JP2004259406A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium having high long term preservation stability of recorded information. <P>SOLUTION: A high density optical information recording medium is provided in which a recording layer with a robust fullerene-based skeleton having an extremely high decomposition temperature as a major component is selected on a transparent substrate, the recording layer capable of forming a recording pit, at an interface adjacent to the recording layer, associated with satisfactory physical deformation and/or modification caused by heat generation of the recording layer due to laser beam irradiation. The optical information recording medium realizes high density recording/reproduction using an optical head having a laser of a wavelength of 390 to 700 nm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３２】
〔式中、Ｒ １ 、Ｒ ２ はそれぞれ独立に、水素原子、ハロゲン原子、シアノ基、置換基を有していてもよいアルキル基、アラルキル基、アルケニル基、アルキニル基、アリール基、アルコキシ基、アラルキルオキシ基、アリールオキシ基、アルケニルオキシ基、アシル基、アミノ基、アミノカルボニル基、シリル基、ホスフィノ基、複素環基を表し、Ｒ １ 、Ｒ ２ は連結基を介して、それぞれ併せて環を形成してもよく、また、Ｒ １ 、Ｒ ２ あるいはフラーレン骨格のいずれか１ つ以上が金属錯体化していてもよい。ｎ は、１ 乃至３ の整数を表す。また、熱分解促進剤としてメタロセニル基をＲ１，Ｒ２の置換基に用いても良い。〕
本発明に用いられる一般式（１）で示されるフラーレン系化合物は、限定されないが、例えば季刊化学総説ＮＯ．４３（１９９９）等に記載の方法に準じて製造することができる。
【００３３】
なお本発明のフラーレン系化合物には、多量体のフラーレン系化合物も含まれる。具体的には、式（１）のフラーレン系化合物２個以上が、少なくとも１種以上の連結基を介して結合、或いは直接単結合し、連結していてもよい。連結基の例としては、置換しても良いメチレン基、置換しても良いメチン基、置換しても良いエチニレン基、置換しても良いフェニレン基、アミノ基、イミノ基、酸素原子または硫黄原子等が挙げられる。これらの連結基により表される連結基群１〜４個を介して式（１）で表されるフラーレン系化合物が連結していても良い。なお、これら高次フラーレンについての含有量は特に限定しない。
【００３４】
用いるフラーレン系色素としては、Ｃ６０，Ｃ７０，Ｃ８２，Ｃ１２０等、特に限定されるものではないが、大量合成が可能なＣ６０フラーレン系化合物が最も好ましい。
【００３５】
記録層に使用されるフラーレン系化合物を同定する方法として、記録膜を単離した後、ＵＶスペクトル、ＦＤ−ＭＳ、ＮＭＲ、ＴＯＦ−ＳＩＭＳ、ＳＮＯＭ、ラマン分光、ＦＴ−ＩＲ等の方法を用いることが可能であるが、フラーレン単体であれば、ベンゼン、トルエンに微量溶解することから、ＴＬＣ分取後、液体クロマトグラフィーによる同定も簡便で確実な方法として有効である。
【００３６】
本発明の光記録媒体を構成している記録層は、実質的に１種またはそれ以上のフラーレン系化合物、特にＣ６０単体あるいは式（１）の化合物からなるものであり、さらに、所望に応じて波長２９０ｎｍ 〜６９０ｎｍ に吸収極大を持ち、３００ｎｍ 〜７００ｎｍ での屈折率が大きい前記以外の化合物と混合しても良い。具体的には、シアニン系化合物、スクアリリウム系化合物、ナフトキノン系化合物、アントラキノン系化合物、テトラピラポルフィラジン系化合物、インドフェノール系化合物、ピリリウム系化合物、チオピリリウム系化合物、アズレニウム系化合物、トリフェニルメタン系化合物、キサンテン系化合物、インダスレン系化合物、インジゴ系化合物、チオインジゴ系化合物、メロシアニン系化合物、チアジン系化合物、アクリジン系化合物、オキサジン系化合物、ジピロメテン系化合物、オキサゾール系、アザポルフィリン系、ポルフィリン系、ポルフィセン系などがあり、複数の化合物の混合であっても良い。これらの化合物の混合割合は、０ ．１ 質量％〜３０ 質量％程度である。
【００３７】
記録層に用いられるフラーレン単体、あるいは一般式（１ ）に示されるフラーレン系化合物の含有量は、記録・再生が可能な任意の量を選択することができるが、通常、３０ ％以上、好ましくは６０ ％以上である。尚、実質的に１００ ％であることも好ましい。
【００３８】
記録層を設ける方法は、例えば、スピンコート法、スプレー法、キャスト法、スライド法、カーテン法、エクストルージョン法、ワイヤー法、グラビア法、スプレッド法、ローラーコート法、ナイフ法、浸漬法などの塗布法、スパッタ法、ＥＢ蒸着法、化学蒸着法、真空蒸着法などが挙げられる。
【００３９】
一般に、Ｃ６０等フラーレン化合物単体の場合には、それ自身溶剤に極めて溶解しにくいことが多いため、スパッタ法、ＥＢ蒸着法、化学蒸着法や真空蒸着法等がむしろ適する。また、基板にダメージを与えない溶媒を選択できない場合も、スパッタ法、ＥＢ蒸着法、化学蒸着法や真空蒸着法などが有効であった。
【００４０】
ここで、Ｃ６０フラーレン薄膜の形成には、とりわけ蒸着法が好ましく、Ｍｏ、Ｗボートの加熱電流精密制御により，０．０１ｎｍ〜０．１ｎｍ／秒範囲で蒸着製膜速度を達成することで均質な膜形成が実現された。
【００４１】
記録層を基板の上に成膜する際に、隣接して用いる基板の材質としては、図６に示すような基板１１を通じてレーザー照射が行われることも加味すれば、基本的には記録光および再生光の波長で透明であって、支持基板としての機械強度を有しており、且つ、融点・分解点が３００℃以上、ガラス転移温度が１００℃以上ものから適用されることが望ましい。このため具体的な材質としては、例えば、アクリル樹脂、ポリエチレン樹脂、ポリカーボネート樹脂、ポリオレフィン樹脂、エポキシ樹脂等の高分子材料が利用される。
一方、図７に示す構成のように、基板１１ ’とは逆の光透過層１５ ’側からレーザー照射が行われる場合、基板の材質としては光学的諸要件を満たす必要はなく、より広範な材料から選択することができる。基板に要求される機械的特性、また基板生産性の観点からは、アクリル樹脂、ポリカーボネート樹脂、ポリオレフィン樹脂等の射出成型或いはキャスト成型可能な材料が好ましい。これらの基板材料は射出成形法等により円盤状に基板に成形してもよい。
【００４２】
通常、これらの基板の表層には、サブミクロンオーダーの案内溝及び／又はプレピットが螺旋状又は同心円上に形成される。これら案内溝及びプレピットは、基板形成時に付与されているのが好ましく、スタンパー原盤を用いての射出成型や、フォトポリマーを用いた熱転写法により付与することができる。尚、図７における光透過層１５ ’に案内溝及び／又はプレピットを形成しても良く、付与する場合も同様の方法を適用できる。案内溝のピッチ及び深さは、ＤＶＤ よりも高密度記録を行うＨＤ −ＤＶＤＲ の場合、ピッチとして０．２５ 〜０．８０μｍ 、深さとして２０ 〜１５０ｎｍの範囲から、より好ましくは３０ｎｍ〜１００ｎｍの範囲から選択するのが好ましい。この記録時の変形量制御を目的に、基板の上には無機物やポリマーからなる層を設けても良い。本発明者らの詳細検討に拠れば、当該隣接層は適度な熱硬度及び粘弾性を有し、変形緩衝しうる隣接界面（層）の形成が好ましい。
【００４３】
尤も、フラーレン化合物を上述の適正な膜厚設定で適正な溝形状を有すポリカーボネート基板上に直接成膜し、記録時の変形痕跡をその基板表層に直接形成してやることでも良好な高密度記録は十分に確認できた。
【００４４】
フラーレン化合物を含む記録層に隣接する層としては有機膜が好ましい。記録ピットが形成されやすいからである。更に、フラーレン化合物を含む記録層と隣接して、例えば明確な温度閾値を有して熱変性するような有機色素膜やポリマーを積層して用いることがより好ましい。記録光の入射側にある基板と記録層との間に形成すれば、フラーレン化合物からの発熱を当該色素・ポリマー層に熱転写し、その色素、ポリマーを変性させることによる記録も可能となった。用いる色素の光学定数の設計次第では良好な信号振幅で高密度信号の獲得が可能となった。またポリマー層は透明であってもよい。これ自体がフラーレンを含む記録層からの熱で記録ピットが形成されて、長期保存性を高められる。
【００４５】
適用可能な色素種として具体的には、シアニン系化合物、スクアリリウム系化合物、ナフトキノン系化合物、アントラキノン系化合物、テトラピラポルフィラジン系化合物、インドフェノール系化合物、ピリリウム系化合物、チオピリリウム系化合物、アズレニウム系化合物、トリフェニルメタン系化合物、キサンテン系化合物、インダスレン系化合物、インジゴ系化合物、チオインジゴ系化合物、メロシアニン系化合物、チアジン系化合物、アクリジン系化合物、オキサジン系化合物、ジピロメテン系化合物、オキサゾール系、アザポルフィリン系、ポルフィリン系、ポルフィセン系などがあり、複数の化合物の混合であっても良い。
【００４６】
これら色素種はフラーレン系薄膜と相溶しないよう溶媒極性を変えた溶液系からスピンコートするか、あるいは真空系の成膜方法により積層された。積層膜厚は、記録波長に合わせた光学デザイン（反射率、変調度）が考慮され最適化された。
【００４７】
記録層色素膜厚の定量的な測定に関しては、最近ガリウムイオンビーム等で端面のエッチングを施した後、ＳＥＭ、あるいはＴＥＭで観察するといった精度の良い方法が利用され始めた。（ＦＩＢ−ＳＥＭ，ＦＩＢ−ＴＥＭ） この手法のメリットとして、凍結破断等で対象物の切片を出して色素膜厚を測定する従来の方法と比較して、硬度が極めて低く端面の正確な厚みを測定することができなかったものまで、正確な層構造を反映させて色素膜厚を測定することが可能となる。
【００４８】
記録層がレーザー光照射により膜の熱モード物理変形を伴って記録されているか否かに関しては、記録層界面を丁寧に剥離させた後、ピット形成部を ＳＥＭ、あるいはＴＥＭ、あるいはＡＦＭによって形態観察するのが一般的である。特に基板の物理変形痕を観察するためには、記録層剥離後にヘプタン、あるいはジメチルシクロヘキサン等の有機溶剤に約１時間浸して記録層を概略除去した後に、ＳＥＭ観察，あるいはＡＦＭ観察を行うことが有効である。さらに、記録後の記録層からの酸化物検出には、ピット形成微小部位の、ＴＯＦ−ＳＩＭＳ、ＳＮＯＭ、顕微ラマン等の極微小領域での分析が有効である。
【００４９】
次に記録層とは隣接して反射層を形成しても良い。該反射層を形成する場合の膜厚は、通常１０ｎｍ 〜２００ｎｍ の厚さにするのが好ましい。反射率を高めるためや密着性をよくするために、そして信号品位の改善を目的に、記録層と反射層の間には反射増幅層や接着層、変形緩衝層を設けることができる。反射層の材料としては、再生光の波長で反射率の十分高いもの、例えば、Ａｕ、Ａｌ、Ａｇ、Ｃｕ、Ｔｉ、Ｃｒ、Ｎｉ、Ｐｔ、Ｔａ、Ｒｈ およびＰｄ の金属を単独あるいは合金にして用いることが可能である。この中でもＡｕ、Ａｇ、Ｐｔ、Ｃｕ、Ａｌ、Ｎｉ、Ｒｈは反射率が高く反射層の材料として適している。青色レーザーでの記録・再生を行う場合には、Ａｌ またはＡｇ が好適である。これ以外でも下記のものを含んでいても良い。例えば、Ｍｇ、Ｓｅ、Ｈｆ、Ｖ、Ｎｂ、Ｒｕ、Ｗ、Ｍｎ、Ｒｅ、Ｆｅ、Ｃｏ、Ｉｒ、Ｚｎ、Ｃｄ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｔｅ、Ｐｂ、Ｐｏ、Ｓｎ、Ｂｉなどの金属および半金属を挙げることができる。また、Ａｇ またはＡｌ を主成分とするものは反射率の高い反射層が容易に得られるため好適である。金属以外の材料で低屈折率薄膜と高屈折率薄膜を交互に積み重ねて多層膜を形成し、反射層として用いることも可能である。
【００５０】
反射層を形成する方法としては、例えば、スパッタ法、イオンプレーティング法、化学蒸着法、真空蒸着法などが挙げられる。また、基板の上や反射層の下に反射率の向上、記録特性の改善、密着性の向上などのために公知の無機系または有機系の中間層、接着層を設けることもできる。
【００５１】
さらに、記録層そして反射層は、通常、保護層により保護される。該保護層の材料としては反射層を外力から保護するものであれば特に限定しない。無機物質としては、ＳｉＯ_２ 、Ｓ_３Ｎ_４ 、ＭｇＦ_２ 、ＡｌＮ 、ＳｎＯ_２ などが挙げられる。また、有機物質としては、熱可塑性樹脂、熱硬化性樹脂、電子線硬化性樹脂、紫外線硬化性樹脂などを挙げることができる。熱可塑性樹脂、熱硬化性樹脂などは適当な溶媒に溶解して塗布液を調製した後に、この塗布液を塗布し、乾燥することによって形成することができる。紫外線硬化性樹脂はそのままもしくは適当な溶媒に溶解して塗布液を調製した後に、この塗布液を塗布し、紫外線を照射して硬化させることによって形成することができる。紫外線硬化性樹脂としては、例えば、ウレタンアクリレート、エポキシアクリレート、ポリエステルアクリレートなどのアクリレート樹脂を用いることができる。これらの材料は単独であるいは混合して用いても良く、１層だけでなく多層膜にして用いても良い。
【００５２】
保護層の形成の方法としては、記録層と同様にスピンコート法やキャスト法などの塗布法やスパッタ法や化学蒸着法などの方法が用いられるが、この中でもスピンコート法が好ましい。
保護層の膜厚は、一般には０．１μｍ 〜１００μｍ の範囲であるが、本発明においては、３μｍ 〜３０μｍ であり、より好ましくは、５μｍ 〜２０μｍ である。
【００５３】
保護層の上にさらにレーベル、バーコードなどの印刷を行うこともできる。
また、反射層面に保護シートまたは基板を貼り合わせる、あるいは反射層面相互を内側とし対向させ、光記録媒体２枚を貼り合わせるなどの手段を用いても良い。基板鏡面側に、表面保護やごみ等の付着防止のために紫外線硬化性樹脂、無機系薄膜等を成膜しても良い。
【００５４】
ここで、本発明で言う波長３９０ｎｍ 〜７００ｎｍのレーザーは、特に制限はないが、例えば、可視光領域の広範囲で波長選択のできる色素レーザーや、波長４００ 〜４１０ｎｍのＧａＮ系レーザー、ＣｒドープしたＬｉＳｎＡｌＦ_６ を用いた波長８６０ｎｍ の赤外線レーザーの第２高調波４３０ｎｍ を発振するレーザー他、波長４０５ｎｍ、４１５ｎｍ、４２５ｎｍ 等の可視半導体レーザー等の半導体レーザー等があげられる。本発明では、上述の半導体レーザー等を記録または再生を行う記録層の感応する波長に応じて適宜選択することができる。高密度記録および再生は各々、上述の該半導体レーザーから選択される１波長または複数波長において可能となる。
【００５５】
このように記録層がフラーレンを含み、記録時の発熱で隣接する層あるいは透明層に記録ピットを形成しうる光記録媒体は、高い耐光性から従来に比べてさらに記録情報の長期保存性が高くなる。次に、その記録特性を高めるための媒体設計の例のいくつかを以下に示す。
【００５６】
（実施例１）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．７４μｍ、溝幅：０．３３μｍ、溝深さ：５０ｎｍ）を有する外径１２０ｍｍ φ、厚さ０．６ｍｍ の円盤状の基板上に、真空蒸着法で下記（化式２）で示されるフラーレン Ｃ６０（東京化成工業社製 ＞９９．９％）を蒸着して、厚さ４０ｎｍとなるように記録層を成膜した。
【００５７】
【化式２】

【００５８】
この記録層の上にバルザース社製スパッタ装置（ＣＤＩ −９００ ）を用いて銀をスパッタし、厚さ１５０ｎｍ の反射層を形成した。スパッタガスにはアルゴンガスを用いた。スパッタ条件は、スパッタパワー２ ．５ｋＷ 、スパッタガス圧１．３３Ｐａ （１ ．０ ×１０^−２Ｔｏｒｒ ）で行った。
【００５９】
さらに、反射層の上に紫外線硬化樹脂ＳＤ−１７（大日本インキ化学工業製）をスピンコートした後、紫外線照射して厚さ５μｍ の保護層を形成した。更に、保護層の上に紫外線硬化樹脂デソライトＫＺ−８６８１（ＪＳＲ製）をスピンコートした後、前記基板と同様な案内溝のないポリカーボネート樹脂基板をのせ、紫外線照射して基板を貼り合わせ、光記録媒体を作製した。
【００６０】
以上のようにして記録層が形成された光記録媒体について、以下のように評価試験を行った。 波長４０５ｎｍ、開口数０．６５の青色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速５．３ｍ／ｓにて１−７ＲＬＬの２Ｔ相当（最小ピット長＝０．２３μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にてグルーブ（溝中）へ記録を実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１４ｍＷで、２ＴＣＮＲ＝５６ｄＢ、変調度＝０．２８と極めて良好な結果が観測された。
【００６１】
引き続いて、同じ光学ピックアップを用い、１−７ＲＬＬの８Ｔ相当（ピット長＝０．９２μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１４ｍＷで、８ＴＣＮＲ＝６０ｄＢ、変調度＝０．８１と良好な結果が観測された。
【００６２】
当該媒体を対象に１−７ＲＬＬランダム信号を記録ストラテジーの最適化により実施し、非常に良好なジッター６．６％を測定した。その際、採取のアイパターンを図８に示す。
【００６３】
一方、フラーレン Ｃ６０単体の窒素雰囲気下での熱重量分析（ＴＧＡ）を行った結果、該記録層化合物の２０ｗｔ％減量時における熱分解温度は、６００℃以上を有し、極めて熱的に安定な堅牢な化合物であることが確認された。
【００６４】
また、当該光記録媒体を記録界面にて剥離して、界面をＳＥＭで観察した結果、記録ピット部位で物理変形を起こして、物理ピットが形成されていることを確認した。
図９には、その際のポリカーポネート基板上に形成された記録ピットの痕跡を示す。
【００６５】
また、当該光記録媒体を記録界面にて剥離して、界面記録ピット部位のＴＯＦ−ＳＩＭＳ分析を行った結果、Ｃ６０の酸化物に帰属されるピークが確認された。 信号評価結果を表１にまとめる。
【００６６】
（実施例２）
フラーレンＣ６０の記録層を膜厚２５ｎｍに成膜する以外は、実施例１と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例１と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１４ｍＷの時の信号品位は、２ＴＣＮＲ＝５４ｄＢと良好なものであった。
【００６７】
引き続いて、同じ光学ピックアップを用い、実施例１と同様に１−７ＲＬＬの８Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１４ｍＷの時の信号品位は、８ＴＣＮＲ＝５５ｄＢと良好なものであった。結果を表１にまとめる。
【００６８】
当該媒体を対象に１−７ＲＬＬランダム信号を記録ストラテジーの最適化により実施し、非常に良好なジッター７．４％を測定した。
【００６９】
（実施例３）
フラーレンＣ６０の記録層を膜厚６０ｎｍに成膜する以外は、実施例１と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例１と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、２ＴＣＮＲ＝４７ｄＢと良好なものであった。
【００７０】
引き続いて、同じ光学ピックアップを用い、実施例１と同様に１−７ＲＬＬの８Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、８ＴＣＮＲ＝６０ｄＢと良好なものであった。結果を表１にまとめる。
【００７１】
当該媒体を対象に１−７ＲＬＬランダム信号を記録ストラテジーの最適化により実施し、良好なジッター８．３％を測定した。
【００７２】
（参考例１）
フラーレンＣ６０の記録層を膜厚１５ｎｍに成膜する以外は、実施例１と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例１と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、未記録状態で信号にノイズが乗っており、そこに記録を施しても良好な信号は確認できなかった。１５ｎｍまで薄くなると均一な連続膜ができなかったためと思われる。
結果を表１にまとめる。
【００７３】
（参考例２）
フラーレンＣ６０の記録層を膜厚６５ｎｍに成膜する以外は、実施例１と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例１と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、ピット間の熱干渉の影響が大きく良好なピットが形成されなかった。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、２ＴＣＮＲ＝３８ｄＢであり、短ピットの熱干渉によるピットの潰れを確認した。２Ｔ変調度も０．１５以下であった。
【００７４】
引き続いて、同じ光学ピックアップを用い、実施例１と同様に１−７ＲＬＬの８Ｔ相当の評価試験を行ったところ、短ピット挙動とは異なり、良好にピットが形成された。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、８ＴＣＮＲ＝６０ｄＢ、変調度＝０．８５であった。結果を表１にまとめる。
【００７５】
（実施例４）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．７４μｍ、溝幅：０．３３μｍ、溝深さ：５０ｎｍ）を有する外径１２０ｍｍ φ、厚さ０．６ｍｍ の円盤状の基板上に真空蒸着法で直接、実施例１で使用されたものと同様のフラーレンＣ６０を蒸着して、厚さ４０ｎｍ となるように記録層を成膜した。この記録層の上には特に反射層、保護層等は設けずにエアーオープン系とし、エアーギャップ５００μｍのスペーサーリングで内外周に挟み同一基板をダミー板として用いたエアーサンドイッチ構造の光記録媒体を作成した。
【００７６】
以上のようにして記録層が形成された光記録媒体について、実施例１と同様に評価試験を行った。波長４０５ｎｍ、開口数０．６５の青色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速５．３ｍ／ｓにて１−７ＲＬＬの２Ｔ相当（最小ピット長＝０．２３μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にてグルーブ（溝中）へ記録を実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１２ｍＷで、２ＴＣＮＲ＝５０ｄＢ、変調度＝０．２３と極めて良好な結果が観測された。
【００７７】
引き続いて、同じ光学ピックアップを用い、１−７ＲＬＬの８Ｔ相当（ピット長＝０．９２μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１０ｍＷで、８ＴＣＮＲ＝５９ｄＢ、変調度＝０．７６と非常に良好な結果が観測された。
【００７８】
（実施例５）
フラーレンＣ６０の記録層を膜厚２５ｎｍに成膜する以外は、実施例４と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例４と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝９ｍＷの時の信号品位は、２ＴＣＮＲ＝５２ｄＢと良好なものであった。
【００７９】
引き続いて、同じ光学ピックアップを用い、実施例１と同様に１−７ＲＬＬの８Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝９ｍＷの時の信号品位は、８ＴＣＮＲ＝５９ｄＢと良好なものであった。結果を表１にまとめる。
【００８０】
（参考例３）
フラーレンＣ６０の記録層を膜厚６５ｎｍに成膜する以外は、実施例４と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例４と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、厚膜のためにピット間の熱干渉の影響が大きくでてしまい、良好なピットが形成されなかった。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１０ｍＷの時の信号品位は、２ＴＣＮＲは４０ｄＢ以下であった。これは短ピットの熱干渉により正常な測定が出来なかったためと思われる。
【００８１】
引き続いて、同じ光学ピックアップを用い、実施例１と同様に１−７ＲＬＬの８Ｔ相当の評価試験を行ったところ、厚膜のためにピット間の熱干渉の影響が大きくでてしまい、良好なピットが形成されなかった。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１０ｍＷの時の信号品位は、８ＴＣＮＲ＝４５ｄＢであった。結果を表１にまとめる。
【００８２】
（実施例６）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．７４ μｍ、溝幅：０．３３μｍ、溝深さ：１００ｎｍ）を有する外径１２０ｍｍ φ、厚さ０．６ｍｍ の円盤状の基板上に、実施例１と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例１と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、２ＴＣＮＲ＝４９ｄＢと良好なものであった。
【００８３】
引き続いて、同じ光学ピックアップを用い、実施例１と同様に１−７ＲＬＬの８Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、８ＴＣＮＲ＝５１ｄＢと良好なものであった。結果を表１にまとめる。
【００８４】
（参考例４）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．７４ μｍ、溝幅：０．３３μｍ、溝深さ：１７０ｎｍ）を有する外径１２０ｍｍ φ、厚さ０．６ｍｍ の円盤状の基板上に、実施例７と同様の方法で光記録媒体を作成した。以上のようにして作成された光記録媒体について、実施例１と同様に１−７ＲＬＬの２Ｔ相当の評価試験を行ったところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、２ＴＣＮＲ＝３９ｄＢと振幅が減少した。
【００８５】
引き続いて、同じ光学ピックアップを用い、実施例７と同様に１−７ＲＬＬの８Ｔ相当の評価試験を行ったところ、信号波形に大きな歪みが顕在化した。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷの時の信号品位は、８ＴＣＮＲ＝４６ｄＢと良好なものではなかった。結果を表１にまとめる。
【００８６】
（実施例７）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．７４μｍ、溝幅：０．３３μｍ、溝深さ：５０ｎｍ）を有する外径１２０ｍｍ φ、厚さ０．６ｍｍ の円盤状の基板上に、真空蒸着法で直接、実施例１で使用されたものと同様のフラーレンＣ６０を蒸着して、厚さ４０ｎｍ となるように記録層を成膜した。その後、該記録層上に無機ＳｉＯ_２膜を徳田製作所製スパッタ装置（ＣＦＳ−８ＥＰ）を用いて膜厚２５ｎｍで成膜して光記録媒体を作製した。その上に実施例１と同様に反射層保護層は設けた媒体構造とした。
【００８７】
以上のようにして記録層が形成された光記録媒体について、実施例１と同様に評価試験を行った。波長４０５ｎｍ、開口数０．６５の青色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速５．３ｍ／ｓにて１−７ＲＬＬの２Ｔ相当（最小ピット長＝０．２３μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にてグルーブ（溝中）へ記録を実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷで、２ＴＣＮＲ＝４５ｄＢとぎりぎりではあるが、どうにか媒体に耐えうる評価結果が観得られた。
【００８８】
引き続いて、同じ光学ピックアップを用い、１−７ＲＬＬの８Ｔ相当（ピット長＝０．９２μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１５ｍＷで、８ＴＣＮＲ＝５８ｄＢと良好な結果が観測された。信号評価結果を表１にまとめる。
【００８９】
（参考例５）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．７４μｍ、溝幅：０．３３μｍ、溝深さ：５０ｎｍ）を有する外径１２０ｍｍ φ、厚さ０．６ｍｍ の円盤状の基板上に、無機ＳｉＯ_２膜を徳田製作所製スパッタ装置（ＣＦＳ−８ＥＰ）を用いて膜厚２５ｎｍで成膜した後、真空蒸着法で、実施例１で使用されたものと同様のフラーレンＣ６０を蒸着して、厚さ４０ｎｍ となるように記録層を成膜した。その後、該記録層上に無機ＳｉＯ_２膜を徳田製作所製スパッタ装置（ＣＦＳ−８ＥＰ）を用いて膜厚２５ｎｍで成膜し、フラーレン記録膜をサンドイッチ構造で挟みこんだ。更に、その上に実施例１と同様に反射層保護層を設けた光記録媒体を作製した。
【００９０】
実施例１と同様に評価試験を行った。波長４０５ｎｍ、開口数０．６５の青色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速５．３ｍ／ｓにて１−７ＲＬＬの２Ｔ相当（最小ピット長＝０．２３μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にてグルーブ（溝中）へ記録を実施したところ、変調度が小さくなり波形も大きく歪んだ。
【００９１】
さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１２ｍＷで、２ＴＣＮＲ＝３９ｄＢ、変調度も０．１５以下と大きく特性が悪化した。
【００９２】
引き続いて、同じ光学ピックアップを用い、１−７ＲＬＬの８Ｔ相当（ピット長＝０．９２μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝１２ｍＷで、８ＴＣＮＲ＝４０ｄＢ、変調度も０．６以下と出力が不充分であった。信号評価結果を表１にまとめる。
【００９３】
（実施例８）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．３２μｍ、溝幅：０．１５μｍ、溝深さ：３５ｎｍ）を有する外径１２０ｍｍ φ、厚さ１．１ｍｍ の円盤状の基板上に、バルザス製スパッタ装置（ＣＤＩ−９００）を用いて銀をスパッタし、厚さ７０ｎｍの反射層を形成した。スパッタガスにはアルゴンガスを用いた。さらに反射層の上には、
真空蒸着法で、実施例１で使用されたものと同様のフラーレンＣ６０を蒸着して、厚さ３０ｎｍ となるように記録層を成膜した。その後、該記録層上に無機ＳｉＯ_２膜を徳田製作所製スパッタ装置（ＣＦＳ−８ＥＰ）を用いて膜厚２５ｎｍで成膜し、その上に、三井化学製エポキシ系ＵＶ硬化樹脂ＸＴ−２０００を膜厚１００μｍに制御して塗工しＵＶ硬化させた光記録媒体を作製した。
【００９４】
以上のようにして記録層が形成された光記録媒体について、波長４０５ｎｍ、開口数０．８５の青色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速５．３ｍ／ｓにて１−７ＲＬＬの２Ｔ相当（最小ピット長＝０．１７μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて、上記のＵＶ硬化樹脂側からオングルーブへの記録を実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．３ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝６ｍＷで、２ＴＣＮＲ＝４７ｄＢ、変調度＝０．２０が得られた。
【００９５】
引き続いて、同じ光学ピックアップを用い、１−７ＲＬＬの８Ｔ相当（ピット長＝０．６８μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝６ｍＷで、８ＴＣＮＲ＝５５ｄＢ、変調度＝０．７８と良好な結果が観測された。信号評価結果を表１にまとめる。
【００９６】
（実施例９）
ポリカーボネート樹脂製で連続した案内溝（トラックピッチ：０．３２μｍ、溝幅：０．１５μｍ、溝深さ：３５ｎｍ）を有する外径１２０ｍｍ φ、厚さ１．１ｍｍ の円盤状の基板上に、直接、真空蒸着法で、実施例１で使用されたものと同様のフラーレンＣ６０を蒸着して、厚さ３０ｎｍ となるように記録層を成膜した。その後、該記録層上に無機ＳｉＯ_２膜を徳田製作所製スパッタ装置（ＣＦＳ−８ＥＰ）を用いて膜厚２５ｎｍで成膜し、その上に、三井化学製エポキシ系ＵＶ硬化樹脂ＸＴ−２０００を膜厚１００μｍに制御して塗工しＵＶ硬化させた光記録媒体を作製した。
【００９７】
以上のようにして記録層が形成された光記録媒体について、波長４０５ｎｍ、開口数０．８５の青色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速５．３ｍ／ｓにて１−７ＲＬＬの２Ｔ相当（最小ピット長＝０．１７μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて、上記のＵＶ硬化樹脂側からオングルーブへの記録を実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．３ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝６ｍＷで、２ＴＣＮＲ＝４５ｄＢが得られた。
【００９８】
引き続いて、同じ光学ピックアップを用い、１−７ＲＬＬの８Ｔ相当（ピット長＝０．６８μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝６ｍＷで、８ＴＣＮＲ＝４８ｄＢと良好な結果が観測された。信号評価結果を表１にまとめる。
【００９９】
（実施例１０）
実施例１で作製した光記録媒体に対して、波長６５０ｎｍ、開口数０．６０の赤色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速３．５ｍ／ｓにてＥＦＭ＋の３Ｔ相当（最小ピット長＝０．４０μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて、上記のＵＶ硬化樹脂側からオングルーブへの記録を実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．３ｍＷ、線速３．５ｍ／ｓ）で再生した結果、記録レーザーパワー＝２４ｍＷで、２ＴＣＮＲ＝５２ｄＢが得られた。
【０１００】
引き続いて、同じ光学ピックアップを用い、１−７ＲＬＬの８Ｔ相当（ピット長＝１．８７μｍ）でのＯＮ・ＯＦＦ繰り返し信号をパルストレーン型の記録ストラテジー条件にて実施したところ、良好にピットが形成され記録できた。さらに、その記録部位を同じ光学ピック（再生パワー＝０．７ｍＷ、線速５．３ｍ／ｓ）で再生した結果、記録レーザーパワー＝２４ｍＷで、１４ＴＣＮＲ＝５８ｄＢと良好な結果が観測された。信号評価結果を表１にまとめる。
【０１０１】
（実施例１１）
実施例１０で記録した光記録媒体に対して、波長４０５ｎｍ、開口数０．６５の青色レーザーヘッドを搭載した評価機（ＰＵＬＳＴＥＣ ＤＤＵ１０００（Ｂｌｕｅ））により、線速３．５ｍ／ｓにて記録部位を再生トレースした（再生パワー＝０．７ｍＷ、線速３．５ｍ／ｓ）結果、３ＴＣＮＲ＝５５ｄＢ、１４ＴＣＮＲ＝６０ｄＢと十分に良好な結果が観測された。 信号評価結果を表１にまとめる。
【０１０２】
【発明の効果】
本発明によれば、レーザー光照射により、記録層と隣接する層または透明基板に熱変形及び／あるいは熱変性を伴った良好な記録ピットが形成されるため、信号振幅の獲得が容易であり、且つ、長期保存信頼性に優れた記録媒体の提供を可能とした。透明基板上に分解温度の極めて高い堅牢なフラーレン系骨格を主成分とした記録層を選択することにより、高密度光記録媒体として非常に注目されている波長３９０ 〜７００ｎｍのレーザーを有する光学ヘッドを用いて、記録・再生可能な光情報記録媒体を提供することが可能となる。
【０１０３】
【表１】

【図面の簡単な説明】
【 図１ 】本発明の光記録媒体の一構成例を示す模式図である。
【 図２ 】本発明の光記録媒体の他の一構成例を示す模式図である。
【 図３ 】本発明の光記録媒体の他の一構成例を示す模式図である。
【 図４ 】本発明の光記録媒体の他の一構成例を示す模式図である。
【 図５ 】本発明の光記録媒体の他の一構成例を示す模式図である。
【 図６ 】本発明の光記録媒体の他の一構成例を示す模式図である。
【 図７ 】本発明の光記録媒体の他の一構成例を示す模式図である。
【 図８ 】本発明の光記録媒体の信号のアイパターンを示す図である。
【 図９ 】記録後の基板ピットの物理変形痕を示す写真である。
【 符号の説明】
１ ：基板、 ２ ：記録層、 ３ ：反射層、 ４ ：保護層
５ ：接着層、 ６ ：透明保護層、 ７ ：スペーサー
８ ：ダミー基板、 ９ ：光透過層（シート）、 １１ ：基板
１２ ：記録層、 １３ ：反射層、 １４ ：保護層
１５ ：ダミー基板層、 １１ ’：支持基板、 １２ ’：記録層
１３ ’：反射層、 １４ ’：透明保護層、 １５ ’：光透過層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-density optical recording medium on which information can be recorded / reproduced by laser light.
[0002]
[Prior art]
2. Description of the Related Art In recent years, the progress of advanced information society has been remarkable, and a medium capable of recording a large amount of information and moving and carrying it has become indispensable in social life. At present, write-once and rewritable optical recording media such as CD-R, CD-RW, DVD-R, and DVD-RW have become widespread as such removable large-capacity optical recording media. Shaping the market. Furthermore, recently, further high-density optical recording media to which a blue-violet laser is applied have been proposed and are being introduced to the market.
[0003]
Among these, the recording material of a write-once optical recording medium that can be recorded only once is required to have a high reflectance before recording so that the degree of modulation is large as a physical property. In the vicinity, it was desired to have an absorption peak with a large extinction coefficient and a high refractive index (usually 2.0 or more). Conventionally, an organic dye has been optimized as a material satisfying such optical requirements, and has been put to practical use after various optimization studies. Furthermore, the dye-based material is suitable for mass production because of its excellent workability and simple media structure.
[0004]
Here, in addition to the need for an ever-increasing recording density, it is necessary to form good high-definition recording pits, and optical changes in a small area mainly due to a red semiconductor laser near 650 nm and a blue-violet semiconductor laser around 400 nm ( The shape control of the (reflectance change) portion has become extremely important.
[0005]
The recording layer made of an organic dye that has been conventionally proposed, when performing high-density optical recording by filling the recording pit interval, generates excessive heat during recording, and the dye layer itself is thermally denatured and / or degraded by the residual heat. In many cases, thermal deformation (generally referred to as thermal interference) often occurs, which often makes it difficult to perform good high-density pit shape control because the pit edges are dull or the front and rear pits are connected. Therefore, for the purpose of reducing such thermal interference, improvement was achieved by selecting a thermally robust dye type and / or optimizing the thickness of the dye recording layer. The sensitivity has been reduced, and there is a limit to improvement for high density. On the other hand, a technique in which a fullerene-based compound is applied to an optical recording medium has been disclosed.
[0006]
Patent Document 1 (JP-A-11-283276) discloses a fluorescent information recording medium using a fullerene-based compound. The medium disclosed in this publication is a ROM-type medium in which, after information is written by photooxidizing fullerene to change its fluorescence characteristics, a photooxidation protection substance is added to protect the information. Further, Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-49245) discloses a proposal using a polymer-dispersed fullerene film to confirm strong light emission at a laser light irradiation site and to use arbitrary patterning of the light emission site as a recording material. Has been described. All of these applications focus on the luminescence behavior of fullerene-based thin films.
[0007]
By the way, it is desired that information recorded as an archive recording medium be stored for a long time in a write-once optical recording medium.
[0008]
[Patent Document 1] JP-A-11-283276
[0009]
[Patent Document 2] JP-A-2001-49245
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide an optical recording medium having extremely high light resistance and long-term weather resistance and capable of improving the long-term storage of recorded information.
[0011]
[Means for Solving the Problems]
In the present invention, a recording layer containing at least a fullerene-based compound is formed directly on a layer transparent to a recording / reproducing wavelength or via another layer, and the recording layer generates heat by laser light irradiation. An optical recording medium capable of forming recording pits in the transparent layer or another layer adjacent to the transparent layer.
[0012]
In the present invention, the recording layer preferably has a thickness of 60 nm or less.
In the present invention, it is preferable that the recording pit is formed by thermal deformation or thermal denaturation.
Further, the fullerene compound of the recording layer preferably contains at least C60 fullerene. It is preferable that recording and / or reproduction be possible in a laser wavelength range of 390 nm to 700 nm.
Here, the layer transparent to the recording / reproducing wavelength may be any layer that can transmit light to the extent that signal quality is not impaired in normal recording / reproducing. Further, it is a transparent layer to the extent that it absorbs light and does not form recording pits due to its own heat generation.
[0013]
The present inventors have found from the interface SEM observation and the like that the fullerene film extremely efficiently converts the light energy irradiated during the recording process into heat and greatly deforms the adjacent layer. Further, it was confirmed by TOF-SIMS analysis and the like that specific fullerene oxide was detected from the fullerene recording site. As a result, it was also revealed that the recording process of the flouren film was going through a large exothermic process accompanied by an oxidation reaction.
[0014]
Therefore, it has been found that by utilizing this, a recording pit can be formed in an adjacent layer adjacent to the recording layer by using fullerene as the recording layer of the high-density optical recording medium.
[0015]
The layer transparent to the recording / reproducing wavelength may be a support substrate on which a recording layer or the like is formed.
[0016]
When a fullerene film is formed directly on a transparent substrate of polycarbonate or the like, recording pits can be formed on the polycarbonate substrate adjacent to the fullerene film due to heat generation when the recording laser beam is irradiated to the fullerene film. In this case, the layer transparent to the recording / reproducing wavelength corresponds to a polycarbonate substrate which is a supporting substrate.
[0017]
Conventional write-once optical recording media generally use a dye for the recording layer, but the dye is inferior in light resistance to polycarbonate and the like due to its properties. Therefore, the life of an optical recording medium using a dye is finite even though it is practically long. In the optical recording medium of the present invention, fullerene is used for the recording layer, and recording pits are also formed on the transparent layer (including the substrate) having high light resistance, so that the light resistance and weather resistance are dramatically improved.
[0018]
Further, it has been found that in order to form recording pits and obtain good recording characteristics, it is preferable that the thickness of the recording layer containing fullerene is considerably thinner. According to this, the thickness is desirably 60 nm or less. The lower limit is determined in order to maintain the recording characteristics, and cannot be unconditionally determined from the recording conditions and the like. However, 5 nm is preferable because it becomes at least a continuous film. More preferably, it is 10 nm. More preferably, it is 20 nm.
[0019]
Next, it was confirmed that the C60 fullerene thin film has a very good optical characteristic with a refractive index of 2 or more over a wide range of wavelengths from 350 nm to 700 nm, and in this wavelength region, uniformly excellent optical recording is possible. I found something. None of the conventional organic dye films can maintain a high refractive index over such a wide wavelength range.
[0020]
Furthermore, the present inventors have pursued the reason why excellent optical recording characteristics can be obtained by using the fullerene according to the present invention as a recording material, and have obtained the following knowledge.
[0021]
TGA thermal loss analysis revealed that under air / nitrogen atmosphere, no thermal loss due to melting, thermal decomposition, etc. was observed up to a high temperature of 500 ° C or higher. Proof that there was no occurrence. From the viscoelastic analysis of C60 bulk under elevated temperature, it was confirmed that there was no change in the viscosity of the film at least at 300 ° C or lower. It was also proved that dulling of the pit edge due to film melting is unlikely to occur. These have good thermophysical properties not found in the conventionally used organic dye materials for recording, indicating that the C60 fullerene-based compound is extremely promising as a high-density recording material in terms of thermal design.
[0022]
It has been found that it has higher light-to-heat conversion efficiency and can maintain good recording sensitivity. In addition, it was also found that the threshold value of the heat change was steep, and that it also had high heat resistance so as not to undergo heat changes such as melting and vaporization up to a high temperature range.
[0023]
It was confirmed that the recording layer using the fullerene-based compound generated a considerable amount of heat due to the very efficient light-to-heat conversion of the fullerene, and further proceeded with the oxidation reaction of the fullerene skeleton. Although the details of such high-efficiency light-to-heat conversion are currently being elucidated, the present inventors believe that the photoexcitation state inherent to the fullerene molecule, that is, the thermal relaxation process from the high excitation state, results. ing. In any case, this very efficient light-to-heat conversion is far superior to that of conventional recording dye materials, and the optical recording behavior based on this principle is equivalent to that of light emission conventionally disclosed in fullerene systems. This is clearly different from the recording mode used.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Here, an optical recording medium of the present invention having a recording layer and a reflective layer on a substrate will be described as a suitable example. In the following description, an optical disc is used as an optical recording medium, which has, for example, a guide groove on a support substrate, a reflective layer and a recording layer mainly composed of an organic dye on the guide groove, and has a wavelength of 390 nm to 700 nm. A medium for recording and reproducing a signal by irradiating a condensed laser beam will be described. However, the optical recording medium of the present invention is not limited to such a shape and configuration, and may be a card, a sheet, or a drum. And other various shapes, those having no reflective layer, and those applicable to recording / reproducing with a shorter wavelength laser which will be developed in the future.
[0025]
The optical recording medium of the present invention has, for example, a four-layer structure in which a substrate 1, a recording layer 2, a reflective layer 3, and a protective layer 4 are sequentially laminated as shown in FIG. , A three-layer structure in which the substrate 1, the recording layer 2, and the protective layer 3 are sequentially laminated, or a recording layer open type structure as shown in FIG. That is, an air-sandwich structure in which only the substrate 1 and the recording layer 2 are sequentially laminated and the dummy substrate 8 is laminated via the spacer 7 or a laminated structure as shown in FIG. That is, a recording layer 2 is formed on a substrate 1, a reflective layer 3 is provided in close contact with the recording layer 2, and a dummy substrate 8 is further bonded thereon via an adhesive layer 5. Any structure may be taken. Each of these may have another layer below or above the recording layer 2 or another layer above the reflective layer 3. Further, as shown in FIG. 5, a structure in which the substrate 1, the reflective layer 3, the recording layer 2, the transparent protective layer 6, and the light transmitting layer (or sheet) 9 are laminated in this order, and recording / reproducing is performed from the transparent protective layer side. good. Here, the transparent protective layer 6 may also serve as the light transmitting layer (or sheet) 9. Further, as described in JP-A-10-326435, the thickness of the light transmitting layer is determined by the N.V. A. And a medium structure defined by the laser wavelength λ. Further, the optical information recording medium of the present invention may have a structure having two or more types of recording layers as described in JP-A-11-203729 as needed.
[0026]
As an example in which the present invention is applied to an optical disc, as shown in FIG. 6, a substrate 11 having a guide groove, a recording layer 12, a reflective layer 13, and a protective layer 14 are laminated in this order, and a protective layer also serving as an adhesive layer. 14 on which a dummy substrate 15 is bonded. Needless to say, a configuration without the substrate 15 may be employed, such as between the substrate 11 and the recording layer 12, between the recording layer 12 and the reflective layer 13, between the reflective layer 13 and the protective layer 14, between the protective layer 14 and the dummy substrate 15. Other layers may be present between. In the optical disk of FIG. 6, recording and reproduction are performed from the substrate 11 side.
[0027]
As another embodiment, a structure disclosed in Japanese Patent Application Laid-Open No. 10-302310, for example, as shown in FIG. 7, a reflective layer 13 ′ and an organic dye are formed on a support substrate 11 ′ having a guide groove formed thereon. A recording layer 12 ′ as a main component is formed in this order, and a light transmitting layer 15 ′ is formed on the recording layer 12 ′ via a transparent protective layer 14 ′ arbitrarily formed, thereby recording and reproducing information. Is performed from the light transmission layer 15 ′ side. Conversely, a guide groove may be formed on the side of the light transmitting layer 15 ′, and the transparent protective layer 14 ′, the recording layer 12 ′, and the reflective layer 13 ′ may be laminated thereon and bonded to the support substrate 11 ′. .
[0028]
Usually, when used as an optical disk, the support substrate is preferably a disk having a thickness of about 1.2 mm and a diameter of about 80 to 120 mm, and a hole having a diameter of about 15 mm is preferably formed in the center.
[0029]
In the present invention, a recording layer is provided on a substrate. The recording layer of the present invention contains at least one fullerene having no substituent or a compound having a substituent represented by the general formula (1). It is. Good recording / reproduction is possible with respect to the recording laser wavelength and the reproduction laser wavelength selected from the wavelengths of 390 nm to 700 nm. That is, a good C / N ratio can be obtained with respect to a recording laser wavelength and a reproduction laser wavelength selected from the wavelength range of 390 nm to 700 nm, and reproduction light stability is good and high quality signal characteristics can be obtained. Optical information recording medium.
[0030]
The fullerene having no substituent or the compound represented by the chemical formula 1 according to the present invention can select an absorption wavelength arbitrarily in a state of maintaining an absorption coefficient by selecting a substituent. At the wavelength, the optical constant required for the recording layer can be satisfied.
[0031]
[Formula 1]

[0032]
[In the formula, R 1 and R 2 each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group which may have a substituent, an aralkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, An aralkyloxy group, an aryloxy group, an alkenyloxy group, an acyl group, an amino group, an aminocarbonyl group, a silyl group, a phosphino group, or a heterocyclic group, and R 1 and R 2 are each independently a ring via a linking group; May be formed, and one or more of R 1, R 2 and the fullerene skeleton may be a metal complex. n represents an integer of 1 to 3. Further, a metallocenyl group may be used as a substituent of R1 and R2 as a thermal decomposition accelerator. ]
The fullerene compound represented by the general formula (1) used in the present invention is not limited. 43 (1999) and the like.
[0033]
The fullerene compound of the present invention also includes multimeric fullerene compounds. Specifically, two or more fullerene-based compounds of the formula (1) may be bonded via at least one or more types of linking groups, or may be directly single-bonded and linked. Examples of the linking group include an optionally substituted methylene group, an optionally substituted methine group, an optionally substituted ethynylene group, an optionally substituted phenylene group, an amino group, an imino group, an oxygen atom or a sulfur atom. And the like. The fullerene-based compound represented by the formula (1) may be linked via 1 to 4 linking groups represented by these linking groups. The content of these higher fullerenes is not particularly limited.
[0034]
The fullerene dye to be used is not particularly limited, such as C60, C70, C82, and C120, but a C60 fullerene compound that can be synthesized in large quantities is most preferable.
[0035]
As a method for identifying a fullerene compound used in the recording layer, a method such as UV spectrum, FD-MS, NMR, TOF-SIMS, SNOM, Raman spectroscopy, and FT-IR is used after isolating the recording film. However, if fullerene is a simple substance, it can be dissolved in benzene and toluene in a trace amount, so that identification by liquid chromatography after TLC fractionation is effective as a simple and reliable method.
[0036]
The recording layer constituting the optical recording medium of the present invention is substantially composed of one or more fullerene compounds, particularly C60 alone or a compound of the formula (1). It may be mixed with a compound having an absorption maximum at a wavelength of 290 nm to 690 nm and a large refractive index at 300 nm to 700 nm. Specifically, cyanine compounds, squarylium compounds, naphthoquinone compounds, anthraquinone compounds, tetrapyraporphyrazine compounds, indophenol compounds, pyrylium compounds, thiopyrylium compounds, azurenium compounds, triphenylmethane compounds , Xanthene compounds, indathrene compounds, indigo compounds, thioindigo compounds, merocyanine compounds, thiazine compounds, acridine compounds, oxazine compounds, dipyrromethene compounds, oxazole compounds, azaporphyrin compounds, porphyrin compounds, porphycene compounds And a mixture of a plurality of compounds. The mixing ratio of these compounds is 0. It is about 1% to 30% by mass.
[0037]
The content of the fullerene alone or the fullerene-based compound represented by the general formula (1) used in the recording layer can be selected to be any amount capable of recording / reproducing, but is usually 30% or more, and preferably 30% or more. 60% or more. In addition, it is also preferable that it is substantially 100%.
[0038]
Methods for providing a recording layer include, for example, spin coating, spraying, casting, sliding, curtain, extrusion, wire, gravure, spread, roller coating, knife coating, dipping, etc. Method, a sputtering method, an EB evaporation method, a chemical evaporation method, a vacuum evaporation method, and the like.
[0039]
Generally, in the case of a fullerene compound such as C60, it is often very difficult to dissolve itself in a solvent, and therefore, a sputtering method, an EB vapor deposition method, a chemical vapor deposition method, a vacuum vapor deposition method, or the like is rather suitable. Also, when a solvent that does not damage the substrate cannot be selected, a sputtering method, an EB evaporation method, a chemical evaporation method, a vacuum evaporation method, or the like has been effective.
[0040]
Here, for forming a C60 fullerene thin film, a vapor deposition method is particularly preferable, and a uniform deposition rate is achieved in the range of 0.01 nm to 0.1 nm / sec by precise control of the heating current of a Mo or W boat. Film formation was achieved.
[0041]
When the recording layer is formed on the substrate, the material of the substrate to be used adjacent to the recording layer is basically the recording light and the laser light, taking into consideration that the laser irradiation is performed through the substrate 11 as shown in FIG. It is desirable that the material be transparent at the wavelength of the reproduction light, have mechanical strength as a supporting substrate, have a melting point and decomposition point of 300 ° C. or more, and have a glass transition temperature of 100 ° C. or more. Therefore, as a specific material, for example, a polymer material such as an acrylic resin, a polyethylene resin, a polycarbonate resin, a polyolefin resin, and an epoxy resin is used.
On the other hand, when laser irradiation is performed from the side of the light transmission layer 15 ′ opposite to the substrate 11 ′, as in the configuration shown in FIG. You can choose from materials. From the viewpoint of the mechanical properties required for the substrate and the productivity of the substrate, a material that can be injection-molded or cast-molded, such as an acrylic resin, a polycarbonate resin, or a polyolefin resin, is preferable. These substrate materials may be formed into substrates in a disk shape by an injection molding method or the like.
[0042]
Usually, guide grooves and / or prepits on the order of submicron are formed in a spiral or concentric circle on the surface layer of these substrates. These guide grooves and prepits are preferably provided at the time of substrate formation, and can be provided by injection molding using a stamper master or thermal transfer method using a photopolymer. Incidentally, guide grooves and / or pre-pits may be formed in the light transmitting layer 15 'in FIG. 7, and the same method can be applied when the guide grooves and / or pre-pits are provided. In the case of HD-DVDR which performs higher-density recording than DVD, the pitch and depth of the guide groove are in the range of 0.25 to 0.80 μm as the pitch and 20 to 150 nm as the depth, and more preferably in the range of 30 to 100 nm. It is preferred to select from a range. For the purpose of controlling the amount of deformation during recording, a layer made of an inorganic substance or a polymer may be provided on the substrate. According to the present inventors' detailed studies, it is preferable that the adjacent layer has an appropriate thermal hardness and viscoelasticity, and forms an adjacent interface (layer) capable of buffering deformation.
[0043]
However, good high-density recording can also be achieved by forming a fullerene compound directly on a polycarbonate substrate having an appropriate groove shape with the above-mentioned appropriate film thickness setting, and forming deformation traces during recording directly on the substrate surface layer. I was able to confirm enough.
[0044]
The layer adjacent to the recording layer containing the fullerene compound is preferably an organic film. This is because recording pits are easily formed. Further, it is more preferable that an organic dye film or a polymer having a clear temperature threshold and thermally denatured is laminated and used adjacent to the recording layer containing the fullerene compound. If formed between the recording layer and the substrate on the recording light incident side, heat generated from the fullerene compound is thermally transferred to the dye / polymer layer, and recording by modifying the dye / polymer becomes possible. Depending on the design of the optical constants of the dyes used, high-density signals can be obtained with good signal amplitude. Further, the polymer layer may be transparent. This itself forms recording pits by heat from the recording layer containing fullerene, thereby enhancing long-term storage.
[0045]
Specific examples of applicable dye species include cyanine compounds, squarylium compounds, naphthoquinone compounds, anthraquinone compounds, tetrapyraporphyrazine compounds, indophenol compounds, pyrylium compounds, thiopyrylium compounds, and azurenium compounds. , Triphenylmethane compounds, xanthene compounds, indazulene compounds, indigo compounds, thioindigo compounds, merocyanine compounds, thiazine compounds, acridine compounds, oxazine compounds, dipyrromethene compounds, oxazole compounds, azaporphyrin compounds , Porphyrin-based, porphycene-based, and the like, and a mixture of a plurality of compounds may be used.
[0046]
These dye species were spin-coated from a solution system in which the solvent polarity was changed so as not to be compatible with the fullerene-based thin film, or were laminated by a vacuum system film-forming method. The laminated film thickness was optimized in consideration of the optical design (reflectance and modulation) according to the recording wavelength.
[0047]
As for the quantitative measurement of the dye thickness of the recording layer, a highly accurate method has recently begun to be used in which an end face is etched with a gallium ion beam or the like and then observed with a SEM or a TEM. (FIB-SEM, FIB-TEM) One of the merits of this method is that the hardness is extremely low as compared with the conventional method of measuring a dye film thickness by taking out a slice of an object due to freezing breakage or the like. It is possible to measure the dye film thickness by reflecting an accurate layer structure up to those that could not be measured.
[0048]
To determine whether or not the recording layer was recorded with the thermal mode physical deformation of the film by irradiating the laser beam, after carefully peeling off the interface of the recording layer, the pit formation part was observed with SEM, TEM, or AFM. It is common to do. In particular, in order to observe the physical deformation traces of the substrate, it is necessary to immerse the recording layer in an organic solvent such as heptane or dimethylcyclohexane for about 1 hour after the recording layer is peeled off, to roughly remove the recording layer, and then perform SEM observation or AFM observation. It is valid. Further, for detection of oxide from the recording layer after recording, it is effective to analyze an extremely small area such as TOF-SIMS, SNOM, and micro Raman of a pit formation minute part.
[0049]
Next, a reflective layer may be formed adjacent to the recording layer. When the reflective layer is formed, the thickness is usually preferably 10 nm to 200 nm. A reflection amplification layer, an adhesive layer, and a deformation buffer layer can be provided between the recording layer and the reflection layer in order to increase the reflectance, improve the adhesion, and improve the signal quality. As a material of the reflection layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal of Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Rh and Pd alone or as an alloy It can be used. Among them, Au, Ag, Pt, Cu, Al, Ni and Rh have high reflectivity and are suitable as the material of the reflection layer. When performing recording / reproduction with a blue laser, Al or Ag is preferable. In addition, the following may be included. For example, metals such as Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, and Bi And metalloids. Further, those containing Ag or Al 2 as a main component are preferable because a reflection layer having a high reflectance can be easily obtained. It is also possible to form a multilayer film by alternately stacking low-refractive-index thin films and high-refractive-index thin films with a material other than a metal and use it as a reflective layer.
[0050]
Examples of the method for forming the reflective layer include a sputtering method, an ion plating method, a chemical vapor deposition method, and a vacuum vapor deposition method. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or below the reflective layer to improve the reflectance, the recording characteristics, and the adhesion.
[0051]
Further, the recording layer and the reflective layer are usually protected by a protective layer. The material of the protective layer is not particularly limited as long as it protects the reflective layer from external force. As the inorganic substance, SiO ₂ , S ₃ N ₄ , MgF ₂ , AlN, SnO ₂ And the like. Examples of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in a suitable solvent to prepare a coating solution, and then applying and drying this coating solution. The ultraviolet-curable resin can be formed by applying the coating liquid as it is or after dissolving it in an appropriate solvent to prepare a coating liquid, and then irradiating ultraviolet rays to cure the resin. As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or as a mixture, and may be used not only as a single layer but also as a multilayer film.
[0052]
As a method of forming the protective layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used as in the case of the recording layer. Among them, the spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 μm to 100 μm, but in the present invention, it is 3 μm to 30 μm, and more preferably 5 μm to 20 μm.
[0053]
Labels, bar codes, and the like can be further printed on the protective layer.
Alternatively, a protective sheet or a substrate may be bonded to the reflective layer surface, or two optical recording media may be bonded to each other with the reflective layer surfaces facing each other. On the mirror side of the substrate, an ultraviolet curable resin, an inorganic thin film, or the like may be formed to protect the surface or prevent adhesion of dust and the like.
[0054]
Here, the laser having a wavelength of 390 nm to 700 nm referred to in the present invention is not particularly limited. For example, a dye laser capable of wavelength selection in a wide range of the visible light region, a GaN-based laser having a wavelength of 400 to 410 nm, or Cr-doped LiSnAlF ₆ And a semiconductor laser such as a visible semiconductor laser having a wavelength of 405 nm, 415 nm, or 425 nm, in addition to a laser that emits a second harmonic of 430 nm of an infrared laser having a wavelength of 860 nm. In the present invention, the above-described semiconductor laser or the like can be appropriately selected according to the sensitive wavelength of the recording layer for recording or reproducing. High-density recording and reproduction are each possible at one or more wavelengths selected from the semiconductor lasers described above.
[0055]
As described above, an optical recording medium in which a recording layer contains fullerene and can form recording pits in an adjacent layer or a transparent layer due to heat generation during recording has a higher long-term preservability of recorded information than conventional ones due to high light resistance. Become. Next, some examples of media designs for improving the recording characteristics will be described below.
[0056]
(Example 1)
A vacuum is placed on a disc-shaped substrate having an outer diameter of 120 mm φ and a thickness of 0.6 mm having continuous guide grooves made of polycarbonate resin (track pitch: 0.74 μm, groove width: 0.33 μm, groove depth: 50 nm). Fullerene C60 (manufactured by Tokyo Chemical Industry Co., Ltd.> 99.9%) represented by the following (Formula 2) was deposited by a vapor deposition method, and a recording layer was formed to have a thickness of 40 nm.
[0057]
[Formula 2]

[0058]
Silver was sputtered on the recording layer using a sputtering apparatus (CDI-900) manufactured by Balzers Co., Ltd. to form a reflective layer having a thickness of 150 nm. Argon gas was used as a sputtering gas. Sputtering conditions were as follows: sputter power 2. 5 kW, sputtering gas pressure 1.33 Pa (1.0 × 10 ^-2 Torr).
[0059]
Further, a UV-curable resin SD-17 (manufactured by Dainippon Ink and Chemicals, Inc.) was spin-coated on the reflective layer, and then UV-irradiated to form a protective layer having a thickness of 5 μm. Furthermore, after spin-coating UV-curable resin Desolite KZ-8681 (manufactured by JSR) on the protective layer, a polycarbonate resin substrate having no guide groove similar to the above-mentioned substrate is placed, and the substrate is irradiated with ultraviolet rays to bond the substrates, and optical recording is performed. A medium was prepared.
[0060]
An evaluation test was performed on the optical recording medium having the recording layer formed as described above as follows. Evaluator equipped with a blue laser head having a wavelength of 405 nm and a numerical aperture of 0.65 (PULSTEC DDU1000 (Blue)), at a linear velocity of 5.3 m / s, equivalent to 1T RLL 2T (minimum pit length = 0.23 μm) When the ON / OFF repetition signal was recorded in the groove (in the groove) under the pulse train type recording strategy condition, pits were formed well and recording was possible. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the recording laser power = 14 mW, 2TCNR = 56 dB, modulation degree = 0.28, which is very good. Results were observed.
[0061]
Subsequently, using the same optical pickup, an ON / OFF repetition signal of 1-7 RLL equivalent to 8T (pit length = 0.92 μm) was carried out under a pulse train type recording strategy condition, and pits were formed well. I was able to record. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the recording laser power = 14 mW, 8TCNR = 60 dB, modulation degree = 0.81. The result was observed.
[0062]
A 1-7 RLL random signal was performed on the medium by optimizing the recording strategy, and a very good jitter of 6.6% was measured. FIG. 8 shows an eye pattern obtained at this time.
[0063]
On the other hand, as a result of performing thermogravimetric analysis (TGA) of fullerene C60 alone in a nitrogen atmosphere, the thermal decomposition temperature of the recording layer compound at a weight loss of 20 wt% was 600 ° C. or more, and was extremely thermally stable. It was confirmed to be a robust compound.
[0064]
Further, the optical recording medium was peeled off at the recording interface, and the interface was observed by SEM. As a result, it was confirmed that physical deformation occurred at the recording pit portion and physical pits were formed.
FIG. 9 shows traces of recording pits formed on the polycarbonate substrate at that time.
[0065]
In addition, the optical recording medium was peeled off at the recording interface, and TOF-SIMS analysis of the interface recording pit portion confirmed a peak attributed to the oxide of C60. Table 1 summarizes the signal evaluation results.
[0066]
(Example 2)
An optical recording medium was prepared in the same manner as in Example 1, except that the recording layer of fullerene C60 was formed to a thickness of 25 nm. The optical recording medium prepared as described above was subjected to an evaluation test corresponding to 2T of 1-7 RLL in the same manner as in Example 1. As a result, pits were formed and recorded successfully. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 14 mW is as good as 2TCNR = 54 dB. there were.
[0067]
Subsequently, the same optical pickup was used to perform an evaluation test corresponding to 1-7RLL of 8T in the same manner as in Example 1. As a result, pits were successfully formed and recording was successfully performed. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 14 mW is as good as 8TCNR = 55 dB. there were. The results are summarized in Table 1.
[0068]
A 1-7 RLL random signal was applied to the medium by optimizing the recording strategy, and a very good jitter of 7.4% was measured.
[0069]
(Example 3)
An optical recording medium was prepared in the same manner as in Example 1 except that the fullerene C60 recording layer was formed to a thickness of 60 nm. The optical recording medium prepared as described above was subjected to an evaluation test corresponding to 2T of 1-7 RLL in the same manner as in Example 1. As a result, pits were formed and recorded successfully. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 15 mW is as good as 2TCNR = 47 dB. there were.
[0070]
Subsequently, the same optical pickup was used to perform an evaluation test corresponding to 1-7RLL of 8T in the same manner as in Example 1. As a result, pits were successfully formed and recording was successfully performed. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 15 mW is as good as 8TCNR = 60 dB. there were. The results are summarized in Table 1.
[0071]
A 1-7 RLL random signal was performed on the medium by optimizing the recording strategy, and a good jitter of 8.3% was measured.
[0072]
(Reference Example 1)
An optical recording medium was prepared in the same manner as in Example 1, except that the recording layer of fullerene C60 was formed to a thickness of 15 nm. The optical recording medium prepared as described above was subjected to an evaluation test equivalent to 2T of 1-7RLL in the same manner as in Example 1. As a result, noise was present on the signal in an unrecorded state. No good signal could be confirmed. This is probably because if the thickness was reduced to 15 nm, a uniform continuous film could not be formed.
The results are summarized in Table 1.
[0073]
(Reference Example 2)
An optical recording medium was prepared in the same manner as in Example 1, except that the recording layer of fullerene C60 was formed to a thickness of 65 nm. When an evaluation test corresponding to 2T of 1-7RLL was performed on the optical recording medium prepared as described above in the same manner as in Example 1, the effect of thermal interference between pits was large, and good pits were not formed. . Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 15 mW is 2TCNR = 38 dB, and the short pit Of the pit due to thermal interference of the pit was confirmed. The 2T modulation was also 0.15 or less.
[0074]
Subsequently, using the same optical pickup, an evaluation test equivalent to 8T of 1-7RLL was performed in the same manner as in Example 1. As a result, unlike the short pit behavior, pits were formed well. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), when the recording laser power = 15 mW, the signal quality is 8TCNR = 60 dB, modulation degree = 0. Was .85. The results are summarized in Table 1.
[0075]
(Example 4)
Vacuum evaporation on a disc-shaped substrate with an outer diameter of 120 mm φ and a thickness of 0.6 mm having continuous guide grooves made of polycarbonate resin (track pitch: 0.74 μm, groove width: 0.33 μm, groove depth: 50 nm) By law Directly A fullerene C60 similar to that used in Example 1 was deposited to form a recording layer having a thickness of 40 nm. An optical recording medium of an air sandwich structure using an air-open system without providing a reflective layer, a protective layer, etc. on the recording layer, and using the same substrate as a dummy plate sandwiched between inner and outer circumferences by a spacer ring having an air gap of 500 μm. Created.
[0076]
An evaluation test was performed on the optical recording medium on which the recording layer was formed as described above in the same manner as in Example 1. Evaluator equipped with a blue laser head having a wavelength of 405 nm and a numerical aperture of 0.65 (PULSTEC DDU1000 (Blue)), at a linear velocity of 5.3 m / s, equivalent to 1T RLL 2T (minimum pit length = 0.23 μm) When the ON / OFF repetition signal was recorded in the groove (in the groove) under the pulse train type recording strategy condition, pits were formed well and recording was possible. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the recording laser power = 12 mW, 2TCNR = 50 dB, modulation degree = 0.23, which is extremely good. Results were observed.
[0077]
Subsequently, using the same optical pickup, an ON / OFF repetition signal of 1-7 RLL equivalent to 8T (pit length = 0.92 μm) was carried out under a pulse train type recording strategy condition, and pits were formed well. I was able to record. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the recording laser power = 10 mW, 8TCNR = 59 dB, and the modulation factor = 0.76. Good results were observed.
[0078]
(Example 5)
An optical recording medium was prepared in the same manner as in Example 4, except that the recording layer of fullerene C60 was formed to a thickness of 25 nm. The optical recording medium prepared as described above was subjected to an evaluation test equivalent to 2T of 1-7 RLL in the same manner as in Example 4. As a result, pits were formed and recorded successfully. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 9 mW is as good as 2TCNR = 52 dB. there were.
[0079]
Subsequently, the same optical pickup was used to perform an evaluation test corresponding to 1-7RLL of 8T in the same manner as in Example 1. As a result, pits were successfully formed and recording was successfully performed. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 9 mW was as good as 8TCNR = 59 dB. there were. The results are summarized in Table 1.
[0080]
(Reference Example 3)
An optical recording medium was prepared in the same manner as in Example 4, except that the recording layer of fullerene C60 was formed to a thickness of 65 nm. When an evaluation test corresponding to 2T of 1-7RLL was performed on the optical recording medium prepared as described above in the same manner as in Example 4, the effect of thermal interference between pits became large due to the thick film. No good pits were formed. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 10 mW was 2 dB less than 40 dB. This is probably because normal measurement could not be performed due to thermal interference of short pits.
[0081]
Subsequently, using the same optical pickup, an evaluation test equivalent to 8T of 1-7RLL was performed in the same manner as in Example 1. As a result, the influence of thermal interference between the pits was large due to the thick film. Was not formed. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 10 mW was 8TCNR = 45 dB. The results are summarized in Table 1.
[0082]
(Example 6)
On a disk-shaped substrate having an outer diameter of 120 mm φ and a thickness of 0.6 mm having continuous guide grooves made of polycarbonate resin (track pitch: 0.74 μm, groove width: 0.33 μm, groove depth: 100 nm), An optical recording medium was prepared in the same manner as in Example 1. The optical recording medium prepared as described above was subjected to an evaluation test corresponding to 2T of 1-7 RLL in the same manner as in Example 1. As a result, pits were formed and recorded successfully. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 15 mW is as good as 2TCNR = 49 dB. there were.
[0083]
Subsequently, the same optical pickup was used to perform an evaluation test corresponding to 1-7RLL of 8T in the same manner as in Example 1. As a result, pits were successfully formed and recording was successfully performed. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 15 mW is as good as 8TCNR = 51 dB. there were. The results are summarized in Table 1.
[0084]
(Reference Example 4)
On a disk-shaped substrate having an outer diameter of 120 mm φ and a thickness of 0.6 mm having continuous guide grooves (track pitch: 0.74 μm, groove width: 0.33 μm, groove depth: 170 nm) made of polycarbonate resin, An optical recording medium was prepared in the same manner as in Example 7. The optical recording medium prepared as described above was subjected to an evaluation test corresponding to 2T of 1-7 RLL in the same manner as in Example 1. As a result, pits were formed and recorded successfully. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 15 mW was reduced to 2TCNR = 39 dB in amplitude. .
[0085]
Subsequently, when the same optical pickup was used and an evaluation test equivalent to 1T-7LLL of 8T was performed in the same manner as in Example 7, large distortion was apparent in the signal waveform. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the signal quality when the recording laser power = 15 mW is as good as 8TCNR = 46 dB. Did not. The results are summarized in Table 1.
[0086]
(Example 7)
A vacuum is placed on a disc-shaped substrate having an outer diameter of 120 mm φ and a thickness of 0.6 mm having continuous guide grooves made of polycarbonate resin (track pitch: 0.74 μm, groove width: 0.33 μm, groove depth: 50 nm). By evaporation method Directly A fullerene C60 similar to that used in Example 1 was deposited to form a recording layer having a thickness of 40 nm. Thereafter, an inorganic SiO 2 is formed on the recording layer. ₂ The film was formed to a thickness of 25 nm using a sputtering device (CFS-8EP) manufactured by Tokuda Seisakusho to produce an optical recording medium. A medium structure in which a reflective layer protective layer was provided thereon in the same manner as in Example 1.
[0087]
An evaluation test was performed on the optical recording medium on which the recording layer was formed as described above in the same manner as in Example 1. Evaluator equipped with a blue laser head having a wavelength of 405 nm and a numerical aperture of 0.65 (PULSTEC DDU1000 (Blue)), at a linear velocity of 5.3 m / s, equivalent to 1T RLL 2T (minimum pit length = 0.23 μm) When the ON / OFF repetition signal was recorded in the groove (in the groove) under the pulse train type recording strategy condition, pits were formed well and recording was possible. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the recording laser power = 15 mW, but 2TCNR = 45 dB, but the medium was somehow endured. A good evaluation result was obtained.
[0088]
Subsequently, using the same optical pickup, an ON / OFF repetition signal of 1-7 RLL equivalent to 8T (pit length = 0.92 μm) was carried out under a pulse train type recording strategy condition, and pits were formed well. I was able to record. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), a good result of 8 TCNR = 58 dB was observed at a recording laser power = 15 mW. Table 1 summarizes the signal evaluation results.
[0089]
(Reference Example 5)
On a disc-shaped substrate having an outer diameter of 120 mm φ and a thickness of 0.6 mm having continuous guide grooves made of polycarbonate resin (track pitch: 0.74 μm, groove width: 0.33 μm, groove depth: 50 nm), inorganic SiO ₂ After forming a film with a film thickness of 25 nm using a sputtering device (CFS-8EP) manufactured by Tokuda Seisakusho, fullerene C60 similar to that used in Example 1 was deposited by a vacuum deposition method to a thickness of 40 nm. The recording layer was formed such that Thereafter, an inorganic SiO 2 is formed on the recording layer. ₂ The film was formed with a film thickness of 25 nm using a sputtering device (CFS-8EP) manufactured by Tokuda Seisakusho, and the fullerene recording film was sandwiched by a sandwich structure. Further, an optical recording medium having a reflective layer protective layer provided thereon in the same manner as in Example 1 was produced.
[0090]
An evaluation test was performed in the same manner as in Example 1. Evaluator equipped with a blue laser head having a wavelength of 405 nm and a numerical aperture of 0.65 (PULSTEC DDU1000 (Blue)), at a linear velocity of 5.3 m / s, equivalent to 1T RLL 2T (minimum pit length = 0.23 μm) When the ON / OFF repetition signal in the above was recorded on the groove (in the groove) under the pulse train type recording strategy condition, the modulation degree became small and the waveform was greatly distorted.
[0091]
Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the recording laser power = 12 mW, 2TCNR = 39 dB, and the modulation factor were as large as 0.15 or less. Characteristics deteriorated.
[0092]
Subsequently, using the same optical pickup, an ON / OFF repetition signal of 1-7 RLL equivalent to 8T (pit length = 0.92 μm) was carried out under a pulse train type recording strategy condition, and pits were formed well. I was able to record. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the output was 8 TCNR = 40 dB and the modulation degree was 0.6 or less at the recording laser power = 12 mW. Was insufficient. Table 1 summarizes the signal evaluation results.
[0093]
(Example 8)
Balzas is formed on a disc-shaped substrate having an outer diameter of 120 mm and a thickness of 1.1 mm having continuous guide grooves (track pitch: 0.32 μm, groove width: 0.15 μm, groove depth: 35 nm) made of polycarbonate resin. Silver was sputtered using a sputtering apparatus (CDI-900) to form a reflective layer having a thickness of 70 nm. Argon gas was used as a sputtering gas. Furthermore, on the reflective layer,
Fullerene C60 similar to that used in Example 1 was deposited by a vacuum deposition method to form a recording layer having a thickness of 30 nm. Thereafter, an inorganic SiO 2 is formed on the recording layer. ₂ The film was formed into a film having a thickness of 25 nm using a sputtering device (CFS-8EP) manufactured by Tokuda Seisakusho Co. A cured optical recording medium was produced.
[0094]
With respect to the optical recording medium having the recording layer formed as described above, a linear velocity of 5.3 m / s was obtained by an evaluator (PULSECTEC DDU1000 (Blue)) equipped with a blue laser head having a wavelength of 405 nm and a numerical aperture of 0.85. The ON / OFF repetition signal at 2T equivalent to 1-7 RLL (minimum pit length = 0.17 μm) was recorded from the UV curable resin side to the on-groove under the pulse train type recording strategy condition. Pits were formed well and recording was possible. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.3 mW, linear velocity 5.3 m / s), 2TCNR = 47 dB and modulation factor = 0.20 were obtained at the recording laser power = 6 mW. Was.
[0095]
Subsequently, using the same optical pickup, an ON / OFF repetition signal of 1-7 RLL equivalent to 8T (pit length = 0.68 μm) was performed under the pulse train type recording strategy condition, and pits were formed well. I was able to record. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), the recording laser power = 6 mW, 8TCNR = 55 dB, modulation degree = 0.78. The result was observed. Table 1 summarizes the signal evaluation results.
[0096]
(Example 9)
Directly on a disc-shaped substrate with an outer diameter of 120 mm φ and a thickness of 1.1 mm having continuous guide grooves made of polycarbonate resin (track pitch: 0.32 μm, groove width: 0.15 μm, groove depth: 35 nm) Fullerene C60 similar to that used in Example 1 was deposited by a vacuum deposition method to form a recording layer having a thickness of 30 nm. Thereafter, an inorganic SiO 2 is formed on the recording layer. ₂ The film was formed into a film having a thickness of 25 nm using a sputtering device (CFS-8EP) manufactured by Tokuda Seisakusho Co. A cured optical recording medium was produced.
[0097]
With respect to the optical recording medium having the recording layer formed as described above, an evaluator equipped with a blue laser head having a wavelength of 405 nm and a numerical aperture of 0.85 (PULSTEC DDU1000 (Blue)) has a linear velocity of 5.3 m / s. When the ON / OFF repetition signal at 2T equivalent to 1-7 RLL (minimum pit length = 0.17 μm) was recorded from the UV curable resin side to the on-groove under the pulse train type recording strategy condition. Pits were formed well and recording was possible. Further, the recording portion was reproduced with the same optical pick (reproduction power = 0.3 mW, linear velocity 5.3 m / s). As a result, 2TCNR = 45 dB was obtained at a recording laser power of 6 mW.
[0098]
Subsequently, using the same optical pickup, an ON / OFF repetition signal of 1-7 RLL equivalent to 8T (pit length = 0.68 μm) was performed under the pulse train type recording strategy condition, and pits were formed well. I was able to record. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), a good result of 8 TCNR = 48 dB was observed with the recording laser power = 6 mW. Table 1 summarizes the signal evaluation results.
[0099]
(Example 10)
The EFM + of the optical recording medium manufactured in Example 1 was evaluated at a linear velocity of 3.5 m / s by an evaluator (PULSTEC DDU1000 (Blue)) equipped with a red laser head having a wavelength of 650 nm and a numerical aperture of 0.60. When the ON / OFF repetition signal at the equivalent of 3T (minimum pit length = 0.40 μm) was recorded from the UV curable resin side to the on-groove under the pulse train type recording strategy condition, the pits were found to be excellent. Formed and recorded. Furthermore, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.3 mW, linear velocity 3.5 m / s), 2TCNR = 52 dB was obtained at a recording laser power = 24 mW.
[0100]
Subsequently, using the same optical pickup, an ON / OFF repetition signal of 1-7 RLL equivalent to 8T (pit length = 1.87 μm) was carried out under pulse train type recording strategy conditions, and pits were formed well. I was able to record. Further, as a result of reproducing the recording portion with the same optical pick (reproduction power = 0.7 mW, linear velocity 5.3 m / s), a favorable result of 14 TCNR = 58 dB was observed at a recording laser power of 24 mW. Table 1 summarizes the signal evaluation results.
[0101]
(Example 11)
The optical recording medium recorded in Example 10 was recorded at a linear velocity of 3.5 m / s by an evaluator equipped with a blue laser head having a wavelength of 405 nm and a numerical aperture of 0.65 (PULSTEC DDU1000 (Blue)). Was reproduced (reproduction power = 0.7 mW, linear velocity: 3.5 m / s). As a result, sufficiently satisfactory results of 3 TCNR = 55 dB and 14 TCNR = 60 dB were observed. Table 1 summarizes the signal evaluation results.
[0102]
【The invention's effect】
According to the present invention, a laser beam irradiation forms a good recording pit with thermal deformation and / or thermal denaturation in a layer adjacent to a recording layer or a transparent substrate, so that it is easy to obtain a signal amplitude. In addition, it is possible to provide a recording medium having excellent long-term storage reliability. By selecting a recording layer mainly composed of a robust fullerene skeleton having an extremely high decomposition temperature on a transparent substrate, an optical head having a laser having a wavelength of 390 to 700 nm, which has been attracting much attention as a high-density optical recording medium, can be obtained. It is possible to provide a recordable / reproducible optical information recording medium by using the optical information recording medium.
[0103]
[Table 1]

[Brief description of the drawings]
FIG. 1 is a schematic view showing one configuration example of an optical recording medium of the present invention.
FIG. 2 is a schematic diagram showing another configuration example of the optical recording medium of the present invention.
FIG. 3 is a schematic diagram showing another configuration example of the optical recording medium of the present invention.
FIG. 4 is a schematic diagram showing another configuration example of the optical recording medium of the present invention.
FIG. 5 is a schematic diagram showing another configuration example of the optical recording medium of the present invention.
FIG. 6 is a schematic diagram showing another configuration example of the optical recording medium of the present invention.
FIG. 7 is a schematic diagram showing another configuration example of the optical recording medium of the present invention.
FIG. 8 is a diagram showing an eye pattern of a signal of the optical recording medium of the present invention.
FIG. 9 is a photograph showing a physical deformation mark of a substrate pit after recording.
[Explanation of symbols]
1: substrate, 2: recording layer, 3: reflective layer, 4: protective layer
5: adhesive layer, 6: transparent protective layer, 7: spacer
8: dummy substrate, 9: light transmitting layer (sheet), 11: substrate
12: recording layer, 13: reflective layer, 14: protective layer
15: dummy substrate layer, 11 ': support substrate, 12': recording layer
13 ': reflective layer, 14': transparent protective layer, 15 ': light transmitting layer

Claims (5)

A recording layer containing at least a fullerene compound is formed directly on a layer transparent to the recording / reproducing wavelength or via another layer, and the recording layer generates heat by laser light irradiation and is adjacent to the recording layer. An optical recording medium, wherein recording pits can be formed in a transparent layer or the another layer. The optical recording medium according to claim 1, wherein the thickness of the recording layer is 60 nm or less. 3. The optical recording medium according to claim 1, wherein the recording pit is formed by thermal deformation or thermal denaturation. 4. The optical recording medium according to claim 1, wherein the fullerene compound of the recording layer contains at least C60 fullerene. 5. The optical recording medium according to claim 1, wherein recording and / or reproduction is possible in a laser wavelength range of 390 nm to 700 nm.

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