JP3989789B2 - Phase change optical recording medium and recording method thereof - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、光ビームを照射することにより記録層材料に光学的な変化を生じさせて情報の記録、再生を行ない、かつ書換えが可能な相変化型光記録媒体とその記録方法に関するものである。
【０００２】
【従来の技術】
本発明に関連する発明としては特開平５−１５１５７２号公報（登録済み）に係るものがあり、記録ストラテジの形式は本発明に似ているが、技術思想は異なり、かつパワーレベルの設定範囲も相違している。
また、特開平９−１３８９４７号公報（登録済み）には、図３に示す記録ストラテジを用い、ＣＤ−ＲＷへの適用を目的として、パルスの幅などを規定した発明が開示されている。
また、特開平１１−１１５３１３号公報には、従来の記録方法を用いた光ディスクの設計方法を採用した、再結晶化上限線速度が２．５〜５．０ｍ／ｓである光記録媒体の発明が開示されている。
【０００３】
従来からＣＤ−ＲＷ、ＤＶＤ＋ＲＷ、ＤＶＤ−ＲＷなどに用いられているＡｇＩｎＳｂＴｅ系合金を記録材料とする相変化型光記録媒体に関しては、特開平１１−１１５３１３号公報に示すような設計がなされ、媒体の設計指針としては、記録方法をあまり複雑化せずに済むように反射率がハイレベルからローレベルに転移する線速に対し、該線速以下の線速範囲を記録可能線速範囲としてきた。
しかし最近のように高い記録線速と更に広い記録可能線速範囲が求められるようになってくると、材料による記録線速の高速化だけでは記録マークの保存信頼性が低下してしまうなど問題が顕在化する。
【０００４】
本発明者等は、従来の設計線速範囲以上の記録可能線速範囲においても充分なオーバーライト特性が得られ、記録マークの保存信頼性が充分に図れる光記録媒体とその記録方法の提供を目的として、基板上に少なくとも相変化記録層と反射層を有し、少なくともＣＡＶ記録によるオーバーライトが可能な記録線速範囲以上の記録線速範囲を有する光記録媒体であって、低速側において最適なオーバーライト特性が得られる消去パワー（Ｐｅｌｏ）より高いレーザー光の連続照射により反射率が低下し始める線速（反射率低下線速）が記録可能な記録線速範囲内に存在する相変化型光記録媒体、及び低速側において最適なオーバーライト特性が得られる消去パワー（Ｐｅｌｏ）以上のレーザー光の連続照射により反射率が低下し始める線速（反射率低下線速）に対し、反射率低下線速以下の記録線速においては消去パワー（Ｐｅｌｏ）を記録パワー（Ｐｗ）の０．４倍以上に設定し、これ以上の記録線速においては消去パワー（Ｐｅｈｉｇｈ）の平均値を記録パワー（Ｐｗ）の０．４倍未満に設定する相変化型光記録媒体の記録方法を発明し（以下、発明Ａという）、別途出願した（特願２００２−２２０３８５号）。
【０００５】
上記発明Ａによれば、高線速記録が可能な相変化型光記録媒体とその記録方法が得られるが、本発明は、更に記録方法を改善し、同じ光記録媒体を使用しても一層の高速記録が可能な記録方法を提供するものである。
具体的にＤＶＤを例として説明すると、特開平１１−１１５３１３号公報記載の設計方法により作成した光記録媒体を用い、特開平９−１３８９４７号公報記載の従来の記録方法で記録可能な線速範囲を約９ｍ／ｓとすると、該光記録媒体と同じ記録材料を用い、発明Ａのような媒体設計をし、発明Ａの記録方法を用いて記録すれば、１２．５ｍ／ｓ程度の記録線速に対応する光記録媒体を得ることができる。
【０００６】
しかし、発明Ａの記録方法を用いて１２．５ｍ／ｓ以上のスピードで記録しようとすると、初回の記録についてはかなり早い線速領域まで記録可能であるが、オーバーライトについては１回目のオーバーライトからジッタ特性が急激に悪くなってしまうという問題が生じる。これは、記録済みマークの消去が十分に行えないために起る現象である。
発明Ａは、ＣＡＶ記録を行うなどの目的であまり記録ストラテジ変化を好まないシステムにおいて記録線速範囲を広げるという目的には非常に良い方法であるが、更に高線速側に着目するとまだ改善の余地がある。つまり、発明Ａの方式は高線速側の記録を可能にするために消去パワーＰｅを低く設定しているのが特徴であるが、そのためにより高速にしようとした場合にはＰｅを更に低下していく必要がある。Ｐｅレベルが小さくなり過ぎれば、スペース部には記録済みのマークが消去できずに残ってしまう。
【０００７】
これに対し本発明の記録方式を用いれば、消去に必要なエネルギーはＰｅ領域にパルス状にＰｅ＋を配置することによって供給でき、更に良好な結晶状態とするには低いレベルのＰｅで補修すれば良いわけである。このような考え方は特開平５−１５１５７２号公報に記載の発明（以下、発明Ｂという）と類似しているようにも見えるが、発明Ｂのパルスデューティー比は０．５〜０．７５と計算できるのに対し、本発明では、後述するように、Ｐｅ＋のパルスデューティー比が０．５以下のときに良い結果が得られることから、両発明は異なった発明であると考えられる。
更に、発明Ｂでは、パルス後のパワーレベルは殆どゼロレベルであると判断できるのに対し、本発明においては、パルス後のパワーレベルＰｅは結晶状態をコントロールする領域であるため、ある一定のパワーレベルが必要であり、発明Ｂの消去パルスとは性格が異なる。
恐らく発明Ｂでは、消去時の温度変動を防ぐ目的でパルス消去を用いているものと考えられる。
【０００８】
【発明が解決しようとする課題】
本発明は、従来よりも高速の記録を行った際のオーバーライト特性が良好となる相変化型光記録媒体の記録方法、及び該記録方法の実施に好適な相変化型光記録媒体の提供を目的とする。
【０００９】
【課題を解決するための手段】
上記課題は、次の１）〜５）の発明（以下、本発明１〜５という）によって解決される。
１） 基板上に少なくとも相変化記録層と反射層を有する相変化型光記録媒体に記録マークを形成するに際し、記録に用いるレーザー光などの光ビームの発光波形を複数のパルスからなる記録パルス列とし、このパルス列を変調することによって記録を行う方法であって、記録マーク部は記録パワー（Ｐｗ）とボトムパワー（Ｐｂ）の間で変調されたパルス列とし、スペース部は記録パワー（Ｐｗ）と消去パワー（Ｐｅ）の間のレベルに設定されたパワー（Ｐｅ＋）と消去パワー（Ｐｅ）の間で変調されたパルス列とし、記録マーク部のＰｗのパルスデューティ比を予め０．２〜０．８の範囲に設定し、スペース部のＰｅ＋のパルスデューティ比を予め０．０５〜０．４の範囲に設定することを特徴とする相変化型光記録媒体の記録方法。
２） 基板上に少なくとも相変化記録層と反射層を有する相変化型光記録媒体に記録マークを形成するに際し、記録に用いるレーザー光などの光ビームの発光波形を複数のパルスからなる記録パルス列とし、このパルス列を変調することによって記録を行う方法であって、記録マーク部は記録パワー（Ｐｗ）とボトムパワー（Ｐｂ）の間で変調されたパルス列とし、スペース部は記録パワー（Ｐｗ）と消去パワー（Ｐｅ）の間のレベルに設定されたパワー（Ｐｅ＋）と消去パワー（Ｐｅ）の間で変調されたパルス列とし、Ｐｅ＋のパルスデューティ比が０．３以上の場合に、光ビームの照射により相変化記録層が記録材料の融点以上となるパワー条件をＰｅ＋として使用する場合には、スペース部のＰｅ＋のパルスデューティ比を０．３未満とすることを特徴とする相変化型光記録媒体の記録方法。
３） Ｐｅが記録マークの形成に最適な記録パワーＰｗの０．２〜０．４倍である１）又は２）に記載の相変化型光記録媒体の記録方法。
４） 予め決められた記録線速以上の場合には１）〜３）の何れかに記載の記録方法を用い、予め決められた記録線速未満の場合にはスペース部を変調せずに、予め決められたＰｅの連続光とすることを特徴とする相変化型光記録媒体の記録方法。
５） ４）記載の記録方法における記録ストラテジを変更する記録線速（予め決められた記録線速）が、記録方法の設定情報として記録されていることを特徴とする相変化型光記録媒体。
【００１０】
以下、上記本発明について詳しく説明する。
図１は、本発明に関連する書き換え型の相変化型光記録媒体の説明図である。図１（ａ）は斜視図であり、一部切り欠いた状態を示している。図１（ｂ）は、該切り欠き部の断面図である。
記録層は通常、初期化により結晶相（消去状態）となっている。そして、本発明の記録方法などにより変調した光ビームを照射することによって、記録層にはアモルファス状態の記録マークが形成される。
図２に、本発明の記録方法の概略例を示す。
本発明の記録方法では、オーバーライト時のスペース部において消去エネルギーを与えるパワーＰｅ＋のパルスと消去レベルをコントロールするＰｅパワーレベルが一対になって、より高速な記録線速においても良好な消去特性が得られる。
【００１１】
【実施例】
以下、実施例により本発明を具体的に説明するが、本発明はこれらの実施例により限定されるものではない。
【００１２】
実施例１
図３に示す様な特開平９−１３８９４７号公報に記載の記録ストラテジを用いて記録した場合に、約３倍速までの記録線速において記録が可能な光記録媒体に対して、Ｐｅレベルを変化させる前記発明Ａの記録方法を用いて記録した場合と、本発明の記録ストラテジを用いて記録した場合とにおいて得られるジッタ特性を表１に示す。
ジッタ特性はチャネル周期Ｔｗに対するマークエッジのばらつきσ／Ｔｗ（％表示）で評価しその実測値を記載した。
相変化型光記録媒体としてはＤＶＤ密度の記録に対応するものを用い、記録装置もＤＶＤ用の波長６６０ｎｍ、ＮＡ０．６５のピックアップを用いて１００回までのオーバーライトを行った結果を示した。記録スピードはＤＶＤの１、２、４、５倍速の条件で行った。
特に５倍速条件でのオバーライト特性の結果については、図４にグラフを用いて示した。発明Ａの記録方法（ストラテジＡ）を用いて記録した場合には、オーバーライト特性、特にＤＯＷ１のジッタ上昇が大きく、この辺りのオーバーライト回数においてスペース部の消去不足が顕著になっていることが確認された。
これに対し、本発明の記録ストラテジ（改良ストラテジ）を用いた結果では、このオーバーライト繰り返しにおいてもジッタ上昇が緩和されており、本発明の記録ストラテジの有効性が確認された。
このとき５倍速の記録ストラテジの各条件は基本的に以下のように設定した。
まず、レーザビームのパワーは、Ｐｗ＝１８ｍＷ、Ｐｅ＋＝１２ｍＷ、Ｐｅ＝６ｍＷとした。
記録マーク部のＰｗのパルスデューティ比は約０．５、スペース部のＰｅ＋のパルスデューティ比は０．２５とし、周波数は各線速毎にＤＶＤのチャネル周波数に合わせて変更した。
もちろん各条件はこれに限定されるものではなく、更に各線速における評価時にはそれぞれに最適化して使用した。
【００１３】
【表１】
実施例２
実施例１で用いたのと同じ、従来ストラテジで約３倍速までの記録線速において記録が可能な光記録媒体を用い、記録線速を５倍速にし、記録マーク部のＰｗのパルスデューティ比を０．５に固定し、スペース部のＰｅ＋のパルスデューティ比を変化させて記録を行った例を表２に、スペース部のＰｅ＋のパルスデューティ比を０．２５に固定し、記録マーク部のＰｗのパルスデューティ比を変化させて評価した例を表３に示す。評価はＤＯＷ１のジッタ特性をモニタすることで行った。Ｐｗ及びＰｅ＋のパワー条件は実施例１と同じにした。
その結果、表２に示すように、Ｐｅ＋のパルスデューティ比が０．１５〜０．３の範囲ではジッタが９％以下と良好であったが、媒体の記録層材料などの変更を考慮した実験では、最適中心値がＰｅ＋のパルスデューティ比で約０．１変化する場合があることから、Ｐｅ＋のパルスデューティ比は、０．０５〜０．４の範囲が好ましい。
また、Ｐｗのパルスデューティ比は０．４〜０．６のとき良い結果が得られたが、上記と同様に媒体の記録層材料などの変更分が０．２あり、これを考慮すると０．２〜０．８の範囲が良い。
【００１５】
【表２】
【表３】
実施例３
実施例１と同じ光記録媒体を用いて、Ｐｗを１８ｍＷに固定し、Ｐｅ＋のパワーを表４のように変化させて、ＤＯＷ１ジッタ及び反射率のＰｅ＋依存性を評価した。パルスの条件は実施例１と同じである。結果を表４に示した。
この光記録媒体を用いた場合、Ｐｅ＋が１６ｍＷ以上のパワー条件になるとジッタが測定できなくなる。また反射率が極端に低下するため、このパワー条件においては記録層材料が溶融し、アモルファス相に変化してしまうことが予想される。従って、Ｐｅ＋は１６ｍＷ未満のパワー条件とする必要がある。
相変化記録材料の記録再生原理としては、レーザ光などのエネルギービームを記録層材料で吸収し、記録層材料のビーム照射された部分が加熱溶融された状態を経て急冷されることにより、溶融状態の構造がそのまま固化し、その結果形成されるアモルファス相が記録マークとして保存される。再生は、記録マークとそれ以外のスペース部分の結晶相との光学定数による反射率差を利用して光ビームにより読み取るものである。一般に相変化型光記録媒体においては、記録マークが低反射率、スペース部が高反射率となるように設計されている。
記録マークを形成する際には、材料の溶融と急冷条件が必須であるため、高パワーのエネルギーパルスを照射して行うが、一方で記録マークを消去（結晶化）する際には、記録材料の結晶化温度以上に材料固有の一定時間以上保持することによって達成されるため、通常は材料の結晶化温度以上融点以下に記録層が加熱されるような連続的なエネルギービームを照射することによって行う。
現在の光ディスクシステムにおいて、消去はダイレクトオーバーライトにより実施され、具体的には、図３に示すような光ビームで記録消去を同時に実施しているが、消去はＰｅの部分で行われることになる。
このＰｅの条件が材料の融点以上になるようなパワー設定になると、ビームが移動した際にアモルファス相が形成されるような急冷条件となってしまい、スペース部分にアモルファスが形成され、結果的にスペース部の反射率低下を引き起してしまう。従って、消去は材料の融点以下に設定する必要があり、本実施例においては、この臨界条件が１６ｍＷ程度であると推測される。
また、Ｐｅ＝６ｍＷの条件でＰｅ＋を変化させて記録実験を行った場合には、Ｐｅ＋が７．５ｍＷ以上１６ｍＷ未満の条件まではジッタ低減の効果が認められた。この条件については更に検討が必要と考えるが、実験からはＰｅ＋はＰｅの１５％〜１６６％高いパワー条件が必要である。
【００１８】
【表４】
実施例４
実施例１と同じ媒体を用い、Ｐｅ＋をＰｗと同じ１８ｍＷとし、Ｐｗのパルスデューティ比を０．５に固定し、Ｐｅ＋のパルスデューティ比を変化させて記録テストを行った。結果を表５に示すが、パルスデューティ比０．２以下では反射率低下が抑えられる結果となり、ジッタ評価も良好であった。実施例２の場合と同様に、媒体の記録層材料などの変更ではＰｅ＋のパルスデューティ比に０．１程度のばらつきがあるため、Ｐｅ＋のパルスデューティ比が０．３以下の条件であっても本発明１に示す記録ストラテジの効果が確認された。
この結果は、実施例３で説明した０．２５以上のパルスデューティとした消去動作においては、パワー条件は融点以上の設定値であるが、照射されるエネルギーパルスが十分に短い場合には、記録材料層が融点まで達しない領域があることを示している。
本実施例において示す記録型のＤＶＤの例では、パルスデューティ０．３以下望ましくは０．２以下の条件範囲がこの範囲内にあるといえる。
更に、Ｐｅ＋とＰｗを同じ設定にできれば記録装置の設定値が１条件軽減されることになるため、記録装置の製造、及び調整上の負担が軽減される効果もある。
【００２０】
【表５】
実施例５
実施例１と同じ媒体を用い、Ｐｅを変化させてテストを行った。Ｐｗ、Ｐｅ＋の条件は実施例１と同様にした。本実施例の場合、良好な結果を与えるＰｅのパワー範囲はＰｗの０．３±０．０３倍程度であった。媒体の記録層材料などの変更では中心値が０．０７５倍程度変動するため、ＰｅはＰｗの０．２〜０．４倍のパワーレベルが良い。
【００２２】
実施例６
実施例１に示すように、従来の記録ストラテジでは３倍速の記録スピードまでしか再生に充分な記録特性が得られないような記録媒体でも、本発明の記録ストラテジを用いることによって消去性能が向上し、５倍速までの記録が可能になることを示したが、このように記録ストラテジを変更して記録スピードの向上を図る場合であって、例えば１２０ｍｍφの記録媒体を使って２倍速から４．８倍速のＣＡＶ記録を行おうとすると、記録装置は、媒体に情報を記録する際に３倍速の記録線速となる半径位置において、この位置より内周側においては従来と同じ記録ストラテジを用いて記録を行い、外周側では本発明のスペース部を変調して記録を行う記録ストラテジにより記録を行うようにする必要がある。このような記録ストラテジを変更して媒体全面に記録を行うようにしようとする場合には、記録媒体に記録ストラテジの条件と記録ストラテジの変更を行う線速条件（予め決められた記録線速）として半径位置やアドレス情報などを予め情報として記録しておき、それを装置が読み取り、予め条件を設定しておくように制御する必要がある。なお、本実施例では、予め決められた記録線速は３倍速である。
本実施例においては、光記録媒体に予め情報を記録する方法として、記録媒体に予め形成しておく案内溝に、ある周期のウォブルを形成し、記録可能線速範囲と本発明６の記録ストラテジ条件とその切り替え線速をデータ化し、上記ウォブルの位相を反転することによって入力するようにした。この情報のエリアは、データエリアの内周側、通常ＤＶＤなどにおいては半径２４ｍｍがデータ領域であるので、これより内周側に設置した。
この媒体を記録装置に導入した場合、記録装置がこの情報を読み取り、適切な記録線速と記録ストラテジを設定できるようになり、安定した記録システムを実現できた。
この方法以外に媒体にデータを入力する手段としては、ＲＯＭに用いられているようなピットを用いる方法も使用可能である。
【００２３】
【発明の効果】
本発明１〜３によれば、高速記録時のオーバーライト特性を改善でき、従来の光記録媒体を更に高線速で記録できる記録方法を確実に設定できる。
本発明４によれば、従来よりも改善された広い線速範囲で記録可能な光ディスクシステムを実現できる。
本発明５によれば、安定した記録システムを実現可能な光記録媒体を提供できる。
【図面の簡単な説明】
【図１】本発明に関連する書き換え型の相変化型光記録媒体の説明図。
（ａ） 斜視図
（ｂ） （ａ）の切り欠き部の断面図
【図２】本発明の記録方法の概略例を示す図。
【図３】特開平９−１３８９４７号公報記載の記録ストラテジを示す図。
【図４】実施例１の５倍速条件でのオバーライト特性の結果を示す図。
【符号の説明】
Ｐｗ 記録パワー
Ｐｅ 消去パワー
Ｐｂ ボトムパワー
Ｐｅ＋ オーバーライト時のスペース部において消去エネルギーを与えるパワー
Ｔｗ チャネル周期
ＤＯＷ ダイレクト・オーバー・ライト[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phase change optical recording medium capable of recording and reproducing information by irradiating a light beam to cause an optical change in a recording layer material, and to rewrite the information, and a recording method thereof. .
[0002]
[Prior art]
As an invention related to the present invention, there is one related to Japanese Patent Laid-Open No. 5-151572 (registered), and the format of the recording strategy is similar to the present invention, but the technical idea is different and the setting range of the power level is also It is different.
Japanese Patent Laid-Open No. 9-138947 (registered) discloses an invention that uses the recording strategy shown in FIG. 3 and defines the pulse width and the like for the purpose of application to CD-RW.
Japanese Patent Application Laid-Open No. 11-115313 discloses an invention of an optical recording medium adopting an optical disc design method using a conventional recording method and having a recrystallization upper limit linear velocity of 2.5 to 5.0 m / s. Is disclosed.
[0003]
A phase change type optical recording medium using an AgInSbTe-based alloy as a recording material conventionally used for CD-RW, DVD + RW, DVD-RW, and the like is designed as shown in JP-A-11-115313. As a design guideline, the linear velocity range below the linear velocity has been set as the recordable linear velocity range with respect to the linear velocity at which the reflectance changes from the high level to the low level so that the recording method does not need to be complicated. .
However, as recently high recording linear velocities and wider recordable linear velocities are required, there is a problem that the storage reliability of the recording marks is reduced only by increasing the recording linear velocity by the material. Becomes apparent.
[0004]
The present inventors provide an optical recording medium capable of obtaining sufficient overwrite characteristics in a recordable linear velocity range that is higher than the conventional designed linear velocity range and sufficiently ensuring the storage reliability of a recording mark, and a recording method thereof. As an object, an optical recording medium having at least a phase change recording layer and a reflective layer on a substrate and having a recording linear velocity range at least higher than a recording linear velocity range capable of overwriting by CAV recording, and optimal on the low speed side Phase change that exists within the recordable linear velocity range in which the linear velocity at which the reflectivity starts to decrease due to continuous irradiation of laser light higher than the erasing power (Pe lo ) with which excellent overwrite characteristics can be obtained (reflectance reduced linear velocity) Type optical recording medium, and linear velocity at which the reflectance starts to decrease due to continuous irradiation of laser light of an erasing power (Pe lo ) or higher that provides optimum overwriting characteristics on the low speed side ( The erasing power (Pe lo ) is set to 0.4 times or more of the recording power (Pw) at a recording linear velocity below the reflectance decreasing linear velocity, and at a recording linear velocity higher than this. Has invented a recording method for a phase-change optical recording medium in which the average value of the erasing power (Pe high ) is set to be less than 0.4 times the recording power (Pw) (hereinafter referred to as Invention A), and has been filed separately (in Japanese). Application No. 2002-220385).
[0005]
According to the invention A, a phase change optical recording medium capable of high linear velocity recording and a recording method thereof can be obtained. However, the present invention further improves the recording method, and even when the same optical recording medium is used, A recording method capable of high-speed recording is provided.
Specifically, a DVD will be described as an example. A linear velocity range that can be recorded by a conventional recording method described in Japanese Patent Laid-Open No. 9-138947 using an optical recording medium created by a design method described in Japanese Patent Laid-Open No. 11-115313. Is about 9 m / s, a recording line of about 12.5 m / s can be obtained by using the same recording material as the optical recording medium, designing the medium as in invention A, and recording using the recording method of invention A. An optical recording medium corresponding to the speed can be obtained.
[0006]
However, when recording is performed at a speed of 12.5 m / s or more using the recording method of the invention A, it is possible to record up to a considerably fast linear velocity area for the first recording, but the first overwriting is performed for overwriting. As a result, there arises a problem that the jitter characteristics deteriorate rapidly. This is a phenomenon that occurs because the recorded mark cannot be sufficiently erased.
The invention A is a very good method for the purpose of expanding the recording linear velocity range in a system that does not like a change in the recording strategy for the purpose of performing CAV recording or the like. There is room. In other words, the method of the invention A is characterized in that the erasing power Pe is set low in order to enable recording on the high linear velocity side. However, when trying to increase the speed, Pe is further reduced. It is necessary to continue. If the Pe level becomes too small, the recorded mark cannot be erased and remains in the space portion.
[0007]
On the other hand, if the recording system of the present invention is used, the energy necessary for erasing can be supplied by arranging Pe + in the form of pulses in the Pe region, and if it is repaired with a low level of Pe to obtain a better crystalline state. That's good. Although this idea seems to be similar to the invention described in Japanese Patent Laid-Open No. 5-151572 (hereinafter referred to as Invention B), the pulse duty ratio of Invention B is calculated as 0.5 to 0.75. On the other hand, in the present invention, as will be described later, good results can be obtained when the pulse duty ratio of Pe + is 0.5 or less. Therefore, both inventions are considered to be different inventions.
Further, in the invention B, it can be determined that the power level after the pulse is almost zero level, whereas in the present invention, the power level Pe after the pulse is a region for controlling the crystal state, so that the power level is constant. A level is required, which is different from the erase pulse of Invention B.
Presumably, in invention B, pulse erasing is used for the purpose of preventing temperature fluctuations during erasing.
[0008]
[Problems to be solved by the invention]
The present invention provides a recording method for a phase change optical recording medium in which overwriting characteristics are improved when recording at a higher speed than before, and a phase change optical recording medium suitable for carrying out the recording method. Objective.
[0009]
[Means for Solving the Problems]
The above problems are solved by the following inventions 1) to 5 ) (hereinafter referred to as the present inventions 1 to 5 ).
1) When forming a recording mark on a phase change optical recording medium having at least a phase change recording layer and a reflective layer on a substrate, the light emission waveform of a light beam such as a laser beam used for recording is a recording pulse train composed of a plurality of pulses. In this method, recording is performed by modulating the pulse train, wherein the recording mark portion is a pulse train modulated between the recording power (Pw) and the bottom power (Pb), and the space portion is erased with the recording power (Pw). A pulse train modulated between the power (Pe +) set to a level between the power (Pe) and the erasing power (Pe) is used, and the pulse duty ratio of Pw of the recording mark portion is 0.2 to 0.8 in advance. A recording method for a phase change optical recording medium, wherein the range is set, and the pulse duty ratio of Pe + in the space portion is set in a range of 0.05 to 0.4 in advance.
2 ) When forming a recording mark on a phase change optical recording medium having at least a phase change recording layer and a reflective layer on a substrate, a light emission waveform of a light beam such as a laser beam used for recording is a recording pulse train composed of a plurality of pulses. In this method, recording is performed by modulating the pulse train, wherein the recording mark portion is a pulse train modulated between the recording power (Pw) and the bottom power (Pb), and the space portion is erased with the recording power (Pw). When a pulse train modulated between the power (Pe +) and the erasing power (Pe) set at a level between the powers (Pe) and the pulse duty ratio of Pe + is 0.3 or more, the light beam is irradiated. When the power condition in which the phase change recording layer is equal to or higher than the melting point of the recording material is used as Pe +, the pulse duty ratio of Pe + in the space portion is less than 0.3. Recording method of the phase-change optical recording medium, characterized by.
3 ) The recording method for a phase change optical recording medium according to 1) or 2) , wherein Pe is 0.2 to 0.4 times the optimum recording power Pw for forming a recording mark.
4 ) When the recording linear velocity is higher than a predetermined recording linear velocity, the recording method described in any one of 1) to 3 ) is used. When the recording linear velocity is lower than the predetermined recording linear velocity, the space portion is not modulated. A recording method for a phase change optical recording medium, characterized in that the continuous light of Pe is determined in advance.
5 ) A phase change type optical recording medium, wherein a recording linear velocity (predetermined recording linear velocity) for changing a recording strategy in the recording method described in 4 ) is recorded as recording method setting information.
[0010]
Hereinafter, the present invention will be described in detail.
FIG. 1 is an explanatory diagram of a rewritable phase change optical recording medium related to the present invention. Fig.1 (a) is a perspective view and has shown the state partly notched. FIG.1 (b) is sectional drawing of this notch part.
The recording layer is usually in a crystalline phase (erased state) by initialization. Then, irradiation with a light beam modulated by the recording method of the present invention forms an amorphous recording mark in the recording layer.
FIG. 2 shows a schematic example of the recording method of the present invention.
In the recording method of the present invention, a pair of a power Pe + pulse for providing erasing energy in the space portion at the time of overwriting and a Pe power level for controlling the erasing level are paired, and good erasing characteristics can be obtained even at a higher recording linear velocity. can get.
[0011]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.
[0012]
Example 1
When recording is performed using the recording strategy described in Japanese Patent Laid-Open No. 9-138947 as shown in FIG. 3, the Pe level is changed with respect to an optical recording medium capable of recording at a recording linear velocity up to about 3 × speed. Table 1 shows the jitter characteristics obtained when recording is performed using the recording method of the invention A and when recording is performed using the recording strategy of the present invention.
The jitter characteristic was evaluated by the mark edge variation σ / Tw (in%) with respect to the channel period Tw, and the measured value was described.
As the phase change type optical recording medium, the one corresponding to the recording of the DVD density was used, and the result of overwriting up to 100 times using the pickup device for DVD having a wavelength of 660 nm and NA of 0.65 was shown. The recording speed was 1, 2, 4, and 5 times the speed of DVD.
In particular, the result of the overlight characteristic under the 5 × speed condition is shown in FIG. 4 using a graph. When recording is performed by using the recording method of the invention A (strategy A), the overwrite characteristic, particularly the DOW1 jitter increases significantly, and the lack of erasure of the space portion becomes remarkable at the number of overwriting times. confirmed.
On the other hand, as a result of using the recording strategy (improved strategy) of the present invention, the increase in jitter was alleviated even during this overwrite repetition, and the effectiveness of the recording strategy of the present invention was confirmed.
At this time, each condition of the 5 × speed recording strategy was basically set as follows.
First, the power of the laser beam was Pw = 18 mW, Pe + = 12 mW, and Pe = 6 mW.
The pulse duty ratio of Pw in the recording mark portion was about 0.5, the pulse duty ratio of Pe + in the space portion was 0.25, and the frequency was changed according to the channel frequency of the DVD for each linear velocity.
Of course, each condition is not limited to this, and further, optimized at the time of evaluation at each linear velocity.
[0013]
[Table 1]
Example 2
The same optical recording medium that can be recorded at a recording linear velocity of up to about 3 × speed with the conventional strategy, the recording linear velocity is set to 5 ×, and the pulse duty ratio of Pw of the recording mark portion is set to the same as used in the first embodiment. Table 2 shows an example in which recording was performed by changing the pulse duty ratio of Pe + in the space portion and fixed to 0.5, and the pulse duty ratio of Pe + in the space portion was fixed to 0.25. Table 3 shows an example in which the pulse duty ratio is changed and evaluated. The evaluation was performed by monitoring the jitter characteristics of DOW1. The power conditions of Pw and Pe + were the same as in Example 1.
As a result, as shown in Table 2, when the pulse duty ratio of Pe + was in the range of 0.15 to 0.3, the jitter was as good as 9% or less. However, the experiment considering changes in the recording layer material of the medium Then, since the optimum center value may change by about 0.1 at the pulse duty ratio of Pe +, the pulse duty ratio of Pe + is preferably in the range of 0.05 to 0.4.
Also, good results were obtained when the pulse duty ratio of Pw was 0.4 to 0.6, but there were 0.2 changes in the recording layer material of the medium in the same manner as described above. A range of 2 to 0.8 is good.
[0015]
[Table 2]
[Table 3]
Example 3
Using the same optical recording medium as in Example 1, Pw was fixed at 18 mW, and the power of Pe + was changed as shown in Table 4 to evaluate the dependence of DOW1 jitter and reflectance on Pe +. The pulse conditions are the same as in the first embodiment. The results are shown in Table 4.
When this optical recording medium is used, jitter cannot be measured when the power condition of Pe + is 16 mW or more. Further, since the reflectance is extremely lowered, it is expected that the recording layer material melts and changes to an amorphous phase under this power condition. Therefore, Pe + needs to have a power condition of less than 16 mW.
The principle of recording and playback of phase change recording materials is that the energy layer such as laser light is absorbed by the recording layer material, and the irradiated portion of the recording layer material is rapidly cooled after being heated and melted, so that the molten state The structure is solidified as it is, and the resulting amorphous phase is stored as a recording mark. The reproduction is performed by reading with a light beam using a difference in reflectance due to an optical constant between the recording mark and the crystal phase of the other space portion. In general, a phase change optical recording medium is designed so that a recording mark has a low reflectance and a space portion has a high reflectance.
When forming a recording mark, it is necessary to irradiate a high-power energy pulse because the material must be melted and rapidly cooled. On the other hand, when erasing (crystallizing) the recording mark, the recording material is used. This is achieved by holding the material for a certain time longer than the crystallization temperature of the material, and usually by irradiating a continuous energy beam that heats the recording layer to the melting point of the material or higher and below the melting point. Do.
In the current optical disk system, erasing is performed by direct overwriting. Specifically, recording erasing is simultaneously performed with a light beam as shown in FIG. 3, but erasing is performed in the portion of Pe. .
When the power setting is such that the condition of Pe is equal to or higher than the melting point of the material, it becomes a rapid cooling condition in which an amorphous phase is formed when the beam moves, and amorphous is formed in the space portion. This will cause a drop in the reflectivity of the space portion. Therefore, it is necessary to set the erasure below the melting point of the material. In this embodiment, it is estimated that this critical condition is about 16 mW.
Further, when the recording experiment was performed by changing Pe + under the condition of Pe = 6 mW, the effect of reducing jitter was recognized up to the condition where Pe + was 7.5 mW or more and less than 16 mW. Although it is considered that further examination is necessary for this condition, it is necessary from the experiment that the power condition of Pe + is 15% to 166% higher than Pe.
[0018]
[Table 4]
Example 4
Using the same medium as in Example 1, Pe + was set to 18 mW same as Pw, the pulse duty ratio of Pw was fixed to 0.5, and the recording test was performed by changing the pulse duty ratio of Pe +. The results are shown in Table 5, and when the pulse duty ratio is 0.2 or less, the reflectance is suppressed from being lowered, and the jitter evaluation is good. As in the case of the second embodiment, when the recording layer material of the medium is changed, there is a variation of about 0.1 in the pulse duty ratio of Pe +, so even if the pulse duty ratio of Pe + is 0.3 or less. The effect of the recording strategy shown in the present invention 1 was confirmed.
As a result, in the erasing operation with a pulse duty of 0.25 or more described in the third embodiment, the power condition is a set value equal to or higher than the melting point, but if the irradiated energy pulse is sufficiently short, the recording is performed. This indicates that there is a region where the material layer does not reach the melting point.
In the example of the recordable DVD shown in this embodiment, it can be said that the condition range of the pulse duty of 0.3 or less, preferably 0.2 or less is within this range.
Furthermore, if Pe + and Pw can be set to the same setting, the setting value of the recording apparatus is reduced by one condition, so that the burden on manufacturing and adjustment of the recording apparatus is also reduced.
[0020]
[Table 5]
Example 5
A test was performed using the same medium as in Example 1 with changing Pe. The conditions for Pw and Pe + were the same as in Example 1. In the case of this example, the power range of Pe that gave good results was about 0.3 ± 0.03 times Pw. When the recording layer material of the medium is changed, the center value fluctuates about 0.075 times, so that Pe has a power level of 0.2 to 0.4 times Pw.
[0022]
Example 6
As shown in the first embodiment, the erasing performance is improved by using the recording strategy of the present invention even on a recording medium in which recording characteristics sufficient for reproduction can be obtained only up to a recording speed of 3 × speed with the conventional recording strategy. Although it has been shown that recording up to 5 × speed is possible, the recording strategy is changed in this way to improve the recording speed. For example, a recording medium of 120 mmφ is used to increase the recording speed from 2 × to 4.8. When attempting to perform double speed CAV recording, the recording apparatus uses the same recording strategy as the conventional one at the radial position where the recording linear speed is triple speed when recording information on the medium. In the outer peripheral side, it is necessary to perform recording by a recording strategy for recording by modulating the space portion of the present invention. When recording is performed on the entire surface of the medium by changing such a recording strategy, the recording strategy condition on the recording medium and the linear velocity condition for changing the recording strategy (predetermined recording linear velocity) It is necessary to control such that the radius position, address information, and the like are recorded as information in advance, read by the apparatus, and conditions are set in advance. In this embodiment, the predetermined recording linear velocity is triple speed.
In this embodiment, as a method of recording information in advance on the optical recording medium, a wobble having a certain period is formed in a guide groove formed in advance on the recording medium, and the recordable linear velocity range and the recording strategy of the sixth aspect of the present invention are recorded. The condition and the switching linear velocity were converted into data and input by inverting the wobble phase. This information area is set on the inner circumference side of the data area, since a radius of 24 mm is a data area in a normal DVD or the like.
When this medium is introduced into a recording apparatus, the recording apparatus can read this information and set an appropriate recording linear velocity and recording strategy, thereby realizing a stable recording system.
In addition to this method, as a means for inputting data to the medium, a method using pits as used in a ROM can be used.
[0023]
【The invention's effect】
According to the first to third aspects of the present invention, it is possible to improve the overwrite characteristics during high-speed recording, and to reliably set a recording method capable of recording a conventional optical recording medium at a higher linear velocity.
According to the fourth aspect of the present invention, it is possible to realize an optical disc system capable of recording in a wide linear velocity range, which is improved as compared with the prior art.
According to the fifth aspect of the present invention, an optical recording medium capable of realizing a stable recording system can be provided.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a rewritable phase change optical recording medium related to the present invention.
(A) Perspective view (b) Cross-sectional view of a notch portion in (a). FIG. 2 is a diagram showing a schematic example of a recording method of the present invention.
FIG. 3 is a diagram showing a recording strategy described in Japanese Patent Laid-Open No. 9-138947.
4 is a graph showing the result of overlight characteristics under a 5 × speed condition in Example 1. FIG.
[Explanation of symbols]
Pw Recording power Pe Erase power Pb Bottom power Pe + Power to give erase energy in the space portion at the time of overwriting Tw Channel period DOW Direct overwriting
Claims (5)
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| JP2002220471A JP3989789B2 (en) | 2002-07-29 | 2002-07-29 | Phase change optical recording medium and recording method thereof |
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| JP2002220471A JP3989789B2 (en) | 2002-07-29 | 2002-07-29 | Phase change optical recording medium and recording method thereof |
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| JP2006209935A (en) | 2004-12-28 | 2006-08-10 | Victor Co Of Japan Ltd | Optical recording method, optical recording apparatus and optical recording medium |
| TWI328807B (en) | 2005-03-02 | 2010-08-11 | Ricoh Co Ltd | Optical recording medium, multi-layered optical recording medium, and optical recording method and recording apparatus using the same |
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