JP2004055011A - Optical recording medium and optical recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium having a wobbling amplitude that can improve both of the reproducing signal quality of additional information and data recording/reproducing quality. <P>SOLUTION: In the optical recording medium, the wobbling amplitude of a groove 2 is set in the range of properly securing the reproducing signal quality of additional information (address information or clock information), and in the range of recording/reproducing data well ( the experimentally obtainable range ) by preventing the influence of wobbling. That is, when the numerical aperture of an objective lens is NA and the wavelength of a recording laser beam is λ in the optical recording/reproducing device, the absolute value A of the wobbling amplitude of the groove 2 is set to satisfy 0.0044≤A×NA/λ≤0.0133. Thus, both of the reproducing signal quality of the additional information and data recording/reproducing quality is heightened. <P>COPYRIGHT: (C)2004,JPO

Description

【００７２】
表１は、各サンプルのウォブリング振幅量と、Ｄ−ＢＥＲ，Ｗ−ＣＮＲ，Ｉｗ／ＩｏおよびＩｗ／Ｉｔの測定結果とを示す表である。
【００７３】
ウォブリング信号は、３２ｄＢ以上のＷ−ＣＮＲを有する場合に、回転制御信号および／またはアドレス信号として実用可能である。そして、３２ｄＢ以上のＷ−ＣＮＲは、表１より、ウォブリング振幅量を±３ｎｍ以上とする場合に実現できることがわかる。
【００７４】
一方、データ信号は、１×１０^−４以下のＤ−ＢＥＲを有する場合に、再生のための信号として実用可能である。そして、１×１０^−４以下のＤ−ＢＥＲは、表１より、ウォブリング振幅量を±９ｎｍ以下とする場合に実現できることがわかる。
以上の結果から、ウォブリングの振幅量を、±３ｎｍから±９ｎｍの範囲とすることが好ましいといえる。
【００７５】
また、ウォブリング信号は、３４ｄＢ以上のＷ−ＣＮＲを有する場合に、回転制御信号および／またはアドレス信号として非常に有効に使用できる。
さらに、データ信号は、８×１０^−５以下のＤ−ＢＥＲを有する場合に、再生のための信号として非常に好ましい。
従って、ウォブリングの振幅量は、±４ｎｍから±６ｎｍの範囲であればより好ましいといえる。
【００７６】
また、記録および再生に用いるレーザ光の波長（λ）を４０５ｎｍ、対物レンズ３８のＮＡを０．６としているので、この測定におけるレーザ光のスポット径変数（λ／ＮＡ）は、６７５ｎｍである。従って、スポット径変数に対する良好なウォブリング振幅量（±Ａ；Ａは絶対値）の比（Ａ×ＮＡ／λ）の範囲は、
０．００４４≦Ａ×ＮＡ／λ≦０．０１３３となる。
なお、レーザ光のスポット径変数（λ／ＮＡ）とは、レーザ光のスポット径を定数で割ったものである。
【００７７】
さらに、表１に、各サンプルにおけるＩｗ／Ｉｏ，Ｉｗ／Ｉｔを示した。
ここで、Ｉｗ／Ｉｏは、トラックエラー信号におけるウォブリング信号量（Ｉｗ；ウォブリング信号振幅量）と、溝のない部分からの反射光を光電変換して得られる電気信号量（Ｉｏ）との比である。
【００７８】
また、Ｉｗ／Ｉｔは、上記のＩｗと、オフトラック時のトラックエラー信号量（Ｉｔ）との比である。
ここで、オフトラック時とは、トラックサーボをかけていないとき、のことである。このときは、トラックの偏心により、光スポットは複数のトラックを横切っている状態にある。すなわち、Ｉｔは、光スポットが複数トラックを横切った場合における、トラックエラー信号の信号振幅量である。
【００７９】
各サンプルのウォブリングにおける物理的な振幅量（ウォブリング物理振幅量）が同一であっても、検出されるウォブリング信号量は、サンプルの反射率やトラック形状により変化する。
そして、Ｉｗ／Ｉｏは、サンプルの反射率によってウォブリング信号量（Ｉｗ）を規格化したものである。これにより、ウォブリング信号量（Ｉｗ）を、反射率の影響を除いて評価できる。
また、Ｉｗ／Ｉｔは、トラックエラー信号量（Ｉｔ）によってウォブリング信号量（Ｉｗ）を規格化した値である。これにより、ウォブリング信号量（Ｉｗ）を、トラック形状の影響を除いて評価できる。
【００８０】
そして、上記したように、ウォブリング信号は、３２ｄＢ以上のＷ−ＣＮＲを有する場合に、アドレス信号（および／またはクロック信号）として実用可能である。そして、３２ｄＢ以上のＷ−ＣＮＲは、表１より、Ｉｗ／Ｉｏを０．０１０以上とする場合に実現できることがわかる。
【００８１】
一方、データ信号は、１×１０^−４以下のＤ−ＢＥＲを有する場合に、再生のための信号として実用可能である。そして、１×１０^−４以下のＤ−ＢＥＲは、表１より、Ｉｗ／Ｉｔを０．０７１以下とする場合に実現できることがわかる。
従って、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１の範囲であれば、良好な再生信号品質を得られるといえる。
【００８２】
〔実験２〕
実験２では、１０種類の溝深さ（グルーブの深さ）および様々なウォブリング振幅量を有する複数の本ディスクのサンプルを作成し、上記した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。
なお、各サンプルの層構成、および、各サンプルに対するデータの記録・再生条件は、実験１において示したものと同様とした。
【００８３】
【表２】

【００８４】
表２は、各サンプルに対する測定において、Ｄ−ＢＥＲが１×１０^−４以下となり、かつ、Ｗ−ＣＮＲが３２ｄＢ以上となるような、ウォブリング振幅量，Ｉｗ／ＩｏおよびＩｗ／Ｉｔの範囲と、各サンプルの溝深さ（ｄ）との関係を示す表である。
【００８５】
また、この表２には、レーザ光の波長と光路長との比である、λ／（ｎ×ｄ）の値も示している。ここで、ｎは、光の入射する側に位置する層の屈折率、すなわち、ディスク基板１の屈折率である。そして、このλ／（ｎ×ｄ）の値は、光波の位相に反比例するものであり、溝深さを位相の逆数で規格化したものである。
【００８６】
この表に示すように、５．５≦λ／（ｎ×ｄ）≦１６を満たす場合、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１となり、良好な再生信号品質を得られることがわかる。
【００８７】
〔実験３〕
実験３では、８種類のトラックピッチを有する複数の本ディスクのサンプルを作成し、上記した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。
【００８８】
なお、各サンプルの層構成、および、各サンプルに対するデータの記録・再生条件は、実験１において示したものと同様とした。また、各サンプルのグルーブ幅およびグルーブ間距離（ランド幅）は、ほぼ等しくした。
【００８９】
【表３】

【００９０】
表３は、各サンプルに対する測定において、Ｄ−ＢＥＲが１×１０^−４以下となり、かつ、Ｗ−ＣＮＲが３２ｄＢ以上となるような、ウォブリング振幅量，Ｉｗ／ＩｏおよびＩｗ／Ｉｔの範囲と、各サンプルのトラックピッチ（ＴＰ）との関係を示す表である。
また、この表には、トラックピッチ（ＴＰ）をスポット径変数によって規格化した値であるＴＰ×ＮＡ／λも示している。
【００９１】
本ディスクを高密度化（大容量化）するためには、トラックピッチおよびＴＰ×ＮＡ／λは小さい程よい。表３に示すように、０．８３≦ＴＰ×ＮＡ／λを満たす場合、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１となり、良好な再生信号品質を得られることがわかる。
【００９２】
なお、本実施の形態では、本ディスクでは、ディスク基板１側からレーザ光の照射を受けることで、記録・再生が行われるとしている。しかしながら、これに限らず、本ディスクを、保護コート層３２側からのレーザ光照射によって記録・再生を行える構成とすることもできる（膜面入射方式）。
【００９３】
図６は、このような構成を有する本ディスクを示す断面図（説明図）である。この図に示すように、この構成では、ディスク基板１上に、放熱層３１，透明誘電体層３０，記録層２９，透明誘電体層２８，再生補助層２７，再生層２６，透明誘電体層２５，保護コート層３２が、この順に積層されている。
【００９４】
このように、この構成では、保護コート層３２以外の各層２５〜３１が、図３に示したディスクとは逆順に積層されている。なお、各層の材料は、図３に示したディスクと同様である。
【００９５】
この構成では、記録トラックの形成されたディスク基板１とは逆側の、保護コート層３２側にレーザ光を照射して記録再生を行うようになっている。このため、ディスク基板１の反りの影響を小さくできる。さらに、記録再生装置における対物レンズのＮＡを高くできるので、高密度化を図れる。
【００９６】
次に、図６に示した構成を有する、本ディスクにおけるウォブリング振幅量，グルーブ深さ（溝深さ）およびトラックピッチの適切な値を確認するための実験について説明する。
【００９７】
〔実験４〕
実験４では、側壁４の様々なウォブリング振幅量を有する、本ディスクにおける１１種類のサンプルを作成し、図４に示した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。
【００９８】
なお、各サンプルの層構成（層の材料など）は、実験１に示したものと同様である。また、各サンプルにおけるグルーブの幅（トラック幅）を０．２５μｍ，溝深さを５０ｎｍに設定した。また、各サンプルのウォブリング周期を一定（３５μｍ）とし、さらに、ウォブリング振幅量を０ｎｍから±１０ｎｍの範囲で変化させた。
【００９９】
また、各サンプルに対するデータの記録・再生条件は以下の通りである。
すなわち、本記録再生装置の半導体レーザ３４から照射されるレーザ光（記録および再生に用いるレーザ光）の波長を４０５ｎｍとし、さらに、対物レンズ３８のＮＡを０．９に設定した。また、レーザ光を、各サンプルに対して保護コート層３２側から入射した。
【０１００】
さらに、データの記録は、線速度３ｍ／ｓで、光パルス磁界変調記録により、最短ビット長０．１３３μｍの（１，７）ＲＬＬ変調コードで行った。そして、このように記録されたデータを再生し、データ信号およびウォブリング信号（ウォブリング再生信号）を生成して、データ信号のビットエラーレート（Ｄ−ＢＥＲ），ウォブリング信号のＣＮＲ（Ｗ−ＣＮＲ），Ｉｗ／ＩｏおよびＩｗ／Ｉｔを測定した。
【０１０１】
【表４】

【０１０２】
表４は、各サンプルのウォブリング振幅量と、Ｄ−ＢＥＲ，Ｗ−ＣＮＲ，Ｉｗ／ＩｏおよびＩｗ／Ｉｔの測定結果とを示す表である。
【０１０３】
上記したように、ウォブリング信号は、３２ｄＢ以上のＷ−ＣＮＲを有する場合に、回転制御信号および／またはアドレス信号として実用可能である。そして、３２ｄＢ以上のＷ−ＣＮＲは、表４より、ウォブリング振幅量を±２ｎｍ以上とする場合に実現できることがわかる。
【０１０４】
一方、データ信号は、１×１０^−４以下のＤ−ＢＥＲを有する場合に、再生のための信号として実用可能である。そして、１×１０^−４以下のＤ−ＢＥＲは、表１より、ウォブリング振幅量を±６ｎｍ以下とする場合に実現できることがわかる。
以上の結果から、ウォブリングの振幅量を±２ｎｍから±６ｎｍの範囲とすることが好ましいといえる。
【０１０５】
また、記録および再生に用いるレーザ光の波長（λ）を４０５ｎｍ、対物レンズ３８のＮＡを０．９としているので、この測定におけるレーザ光のスポット径変数（λ／ＮＡ）は、４５０ｎｍである。従って、スポット径変数に対する良好なウォブリング振幅量の比（Ａ×ＮＡ／λ）の範囲は、実験１で得られた値と同様に、
０．００４４≦Ａ×ＮＡ／λ≦０．０１３３となる。
【０１０６】
また、表４に示したように、３２ｄＢ以上のＷ−ＣＮＲおよび１×１０^−４以下のＤ−ＢＥＲを実現して、良好な再生信号品質を得るためには、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１であればよいことがわかる。
【０１０７】
〔実験５〕
実験５では、１０種類の溝深さ（グルーブの深さ）および様々なウォブリング振幅量を有する複数の本ディスクのサンプルを作成し、上記した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。
なお、各サンプルの層構成、および、各サンプルに対するデータの記録・再生条件は、実験４において示したものと同様である。
【０１０８】
【表５】

【０１０９】
表５は、各サンプルに対する測定において、Ｄ−ＢＥＲが１×１０^−４以下となり、かつ、Ｗ−ＣＮＲが３２ｄＢ以上となるような、ウォブリング振幅量，Ｉｗ／ＩｏおよびＩｗ／Ｉｔの範囲と、各サンプルの溝深さ（ｄ）との関係を示す表である。
また、この表５には、レーザ光の波長と光路長との比である、λ／（ｎ×ｄ）の値も示している。なお、この式のｎは、光の入射する側に位置する層の屈折率、すなわち、保護コート層３２の屈折率である。
【０１１０】
この表に示すように、表２（実験２）に示した結果と同様に、５．５≦λ／（ｎ×ｄ）≦１６を満たす場合、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１となり、良好な再生信号品質を得られることがわかる。
【０１１１】
また、様々なトラックピッチを有する複数の本ディスク（図６のタイプ）のサンプルを作成し、上記した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。また、各サンプルの層構成、および、各サンプルに対するデータの記録・再生条件は、実験４において示したものと同様とした。さらに、各サンプルのグルーブ幅およびグルーブ間距離（ランド幅）は、ほぼ等しくした。
【０１１２】
その結果、実験３で示した結果と同様に、０．８３≦ＴＰ×ＮＡ／λの範囲であれば、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１となり、良好な再生信号品質を得られることがわかった。
【０１１３】
また、本実施の形態では、本ディスクを光磁気ディスクであるとしている。しかしながら、本発明の光記録媒体は、光磁気ディスクに限定されるものではない。例えば、本発明の光記録媒体を、相変化ディスク等、他の記録方式を利用した媒体とすることもできる。このような媒体においても、実験１〜５等に示した結果と同様の実験結果を得ており、ウォブリング振幅量の好ましい範囲は、光磁気ディスクと同様であることがわかっている。
なお、相変化ディスクは、外部磁界を印加することなく、レーザ光のみでデータ記録（書き換え）を行えるものである。
【０１１４】
以下に、相変化ディスクからなる本ディスクについて説明する。図７は、相変化ディスクからなる本ディスクの構成を示す断面図（説明図）である。
この図に示すように、この構成では、ディスク基板１上に、反射層４４，透明誘電体層４５，記録層４６，透明誘電体層４７，透明カバー層４８が、この順に積層されている。
【０１１５】
透明誘電体層４５・４７は、ＺｎＳ−ＳｉＯ_２、Ａｌ_２Ｏ_３、ＳｉＯ_２等の材料からなり、１層ないし２層で構成されている。反射層４４は、ＡｌあるいはＡｌを含む合金膜からなるものである。
透明カバー層４８は、紫外線硬化樹脂あるいはプラスチックシートからなる。記録層４６は、ＧｅＳｂＴｅ、ＡｇＩｎＳｂＴｅ等の相変化記録材料により構成されている。
【０１１６】
この構成では、記録トラックの形成されたディスク基板１とは逆側の、透明カバー層４８側にレーザ光を照射して記録再生を行うようになっている。このため、ディスク基板１の反りの影響を小さくできる。さらに、記録再生装置における対物レンズのＮＡを高くできるので、高密度化を図れる。
また、透明カバー層４８を設けているので、ディスクの耐環境性を向上でき、信頼性にも優れている。
【０１１７】
ここで、図７に示した構成を有する、相変化型の本ディスクにおけるウォブリング振幅量，グルーブ深さ（溝深さ）およびトラックピッチの適切な値を確認するための実験について説明する。
【０１１８】
〔実験６〕
実験６では、側壁４の様々なウォブリング振幅量を有する、本ディスクにおける１１種類のサンプルを作成し、図４に示した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。
【０１１９】
なお、各サンプルにおけるグルーブの幅（トラック幅）を０．２６μｍ、溝深さを３５ｎｍに設定した。また、各サンプルのウォブリング周期を一定（３５μｍ）とし、さらに、ウォブリング振幅量を０ｎｍから±１０ｎｍの範囲で変化させた。
【０１２０】
また、各サンプルに対するデータの記録・再生条件は以下の通りである。
すなわち、本記録再生装置の半導体レーザ３４から照射されるレーザ光（記録および再生に用いるレーザ光）の波長を４０５ｎｍとし、さらに、対物レンズ３８のＮＡを０．８５に設定した。また、レーザ光を、各サンプルに対して透明カバー層４８側から入射した。
【０１２１】
さらに、データの記録は、線速度３ｍ／ｓで、最短ビット長０．１３３μｍの（１，７）ＲＬＬ変調コードで行った。そして、このように記録されたデータを再生し、データ信号およびウォブリング信号を生成して、データ信号のビットエラーレート（Ｄ−ＢＥＲ），ウォブリング信号のＣＮＲ（Ｗ−ＣＮＲ），Ｉｗ／ＩｏおよびＩｗ／Ｉｔを測定した。
【０１２２】
【表６】

【０１２３】
表６は、各サンプルのウォブリング振幅量と、Ｄ−ＢＥＲ，Ｗ−ＣＮＲ，Ｉｗ／ＩｏおよびＩｗ／Ｉｔの測定結果とを示す表である。
【０１２４】
上記したように、ウォブリング信号は、３２ｄＢ以上のＷ−ＣＮＲを有する場合に、回転制御信号および／またはアドレス信号として実用可能である。そして、３２ｄＢ以上のＷ−ＣＮＲは、表６より、ウォブリング振幅量を±２ｎｍ以上とする場合に実現できることがわかる。
【０１２５】
一方、データ信号は、１×１０^−４以下のＤ−ＢＥＲを有する場合に、再生のための信号として実用可能である。そして、１×１０^−４以下のＤ−ＢＥＲは、表１より、ウォブリング振幅量を±６ｎｍ以下とする場合に実現できることがわかる。
【０１２６】
以上の結果から、図７に示したタイプの本ディスクにおいても、ウォブリングの振幅量を±２ｎｍから±６ｎｍの範囲とすることが好ましいといえる。
【０１２７】
また、記録および再生に用いるレーザ光の波長（λ）を４０５ｎｍ、対物レンズ３８のＮＡを０．８５としているので、この測定におけるレーザ光のスポット径変数（λ／ＮＡ）は、約４７６ｎｍである。従って、スポット径変数に対する良好なウォブリング振幅量の比（Ａ×ＮＡ／λ）の範囲は、０．００４２≦Ａ×ＮＡ／λ≦０．０１２６となる。
【０１２８】
また、表６に示したように、３２ｄＢ以上のＷ−ＣＮＲおよび１×１０^−４以下のＤ−ＢＥＲを実現して、良好な再生信号品質を得るためには、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１であればよいことがわかる。
【０１２９】
また、図７に示した本ディスクに関し、溝深さおよびウォブリング振幅量を変化させたサンプルを作成し、上記した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。なお、各サンプルの層構成、および、各サンプルに対するデータの記録・再生条件は、上記と同様である。
【０１３０】
この実験の結果、表２（実験２）で示した結果と同様に、５．５≦λ／（ｎ×ｄ）≦１６を満たす場合、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１となり、良好な再生信号品質を得られることがわかった（ｎは透明カバー層４８の屈折率）。
【０１３１】
また、様々なトラックピッチを有する複数の本ディスク（図７のタイプ）のサンプルを作成し、上記した本記録再生装置を用いてデータを記録した後、ウォブリング信号（アドレス信号）およびデータ信号の再生信号品質を測定した。また、各サンプルの層構成、および、各サンプルに対するデータの記録・再生条件は、上記と同様とした。さらに、各サンプルのグルーブ幅およびグルーブ間距離（ランド幅）は、ほぼ等しくした。
【０１３２】
その結果、実験３で示した結果と同様に、０．８３≦ＴＰ×ＮＡ／λの範囲であれば、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１となり、良好な再生信号品質を得られることがわかった。
【０１３３】
次に、図１・２に示した本ディスクのディスク基板１における製造方法（製造プロセス）について説明する。
【０１３４】
ディスク基板１の製造では、まず、ディスク基板１の基になるマスターガラス原盤を作成する。そして、このマスターガラス原盤からスタンパー２４を作成し、このスタンパー２４を用いた成型により、ディスク基板１を形成するようになっている。
【０１３５】
まず、マスターガラス原盤の製造プロセスについて説明する。図８（ａ）〜（ｅ）は、このマスターガラス原盤の製造プロセスを示す説明図である。
【０１３６】
マスターガラス原盤の製造では、まず、図８（ａ）に示すように、ガラス原盤５１の片面に、フォトレジスト７を塗布する。
次に、図８（ｂ）に示すように、対物レンズ８によってレーザ光をフォトレジスト７上に集光し、フォトレジスト７を、所望のグルーブパターン（本ディスクのグルーブ２に応じたパターン）に応じて感光させる。
【０１３７】
その後、図８（ｃ）に示すように、フォトレジスト７を現像することにより、フォトレジスト７の感光部分を除去する。これにより、フォトレジスト７の除去された部位により、上記のグルーブパターンが形成される。
【０１３８】
次に、図８（ｄ）に示すように、フォトレジスト７をマスクとして、ドライエッチングもしくはウエットエッチングにより、ガラス原盤５１をエッチングする。これにより、ガラス原盤５１の表面に、上記した所望のグルーブパターンが形成される。
その後、図８（ｅ）に示すように、残ったフォトレジスト７を、アッシング等により除去する。これにより、マスターガラス原盤９が完成する。
【０１３９】
次に、マスターガラス原盤９から成形基板を製造するプロセスについて説明する。図９（ａ）〜（ｅ）は、このプロセスを説明するための説明図である。
まず、図９（ａ）に示すように、マスターガラス原盤９に、導電性の薄膜２２を、スパッタあるいは無電解メッキなどによって形成する。
【０１４０】
次に、図９（ｂ）に示すように、薄膜２２上に、金属層２３を電鋳などによって形成する。その後、図９（ｃ）に示すように、薄膜２２・金属層２３を、マスターガラス原盤９から剥離する。
【０１４１】
そして、図９（ｄ）に示すように、薄膜２２・金属層２３に対し、裏面研磨，内外径加工を行い、スタンパー２４を形成する。次に、図９（ｅ）に示すように、スタンパー２４を用いた射出成型もしくは射出圧縮成型により、プラスチックからなるディスク基板１を形成する。
【０１４２】
なお、薄膜２２の材料としては、Ｎｉ，Ｔａ，Ｃｒまたはその合金、あるいはそれらの複合膜を用いることが可能である。また、金属層２３の材料としては、Ｎｉ，Ｔａ，Ｃｒまたはその合金、あるいはそれらの複合膜を使用できる。
また、ディスク基板１のプラスチック材料としては、ポリカーボネート樹脂，アクリル樹脂，エチレン樹脂，エステル樹脂，ナイロン樹脂，ＡＰＯ（活性ポリオレフィン樹脂）などの熱可塑性樹脂を使用できる。
【０１４３】
また、スタンパー２４の製造方法は、マスターガラス原盤９を用いる方法に限らない。例えば、レジスト原盤を作成して、このレジスト原盤を用いてスタンパー２４を製造してもよい。また、図９（ａ）〜（ｄ）の工程を２回繰り返すことにより、凹凸を逆転させたスタンパーを形成できる。
【０１４４】
また、ディスク基板１のグルーブ深さ（ランド高さ）は、マスターガラス原盤９の製造プロセスにおける、図８（ｄ）に示したエッチングの条件を変えることにより制御できる。また、グルーブおよびランドの両方を記録トラック（情報トラック）として用いる場合、グルーブ深さ（ランド高さ）を、λ／（６×ｎ）の近傍とすることが好ましい。この構成では、記録信号に関する記録トラック間のクロストーク（隣接トラックからの回り込みノイズ）を低減でき、高密度化に適している。
【０１４５】
また、図８（ａ）〜（ｅ）を用いて、マスターガラス原盤９の製造方法を示したが、ここで、マスターガラス原盤９の製造に使用される、フォトレジスト７を感光させる装置（感光装置）について説明する。
【０１４６】
図１０は、この感光装置の構成を示す説明図である。この図に示すように、感光装置は、レーザ光源１０ａ，レーザ光源１０ｂ，ノイズ抑制装置１１，ミラー１２，光変調器１３，ミラー１４，光偏向器１５，ビームエキスパンダー１６，ハーフミラー１７・１８，対物レンズ１９，シリンドリカルレンズ２０，光検出器２１を備えている。
【０１４７】
レーザ光源１０ａは、フォトレジスト７を感光させるために照射されるレーザ光（感光レーザ光）を発する光源である。このレーザ光源１０ａとしては、例えば、Ｋｒレーザ光源を用いることが可能である。
【０１４８】
ノイズ抑制装置１１は、レーザ光源１０ａから出射されて自身を通過する感光レーザ光の光ノイズを低減させるものである。ミラー１２は、ノイズの低減された感光レーザ光の進行方向を光変調器１３に向けるものである。
【０１４９】
光変調器１３は、自身を通過する感光レーザ光に所定の変調を加えるものである。ミラー１４は、光変調器１３を通過した感光レーザ光の進行方向を光偏向器１５に向けるものである。光偏向器１５は、自身を通過する感光レーザ光に所定の偏向を加えるものである。
なお、光変調器１３および光偏向器１５としては、例えば、電気光学素子を用いることができる。
【０１５０】
ビームエキスパンダー１６は、光偏向器１５を通過した感光レーザ光のビーム径を適切な大きさに拡大するものである。ハーフミラー１７は、ビーム径の拡大された感光レーザ光の進行方向を、対物レンズ８に向けるものである。また、ハーフミラー１７は、対物レンズ８を通過したフォーカスレーザ光（後述）を透過させる機能も有している。
対物レンズ８は、ハーフミラー１７からの感光レーザ光、あるいは、後述するハーフミラー１８からのフォーカスレーザ光を、ガラス原盤５１上のフォトレジスト７に集光させるものである。
【０１５１】
また、レーザ光源１０ｂは、対物レンズ８のフォーカス調整用に使用されるレーザ光（フォーカスレーザ光）のための光源である。このレーザ光源１０ｂとしては、例えば、Ｈｅ−Ｎｅレーザ光を使用できる。
【０１５２】
ハーフミラー１８は、レーザ光源１０ｂから出射されたフォーカスレーザ光の進行方向を対物レンズ８に向けるものである。
【０１５３】
また、対物レンズ８によってガラス原盤５１上のフォトレジスト７に集光・反射されたフォーカスレーザ光は、対物レンズ８，ハーフミラー１８を通過して、対物レンズ１９・シリンドリカルレンズ２０に向かう。これらの対物レンズ１９・シリンドリカルレンズ２０は、自身を通過するフォーカスレーザ光を、光検出器２１に集光させるものである。
【０１５４】
光検出器２１は、自身に集光されたフォーカスレーザ光の状態に応じた駆動信号を、フォーカスサーボ系（図示せず）に出力するものである。フォーカスサーボ径は、駆動信号に基づいて、対物レンズ８をフォーカス方向に駆動する。これにより、スピンドルモータで回転しているガラス原盤５１上のフォトレジスト７に、対物レンズ８の焦点が合わされる。
【０１５５】
なお、この感光装置では、光偏向器１５により、アドレス情報に応じて、感光レーザ光のスポット位置を、ガラス原盤５１の半径方向に変化させるようになっている。これにより、所望のグルーブパターンに応じて、フォトレジスト７の感光部分をウォブリングさせることが可能となる。
【０１５６】
また、本実施の形態では、図８（ａ）〜（ｅ）を用いて、マスターガラス原盤９の製造方法を示した。しかしながら、マスターガラス原盤９の製造方法はこの方法に限らない。例えば、所望のパターンの形成されたマスク原盤を作成し、このマスク原盤を用いて、密着露光法によりマスターガラス原盤９を製造してもよい。
【０１５７】
また、本実施の形態では、記録および再生に用いるレーザ光の波長を同一としている。しかしながら、これに限らず、記録レーザ光と再生レーザ光との波長を変えるようにしてもよい。
また、この場合、本ディスクのウォブリング振幅量に関する（Ａ×ＮＡ／λ）の範囲は、再生レーザ光あるいは記録レーザ光のいずれかの波長に合わせて、０．００４４≦Ａ×ＮＡ／λ≦０．０１３３（相変化型の場合は０．００４２≦Ａ×ＮＡ／λ≦０．０１２６）を満たすように設定されることが好ましい。
【０１５８】
また、同様に、本ディスクの溝深さ（ｄ）およびトラックピッチ（ＴＰ）の範囲も、再生レーザ光あるいは記録レーザ光のいずれかの波長に合わせて、５．５≦λ／（ｎ×ｄ）≦１６、０．８３≦ＴＰ×ＮＡ／λを満たすように設定されることが好ましい。
【０１５９】
また、本実施の形態では、ディスク基板１のグルーブ２が螺旋状であるとしている。しかしながら、ディスク基板１では、グルーブ２を同心円状に形成してもよい。
【０１６０】
また、本実施の形態では、ディスク基板１のグルーブ２における側壁４を、アドレス情報に応じてウォブリング（蛇行）させているとしている。しかしながら、この側壁４を、回転制御情報（クロック情報）に応じてウォブリングさせるようにしてもよい。これにより、ウォブリング信号に基づいて、回転制御信号（クロック信号）を得ることができる。また、側壁４のウォブリングを、アドレス情報およびクロック情報の双方に応じたものとすることで、ウォブリング信号から、アドレス信号およびクロック信号の双方を得られる。
【０１６１】
また、側壁４を、クロック信号とは異なる回転制御情報に応じてウォブリングさせてもよい。これにより、ウォブリング信号に基づいて、上記の回転制御信号を得ることができる。
【０１６２】
また、側壁４のウォブリングを、アドレス情報，クロック情報および回転制御情報の全てに応じたものとすることで、ウォブリング信号から、アドレス信号，クロック信号および回転制御信号の３つの信号を得られる。
【０１６３】
また、本実施の形態では、本ディスクを再生する際、プッシュプル法によってトラックエラー信号を得るとしている。しかしながら、これに限らず、トラックエラー信号を、他の方法によって取得するようにしてもよい。
【０１６４】
また、本実施の形態では、グルーブ２を記録トラックとするとしている。しかしながら、これに限らず、ランド３のみを記録トラックとしてもよい。また、グルーブ２とランド３との双方を記録トラックとして用いてもよい。
光スポット５をグルーブ２に追従させるか、ランド３に追従させるかは、トラックエラー信号の極性を反転させることによって容易に選択できる。
【０１６５】
また、本実施の形態では、図４に示した本記録再生装置の光学ヘッド４１を、磁気光学効果を利用した光磁気ディスク用の光学ヘッドであるとしている。しかしながら、本記録再生装置には、他の方式を用いた光記録媒体用の光学ヘッドを搭載することも可能である。
【０１６６】
また、本実施の形態では、図４に示した本記録再生装置の受光部４０を、２分割された構成であるとしている。しかしながら、これに限らず、受光部４０を、３つ以上に分割してもよい。すなわち、受光部４０は、複数の領域に分割されていることが好ましい。
【０１６７】
また、本ディスクからの反射光を光電変換して得られる電気信号は、「媒体に記録されたデータに応じた信号（データ信号）とトラックエラー信号（プッシュプル信号）とに分けられる。また、上記のデータ信号は、記録情報信号，記録信号，記録情報の再生信号と表現することもできる。さらに、ウォブリング信号は、トラックエラー信号から取り出されるウォブリング周波数成分に応じた信号であり、ウォブリング再生信号，トラックのウォブリングからの再生信号と表現することもできる。また、ウォブリング信号から、回転制御情報の再生信号、アドレス情報の再生信号およびクロック信号を得ることが可能である。
【０１６８】
また、本実施の形態では、Ａ×ＮＡ／λを、スポット径変数（λ／ＮＡ）に対する良好なウォブリング振幅量の比であるとしている。ここで、光スポット径∝λ／ＮＡであることから、Ａ×ＮＡ／λは、光スポット径に対するウォブリング振幅量の比の定数倍であるということもできる。
【０１６９】
また、本実施の形態では、本発明の光記録媒体を、光磁気ディスクあるいは相変化型の光ディスクであるとしている。しかしながら、本発明の光記録媒体は、ディスク形状である必要はなく、どのような形状を有していてもよい。
【０１７０】
また、本実施の形態では、屈折率として、ディスク基板１あるいは保護コート層３２の屈折率を用いている。
しかしながら、これに限らず、屈折率ｎとしては、レーザ光の照射を受ける表面から、記録層（あるいは再生層）に到達するまでの部位における、平均の屈折率を用いてもよい。また、屈折率ｎとして、ディスク基板１あるいは保護コート層３２のように、上記の部位のなかで最も支配的な（厚い）層の屈折率を採用することもできる。
【０１７１】
また、本発明の光記録媒体を、光記録再生装置において記録レーザ光（あるいは記録レーザ光および磁場）によってデータを記録される一方、再生レーザ光によってデータ再生の行われる光記録媒体であって、付帯情報に応じた周波数でウォブリングされたグルーブを備えた光記録媒体において、上記光記録再生装置における対物レンズの開口数をＮＡ，記録レーザ光の波長をλとする場合、上記グルーブにおけるウォブリング振幅量の絶対値Ａが、．００４２≦Ａ×ＮＡ／λ≦０．０１２６（あるいは０．００４４≦Ａ×ＮＡ／λ≦０．０１３３）を満たす構成である、と表現することもできる。
【０１７２】
また、通常、光記録媒体における記録トラックのウォブリングの振幅量は、ウォブリング再生信号の信号品質より最適化されているといえる。また、光記録媒体の高密度化が要求され、レーザの短波長化、対物レンズの高ＮＡ化、磁気的超解像媒体の開発等により、情報トラックの狭トラックピッチ化や記録情報信号の狭小化が進み、情報トラックのウォブリングの記録情報の再生信号への影響が大きくなり、従来のウォブリング振幅量では情報再生信号が劣化するという問題が生じているといえる。また、狭トラックピッチ化に伴い、ウォブリング振幅量も小さくなり、基板製造時に、物理量だけでの制御が難しくなってきているともいえる。
【０１７３】
また、図３に示した光ディスクは、次のように再生することもできる。すなわち、再生層２６に光ビームが照射されると、照射された部位の温度分布はガウス分布になるので、光ビームの径より小さい領域のみの温度が上昇する。この温度上昇に伴って、温度上昇部位の磁化は、面内磁化から垂直磁化に移行する。つまり、再生層２６と記録層２９の２層間の静磁結合により、記録層２９の磁化の向きが再生層２６に転写される。温度上昇部位が面内磁化から垂直磁化に移行すると、温度上昇部位のみが磁気光学効果を示すようになり、温度上昇部位からの反射光に基づいて記録層２９に記録された情報が再生される。そして、光ビームが移動して次の記録ビットを再生するときは、先の再生部位の温度は低下し、垂直磁化から面内磁化に移行する。これに伴って、この温度の低下した部位は磁気光学効果を示さなくなり、記録層２９に記録された磁化は再生層２６の面内磁化にマスクされて再生されなくなる。これにより、雑音の原因である隣接ビットからの信号が混入することがなくなる。このように、所定温度以上の温度を有する領域のみを再生に関与させるので、光ビームの径より小さい記録ビットの再生が行え、記録密度は著しく向上することになる。
【０１７４】
また、差動増幅器４３では、第１受光素子４２ａからの電気信号と第２受光素子４２ｂからの電気信号とから差動信号を演算し、この差動信号により、トラックのウォブリング信号から、回転制御信号（ウォブリングがクロック情報に応じている場合）および／またはアドレス信号が生成されるともいえる。
【０１７５】
また、図４に示した光学ヘッド４１は、磁気光学効果を利用した光磁気ディスク用の光学ヘッドについて示しているが、他の方式による記録可能なディスクに対しても本発明による光記録再生装置は適用可能である。さらに、図４あるいは図５に示す光記録再生装置において、図には明示していないが、光ディスクに記録された信号の再生、およびサーボ信号の生成機能および処理機能が装置に付加されていることはいうまでもない。
【０１７６】
また、図１０に示した装置を、フォトレジスト７をグルーブ２のパターンに感光させる装置と表現することもできる。また、この装置の構成を、以下のように表現することもできる。すなわち、この装置は、フォトレジスト７を感光させるためのレーザ光源１０ａと、対物レンズ８のフォーカス用レーザ光源１０ｂを備えており、レーザ光源１０ａには、例えばＫｒレーザが使用され、レーザ光源１０ｂには、例えばＨｅ−Ｎｅレーザが使用される。レーザ光源１０ａからのレーザ光は、ノイズ抑制装置１１により光ノイズを低減した後、ミラー１２で反射され、光変調器１３に入射する。光変調器１３を通ったレーザ光は、ミラー１４で反射され、光偏向器１５に入射する。光変調器１３および光偏向器１５としては、例えば電気光学素子を用いることができる。光偏向器１５を通ったレーザ光はビームエキスパンダー１６によって適当なビーム径に拡大された後、ハーフミラー１７によって対物レンズ８に入射する。そして対物レンズ８によってガラス原盤５１上のフォトレジスト７に集光される。
【０１７７】
一方、レーザ光源１０ｂからのレーザ光は、ハーフミラー１８で反射され、対物レンズ８によってガラス原盤５１上のフォトレジスト７に集光される。その反射光は、対物レンズ８、ハーフミラー１８を通り、対物レンズ１９及びシリンドリカルレンズ２０によって光検出器２１に集光される。光検出器２１からの信号に基づいて、フォーカスサーボ系が対物レンズ８をフォーカス方向に駆動し、スピンドルモータで回転しているガラス原盤５１上のフォトレジスト７に対物レンズ８の焦点が合わされる。上記の構成において、光偏向器１５により、回転制御情報および／またはアドレス情報に応じてレーザスポットを半径方向に変化させることにより、グルーブが所望のパターンにウォブリングされる。
【０１７８】
また、表２は、それぞれの溝深さにおいて、Ｗ−ＣＮＲが３２ｄＢ以上且つ、Ｄ−ＢＥＲが１×１０^−４となる、ウォブリング振幅量、Ｉｗ／ＩｏおよびＩｗ／Ｉｔの範囲を示したものであるともいえる。
【０１７９】
また、表３は、溝および溝間の幅がほぼ等しくトラックピッチを変えたサンプルを作製し、それぞれのトラックピッチにおいて、Ｗ−ＣＮＲが３２ｄＢ以上且つ、Ｄ−ＢＥＲが１×１０^−４以下となる、ウォブリング振幅量、Ｉｗ／ＩｏおよびＩｗ／Ｉｔの範囲を示したものであるともいえる。
また、λは記録レーザの波長、ｎはトラックの光入射側の屈折率（基板入射方式の場合はディスク基板１の屈折率、膜面入射方式の場合は、空気もしくはカバー層等の屈折率）であってもよい。
【０１８０】
また、本発明は、以下の第４〜第１０光記録媒体、および、第１・第２光記録再生装置として表現することもできる。すなわち、第４光記録媒体は、データを記録するトラックを有し、前記トラックが回転制御情報および／またはアドレス情報に対応して変調された信号でウォブリングされた光記録媒体において、前記トラックのウォブリング振幅量±Ａが、０．００４４≦Ａ×ＮＡ／λ≦０．０１３３の範囲（ＮＡ：対物レンズの開口数、λ：記録レーザ波長）である構成である。この構成によれば、回転制御情報および／またはアドレス情報の再生信号品質を確保し、且つ、記録情報の再生信号への影響を抑制できる。
また、『前記トラックが回転制御情報および／またはアドレス情報に対応して変調された信号でウォブリングされた光記録媒体』とは、「回転制御情報および／またはアドレス情報に対応してウォブリングされた光記録媒体」と表現することもできる。
【０１８１】
また、第５光記録媒体は、データを記録するトラックを有し、前記トラックが回転制御情報および／またはアドレス情報に対応して変調された信号でウォブリングされた光記録媒体において、前記トラックのウォブリングからの再生信号量Ｉｗが、Ｉｗ／Ｉｏ≧０．０１０、且つ、Ｉｗ／Ｉｔ≦０．０７１の範囲（Ｉｏ：光記録媒体の平坦部からの反射光量、Ｉｔ：オフトラック時のトラックエラー信号量）である構成である。この構成によれば、制御情報および／またはアドレス情報の再生信号品質を確保し、且つ、記録情報の再生信号への影響を抑制でき、基板製造時のウォブリング振幅量の制御が容易となる。
【０１８２】
また、第６光記録媒体は、第４あるいは第５光記録媒体において、トラックの深さｄが、５．５≦λ／（ｎ×ｄ）≦１６の範囲である構成である。この構成によれば、ウォブリングの振幅量の調整により、回転制御情報および／またはアドレス情報の再生信号品質を確保し、且つ、記録情報の再生信号への影響を抑制できる。
【０１８３】
また、第７光記録媒体は、第４〜６光記録媒体のいずれかにおいて、少なくとも光磁気記録層が形成されている構成である。この構成によれば、１００万回以上書き換えが可能な光記録媒体を提供できる。
【０１８４】
また、第８光記録媒体は、第４〜６光記録媒体のいずれかにおいて、少なくとも相変化記録層が形成されている構成である。この構成によれば、レーザ光のみで書き換えが可能な光記録媒体を提供できる。
【０１８５】
また、第９光記録媒体は、第４〜６光記録媒体のいずれかにおいて、少なくとも磁気的超解像光磁気記録再生層が形成されている構成である。この構成によれば、光スポット径よりも小さいビットの再生ができるようになり、高密度化が可能になる。
【０１８６】
また、第１０光記録媒体は、第４〜６の光記録媒体のいずれかにおいて、トラックが形成された基板に対して反対側から記録再生を行う構成である。この構成によれば、対物レンズのＮＡを高くでき、高密度化が可能になる。
【０１８７】
また、第１光記録再生装置は、データを記録するトラックを有し、前記トラックが回転制御情報および／またはアドレス情報に対応して変調された信号でウォブリングされ、前記トラックのウォブリング振幅量±Ａが、０．００４４≦Ａ×ＮＡ／λ≦０．０１３３の範囲である光記録媒体に対して、情報の記録再生を行う光記録再生装置であって、前記光記録媒体に光を照射し、前記光記録媒体より反射された光を１対の受光部により受光して電気信号に変換する光学ヘッドを有し、前記電気信号の差動をとったプッシュプル信号に基づいて、回転制御情報および／またはアドレス情報を再生する構成である。この構成によれば、高密度な記録情報信号と回転制御信号および／またはアドレス信号の再生が可能である。
【０１８８】
た、第２光記録再生装置は、データを記録するトラックを有し、前記トラックが回転制御情報および／またはアドレス情報に対応して変調された信号でウォブリングされ、前記トラックのウォブリングからの再生信号量Ｉｗが、Ｉｗ／Ｉｏ≧０．０１０、且つ、Ｉｗ／Ｉｔ≦０．０７１の範囲である光記録媒体に対して、情報の記録再生を行う光記録再生装置であって、前記光記録媒体に光を照射し、前記光記録媒体より反射された光を１対の受光部により受光して電気信号に変換する光学ヘッドを有し、前記電気信号の差動をとったプッシュプル信号に基づいて、回転制御情報および／またはアドレス情報を再生する構成である。この構成によれば、高密度な記録情報信号と回転制御信号および／またはアドレス信号の再生が可能である。
【０１８９】
【発明の効果】
以上のように、本発明における第１の光記録媒体（第１光記録媒体）は、光記録再生装置において記録レーザ光および磁場によってデータを記録される一方、再生レーザ光によってデータ再生の行われる光記録媒体であって、付帯情報に応じてウォブリングされたグルーブを備えた光記録媒体において、上記光記録再生装置における対物レンズの開口数をＮＡ，記録レーザ光の波長をλとする場合、上記グルーブにおけるウォブリング振幅量の絶対値Ａが、
０．００４４≦Ａ×ＮＡ／λ≦０．０１３３
を満たす構成である。
【０１９０】
また、本発明における第２の光記録媒体（第２光記録媒体）は、光記録再生装置において記録レーザ光によってデータを記録される一方、再生レーザ光によってデータ再生の行われる光記録媒体であって、付帯情報に応じてウォブリングされたグルーブを備えた光記録媒体において、上記光記録再生装置における対物レンズの開口数をＮＡ，上記記録レーザ光の波長をλとする場合、上記グルーブにおけるウォブリング振幅量の絶対値Ａが、
０．００４２≦Ａ×ＮＡ／λ≦０．０１２６
を満たす構成である。
【０１９１】
これら第１・第２光記録媒体では、グルーブにおけるウォブリングの振幅量が、付帯情報の再生信号品質を好適に確保できる範囲であって、ウォブリングの影響を回避してデータの記録・再生を良好に行える範囲（実験によって求められた範囲）に設定されている。
【０１９２】
すなわち、光記録再生装置における対物レンズの開口数をＮＡ，記録レーザ光の波長をλとする場合、グルーブにおけるウォブリング振幅量の絶対値Ａが、第１光記録媒体の場合に０．００４４≦Ａ×ＮＡ／λ≦０．０１３３を、第２光記録媒体の場合に０．００４２≦Ａ×ＮＡ／λ≦０．０１２６を満たすように設定されている。
これにより、第１・第２光記録媒体では、付帯情報の再生信号品質、および、データの記録・再生品質の双方を高められるようになっている。
【０１９３】
また、第１記録媒体を、データ（ユーザーによって記録された情報）に応じた磁化を有する記録層（データを磁気的に記録する記録層）と、再生レーザ光の照射によって高温となった領域で記録層の磁化を転写する再生層とを備えるように構成してもよい。すなわち、第１記録媒体を、磁気的超解像光磁気記録媒体としてもよい。
【０１９４】
この構成では、再生層の高温領域を再生に関与させる一方、その他の領域（低温領域）をマスクとして用いることができる。これにより、記録層の記録ビット（磁区）を、再生レーザ光のスポット径より小さくできるので、データの記録密度を著しく向上できる。また、低温領域のマスクによって、雑音の原因である隣接ビットからの信号混入を回避できる。
【０１９５】
また、本発明における第３の光記録媒体（第３光記録媒体）は、光記録再生装置において記録レーザ光および磁場、あるいは記録レーザ光によってデータを記録される一方、再生レーザ光によってデータ再生の行われる光記録媒体であって、付帯情報に応じてウォブリングされたグルーブを備えた光記録媒体において、この媒体を再生することによって得られるトラックエラー信号におけるウォブリング信号量（Ｉｗ）と、平坦部分からの反射光に応じた電気信号量（Ｉｏ）との比（Ｉｗ／Ｉｏ）、および、上記ウォブリング信号量（Ｉｗ）と、オフトラック時のトラックエラー信号量（Ｉｔ）との比（Ｉｗ／Ｉｔ）が、Ｉｗ／Ｉｏ≧０．０１０、かつ、Ｉｗ／Ｉｔ≦０．０７１を満たす構成である。
【０１９６】
第３光記録媒体では、この媒体を再生することによって得られるトラックエラー信号におけるウォブリング信号量が、付帯情報の再生信号品質を好適に確保できる範囲であって、ウォブリングの影響を回避してデータの記録・再生を良好に行える範囲（実験によって求められた範囲）に設定されている。
【０１９７】
すなわち、第３光記録媒体では、トラックエラー信号におけるウォブリング信号量（Ｉｗ）と、平坦部分（グルーブのない部分；ランドなど）からの反射光に応じた電気信号量（Ｉｏ）との比（Ｉｗ／Ｉｏ）が、Ｉｗ／Ｉｏ≧０．０１０を満たすようになっている。
さらに、第３光記録媒体では、ウォブリング信号量（Ｉｗ）と、オフトラック時のトラックエラー信号量（Ｉｔ）との比（Ｉｗ／Ｉｔ）が、Ｉｗ／Ｉｔ≦０．０７１を満たすように設定されている。
これにより、第３光記録媒体では、付帯情報の再生信号品質、および、データの記録・再生品質の双方を高められるようになっている。
【０１９８】
また、第３記録媒体が、レーザ光および磁界によってデータ記録の行われるタイプである場合には、この媒体を、第１光記録媒体と同様に、データに応じた磁化を有する記録層と、再生レーザ光の照射によって高温となった領域で記録層の磁化を転写する再生層とを備えるように構成してもよい。すなわち、第３記録媒体を、磁気的超解像光磁気記録媒体としてもよい。
【０１９９】
また、第１〜第３光記録媒体は、通常、基板と、この基板上に形成された積層体とから構成される。ここで、積層体とは、記録・再生に有効な複数種類の層の積層されたものである。また、この構成は、記録レーザ光の入射を、基板側ではなく、積層体側から受けるようになっていることが好ましい。
これにより、光記録再生装置における対物レンズのＮＡを高められるので、データを高密度で記録できる。
【０２００】
また、第１〜第３光記録媒体における記録レーザ光の入射部位の屈折率ｎと、上記グルーブの深さｄとを、
５．５≦λ／（ｎ×ｄ）≦１６
を満たすように構成することが好ましい。
【０２０１】
屈折率ｎおよびグルーブ深さ（溝深さ）ｄを上記の範囲に設定することで、付帯情報の再生信号品質をより好適に確保できるとともに、データの記録・再生をより良好に行えることが実験で確かめられている。
【０２０２】
なお、上記したように、通常、光記録媒体は、基板と、その上に形成される積層体（複数の層からなるもの）とから構成される。そして、上記した記録レーザの入射部位とは、記録レーザ光の照射を受ける表面から、積層体における記録層（データを記録するための層）に到達するまでの部位のことである。
また、入射部位の屈折率は、この部位に複数の層のある場合には、それら複数の層における平均の屈折率となる。また、入射部位の屈折率として、入射部位のなかで最も支配的な（厚い）層の屈折率を採用することもできる。
【０２０３】
また、光記録再生装置を、第１〜第３光記録媒体のいずれかを備え、これに対してデータの記録・再生を行うように構成することで、付帯情報の再生信号品質をより好適に確保できるとともに、データの記録・再生をより良好に行うことの可能な光記録再生装置を提供できる。
【図面の簡単な説明】
【図１】本発明の一実施形態にかかる光磁気ディスクのディスク基板を示す平面図である。
【図２】図１に示したディスク基板の断面図である。
【図３】上記光磁気ディスクの構成を示す断面図である。
【図４】本発明の一実施形態にかかる光記録再生装置の構成を示す説明図である。
【図５】図４に示した光記録再生装置における受光部の構成を示す説明図である。
【図６】本発明の一実施形態にかかる他の光磁気ディスクの構成を示す断面図である。
【図７】本発明の一実施形態にかかるさらに他の光磁気ディスクの構成を示す断面図である。
【図８】図１に示したディスク基板を製造するために用いるマスターガラス原盤の製造プロセスを示す説明図である。
【図９】上記マスターガラス原盤から成形基板を製造するプロセスを示す説明図である。
【図１０】上記マスターガラス原盤の製造に使用される、フォトレジストを感光させる感光装置の構成を示す説明図である。
【図１１】従来の光記録媒体の構成を示す説明図である。
【符号の説明】
１　　　ディスク基板
２　　　グルーブ
３　　　ランド
４　　　側壁
５　　　光スポット
６　　　中心線
７　　　フォトレジスト
８　　　対物レンズ
９　　　マスターガラス原盤
１０ａ　レーザ光源
１０ｂ　フォーカス用レーザ光源
１１　　ノイズ抑制装置
１２　　ミラー
１３　　光変調器
１４　　ミラー
１５　　光偏向器
１６　　ビームエキスパンダー
１７　　ハーフミラー
１８　　ハーフミラー
１９　　対物レンズ
２０　　シリンドリカルレンズ
２１　　光検出器
２２　　薄膜
２３　　金属層
２４　　スタンパー
２５　　透明誘電体層
２６　　再生層
２７　　再生補助層
２８　　透明誘電体層
２９　　記録層
３０　　透明誘電体層
３１　　放熱層
３２　　保護コート層
３３　　ディスク
３４　　半導体レーザ
３５　　コリメータレンズ
３６　　偏光子
３７　　光分岐素子
３８　　対物レンズ
３９　　検光子
４０　　受光部
４１　　光学ヘッド
４３　　差動増幅器
４４　　反射層
４５　　透明誘電体層
４６　　記録層
４７　　透明誘電体層
４８　　透明カバー層
４９　　記録トラック
Ａ　　　ウォブリング振幅量
λ　　　レーザ光の波長
ｎ　　　屈折率
ｄ　　　グルーブ深さ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium having grooves wobbled in accordance with supplementary information such as address information.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an optical recording medium, a read-only medium such as a compact disk or a DVD, in which a pit array is formed in advance on a substrate, or a magneto-optical disk (a mini disk or the like) or a phase change disk (DVD-RAM or the like) Some are writable.
[0003]
In a writable optical recording medium, a recording track is formed on a substrate in advance. Then, recording and reproduction are performed by causing the light spot of the optical head to follow the recording track.
[0004]
By the way, in recording / reproducing on an optical recording medium, a tracking servo is performed in order to make a light spot follow a recording track. One of the tracking servo systems is a push-pull method.
[0005]
In the push-pull method, reflected light from an optical recording medium is received by two light receiving units and converted into an electric signal. Then, a push-pull signal corresponding to the difference between the electric signals of the respective light receiving sections is generated and set to be used as a track error signal.
[0006]
Also, various methods have been proposed as a method of providing address information on an optical recording medium (assigning and formatting address information). For example, as shown in FIG. 11, there is a method in which a pre-pit 50 corresponding to address information is provided in the middle of a recording track (information track) 49.
However, data cannot be written in such a pre-pit 50. For this reason, in this method, the data efficiency (data recording amount per unit area) is lowered, which is disadvantageous for increasing the density of the medium.
[0007]
Also, for example, Japanese Patent Application Laid-Open No. 64-35727 discloses another method for pre-formatting address information, in which a recording track is wobbled according to the address information.
In this method, address information is obtained by extracting a wobbling frequency component from a track error signal. This method is advantageous in terms of increasing the density of the medium because it is possible to avoid a reduction in data efficiency.
[0008]
Further, in an optical recording medium (optical disk) having the form of an optical disk, it is necessary to generate a clock signal for controlling the rotation of the disk during recording and reproduction. Therefore, there has been proposed a method of generating a clock signal by wobbling a recording track according to a clock signal and extracting a wobbling frequency component from a track error signal.
Normally, the amplitude of wobbling in a recording track is a value that optimizes the quality of a wobbling signal (wobbling reproduction signal; a signal corresponding to a wobbling frequency component extracted from a track error signal).
[0009]
[Problems to be solved by the invention]
Recently, the development of a laser having a shorter wavelength, a higher NA of an objective lens, and a magnetic super-resolution medium has been advanced. With such technical development, recording / reproduction on an optical recording medium capable of high-density recording (high-density medium; an optical recording medium with a narrow recording track pitch and small recording marks) has become possible.
[0010]
However, in such a high-density medium, if the recording track is wobbled with the conventional amplitude in order to embed the address information and the clock information, the effect of the wobbling on the data reproduction becomes large and the reproduction signal is deteriorated. Problems arise.
[0011]
The present invention has been made to solve the above-mentioned conventional problems. An object of the present invention is to provide an optical recording medium having a wobbling amplitude that can improve both the reproduction signal quality of address information and clock information and the recording and reproduction quality of data.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a first optical recording medium (first optical recording medium) according to the present invention has an optical recording / reproducing apparatus in which data is recorded by a recording laser beam and a magnetic field, while data is recorded by a reproducing laser beam. In an optical recording medium on which reproduction is performed, which has a groove wobbled in accordance with incidental information, the numerical aperture of an objective lens in the optical recording / reproducing apparatus is NA, and the wavelength of recording laser light is λ. The absolute value A of the wobbling amplitude in the groove is
0.0044 ≦ A × NA / λ ≦ 0.0133
It is characterized by satisfying.
[0013]
Further, the second optical recording medium (second optical recording medium) in the present invention is an optical recording medium in which data is recorded by a recording laser beam in an optical recording / reproducing apparatus and data is reproduced by a reproducing laser beam. In an optical recording medium having a groove wobbled in accordance with incidental information, when the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA and the wavelength of the recording laser light is λ, the wobbling amplitude in the groove is The absolute value A of the quantity is
0.0042 ≦ A × NA / λ ≦ 0.0126
It is characterized by satisfying.
[0014]
These first and second recording media are optical recording media for reproducing data by irradiating a laser beam in an optical recording / reproducing apparatus.
The first optical recording medium is a magneto-optical recording medium on which data is recorded by a laser beam and a magnetic field. On the other hand, the second optical recording medium is a so-called phase-change type optical recording medium in which data can be recorded only by laser light.
[0015]
As described above, these first and second optical recording media are provided with grooves wobbled (meandering) according to the accompanying information (grooves meandering at a period (frequency) according to the accompanying information).
[0016]
Here, the supplementary information is information other than data (information recorded by a user) on the optical recording medium, and is, for example, address information, clock information, operation control information (rotation control information, etc.). .
At the time of recording / reproducing on the first / second optical recording medium, a reproduction signal (address signal, clock signal, etc.) relating to such additional information is obtained by reflected laser light from the wobbling.
[0017]
Data recording on the first and second optical recording media is performed on the above-mentioned grooves, lands between grooves, or both grooves and lands.
[0018]
In particular, in the case of the first and second optical recording media, the amount of wobbling in the groove is in a range where the reproduction signal quality of the incidental information can be appropriately secured, and the recording / reproduction of data is avoided by avoiding the effect of wobbling. Is set in a range (a range obtained by an experiment) that can be favorably performed.
[0019]
That is, when the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA and the wavelength of the recording laser beam is λ, the absolute value A of the wobbling amplitude in the groove is 0.0044 ≦ A in the case of the first optical recording medium. × NA / λ ≦ 0.0133 is set so as to satisfy 0.0042 ≦ A × NA / λ ≦ 0.0126 in the case of the second optical recording medium.
[0020]
Thereby, in the first and second optical recording media, both the reproduction signal quality of the additional information and the data recording / reproduction quality can be improved.
The above (A × NA / λ) is the ratio (A × NA / λ) of the wobbling amplitude to the spot diameter variable of the laser beam. The laser beam spot diameter variable (λ / NA) is a value obtained by dividing the laser beam spot diameter by a constant.
[0021]
Further, the first recording medium is divided into a recording layer having a magnetization corresponding to data (information recorded by a user) (a recording layer for magnetically recording data) and an area heated to a high temperature by irradiation with a reproduction laser beam. A reproduction layer for transferring the magnetization of the recording layer may be provided. That is, the first recording medium may be a magnetic super-resolution magneto-optical recording medium.
[0022]
In this configuration, while the high-temperature region of the reproduction layer is involved in reproduction, the other region (low-temperature region) can be used as a mask. Thereby, the recording bit (magnetic domain) of the recording layer can be made smaller than the spot diameter of the reproduction laser beam, so that the data recording density can be remarkably improved. Further, by using the mask in the low-temperature region, it is possible to avoid mixing of signals from adjacent bits that cause noise.
[0023]
In the third optical recording medium (third optical recording medium) of the present invention, data is recorded by a recording laser beam and a magnetic field or a recording laser beam in an optical recording / reproducing apparatus, while data is reproduced by a reproducing laser beam. In an optical recording medium to be performed, which has a groove wobbled in accordance with incidental information, the wobbling signal amount (Iw) in a track error signal obtained by reproducing the medium and the flat portion (Iw / Io) and the ratio (Iw / It) of the wobbling signal amount (Iw) to the track error signal amount (It) during off-track. ) Satisfies Iw / Io ≧ 0.010 and Iw / It ≦ 0.071.
[0024]
The third recording medium is, like the first and second optical recording media, an optical recording medium for reproducing data by irradiating a laser beam in an optical recording / reproducing apparatus.
The third optical recording medium may be a magneto-optical recording medium on which data is recorded by laser light and a magnetic field, or a so-called phase-change optical recording medium on which data can be recorded only by laser light. Is also good.
[0025]
The third optical recording medium, like the first and second optical recording media, has a groove wobbled in accordance with incidental information. Then, at the time of recording / reproducing, a reproduction signal relating to such additional information is obtained by reflected light of the laser light from the wobbling. Further, data recording on the third optical recording medium is performed on the above-mentioned grooves, lands between the grooves, or both the grooves and the lands.
[0026]
In particular, in the case of the third optical recording medium, the wobbling signal amount in the track error signal obtained by reproducing the medium is in a range where the reproduction signal quality of the accompanying information can be appropriately secured, and the influence of wobbling is avoided. The range is set to a range where data can be recorded / reproduced satisfactorily (a range obtained by experiments).
[0027]
That is, in the third optical recording medium, the ratio of the wobbling signal amount (Iw) in the track error signal to the electric signal amount (Io) corresponding to the reflected light from a flat portion (a portion without a groove; a land or the like) of the medium. (Iw / Io) satisfies Iw / Io ≧ 0.010.
Further, in the third optical recording medium, the ratio (Iw / It) of the wobbling signal amount (Iw) to the track error signal amount (It) during off-track is set so as to satisfy Iw / It ≦ 0.071. Have been.
[0028]
As a result, in the third optical recording medium, both the reproduction signal quality of the incidental information and the data recording / reproduction quality can be improved.
[0029]
Note that the wobbling signal amount is a signal amplitude amount of a signal corresponding to a wobbling frequency component of a groove, which is extracted from a track error signal (electric signal) obtained by reproducing the third optical recording medium.
[0030]
Here, even if the physical amplitude amount in wobbling is the same, the detected wobbling signal amount changes depending on the reflectance of the sample and the track shape.
The ratio (Iw / Io) is obtained by standardizing the wobbling signal amount (Iw) according to the reflectance of the medium.
That is, the ratio (Iw / Io) is for evaluating the wobbling signal amount (Iw) excluding the influence of the reflectance.
[0031]
The off-track state is when the track servo is not applied. At this time, due to the eccentricity of the track, the light spot of the reproduction laser beam crosses a plurality of tracks. That is, It is the signal amplitude of the track error signal when the light spot crosses a plurality of tracks.
Iw / It is a value obtained by standardizing the wobbling signal amount (Iw) by the track error signal amount (It).
That is, the ratio (Iw / It) is for evaluating the wobbling signal amount (Iw) excluding the influence of the track shape.
[0032]
When the third recording medium is of a type in which data recording is performed by laser light and a magnetic field, this medium is, like the first optical recording medium, a recording layer having a magnetization corresponding to data and a reproduction layer. A reproduction layer for transferring the magnetization of the recording layer in a region heated to a high temperature by the irradiation of the laser beam may be provided. That is, the third recording medium may be a magnetic super-resolution magneto-optical recording medium.
[0033]
Further, the first to third optical recording media usually include a substrate and a laminate formed on the substrate. Here, the laminate is a laminate of a plurality of types of layers effective for recording and reproduction. In addition, it is preferable that this configuration receives recording laser light not from the substrate but from the laminate.
Thereby, the NA of the objective lens in the optical recording / reproducing apparatus can be increased, so that data can be recorded at a high density.
[0034]
Further, the refractive index n of the incident portion of the recording laser light in the first to third optical recording media and the depth d of the groove are defined by:
5.5 ≦ λ / (n × d) ≦ 16
It is preferable to satisfy the following.
[0035]
By setting the refractive index n and the groove depth (groove depth) d in the above ranges, it is possible to more appropriately secure the reproduction signal quality of the incidental information, and to perform the data recording / reproduction better. Has been verified.
[0036]
Note that, as described above, the optical recording medium is usually composed of a substrate and a laminate (formed of a plurality of layers) formed thereon. The above-described recording laser incident site is a site from the surface receiving the recording laser beam to the recording layer (layer for recording data) in the laminate.
In addition, when there are a plurality of layers in the incident portion, the refractive index of the incident portion is an average refractive index in the plurality of layers. Further, as the refractive index of the incident part, the refractive index of the most dominant (thick) layer in the incident part can be adopted.
[0037]
Further, the optical recording / reproducing apparatus is provided with any one of the first to third optical recording media, and is configured to record / reproduce data with respect to the optical recording / reproducing apparatus, so that the reproduction signal quality of the supplementary information can be more appropriately improved. It is possible to provide an optical recording / reproducing apparatus which can secure the data and can perform data recording / reproducing more favorably.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described.
FIG. 3 is a cross-sectional view showing a configuration of a magneto-optical disk (present disk; magneto-optical recording medium) according to the present embodiment.
[0039]
As shown in this figure, this disk has a transparent dielectric layer 25, a reproduction layer 26, a reproduction auxiliary layer 27, a transparent dielectric layer 28, a recording layer 29, a transparent dielectric layer 30, a heat radiation layer on a disk substrate 1. 31 and a protective coat layer 32 are laminated in this order.
[0040]
The transparent dielectric layers 25, 28, and 30 are made of a material that does not contain oxygen, such as AlN, SiN, and AlSiN.
The heat radiation layer 31 is made of an Al film or an alloy film containing Al.
[0041]
The protective coat layer 32 is formed by applying an ultraviolet curable resin by spin coating and irradiating with ultraviolet rays.
The recording layer 29 is a perpendicular magnetization film made of a rare earth transition metal alloy, and can be made of TbFeCo, DyFeCo, TbDyFeCo, or the like having a large coercive force at room temperature.
The reproducing layer (magnetic super-resolution magneto-optical recording / reproducing layer) 26 is made of a rare earth transition metal alloy (for example, GdFeCo, GdDyFeCo, etc.), and is an in-plane magnetized film from room temperature to a critical temperature (predetermined temperature). This is a magnetic layer that transfers to a perpendicular magnetization film.
The reproduction auxiliary layer 27 is an in-plane magnetic film made of a rare earth transition metal alloy (for example, GdFe) having a lower Curie temperature than the reproduction layer 26 and the recording layer 29.
[0042]
FIG. 1 is a plan view showing the configuration of the disk substrate 1, and FIG. 2 is a sectional view of the same. As shown in these figures, grooves 2 and lands 3 are formed on the surface of the disk substrate 1. The above-mentioned layers 25 to 32 are stacked on the surface on which the groove 2 and the land 3 are formed.
[0043]
The groove 2 is a spiral groove located between the wobbled (meandering) side walls 4, and is used for push-pull tracking. The data is recorded in a portion on the groove 2 in the recording layer 29. Therefore, the recording track of the present disk is the groove 2, and the track pitch is the same as the pitch at which the groove 2 is formed.
The land 3 is an area between the grooves 2 and is set to have the same width as the groove 2.
[0044]
The side walls 4 of the groove 2 are wobbled (meandering) in the radial direction of the disk substrate 1 according to the address information (ie, wobbled at a cycle (frequency) according to the address information). The wobbling frequency (meandering frequency) is set to a value higher than the tracking frequency of the tracking servo system and lower than the information recording frequency.
[0045]
Here, recording / reproducing of data to / from this disc will be described. In the present disk, recording / reproduction is performed by receiving a laser beam from the disk substrate 1 side by a recording / reproducing device as described later (substrate incidence method).
Data recording is performed on the recording layer 29 on the groove 2 by laser light and an external magnetic field.
[0046]
At the time of recording / reproduction, a track error signal is obtained by a push-pull method. Further, the address information is obtained by extracting the meandering frequency component of the side wall 4 from the track error signal.
[0047]
That is, as shown in FIG. 1, when the light spot (light spot for recording / reproducing) 5 is made to follow the groove 2, the wobbling frequency is higher than the tracking frequency of the tracking system. Tracking substantially on the center line 6. For this reason, a tracking error equal to half the wobbling amplitude of the groove 2 always occurs.
Therefore, a signal component of the wobbling frequency can be obtained by extracting this error from the track error signal. The same applies to the case where the light spot 5 follows the land 3.
[0048]
Here, it is preferable that the diameter of the light spot 5 is larger than the width of the groove 2 and smaller than 1.5 times the track pitch. Thus, it is possible to prevent the light spot 5 from hitting the side wall 4 of the groove 2 located next to the groove 2 that is following, so that accurate address information can be obtained.
[0049]
The recorded data is reproduced as follows.
That is, the irradiation site of the light spot (reproduction laser light) 5 on the reproduction layer 26 has a temperature distribution according to a Gaussian distribution.
Then, only the region (high-temperature region; having a size corresponding to the recording bit of the recording layer 29) smaller than the diameter of the light spot 5 becomes higher than the critical temperature and shifts from in-plane magnetization to perpendicular magnetization, thereby reducing the magneto-optical effect. As shown.
[0050]
Further, in the high temperature region, the magnetization of the reproducing layer 26 and the recording layer 29 are magnetostatically coupled, and the magnetization (direction of magnetization) of the recording layer 29 is transferred to the reproducing layer 26. Thereby, the data recorded in the recording layer 29 can be reproduced based on the reflected light from the high-temperature region in the reproduction layer 26.
After the data is reproduced, the temperature of the high-temperature region becomes low with the movement of the light spot 5 and shifts from perpendicular magnetization to in-plane magnetization.
[0051]
Further, the low-temperature region in the in-plane magnetization state in the reproducing layer 26 does not exhibit the magneto-optical effect, and thus has a function of masking the magnetization of the recording layer 29 in the region.
As described above, in the present disk, while only the high-temperature region of the reproducing layer 26 is involved in the reproduction, by using the low-temperature region as a mask, the magnetic super-resolution light for reproducing the recording bits smaller than the diameter of the light spot 5 is obtained. It is a magnetic recording medium.
Thereby, the data recording density can be significantly improved. Further, by using the mask in the low-temperature region, it is possible to avoid mixing of signals from adjacent bits that cause noise.
Further, since this disk is a magneto-optical disk, it has higher reliability than other types of media, and can record (rewrite) data more than 1,000,000 times.
[0052]
Next, an optical recording / reproducing apparatus (present recording / reproducing apparatus) for recording / reproducing on / from the present disc will be described. FIG. 4 is an explanatory diagram showing the configuration of the present recording / reproducing apparatus.
As shown in this figure, the present recording / reproducing apparatus includes a semiconductor laser (light source) 34 for generating a laser beam for irradiating the main disc 33, and an optic for guiding the laser beam to the main disc 33 and receiving the reflected light. The head 41 is provided.
[0053]
The optical head 41 includes a collimator lens 35, a polarizer 36, a light splitting element 37, and an objective lens 38. These are arranged on the optical path from the semiconductor laser 34 to the disc 33 in order from the semiconductor laser 34 side. ing. The optical head 41 has an analyzer 39 and a light receiving unit 40 arranged side by side in a direction perpendicular to the optical path.
[0054]
The collimator lens 35 converts the laser light emitted from the semiconductor laser 34 and incident while diffusing, into parallel light. The light splitting element 37 allows the parallel light converted by the collimator lens 35 to pass therethrough, and reflects the reflected light (return light) from the disk 33 toward the analyzer 39.
[0055]
The objective lens 38 condenses the laser light that has passed through the light branching element 37, generates a light spot S, and irradiates the light spot S on the disk 33. The data on the disk 33 is read by the reflected light (return light) of the light spot S. Further, the objective lens 38 also has a function of converting return light that enters while diffusing into parallel light, and causing the parallel light to enter the light splitting element 37.
[0056]
The analyzer 39 and the light receiving section 40 are arranged on the optical path of the return light reflected by the light branching element 37. The light receiving unit 40 is formed of, for example, a phototransistor, and converts a data recorded on the disk 33 and a return light modulation signal corresponding to wobbling (corresponding to address information) into an electric signal.
[0057]
FIG. 5 is an explanatory diagram illustrating the configuration of the light receiving unit 40. As shown in this figure, the light receiving area of the return light in the light receiving section 40 is divided into two by a dividing line parallel to the track of the disk 33. The first light receiving element 42a and the second light receiving element 42b are provided in each area.
[0058]
These light receiving elements 42a and 42b receive return light for each region. That is, the return light incident on the light receiving unit 40 is divided into two by the above-mentioned division line, and is incident on each of the light receiving elements 42a and 42b to be converted into an electric signal.
[0059]
Further, the first light receiving element 42a is connected to a non-inverting input terminal of the differential amplifier 43, while the second light receiving element 42b is connected to an inverting input terminal of the differential amplifier 43.
[0060]
The differential amplifier 43 calculates a differential signal from electric signals of the first light receiving element (first light receiving unit) 42a and the second light receiving element (second light receiving unit) 42b. The differential signal is used to derive a wobbling frequency component of the track and generate a wobbling signal.
[0061]
In the present recording / reproducing apparatus, address information is generated using the wobbling signal generated as described above. Therefore, the present recording / reproducing apparatus has a simple configuration that can manage address information by a simple method and can be easily reduced in size and cost.
[0062]
The recording / reproducing apparatus has a member (not shown) for reproducing data from the electric signal generated by the light receiving unit 40 and for generating and processing a servo signal (not shown).
Here, in the present recording / reproducing apparatus, two servo signals of a track servo signal and a focus servo signal are generated. The track servo signal is obtained from a low band portion of the track error signal. The focus servo signal is generated by another light receiving system (not shown) in the recording / reproducing apparatus.
[0063]
Next, an experiment for confirming appropriate values of the wobbling amplitude, the groove depth (groove depth) and the track pitch in the present disk will be described.
[0064]
[Experiment 1]
In Experiment 1, twelve types of samples of the present disk having various wobbling amplitudes of the side wall 4 were prepared, and data was recorded using the present recording / reproducing apparatus shown in FIG. 4, and then a wobbling signal (address signal) was obtained. And the reproduction signal quality of the data signal (reproduction signal corresponding to the recorded data) was measured.
[0065]
The wobbling signal (address signal) is a reproduction signal corresponding to the wobbling frequency component extracted from the track error signal, and is a signal corresponding to the wobbling of the side wall 4.
[0066]
Note that the wobbling amplitude of each sample was changed by changing the input signal to the optical deflector 15 in the manufacture of the master glass master (described later). The wobbling amplitude of each sample was measured by an AFM device when the disk substrate 1 was formed.
[0067]
In addition, each of the sample layer structures includes a disc substrate 1 made of a polycarbonate resin having a thickness of 0.6 mm, transparent dielectric layers 25, 28, and 30 made of AlN, a reproducing layer 26 made of GdFeCo, a reproducing auxiliary layer 27 made of GdFe, and a TbFeCo. , A heat dissipation layer 31 made of an Al alloy, and a protective coat layer 32 made of an ultraviolet curable resin. The reproducing layer 26 had a characteristic of shifting from in-plane magnetization to perpendicular magnetization at around 150 ° C. (critical temperature was 150 ° C.).
[0068]
The groove width (track width) of each sample was set to 0.4 μm, and the groove depth (groove depth) was set to 35 nm. The wobbling cycle of each sample was fixed (35 μm), and the amount of wobbling amplitude was changed in the range of 0 nm to ± 15 nm.
[0069]
The data recording / reproducing conditions for each sample are as follows.
That is, the wavelength of the laser light (laser light used for recording and reproduction) emitted from the semiconductor laser 34 of the present recording / reproducing apparatus is 405 nm, and the NA (Numerical Aperture; numerical aperture) of the objective lens 38 is 0.6. Set. In addition, laser light was incident on each sample from the disk substrate 1 side.
[0070]
Further, data was recorded at a linear velocity of 3 m / s by optical pulse magnetic field modulation recording with a (1,7) RLL modulation code having a minimum bit length of 0.2 μm. The data recorded in this manner is reproduced to generate a data signal and a wobbling signal (wobbling reproduction signal), and the bit error rate (D-BER) of the data signal, the CNR (W-CNR) of the wobbling signal, Iw / Io and Iw / It were measured.
[0071]
[Table 1]

[0072]
Table 1 is a table showing the wobbling amplitude amount of each sample and the measurement results of D-BER, W-CNR, Iw / Io, and Iw / It.
[0073]
The wobbling signal can be used as a rotation control signal and / or an address signal when it has a W-CNR of 32 dB or more. Table 1 shows that the W-CNR of 32 dB or more can be realized when the wobbling amplitude is ± 3 nm or more.
[0074]
On the other hand, the data signal is 1 × 10 ^-4 When it has the following D-BER, it can be practically used as a signal for reproduction. And 1 × 10 ^-4 From Table 1, it can be seen that the following D-BER can be realized when the wobbling amplitude is set to ± 9 nm or less.
From the above results, it can be said that the wobbling amplitude is preferably in the range of ± 3 nm to ± 9 nm.
[0075]
In addition, the wobbling signal can be used very effectively as a rotation control signal and / or an address signal when having a W-CNR of 34 dB or more.
Further, the data signal is 8 × 10 ^-5 When it has the following D-BER, it is very preferable as a signal for reproduction.
Therefore, it can be said that the amount of wobbling amplitude is more preferably in the range of ± 4 nm to ± 6 nm.
[0076]
Since the wavelength (λ) of the laser beam used for recording and reproduction is 405 nm and the NA of the objective lens 38 is 0.6, the spot diameter variable (λ / NA) of the laser beam in this measurement is 675 nm. Therefore, the range of the ratio (A × NA / λ) of the good wobbling amplitude (± A; A is an absolute value) to the spot diameter variable is:
0.0044 ≦ A × NA / λ ≦ 0.0133.
The laser beam spot diameter variable (λ / NA) is obtained by dividing the laser beam spot diameter by a constant.
[0077]
Further, Table 1 shows Iw / Io and Iw / It for each sample.
Here, Iw / Io is a ratio of a wobbling signal amount (Iw; wobbling signal amplitude amount) in the track error signal to an electric signal amount (Io) obtained by photoelectrically converting light reflected from a portion having no groove. is there.
[0078]
Iw / It is the ratio of the above Iw to the amount of track error signal (It) during off-track.
Here, the off-track state is when the track servo is not applied. At this time, the light spot is in a state of crossing a plurality of tracks due to the eccentricity of the tracks. That is, It is the signal amplitude of the track error signal when the light spot crosses a plurality of tracks.
[0079]
Even if the physical amplitude amount (wobbling physical amplitude amount) in wobbling of each sample is the same, the detected wobbling signal amount changes depending on the reflectance and the track shape of the sample.
Iw / Io is obtained by standardizing the wobbling signal amount (Iw) according to the reflectance of the sample. Thereby, the wobbling signal amount (Iw) can be evaluated excluding the influence of the reflectance.
Iw / It is a value obtained by standardizing the wobbling signal amount (Iw) by the track error signal amount (It). Thus, the wobbling signal amount (Iw) can be evaluated excluding the influence of the track shape.
[0080]
Then, as described above, the wobbling signal can be used as an address signal (and / or a clock signal) when it has a W-CNR of 32 dB or more. Table 1 shows that W-CNR of 32 dB or more can be realized when Iw / Io is 0.010 or more.
[0081]
On the other hand, the data signal is 1 × 10 ^-4 When it has the following D-BER, it can be practically used as a signal for reproduction. And 1 × 10 ^-4 From Table 1, it can be seen that the following D-BER can be realized when Iw / It is 0.071 or less.
Therefore, it can be said that good reproduction signal quality can be obtained if Iw / Io ≧ 0.010 and Iw / It ≦ 0.071.
[0082]
[Experiment 2]
In Experiment 2, a plurality of samples of the present disk having ten kinds of groove depths (groove depths) and various amounts of wobbling amplitude were prepared, and data was recorded using the above-described recording / reproducing apparatus. The reproduction signal quality of the signal (address signal) and the data signal was measured.
The layer structure of each sample and the conditions for recording and reproducing data for each sample were the same as those shown in Experiment 1.
[0083]
[Table 2]

[0084]
Table 2 shows that the D-BER was 1 × 10 in the measurement for each sample. ^-4 6 is a table showing the relationship between the wobbling amplitude amount, the range of Iw / Io and Iw / It, and the groove depth (d) of each sample such that the W-CNR becomes 32 dB or more.
[0085]
Table 2 also shows the value of λ / (n × d), which is the ratio between the wavelength of the laser beam and the optical path length. Here, n is the refractive index of the layer located on the light incident side, that is, the refractive index of the disk substrate 1. The value of λ / (n × d) is inversely proportional to the phase of the light wave, and is obtained by normalizing the groove depth by the reciprocal of the phase.
[0086]
As shown in this table, when 5.5 ≦ λ / (n × d) ≦ 16, Iw / Io ≧ 0.010 and Iw / It ≦ 0.071, and a good reproduction signal quality is obtained. It is understood that it can be done.
[0087]
[Experiment 3]
In Experiment 3, samples of a plurality of discs having eight kinds of track pitches were prepared, and data was recorded using the above-described recording / reproducing apparatus. It was measured.
[0088]
The layer structure of each sample and the conditions for recording and reproducing data for each sample were the same as those shown in Experiment 1. Further, the groove width and the distance between the grooves (land width) of each sample were substantially equal.
[0089]
[Table 3]

[0090]
Table 3 shows that the D-BER was 1 × 10 in the measurement for each sample. ^-4 6 is a table showing the relationship between the wobbling amplitude amount, the range of Iw / Io and Iw / It, and the track pitch (TP) of each sample so that W-CNR becomes 32 dB or more.
This table also shows TP × NA / λ, which is a value obtained by standardizing the track pitch (TP) by a spot diameter variable.
[0091]
In order to increase the density (large capacity) of this disk, the smaller the track pitch and TP × NA / λ, the better. As shown in Table 3, when 0.83 ≦ TP × NA / λ is satisfied, Iw / Io ≧ 0.010 and Iw / It ≦ 0.071, which indicates that good reproduction signal quality can be obtained. .
[0092]
In the present embodiment, it is assumed that recording / reproduction is performed by receiving irradiation of laser light from the disk substrate 1 side in the present disk. However, the present invention is not limited to this, and it is also possible to adopt a configuration in which recording and reproduction can be performed on the present disk by irradiating a laser beam from the protective coating layer 32 side (film surface incidence method).
[0093]
FIG. 6 is a sectional view (explanatory diagram) showing the present disk having such a configuration. As shown in this figure, in this configuration, on the disk substrate 1, a heat dissipation layer 31, a transparent dielectric layer 30, a recording layer 29, a transparent dielectric layer 28, a reproduction auxiliary layer 27, a reproduction layer 26, a transparent dielectric layer 25, the protective coat layer 32 is laminated in this order.
[0094]
As described above, in this configuration, the layers 25 to 31 other than the protective coat layer 32 are stacked in the reverse order to the disc shown in FIG. The material of each layer is the same as that of the disk shown in FIG.
[0095]
In this configuration, recording and reproduction are performed by irradiating a laser beam to the protective coating layer 32 side opposite to the disk substrate 1 on which recording tracks are formed. For this reason, the influence of the warpage of the disk substrate 1 can be reduced. Further, since the NA of the objective lens in the recording / reproducing apparatus can be increased, the density can be increased.
[0096]
Next, an experiment for confirming appropriate values of the wobbling amplitude, the groove depth (groove depth) and the track pitch in the present disk having the configuration shown in FIG. 6 will be described.
[0097]
[Experiment 4]
In Experiment 4, eleven types of samples of the present disk having various wobbling amplitudes of the side wall 4 were prepared, and data was recorded using the present recording / reproducing apparatus shown in FIG. And the reproduction signal quality of the data signal was measured.
[0098]
Note that the layer configuration (layer material and the like) of each sample is the same as that shown in Experiment 1. The groove width (track width) of each sample was set to 0.25 μm, and the groove depth was set to 50 nm. The wobbling cycle of each sample was fixed (35 μm), and the wobbling amplitude was changed in the range of 0 nm to ± 10 nm.
[0099]
The data recording / reproducing conditions for each sample are as follows.
That is, the wavelength of the laser light (laser light used for recording and reproduction) emitted from the semiconductor laser 34 of the recording / reproducing apparatus was set to 405 nm, and the NA of the objective lens 38 was set to 0.9. In addition, laser light was incident on each sample from the protective coat layer 32 side.
[0100]
Further, data was recorded at a linear velocity of 3 m / s by optical pulse magnetic field modulation recording with a (1,7) RLL modulation code having a minimum bit length of 0.133 μm. The data recorded in this manner is reproduced to generate a data signal and a wobbling signal (wobbling reproduction signal), and the bit error rate (D-BER) of the data signal, the CNR (W-CNR) of the wobbling signal, Iw / Io and Iw / It were measured.
[0101]
[Table 4]

[0102]
Table 4 is a table showing the wobbling amplitude amount of each sample and the measurement results of D-BER, W-CNR, Iw / Io, and Iw / It.
[0103]
As described above, the wobbling signal can be used as a rotation control signal and / or an address signal when it has a W-CNR of 32 dB or more. Table 4 shows that the W-CNR of 32 dB or more can be realized when the wobbling amplitude is ± 2 nm or more.
[0104]
On the other hand, the data signal is 1 × 10 ^-4 When it has the following D-BER, it can be practically used as a signal for reproduction. And 1 × 10 ^-4 From Table 1, it can be seen that the following D-BER can be realized when the wobbling amplitude is set to ± 6 nm or less.
From the above results, it can be said that the amount of wobbling amplitude is preferably in the range of ± 2 nm to ± 6 nm.
[0105]
Since the wavelength (λ) of the laser beam used for recording and reproduction is 405 nm and the NA of the objective lens 38 is 0.9, the spot diameter variable (λ / NA) of the laser beam in this measurement is 450 nm. Therefore, the range of the ratio (A × NA / λ) of the good wobbling amplitude to the spot diameter variable is the same as the value obtained in Experiment 1,
0.0044 ≦ A × NA / λ ≦ 0.0133.
[0106]
Further, as shown in Table 4, W-CNR of 32 dB or more and 1 × 10 ^-4 It can be seen that in order to realize the following D-BER and obtain good reproduction signal quality, it is sufficient that Iw / Io ≧ 0.010 and Iw / It ≦ 0.071.
[0107]
[Experiment 5]
In Experiment 5, samples of a plurality of discs having ten kinds of groove depths (groove depths) and various amounts of wobbling amplitude were prepared, and data was recorded using the above-described recording / reproducing apparatus. The reproduction signal quality of the signal (address signal) and the data signal was measured.
The layer configuration of each sample and the conditions for recording and reproducing data for each sample are the same as those shown in Experiment 4.
[0108]
[Table 5]

[0109]
Table 5 shows that the D-BER was 1 × 10 in the measurement for each sample. ^-4 6 is a table showing the relationship between the wobbling amplitude amount, the range of Iw / Io and Iw / It, and the groove depth (d) of each sample such that the W-CNR becomes 32 dB or more.
Table 5 also shows the value of λ / (n × d), which is the ratio between the wavelength of the laser beam and the optical path length. Note that n in this equation is the refractive index of the layer located on the light incident side, that is, the refractive index of the protective coating layer 32.
[0110]
As shown in this table, similarly to the result shown in Table 2 (Experiment 2), when 5.5 ≦ λ / (n × d) ≦ 16, Iw / Io ≧ 0.010 and Iw / It satisfies It ≦ 0.071, which indicates that good reproduction signal quality can be obtained.
[0111]
Also, after preparing samples of a plurality of discs (types of FIG. 6) having various track pitches and recording data using the above-described recording / reproducing apparatus, reproduction of a wobbling signal (address signal) and a data signal are performed. The signal quality was measured. The layer structure of each sample and the conditions for recording and reproducing data for each sample were the same as those shown in Experiment 4. Further, the groove width and the distance between the grooves (land width) of each sample were made substantially equal.
[0112]
As a result, similarly to the result shown in Experiment 3, if 0.83 ≦ TP × NA / λ, Iw / Io ≧ 0.010 and Iw / It ≦ 0.071, and good reproduction It was found that signal quality could be obtained.
[0113]
In the present embodiment, the disk is a magneto-optical disk. However, the optical recording medium of the present invention is not limited to a magneto-optical disk. For example, the optical recording medium of the present invention may be a medium using another recording method such as a phase change disk. Even with such a medium, the same experimental results as those shown in Experiments 1 to 5 have been obtained, and it is known that the preferable range of the wobbling amplitude is the same as that of the magneto-optical disk.
The phase-change disk can record (rewrite) data only by laser light without applying an external magnetic field.
[0114]
Hereinafter, the present disk composed of a phase change disk will be described. FIG. 7 is a cross-sectional view (explanatory diagram) showing the configuration of the present disk composed of a phase change disk.
As shown in this figure, in this configuration, a reflective layer 44, a transparent dielectric layer 45, a recording layer 46, a transparent dielectric layer 47, and a transparent cover layer 48 are laminated on the disk substrate 1 in this order.
[0115]
The transparent dielectric layers 45 and 47 are made of ZnS-SiO ₂ , Al ₂ O ₃ , SiO ₂ And one or two layers. The reflection layer 44 is made of Al or an alloy film containing Al.
The transparent cover layer 48 is made of an ultraviolet curable resin or a plastic sheet. The recording layer 46 is made of a phase change recording material such as GeSbTe or AgInSbTe.
[0116]
In this configuration, recording and reproduction are performed by irradiating a laser beam to the transparent cover layer 48 opposite to the disk substrate 1 on which the recording tracks are formed. For this reason, the influence of the warpage of the disk substrate 1 can be reduced. Further, since the NA of the objective lens in the recording / reproducing apparatus can be increased, the density can be increased.
Further, since the transparent cover layer 48 is provided, the environment resistance of the disk can be improved and the reliability is excellent.
[0117]
Here, an experiment for confirming appropriate values of the wobbling amplitude, the groove depth (groove depth) and the track pitch in the phase change type disk having the configuration shown in FIG. 7 will be described.
[0118]
[Experiment 6]
In Experiment 6, eleven types of samples of the present disk having various wobbling amplitudes of the side wall 4 were prepared, data was recorded using the present recording / reproducing apparatus shown in FIG. 4, and then a wobbling signal (address signal) was obtained. And the reproduction signal quality of the data signal was measured.
[0119]
The groove width (track width) of each sample was set to 0.26 μm, and the groove depth was set to 35 nm. The wobbling cycle of each sample was fixed (35 μm), and the wobbling amplitude was changed in the range of 0 nm to ± 10 nm.
[0120]
The data recording / reproducing conditions for each sample are as follows.
That is, the wavelength of the laser light (laser light used for recording and reproduction) emitted from the semiconductor laser 34 of the recording / reproducing apparatus was set to 405 nm, and the NA of the objective lens 38 was set to 0.85. In addition, laser light was incident on each sample from the transparent cover layer 48 side.
[0121]
Further, data recording was performed with a (1,7) RLL modulation code having a linear velocity of 3 m / s and a minimum bit length of 0.133 μm. Then, the data thus recorded is reproduced to generate a data signal and a wobbling signal, and the bit error rate (D-BER) of the data signal, the CNR (W-CNR) of the wobbling signal, Iw / Io, and Iw / It was measured.
[0122]
[Table 6]

[0123]
Table 6 is a table showing the wobbling amplitude amount of each sample and the measurement results of D-BER, W-CNR, Iw / Io, and Iw / It.
[0124]
As described above, the wobbling signal can be practically used as a rotation control signal and / or an address signal when it has a W-CNR of 32 dB or more. Table 6 shows that the W-CNR of 32 dB or more can be realized when the wobbling amplitude is ± 2 nm or more.
[0125]
On the other hand, the data signal is 1 × 10 ^-4 When it has the following D-BER, it can be practically used as a signal for reproduction. And 1 × 10 ^-4 From Table 1, it can be seen that the following D-BER can be realized when the wobbling amplitude is set to ± 6 nm or less.
[0126]
From the above results, it can be said that it is preferable to set the wobbling amplitude in the range of ± 2 nm to ± 6 nm also in the present disk of the type shown in FIG.
[0127]
Since the wavelength (λ) of the laser beam used for recording and reproduction is 405 nm, and the NA of the objective lens 38 is 0.85, the spot diameter variable (λ / NA) of the laser beam in this measurement is about 476 nm. . Therefore, the range of the ratio (A × NA / λ) of the good wobbling amplitude amount to the spot diameter variable is 0.0042 ≦ A × NA / λ ≦ 0.0126.
[0128]
Further, as shown in Table 6, W-CNR of 32 dB or more and 1 × 10 ^-4 It can be seen that in order to realize the following D-BER and obtain good reproduction signal quality, it is sufficient that Iw / Io ≧ 0.010 and Iw / It ≦ 0.071.
[0129]
Further, with respect to the present disk shown in FIG. 7, a sample in which the groove depth and the amount of wobbling amplitude are changed is prepared, and data is recorded using the above-mentioned recording / reproducing apparatus. Then, a wobbling signal (address signal) and a data The reproduced signal quality of the signal was measured. The layer structure of each sample and the conditions for recording and reproducing data for each sample are the same as described above.
[0130]
As a result of this experiment, similarly to the result shown in Table 2 (Experiment 2), when 5.5 ≦ λ / (n × d) ≦ 16, Iw / Io ≧ 0.010 and Iw / It ≦ 0.071 was obtained, indicating that good reproduction signal quality was obtained (n is the refractive index of the transparent cover layer 48).
[0131]
Also, samples of a plurality of main discs (types shown in FIG. 7) having various track pitches are prepared, data is recorded using the above-described main recording / reproducing apparatus, and then a wobbling signal (address signal) and a data signal are reproduced. The signal quality was measured. The layer configuration of each sample and the conditions for recording and reproducing data for each sample were the same as described above. Further, the groove width and the distance between the grooves (land width) of each sample were made substantially equal.
[0132]
As a result, similarly to the result shown in Experiment 3, if 0.83 ≦ TP × NA / λ, Iw / Io ≧ 0.010 and Iw / It ≦ 0.071, and good reproduction It was found that signal quality could be obtained.
[0133]
Next, a manufacturing method (manufacturing process) of the disk shown in FIGS. 1 and 2 on the disk substrate 1 will be described.
[0134]
In the manufacture of the disk substrate 1, first, a master glass master serving as a base of the disk substrate 1 is prepared. Then, a stamper 24 is formed from the master glass master, and the disk substrate 1 is formed by molding using the stamper 24.
[0135]
First, the manufacturing process of the master glass master will be described. FIGS. 8A to 8E are explanatory diagrams showing a manufacturing process of the master glass master.
[0136]
In the production of the master glass master, first, as shown in FIG. 8A, a photoresist 7 is applied to one surface of the glass master 51.
Next, as shown in FIG. 8B, the laser beam is focused on the photoresist 7 by the objective lens 8, and the photoresist 7 is formed into a desired groove pattern (a pattern corresponding to the groove 2 of the present disk). Exposure according to.
[0137]
Thereafter, as shown in FIG. 8C, the photosensitive portion of the photoresist 7 is removed by developing the photoresist 7. Thus, the above-described groove pattern is formed by the portion where the photoresist 7 has been removed.
[0138]
Next, as shown in FIG. 8D, the glass master 51 is etched by dry etching or wet etching using the photoresist 7 as a mask. Thus, the desired groove pattern described above is formed on the surface of the glass master 51.
Thereafter, as shown in FIG. 8E, the remaining photoresist 7 is removed by ashing or the like. Thereby, the master glass master 9 is completed.
[0139]
Next, a process of manufacturing a molded substrate from the master glass master 9 will be described. FIGS. 9A to 9E are explanatory diagrams for explaining this process.
First, as shown in FIG. 9A, a conductive thin film 22 is formed on the master glass master 9 by sputtering or electroless plating.
[0140]
Next, as shown in FIG. 9B, a metal layer 23 is formed on the thin film 22 by electroforming or the like. Thereafter, as shown in FIG. 9C, the thin film 22 and the metal layer 23 are peeled off from the master glass master 9.
[0141]
Then, as shown in FIG. 9D, the back surface polishing and the inner and outer diameter processing are performed on the thin film 22 and the metal layer 23 to form the stamper 24. Next, as shown in FIG. 9E, the disk substrate 1 made of plastic is formed by injection molding or injection compression molding using the stamper 24.
[0142]
As the material of the thin film 22, it is possible to use Ni, Ta, Cr or an alloy thereof, or a composite film thereof. Further, as a material of the metal layer 23, Ni, Ta, Cr or an alloy thereof, or a composite film thereof can be used.
As a plastic material of the disk substrate 1, a thermoplastic resin such as a polycarbonate resin, an acrylic resin, an ethylene resin, an ester resin, a nylon resin, and an APO (active polyolefin resin) can be used.
[0143]
The method of manufacturing the stamper 24 is not limited to the method using the master glass master 9. For example, a resist master may be prepared, and the stamper 24 may be manufactured using the resist master. Also, by repeating the steps of FIGS. 9A to 9D twice, it is possible to form a stamper with reversed irregularities.
[0144]
Further, the groove depth (land height) of the disk substrate 1 can be controlled by changing the etching condition shown in FIG. 8D in the process of manufacturing the master glass master 9. When both the groove and the land are used as recording tracks (information tracks), it is preferable that the groove depth (land height) is in the vicinity of λ / (6 × n). This configuration can reduce crosstalk (recording noise from adjacent tracks) between recording tracks related to recording signals, and is suitable for high-density recording.
[0145]
8 (a) to 8 (e), a method for manufacturing the master glass master 9 has been described. Here, an apparatus (photosensitive) for exposing the photoresist 7 used for manufacturing the master glass master 9 is described. The device will be described.
[0146]
FIG. 10 is an explanatory diagram showing the configuration of the photosensitive device. As shown in this figure, the photosensitive device includes a laser light source 10a, a laser light source 10b, a noise suppression device 11, a mirror 12, an optical modulator 13, a mirror 14, an optical deflector 15, a beam expander 16, half mirrors 17, 18, An objective lens 19, a cylindrical lens 20, and a photodetector 21 are provided.
[0147]
The laser light source 10a is a light source that emits a laser beam (photosensitive laser beam) applied to expose the photoresist 7. As the laser light source 10a, for example, a Kr laser light source can be used.
[0148]
The noise suppression device 11 reduces the optical noise of the photosensitive laser light emitted from the laser light source 10a and passing therethrough. The mirror 12 directs the traveling direction of the noise-reduced photosensitive laser light to the optical modulator 13.
[0149]
The optical modulator 13 applies a predetermined modulation to the photosensitive laser beam passing therethrough. The mirror 14 directs the traveling direction of the photosensitive laser beam that has passed through the optical modulator 13 to the optical deflector 15. The optical deflector 15 applies a predetermined deflection to the photosensitive laser beam passing therethrough.
In addition, as the optical modulator 13 and the optical deflector 15, for example, an electro-optical element can be used.
[0150]
The beam expander 16 expands the beam diameter of the photosensitive laser light that has passed through the optical deflector 15 to an appropriate size. The half mirror 17 directs the traveling direction of the photosensitive laser beam having the enlarged beam diameter to the objective lens 8. The half mirror 17 also has a function of transmitting a focus laser beam (described later) that has passed through the objective lens 8.
The objective lens 8 focuses the photosensitive laser light from the half mirror 17 or the focus laser light from the half mirror 18 described later on the photoresist 7 on the glass master 51.
[0151]
The laser light source 10b is a light source for laser light (focus laser light) used for focus adjustment of the objective lens 8. As the laser light source 10b, for example, a He-Ne laser beam can be used.
[0152]
The half mirror 18 directs the traveling direction of the focus laser light emitted from the laser light source 10b toward the objective lens 8.
[0153]
The focus laser light condensed and reflected on the photoresist 7 on the glass master 51 by the objective lens 8 passes through the objective lens 8 and the half mirror 18 and travels to the objective lens 19 and the cylindrical lens 20. The objective lens 19 and the cylindrical lens 20 focus the focus laser light passing therethrough on the photodetector 21.
[0154]
The photodetector 21 outputs a drive signal corresponding to the state of the focus laser light focused on itself to a focus servo system (not shown). The focus servo diameter drives the objective lens 8 in the focus direction based on the drive signal. As a result, the objective lens 8 is focused on the photoresist 7 on the glass master 51 which is being rotated by the spindle motor.
[0155]
In this photosensitive device, the light deflector 15 changes the spot position of the photosensitive laser beam in the radial direction of the glass master 51 in accordance with the address information. This makes it possible to wobbled the photosensitive portion of the photoresist 7 according to a desired groove pattern.
[0156]
Further, in the present embodiment, a method for manufacturing the master glass master 9 has been described with reference to FIGS. However, the method of manufacturing the master glass master 9 is not limited to this method. For example, a mask master on which a desired pattern is formed may be prepared, and the master glass master 9 may be manufactured by using the mask master by a contact exposure method.
[0157]
In this embodiment, the wavelengths of the laser beams used for recording and reproduction are the same. However, the present invention is not limited to this, and the wavelengths of the recording laser beam and the reproducing laser beam may be changed.
In this case, the range of (A × NA / λ) relating to the wobbling amplitude of the present disk is 0.0044 ≦ A × NA / λ ≦ 0 in accordance with the wavelength of either the reproduction laser light or the recording laser light. .0133 (0.0042 ≦ A × NA / λ ≦ 0.0126 in the case of the phase change type).
[0158]
Similarly, the ranges of the groove depth (d) and the track pitch (TP) of this disk are set to 5.5 ≦ λ / (n × d) in accordance with the wavelength of either the reproduction laser light or the recording laser light. ) ≦ 16, 0.83 ≦ TP × NA / λ.
[0159]
Further, in the present embodiment, the groove 2 of the disk substrate 1 is assumed to be spiral. However, in the disk substrate 1, the grooves 2 may be formed concentrically.
[0160]
In the present embodiment, the side wall 4 of the groove 2 of the disk substrate 1 is wobbled (meandering) according to the address information. However, the side wall 4 may be wobbled according to the rotation control information (clock information). Thus, a rotation control signal (clock signal) can be obtained based on the wobbling signal. Further, by making the wobbling of the side wall 4 according to both the address information and the clock information, both the address signal and the clock signal can be obtained from the wobbling signal.
[0161]
Further, the side wall 4 may be wobbled according to rotation control information different from the clock signal. Thereby, the above-described rotation control signal can be obtained based on the wobbling signal.
[0162]
Further, by making the wobbling of the side wall 4 according to all of the address information, the clock information and the rotation control information, three signals of the address signal, the clock signal and the rotation control signal can be obtained from the wobbling signal.
[0163]
Also, in the present embodiment, when reproducing the present disk, a track error signal is obtained by the push-pull method. However, the present invention is not limited to this, and the track error signal may be obtained by another method.
[0164]
In the present embodiment, the groove 2 is used as a recording track. However, the present invention is not limited to this, and only the land 3 may be used as the recording track. Further, both the groove 2 and the land 3 may be used as recording tracks.
Whether the light spot 5 follows the groove 2 or the land 3 can be easily selected by inverting the polarity of the track error signal.
[0165]
Further, in this embodiment, the optical head 41 of the present recording / reproducing apparatus shown in FIG. 4 is an optical head for a magneto-optical disk utilizing a magneto-optical effect. However, it is possible to mount an optical head for an optical recording medium using another method in the recording / reproducing apparatus.
[0166]
Further, in the present embodiment, the light receiving section 40 of the present recording / reproducing apparatus shown in FIG. 4 is configured to be divided into two. However, the invention is not limited thereto, and the light receiving unit 40 may be divided into three or more. That is, the light receiving unit 40 is preferably divided into a plurality of regions.
[0167]
The electric signal obtained by photoelectrically converting the light reflected from the disk is divided into a signal (data signal) corresponding to data recorded on the medium and a track error signal (push-pull signal). The above data signal can be expressed as a recording information signal, a recording signal, and a reproduction signal of the recording information, and the wobbling signal is a signal corresponding to a wobbling frequency component extracted from the track error signal. It is also possible to obtain a reproduction signal of rotation control information, a reproduction signal of address information, and a clock signal from the wobbling signal.
[0168]
In the present embodiment, A × NA / λ is a ratio of a good wobbling amplitude to a spot diameter variable (λ / NA). Here, since the light spot diameter is ∝λ / NA, it can be said that A × NA / λ is a constant multiple of the ratio of the wobbling amplitude to the light spot diameter.
[0169]
In the present embodiment, the optical recording medium of the present invention is a magneto-optical disk or a phase-change optical disk. However, the optical recording medium of the present invention does not need to have a disk shape, and may have any shape.
[0170]
In the present embodiment, the refractive index of the disk substrate 1 or the protective coating layer 32 is used as the refractive index.
However, the refractive index n is not limited to this, and the average refractive index in a region from the surface receiving the laser beam irradiation to the recording layer (or the reproducing layer) may be used. In addition, as the refractive index n, the refractive index of the most dominant (thick) layer among the above-mentioned portions, such as the disk substrate 1 or the protective coat layer 32, can be adopted.
[0171]
Further, the optical recording medium of the present invention is an optical recording medium in which data is recorded by a recording laser beam (or a recording laser beam and a magnetic field) in an optical recording / reproducing apparatus, while data is reproduced by a reproducing laser beam. In an optical recording medium provided with a groove wobbled at a frequency corresponding to incidental information, when the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA and the wavelength of the recording laser light is λ, the wobbling amplitude in the groove is Is the absolute value A of. It can also be expressed that the configuration satisfies 0042 ≦ A × NA / λ ≦ 0.0126 (or 0.0044 ≦ A × NA / λ ≦ 0.0133).
[0172]
In general, it can be said that the wobbling amplitude of the recording track in the optical recording medium is optimized from the signal quality of the wobbling reproduction signal. In addition, there is a demand for higher density of optical recording media, and by shortening the wavelength of lasers, increasing the NA of objective lenses, and developing magnetic super-resolution media, the track pitch of information tracks has become narrower and recording information signals have become narrower. It can be said that wobbling of the information track has a greater effect on the reproduction signal of the recorded information, and that the information reproduction signal deteriorates with the conventional wobbling amplitude. Also, with the narrower track pitch, the amount of wobbling amplitude also becomes smaller, and it can be said that it is becoming difficult to control only physical quantities during substrate manufacturing.
[0173]
The optical disk shown in FIG. 3 can be reproduced as follows. That is, when the reproducing layer 26 is irradiated with the light beam, the temperature distribution of the irradiated portion becomes a Gaussian distribution, so that the temperature of only the region smaller than the diameter of the light beam increases. As the temperature rises, the magnetization at the temperature rise site shifts from in-plane magnetization to perpendicular magnetization. That is, the direction of magnetization of the recording layer 29 is transferred to the reproducing layer 26 by magnetostatic coupling between the two layers of the reproducing layer 26 and the recording layer 29. When the temperature rising portion shifts from in-plane magnetization to perpendicular magnetization, only the temperature rising portion exhibits the magneto-optical effect, and information recorded in the recording layer 29 is reproduced based on the reflected light from the temperature rising portion. . Then, when the light beam moves and reproduces the next recording bit, the temperature of the preceding reproducing portion decreases, and the magnetization shifts from perpendicular magnetization to in-plane magnetization. Along with this, the portion where the temperature is lowered does not show the magneto-optical effect, and the magnetization recorded on the recording layer 29 is masked by the in-plane magnetization of the reproducing layer 26 and cannot be reproduced. This prevents a signal from an adjacent bit that causes noise from being mixed. As described above, since only the region having a temperature equal to or higher than the predetermined temperature is involved in the reproduction, the recording bit smaller than the diameter of the light beam can be reproduced, and the recording density is remarkably improved.
[0174]
Further, the differential amplifier 43 calculates a differential signal from the electric signal from the first light receiving element 42a and the electric signal from the second light receiving element 42b, and uses this differential signal to calculate the rotation control from the wobbling signal of the track. It can also be said that a signal (if wobbling is responsive to clock information) and / or an address signal is generated.
[0175]
Further, although the optical head 41 shown in FIG. 4 shows an optical head for a magneto-optical disk utilizing a magneto-optical effect, the optical recording / reproducing apparatus according to the present invention can be applied to a disk capable of recording by another method. Is applicable. Further, in the optical recording / reproducing apparatus shown in FIG. 4 or FIG. 5, although not explicitly shown in the figures, a function of reproducing a signal recorded on an optical disk and generating and processing a servo signal is added to the apparatus. Needless to say.
[0176]
Further, the apparatus shown in FIG. 10 can be expressed as an apparatus for exposing the photoresist 7 to the pattern of the groove 2. Also, the configuration of this device can be expressed as follows. That is, the apparatus includes a laser light source 10a for exposing the photoresist 7 and a laser light source 10b for focusing the objective lens 8. For example, a Kr laser is used as the laser light source 10a, and the laser light source 10b is used as the laser light source 10b. For example, a He-Ne laser is used. The laser light from the laser light source 10 a is reduced in optical noise by the noise suppression device 11, is reflected by the mirror 12, and enters the optical modulator 13. The laser light that has passed through the optical modulator 13 is reflected by the mirror 14 and enters the optical deflector 15. As the optical modulator 13 and the optical deflector 15, for example, an electro-optical element can be used. The laser beam that has passed through the optical deflector 15 is expanded to an appropriate beam diameter by a beam expander 16 and then enters the objective lens 8 by a half mirror 17. Then, the light is focused on the photoresist 7 on the glass master 51 by the objective lens 8.
[0177]
On the other hand, the laser light from the laser light source 10 b is reflected by the half mirror 18 and is focused on the photoresist 7 on the glass master 51 by the objective lens 8. The reflected light passes through the objective lens 8 and the half mirror 18, and is condensed on the photodetector 21 by the objective lens 19 and the cylindrical lens 20. On the basis of a signal from the photodetector 21, the focus servo system drives the objective lens 8 in the focus direction, and the focus of the objective lens 8 is focused on the photoresist 7 on the glass master 51 which is rotated by the spindle motor. In the above configuration, the groove is wobbled in a desired pattern by changing the laser spot in the radial direction according to the rotation control information and / or the address information by the optical deflector 15.
[0178]
Table 2 shows that, at each groove depth, W-CNR is 32 dB or more and D-BER is 1 × 10 ^-4 It can be said that the range of the wobbling amplitude, Iw / Io, and Iw / It is shown.
[0179]
Table 3 shows that samples having substantially the same width between the grooves and changing the track pitch were prepared. At each track pitch, the W-CNR was 32 dB or more and the D-BER was 1 × 10 ^-4 It can be said that the following shows the ranges of the wobbling amplitude amount, Iw / Io, and Iw / It.
Further, λ is the wavelength of the recording laser, and n is the refractive index on the light incident side of the track (the refractive index of the disk substrate 1 in the case of the substrate incident method, and the refractive index of air or a cover layer in the case of the film incident method). It may be.
[0180]
In addition, the present invention can be expressed as the following fourth to tenth optical recording media and first and second optical recording / reproducing apparatuses. That is, the fourth optical recording medium has a track for recording data, and in the optical recording medium in which the track is wobbled with a signal modulated according to rotation control information and / or address information, the wobbling of the track is performed. The amplitude ± A is in the range of 0.0044 ≦ A × NA / λ ≦ 0.0133 (NA: numerical aperture of the objective lens, λ: recording laser wavelength). According to this configuration, it is possible to ensure the quality of the reproduction signal of the rotation control information and / or the address information and to suppress the influence of the recording information on the reproduction signal.
Further, "an optical recording medium in which the track is wobbled with a signal modulated in accordance with rotation control information and / or address information" means "an optical disk wobbled in accordance with rotation control information and / or address information." It can also be expressed as "recording medium".
[0181]
The fifth optical recording medium has a track on which data is recorded, and the track is wobbled with a signal modulated according to rotation control information and / or address information. Is within the range of Iw / Io ≧ 0.010 and Iw / It ≦ 0.071 (Io: the amount of light reflected from the flat portion of the optical recording medium, It: the track error signal during off-track) Quantity). According to this configuration, the quality of the reproduced signal of the control information and / or the address information can be ensured, and the influence of the recorded information on the reproduced signal can be suppressed, so that the control of the wobbling amplitude at the time of manufacturing the substrate becomes easy.
[0182]
The sixth optical recording medium has a configuration in which the track depth d is in the range of 5.5 ≦ λ / (n × d) ≦ 16 in the fourth or fifth optical recording medium. According to this configuration, by adjusting the amplitude of the wobbling, it is possible to ensure the quality of the reproduction signal of the rotation control information and / or the address information and to suppress the influence of the recording information on the reproduction signal.
[0183]
Further, the seventh optical recording medium has a configuration in which at least a magneto-optical recording layer is formed in any of the fourth to sixth optical recording media. According to this configuration, it is possible to provide an optical recording medium that can be rewritten 1,000,000 times or more.
[0184]
The eighth optical recording medium has a configuration in which at least a phase change recording layer is formed in any of the fourth to sixth optical recording media. According to this configuration, it is possible to provide an optical recording medium that can be rewritten only with laser light.
[0185]
The ninth optical recording medium has a configuration in which at least a magnetic super-resolution magneto-optical recording / reproducing layer is formed in any of the fourth to sixth optical recording media. According to this configuration, it is possible to reproduce a bit smaller than the diameter of the light spot, and it is possible to increase the density.
[0186]
In addition, the tenth optical recording medium is configured to perform recording / reproduction from any of the fourth to sixth optical recording media from the side opposite to the substrate on which the track is formed. According to this configuration, the NA of the objective lens can be increased, and the density can be increased.
[0187]
The first optical recording / reproducing apparatus has a track for recording data, the track is wobbled with a signal modulated according to rotation control information and / or address information, and the wobbling amplitude ± A of the track is set. Is an optical recording / reproducing apparatus for recording / reproducing information on / from an optical recording medium satisfying a range of 0.0044 ≦ A × NA / λ ≦ 0.0133, wherein the optical recording medium is irradiated with light; An optical head that receives light reflected from the optical recording medium by a pair of light receiving units and converts the light into an electric signal, based on a push-pull signal obtained by taking a difference between the electric signal, rotation control information and And / or reproducing address information. According to this configuration, it is possible to reproduce a high-density recording information signal, a rotation control signal, and / or an address signal.
[0188]
Further, the second optical recording / reproducing apparatus has a track for recording data, the track is wobbled with a signal modulated according to rotation control information and / or address information, and a reproduction signal from the wobbling of the track is provided. An optical recording / reproducing apparatus for recording / reproducing information on / from an optical recording medium having an amount Iw in a range of Iw / Io ≧ 0.010 and Iw / It ≦ 0.071, wherein the optical recording medium An optical head for irradiating light to the optical recording medium and receiving the light reflected from the optical recording medium by a pair of light receiving units and converting the light into an electric signal, based on a push-pull signal obtained by taking the differential of the electric signal. And reproduces the rotation control information and / or the address information. According to this configuration, it is possible to reproduce a high-density recording information signal, a rotation control signal, and / or an address signal.
[0189]
【The invention's effect】
As described above, in the first optical recording medium (first optical recording medium) in the present invention, data is recorded by the recording laser beam and the magnetic field in the optical recording / reproducing apparatus, and data is reproduced by the reproducing laser beam. In an optical recording medium having grooves wobbled in accordance with incidental information, the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA, and the wavelength of the recording laser light is λ. The absolute value A of the wobbling amplitude amount in the groove is
0.0044 ≦ A × NA / λ ≦ 0.0133
It is the structure which satisfies.
[0190]
Further, the second optical recording medium (second optical recording medium) in the present invention is an optical recording medium in which data is recorded by a recording laser beam in an optical recording / reproducing apparatus and data is reproduced by a reproducing laser beam. In an optical recording medium having a groove wobbled in accordance with incidental information, when the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA and the wavelength of the recording laser light is λ, the wobbling amplitude in the groove is The absolute value A of the quantity is
0.0042 ≦ A × NA / λ ≦ 0.0126
It is the structure which satisfies.
[0191]
In these first and second optical recording media, the wobbling amplitude in the groove is within a range in which the reproduction signal quality of the incidental information can be suitably secured, and the recording and reproduction of data can be performed favorably by avoiding the effect of wobbling. It is set within the range that can be performed (the range obtained by experiments).
[0192]
That is, when the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA and the wavelength of the recording laser beam is λ, the absolute value A of the wobbling amplitude in the groove is 0.0044 ≦ A in the case of the first optical recording medium. × NA / λ ≦ 0.0133 is set so as to satisfy 0.0042 ≦ A × NA / λ ≦ 0.0126 in the case of the second optical recording medium.
Thereby, in the first and second optical recording media, both the reproduction signal quality of the additional information and the data recording / reproduction quality can be improved.
[0193]
Further, the first recording medium is divided into a recording layer having a magnetization corresponding to data (information recorded by a user) (a recording layer for magnetically recording data) and an area heated to a high temperature by irradiation with a reproduction laser beam. A reproduction layer for transferring the magnetization of the recording layer may be provided. That is, the first recording medium may be a magnetic super-resolution magneto-optical recording medium.
[0194]
In this configuration, while the high-temperature region of the reproduction layer is involved in reproduction, the other region (low-temperature region) can be used as a mask. Thereby, the recording bit (magnetic domain) of the recording layer can be made smaller than the spot diameter of the reproduction laser beam, so that the data recording density can be remarkably improved. Further, by using the mask in the low-temperature region, it is possible to avoid mixing of signals from adjacent bits that cause noise.
[0195]
In the third optical recording medium (third optical recording medium) of the present invention, data is recorded by a recording laser beam and a magnetic field or a recording laser beam in an optical recording / reproducing apparatus, while data is reproduced by a reproducing laser beam. In an optical recording medium to be performed, which has a groove wobbled according to incidental information, the wobbling signal amount (Iw) in a track error signal obtained by reproducing the medium and the flat portion (Iw / Io) and the ratio (Iw / It) of the wobbling signal amount (Iw) to the track error signal amount (It) during off-track. ) Satisfies Iw / Io ≧ 0.010 and Iw / It ≦ 0.071.
[0196]
In the third optical recording medium, the amount of the wobbling signal in the track error signal obtained by reproducing the medium is within a range in which the quality of the reproduction signal of the supplementary information can be appropriately secured. The range is set to a range in which recording and reproduction can be performed satisfactorily (a range obtained by experiments).
[0197]
That is, in the third optical recording medium, the ratio (Iw) between the amount of wobbling signal (Iw) in the track error signal and the amount of electric signal (Io) corresponding to the reflected light from a flat portion (a portion without a groove; a land or the like). / Io) satisfies Iw / Io ≧ 0.010.
Further, in the third optical recording medium, the ratio (Iw / It) of the wobbling signal amount (Iw) to the track error signal amount (It) during off-track is set so as to satisfy Iw / It ≦ 0.071. Have been.
As a result, in the third optical recording medium, both the reproduction signal quality of the incidental information and the data recording / reproduction quality can be improved.
[0198]
When the third recording medium is of a type in which data recording is performed by laser light and a magnetic field, this medium is, like the first optical recording medium, a recording layer having a magnetization corresponding to data and a reproduction layer. A reproduction layer for transferring the magnetization of the recording layer in a region heated to a high temperature by the irradiation of the laser beam may be provided. That is, the third recording medium may be a magnetic super-resolution magneto-optical recording medium.
[0199]
Further, the first to third optical recording media usually include a substrate and a laminate formed on the substrate. Here, the laminate is a laminate of a plurality of types of layers effective for recording and reproduction. In addition, it is preferable that this configuration receives recording laser light not from the substrate but from the laminate.
Thereby, the NA of the objective lens in the optical recording / reproducing apparatus can be increased, so that data can be recorded at a high density.
[0200]
Further, the refractive index n of the incident portion of the recording laser light in the first to third optical recording media and the depth d of the groove are defined by:
5.5 ≦ λ / (n × d) ≦ 16
It is preferable to satisfy the following.
[0201]
By setting the refractive index n and the groove depth (groove depth) d in the above ranges, it is possible to more appropriately secure the reproduction signal quality of the incidental information, and to perform the data recording / reproduction better. Has been verified.
[0202]
Note that, as described above, the optical recording medium is usually composed of a substrate and a laminate (formed of a plurality of layers) formed thereon. The above-described recording laser incident site is a site from the surface receiving the recording laser beam to the recording layer (layer for recording data) in the laminate.
In addition, when there are a plurality of layers in the incident portion, the refractive index of the incident portion is an average refractive index in the plurality of layers. Further, as the refractive index of the incident part, the refractive index of the most dominant (thick) layer in the incident part can be adopted.
[0203]
Further, the optical recording / reproducing apparatus is provided with any one of the first to third optical recording media, and is configured to record / reproduce data with respect to the optical recording / reproducing apparatus, so that the reproduction signal quality of the supplementary information can be more appropriately improved. It is possible to provide an optical recording / reproducing apparatus which can secure the data and can perform data recording / reproducing more favorably.
[Brief description of the drawings]
FIG. 1 is a plan view showing a disk substrate of a magneto-optical disk according to an embodiment of the present invention.
FIG. 2 is a sectional view of the disk substrate shown in FIG.
FIG. 3 is a sectional view showing a configuration of the magneto-optical disk.
FIG. 4 is an explanatory diagram showing a configuration of an optical recording / reproducing apparatus according to one embodiment of the present invention.
5 is an explanatory diagram showing a configuration of a light receiving unit in the optical recording / reproducing apparatus shown in FIG.
FIG. 6 is a sectional view showing a configuration of another magneto-optical disk according to an embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a configuration of still another magneto-optical disk according to an embodiment of the present invention.
FIG. 8 is an explanatory view showing a manufacturing process of a master glass master used for manufacturing the disk substrate shown in FIG. 1;
FIG. 9 is an explanatory view showing a process of manufacturing a molded substrate from the master glass master.
FIG. 10 is an explanatory diagram showing a configuration of a photosensitive device that is used for manufacturing the master glass master and exposes a photoresist.
FIG. 11 is an explanatory diagram showing a configuration of a conventional optical recording medium.
[Explanation of symbols]
1 disk board
2 grooves
3 Land
4 Side wall
5 light spots
6 center line
7 Photoresist
8 Objective lens
9 Master glass master
10a Laser light source
10b Focus laser light source
11 Noise suppression device
12 mirror
13 Optical modulator
14 Mirror
15 Optical deflector
16 beam expander
17 Half mirror
18 Half mirror
19 Objective lens
20 cylindrical lens
21 Photodetector
22 Thin film
23 Metal layer
24 Stamper
25 Transparent dielectric layer
26 Reproduction layer
27 Reproduction support layer
28 Transparent dielectric layer
29 Recording layer
30 transparent dielectric layer
31 Heat dissipation layer
32 Protective coat layer
33 disks
34 Semiconductor Laser
35 Collimator lens
36 polarizer
37 Optical splitter
38 Objective lens
39 Analyzer
40 light receiving section
41 Optical Head
43 Differential Amplifier
44 Reflective layer
45 Transparent dielectric layer
46 recording layer
47 Transparent dielectric layer
48 Transparent cover layer
49 recording tracks
A Wobbling amplitude
λ Laser light wavelength
n Refractive index
d Groove depth

Claims (7)

An optical recording medium in which data is recorded by a recording laser beam and a magnetic field in an optical recording / reproducing apparatus, while data is reproduced by a reproducing laser beam.
In an optical recording medium having grooves wobbled in accordance with incidental information, when the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA and the wavelength of the recording laser light is λ,
The absolute value A of the wobbling amplitude amount in the groove is
0.0044 ≦ A × NA / λ ≦ 0.0133
An optical recording medium characterized by satisfying the following. A recording layer having a magnetization according to data,
The optical recording medium according to claim 1, further comprising: a reproducing layer that transfers magnetization of the recording layer in a region heated to a high temperature by the irradiation of the reproducing laser beam. An optical recording medium in which data is recorded by a recording laser beam in an optical recording / reproducing apparatus, while data is reproduced by a reproducing laser beam,
In an optical recording medium having grooves wobbled in accordance with incidental information, when the numerical aperture of the objective lens in the optical recording / reproducing apparatus is NA and the wavelength of the recording laser light is λ,
The absolute value A of the wobbling amplitude amount in the groove is
0.0042 ≦ A × NA / λ ≦ 0.0126
An optical recording medium characterized by satisfying the following. An optical recording medium in which data is recorded by a recording laser beam and a magnetic field, or a recording laser beam in an optical recording / reproducing apparatus, while data is reproduced by a reproducing laser beam,
In an optical recording medium having grooves wobbled in accordance with incidental information, a wobbling signal amount (Iw) in a track error signal obtained by reproducing the medium and an electric signal amount in accordance with light reflected from a flat portion. Ratio (Iw / Io) to (Io), and
The ratio (Iw / It) of the wobbling signal amount (Iw) to the track error signal amount (It) during off-track is:
Iw / Io ≧ 0.010 and Iw / It ≦ 0.071
An optical recording medium characterized by satisfying the following. It consists of a substrate and a laminate formed on the substrate,
5. The optical recording medium according to claim 1, wherein the recording laser beam is set to be incident from the side of the laminate. The depth d of the groove and the refractive index n of the incident portion of the recording laser beam are:
5.5 ≦ λ / (n × d) ≦ 16
The optical recording medium according to claim 1, wherein the optical recording medium satisfies the following. An optical recording / reproducing apparatus comprising the optical recording medium according to any one of claims 1 to 6, and recording / reproducing data on / from the optical recording medium.

Images