を示すもので、この装置は、レーザ光源２１と、レーザ光源２１から発せられたレーザ光を集光する集光レンズ２２と、マーキングを施すべき磁気記録媒体Ｄを保持する基板保持装置２３とを備えて概略構成されている。集光レンズ２２とは、凸レンズアクロマティックレンズ、顕微鏡用対物レンズ等のほかに、カライドスコープ等を用いることができる。
【００４１】
カライドスコープはレーザ光を、エネルギー密度が均一な平行光とするための光学装置であり、図１０に示すように、筒状のスコープ本体３０内に、入射光を多重反射させ平行化するカライドミラー３１と、カライドミラー３１からの出射光の方向を変える反射ミラー３２とを収容し、本体３０の外周に反射ミラー３２からの反射光の光路を整える集光用レンズ３３を設けて構成されたものである。このカライドスコープは、レーザ光のエネルギー密度を均一にすることができるので集光レンズ２２として用いるのに好ましい。
また、基板保持装置３３は、マーキング処理を施すべき磁気記録媒体Ｄを周方向に所定の回転速度で回転させることができるように構成されている。
本発明の磁気記録媒体のマーキング装置は、これらの装置に限らず、その他外部変調器、各種制御装置等を備えて構成することができる。
【００４２】
このような記録媒体のマーキング装置であれば、成膜後の磁気記録媒体６上に、上述の突起状構造体１０を複数容易に形成することができる。
【００４３】
図１１は、上記磁気記録媒体を用いた磁気記録再生装置の例を示すものである。ここに示す磁気記録再生装置は、磁気記録媒体６と、磁気記録媒体６を回転駆動させる媒体駆動部４１と、磁気記録媒体６に情報を記録再生する磁気ヘッド４２と、ヘッド駆動部４３と、記録再生信号処理系４４とを備えている。記録再生信号処理系４４は、外部からの記録信号を処理して磁気ヘッド４４に送ったり、磁気ヘッド４２からの再生信号を処理して外部に送ることができるようになっている。
このような磁気記録再生装置であれば、片面のみ使用可能な磁気記録媒体６であっても、その内部に備えて使用することができる。よって製造コストを低くすることができるので、安価とすることができる。
【００４４】
【実施例】
以下、本発明を実施例を示して詳しく説明する。
（実施例１）
リチウムシリケイトガラスからなるガラス基板１上に、Ｃｒ合金からなる下地層２、Ｃｏ合金からなる磁性膜３、カーボンからなる保護層４を順に成膜した磁気記録媒体６の非記録領域１０１に加工範囲を円周上に５００μｍとして、次に示す装置、方法により突起状構造体１０を複数形成した。このとき基板１上に形成された下地層２、磁性膜３、保護層４をあわせた成膜層５の膜圧は１００ｎｍであった。
レーザ光源として、ＭｉｌｌｅｎｎｉａＸ（連続発振、波長５３２ｎｍ、出力５Ｗ、スペクトラフィジックス社製）を用い、外部変調器ＥＯＭ ｍｏｄｅ１３７０−ＬＡ（Ｃｏｎｏｐｔｉｃｓ，ｉｎｃ製）を用いてレーザをパルス化し、集光レンズには、ＭＳＰｌａｎ×５（オリンパス社製）を用いた。
そして、この磁気記録媒体６を回転させながら上記レーザを、加工パルス周波数２００ｋＨｚ、レーザ出力２．５Ｗ、パルス幅５００ｎｓで照射した。このときの回転する磁気記録媒体６の集速を４ｍ/ｓ、ピッチを半径方向２０μｍとし、その加工範囲を円周上に１００μｍとした。
【００４５】
この結果、磁気記録媒体６の所定の位置に、凸部１１の高さが５０ｎｍである突起状構造体１０を複数形成することできた。その形状は良好であり、ガラス基板が露出した突起状構造体１０はなかった。
【００４６】
（実施例２）
磁気記録媒体６の基板１としてニッケル燐メッキを施したアルミ基板を用いた以外は実施例１と同様にして磁気記録媒体６上に凸部１１の高さが５０ｎｍである複数の突起状構造体１０を形成した。
この結果、磁気記録媒体６の所定の位置に、突起状構造体１０を容易に形成することできた。その形状は良好であり、アルミ基板のニッケル燐下地層が露出した突起状構造体１０はなかった。
【００４７】
（実施例３）
レーザ光源として、ＭｉｌｌｅｎｎｉａＶ（連続発振、波長５３２ｎｍ、出力５Ｗ、スペクトラフィジックス社製）を用い、レーザ出力を０．８Ｗとして、連続発振レーザを用いた以外は実施例１と同様にして、磁気記録媒体６上に凸部１１の高さが５０ｎｍである複数の突起状構造体１０を形成した。
この結果、磁気記録媒体６の所定の位置に、突起状構造体１０を容易に形成するこできた。その形状は良好であり、ガラス基板が露出した突起状構造体１０はなかった。
【００４８】
（実施例４）
レーザ光源としてＺＴ−１５（パルス発振、波長１０６４ｎｍ、出力２Ｗ、コヒーレント社製）を用い、加工パルス周波数を１５０ｋＨｚ、レーザ出力０．１５Ｗ、パルス幅１１０ｎｓとした以外は、実施例１と同様にして、凸部１１の高さが５０ｎｍである複数の突起状構造体１０を形成した。
この結果、磁気記録媒体６の所定の位置に、突起状構造体１０を容易に形成することできた。その形状は良好であり、ガラス基板が露出した突起状構造体１０はなかった。
【００４９】
（比較例１）
レーザ光のパルス幅を１５００ｎｓとした以外は、実施例１と同様にして、凸１１部の高さが２００ｎｍである複数の突起状構造体１０形成した。
しかしながら、形成した全ての突起状構造体１０において、ガラス基材が露出してしまった。
【００５０】
（比較例２）
レーザ光のパルス幅を１５００ｎｓとした以外は、実施例２と同様にして、凸１１部の高さが２００ｎｍである複数の突起状構造体１０形成した。
しかしながら、形成した全ての突起状構造体１０において、アルミ基材のニッケル燐メッキ部分が露出してしまった。
【００５１】
（比較例３）
レーザ光源として５０１ＱＭ−ＶＤ（パルス発振、波長１０６４ｎｍ、出力１．５Ｗ、コヒーレント社製）を用い、加工パルス周波数を１０ｋＨｚ、レーザ出力を０．０１Ｗ、パルス幅を１０ｎｓとした以外は、実施例１と同様にして、凸部１１の高さが５０ｎｍである突起状構造体１０を複数形成した。
この結果、形成された突起状構造体１０の３０％程度で、ガラス基板が露出してしまった。このとき、レーザ出力を可変しても、ガラス基板が露出していない突起状構造体１０を得ることはできなかった。
【００５２】
実施例１と比較例１の突起状構造体１０形成後の磁気記録媒体６にけるコロージョン性を評価した。コロージョン性の評価は、それぞれの磁気記録媒体６を温度８０℃の温水に６０分間浸して温水抽出し、この温水中のリチウムイオン量をＩＣＰ−ＭＳにより測定した。このとき、レーザ処理をしていない実施例１に用いた磁気記録媒体６と同様のものをリファレンスとし、同様の試験を行った。結果を表２に示す。
この結果から、比較例１の磁気記録媒体６から、実施例１およびリファレンスの磁気記録媒体６に比較して、多量のリチウムイオンが析出していることがわかった。
【００５３】
実施例２と比較例２の突起状構造体１０形成後の磁気記録媒体６にけるコロージョン性を評価した。コロージョン性の評価は、それぞれの磁気記録媒体６を温度８０℃、湿度８０％のオーブン中に１６８時間放置し、その後、温度２５℃の温水に６０分間浸して温水抽出し、この温水中のニッケルイオン量をＩＣＳ−ＭＳにより測定した。レーザ処理をしていない実施例２に用いた磁気記録媒体６と同様のものをリファレンスとし、同様の試験を行った。結果を表２に示す。この結果から比較例２の磁気記録媒体６から、実施例２およびリファレンスの磁気記録媒体６に比較して、多量のニッケルイオンが析出していることがわかった。
【００５４】
【表２】

【００５５】
（実施例５）
レーザには、ＭｉｌｌｅｎｉａＶ（スペクトラフィジックス社製、出力５Ｗ）レーザ出力２.５Ｗ、外部変調器としてＥＭＯ ｍｏｄｅ１３７０−ＬＡ（Ｃｏｎｏｐｔｉｃｓ．ｉｎｃ製）、集光レンズとして顕微鏡用対物レンズＭＳＰｌａｎ×５（オリンパス社製、焦点距離３６ｍｍ）モータとしてＡＣサーボモータ（新明和製）を用い、磁気記録媒体６として、上記実施例１に用いた磁気記録媒体６を用い、この磁気記録媒体６の加工周速を４ｍ/ｓで回転させながら、加工ピッチを半径方向２０μｍとし、円周方向の間隔を制御することによって、その表面に、突起状構造物１０と形成することにより、文字Ａを印字した。
そして、図３にあるように、文字Ａは、１０×１０ドットとして、このドットを白部を０、黒部を１としたデジタル信号に変換し、デジタル信号が１の時のみに、レーザがパルス発振して、突起状構造物１０が形成されるようにした。
そして、図４に示した文字Ａを変換したデジタル信号は行ごとに、データゼネレータＤＺ２０２０（ソニーテクトロニクス社製）に取り込み、トリガー信号が入力されたら、順番に１回ずつ対応するデジタル信号が発振されるようにした。また、上記データゼネレータのクロック周波数は、２ＭＨｓであったので、そのままデジタル信号を発信したのでは２μｍ間隔のドットとなってしまうので、、デジタル信号が０のときには００００００００００、１のときには１０００００００００のデジタル信号を割り当て、２０μｍドット間隔になるように調整した。このとき、レーザ光の１パルスあたりのパルス幅は５００ｎｓであった。トリガー信号には、ＡＣサーボメータのＺ相信号を用いた。
この結果、２００×２００μｍ角のＡという文字を行方向のずれなしできれいに作製することができた。また、このときの突起状構造体１０の凸部１１の高さｈ１は、５００ｎｍであった。
【００５６】
（比較例４）
レーザには、ＭｉｌｌｅｎｉａＺ（スペクトラフィジックス社製、出力１０Ｗ）
レーザ出力１０Ｗ、外部変調器としてＥＭＯ ｍｏｄｅ１３７０−ＬＡ（Ｃｏｎｏｐｔｉｃｓ．ｉｎｃ製）、集光レンズとしてＹｆθレンズ（シグマ光機社製、焦点距離１００ｍｍ）を用い、磁気記録媒体６に実施例１と同様のものを用い、この磁気記録媒体６を静止させ、ガルバノミラーを動かすことにより、上記Ａの印字を行った。
この結果、磁気記録媒体６上に突起状構造体１０を形成することができず、文字Ａを印字することができなかった。
【００５７】
【発明の効果】
以上説明したように本発明の磁気記録媒体は、基板上に少なくとも磁性膜が形成された磁気記録媒体であって、この記録媒体上に、目視により識別可能な複数の突起状構造体からなるマーキングが形成されているものであるので、磁気記録媒体における様々な識別を目視により容易に行うことができるものである。例えば、磁気記録媒体における記録面と非記録面とを有するものであれば、その識別を容易に行うことができる。また、このような磁気記録媒体であれば、従来不良品とされていた片面のみ良好な磁気記録媒体でも製品として用いることができ、大幅なコストダウンを計ることができる。
【００５８】
また、上記突起状構造体の凸部の高さが、１０ｎｍ以上、（基板上に形成された層の総合厚さ）×２ｎｍ以下であれば、目視可能でわかりやすく、また磁気記録媒体の耐コロージョン性の低下させることのなくマーキングを施された磁気記録媒体を得ることができる。
上記突起状構造体の凹部の深さが、１０ｎｍ以上、（基板上に形成された層の総合厚さ）ｎｍ以下であれば、同様に目視可能でわかりやすく、また磁気記録媒体の耐コロージョン性の低下させることのなくマーキングを施された磁気記録媒体を得ることができる。
さらに、上記基板上に形成された層の総合厚さが、１０〜３００ｎｍである磁気記録媒体であれば、容易に良好なマーキングを施すことができる。
上記マーキングが、目視により識別可能な記号または文字などであれば、より磁気記録媒体の識別が容易となる。
また、上記マーキングにより正常面（記録面）と不良面とを識別された磁気記録媒体によれば、これを用いることにより従来破棄されてきた片面のみ使用可能な磁気記録媒体を製品として用いることが可能となり、大幅なコスト削減が可能となる。また、この磁気記録媒体を磁気記録装置に用いれば、磁気記録装置の製造コストを下げることができる。
【００５９】
本発明の磁気記録媒体の製造方法によれば、パルス発振レザー光または、パルス化された連続発振レーザ光を、磁気記録媒体に照射することによって上記突起状構造体を形成するものであるので、成膜後の磁気記録媒体に、上記突起状構造体を複数形成して、目視により識別可能なマーキングを容易に形成することができる。詳しくは、凸部の高さが、１０ｎｍ以上、（基板上に形成された層の総合厚さ）×２ｎｍ以下であり、凹部の深さが、１０ｎｍ以上、（基板上に形成された層の総合厚さ）ｎｍ以下である突起状構造体を複数、容易に磁気記録媒体上に形成することができる。
また、この方法においては、レーザ光により突起状構造体を、磁気記録媒体上の正確な位置に形成することができるので、輪郭のはっきりとした正確な形状の記号や文字等のマーキングを磁気記録媒体の表面に形成することができる。
また、上記磁気記録媒体の製造方法において、レーザ光の波長が２００〜１１００ｎｍ、そのパルス幅を１００ｎｓ以上にすれば、上記凸部の高さまた、凹部の深さ等の制御がよういであり、これらの値にばらつきの少ない良好な形状の突起状構造体を得ることができる。
【００６０】
本発明の磁気記録媒体のマーキング装置によれば、上記形状の突起状構造体を容易に形成することができ、上記磁気記録媒体を容易に製造することができる。また、本発明の磁気記録再生装置においては、正常記録面と不良記録面とを有し、従来破棄されてきた磁気記録媒体であっても用いることができるので、製造コストが低く、安価とすることができる。
【図面の簡単な説明】
【図１】 本発明の磁気記録媒体の一例を示す平面図である。
【図２】 （ａ）本発明の磁気記録媒体に形成される突起状構造体の一例を示した平面図である。
（ｂ）（ａ）におけるＡ−Ａ’方向からみた断面図である。
【図３】 本発明の磁気記録媒体に形成されるマーキングの一例をドットパターンとして示した図である。
【図４】 図３におけるマーキングのドットパターンをデジタル信号として表した図である。
【図５】 本発明の磁気記録媒体に形成される突起状構造体の一例における凸部の高さｈ１と、レザーパワーの関係を示したグラフである。
【図６】 本発明の磁気記録媒体に形成される突起状構造体の一例における凹部に深さｈ２と、レザーパワーの関係を示したグラフである。
【図７】 本発明の磁気記録媒体に形成される突起状構造体を形成する際のレーザ光のパルス幅と、レーザパワーの関係を示したグラフである。
【図８】 磁気記録媒体の一例の構造を示すための断面図である。
【図９】 本発明の磁気記録媒体のマーキング装置の一例を示す概略構成図である。
【図１０】 本発明の磁気記録媒体のマーキング装置に用いられるカライドスコープの一例を示す概略構成図である。
【図１１】 本発明の磁気記録再生装置の一例を示す概略構成図である。
【符号の説明】
１…基板、 ２…下地膜、 ３…磁性膜、 ４…保護膜、 ５…成膜層
６…磁気記録媒体、 ７…マーキング
１０…突起状構造体、１１…凸部、１２…凹部[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a magnetic recording medium used for a magnetic disk device or the like.,andMore specifically, the magnetic recording medium is provided with markings that can be visually identified.When,The present invention relates to a magnetic recording / reproducing apparatus having the magnetic recording medium.
[0002]
[Prior art]
As a magnetic recording medium used for a hard disk drive (HDD), for example, a nonmagnetic underlayer 2, a magnetic film 3, a protective film 4 and the like are provided on a substrate 1 such as an aluminum substrate or a glass substrate as shown in FIG. Those formed in order are known.
Conventionally, such a magnetic recording medium 6 is sometimes marked on the surface in order to facilitate identification between each other for manufacturing management. Such marking is performed by forming markings such as numbers and letters on a magnetic recording medium by means of laser irradiation, ink jetting, ruled writing, or the like. According to these methods, it is possible to easily form the marking for identification on the magnetic recording medium using a commercially available laser device. For example, in a method using a YAG laser or the like, it could be easily formed using a laser marker such as a commercially available LE-100S (manufactured by Laser Technology) or MY-9500 (manufactured by Keyence).
[0003]
[Problems to be solved by the invention]
However, the marking process on the magnetic recording medium 6 by such a method is usually formed on the substrate 1 or the nonmagnetic underlayer 2 of the magnetic recording medium 6, and the magnetic film 3 and the like in the manufacturing stage. However, it was not performed on the film formation surface after the magnetic recording medium 6 was manufactured after the film formation, that is, after the magnetic film 3 or the like was formed.
Therefore, when marking is performed on the surface of the magnetic recording medium 6 after the magnetic recording medium 6 is manufactured, it is good to use the processing method conditions for marking on the substrate 1 or the nonmagnetic underlayer 2 as they are. Cannot be marked.
The present invention has been made in view of the above circumstances, and an object thereof is to obtain a method capable of easily and accurately marking a magnetic recording medium after forming each layer on a substrate, that is, after manufacture. To do.
[0004]
[Means for Solving the Problems]
  The magnetic recording medium of the present invention is a magnetic recording medium in which at least a magnetic film is formed on a substrate, and a visually identifiable marking is formed on the recording medium, and the marking has a plurality of protruding structures. KaraIn addition, the magnetic recording medium has a normal surface and a defective surface, and the normal and defective surfaces can be distinguished by the marking.It is characterized by that.
  In the magnetic recording medium of the present invention, it is desirable that the height of the protrusions of the protruding structure is 10 nm or more and (total thickness of layers formed on the substrate) × 2 nm or less.
  In the magnetic recording medium of the present invention, it is desirable that the depth of the concave portion of the projecting structure is 10 nm or more and (the total thickness of the layers formed on the substrate) nm or less.
  In the magnetic recording medium of the present invention, it is desirable that the total thickness of the layers formed on the substrate is 10 to 300 nm.
  In the magnetic recording medium of the present invention, it is desirable that the marking is a symbol or character that can be visually identified..
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the magnetic recording medium of the present invention will be described.
FIG. 1 shows an example of the magnetic recording medium of the present invention.
This magnetic recording medium 6 has a circular disk shape, and has a film-forming layer having at least a magnetic film formed on both surfaces of a substrate. As shown in the figure, the surface of the magnetic recording medium 6 is composed of a recording area 100 that is a recording / reproducing area and a non-recording area 101 that is not related to recording on the inner periphery thereof. The recording area 101 further includes an innermost peripheral area 102 and a CSS zone 103 which is a contact area with the magnetic head. A marking 7 that can be visually recognized is formed on the innermost peripheral portion 102 of the magnetic recording medium 6. In this example, a CSS zone 103 is provided in the magnetic recording medium 6. The magnetic recording medium 6 may be one in which a CSS zone is not formed like that used in a ramp load type magnetic recording / reproducing apparatus.
[0008]
Such a magnetic recording medium 6 includes, for example, a nonmagnetic underlayer 2 made of Cr, Cr / Ti alloy, etc., a Co / Cr alloy on a substrate 1 made of an aluminum substrate or a glass substrate as shown in FIG. , A magnetic layer 3 made of Co / Cr / Ta alloy or the like and a protective layer 4 made of carbon or the like are formed by a technique such as sputtering, vacuum deposition, ion plating, or plating. Such layers formed on the substrate 1 are collectively referred to as a film formation layer 5. In this example, the film-forming layer 5 is composed of the underlayer 2, the magnetic layer 3, and the protective layer 4, but a lubricating layer made of perfluoropolyether (PFPE) or the like is provided on the protective layer 4. In some cases, a NiP alloy film formed by plating, sputtering, or the like is provided between the substrate 1 and the nonmagnetic underlayer 2, and at least the magnetic film 3 is formed as the film formation layer 5. If it is what is done.
[0009]
The thickness of the film-forming layer 5 is related to the configuration of the underlayer 2, the magnetic film 3, the protective layer 4, and the like, and the thickness thereof, but the total thickness is usually 10 to 300 nm. If the thickness is less than 10 nm, the magnetic film 3 becomes too thin and its magnetization becomes weak, making it difficult to use as the magnetic recording medium 6. When the magnetic recording medium 6 is made rough, the head may come into contact with the magnetic recording medium 6 to cause a head crash.
[0010]
The marking 7 formed on the magnetic recording medium 6 is identifiable by visual observation, and desirably represents a symbol, character, figure, or the like. In this example, the letter A is used. As described above, if the marking 7 indicates a symbol or a character, it can be immediately confirmed by visual observation. For example, the front and back of the magnetic recording medium 6 can be easily identified by the marking 7.
Such a marking 7 is formed from a plurality of protruding structures formed on the surface of the magnetic recording medium 6. 2 is a schematic cross-sectional view showing an example of a protruding structure formed on the magnetic recording medium of the present invention, FIG. 2- (a) is a plan view, and FIG. 2- (b) is ( It is AA 'sectional drawing in a).
[0011]
A plurality of the protruding structures 10 are provided on the magnetic recording medium 6 on which the film forming layer 5 having at least a magnetic film is formed on the substrate 1, and rises from the surface of the film forming layer 5 of the magnetic recording medium 6. It is formed in a crater shape by the formed annular convex portion 11 and the concave portion 12 formed by digging down from the surface of the film forming layer 5 and surrounded by the convex portion.
The size of the projecting structure 10 is not particularly limited. However, as shown in FIG. 2, in the annular projecting structure 10, the other side from the apex of the convex portion on the straight line passing through the center of the projecting structure 10. When the distance (L1) to the apex of the convex portion is defined and expressed as the diameter of the protruding structure 10, the diameter (distance L1) is 0.1 to 30 μm, preferably 1 to 30 μm, more preferably Is in the range of 8-30 μm.
Further, the height of the convex portion 11 of the projecting structure 10, that is, the height h1 from the surface of the film formation layer 5 is preferably in the range of 10 nm or more (the thickness of the film formation layer 5) × 2 nm or less. . If the height h1 of the convex portion 11 is less than 10 nm, it is difficult to visually identify the marking 7 composed of the plurality of protruding structures 10, and it is difficult to identify the marking 7 using an optical method. End up. On the other hand, if the height h1 exceeds twice the thickness of the film formation layer 5, the magnetic head may be unstable when the magnetic recording medium 6 is driven.
[0012]
The depth of the concave portion 12 of the protruding structure 10, that is, the depth h2 from the surface of the film formation layer 5 is preferably in the range of 10 nm or more (thickness of the film formation layer 5) nm or less. When the depth h2 of the recess 12 is less than 10 nm, it is difficult to visually identify the marking composed of the plurality of protruding structures 10, and it is difficult to identify the marking using an optical method. End up. Further, when the depth h2 becomes larger than the thickness of the film formation layer 5 formed on the substrate 1, the substrate 1 is exposed.
[0013]
When the surface of the substrate 1 is exposed, the following problems occur. In general, as the substrate 1 used for the magnetic recording medium 6, an aluminum substrate, a glass substrate, or the like is used as described above. When these substrates 1 are exposed from the magnetic recording medium 6, various cations are precipitated from the surface. For example, if the surface is an aluminum substrate plated with nickel phosphorous, nickel ions will precipitate, and if it is a glass substrate, lithium ions, potassium ions, sodium ions, etc. will precipitate. If such ions are present, the deterioration of the corrosion resistance of the magnetic recording medium 6 is promoted, and the reliability of the magnetic recording medium cannot be maintained.
Therefore, it is preferable to form the protruding structure 10 so that the surface of the substrate 1 is not exposed.
Moreover, it is preferable that the space | interval of each protruding structure 10 is 10-50 micrometers. If the thickness is less than 10 μm, the protruding structures 10 may overlap each other due to the vibration of the apparatus or the spindle, and if the thickness exceeds 50 μm, the density of the protruding structures 10 becomes coarse and is visually identified. It becomes difficult to do.
As the size L2 of the marking 7 formed by such a plurality of protruding structures 10, it is difficult to visually identify if it is too small, and if it is too large, it takes time to form. It is preferable to be about 2 mm.
[0014]
Next, an embodiment of the method for manufacturing a magnetic recording medium of the present invention will be described by taking the case of manufacturing the magnetic recording medium 6 as an example.
The magnetic recording medium 6 can be obtained by irradiating a laser beam on the surface thereof to form a plurality of protruding structures 10 and thereby providing markings 7 that can be visually identified.
[0015]
As the laser light, it is desirable to use pulsed laser light or pulsed laser light obtained by pulsing continuous wave laser light.
Typical examples of these laser light irradiation devices, ie, lasers, include Millennia (Spectra Physics) and Verdy (Coherent) as continuous wave lasers.
Typical examples of the pulsed laser include T / J20-V80-106Q (Spectra Physics) and ZT-15 (Coherent).
Examples of the laser light source of the laser beam irradiation apparatus include a YAG laser (wavelength 1064 nm), a YAG-SHG laser (wavelength 532 nm), and the like.
[0016]
As a method for obtaining the pulsed laser light, for example, the following two methods can be used.
(1) A method of obtaining pulsed laser light by pulsing continuously oscillated laser light using an external modulator.
(2) A method for obtaining pulsed laser light using a Q-switched pulsed laser.
In the method (1), the laser light obtained by the continuous wave laser is pulsed by passing it through an external modulator such as EOM or AOM. This method is preferable in that a pulsed laser beam having excellent repeatability can be obtained and the pulse width can be arbitrarily set.
[0017]
The EOM is an electro-optic-modulator (electric-optic-modulator), which applies the voltage to the optical crystal and changes the refractive index of the crystal to change the refractive index of the crystal. The laser output is continuously changed by changing the optical path.
AOM is an acousto-optic modulator, and the diffraction angle of the continuous-wave laser light incident on the optical crystal by introducing the ultrasonic wave from the outside and utilizing the optical elastic effect of the crystal. By changing, the laser output that passes straight through is continuously changed.
[0018]
The method (2) is a method of obtaining a high output pulse by switching the Q value of the laser resonator using a Q-switch pulse laser provided with a laser resonator. The laser resonator has a built-in modulator such as EOM or AOM, and the laser light is pulsed by controlling the operation of the modulator with an external electric signal.
Generally used Q-switched pulse laser has a pulse width of 10 to 80 ns, so it is not suitable for manufacturing the protruding structure 10 in the present invention. However, if a special Q-switched pulse laser with a long pulse width is used, The protruding structure 10 can be formed. For example, if ZT-15 (wavelength 1064 nm, manufactured by Coherent Co., Ltd.) is used at 150 kHz, the pulse width becomes 110 nm, and the protruding structure 10 can be formed.
[0019]
The pulse width of the laser light (half-value width of the pulse waveform when the laser light is detected by a photo director) is 100 ns or more, and preferably in the range of 100 to 1000 ns. With such a configuration, it is easy to control the shapes of the convex portions 11 and the concave portions 12 of the projecting structure 10, and a good projecting structure 10 can be formed on the magnetic recording medium 6.
Further, the irradiation beam diameter of the laser light is preferably 0.1 to 30 μm, more preferably 1 to 30 μm, and still more preferably 8 to 30 μm.
[0020]
FIG. 5 shows the relationship between the height h1 of the protrusion 11 in the projecting structure and the laser power with a pulse width of 500 ns (with a long pulse width in the figure) and 50 ns (with a short pulse width in the figure). This is a comparison.
Further, FIG. 6 shows the relationship between the depth h2 of the recess 12 in the projecting structure and the laser power, with a pulse width of 500 ns (with a long pulse width in the figure) and 50 ns (with a short pulse width in the figure). And compared.
[0021]
From FIG. 5, it can be seen that the longer the pulse width, the gentler the slope of the graph of the laser power and the height h1 of the convex portion 11. From this, it can be understood that the longer the pulse width, the smaller the fluctuation in the height h1 of the convex portion 11 with respect to a certain amount of laser power fluctuation.
Similarly, as shown in FIG. 6, the slope of the graph of the laser power and the depth h2 of the recess 12 is gentler for the longer pulse width. It can be seen that the longer one has less variation in the height h2 of the recess 12. In FIG. 6, the depth h <b> 2 of the concave portion 12 is saturated when the laser power is equal to or higher than a certain level. That is, the concave portion 12 penetrates the film formation layer 5 and reaches the substrate 1. This is because no further processing is possible. Such a phenomenon is often seen when the substrate 1 is a glass substrate. This is because glass hardly exhibits workability with respect to laser light having a wavelength of 200 to 1100 nm.
[0022]
FIG. 7 is a graph showing the relationship between the laser power and the pulse width. The pulse width at the start of machining (the number of pulses when the height h1 of the convex portion 11 is 10 nm) and all the protrusions formed The pulse width when the substrate 1 is exposed in the shaped structure 10, in other words, the pulse width when the convex portion 11 cannot be formed any more is shown. From this graph, it can be seen that the laser power is smaller and the processing start pulse width is longer, the width between the number of pulses when the substrate is exposed is larger. It can be seen that this width becomes narrower as the laser power is larger and the pulse width is shorter. From this, it can be said that a longer pulse width is suitable for controlling the height of the convex portion 11 or controlling the depth of the concave portion 12.
[0023]
From such an experiment, it was found that the longer the pulse width of the laser beam irradiated onto the magnetic recording medium 6, the easier it is to control the shapes of the convex portions 11 and the concave portions 12.
Further, it was found in the next experiment that the specific pulse width is preferably 100 ns or more. Next, this experiment will be described.
The relationship between the pulse width and the height h1 of the protrusion 11 of the protruding structure was examined using the following apparatus.
The experimental conditions were as follows.
As the laser, MillenniaX (continuous oscillation, wavelength 532 nm, output 10 W, manufactured by Spectra Physics) was used, and laser light was pulsed using an external modulator EOMmode 1370-LA (manufactured by Conoptics, Inc.). × 5 (manufactured by Olympus) was used.
In addition, as the magnetic recording medium, an underlayer, a magnetic film, and a protective layer were sequentially formed on a glass substrate, and the total thickness of these formed layers was 100 nm.
Then, the laser was irradiated while rotating the magnetic recording medium, a projecting structure was formed under the following conditions, and marking was performed.
Processing speed: 4m / s
Processing pulse frequency: 200 kHz
Processing pitch: 20 μm in the radial direction, 20 μm in the circumferential direction
Processing range: 100 μm on the circumference
[0024]
Under the above experimental conditions, the amount of change in the height of the convex portion of the protruding structure formed on the magnetic recording medium when the pulse width of the laser beam was changed was examined. The results are shown in Table 1.
From this result, if the depth h2 of the recess 12 is controlled around 60 nm, the fluctuation at 100 ns can be about 60 ± 20 nm. When the pulse width is less than this value, it is difficult to manage the depth of the recess 12 within 100 nm (thickness of the film formation surface), and it is understood that the lower limit is around 100 ns. For this reason, the pulse width of the laser is preferably 100 ns or more.
[0025]
[Table 1]

[0026]
Moreover, as a wavelength of a laser beam, 200-1100 nm is preferable. If it is less than 200 nm, there is a concern about the generation of ozone, and in order to prevent this generation, the non-oxygen projecting structure 10 must be formed, which is troublesome. In addition, many lasers that emit laser light are inferior in repeatability and stability, such as an excimer laser, and the height of the formed protrusions is likely to be uneven, and the cost is also undesirable. On the other hand, if the wavelength exceeds 1100 nm, the absorption to the metal falls, so that the protruding structure 10 cannot be formed on the film formation layer 5, which is not preferable. In addition, a laser having a wavelength in this range is difficult to be absorbed by glass, and thus can be said to be particularly suitable when laser irradiation is performed on a magnetic recording medium having a glass substrate as the substrate 1. Conversely, glass is, for example, CO₂Such a wavelength is not suitable for a laser with a laser wavelength of 10.6 μm because particles are more likely to be absorbed than metal.
[0027]
In addition, in order to form a plurality of protruding structures 10 on the magnetic recording medium 6 by irradiating such laser light, and to form markings such as identification symbols and characters, the magnetic recording medium 6 It is preferable to irradiate a pulsed laser beam in synchronization with the rotation Z-phase signal of the magnetic recording medium 6 while rotating the magnetic recording medium 6.
At this time, it is preferable that characters are printed by moving either the magnetic recording medium 6 or the condenser lens in the radial direction of the magnetic recording medium 6 while rotating the magnetic recording medium 6. Since only the rotation direction of the magnetic recording medium 6 is a one-dimensional movement, two-dimensional movement is possible by moving either the magnetic recording medium 6 or the condenser lens in the radial direction of the magnetic recording medium 6. Characters can be printed.
In addition, as the condensing lens used at this time, any one of a convex lens, an achromatic lens, a microscope objective lens, and the like may be used. However, if the focal distance is too small, the depth of focus cannot be obtained, which is not preferable. If the focal distance is too large, the continuous wave laser cannot be used for processing. Therefore, the focal range is preferably 10 to 80 μm.
[0028]
As a method of rotating the magnetic recording medium 6, it is preferable to use a motor or the like. Examples of the motor include a DC (servo) motor, an AC (servo) motor, and a stepping motor. As such a motor, a motor capable of outputting a Z-phase signal is preferable. The Z-phase signal is an output signal of one pulse for one rotation of the rotating shaft, and in this case, it can be used for the origin of positioning of the laser irradiation position. Further, any signal having the role of positioning origin can be used in place of the Z signal. For example, if the output signal is an A-phase signal with 1024 pulses per revolution, it can be used as the origin signal by counting the output signal 1024 times.
[0029]
Next, the manufacturing method of the magnetic recording medium of the present invention will be described by taking as an example the case of printing on the magnetic recording medium using the letter A as a marking.
First, the character information is represented as a dot pattern as shown in FIG. In this case, the alphabet A was represented as 10 × 10 dots.
Next, this dot pattern is converted into a digital signal. For example, as shown in FIG. 4, the black portion of the dot pattern A in FIG.
Next, a line of the converted digital signal is input to a pulse generator such as a data generator as a combined signal. In this case, since A is represented by 10 × 10 dots, each row is a 10-bit digital signal. For example, each row is 0000110000, the second row is 0000110000, and the third row is 0001111000. The digital signal is input to the pulse transmitter.
Next, a sequence is created in the pulse transmitter, and when a trigger signal is input once, one row of digital signals is output each time. Further, when the trigger signal is input once, the digital signal of the next row is output once. This process is repeated until information such as characters is completed. For example, in this case, the process is repeated until the 10th line ends.
A Z-phase signal is used as a trigger signal at this time, and marking is performed so that the condensing lens moves in a uniaxial direction while rotating the magnetic recording medium. At this time, the pulse width at the time of marking is set to a range suitable for producing the above-described protruding structure.
[0030]
In this way, one line of the digital signal is printed at the origin position of one rotation of the magnetic recording medium. If this is repeated for each digital signal in each row, a character or the like, in this case, A can be printed.
As described above, when the origin signal is used as the trigger signal, the origin position and a line of information such as characters come to substantially the same position. Therefore, the line direction of printing does not shift. The Z-phase signal is generated once per rotation while the magnetic recording medium is rotating. However, in practice, since it is a part of the time between markings, it is necessary to generate a Z-phase signal sufficient for marking. This is because the relay is turned on only during marking. It can be easily realized by a simple sequencer.
If the marking method is performed by estimating the rotation time without using the origin signal, the printing is shifted in the line direction due to variations in rotation.
[0031]
In a general leather marking apparatus, a galvanometer mirror and an fθ lens are used in order to directly express characters and the like. The galvanometer mirror is composed of two mirrors, and by controlling the two mirrors, two-dimensional drawing is possible and characters and the like can be directly expressed. When this galvanometer mirror is used, the incident angle and the incident position of the laser beam to the condenser lens change, so it is difficult to focus on the same surface with a commonly used condenser lens. The fθ lens is used to solve this problem. By increasing the focal length of the fθ lens, the same surface can be used even if the incident angle and incident position of the laser beam to the condenser lens change. It is possible to focus on the top.
For example, with a Yfθ lens (manufactured by Sigma Koki Co., Ltd.), the scanning distance becomes as short as φ240, 120, and 60 mm as the focal length becomes as small as 300, 150, and 100 mm.
[0032]
Thus, in a conventional laser marking device, when a continuous wave laser beam is pulsed using an external modulation device, a lens with a long focal length cannot be used because its peak power is small. .
However, if the above-described magnetic recording medium is rotated and the laser light is pulse-oscillated in synchronization with the Z-phase signal of the rotation of the magnetic recording medium, such laser light is pulsed using an external modulator. Even if a normal condensing lens with a short focal length is used, symbols, characters, etc. can be printed accurately.
In general, pulsed laser light is used as the laser texture method.
Therefore, for example, the laser method used for the laser texture method can be used for laser marking as it is.
In this way, the marking can be easily formed on the magnetic recording medium 6.
[0033]
According to the manufacturing method of the magnetic recording medium in which the projecting structure 10 is formed on the surface of the magnetic recording field plate 6 using such laser light and marking is performed, the wavelength and pulse width of the laser light are optimized. Since it is set, it is possible to accurately set the height of the convex portion 11, the depth of the concave portion 12, the formation position, and the like of the protruding structure 10. In addition, since this forming method is basically a dry process, it is possible to prevent impurities from being mixed into the magnetic recording medium 6.
Further, in such a method of manufacturing the magnetic recording medium 6, the magnetic recording medium 6 is rotated, and a plurality of laser beams are irradiated by irradiating the pulsed laser light in synchronization with the Z-phase signal of the rotation of the magnetic recording medium 6. Therefore, the marking 7 indicating symbols and characters can be easily and accurately formed on the magnetic recording medium 6.
[0034]
In addition, such a method of marking the magnetic recording medium 6 after film formation is, for example, a magnetic recording medium 6 that can be used as a recording surface only on one side, and a recording surface and a non-recording surface are identified on the surface. Can be used for
A normal magnetic recording medium 6 has recording surfaces on both sides in order to improve the recording capacity. However, the manufactured magnetic recording medium 6 includes one having one surface that is defective as a recording surface. Here, this defective surface is a non-recording surface.
The recording surface (normal surface) and the non-recording surface (defective surface) in the magnetic recording medium 6 are characterized by their surface characteristics by tests such as surface inspection and electromagnetic conversion characteristic inspection performed after the production of the magnetic recording medium 6. It can be understood for the first time. Therefore, marking for discriminating between the recording surface and the non-recording surface must be performed after these inspections, that is, after manufacturing the magnetic recording medium 6 (after forming the magnetic film). The marking forming method in (1) is preferably used.
[0035]
The marking 7 formed on the magnetic recording medium 6 having such a recording surface and a non-recording surface may be formed on either the recording surface or the non-recording surface of the magnetic recording medium.
If the marking 7 is formed on the non-recording surface, the protruding structure 10 is formed at an arbitrary position on the non-recording surface of the magnetic recording medium 6 without impairing the characteristics of the recording surface of the magnetic recording medium 6. And the identification becomes easy.
Further, as the formation position when the marking 7 is formed on the recording surface, for example, the non-recording area 101 in the magnetic recording medium 6 as shown in FIG. 1 is preferable. The innermost peripheral region 102 is preferably formed. In this way, even when the marking 7 is formed on the recording surface, the recording characteristics of the magnetic recording medium 6 are not deteriorated.
[0036]
Conventionally, such a magnetic recording medium 6 that can be used as a recording surface only on one side has been discarded as a defective product.
However, recently, even such a magnetic recording medium 6 that can be used on only one side has been made practical. This is because, conventionally, in a hard disk drive (HDD), two magnetic recording heads have been used per magnetic recording medium, so that the recording capacity can be increased by using both surfaces of the magnetic recording medium 6 as recording surfaces. Although there has been a circumstance that the improvement has been achieved, in recent years, the recording density of HDDs has been remarkably improved, and in the use of a normal personal computer (PC), the required recording capacity can be obtained by using only one side of the magnetic recording medium 6. This is because more and more people are satisfied.
[0037]
Under such circumstances, even if the magnetic recording medium 6 has not been used because one of the recording surfaces is defective at the stage of inspection after the magnetic recording medium has been manufactured, the recording surface on one side is normal. Thus, it can be considered that the magnetic recording medium 6 can be sufficiently used. Therefore, if only one side, which has been discarded as a defective product in the past, can use the normal magnetic recording medium 6 effectively, a significant cost reduction can be realized.
When the magnetic recording medium 6 having such a good recording surface on only one side is used, it is necessary to distinguish between a normal recording surface and a non-recording surface that is not.
[0038]
Therefore, if the magnetic recording medium 6 is subjected to the marking, the recording surface of the magnetic recording medium 6 can be easily distinguished from the non-recording surface by visual inspection. Therefore, such a magnetic recording medium 6 that can be used only on one side can be put into practical use. Thereby, the manufacturing cost of the magnetic recording medium 6 can be greatly reduced, and the cost of the magnetic recording / reproducing apparatus can be reduced by using the magnetic recording medium 6 that can be used only on one side for the magnetic recording apparatus.
[0039]
In addition, this invention is not limited to such a use, It can be used for the marking 7 of various uses. For example, it can be used for identification of the serial number and date of the magnetic recording medium 6 used on both sides.
The present invention can also be used for marking on a magnetic recording medium having no CSS zone.
[0040]
FIG. 9 shows an embodiment of a marking device for a magnetic recording medium according to the present invention. This device comprises a laser light source 21, a condensing lens 22 for condensing the laser light emitted from the laser light source 21, and And a substrate holding device 23 for holding the magnetic recording medium D to be marked. As the condenser lens 22, a kaleidoscope or the like can be used in addition to a convex lens achromatic lens, a microscope objective lens, and the like.
[0041]
The kaleidoscope is an optical device for converting laser light into parallel light having a uniform energy density. As shown in FIG. 10, a kaleidomirror that collimates incident light in a cylindrical scope body 30 by multiple reflection. 31 and a reflecting mirror 32 that changes the direction of the emitted light from the kaleido mirror 31, and a condensing lens 33 that arranges the optical path of the reflected light from the reflecting mirror 32 is provided on the outer periphery of the main body 30. is there. This kaleidoscope is preferable for use as the condensing lens 22 because the energy density of the laser beam can be made uniform.
Further, the substrate holding device 33 is configured to rotate the magnetic recording medium D to be subjected to the marking process in the circumferential direction at a predetermined rotation speed.
The marking device for the magnetic recording medium of the present invention is not limited to these devices, and can be configured to include other external modulators, various control devices, and the like.
[0042]
With such a recording medium marking device, a plurality of the protruding structures 10 can be easily formed on the magnetic recording medium 6 after film formation.
[0043]
FIG. 11 shows an example of a magnetic recording / reproducing apparatus using the magnetic recording medium. The magnetic recording / reproducing apparatus shown here includes a magnetic recording medium 6, a medium driving unit 41 that rotationally drives the magnetic recording medium 6, a magnetic head 42 that records and reproduces information on the magnetic recording medium 6, a head driving unit 43, And a recording / reproducing signal processing system 44. The recording / reproducing signal processing system 44 can process an external recording signal and send it to the magnetic head 44, or can process a reproducing signal from the magnetic head 42 and send it to the outside.
With such a magnetic recording / reproducing apparatus, even a magnetic recording medium 6 that can be used on only one side can be used in the interior thereof. Therefore, the manufacturing cost can be reduced, and the cost can be reduced.
[0044]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
A processing range in a non-recording area 101 of a magnetic recording medium 6 in which an underlayer 2 made of a Cr alloy, a magnetic film 3 made of a Co alloy, and a protective layer 4 made of carbon are sequentially formed on a glass substrate 1 made of lithium silicate glass. A plurality of protruding structures 10 were formed by the following apparatus and method. At this time, the film pressure of the film formation layer 5 including the underlayer 2, the magnetic film 3, and the protective layer 4 formed on the substrate 1 was 100 nm.
MillenniaX (continuous oscillation, wavelength 532 nm, output 5 W, manufactured by Spectra Physics) was used as a laser light source, and the laser was pulsed using an external modulator EOM mode 1370-LA (manufactured by Conoptics, Inc.). MSPlan × 5 (manufactured by Olympus) was used.
Then, while rotating the magnetic recording medium 6, the laser was irradiated at a processing pulse frequency of 200 kHz, a laser output of 2.5 W, and a pulse width of 500 ns. The collecting speed of the rotating magnetic recording medium 6 at this time was 4 m / s, the pitch was 20 μm in the radial direction, and the processing range was 100 μm on the circumference.
[0045]
As a result, it was possible to form a plurality of protruding structures 10 having a height of the protrusion 11 of 50 nm at a predetermined position of the magnetic recording medium 6. The shape was good, and there was no protruding structure 10 with the glass substrate exposed.
[0046]
(Example 2)
A plurality of protruding structures in which the height of the protrusions 11 is 50 nm on the magnetic recording medium 6 in the same manner as in Example 1 except that an aluminum substrate plated with nickel phosphorus is used as the substrate 1 of the magnetic recording medium 6 10 was formed.
As a result, the protruding structure 10 could be easily formed at a predetermined position of the magnetic recording medium 6. The shape was good, and there was no protruding structure 10 in which the nickel phosphorus underlayer of the aluminum substrate was exposed.
[0047]
(Example 3)
The magnetic recording medium is the same as in Example 1 except that Millennia V (continuous oscillation, wavelength 532 nm, output 5 W, manufactured by Spectra Physics) is used as the laser light source, the laser output is 0.8 W, and the continuous oscillation laser is used. A plurality of protruding structures 10 having a height of the convex portion 11 of 50 nm was formed on 6.
As a result, the protruding structure 10 can be easily formed at a predetermined position of the magnetic recording medium 6. The shape was good, and there was no protruding structure 10 with the glass substrate exposed.
[0048]
(Example 4)
As in Example 1, except that ZT-15 (pulse oscillation, wavelength 1064 nm, output 2 W, manufactured by Coherent Co., Ltd.) was used as the laser light source, the processing pulse frequency was 150 kHz, the laser output 0.15 W, and the pulse width 110 ns. A plurality of projecting structures 10 having a height of the convex portion 11 of 50 nm were formed.
As a result, the protruding structure 10 could be easily formed at a predetermined position of the magnetic recording medium 6. The shape was good, and there was no protruding structure 10 with the glass substrate exposed.
[0049]
(Comparative Example 1)
Except that the pulse width of the laser beam was set to 1500 ns, a plurality of protruding structures 10 having a height of the convex portion 11 of 200 nm were formed in the same manner as in Example 1.
However, the glass base material was exposed in all the protruding structures 10 formed.
[0050]
(Comparative Example 2)
Except that the pulse width of the laser beam was set to 1500 ns, a plurality of protruding structures 10 having a height of the convex portion 11 of 200 nm were formed in the same manner as in Example 2.
However, in all the protruding structures 10 formed, the nickel phosphorous plating portion of the aluminum base material was exposed.
[0051]
(Comparative Example 3)
Example 1 except that 501QM-VD (pulse oscillation, wavelength 1064 nm, output 1.5 W, manufactured by Coherent) was used as the laser light source, the processing pulse frequency was 10 kHz, the laser output was 0.01 W, and the pulse width was 10 ns. In the same manner as described above, a plurality of protruding structures 10 having a height of the convex portion 11 of 50 nm were formed.
As a result, the glass substrate was exposed in about 30% of the formed protruding structure 10. At this time, even if the laser output was varied, it was impossible to obtain the protruding structure 10 in which the glass substrate was not exposed.
[0052]
The corrosion properties of the magnetic recording medium 6 after the formation of the protruding structures 10 of Example 1 and Comparative Example 1 were evaluated. For evaluation of the corrosion property, each magnetic recording medium 6 was immersed in warm water at a temperature of 80 ° C. for 60 minutes and extracted with warm water, and the amount of lithium ions in the warm water was measured by ICP-MS. At this time, the same test as that of the magnetic recording medium 6 used in Example 1 that was not laser-treated was used as a reference. The results are shown in Table 2.
From this result, it was found that a larger amount of lithium ions was precipitated from the magnetic recording medium 6 of Comparative Example 1 than in Example 1 and the reference magnetic recording medium 6.
[0053]
The corrosion properties of the magnetic recording medium 6 after the formation of the protruding structures 10 of Example 2 and Comparative Example 2 were evaluated. Evaluation of the corrosion property was carried out by leaving each magnetic recording medium 6 in an oven at a temperature of 80 ° C. and a humidity of 80% for 168 hours, and then immersing in warm water at a temperature of 25 ° C. for 60 minutes to extract the hot water. The amount of ions was measured by ICS-MS. A similar test was performed using the same magnetic recording medium 6 as used in Example 2 that was not laser-treated as a reference. The results are shown in Table 2. From this result, it was found that a larger amount of nickel ions was precipitated from the magnetic recording medium 6 of Comparative Example 2 than in Example 2 and the reference magnetic recording medium 6.
[0054]
[Table 2]

[0055]
(Example 5)
The laser includes Millenia V (Spectra Physics, output 5W), laser output 2.5W, EMO mode 1370-LA (manufactured by Conoptics. Inc.) as an external modulator, and microscope objective lens MSPlan × 5 (manufactured by Olympus) as a condenser lens. , Focal length 36 mm) An AC servo motor (manufactured by Shin Meiwa) is used as the motor, the magnetic recording medium 6 used in Example 1 is used as the magnetic recording medium 6, and the processing peripheral speed of the magnetic recording medium 6 is 4 m / min. While rotating at s, the processing pitch was set to 20 μm in the radial direction, and the circumferential interval was controlled to form the protruding structure 10 on the surface, thereby printing the letter A.
Then, as shown in FIG. 3, the letter A is converted to a digital signal with 10 × 10 dots and the white portion is set to 0 and the black portion is set to 1, and the laser is pulsed only when the digital signal is 1. Oscillation was performed to form the protruding structure 10.
Then, the digital signal obtained by converting the letter A shown in FIG. 4 is taken into the data generator DZ2020 (manufactured by Sony Tektronix) for each row, and when the trigger signal is input, the corresponding digital signal is oscillated once in sequence. It was to so. Further, since the clock frequency of the data generator is 2 MHs, if the digital signal is transmitted as it is, dots of 2 μm intervals are formed. Therefore, when the digital signal is 0, the digital signal is 1000000, when it is 1 Was adjusted so that the interval between dots was 20 μm. At this time, the pulse width per pulse of the laser light was 500 ns. A Z-phase signal from an AC servometer was used as the trigger signal.
As a result, a character A of 200 × 200 μm square could be neatly produced without any deviation in the row direction. Moreover, the height h1 of the convex part 11 of the protruding structure 10 at this time was 500 nm.
[0056]
(Comparative Example 4)
For the laser, MilleniaZ (Spectra Physics, output 10W)
Laser output 10 W, EMO mode 1370-LA (manufactured by Conoptics, Inc.) as an external modulator, Yfθ lens (manufactured by Sigma Koki Co., Ltd., focal length 100 mm) as a condensing lens, and magnetic recording medium 6 similar to that in Example 1 Using this, the magnetic recording medium 6 was stopped, and the galvanometer mirror was moved to perform the printing of A above.
As a result, the protruding structure 10 could not be formed on the magnetic recording medium 6 and the letter A could not be printed.
[0057]
【The invention's effect】
As described above, the magnetic recording medium of the present invention is a magnetic recording medium in which at least a magnetic film is formed on a substrate, and a marking comprising a plurality of protruding structures that can be visually identified on the recording medium. Therefore, various identifications in the magnetic recording medium can be easily performed visually. For example, if the magnetic recording medium has a recording surface and a non-recording surface, the identification can be easily performed. In addition, with such a magnetic recording medium, a magnetic recording medium that is good only on one side, which has been regarded as a defective product, can be used as a product, and a significant cost reduction can be achieved.
[0058]
Further, if the height of the protrusions of the protruding structure is 10 nm or more and (total thickness of the layers formed on the substrate) × 2 nm or less, it is visible and easy to understand, and the resistance of the magnetic recording medium It is possible to obtain a magnetic recording medium on which marking has been performed without reducing the corrosion property.
If the depth of the concave portion of the projecting structure is 10 nm or more and (total thickness of the layer formed on the substrate) nm or less, it is similarly visible and easy to understand, and the corrosion resistance of the magnetic recording medium. It is possible to obtain a magnetic recording medium on which marking has been performed without reducing the above.
Furthermore, if the total thickness of the layers formed on the substrate is 10 to 300 nm, good marking can be easily performed.
If the marking is a symbol or character that can be visually identified, the magnetic recording medium can be more easily identified.
Further, according to the magnetic recording medium in which the normal surface (recording surface) and the defective surface are identified by the marking, a magnetic recording medium that can be used only on one side that has been conventionally discarded can be used as a product. It becomes possible and a significant cost reduction is possible. Further, if this magnetic recording medium is used in a magnetic recording apparatus, the manufacturing cost of the magnetic recording apparatus can be reduced.
[0059]
According to the method for producing a magnetic recording medium of the present invention, the projecting structure is formed by irradiating the magnetic recording medium with pulsed laser light or pulsed continuous wave laser light. By forming a plurality of the protruding structures on the magnetic recording medium after film formation, it is possible to easily form a marking that can be visually identified. Specifically, the height of the convex portion is 10 nm or more and (total thickness of the layer formed on the substrate) × 2 nm or less, and the depth of the concave portion is 10 nm or more (of the layer formed on the substrate). A plurality of protruding structures having a total thickness (nm) or less can be easily formed on the magnetic recording medium.
In addition, in this method, the protruding structure can be formed at a precise position on the magnetic recording medium by the laser beam, so that markings such as symbols and characters having a clear outline and a precise shape can be magnetically recorded. It can be formed on the surface of the medium.
Further, in the method for manufacturing the magnetic recording medium, if the wavelength of the laser beam is 200 to 1100 nm and the pulse width is 100 ns or more, the height of the convex part, the depth of the concave part, etc. are controlled. A projecting structure having a good shape with little variation in these values can be obtained.
[0060]
According to the marking device for a magnetic recording medium of the present invention, the protruding structure having the above shape can be easily formed, and the magnetic recording medium can be easily manufactured. In the magnetic recording / reproducing apparatus of the present invention, even a magnetic recording medium having a normal recording surface and a defective recording surface and discarded in the past can be used. be able to.
[Brief description of the drawings]
FIG. 1 is a plan view showing an example of a magnetic recording medium of the present invention.
FIG. 2A is a plan view showing an example of a protruding structure formed on a magnetic recording medium of the present invention.
(B) It is sectional drawing seen from the A-A 'direction in (a).
FIG. 3 is a diagram showing an example of a marking formed on the magnetic recording medium of the present invention as a dot pattern.
FIG. 4 is a diagram showing a marking dot pattern in FIG. 3 as a digital signal.
FIG. 5 is a graph showing the relationship between the height h1 of the protrusion and the leather power in an example of the protruding structure formed on the magnetic recording medium of the present invention.
FIG. 6 is a graph showing the relationship between the depth h2 and the leather power in the recesses in an example of the protruding structure formed on the magnetic recording medium of the present invention.
FIG. 7 is a graph showing the relationship between the laser beam power and the pulse width of laser light when forming the protruding structure formed on the magnetic recording medium of the present invention.
FIG. 8 is a cross-sectional view illustrating an exemplary structure of a magnetic recording medium.
FIG. 9 is a schematic configuration diagram showing an example of a marking device for a magnetic recording medium according to the present invention.
FIG. 10 is a schematic configuration diagram showing an example of a kaleidoscope used in the magnetic recording medium marking device of the present invention.
FIG. 11 is a schematic configuration diagram showing an example of a magnetic recording / reproducing apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Base film, 3 ... Magnetic film, 4 ... Protective film, 5 ... Film-forming layer
6 ... Magnetic recording medium, 7 ... Marking
DESCRIPTION OF SYMBOLS 10 ... Projection-like structure, 11 ... Convex part, 12 ... Concave part

Claims (6)

A magnetic recording medium in which at least a magnetic layer is formed on the substrate, on the recording medium, identifiable markings formed visually, Ri Do this marking from a plurality of the protruding structure, and, the magnetic A magnetic recording medium having a normal surface and a defective surface, wherein the normal surface and the defective surface can be distinguished by the marking .   2. The magnetic recording medium according to claim 1, wherein the height of the protrusions of the protruding structure is 10 nm or more and (total thickness of layers formed on the substrate) × 2 nm or less.   3. The magnetic recording medium according to claim 1, wherein a depth of the concave portion of the projecting structure is 10 nm or more and a total thickness of the layers formed on the substrate) nm or less.   4. The magnetic recording medium according to claim 1, wherein the total thickness of the layers formed on the substrate is 10 to 300 nm. 5.   5. The magnetic recording medium according to claim 1, wherein the marking indicates a symbol or a character. A magnetic recording medium and a magnetic head for recording / reproducing information on the magnetic recording medium are provided, and the magnetic recording medium is the magnetic recording medium according to any one of claims 1 to 5. Magnetic recording / reproducing device.

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