JP4223703B2 - Phase change information recording medium - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、コンピューターメモリ、画像および音声ファイル用メモリー、光カードなどに利用される光記録媒体に関し、また、レーザなどの光により情報の記録あるいは再生などを行なう情報記録媒体に関し、特に高記録密度化あるいは感度に優れた相変化型情報記録媒体に関する。
【０００２】
【従来の技術】
レーザービームの照射による記録、再生が可能な光媒体として、結晶−非晶質の転移を利用する相変化媒体や、色素−穴明きによる反射率差を利用する色素媒体がある。従来記録、再生可能な光媒体に関して光入射する側から再生専用のメディアに関しては２層の記録層（ピット）形成が容易であった。しかしながら記録再生ができる層を２層設ける場合、１層は光を透過しかつ吸収させて記録をするという相反する現象を起こさせなくてはならない。透過するということは通常の膜厚では吸収が少なく、厚い放熱層を設けると、光が透過しないので、放熱が十分ではないので、アモルファス化しにくい。このことから高速で記録しにくい、高密度で記録できない現象が生じていた。また記録層間が１０μｍから３０μｍ程度と狭いので初期化時や記録時に層間の熱的な干渉が起き記録層２層製膜後に初期化しても十分な記録再生特性が得られず、各記録層毎に初期化することなどが行われている。しかし記録層の一方に記録している場合、もう一方の記録層のデータが消滅するという不具合があった。
【０００３】
ＣＤ−ＲやＣＤ−ＲＷなどの光ディスクは、ポリカーボネートなどプラスチックの円形基板、またはその上に設けた記録層に、円周方向に沿って、音や文字や画像の信号を記録し、その面にアルミニウムや金、銀などの金属を蒸着またはスパッタリングして反射層を形成したもので、基板面側からレーザー光を入射して、信号の記録、再生を行なう。近年、コンピューター等で扱う情報量が増加したことから、ＤＶＤ−ＲＡＭ、ＤＶＤ−ＲＷのような光ディスクの信号記録容量の増大および信号情報の高密度化が進んでいる。ＣＤの記録容量は６５０ＭＢ程度で、ＤＶＤは４．７ＧＢ程度であるが、今後、更なる高記録密度化が要求されている。このような高記録密度媒体を実現するために使用するレーザー波長を青色光領域まで短波長化することが提案されている。しかしながら従来の技術としては、特開平０８−２８７４７４号公報のように多層化することは述べられていても、具体的なメディアに関する情報がなかったり、特開平９−１９８７０９号公報では、実施例が相変化記録層２層で、光が最初に透過する層がＳｂＳｅ、もう一層がＧｅ２Ｓｂ２Ｔｅ５組成からなる記録層であった。実際には高速記録の観点では記録感度が悪くなり、Ｇｅ２Ｓｂ２Ｔｅ５の組成では高密度記録がしづらいことがわかっている。
【０００４】
【本発明が解決しようとする課題】
従って、本発明は、高速、高記録密度化に優れた相変化型情報記録媒体を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明の第（１）は、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂ元素とＴｅ元素を少なくとも含み、２つの記録層の間に熱伝導率の傾斜した層を有し、該保護層は、光入射側の熱伝導率が小さくすることで高密度記録を可能とすることと、初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくして記録層２層とも初期化を可能にし、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体を提供することである。
【０００７】
また、本発明の第（２）は、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂ元素とＴｅ元素を少なくとも含み、２つの記録層の間に熱伝導率の違う層を３層以上設け光入射側の層の熱伝導率を小さくすることで、初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくして記録層２層とも初期化を可能にし、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体を提供することである。
【０００９】
また、本発明の第（３）は、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂ元素とＴｅ元素を少なくとも含み、該記録層２層間に形成した透過率が違う層３層以上のうち、光入射側の層の透過率を高くすることで、初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくして記録層２層とも初期化を可能にし、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体を提供することである。
【００１２】
この発明の実施の形態にかかる基板および光ディスクの構成を図１に示す。
基板の材料は通常ガラス、セラミックスあるいは樹脂であり、樹脂基板が成形性、コストの点で好適である。樹脂の例としてはポリカーボネート樹脂、アクリル樹脂、エポキシ樹脂、ポリスチレン樹脂、アクリロニトリル−スチレン共重合体樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、シリコーン系樹脂、フッ素系樹脂、ＡＢＳ樹脂、ウレタン樹脂などが挙げられるが、成形性、光学特性、コストの点で優れるポリカーボネート樹脂、アクリル系樹脂が好ましい。基板面の一方に凹凸パターンが形成されており、こちら側に耐熱層、記録層などが成膜される。基板の厚さは特に制限されるものではない。基板側からレーザー光を照射しない場合は、光学特性を考慮する必要がなく、剛性の優れたポリエチレンテレフタレートなどが好ましい。
【００１３】
保護層（１）、保護層（２）、保護層（３）および保護層（４）は記録層の劣化変質を防ぎ、記録層の接着強度を高め、かつ記録特性を高めるなどの作用を有するもので、ＳｉＯ、ＳｉＯ２、ＺｎＯ、ＳｎＯ２、Ａｌ２Ｏ３、ＴｉＯ２、Ｉｎ２Ｏ３、ＭｇＯ、ＺｒＯ２などの金属酸化物、Ｓｉ３Ｎ４、ＡｌＮ、ＴｉＮ、ＢＮ、ＺｒＮなどの窒化物、ＺｎＳ、Ｉｎ２Ｓ３、ＴａＳ４などの硫化物、ＴａＣ、Ｂ４Ｃ、ＷＣ、ＴｉＣ、ＺｒＣなどの炭化物やダイヤモンド状カーボンあるいは、それらの混合物が挙げられる。これらの材料は、単体で耐熱層とすることもできるが、互いの混合物としてもよい。また、必要に応じて不純物を含んでもよい。耐熱層の融点は記録層よりも高いことが必要である。このような耐熱層は、各種気相成長法、たとえば真空蒸着法、スパッタリング法、プラズマＣＶＤ法、光ＣＶＤ法、イオンプレーティング法、電子ビーム蒸着法などによって形成できる。なかでも、スパッタリング法が、量産性、膜質等に優れている。
【００１４】
反射放熱層としては、一般的にはＡｌ、Ａｕ、Ａｇ、Ｃｕ、Ｔａなどの金属材料、またはそれらの合金などを用いることができる。また、添加元素としては、Ｃｒ、Ｔｉ、Ｓｉ、Ｃｕ、Ａｇ、Ｐｄ、Ｔａなどが使用される。このような反射放熱層は、各種気相成長法、たとえば真空蒸着法、スパッタリング法、プラズマＣＶＤ法、光ＣＶＤ法、イオンプレーティング法、電子ビーム蒸着法などによって形成できる。なかでも、スパッタリング法が、量産性、膜質等に優れている。
【００１５】
薄型基板は、高ＮＡの対物レンズを用いる場合、０．３ｍｍ以下の厚さが要求されるため、シート状であることが好ましい。材料としては、ポリカーボネート樹脂、アクリル樹脂、エポキシ樹脂、ポリスチレン樹脂、アクリロニトリル−スチレン共重合体樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、シリコーン系樹脂、フッ素系樹脂、ＡＢＳ樹脂、ウレタン樹脂などが挙げられるが、光学特性、コストの点で優れるポリカーボネート樹脂、アクリル系樹脂が好ましい。上記透明シートを用いて光透過層を形成する方法としては、紫外線硬化性樹脂、あるいは透明な両面粘着シートを介して、透明シートを貼りつける方法が挙げられる。また、紫外線硬化性樹脂を保護層上に塗布してこれを硬化させて光透過層を形成してもよい。
【００１６】
以上のような層構成で、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂ元素およびＴｅ元素を少なくとも含み、２つの記録層の間に熱伝導率の傾斜した層を設けて高密度記録を可能とすることと初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくして記録層２層とも初期化を可能にし、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体を提供することができ、熱伝導率の傾斜した層のつくる方法は窒化物、酸化物それぞれ、窒素量、酸素量を製膜時間で変化させることで形成が可能である。
【００１７】
【実施例】
（実施例１）
トラックピッチ０．３５μｍ、１．１ｍｍ厚みポリカーボネート基板にメディア構成では図１のように保護層（１）（ＺｎＳ−ＳｉＯ２）を４０ｎｍ、記録層（１）のＳｂ６８Ｔｅ２９Ｇｅ３を１２ｎｍ、保護層（２）のＺｎＳＳｉＯ２層を１４ｎｍとＡｌＮｘを１００ｎｍ形成しその窒化量を時間とともに（膜厚方向に）変化させ、製膜時に窒素量を時間とともに増やし、膜厚方向に熱伝導率が傾斜した膜にした。
このＡｌＮｘの上に紫外線硬化樹脂のスピンコートによる樹脂層を２０μｍ、この樹脂層にスタンパーによる転写を硬化する前に行い、次に保護層（３）であるＺｎＳＳｉＯ２を７０ｎｍ、記録層（２）(Ａｇ６Ｉｎ７Ｓｂ６９Ｔｅ２４)を１０ｎｍ、保護層（４）のＺｎＳＳｉＯを１５ｎｍ、放熱層のＡｇＰｂＣｕを１２０ｎｍを順次、枚葉スパッタ装置にて成膜しさらにラジカルＵＶ樹脂で形成しメディア化した。
【００１８】
（比較例１）
トラックピッチ０．３５μｍ、１．１ｍｍ厚みポリカーボネート基板にメディア構成では図１のように保護層（１）（ＺｎＳ−ＳｉＯ２）を４０ｎｍ、記録層（１）Ｓｂ６８Ｔｅ２９Ｇｅ３を１２ｎｍ、保護層（２）ＺｎＳＳｉＯ２層を１４ｎｍとＡｌ−Ｔｉ（１ｗｔ％）の５ｎｍを枚葉スパッタ装置にて成膜し、紫外線硬化樹脂のスピンコートによる樹脂層を２０μｍ、この樹脂層にスタンパーによる転写を硬化する前に行い、次に保護層（３）であるＺｎＳＳｉＯ２を７０ｎｍ、記録層（２）(Ａｇ６Ｉｎ７Ｓｂ６９Ｔｅ２４)を１０ｎｍ、保護層（４）のＺｎＳＳｉＯを１５ｎｍ、放熱層のＡｇＴｉ（１ｗｔ％）を１２０ｎｍを順次、枚葉スパッタ装置にて成膜しさらにラジカルＵＶ樹脂で形成しメディア化した。
実施例１の結晶化を行うための初期化を８００ｍＷで処理し、記録再生を行った。評価条件４００ｎｍ，ＮＡ＝０．８５、６．０ｍ／ｓ、０．１４μｍ／ｂｉｔで評価した結果、記録層２層ともジッタ９．０％以下の良好な特性が得られた。比較例１は記録層（２）初期化後に記録層（１）が熱的なダメージを起こし良好に初期化ができず、記録再生特性が悪くジッタが１８．３％であった。
【００１９】
（実施例２）
トラックピッチ０．３５μｍ、１．１ｍｍ厚みポリカーボネート基板に、メディア構成では図１のように保護層（１）（ＺｎＳ−ＳｉＯ２）を４０ｎｍ、記録層（１）Ｓｂ６８Ｔｅ２９Ｇｅ３を１２ｎｍ、保護層（２）ＺｎＳＳｉＯ２層を１４ｎｍと酸化インジウム(Ｉｎ２Ｏ３)１５０ｎｍとＡｕ５ｎｍを枚葉スパッタ装置にて成膜し（正確な薄膜での熱伝導率は測定不能であるがＺｎＳＳｉＯ２＜ＩｎＯ ２ ＜Ａｕの順で熱伝導率が良い。）紫外線硬化樹脂のスピンコートによる樹脂層を２０μｍ、この樹脂層にスタンパーによる転写を硬化する前に行い、次に保護層（３）であるＺｎＳＳｉＯ２を７０ｎｍ、記録層（２）（Ａｇ６Ｉｎ７Ｓｂ６９Ｔｅ２４）を１０ｎｍ、保護層（４）のＺｎＳＳｉＯを１５ｎｍ、放熱層のＡｇＰｂＣｕを１２０ｎｍを順次、枚葉スパッタ装置にて成膜しさらにラジカルＵＶ樹脂で形成しメディア化した。
実施例１の結晶化を行うための初期化を８００ｍＷで処理し、記録再生を行った。評価条件４００ｎｍ、ＮＡ＝０．８５、６．０ｍ／ｓ、０．１４μｍ／ｂｉｔで評価した結果、記録層２層ともジッタ９．０％以下の良好な特性が得られた。熱伝導率の違う層が２層では比較例１のように熱的な遮断がうまくいかずに良好な記録再生特性が得られない。
【００２０】
（実施例３）
トラックピッチ０．３５μｍ、１．１ｍｍ厚みポリカーボネート基板にメディア構成では図１のように保護層（１）（ＺｎＳ−ＳｉＯ２）を４０ｎｍ、記録層（１）Ｓｂ６８Ｔｅ２９Ｇｅ３を１０ｎｍ、保護層（２）ＺｎＳＳｉＯ２層を１０ｎｍと（酸化インジウム（Ｉｎ２Ｏ３）２００ｎｍとＭｏＣｒを１２ｎｍを枚葉スパッタ装置にて成膜した。紫外線硬化樹脂のスピンコートによる樹脂層を２５μｍ、この樹脂層にスタンパーによる転写を硬化する硬化する前に行い、次に保護層（３）であるＺｎＳＳｉＯ２を７０ｎｍ、記録層（２）（Ａｇ１Ｉｎ３Ｓｂ６８Ｔｅ２４）を１０ｎｍ、保護層（４）のＺｎＳＳｉＯを１５ｎｍ、放熱層のＡｇＰｂＣｕを１２０ｎｍを順次、枚葉スパッタ装置にて成膜しさらにラジカルＵＶ樹脂で形成しメディア化した。
【００２１】
（比較例２）
トラックピッチ０．３５μｍ、１．１ｍｍ厚みポリカーボネート基板にメディア構成では図１のように保護層（１）（ＺｎＳ−ＳｉＯ２）を４０ｎｍ、記録層（１）ＳｂＴｅＧｅを１０ｎｍ、保護層（２）ＺｎＳＳｉＯ２層を１０ｎｍとＡｌ−Ｔｉ（１ｗｔ％）５ｎｍを枚葉スパッタ装置にて成膜し青色波長での透過率が（ＺｎＳＳｉＯ２が９８％、Ａｌ−Ｔｉで７３％であった、紫外線硬化樹脂のスピンコートによる樹脂層を２５μｍ、この樹脂層にスタンパーによる転写を硬化する前に行い、次に保護層（３）であるＺｎＳＳｉＯ２を７０ｎｍ、記録層（２）を１０ｎｍ、保護層（４）のＺｎＳＳｉＯを１５ｎｍ、放熱層のＡｇＴｉ（１ｗｔ％）を１２０ｎｍを順次、枚葉スパッタ装置にて成膜しさらにラジカルＵＶ樹脂で形成しメディア化した。
実施例３の場合、光入射側の記録層を評価条件実施例１記載の条件で記録後、記録層（２）の記録再生実験を行っても記録層（１）の記録された状態が保持されていた。
比較例２では記録層（１）のみの初期化や記録再生特性は実施例１記載の条件で評価するとジッタが９．２％と良好な特性を示したが、記録層（２）の初期化後、記録層（１）の記録再生特性はジッタ１８％と良くなかった。
【００２２】
（実施例４）
トラックピッチ０．３５μｍ、１．１ｍｍ厚みポリカーボネート基板にメディア構成では図１のように保護層（１）（ＺｎＳ−ＳｉＯ２）を１１０ｎｍ、記録層（１）Ｓｂ６８Ｔｅ２９Ｇｅ３を１２ｎｍ、保護層（２）ＺｎＳＳｉＯ２層を１０ｎｍとＳｉＣ１００ｎｍとＡｕ１２ｎｍを枚葉スパッタ装置にて成膜した。青色波長での各透過率はＺｎＳＳｉＯ２（９８％）＜ＳｉＣ（９４％）＜Ａｕ（７１％，反射率２９％）の順で透過率が良い。紫外線硬化樹脂のスピンコートによる樹脂層を２５μｍ、この樹脂層にスタンパーによる転写を硬化する硬化する前に行い、次に保護層（３）であるＺｎＳＳｉＯ２を７０ｎｍ、記録層（２）（Ａｇ１Ｉｎ３Ｓｂ６８Ｔｅ２４）を１０ｎｍ,保護層（４）のＺｎＳＳｉＯを１５ｎｍ、放熱層のＡｇＰｂＣｕを１２０ｎｍを順次、枚葉スパッタ装置にて成膜しさらにラジカルＵＶ樹脂で形成しメディア化した。
実施例４の場合、光入射側の記録層を評価条件実施例１記載の条件で記録後、記録層（２）の記録再生実験を行っても記録層（１）の記録された状態が保持されていた。
比較例２では記録層（１）のみの初期化や記録再生特性は実施例１記載の条件で評価するとジッタが９．２％と良好な特性を示したが、記録層（２）の初期化後、記録層（１）の記録再生特性はジッタ１８％と良くなかった。
【００２３】
（実施例５）
トラックピッチ０．３５μｍ、１．１ｍｍ厚みポリカーボネート基板にメディア構成では図１のように保護層（１）（ＺｎＳ−ＳｉＯ２）を１６０ｎｍ、記録層（１）Ｓｂ６８Ｔｅ２９Ｇｅ３を１２ｎｍ、保護層（２）ＺｎＳＳｉＯ２層を１０ｎｍとＡＴＯ１７０ｎｍとＡｕ１０ｎｍを枚葉スパッタ装置にて成膜した。青色波長での各透過率はＺｎＳＳｉＯ２（９８％）＜ＡＴＯ（９０％）＜Ａｕ（７２％，反射率２８％）の順で透過率が良い。紫外線硬化樹脂のスピンコートによる樹脂層を２５μｍ、この樹脂層にスタンパーによる転写を硬化する硬化する前に行い、次に保護層（３）であるＺｎＳＳｉＯ２を７０ｎｍ、記録層（２）(Ａｇ１Ｉｎ３Ｓｂ６８Ｔｅ２４)を１０ｎｍ、保護層（４）のＺｎＳＳｉＯを１５ｎｍ、放熱層のＡｇＰｄＣｕを１２０ｎｍを順次、枚葉スパッタ装置にて成膜しさらにラジカルＵＶ樹脂で形成しメディア化した。
実施例５の場合、光入射側の記録層を評価条件実施例１記載の条件で記録後、記録層（２）の記録再生実験を行っても記録層（１）の記録された状態が保持されていた。
比較例２では記録層（１）のみの初期化や記録再生特性は実施例１記載の条件で評価するとジッタが９.２％と良好な特性を示したが、記録層（２）の初期化後、記録層（１）の記録再生特性はジッタ１８％と良くなかった。
【００２４】
【発明の効果】
以上、詳細かつ具体的な説明から明らかなように、本発明により、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂＴｅを少なくとも含み、２つの記録層の間に熱伝導率の傾斜した層を有し、該保護層は、光入射側の熱伝導率が小さくすることで高密度記録が可能となり初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくできるので記録層２層とも良好で初期化が可能となり、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体が提供できる。
また、本発明により、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂ元素とＴｅ元素を少なくとも含み、２つの記録層の間に熱伝導率の違う層を３層以上設けることで高密度記録が可能となり初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくできるので記録層２層とも良好で初期化が可能となり、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体が提供できる。
また、本発明により、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂ元素とＴｅ元素を少なくとも含み、２つの記録層の間に熱伝導率の違う層を３層以上設け光入射側の層の熱伝導率を小さくすることで、初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくできるので記録層２層とも良好で初期化が可能となり、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体が提供できる。
また、本発明により、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、光の入射側の記録層がＳｂ元素とＴｅ元素を少なくとも含み、２つの記録層の間に、記録波長での透過率が違う層を３層以上設けることで初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくできるので記録層２層とも良好で初期化が可能となり、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体が提供できる。
また、本発明により、記録層２層間に形成した透過率が違う層３層以上のうち、光入射側の層の透過率を高くすることで初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくできるので記録層２層とも良好で初期化が可能となり、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体が提供できる。
また、本発明により、記録層２層間に形成した透過率が違う層３層以上のうち、光入射側とは反対側の光反射率が記録波長で５０％以下とすることで、光入射側への戻る光が少ないので初期化時に光入射方向から見て遠い側の記録層を初期化している場合、熱的に光入射側の記録層へ熱の干渉が少なくできるので記録層２層とも良好で初期化が可能となり、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体が提供できる。
さらにまた、本発明により、情報の記録、再生を行なう記録媒体において、基板上に記録層が少なくとも２層以上構成され、記録層に挟まれた層が酸化インジウム／酸化スズ複合酸化物（ＩＴＯ）、酸化スズ／酸化アンチモン複合酸化物（ＡＴＯ）、ＳｉＣ、ＶＯ、ＴｉＯｘ、ＺｒＯｘ、ＺｎＯｘから選ばれた１層以上の層と金属Ａｕ、Ｃｕ、Ｍｏ、Ｗもしくはこれらの合金の層を少なくとも含むことで初期化時に光入射方向から見て遠い側の記録層を初期化する場合、熱的に光入射側の記録層へ熱の干渉が少なくして初期化も可能になり、記録時も同様に記録層間の熱干渉を少なくできエラーが少ない相変化型記録媒体が提供できる。
【図面の簡単な説明】
【図１】本発明の実施の形態にかかる基板および光ディスクの構成を示した図である。
【符号の説明】
１ 記録層
１’ 保護層
２ 記録層
２’ 保護層
３ 保護層
４ 保護層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording medium used for a computer memory, a memory for image and sound files, an optical card, and the like, and more particularly to an information recording medium for recording or reproducing information by light such as a laser, and particularly to a high recording density. The present invention relates to a phase change type information recording medium excellent in conversion or sensitivity.
[0002]
[Prior art]
As an optical medium that can be recorded and reproduced by laser beam irradiation, there are a phase change medium using a crystal-amorphous transition and a dye medium using a reflectance difference due to dye-drilling. Conventionally, it has been easy to form two recording layers (pits) for a read-only medium from the light incident side with respect to an optical medium that can be recorded and reproduced. However, when two layers capable of recording / reproducing are provided, one layer must cause a contradictory phenomenon of recording by transmitting and absorbing light. Permeation is less absorbed at a normal film thickness, and if a thick heat dissipation layer is provided, light is not transmitted, and heat dissipation is not sufficient, so that it is difficult to become amorphous. For this reason, there has been a phenomenon in which high-speed recording is difficult and high-density recording is impossible. Also, since the recording layer is as narrow as 10 to 30 μm, thermal interference between the layers occurs at the time of initialization or recording, and sufficient recording / reproduction characteristics cannot be obtained even if the recording layer is initialized after the two layers are formed. It has been initialized to. However, when recording is performed on one of the recording layers, the data of the other recording layer is lost.
[0003]
Optical discs such as CD-R and CD-RW record sound, text and image signals along the circumferential direction on a plastic circular substrate such as polycarbonate, or a recording layer provided thereon, on the surface. A reflective layer is formed by vapor deposition or sputtering of a metal such as aluminum, gold, or silver. A laser beam is incident from the substrate surface side to record and reproduce signals. In recent years, since the amount of information handled by computers and the like has increased, the signal recording capacity of optical disks such as DVD-RAM and DVD-RW has increased and the density of signal information has increased. The recording capacity of a CD is about 650 MB and the DVD is about 4.7 GB, but further higher recording density is required in the future. It has been proposed to reduce the wavelength of the laser used to realize such a high recording density medium to the blue light region. However, as a conventional technique, there is no information on specific media even though the multilayering is described as disclosed in Japanese Patent Laid-Open No. 08-287474, or an example is disclosed in Japanese Patent Laid-Open No. 9-198709. Of the two phase change recording layers, the first light transmitting layer was SbSe, and the other layer was a recording layer made of Ge 2 Sb 2 Te 5 composition. Actually, it is known that the recording sensitivity is deteriorated from the viewpoint of high-speed recording, and it is difficult to perform high-density recording with the composition of Ge 2 Sb 2 Te 5 .
[0004]
[Problems to be solved by the present invention]
Accordingly, an object of the present invention is to provide a phase change information recording medium excellent in high speed and high recording density.
[0005]
[Means for Solving the Problems]
According to the first aspect of the present invention, in a recording medium for recording and reproducing information, at least two recording layers are formed on a substrate, the recording layer on the light incident side includes at least an Sb element and a Te element, two have a sloped layer of thermal conductivity between the recording layer, the protective layer, the method comprising: enabling high-density recording by the thermal conductivity of the light incident side is small, light incident upon initialization When the recording layer on the side far from the direction is initialized, thermal interference with the recording layer on the light incident side is thermally reduced so that the two recording layers can be initialized. It is an object of the present invention to provide a phase change type recording medium that can reduce thermal interference between layers and has few errors.
[0007]
According to a second aspect of the present invention, in the recording medium for recording and reproducing information, at least two recording layers are formed on the substrate, and the recording layer on the light incident side contains at least Sb element and Te element. Including three or more layers having different thermal conductivity between the two recording layers, and reducing the thermal conductivity of the light incident side layer so that the recording layer far from the light incident direction during initialization In the case of initialization, the thermal interference to the recording layer on the light incident side is thermally reduced so that the two recording layers can be initialized. Similarly, during recording, the thermal interference between the recording layers can be reduced and errors are reduced. A phase change recording medium is provided.
[0009]
According to a third aspect of the present invention, in the recording medium for recording and reproducing information, at least two recording layers are formed on the substrate, and the recording layer on the light incident side contains at least Sb element and Te element. In addition, among the three or more layers having different transmittances formed between the two recording layers, the recording layer on the far side as viewed from the light incident direction at the time of initialization is increased by increasing the transmittance of the layer on the light incident side. In the case of initialization, the thermal interference to the recording layer on the light incident side is thermally reduced so that the two recording layers can be initialized. Similarly, during recording, the thermal interference between the recording layers can be reduced and errors are reduced. A phase change recording medium is provided.
[0012]
A configuration of a substrate and an optical disk according to an embodiment of the present invention is shown in FIG.
The material of the substrate is usually glass, ceramics or resin, and the resin substrate is preferable in terms of moldability and cost. Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, etc. Polycarbonate resins and acrylic resins that are excellent in terms of moldability, optical characteristics, and cost are preferred. An uneven pattern is formed on one side of the substrate surface, and a heat-resistant layer, a recording layer, and the like are formed on this side. The thickness of the substrate is not particularly limited. When laser light is not irradiated from the substrate side, it is not necessary to consider optical characteristics, and polyethylene terephthalate having excellent rigidity is preferable.
[0013]
The protective layer (1), the protective layer (2), the protective layer (3), and the protective layer (4) have functions such as preventing deterioration and deterioration of the recording layer, increasing the adhesive strength of the recording layer, and improving the recording characteristics. SiO, SiO 2 , ZnO, SnO 2 , Al 2 O 3 , TiO 2 , In 2 O 3 , MgO, ZrO 2 and other metal oxides, Si 3 N 4 , AlN, TiN, BN, ZrN, etc. Examples thereof include nitrides, sulfides such as ZnS, In 2 S 3 , and TaS 4 , carbides such as TaC, B 4 C, WC, TiC, and ZrC, diamond-like carbon, and mixtures thereof. These materials can be used alone as a heat-resistant layer, but they may be mixed with each other. Moreover, you may contain an impurity as needed. The melting point of the heat-resistant layer needs to be higher than that of the recording layer. Such a heat-resistant layer can be formed by various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition, and the like. Among these, the sputtering method is excellent in mass productivity and film quality.
[0014]
Generally, a metal material such as Al, Au, Ag, Cu, Ta, or an alloy thereof can be used as the reflective heat dissipation layer. Further, Cr, Ti, Si, Cu, Ag, Pd, Ta or the like is used as an additive element. Such a reflective heat dissipation layer can be formed by various vapor phase growth methods, for example, vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition and the like. Among these, the sputtering method is excellent in mass productivity and film quality.
[0015]
The thin substrate is preferably in the form of a sheet because a thickness of 0.3 mm or less is required when using a high NA objective lens. Materials include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, etc. A polycarbonate resin and an acrylic resin, which are excellent in characteristics and cost, are preferable. Examples of a method for forming a light transmission layer using the transparent sheet include a method of attaching a transparent sheet via an ultraviolet curable resin or a transparent double-sided pressure-sensitive adhesive sheet. Alternatively, a light transmissive layer may be formed by applying an ultraviolet curable resin on the protective layer and curing it.
[0016]
In the recording medium that records and reproduces information in the layer configuration as described above, at least two recording layers are formed on the substrate, and the recording layer on the light incident side includes at least Sb element and Te element. When a recording layer on the side far from the light incident direction is initialized at the time of initialization, a layer with a gradient of thermal conductivity is provided between two recording layers to enable high-density recording, It is possible to provide a phase change type recording medium in which both the recording layers can be initialized by reducing heat interference with the recording layer on the incident side, and the heat interference between the recording layers can be similarly reduced during recording, thereby reducing errors. In addition, a method of forming a layer having a gradient thermal conductivity can be formed by changing the amount of nitrogen and the amount of oxygen in the nitride and oxide, respectively, with the film formation time.
[0017]
【Example】
(Example 1)
In a media configuration on a polycarbonate substrate having a track pitch of 0.35 μm and a thickness of 1.1 mm, as shown in FIG. 1, the protective layer (1) (ZnS—SiO 2 ) is 40 nm, the recording layer (1) Sb 68 Te 29 Ge 3 is 12 nm, The ZnSSiO 2 layer of the protective layer (2) is formed to 14 nm and AlNx is formed to 100 nm, and the nitriding amount is changed with time (in the film thickness direction), and the nitrogen amount is increased with time during film formation, and the thermal conductivity is increased in the film thickness direction. An inclined film was formed.
On this AlNx, a resin layer formed by spin coating of an ultraviolet curable resin is 20 μm, and this resin layer is formed before the transfer by a stamper is cured. Next, ZnSSiO 2 as a protective layer (3) is 70 nm, and the recording layer (2). (Ag 6 In 7 Sb 69 Te 24 ) 10 nm, ZnSSiO of the protective layer (4) 15 nm, AgPbCu of the heat dissipation layer 120 nm in this order by a single-wafer sputtering apparatus, and further formed with radical UV resin to form media did.
[0018]
(Comparative Example 1)
As shown in FIG. 1, the protective layer (1) (ZnS—SiO 2 ) is 40 nm, the recording layer (1) Sb 68 Te 29 Ge 3 is 12 nm, and the media is formed on a polycarbonate substrate having a track pitch of 0.35 μm and a thickness of 1.1 mm. the layer (2) ZnSSiO 2 layers were deposited 5nm of 14nm and Al-Ti (1wt%) in the single-wafer sputtering system, 20 [mu] m resin layer by spin-coating an ultraviolet curing resin, transcription by the stamper to the resin layer This is performed before curing, and then the protective layer (3) ZnSSiO 2 is 70 nm, the recording layer (2) (Ag 6 In 7 Sb 69 Te 24 ) is 10 nm, the protective layer (4) ZnSSiO is 15 nm, and the heat dissipation layer A film of AgTi (1 wt%) of 120 nm was sequentially formed with a single wafer sputtering apparatus and further formed with a radical UV resin to form a medium.
Initialization for crystallization in Example 1 was processed at 800 mW, and recording / reproduction was performed. As a result of evaluation under the evaluation conditions of 400 nm, NA = 0.85, 6.0 m / s, and 0.14 μm / bit, good characteristics with a jitter of 9.0% or less were obtained in both recording layers. In Comparative Example 1, the recording layer (1) was thermally damaged after initialization of the recording layer (2) and could not be initialized satisfactorily, the recording / reproduction characteristics were poor, and the jitter was 18.3%.
[0019]
(Example 2)
A polycarbonate substrate having a track pitch of 0.35 μm and a thickness of 1.1 mm has a media structure of 40 nm for the protective layer (1) (ZnS—SiO 2 ), 12 nm for the recording layer (1) Sb 68 Te 29 Ge 3 as shown in FIG. Protective layer (2) A ZnSSiO 2 layer of 14 nm, indium oxide (In 2 O 3 ) 150 nm, and Au 5 nm was formed by a single wafer sputtering apparatus (although the thermal conductivity in an accurate thin film cannot be measured, ZnSSiO 2 < The thermal conductivity is good in the order of InO 2 <Au.) The resin layer by spin coating of UV curable resin is 20 μm, and this resin layer is subjected to hardening before transfer by a stamper, and then the protective layer (3) ZnSSiO 2 70 nm, the recording layer (2) (Ag 6 in 7 Sb 69 Te 24) of 10 nm, 15 nm to ZnSSiO protective layer (4), the heat dissipation layer The gPbCu sequentially 120 nm, and the media of formed film formation further radical UV resins in sheet sputtering apparatus.
Initialization for crystallization in Example 1 was processed at 800 mW, and recording / reproduction was performed. As a result of evaluation under evaluation conditions of 400 nm, NA = 0.85, 6.0 m / s, and 0.14 μm / bit, good characteristics with a jitter of 9.0% or less were obtained in both recording layers. When two layers having different thermal conductivities are used, the thermal shutoff does not work as in Comparative Example 1, and good recording / reproducing characteristics cannot be obtained.
[0020]
(Example 3)
As shown in FIG. 1, the protective layer (1) (ZnS—SiO 2 ) is 40 nm, the recording layer (1) Sb 68 Te 29 Ge 3 is 10 nm, and the medium is formed on a polycarbonate substrate having a track pitch of 0.35 μm and a thickness of 1.1 mm. layer (2) ZnSSiO 2 layers and 10nm (the indium oxide (in 2 O 3) 200nm and 12nm the MoCr film was formed by single wafer sputtering apparatus. 25 [mu] m resin layer by spin coating of ultraviolet curing resin, the resin This is performed before curing by transferring the stamper to the layer, and then the protective layer (3) ZnSSiO 2 is 70 nm, the recording layer (2) (Ag 1 In 3 Sb 68 Te 24 ) is 10 nm, and the protective layer (4 ) ZnSSiO 15nm, heat dissipation layer AgPbCu 120nm in order, using a single wafer sputtering system, and further radical UV resin Formed with fat and made into media.
[0021]
(Comparative Example 2)
In a media configuration on a polycarbonate substrate having a track pitch of 0.35 μm and a thickness of 1.1 mm, as shown in FIG. 1, the protective layer (1) (ZnS—SiO 2 ) is 40 nm, the recording layer (1) SbTeGe is 10 nm, and the protective layer (2) ZnSSiO Two layers of 10 nm and Al—Ti (1 wt%) 5 nm are formed by a single wafer sputtering apparatus, and the transmittance at blue wavelength is 98% for ZnSSiO 2 and 73% for Al—Ti. The resin layer by spin coating of 25 μm is performed before the transfer by the stamper is cured on this resin layer, and then the protective layer (3) ZnSSiO 2 is 70 nm, the recording layer (2) is 10 nm, and the protective layer (4) A ZnSSiO film of 15 nm and a heat dissipation layer of AgTi (1 wt%) of 120 nm were sequentially formed with a single wafer sputtering apparatus and further formed with a radical UV resin. And A reduction.
In the case of Example 3, after the recording layer on the light incident side was recorded under the conditions described in Evaluation Example 1, the recorded state of the recording layer (1) was maintained even when a recording / reproducing experiment of the recording layer (2) was performed. It had been.
In Comparative Example 2, the initialization and recording / reproduction characteristics of only the recording layer (1) showed good characteristics with a jitter of 9.2% when evaluated under the conditions described in Example 1. The initialization of the recording layer (2) was performed. After that, the recording / reproducing characteristic of the recording layer (1) was not good with a jitter of 18%.
[0022]
(Example 4)
As shown in FIG. 1, the protective layer (1) (ZnS—SiO 2 ) is 110 nm, the recording layer (1) Sb 68 Te 29 Ge 3 is 12 nm, and protection is performed on a polycarbonate substrate with a track pitch of 0.35 μm and a thickness of 1.1 mm. Layer (2) A ZnSSiO 2 layer having a thickness of 10 nm, SiC of 100 nm and Au of 12 nm was formed using a single wafer sputtering apparatus. Each transmittance at the blue wavelength is good in the order of ZnSSiO 2 (98%) <SiC (94%) <Au (71%, reflectance 29%). The resin layer by spin coating of UV curable resin is 25 μm, which is performed before curing to cure the transfer by the stamper to this resin layer, and then the protective layer (3) ZnSSiO 2 is 70 nm, the recording layer (2) (Ag 1 In 3 Sb 68 Te 24 ), ZnSSiO of the protective layer (4) of 15 nm, and AgPbCu of the heat dissipation layer of 120 nm were sequentially formed with a single wafer sputtering apparatus and further formed with radical UV resin to form a media.
In the case of Example 4, after the recording layer on the light incident side was recorded under the conditions described in the evaluation conditions of Example 1, the recorded state of the recording layer (1) was maintained even when the recording layer (2) was recorded and reproduced. It had been.
In Comparative Example 2, the initialization and recording / reproduction characteristics of only the recording layer (1) showed good characteristics with a jitter of 9.2% when evaluated under the conditions described in Example 1. The initialization of the recording layer (2) was performed. After that, the recording / reproducing characteristic of the recording layer (1) was not good with a jitter of 18%.
[0023]
(Example 5)
In a media configuration on a polycarbonate substrate with a track pitch of 0.35 μm and a thickness of 1.1 mm, the protective layer (1) (ZnS—SiO 2 ) is 160 nm, the recording layer (1) Sb 68 Te 29 Ge 3 is 12 nm, as shown in FIG. Layer (2) A ZnSSiO 2 layer having a thickness of 10 nm, ATO 170 nm and Au 10 nm was formed using a single wafer sputtering apparatus. Each transmittance at the blue wavelength is good in the order of ZnSSiO 2 (98%) <ATO (90% ) < Au (72%, reflectance 28%). The resin layer by spin coating of UV curable resin is 25 μm, which is performed before curing to cure the transfer by the stamper on this resin layer, and then the protective layer (3) ZnSSiO 2 is 70 nm, the recording layer (2) (Ag 1 In 3 Sb 68 Te 24 ), ZnSSiO of the protective layer (4) of 15 nm, and AgPdCu of the heat dissipation layer of 120 nm were sequentially formed with a single-wafer sputtering apparatus, and further formed with radical UV resin to form a media.
In the case of Example 5, after recording the recording layer on the light incident side under the conditions described in the evaluation condition Example 1, the recorded state of the recording layer (1) is maintained even if the recording layer (2) is recorded and reproduced. It had been.
In Comparative Example 2, the initialization and recording / reproducing characteristics of only the recording layer (1) showed good characteristics of 9.2% when evaluated under the conditions described in Example 1. The initialization of the recording layer (2) was performed. After that, the recording / reproducing characteristic of the recording layer (1) was not good with a jitter of 18%.
[0024]
【The invention's effect】
As is apparent from the detailed and specific description above, according to the present invention, in the recording medium for recording and reproducing information, at least two recording layers are formed on the substrate, and the recording layer on the light incident side is provided. at least include SbTe, have a layer formed by the slope of the thermal conductivity between the two recording layers, the protective layer, at initialization enables high-density recording in to Rukoto thermal conductivity of the light incident side is small When the recording layer on the side far from the light incident direction is initialized, thermal interference with the recording layer on the light incident side can be reduced thermally, so both recording layers are good and can be initialized. Similarly, it is possible to provide a phase change recording medium with less heat interference between the recording layers and less errors.
According to the present invention, in the recording medium for recording and reproducing information, at least two recording layers are formed on the substrate, and the recording layer on the light incident side includes at least Sb element and Te element. By providing three or more layers with different thermal conductivity between the layers, high-density recording is possible, and when the recording layer on the side far from the light incident direction is initialized during initialization, Therefore, the two recording layers are good and can be initialized, and also during recording, a thermal change between the recording layers can be reduced and a phase change recording medium with few errors can be provided.
According to the present invention, in the recording medium for recording and reproducing information, at least two recording layers are formed on the substrate, and the recording layer on the light incident side includes at least Sb element and Te element. When three or more layers with different thermal conductivities are provided between the layers and the thermal conductivity of the light incident side layer is reduced to initialize the recording layer far from the light incident direction during initialization Since the thermal interference to the recording layer on the light incident side can be reduced thermally, both the recording layers are good and can be initialized, and during recording, the thermal interference between the recording layers can be reduced and errors can be reduced. A recording medium can be provided.
According to the present invention, in the recording medium for recording and reproducing information, at least two recording layers are formed on the substrate, and the recording layer on the light incident side includes at least Sb element and Te element. When three or more layers having different transmittances at the recording wavelength are provided between the layers, the recording layer on the side far from the light incident direction is initialized at the time of initialization. Since the heat interference with the recording layer can be reduced, the two recording layers can be satisfactorily initialized and the phase change type recording medium can be provided which can reduce the thermal interference between the recording layers and reduce errors during recording.
According to the present invention, among the three or more layers having different transmittances formed between the two recording layers, the recording on the far side as viewed from the light incident direction at the time of initialization is made by increasing the transmittance of the light incident side layer. When the layers are initialized, thermal interference with the recording layer on the light incident side can be reduced thermally, so that both recording layers are good and can be initialized. Similarly, during recording, thermal interference between the recording layers is reduced. And a phase change recording medium with few errors can be provided.
Further, according to the present invention, the light reflectance on the side opposite to the light incident side among the three or more layers having different transmittances formed between the recording layers 2 is set to 50% or less at the recording wavelength. When the recording layer on the side far from the light incident direction is initialized at the time of initialization because there is little light returning to the recording layer, it is possible to reduce thermal interference with the recording layer on the light incident side. A phase change type recording medium can be provided that is favorable and can be initialized, and that can similarly reduce thermal interference between recording layers and reduce errors during recording.
Furthermore, in the recording medium for recording and reproducing information according to the present invention, at least two recording layers are formed on the substrate, and the layer sandwiched between the recording layers is indium oxide / tin oxide composite oxide (ITO). At least one layer selected from tin oxide / antimony oxide composite oxide (ATO), SiC, VO, TiOx, ZrOx, ZnOx and a layer of metal Au, Cu, Mo, W or an alloy thereof. When initializing the recording layer on the side far from the light incident direction during initialization, it is possible to initialize with less thermal interference with the recording layer on the light incident side. It is possible to provide a phase change recording medium that can reduce thermal interference between recording layers and has few errors.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a substrate and an optical disc according to an embodiment of the present invention.
[Explanation of symbols]
1 recording layer 1 'protective layer 2 recording layer 2' protective layer 3 protective layer 4 protective layer
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001284178A JP4223703B2 (en) | 2001-09-18 | 2001-09-18 | Phase change information recording medium |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001284178A JP4223703B2 (en) | 2001-09-18 | 2001-09-18 | Phase change information recording medium |
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| Publication Number | Publication Date |
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| JP2003091870A JP2003091870A (en) | 2003-03-28 |
| JP4223703B2 true JP4223703B2 (en) | 2009-02-12 |
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| JP2001284178A Expired - Fee Related JP4223703B2 (en) | 2001-09-18 | 2001-09-18 | Phase change information recording medium |
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| TW200534235A (en) | 2004-03-10 | 2005-10-16 | Matsushita Electric Ind Co Ltd | Information recording medium and method for manufacturing the same |
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