JP2004199756A - Information recording/reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain satisfactory recording characteristics by a practical driving device even during high-speed writing in a 1T strategy method. <P>SOLUTION: Recording parameters Pind, γ target, ρ and ε enabling acquisition of optimal recording characteristics by a standard recording/reproducing device are recorded beforehand in an information recording medium, and conversion coefficients A1 (or B1) and A2 (or B2) enabling acquisition of optimal recording characteristics by a recording/reproducing device having a recording pulse width Tmp different from that of the standard recording/reproducing device, i.e., the coefficients of the linear expressions of P target-Tmp and optimal recording power Po-Tmp characteristics represented by linear relations are recorded. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

で設定される。よって、ｄＴtopaは、
ｄＴtopa＝ｄＴtops×（Ｔmpa/Ｔmps）
である。
【００３２】
次に、ｄＴeraは記録したマークの後のスペースの立上り位置を設定するものであるが、この立上り位置はＴmpによらず同じとするために、ｄＴeraは一定に設定される。
【００３３】
以上より、実用化ドライブに搭載可能なレーザーダイオード及び駆動装置で実現可能な記録パルス巾Ｔmpaでの記録時に必要な記録パラメータは、標準評価装置で設定された、Ｔmp、ｄＴtop、ｄＴera、Ｐind、γtarget、ρ、ε、及び変換係数Ａ₁（またはＢ₁）、Ａ₂（またはＢ₂）である。
【００３４】
ここで、Ｐindは、記録パルス巾ＴmpsのときのＰtarget（＝Ｐtargets）をそのまま用いることはできない。なぜなら、これらのパラメータはＣＤ−ＲＷの規格書で規定されるATIP（Absolute Time In Pre-groove）のATIＰExtra Information のAdditional Informationに記録することで実用記録装置（CD-R/RWドライブ）で利用されることが可能となるが、メディアに記録する場合には用意された離散的な値を用いなければならないからである。この結果、ＰindはＰtargetsから若干の誤差を生じるので、Ｐtargeta、ρaも若干の誤差を生じることになる。
【００３５】
以上の説明では記録パラメータの数を少なくするために、必要な変換係数を、Ａ₁、Ｂ₁のうちのいずれか１つとＡ₂、Ｂ₂のうちのいずれか１つの計２つとしているが、Ｐtargeta、ρaを求めるのにＡ₁、Ｂ₁、Ａ₂、Ｂ₂の４つのパラメータを使いＰindを用いない記録パラメータの設定を行なうことも可能である。この場合はメディアに記録するパラメータは増えるがＰtargeta、ρaを求める時の演算処理が簡単になる。
【００３６】
【発明の実施の形態】
以下、図面に基づいて本発明の実施の形態を説明する。
本発明の情報記録再生方法を用いた第１の実施の形態を説明する。対象となる情報記録媒体は、例えばＣＤ−ＲＷ、ＤＶＤ−ＲＡＭ、ＤＶＤ−ＲＷ、ＤＶＤ＋ＲＷ、ＰＤ等の書換え可能な相変化型光情報記録媒体であり、記録再生波長領域で略透明である基板上に、少なくとも記録層と反射層を有する。
【００３７】
図２は、書換え可能な相変化型光情報記録媒体の構成の一例を示すもので、透明基板１上に、下部保護層２、記録層３、上部保護層４、反射層５、樹脂層６が順次積層されている。
透明基板１の材料としては、記録・再生波長領域でほぼ透明であると同時にディスクの機械的強度を確保できるものが望ましく、ガラス、樹脂等が挙げられるが、コスト、強度、透明性の点からポリカーボネート樹脂を用いるのが一般的であり、好ましい。基板１上には光ビームの走査を容易にするための案内溝（グルーブ）を形成してもよい。
【００３８】
記録層３の材料としては相変化材料を用いる。相変化材料としては、可逆的に変化する２つ以上の相を有する材料である必要があり、例えば結晶−アモルファス間で相変化する材料が挙げられる。情報の記録は、結晶状態の中にアモルファスマークを形成するか、またはアモルファス状態の中に結晶のマークを形成することで行われる。
【００３９】
反射層５としては任意の金属または合金を用いることができる。反射層材料の例としては、Ａｕ、Ａｇ、Ｃｕ、Ａｌまたはそれらの合金などが挙げられる。
【００４０】
記録層３の上下には保護層を設けるのが一般的である。保護層は記録層３にかかる熱から樹脂基板１を保護する下部保護層２と、記録層３の原子の反射層５への熱拡散を防止するため、及び記録層に効率的に熱エネルギーが掛かるようにするために形成する上部保護層４とがある。下部保護層２は、基板１と記録層３の間に形成され、熱的特性または光学的特性から複数層を積層した多層膜でもよい。上部保護層４は記録層３と反射層５の間に形成され、下部保護層２と同様に熱的・光学的特性または化学的特性から多層構造としてもよい。保護層材料としては、任意の誘電体、半導体、半金属またはそれらの物質の混合物が挙げられる。反射層５の上には、上記の各層を機械的・化学的損傷から保護する樹脂層（オーバーコート層）６を設けてもよく、また樹脂基板等を貼り合わせてもよい。
【００４１】
上記光情報記録媒体への情報の記録及び再生は、記録層３の近傍に集光した光ビームを走査することにより行われる。本発明の情報記録再生方法は、マークの長さ及びマーク間（スペース）の長さを、基本クロック周期Ｔを最小単位として変動させて情報を記録するＰWＭ方式に適用される。このＰWＭ方式においては、強度変調した光を照射して、基本クロック周期Ｔの整数倍（ｎ・Ｔ）の長さのマーク及びスペースが形成される。照射の強度は３レベルであり、それぞれ記録パワーＰw、消去パワーＰe、バイアスパワーＰbで表され、Ｐw＞Ｐe＞Ｐbの関係にある。マークを記録するときは、記録パワー（ピークパワー）Ｐw、バイアスパワー（ボトムパワー）Ｐbのパルス発光を行い、スペースを記録（またはマークを消去）するときは、消去パワーＰeのＣＷ発光を行う。すなわち、記録パワーＰwとバイアスパワーＰbのパルス光を照射して記録層材料を加熱・急冷することにより、アモルファスマークの形成が行われ、消去パワーＰeのＣＷ発光して記録層材料を加熱・徐冷することにより、結晶状態のスペースが形成される。
【００４２】
このようなマーク形成には、図１に示すようなＣＤ−ＲＷの規格書で規定されている1Ｔストラテジ法のパルス発光パターンが用いられる。このパルス発光パターンにおいて、マルチパルスの記録パルス巾Ｔmpは固定されているが、EFMデータ信号の立上がりから１Ｔ後の位置より先頭パルの立上がりまでの時間であるｄＴtop、EFMデータ信号の立下り位置から消去パワーＰeの立上がるまでの時間ｄＴeraは記録媒体に合わせて設定される。
【００４３】
まず、標準評価装置により最適なストラテジを探し、Ｔmp、ｄＴtop、ｄＴeraが設定される。また、γ法におけるγtarget、及び消去パワーＰeを決定するためのεも設定される。次に、変調度ｍと記録パワーＰwの関係を求めることにより、
γ＝(Δｍ/ｍ)／(ΔＰw/Ｐw）
におけるγ＝γtargetのときの記録パワーＰw（＝Ｐtarget）からＰindが設定される。また、再生信号のジッターとＰwの関係を求めることにより、ジッターの最小値での記録パワーＰwを最適記録パワーＰoとして、ρ（＝Ｐo／Ｐind）が設定される。
【００４４】
さらに、γ＝γtargetのときの記録パワーＰtargetと記録パルス巾Ｔmpの図３（ａ）に示すような直線関係を求めて、次式
Ｐtarget＝Ａ₁×Ｔmp+Ｂ₁
における変換係数Ａ₁及びＢ₁のいずれかの変換係数が設定される。
【００４５】
また、ジッターの最小値での最適記録パワーＰoと記録パルス巾Ｔmpの図３（ｂ）に示すような直線関係を求めて、次式
Ｐo＝Ａ₂×Ｔmp+Ｂ₂
における変換係数Ａ₂及びＢ₂のどちらか一方が設定される。
【００４６】
上記のようにして標準評価装置で設定されたＴmp、ｄＴtop、ｄＴera、Ｐind、γtarget、ρ、ε、及び変換係数Ａ₁（またはＢ₁）、Ａ₂（またはＢ₂）が、光情報記録媒体に予め記録される。
【００４７】
上記設定値が予め記録された光情報記録媒体に、標準評価装置で最適化された記録パルス巾Ｔmpとは異なる記録パルス巾Ｔmpを有する記録再生装置にて情報を記録する場合には、以下のプロセスにて記録条件が設定される。ここで、両者の記録条件を識別するために、標準評価装置で最適化された記録パルス巾ＴmpをＴmpsとし、このＴmpsに対応するｄＴtop、ｄＴera、Ｐtarget、ρ、εを、それぞれｄＴtops、ｄＴeras、Ｐtargets、ρs、εsとする一方、記録再生装置での記録パルス巾ＴmpをＴmpa（Ｔmps＜Ｔmpa）とし、このＴmpsに対応するｄＴtop、ｄＴera、Ｐtarget、ρ、εを、それぞれｄＴtopa、ｄＴeraa、Ｐtargeta、ρa、εaとして説明する。
【００４８】
ｄＴeraとεは、記録パルス巾Ｔmpによらず一定であり、ｄＴeraa＝ｄＴeras、εa＝εsであるが、ｄＴtopa、Ｐtargeta、ρaは、記録パルス巾Ｔmpsに対して設定された記録パラメータｄＴtops、Ｐind、ρs、Ａ₁（またはＢ₁）、Ａ₂（またはＢ₂）を用いて算出される。
【００４９】
ｄＴtopaは、次式

より、
ｄＴtopa＝dＴtops×Ｔmpa/Ｔmps
が成立し、記録パルス巾Ｔmpaと、設定値Ｔmps、dＴtopsにより算出される。
【００５０】
γ＝γtargetのときの記録パルス巾ＴmpaでのＰtargetaは、次式
Ｐtargeta＝Ａ₁×Ｔmpa+Ｂ₁
の関係を満たすため、Ａ₁が設定されている場合には、Ｂ₁に
Ｐtargets＝Ａ₁×Ｔmps+Ｂ₁
からの
Ｂ₁＝Ｐtargets−Ａ₁×Ｔmps
を用いることにより、既知データから容易に算出される。なお、ここではＰtargetsとして設定値Ｐindが適用される。また、Ｂ₁が設定されている場合には、Ａ₁には
Ａ₁＝（Ｐtargets−Ｂ₁）／Ｔmps
が用いられる。このようにして算出されたＰtargetaは、記録パルス巾ＴmpaでのＰindとされる。
【００５１】
ρaは、
ρa＝Ｐｏ／Ｐtargeta
であり、この場合の最適記録パワーＰｏは、次式
Ｐｏ＝Ａ₂×Ｔmpa+Ｂ₂
で表されるため、
ρa＝（Ａ₂×Ｔmpa+Ｂ₂）／(Ａ₁×Ｔmpa+Ｂ₁)
となる。ここで、Ａ₂が設定されている場合には、Ｂ₂は、次式
ρs＝（Ａ₂×Ｔmps+Ｂ₂）／(Ａ₁×Ｔmps+Ｂ₁)
より、
Ｂ₂＝ρs×(Ａ₁×Ｔmps+Ｂ₁)−（Ａ₂×Ｔmps）
となるので、ρaはρs、Ｔmps、Ａ₂、Ａ₁、Ｂ₁より容易に算出される。なお、Ａ₁、Ｂ₁のいずれか一方は、前述したように設定値から算出された値である。また、Ｂ₂が設定されている場合には、Ａ₂は、
Ａ₂＝｛ρs×(Ａ₁×Ｔmps+Ｂ₁)−Ｂ₂｝／Ｔmps
より求められる。
【００５２】
以上の説明からも明らかように、本実施の形態においては、標準評価装置により最適化された記録パラメータＴmp、ｄＴtop、ｄＴera、Ｐind、γtarget、ρ、ε、変換係数Ａ₁（またはＢ₁）、Ａ₂（またはＢ₂）を光情報記録媒体に予め記録しておくことにより、記録パルス巾の異なる記録再生装置にて最適な記録特性が得られる記録条件を容易に設定することができ、基本クロック周波数が１００ＭＨｚを超える高速書き込みでも、従来の立上り・立下り時間を有する発光光源(レーザーダイオードとその駆動装置)を用いた記録再生装置で充分な記録特性を得ることが可能となる。
【００５３】
次に、本発明の情報記録再生方法を用いた第２の実施の形態を説明する。本実施の形態においては、第１に実施の形態と比較して、光情報記録媒体に予め記録する記録パラメータとして、変換係数Ａ₁、Ｂ₁、Ａ₂、Ｂ₂のすべてを用い、その代わりにＰindを記録パラメータから削除するものである。
【００５４】
この実施の形態においても、標準評価装置により最適化された記録パラメータＴmp、ｄＴtop、ｄＴera、γtarget、ρ、ε、Ａ₁、Ｂ₁、Ａ₂、Ｂ₂を光情報記録媒体に予め記録しておくことにより、実用的なドライブ装置にて充分な記録特性が得られる記録条件を容易に設定することができる。この場合はメディアに記録するパラメータは増えるがＰtargeta、ρaを求める時の演算処理が簡単になる。
【００５５】
【実施例】
以下、実施例について、本発明をさらに詳細に説明する。
＜実施例１＞
(光ディスクの作製)
ポリカーボネート製ＣＤ−ＲＷ用基板上に下部誘電体層、記録層、上部誘電体層、反射層を順次スパッタリング法を用いて成膜した。下部誘電体層材料及び上部誘電体層材料としてＺｎＳにＳｉＯ_２を２０ｍｏｌ％混合した誘電体を用い、記録層としてＡｇＩｎＳｂＴｅ合金に微量のＧｅを添加した材料を用いた。反射層材料にはＡｇを用いた。下部誘電体層の膜厚を７０ｎｍ、記録層膜厚を１５ｎｍ、上部誘電体層を２０ｎｍ、反射層を１５０ｎｍとした。さらに、その上に樹脂製の保護層をスピンコーティング法で成膜し、紫外線を照射することで硬化した。保護層材料は市販のＣＤ 用保護層材料である紫外線効果樹脂を用いた。保護層の膜厚は約１０μｍであった。
【００５６】
成膜後、記録層は急冷状態にあり、アモルファス状態である。そのため、ディスク全面を結晶化するために、ＣＤ−ＲＷ用初期化装置を用いて初期化した。初期化は高出力レーザを全面に照射及び走査することで行った。初期化レーザは波長８３０ｎｍであり、ビーム径は走査方向に１μｍ、その垂直方向に８０μｍであった。照射強度は８００ｍＷ（消費電力）で走査速度は２.５ｍ／ｓとした。完成したディスクは未記録状態でＣＤ−ＲＷディスクの各規格を満足するものであった。
【００５７】
（光ディスクの記録実験）
このようなディスクにＣＤの１６倍速相当の記録実験を行った。情報記録・再生装置としてパルステック工業製ＤＤＵ１０００を用い、記録ストラテジ発生装置としてソニーテクトロニクス製ＡＷＧ６１０を使用した。用いた記録ストラテジは図３で示した1Ｔストラテジであり、記録パルス巾Ｔｍｐを０.２５Ｔ、０.３０Ｔ、０.４０Ｔ、０.４５Ｔ（Ｔ＝１４.４ｎｓ）と変化させた時の、変調度と記録パワーの関係、及びジッターと記録パワーの関係を求めた。このとき、ｄＴtop＝０.１２５Ｔ、ｄＴera＝０である。また、消去パワーを設定するεは０.４とした。
【００５８】
変調度と記録パワーの関係より、図４に示すようなＰ targetと記録パルス巾Ｔｍｐの関係が得られた。また、ジッターと記録パワーの関係より、ジッター最小値での記録パワーを最適記録パワーＰｏとしたとき、図５に示すようなＰoと記録パルス巾Ｔｍｐの関係が得られた。図４、図５のグラフは共に直線に近似され、Ｐtarget−Ｔmp特性は、
Ｐtarget＝Ａ₁×Ｔmp/Ｔ+Ｂ₁
とするとき、Ａ₁＝−４４.７、Ｂ₁＝４９.４であった。また、Ｐo−Ｔmp特性は、
Ｐo＝Ａ₂×Ｔmp/Ｔ+Ｂ₂
とするとき、Ａ₂＝−７６.５、Ｂ₂＝６９.３であった。また、各Ｔmpに対してＴmp＝０.２５ＴのときがＰoにおけるジッター値は最小であった。
【００５９】
各記録パラメータとして、Ｔmp＝０.２５Ｔのときの以下の値がメディアにプリフォーマットされることで、１６倍速の１Ｔストラテジでの最適な記録が可能となる。
γtarget＝１.３５（図４より任意に設定）
Ｐind＝３８ｍＷ
ρ＝Ｐo／Ｐind＝５０／３８＝１.３２
ε＝０.４
ｄＴtop＝０.１２５Ｔ
ｄＴera＝０Ｔ
【００６０】
さらに、Ｔmp＝０.２５Ｔ（３.６ｎｓ）の記録パルス巾を発生させるのに充分に短い立上り、立下り時間を持たない発光源（レーザーダイオードとその駆動装置）を持つ実使用ドライブでの記録の為の変換パラメータとして、
Ａ₁＝−４４.７
Ａ₂＝−７６.５
をメディアにプリフォーマットすることで、Ｔmp＝０.２５Ｔ以上の記録パルス巾での記録でも良好な記録が可能となる。
【００６１】
すなわち、Ｔmp＝０.２５Ｔ以上のＴmp（＝Ｔmpa）でのＰtarget（＝Ｐtargeta）は、
Ｐtargeta＝Ａ₁×Ｔmpa/Ｔ+Ｂ₁
であり、Ｔmp＝０.２５Ｔのとき、Ｐtarget＝３８ｍＷであるので（この場合、Ｐind＝Ｐtargetとした）、
３８＝Ａ₁×０.２５+Ｂ₁
より、Ｂ₁＝３８−０．２５Ａ₁となるため、

であり、Ａ₁＝−４４.７を代入すると
Ｐtargeta＝−（Ｔmpa/Ｔ−０.２５）×４４.７＋３８
となり、実使用ドライブの記録パルス巾ＴmpaのときのＰtargetが求まるので、この値を実使用ドライブの記録パルス巾ＴmpaのときのＰindとすることができる。
【００６２】
また、Ｔmpaのときのρ（＝ρa）は、
ρa＝Ｐo／Ｐtargeta＝（Ａ₂×Ｔmpa/Ｔ+Ｂ₂）／Ｐtargetaであり、Ｔmp＝０ ２５Ｔのとき、ρ＝1.３２、Ｐtarget＝３８ｍＷであるので、
１.３２＝（Ａ₂×０．２５+Ｂ₂）／３８
より、Ｂ₂＝１.３２×３８−０.２５Ａ₂となるため、

であり、Ａ₂＝−７６.５を用いて

となり、実使用ドライブの記録パルス巾Ｔmpaを用いてρaを決定することができる。よって最終的には記録装置にマウントされた各メディアに対してγ法を用い、記録パルス巾がＴmpaの時の最適パワーＰｏ＝Ｐtargeta×ρaが設定される。
【００６３】
次に、ＴmpaのときのｄＴtopaは、Ｔmp＝０.２５ＴのときのｄＴtopをｄＴtopsとすると、

またＴtopa＝ｄＴtopa+Ｔmpa＝1.5Ｔmpa
であり、実使用ドライブの記録パルス巾Ｔmpaを用いて設定することができる。ｄＴera、εはＴmpによらず一定である。
よって、記録パルス巾Ｔmpaの時の記録ストラテジが設定される。
【００６４】
したがって、
γtarget＝１.３５
Ｐind＝３８ｍＷ
ρ＝１.３２
ε＝０.４
ｄＴtop＝０.１２５Ｔ
ｄＴera＝０
Ａ₁＝−４４.７
Ａ₂＝−７６.５
の各記録パラメータをメディアにプリフォーマットすることにより、１６倍速時の記録パルス巾０.２５Ｔの発生において充分に短い立上り、立下り時間を持たない発光源を持つ実使用ドライブ装置でも上記パラメータを用いて良好な記録が可能となる。
【００６５】
＜実施例２＞
実施例1において、メディアにプリフォーマットする記録パラメータとして、Ｐtarget＝Ａ₁×Ｔmp+Ｂ₁
及び
Ｐo＝Ａ₂×Ｔmp+Ｂ₂
におけるＢ₁、Ｂ₂を追加し、Ｐindは不用とした。したがって、メディアにプリフォーマットする記録パラメータとしては、
γtarget＝１.３５
ρ＝１.３２
ε＝０.４
ｄＴtop＝０.１２５Ｔ
ｄＴera＝０Ｔ
Ａ₁＝４４.７
Ａ₂＝−７６.５
Ｂ₁＝４９.４
Ｂ₂＝６９.３
となる。
【００６６】
この場合でも、実施例１での説明でも明らかなように、１６倍速時の記録パルス巾０.２５Ｔの発生において充分に短い立上り、立下り時間を持たない発光源を持つ実使用ドライブ装置でも上記パラメータを用いて良好な記録が可能となる。この場合はメディアに記録するパラメータは増えるがＰtargeta、ρaを求める時の演算処理が簡単になる。
【００６７】
【発明の効果】
上述したように、請求項1記載の発明によれば、情報記録媒体に対して標準記録再生装置により最適な記録特性を得ることを可能とする記録パラメータと、標準記録再生装置とは記録ストラテジが異なる記録再生装置で最適な記録特性を得ることを可能とする記録パラメータの変換係数を予め記録することにより、実用的記録再生装置では標準記録再生装置での記録ストラテジを設定できない場合でも、記録パラメータの変換係数を用いて情報記録媒体に良好な特性を持つ記録を行なうことができる。
【００６８】
請求項２記載の発明によれば、標準記録再生装置とは記録ストラテジが異なる記録再生装置はマルチパルスの記録パルス巾Ｔmpが異なる記録ストラテジを有する記録再生装置であるので、実用的記録再生装置において、標準記録再生装置での記録パルス巾Ｔmpに対して短い立上り・立下り時間を持たない場合でも、記録パラメータの変換係数を用いることにより、情報記録媒体に良好な特性を持つ記録を行なうこができる。
【００６９】
請求項３記載の発明によれば、記録パラメータとして、γ（ガンマ）法で使用されるＰind、γtarget、ρ、εを用いることにより、ＣＤ−ＲＷ規格及びＤＶＤ＋ＲＷ規格における記録パラメータを用いた変換パラメータを使用できるので、記録パルスの短い立上り・立下り時間を持たない実用的記録再生装置においても、情報記録媒体に良好な特性を持つ記録を確実に行なうことができる。
【００７０】
請求項４記載の発明によれば、記録パラメータの変換係数として、Ｐtarget＝Ａ₁×Ｔmp＋Ｂ₁及びＰo＝Ａ₂×Ｔmp＋Ｂ₂における変換係数Ａ₁またはＢ₁及びＡ₂またはＢ₂を用いることにより、標準記録再生装置で設定された記録パラメータに２つの変換係数を加えるだけで、記録パルスの短い立上り・立下り時間を持たない実用的記録再生装置においても、情報記録媒体に良好な特性を持つ記録を行なうことができる。
【００７１】
請求項５記載の発明によれば、記録パラメータとして、γ（ガンマ）法で使用されるγtarget、ρ、εを用い、記録パラメータの変換係数として、Ｐtarget＝Ａ₁×Ｔmp＋Ｂ₁及びＰo＝Ａ₂×Ｔmp＋Ｂ₂における変換係数Ａ₁、Ｂ₁、Ａ₂、Ｂ₂を用いることにより、記録パルスの短い立上り・立下り時間を持たない実用的記録再生装置においても、情報記録媒体に良好な特性を持つ記録を行なうことができると共に、Ｐtargeta、ρaを求める時の演算処理が簡単になる。
【図面の簡単な説明】
【図１】1Ｔストラテジ法におけるマーク形成時のパルス発光パターンを示す図である。
【図２】書換え可能な相変化型光情報記録媒体の構成の一例を示す断面図である。
【図３】記録パワーＰtargetと記録パルス巾Ｔmpの直線関係（ａ）と、最適記録パワーＰoと記録パルス巾Ｔmpの直線関係（ｂ）を示す図である。
【図４】実施例１のγをパラメータとした記録パワーＰtargetと記録パルス巾Ｔmpの関係を示す図である。
【図５】実施例１の最適記録パワーＰoと記録パルス巾Ｔmpの関係を示す図である。
【図６】点線で示した理想的な発光波形に対して、立上り・立下りに時間を要する実際の発光波形を実線で示す図である。
【符号の説明】
１：基板
２：下部保護層
３：記録層
４：上部保護層
５：反射層
６：樹脂層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for recording and reproducing information on a rewritable phase change type information recording medium by light.
[0002]
[Prior art]
In recent years, demand for high-speed recording of optical information recording media has been increasing. In particular, in the case of a disk-shaped optical information recording medium, that is, an optical disk, the recording / reproducing speed can be increased by increasing the rotation speed, and thus the speed is increasing. Among optical discs, optical information recording media that can record only by intensity modulation of the light irradiated at the time of recording have a simple recording mechanism, and can reduce the cost of the medium and the recording device, and at the same time, have high intensity reproduction. Since modulated light is used, high compatibility with read-only devices can be ensured, and the use of modulated light has spread. Due to the recent increase in the capacity of electronic information, demand for higher density and higher speed recording has been increasing. .
[0003]
Among such optical disks, those using a phase change material are becoming mainstream because of being capable of rewriting many times. In the case of an optical disk using a phase-change material for the recording layer, recording is performed by creating a rapidly cooled state and a gradually cooled state of the recording layer material by modulating the intensity of an irradiated light beam. The recording layer material becomes amorphous in the rapidly cooled state and becomes crystalline in the slowly cooled state. Since optical properties are different between amorphous and crystalline, optical information can be recorded.
[0004]
Since the recording principle uses a complex mechanism of "rapid cooling" and "slow cooling" of the recording layer material, high-speed recording involves irradiating the medium with recording light that has been pulse-divided and intensity-modulated to three values. (For example, see Patent Document 1).
[0005]
However, when the recording speed is increased, the basic clock frequency is increased, and is approximately 104 MHz for a CD-RW equivalent to a 24 × speed, and approximately 131 MHz for a DVD-RW and DVD + RW equivalent to a 5 × speed, so that the conventional recording method (recording strategy) In addition, the rising and falling effects in pulsed light emission are increased, and the effective irradiation light energy is reduced.
[0006]
FIG. 6 shows an example. As compared with the ideal light emission waveform indicated by the dotted line, the actual light emission waveform requires time to rise and fall, and thus does not become rectangular as indicated by the solid line in FIG. Further, when the basic clock frequency is increased, as shown in FIG. 6B, the ratio of the rise / fall time is increased, and a sufficiently high recording (peak) power and a sufficiently low bias (bottom) power can be secured. Gone. That is, the recording (peak) power Pw decreases by ΔPw, and the bias (bottom) power Pb increases by ΔPb.
[0007]
With such a recording waveform, sufficient heating and cooling are not performed on the recording layer material, so that it is difficult to secure a rapid cooling state. As a result, an amorphous recording mark (hereinafter, a recording mark is simply referred to as a mark). ) Is not sufficiently formed, and the amplitude of the reproduced signal decreases.
[0008]
In order to solve such a phenomenon, a light-emitting light source (laser diode and its driving device) having a short rise / fall time is required. However, it is very difficult to secure a light-emitting light source corresponding to a frequency exceeding 100 MHz. Have difficulty.
[0009]
Therefore, as a technique for performing high-speed recording with a current light-emitting light source, it has been proposed to cope with the problem by reducing the number of recording pulses (for example, see Patent Literature 2 and Patent Literature 3). This is a recording pulse for each basic clock cycle T as defined in the conventional CD-RW standard (Recordable Compact Disc System Part III: CD-RW Version 2.0, Volume 2: High-Speed Version 1.1). Is not a recording method (hereinafter referred to as a 1T strategy method), but a recording method (hereinafter referred to as a 2T strategy method) in which a recording pulse is generated every 2T, which is twice the basic clock period T. Specifically, this is a technique in which recording is performed with three pulses as shown in FIG. 6B, but is recorded with two pulses as shown in FIG. 6C. This makes it possible to increase the light emission time (Pw level time) and cooling time (Pb level time) per pulse, thereby reducing the influence of the rise and fall times described above.
[0010]
However, in the recording by the 2T strategy method, since the light is emitted by m pulses when the number is an odd multiple of the basic clock cycle, that is, n = (2m + 1), and the even multiple, that is, when n = 2m, each of the even number and the odd number is used. It is necessary to set an optimal light emission pattern, and it is difficult to optimize the light emission pattern.
[0011]
Patent Document 4 proposes a method of setting the length of each pulse independently and individually. If this method is used, even if the optical system has a low recording power and a low response, a high modulation degree can be obtained. And good jitter can be obtained. However, as described above, since a complicated adjustment is required for the marks of each length, the dependence of the recording mark length (hereinafter simply referred to as the mark length) on the recording power Pw is different for each mark of each length. Will be different. As a result, there is a disadvantage that the recording power margin becomes narrow.
[0012]
Even in the 1T strategy method, a laser diode having a sufficiently short rise / fall time and a drive device for generating a write pulse of the strategy optimized by the standard evaluation device with a practical drive device must be provided. However, it is costly and it is difficult to put the drive into practical use.
[0013]
[Patent Document 1]
JP-A-9-219021
[Patent Document 2]
JP-A-9-134525
[Patent Document 3]
U.S. Pat. No. 5,732,062
[Patent Document 4]
JP 2001-331936 A
[0014]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art. In the 1T strategy method, even in a high-speed writing in which a basic clock frequency exceeds 100 MHz, a light emitting light source having a conventional rise / fall time (a laser diode and a laser diode) is used. It is an object of the present invention to provide an information recording method capable of obtaining sufficient recording characteristics with a practical drive device using the drive device).
[0015]
[Means for Solving the Problems]
That is, according to the first aspect of the present invention, by irradiating the information recording medium with light, a phase change is caused in the recording layer of the information recording medium, and information can be recorded on and reproduced from the information recording medium and can be rewritten. In the information recording / reproducing method, a recording parameter which enables an optimum recording characteristic to be obtained by a standard recording / reproducing apparatus is recorded in advance on the information recording medium, and a recording strategy different from that of the standard recording / reproducing apparatus is used. It is characterized in that a conversion coefficient of the recording parameter is recorded so that an optimum recording characteristic can be obtained in a reproducing apparatus.
[0016]
According to a second aspect of the present invention, in the information recording / reproducing method of the first aspect, the recording / reproducing apparatus having a different recording strategy from the standard recording / reproducing apparatus is a recording / reproducing apparatus having a recording strategy having a different recording pulse width Tmp of a multi-pulse. It is characterized by the following.
[0017]
According to a third aspect of the present invention, in the information recording / reproducing method of the second aspect, the recording parameters correspond to γtarget and γtarget which are arbitrary γ values used in the (gamma) method used for determining the optimum recording power Po. It is characterized by including at least one of a recording power Pind, a ratio ρ of Po to Pind, and a ratio ε of an erasing power Pe to Po.
[0018]
According to a fourth aspect of the present invention, in the information recording / reproducing method of the third aspect, if the recording power when γ = γtarget is Ptarget, Ptarget = A₁× Tmp + B₁, Po = A_Two× Tmp + B_TwoWhere the conversion parameter of the recording parameter is at least A₁Or B₁One of A and A_TwoOr B_TwoOr any one of the following.
[0019]
According to a fifth aspect of the present invention, in the information recording / reproducing method of the second aspect, the recording parameters are arbitrary γ values used in a γ (gamma) method used to determine an optimum recording power Po. And the ratio ρ of the erasing power Pe to the optimum recording power Po, the recording power when γ = γtarget is Ptarget, and Ptarget = A₁× Tmp + B₁, Po = A_Two× Tmp + B_Two, The conversion coefficient of the recording parameter is A₁, B₁, A_Two, And B_TwoIt is characterized by including.
[0020]
The object of the information recording / reproducing method of the present invention is a rewritable phase-change optical information recording medium, such as a CD-RW, a DVD-RAM, a DVD-RW, a DVD + RW, and a PD. Recording and reproduction of information on and from the optical information recording medium are performed by scanning a light beam focused near the recording layer. Recording of information is performed by irradiating intensity-modulated light to form, for example, an amorphous mark in a crystal.
[0021]
The information recording / reproducing method of the present invention is a method of recording information by changing the length of a mark and the length of a space between marks (space) using the basic clock period Tw as a minimum unit. Modulation). Examples of PWM include EFM (Eight to Fourteen Modulation: 8-14 modulation) used for compact discs, EFM + (a type of 8-16 modulation) used for DVD (Digital Versatile Disc), and BRD (Blue). -Ray Disc).
[0022]
In these PWM modulation methods, since information is encoded in the length of a mark and a space, it is important that the mark length and the space length are uniform. The mark length and the space length are n times (n is a natural number) the basic clock period T, that is, n · T. T = 231.4 ns and n = 3 to 11 in the case of a 1 × speed EFM of a compact disc, and T = 38.1 ns and n = 3 to 11 and 14 in the case of a 1 × speed of a DVD.
[0023]
The formation of these marks having a length of n · T is performed by irradiating the recording layer with intensity-modulated light. There are three levels of irradiation intensity, which are represented by recording power Pw, erasing power Pe, and bias power Pb, respectively, and have a relationship of Pw> Pe> Pb. When recording a mark, pulse light emission of recording power (peak power) Pw and bias power (bottom power) Pb is performed, and when recording a space (or erasing a mark), CW light emission of erasing power Pe (CW: Continuous Wave: a continuous wave, that is, light emission at a constant intensity without intensity modulation. The recording layer material is heated and quenched by irradiating pulse light to form an amorphous mark, and CW light is emitted with lower power to heat and gradually cool the recording layer to form a crystalline space.
[0024]
FIG. 1 shows a pulse light emission pattern at the time of mark formation in the 1T strategy method specified in the CD-RW standard (Recordable Compact Disc System Part III: CD-RW Volume 2: High-Speed Version 1.1). In FIG. 1, Ttop is the pulse width at the head of the mark, Tmp is the recording pulse width of the multipulse following the head pulse, and dTtop is the time from the position 1T after the rising of the EFM data signal to the rising of the head pulse, dTera. Indicates the time from the falling position of the EFM data signal to the rising of the erasing power Pe. The recording pulse width Tmp is fixed, but dTtop and dTera are set according to the medium.
[0025]
The information recording / reproducing method of the present invention uses a laser diode and a drive that can be mounted on a practical drive at a low cost, instead of the recording pulse width Tmps, which is one of the recording parameters optimized by the 1T strategy method by a standard evaluation device. A good recording characteristic can be obtained by using a recording pulse width Tmpa (Tmps <Tmpa) which can be realized by the apparatus. A new recording condition when the recording pulse width Tmpa is used is set by the following process.
[0026]
First, an optimal strategy is searched for by a standard evaluation device, and Tmp, dTtop, and dTera are set. It is also disclosed in Japanese Patent No. 3081551 and is an OPC (Optimum Power Control) parameter in the γ (gamma) method for setting the optimum recording power and erasing power specified in the CD-RW standard. Set Pind, γtarget, ρ, and ε. In the γ method, the modulation degree m corresponding to the recording power Pw and the minute change amount ΔPw and the minute change amount Δm
γ = (Δm / m) / (ΔPw / Pw)
Is defined, and γ target is first set as an arbitrary γ value. Pind is a recording power value close to (or equal to) the recording power Ptarget when γ = γtarget in the characteristic curve of γ vs Pw, and is a value serving as a starting point when the recording apparatus performs the OPC operation. ρ is the ratio of Po to Pind, and ε is the ratio of the erasing power Pe to Po.
In a specific OPC operation, the recording apparatus changes the recording power around Pind for the medium mounted on the recording apparatus, obtains a characteristic curve of γ vs Pw, and obtains the recording power Ptarget when γ = γ target. . The optimum power Po is set by Po = Ptarget × ρ, and the erasing power Pe is set by Pe = Po × ε.
[0027]
Next, using Ttop, dTera, and ε, the relationship between the modulation degree m and the recording power Pw is determined using Tmp as a parameter. From this relationship between m and Pw, γ was used as a parameter.
Find the characteristic of Ptarget-Tmp. Ptarget is linear with respect to the recording pulse width Tmp,
Ptarget = A₁× Tmp + B₁
There is a relationship. Further, the optimum recording power Po which is Pw at the minimum value of the jitter in the relationship between the jitter of the reproduction signal and Pw is also linear with respect to Tmp,
Po = A_Two× Tmp + B_Two
In a relationship.
[0028]
Therefore, Ptarget, which is Ptarget with respect to the recording pulse width Tmpa, is:
Ptargeta = A₁× Tmpa + B₁
Is set by Here, assuming that Ptarget at the time of the recording pulse width Tmps is Ptargets,
Ptargets = A₁× Tmps + B₁
Therefore, B₁Let A be a constant₁Are Ptargets, Tmps and B₁And can be represented by A₁Let B be a constant₁Are Ptargets, Tmps and A₁Can be represented by
A₁
Further, ρa, which is ρ with respect to the recording pulse width Tmpa, is given by the relationship ρa = Po / Ptargeta.
ρa = (A_Two× Tmpa + B_Two) / (A₁× Tmpa + B₁)
Is set by Here, assuming that ρ at the time of the recording pulse width Tmps is ρs,
ρs = (A_Two× Tmps + B_Two) / (A₁× Tmps + B₁)
Therefore, B_TwoLet A be a constant_TwoIs ρs, Tmps, Ptargets, A₁(Or B₁) And B_TwoAnd can be represented by A_TwoLet B be a constant_TwoIs ρs, Tmps, Ptargets, A₁(Or B₁) And A_TwoCan be represented by
[0030]
Ε (= Pe / Po) for setting the erasing power Pe from the optimum recording power Po is set to be constant regardless of Tmp.
[0031]
Next, the top pulse width Ttop of the mark record is
Ttop = dTtop + Tmp
Therefore, Ttop and dTtop optimized at the time of the recording pulse width Tmps in the standard evaluation device are Ttops and dTtops, and Ttop and dTtop in the laser diode and the driving device that can be mounted on a practical drive are Ttopa and Assuming that dTtopa, Tmp is proportional to the change from Tmps to Tmpa in the standard evaluation device,

Is set by Therefore, dTtopa is
dTtopa = dTtops × (Tmpa / Tmps)
It is.
[0032]
Next, dTera is for setting the rising position of the space after the recorded mark. In order to make the rising position the same regardless of Tmp, dTera is set to be constant.
[0033]
As described above, the recording parameters necessary for recording with the recording pulse width Tmpa achievable with the laser diode that can be mounted on the practical drive and the driving device are Tmp, dTtop, dTera, Pind, and γtarget set by the standard evaluation device. , Ρ, ε, and the conversion coefficient A₁(Or B₁), A_Two(Or B_Two).
[0034]
Here, Pind cannot directly use Ptarget (= Ptargets) for the recording pulse width Tmps. Because these parameters are recorded in ATIP (Absolute Time In Pre-groove) ATIP Extra Information Additional Information specified in the CD-RW standard, they are used in practical recording devices (CD-R / RW drives). This is because when recording on a medium, a prepared discrete value must be used. As a result, since Pind generates a slight error from Ptargets, Ptargeta and ρa also cause some errors.
[0035]
In the above description, in order to reduce the number of recording parameters, the necessary conversion coefficient is A₁, B₁A and any one of_Two, B_Two, And P targeta and ρa are determined by A₁, B₁, A_Two, B_TwoIt is also possible to set the recording parameters without using Pind using the four parameters. In this case, the number of parameters to be recorded on the medium increases, but the calculation processing for obtaining Ptargeta and ρa is simplified.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A first embodiment using the information recording / reproducing method of the present invention will be described. The target information recording medium is, for example, a rewritable phase-change optical information recording medium such as a CD-RW, a DVD-RAM, a DVD-RW, a DVD + RW, and a PD. Has at least a recording layer and a reflective layer.
[0037]
FIG. 2 shows an example of the configuration of a rewritable phase-change optical information recording medium, in which a lower protective layer 2, a recording layer 3, an upper protective layer 4, a reflective layer 5, a resin layer 6 are formed on a transparent substrate 1. Are sequentially laminated.
The material of the transparent substrate 1 is desirably substantially transparent in the recording / reproducing wavelength region, and at the same time, can secure the mechanical strength of the disk. Examples of the material include glass and resin, but from the viewpoint of cost, strength, and transparency. It is common and preferred to use a polycarbonate resin. A guide groove (groove) for facilitating scanning of the light beam may be formed on the substrate 1.
[0038]
As the material of the recording layer 3, a phase change material is used. The phase change material needs to be a material having two or more phases that change reversibly, and for example, a material that changes phase between crystal and amorphous. Information is recorded by forming an amorphous mark in a crystalline state or by forming a crystalline mark in an amorphous state.
[0039]
As the reflection layer 5, any metal or alloy can be used. Examples of the reflective layer material include Au, Ag, Cu, Al, and alloys thereof.
[0040]
Generally, protective layers are provided above and below the recording layer 3. The protective layer protects the resin substrate 1 from the heat applied to the recording layer 3 and the lower protective layer 2 to prevent heat diffusion of atoms of the recording layer 3 to the reflective layer 5 and efficiently provide thermal energy to the recording layer. There is an upper protective layer 4 formed so as to be hooked. The lower protective layer 2 may be formed between the substrate 1 and the recording layer 3 and may be a multilayer film in which a plurality of layers are stacked in view of thermal characteristics or optical characteristics. The upper protective layer 4 is formed between the recording layer 3 and the reflective layer 5 and, like the lower protective layer 2, may have a multilayer structure in terms of thermal / optical characteristics or chemical characteristics. The protective layer material includes any dielectric, semiconductor, metalloid or mixture of these materials. On the reflective layer 5, a resin layer (overcoat layer) 6 for protecting the above layers from mechanical and chemical damage may be provided, or a resin substrate or the like may be bonded.
[0041]
Recording and reproduction of information on the optical information recording medium are performed by scanning a light beam focused near the recording layer 3. The information recording / reproducing method of the present invention is applied to a PWM system in which information is recorded by changing the length of a mark and the length of a space between marks using a basic clock cycle T as a minimum unit. In the PWM method, a mark and a space having a length that is an integral multiple (n · T) of the basic clock period T are formed by irradiating intensity-modulated light. There are three levels of irradiation intensity, which are represented by recording power Pw, erasing power Pe, and bias power Pb, respectively, and have a relationship of Pw> Pe> Pb. When recording a mark, pulse light emission of recording power (peak power) Pw and bias power (bottom power) Pb is performed, and when recording a space (or erasing a mark), CW light emission of erasing power Pe is performed. That is, the recording layer material is heated and quenched by irradiating pulse light of the recording power Pw and the bias power Pb, thereby forming an amorphous mark, and emitting CW light of the erasing power Pe to heat and gradually heat the recording layer material. By cooling, a space in a crystalline state is formed.
[0042]
For such mark formation, a pulse emission pattern of the 1T strategy method specified in the CD-RW standard as shown in FIG. 1 is used. In this pulse emission pattern, the recording pulse width Tmp of the multi-pulse is fixed, but dTtop, which is the time from the position 1T after the rise of the EFM data signal to the rise of the first pal, from the falling position of the EFM data signal. The time dTera until the erasing power Pe rises is set according to the recording medium.
[0043]
First, an optimal strategy is searched for by a standard evaluation device, and Tmp, dTtop, and dTera are set. Also, γ target in the γ method and ε for determining the erase power Pe are set. Next, by obtaining the relationship between the modulation degree m and the recording power Pw,
γ = (Δm / m) / (ΔPw / Pw)
Is set from the recording power Pw (= Ptarget) when γ = γtarget. By determining the relationship between the jitter of the reproduced signal and Pw, ρ (= Po / Pind) is set with the recording power Pw at the minimum value of the jitter as the optimum recording power Po.
[0044]
Further, a linear relationship between the recording power Ptarget and the recording pulse width Tmp when γ = γtarget is obtained as shown in FIG.
Ptarget = A₁× Tmp + B₁
Conversion factor A in₁And B₁Is set.
[0045]
Further, a linear relationship between the optimum recording power Po and the recording pulse width Tmp at the minimum value of the jitter as shown in FIG.
Po = A_Two× Tmp + B_Two
Conversion factor A in_TwoAnd B_TwoIs set.
[0046]
Tmp, dTtop, dTera, Pind, γtarget, ρ, ε, and conversion coefficient A set by the standard evaluation device as described above.₁(Or B₁), A_Two(Or B_Two) Is recorded in the optical information recording medium in advance.
[0047]
When information is recorded on an optical information recording medium in which the above set values are recorded in advance by a recording / reproducing apparatus having a recording pulse width Tmp different from the recording pulse width Tmp optimized by the standard evaluation apparatus, Recording conditions are set in the process. Here, in order to identify both recording conditions, the recording pulse width Tmp optimized by the standard evaluation device is Tmps, and dTtop, dTera, Ptarget, ρ, and ε corresponding to the Tmps are respectively dTtops, dTeras, While Ptargets, ρs, and εs, the recording pulse width Tmp in the recording / reproducing apparatus is represented by Tmpa (Tmps <Tmpa), and dTtop, dTera, Ptarget, ρ, and ε corresponding to the Tmps are respectively dTtopa, dTeraa, Ptargeta, Description will be given as ρa and εa.
[0048]
dTera and ε are constant irrespective of the recording pulse width Tmp, and dTeraa = dTeras, εa = εs, but dTtopa, Ptargeta, and ρa are recording parameters dTtops, Pind, ρs, A₁(Or B₁), A_Two(Or B_Two).
[0049]
dTtopa is given by

Than,
dTtopa = dTtops × Tmpa / Tmps
Holds, and is calculated from the recording pulse width Tmpa and the set values Tmps and dTtops.
[0050]
Ptargeta at the recording pulse width Tmpa when γ = γtarget is given by the following equation.
Ptargeta = A₁× Tmpa + B₁
A to satisfy the relationship₁Is set, B₁To
Ptargets = A₁× Tmps + B₁
from
B₁= Ptargets-A₁× Tmps
Is easily calculated from the known data. Here, the set value Pind is applied as Ptargets. Also, B₁Is set, A₁To
A₁= (Ptargets-B₁) / Tmps
Is used. Ptargeta calculated in this way is set as Pind at the recording pulse width Tmpa.
[0051]
ρa is
ρa = Po / Ptargeta
In this case, the optimum recording power Po is given by the following equation.
Po = A_Two× Tmpa + B_Two
Is represented by
ρa = (A_Two× Tmpa + B_Two) / (A₁× Tmpa + B₁)
Becomes Where A_TwoIs set, B_TwoIs
ρs = (A_Two× Tmps + B_Two) / (A₁× Tmps + B₁)
Than,
B_Two= Ρs × (A₁× Tmps + B₁)-(A_Two× Tmps)
Ρa is ρs, Tmps, A_Two, A₁, B₁Calculated more easily. A₁, B₁Is a value calculated from the set value as described above. Also, B_TwoIs set, A_TwoIs
A_Two= ｛Ρs × (A₁× Tmps + B₁) -B_Two｝ / Tmps
More required.
[0052]
As is clear from the above description, in the present embodiment, the recording parameters Tmp, dTtop, dTera, Pind, γtarget, ρ, ε, and the conversion coefficient A optimized by the standard evaluation device₁(Or B₁), A_Two(Or B_Two) Is recorded on an optical information recording medium in advance, so that recording conditions under which optimum recording characteristics can be obtained in recording / reproducing apparatuses having different recording pulse widths can be easily set, and the basic clock frequency exceeds 100 MHz. Even with high-speed writing, sufficient recording characteristics can be obtained with a conventional recording / reproducing apparatus using a light-emitting light source (laser diode and its driving device) having rise / fall times.
[0053]
Next, a second embodiment using the information recording / reproducing method of the present invention will be described. In this embodiment, first, as compared with the first embodiment, the conversion coefficient A is used as a recording parameter to be prerecorded on the optical information recording medium.₁, B₁, A_Two, B_TwoIs used, and instead, Pind is deleted from the recording parameters.
[0054]
Also in this embodiment, the recording parameters Tmp, dTtop, dTera, γtarget, ρ, ε, A₁, B₁, A_Two, B_TwoIs recorded in advance on an optical information recording medium, recording conditions under which sufficient recording characteristics can be obtained with a practical drive device can be easily set. In this case, the number of parameters to be recorded on the medium increases, but the calculation processing for obtaining Ptargeta and ρa is simplified.
[0055]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
<Example 1>
(Production of optical disk)
A lower dielectric layer, a recording layer, an upper dielectric layer, and a reflective layer were sequentially formed on a polycarbonate CD-RW substrate by a sputtering method. ZnS to SiO as lower dielectric layer material and upper dielectric layer material₂Was used as a recording layer, and a material obtained by adding a small amount of Ge to an AgInSbTe alloy was used as a recording layer. Ag was used for the material of the reflection layer. The thickness of the lower dielectric layer was 70 nm, the thickness of the recording layer was 15 nm, the thickness of the upper dielectric layer was 20 nm, and the thickness of the reflective layer was 150 nm. Further, a protective layer made of a resin was formed thereon by spin coating, and cured by irradiating ultraviolet rays. As the protective layer material, an ultraviolet ray effect resin which is a commercially available protective layer material for CD was used. The thickness of the protective layer was about 10 μm.
[0056]
After film formation, the recording layer is in a quenched state and is in an amorphous state. Therefore, in order to crystallize the entire surface of the disk, the disk was initialized using a CD-RW initialization device. Initialization was performed by irradiating and scanning the entire surface with a high-power laser. The initialization laser had a wavelength of 830 nm, and the beam diameter was 1 μm in the scanning direction and 80 μm in the vertical direction. The irradiation intensity was 800 mW (power consumption) and the scanning speed was 2.5 m / s. The completed disc satisfies each standard of the CD-RW disc in an unrecorded state.
[0057]
(Recording experiment on optical disc)
A recording experiment was performed on such a disc at a speed equivalent to 16 times the speed of a CD. DDU1000 manufactured by Pulstec Industrial was used as an information recording / reproducing device, and AWG610 manufactured by Sony Tektronix was used as a recording strategy generator. The recording strategy used is the 1T strategy shown in FIG. 3, and the modulation when the recording pulse width Tmp is changed to 0.25T, 0.30T, 0.40T, 0.45T (T = 14.4 ns). The relationship between degree and recording power and the relationship between jitter and recording power were determined. At this time, dTtop = 0.125T and dTera = 0. Further, ε for setting the erasing power was set to 0.4.
[0058]
From the relationship between the modulation degree and the recording power, as shown in FIG.P targetAnd the recording pulse width Tmp. Further, from the relationship between jitter and recording power, when the recording power at the minimum value of jitter was the optimum recording power Po, the relationship between Po and the recording pulse width Tmp as shown in FIG. 5 was obtained. 4 and 5 are both approximated to straight lines, and the Ptarget-Tmp characteristic is
Ptarget = A₁× Tmp / T + B₁
And A₁= -44.7, B₁= 49.4. The Po-Tmp characteristic is
Po = A_Two× Tmp / T + B_Two
And A_Two= -76.5, B_Two= 69.3. When Tmp = 0.25T for each Tmp, the jitter value at Po was the minimum.
[0059]
As the recording parameters, the following values at the time of Tmp = 0.25T are preformatted on the medium, so that optimal recording can be performed with a 16 × speed 1T strategy.
γ target = 1.35 (arbitrarily set from Fig. 4)
Pind = 38mW
ρ = Po / Pind = 50/38 = 1.32.
ε = 0.4
dTtop = 0.125T
dTera = 0T
[0060]
Furthermore, recording with an actual drive having a light-emitting source (laser diode and its driving device) having no rise and fall times short enough to generate a recording pulse width of Tmp = 0.25T (3.6 ns) As conversion parameters for
A₁= -44.7
A_Two= -76.5
Is pre-formatted on a medium, good recording is possible even with recording with a recording pulse width of Tmp = 0.25T or more.
[0061]
That is, Ptarget (= Ptargeta) at Tmp (= Tmpa) of Tmp = 0.25T or more is
Ptargeta = A₁× Tmpa / T + B₁
When Tmp = 0.25T, Ptarget = 38 mW (in this case, Pind = Ptarget),
38 = A₁× 0.25 + B₁
Than B₁= 38-0.25A₁Because

And A₁= -44.7
Ptargeta = − (Tmpa / T−0.25) × 44.7 + 38
Since Ptarget at the time of the recording pulse width Tmpa of the actually used drive is obtained, this value can be set as Pind at the time of the recording pulse width Tmpa of the actually used drive.
[0062]
Ρ (= ρa) at the time of Tmpa is
ρa = Po / Ptargeta = (A_Two× Tmpa / T + B_Two) / Ptargeta, and when Tmp = 025T, ρ = 1.32 and Ptarget = 38 mW,
1.32 = (A_Two× 0.25 + B_Two) / 38
Than B_Two= 1.32 x 38-0.25A_TwoBecause

And A_Two== 76.5

Ρa can be determined by using the recording pulse width Tmpa of the actual drive. Therefore, finally, the optimum power Po = Ptargeta × ρa when the recording pulse width is Tmpa is set by using the γ method for each medium mounted on the recording apparatus.
[0063]
Next, assuming that dTtopa at the time of Tmpa is dTtops at the time of Tmp = 0.25T,

Also, Ttopa = dTtopa + Tmpa = 1.5Tmpa
This can be set using the recording pulse width Tmpa of the drive actually used. dTera and ε are constant regardless of Tmp.
Therefore, the recording strategy for the recording pulse width Tmpa is set.
[0064]
Therefore,
γ target = 1.35
Pind = 38mW
ρ = 1.32
ε = 0.4
dTtop = 0.125T
dTera = 0
A₁= -44.7
A_Two= -76.5
By preformatting each recording parameter of the medium into a medium, the above parameters are used even in an actual drive device having a light emitting source having no sufficiently short rise and fall times when a recording pulse width of 0.25T at 16 × speed is generated. And good recording becomes possible.
[0065]
<Example 2>
In the first embodiment, Ptarget = A₁× Tmp + B₁
as well as
Po = A_Two× Tmp + B_Two
B in₁, B_TwoWas added and Pind was unnecessary. Therefore, the recording parameters to be preformatted on the media are:
γ target = 1.35
ρ = 1.32
ε = 0.4
dTtop = 0.125T
dTera = 0T
A₁= 44.7
A_Two= -76.5
B₁= 49.4
B_Two= 69.3
Becomes
[0066]
In this case as well, as is apparent from the description of the first embodiment, even in an actual drive device having a light emitting source that does not have a sufficiently short rise and fall time when a recording pulse width of 0.25T is generated at 16 × speed, Good recording becomes possible using parameters. In this case, the number of parameters to be recorded on the medium increases, but the calculation processing for obtaining Ptargeta and ρa is simplified.
[0067]
【The invention's effect】
As described above, according to the first aspect of the present invention, the recording parameters that enable the standard recording / reproducing device to obtain optimum recording characteristics for the information recording medium, and the recording strategy of the standard recording / reproducing device By pre-recording the conversion parameters of the recording parameters that enable the optimum recording characteristics to be obtained by different recording and reproducing devices, even if the recording strategy in the standard recording and reproducing device cannot be set in a practical recording and reproducing device, the recording parameters can be set. Recording with good characteristics can be performed on the information recording medium using the conversion coefficient of
[0068]
According to the second aspect of the present invention, a recording / reproducing apparatus having a different recording strategy from the standard recording / reproducing apparatus is a recording / reproducing apparatus having a recording pulse width Tmp different from that of the multi-pulse. Even when the rise / fall time is not short with respect to the recording pulse width Tmp in the standard recording / reproducing apparatus, it is possible to perform recording with good characteristics on the information recording medium by using the conversion coefficient of the recording parameter. it can.
[0069]
According to the third aspect of the present invention, by using Pind, γtarget, ρ, and ε used in the γ (gamma) method as the recording parameters, the conversion parameters using the recording parameters in the CD-RW standard and the DVD + RW standard are used. Therefore, even with a practical recording / reproducing apparatus having no short rise / fall time of the recording pulse, it is possible to reliably perform recording with good characteristics on the information recording medium.
[0070]
According to the fourth aspect of the present invention, Ptarget = A₁× Tmp + B₁And Po = A_Two× Tmp + B_TwoConversion factor A in₁Or B₁And A_TwoOr B_TwoBy using only the two conversion coefficients to the recording parameters set by the standard recording / reproducing apparatus, the recording / reproducing apparatus which does not have a short rise / fall time of the recording pulse is suitable for the information recording medium. Recording with various characteristics can be performed.
[0071]
According to the fifth aspect of the present invention, γtarget, ρ, and ε used in the γ (gamma) method are used as the recording parameters, and Ptarget = A as the recording parameter conversion coefficient.₁× Tmp + B₁And Po = A_Two× Tmp + B_TwoConversion factor A in₁, B₁, A_Two, B_TwoBy using the method, even with a practical recording / reproducing apparatus having no short rise / fall time of the recording pulse, it is possible to perform recording with good characteristics on the information recording medium and to calculate Ptargeta and ρa. Processing is simplified.
[Brief description of the drawings]
FIG. 1 is a diagram showing a pulse emission pattern at the time of forming a mark in the 1T strategy method.
FIG. 2 is a cross-sectional view showing an example of the configuration of a rewritable phase-change optical information recording medium.
FIG. 3 is a diagram showing a linear relationship (a) between a recording power Ptarget and a recording pulse width Tmp, and a linear relationship (b) between an optimum recording power Po and a recording pulse width Tmp.
FIG. 4 is a diagram illustrating a relationship between a recording power Ptarget and a recording pulse width Tmp using γ as a parameter in the first embodiment.
FIG. 5 is a diagram illustrating a relationship between an optimum recording power Po and a recording pulse width Tmp according to the first embodiment.
FIG. 6 is a diagram illustrating, with a solid line, an actual light emission waveform that requires time to rise and fall with respect to an ideal light emission waveform indicated by a dotted line.
[Explanation of symbols]
1: substrate
2: Lower protective layer
3: Recording layer
4: Upper protective layer
5: reflective layer
6: Resin layer

Claims (5)

By irradiating the information recording medium with light to cause a phase change in the recording layer of the information recording medium, recording and reproducing information on and from the information recording medium, and a rewritable information recording and reproducing method, The recording parameters enabling the standard recording / reproducing device to obtain the optimum recording characteristics are recorded in advance on the information recording medium, and the optimum recording characteristics are obtained by a recording / reproducing device having a recording strategy different from that of the standard recording / reproducing device. An information recording / reproducing method, wherein a recording coefficient of the recording parameter is recorded. 2. The information recording / reproducing method according to claim 1, wherein the recording / reproducing apparatus having a recording strategy different from that of the standard recording / reproducing apparatus is a recording / reproducing apparatus having a recording strategy in which a recording pulse width Tmp of a multi-pulse is different. The recording parameters include an arbitrary γ value used in the (gamma) method used to determine the optimum recording power Po, a recording power Pin corresponding to the γ target, a ratio ρ of Po to Pin, and an erasing power Pe to Po. 3. The information recording / reproducing method according to claim 2, wherein at least one of the ratios ε is included. Assuming that the recording power when γ = γtarget is Ptarget, when Ptarget = A ₁ × Tmp + B ₁ and Po = A ₂ × Tmp + B ₂ , the conversion coefficient of the recording parameter is at least _{one of} A _{1 and} B _1. , and the information recording and reproducing method according to claim 3, characterized in that it comprises one of a ₂ or B _2. The recording parameters include an arbitrary γ value used in the γ (gamma) method used to determine the optimum recording power Po, a recording power Pin corresponding to the γ target, a ratio ρ of Po to Pin, ρ, and an optimum recording. Including the ratio ε of the erasing power Pe to the power Po, and assuming that the recording power when γ = γtarget is Ptarget, when Ptarget = A ₁ × Tmp + B ₁ and Po = A ₂ × Tmp + B ₂ , the conversion coefficient of the recording parameter 3. The information recording / reproducing method according to claim ₂ , wherein A includes B ₁ , B ₁ , A ₂ , and B ₂ .

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