JP4112376B2 - Optical recording medium and recording method thereof - Google Patents

Description

（式中、Ｘ、Ｙはアルキル、アリール等の有機置換基を表わし、Ｚはアニオンを表わし、ｎは正数を表わす。）
【００４３】
但し、上記シアニン色素のうちでも、特に分解特性が良好な色素として、ｎが２、または３であるシアニン色素が好ましい。
ｎが２又は３であるシアニン色素では、青色レーザ波長領域以下の波長が記録再生波長となった場合、記録再生波長における反射率の向上を図れ、また記録再生波長から主吸収帯を遠ざけることができるため、色素の光学定数の波長依存性が大幅に改善できるためである。但し、本発明では、ｎの値を２又は３に限定するものではない。
【００４４】
また、上記一般式（１）中の左右の複素環は、それ単独で３００ｎｍ以上に吸収ピークを有する分子・分子団であることが好ましい。さらに具体的に言えば、青色レ−ザ波長領域で、記録による大きな吸収係数の増加を図るためには、一般式（１）中、左右の複素環のうち少なくとも１つは、三環式以上の多環式縮合環であることが好ましい。
これによって、分解時の吸収係数の増加が、青色領域で大きく検出できる。
【００４５】
色素層の形成は蒸着、スパッタリング、ＣＶＤ又は溶剤塗布などの通常の手段によって行なうことができる。塗布法を用いる場合には、上記染料などを有機溶剤に溶解して、スプレー、ローラーコーティング、ディッピング又はスピンコーティングなどの慣用のコーティング法で行なうことができる。
量産性、コスト面からはスピンコート法が好ましい。
また、厚みの均一な記録層が得られるという点からは、塗布法よりも真空蒸着法等のほうが好ましい。
スピンコート法による成膜の場合、回転数は５００〜１５０００ｒｐｍが好ましく、スピンコートの後、場合によっては加熱あるいは溶媒蒸気にあてる等の処理を行なっても良い。
ドクターブレード法、キャスト法、スピンコート法、浸漬法等の塗布方法により記録層を形成する場合の塗布溶媒としては、基板を侵さない溶媒であればよく、特に限定されない。
【００４６】
用いられる有機溶剤としては、一般に、ジアセトンアルコール、メタノール、エタノール、イソプロパノールなどアルコール類、アセトン、メチルエチルケトン、シクロヘキサノン、３−ヒドロキシ−３−メチル−２−ブタノンなどのケトン類、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジメチルホルムアミドなどのアミド類、ジメチルスルホキシドなどのスルホキシド類、テトラヒドロフラン、ジオキサン、ジエチルエーテル、エチレングリコールモノメチルエーテルなどのエーテル類、酢酸メチル、酢酸エチルなどのエステル類、乳酸メチル、乳酸エチル、イソ酪酸メチル等のヒドロキシカルボン酸エステル系溶媒等、クロロホルム、塩化メチレン、ジクロロエタン、四塩化炭素、トリクロロエタンなどの脂肪族ハロゲン化炭素類、テトラフルオロプロパノール、オクタフルオロペンタノール、ヘキサフルオロブタノール等のパーフルオロアルキルアルコール系溶媒等、ベンゼン、キシレン、モノクロロベンゼン、ジクロロベンゼンなどの芳香族類、あるいはメトキシエタノール、エトキシエタノールなどのセルソルブ類、ヘキサン、ペンタン、シクロヘキサン、メチルシクロヘキサンなどの炭化水素類などが挙げられる。
色素層の膜厚は、１００Å〜１０μｍ、好ましくは１００Å〜２０００Åが適当である。
【００４７】
また、有機化合物層は、有機化合物の安定や耐光性向上のために、一重項酸素クエンチャーとして遷移金属キレート化合物（例えば、アセチルアセトナートキレート、ビスフェニルジチオール、サリチルアルデヒドオキシム、ビスジチオ−α−ジケトン等）等や、記録感度向上のために金属系化合物等の記録感度向上剤を含有していても良い。
【００４８】
ここで、金属系化合物とは、遷移金属等の金属が原子、イオン、クラスター等の形で化合物に含まれるものを言い、例えばエチレンジアミン系錯体、アゾメチン系錯体、フェニルヒドロキシアミン系錯体、フェナントロリン系錯体、ジヒドロキシアゾベンゼン系錯体、ジオキシム系錯体、ニトロソアミノフェノール系錯体、ピリジルトリアジン系錯体、アセチルアセトナート系錯体、メタロセン系錯体、ポルフィリン系錯体のような有機金属化合物が挙げられる。金属原子としては特に限定されないが、遷移金属であることが好ましい。
【００４９】
さらに、必要に応じて他系統の色素を併用することもできる。
他系統の色素としては含金属アゾ系色素、フタロシアニン系色素、ナフタロシアニン系色素、シアニン系色素、アゾ系色素、スクアリリウム系色素、含金属インドアニリン系色素、トリアリールメタン系色素、メロシアニン系色素、アズレニウム系色素、ナフトキノン系色素、アントラキノン系色素、インドフェノール系色素、キサンテン系色素、オキサジン系色素、ピリリウム系色素等が挙げられる。
【００５０】
さらに、必要に応じて、バインダー、レベリング剤、消泡剤等を併用することもできる。
好ましいバインダーとしては、ポリビニルアルコール、ポリビニルピロリドン、ニトロセルロース、酢酸セルロース、ケトン系樹脂、アクリル系樹脂、ポリスチレン系樹脂、ウレタン系樹脂、ポリビニルブチラール、ポリカーボネート、ポリオレフィン等が挙げられる。
【００５１】
光吸収機能と光反射機能を兼用する層の上には、直接または上引層等を介して、さらに反射層を形成してもよく、その膜厚は好ましくは、厚さ５０〜３００ｎｍである。
反射層の材料としては、再生光の波長で反射率の充分高いもの、例えば、Ａｕ、Ａｌ、Ａｇ、Ｃｕ、Ｔｉ、Ｃｒ、Ｎｉ、Ｐｔ、Ｔａ、Ｃｒ及びＰｂ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、Ａｌ、Ａｇは反射率が高く反射層の材料として適している。これらを主成分とする以外に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、Ｒｈ、Ｉｒ、Ｃｕ、Ｚｎ、Ｃｄ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｔｅ、Ｐｂ、Ｐｏ、Ｓｎ、Ｂｉなどの金属及び半金属を挙げることができる。
なかでもＡｇを主成分としているものはコストが安い点、高反射率が出やすい点から特に好ましい。
【００５２】
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。
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、真空蒸着法等が挙げられる。
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、密着性の向上等のために公知の無機系または有機系の上引層、下引層、あるいは接着層を設けることもできる。
【００５３】
光吸収機能と光反射機能を兼用する層、あるいは反射層の上に形成する保護層の材料としては、光吸収機能と光反射機能を兼用する層、あるいは反射層を外力から保護するものであれば特に限定されない。有機物質の材料としては、熱可塑性樹脂、熱硬化性樹脂、電子線硬化性樹脂、ＵＶ硬化性樹脂等を挙げることができる。
また、無機物質としては、ＳｉＯ_２、ＳｉＮ_４、ＭｇＦ_２、ＳｎＯ_２等が挙げられる。
熱可塑性樹脂、熱硬化性樹脂などは適当な溶剤に溶解して塗布液を塗布し、乾燥することによって形成することができる。
ＵＶ硬化性樹脂は、そのままもしくは適当な溶剤に溶解して塗布液を調製した後にこの塗布液を塗布し、ＵＶ光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。
ＵＶ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系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いし、１層だけではなく多層膜にして用いても良い。
【００５４】
保護層の形成方法としては、有機化合物層と同様にスピンコート法やキャスト法等の塗布法やスパッタ法や化学蒸着法等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０．１〜１００μｍの範囲であるが、本発明においては、３〜３０μｍが好ましい。
また、光吸収機能と光反射機能を兼用する層、あるいは反射層面に更に基板を貼り合わせてもよく、また光吸収機能と光反射機能を兼用する層、あるいは反射層面相互を内面とし対向させ光学記録媒体２枚を貼り合わせても良い。
基板鏡面側に、表面保護やゴミ等の付着防止のために紫外線硬化樹脂層や、無機系薄膜等を成膜してもよい。
【００５５】
カバー層は、高密度化を図るために、高ＮＡのレンズを用いる場合必要となる。
例えば高ＮＡ化すると、再生光が透過する部分の厚さを薄くする必要がある。
これは、高ＮＡ化に伴い、光学ピックアップの光軸に対してディスク面が垂直からズレる角度（いわゆるチルト角、光源の波長の逆数と対物レンズの開口数の積の２乗に比例する）により発生する収差の許容量が小さくなるためであり、このチルト角が基板の厚さによる収差の影響を受け易いためである。
したがって、基板の厚さを薄くしてチルト角に対する収差の影響をなるべく小さくするようにしている。
【００５６】
そこで、例えば基板上に凹凸を形成して記録層とし、その上に反射膜を設け、さらにこの上に光を透過する薄膜である光透過性のカバー層を設けるようにし、カバー層側から再生光を照射して記録層の情報を再生するような光記録媒体や、基板上に反射膜を設け、その上に記録膜を形成して記録層とし、さらにこの上に光透過性を有するカバー層を設けるようにし、カバー層側から再生光を照射して記録層の情報を再生するような光記録媒体が提案されている。このようにすれば、カバー層を薄型化していくことで対物レンズの高ＮＡ化に対応可能である。つまり、薄いカバー層を設け、このカバー層側から記録再生することで、さらなる高記録密度化を図ることができる。
なお、このようなカバー層はポリカーボネートシートや、紫外線硬化型樹脂により形成されるのが一般的である。また、本発明でいうカバー層とは、カバー層を接着するための層を含めてもよい。
【００５７】
本発明による光記録媒体における情報の記録原理を図２又は図３を参照して説明すると、次のとおりである。
光源として５００ｎｍ以下の波長のレーザを用いて、５〜１５ｍＷ程度のパワーで光記録媒体に照射すると、光吸収機能と光反射機能を兼用する層が光を吸収し、昇温して熱を放出する。この熱は有機化合物層に伝達されて有機化合物の分解・変質を誘発する。この分解・変質によって、有機化合物は、有機化合物を構成していた個々の分子や分子団に分断され、これらの個々の分子や分子団が持つ吸収帯の強度を増加させる。この個々の分子や分子団が持つ吸収帯の強度増加によって形成された記録ピットは、未記録部と大きな反射率差を生むため、再生レーザを照射するとことで明瞭に検出することが可能となる。
あるいは、光源として５００ｎｍ以下の波長のレーザを用いて、５〜１５ｍＷ程度のパワーで光記録媒体に照射すると、光吸収機能と光反射機能を兼用する層が光を吸収し、昇温して熱を放出する。この熱は有機化合物層に伝達されて有機化合物の分解・変質を誘発する。この分解・変質によって、有機化合物は体積減少を起こし、光吸収機能と光反射機能を兼用する層が有機材料層側に変形を起こす。あるいは、光源として５００ｎｍ以下の波長のレーザを用いて、５〜１５ｍＷ程度のパワーで光記録媒体に照射すると、光吸収機能と光反射機能を兼用する層が光を吸収し、昇温して自らが熱膨張し、有機材料層側に変形する。
この光吸収機能と光反射機能を兼用する層の変形によって形成された記録ピットは、未記録部と大きな反射率差を生むため、再生レーザを照射するとことで明瞭に検出することが可能となる。
【００５８】
以下、図２又は図３の各構成の機能を説明する。
図２は、青色レーザ波長対応の追記型光記録媒体を実現させる層構成の一例を示すもので、基板上に有機化合物層、光吸収機能と光反射機能を兼用する層が順次設けられた構造を有する。この構造では、通常記録再生が基板側から行なわれる。この構造では、基板側からのレーザ光照射により光吸収機能と光反射機能を兼用する層が発熱し、この熱によって有機化合物の分解あるいは変質等の状態変化を誘発させ、記録再生波長での吸収係数を増加させることで、あるいはこの熱によって有機化合物の分解あるいは変質等の状態変化を誘発させ、有機化合物層の体積減少を生じさせ、光吸収機能と光反射機能を兼用する層を有機化合物層側へ変形させることで、あるいはこの熱によって光吸収機能と光反射機能を兼用する層を熱膨張させ、光吸収機能と光反射機能を兼用する層を有機化合物層側へ変形させることで記録が行なわれる。なお、未記録時の反射率を向上させ記録再生装置への負荷を減らし、かつ記録再生特性を向上させるために、有機化合物層と光吸収機能と光反射機能を兼用する層の屈折率差を大きくすることが好ましい。
【００５９】
図３は、青色レーザ波長対応の追記型光記録媒体を実現させる層構成の別の一例を示すもので、基板上に光吸収機能と光反射機能を兼用する層、有機化合物層、カバー層が順次設けられた構造を有する。この構造では、通常記録再生がカバー層側から行なわれる。この構造では、カバー層側からのレーザ光照射により光吸収機能と光反射機能を兼用する層が発熱し、この熱によって有機化合物の分解あるいは変質等の状態変化を誘発させ、記録再生波長での吸収係数を増加させることで、あるいはこの熱によって有機化合物の分解あるいは変質等の状態変化を誘発させ、有機化合物層の体積減少を生じさせ、光吸収機能と光反射機能を兼用する層を有機化合物層側へ変形させることで、あるいはこの熱によって光吸収機能と光反射機能を兼用する層を熱膨張させ、光吸収機能と光反射機能を兼用する層を有機化合物層側へ変形させることで、あるいはこの熱によって基板を熱膨張させ、光吸収機能と光反射機能を兼用する層を有機化合物層側へ変形させることで記録が行なわれる。 なお、未記録時の反射率を向上させ記録再生装置への負荷を減らし、かつ記録再生特性を向上させるために、有機化合物層と光吸収機能と光反射機能を兼用する層の屈折率差を大きくすることが好ましい。
【００６０】
【実施例】
以下、本発明の実施例を具体的に説明するが、本発明は必ずしもこれに限られるものではない。
〔実施例１〕
本発明の層構成と記録原理によって、良好な記録再生が実現できることを検証する。
基板上に、未記録時の主吸収帯が記録再生波長に対して長波長側に存在する有機化合物層、光吸収機能と光反射機能を兼用する層（Ｓｉ）を積層した光記録媒体に対し、有機化合物層の膜厚と、Ｓｉ層の膜厚を変化させた時の反射率と変調度を計算した。
なお、有機化合物層の未記録時の複素屈折率は、１．５０−ｉ０．０５０であり、記録後の複素屈折率は１．５０−ｉ０．１２５と仮定した（なお、記録再生波長は４０５ｎｍである）。
その結果は、変調度（ＭＡ）は図８、反射率（Ｒ）は図９に示すとおりである。
また、高い変調度と高い反射率が得られる領域を明確にするために、変調度×反射率（ＭＡ×Ｒ）を図１０に示した。
なお、いずれの図も横軸は有機化合物層（色素層）の膜厚、縦軸はＳｉ層の膜厚を示す。
この結果から、例えば有機化合物層の膜厚が６０ｎｍ以上で、Ｓｉ層の膜厚が１０〜４０ｎｍの領域、あるいは有機化合物層の膜厚が８０ｎｍ以上で、Ｓｉ層の膜厚が５０ｎｍ以上の領域で、変調度５０％程度、反射率３０〜４０％が得られることがわかり、青色レーザ波長領域でも有機化合物を用いた光記録媒体において、高反射率化と高変調度化が図れることが確かめられた。
なお、上記の最適条件は、記録による有機化合物層の複素屈折率変化が、１．５０−ｉ０．０５０から１．５０−ｉ０．１２５である場合のものであって、本発明はこれに限定されるものではない。
有機化合物層の吸収係数（複素屈折率の虚部）の増加が大きくなれば、さらに最適条件の範囲は広がり、例えば、さらに有機化合物層の膜厚を薄膜化することができる（つまり浅い溝の基板が使用できる）。
また、本実施例では、基板側からの記録再生を考えた基板／有機化合物層／光吸収機能と光反射機能を兼用する層という構成で反射率や変調度の計算を行なったが、記録再生波長に対しカバー層が充分厚いこと、および基板とカバー層の屈折率がほぼ同一であることから、カバー側からの記録再生を考えた基板／光吸収機能と光反射機能を兼用する層／有機化合物層／カバー層という構成での反射率や変調度もほとんど同一となることは明白である。
【００６１】
〔実施例２〕
本発明の層構成と記録原理によって、良好な記録再生が実現できることを検証する。
基板上に、未記録時の主吸収帯が記録再生波長に対して長波長側に存在する有機化合物層、光吸収機能と光反射機能を兼用する層（Ｓｉ）を積層した光記録媒体に対し、有機化合物層の膜厚と、Ｓｉ層の膜厚を変化させた時の反射率と変調度を計算した。
なお、有機化合物層の未記録時の複素屈折率は、１．５０−ｉ０．０２であり、記録後の複素屈折率は（１．５０×[χ]）−ｉ（０．０２×２．０）と仮定した（なお、記録再生波長は４０５ｎｍであり、χ は０．８、１．０、１．２、１．５である）。
その結果は、図１１（ａ）〜（ｉ）のようになった。
（ａ）は未記録時の反射率（Ｒ）を表す図であり、（ｂ）はχ＝０．８の時の変調度（ＭＡ）を表す図、（ｃ）はχ＝０．８の時の変調度×反射率（ＭＡ×Ｒ）を示す図であり、（ｄ）はχ＝１．０の時の変調度（ＭＡ）を表す図、（ｅ）はχ＝１．０の時の変調度×反射率（ＭＡ×Ｒ）を示す図であり、（ｆ）はχ＝１．２の時の変調度（ＭＡ）を表す図、（ｇ）はχ＝１．２の時の変調度×反射率（ＭＡ×Ｒ）を示す図であり、（ｈ）はχ＝１．５の時の変調度（ＭＡ）を表す図、（ｉ）はχ＝１．５の時の変調度×反射率（ＭＡ×Ｒ）を示す図である。なお、上記結果で変調度×反射率（ＭＡ×Ｒ）を示したのは、高い変調度と高い反射率が得られる領域を明確にするためである。
また、いずれの図も横軸は有機化合物層（色素層）の膜厚、縦軸はＳｉ層の膜厚を示す。
この計算結果から、高変調度と高反射率を確保するためには、記録前後で有機化合物層の屈折率が低下しないことが必要であり（すなわち、（記録後の有機化合物層の複素屈折率実部）≧（記録前の有機化合物層の複素屈折率実部））、記録による吸収係数の増加の程度によらず、Ｓｉ膜厚が１０ｎｍ以上、さらに好ましくは１０〜３０ｎｍの範囲にあれば、高変調度と高反射率が達成できることがわかる。
また、記録によって吸収係数が増加する割合が高いほど、高変調度と高反射率を達成できる有機化合物層膜厚が薄膜化できることがわかる。
本実施例では、基板側からの記録再生を考えた基板／有機化合物層／光吸収機能と光反射機能を兼用する層という構成で反射率や変調度の計算を行なったが、記録再生波長に対しカバー層が充分厚いこと、および基板とカバー層の屈折率がほぼ同一であることから、カバー側からの記録再生を考えた基板／光吸収機能と光反射機能を兼用する層／有機化合物層／カバー層という構成での反射率や変調度もほとんど同一となることは明白である。
【００６２】
〔実施例３〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０２とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０２×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１２（ａ）〜（ｉ）のようになった。
【００６３】
〔実施例４〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０２とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０２×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１３（ａ）〜（ｉ）のようになった。
【００６４】
〔実施例５〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０５×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１４（ａ）〜（ｉ）のようになった。
【００６５】
〔実施例６〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０５×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１５（ａ）〜（ｉ）のようになった。
【００６６】
〔実施例７〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０５×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１６（ａ）〜（ｉ）のようになった。
【００６７】
〔実施例８〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０７とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０７×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１７（ａ）〜（ｉ）のようになった。
【００６８】
〔実施例９〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０７とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０７×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１８（ａ）〜（ｉ）のようになった。
【００６９】
〔実施例１０〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．０７とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．０７×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図１９（ａ）〜（ｉ）のようになった。
【００７０】
〔実施例１１〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．１０とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．１０×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２０（ａ）〜（ｉ）のようになった。
【００７１】
〔実施例１２〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ ０．１０とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．１０×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２１（ａ）〜（ｉ）のようになった。
【００７２】
〔実施例１３〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．１０とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．１０×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２２（ａ）〜（ｉ）のようになった。
【００７３】
〔実施例１４〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．１５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．１５×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２３（ａ）〜（ｉ）のようになった。
【００７４】
〔実施例１５〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．１５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．１５×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２，１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２４（ａ）〜（ｉ）のようになった。
【００７５】
〔実施例１６〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．１５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．１５×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２５（ａ）〜（ｉ）のようになった。
【００７６】
〔実施例１７〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．２０とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．２０×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２６（ａ）〜（ｉ）のようになった。
【００７７】
〔実施例１８〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．２０とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．２０×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２７（ａ）〜（ｉ）のようになった。
【００７８】
〔実施例１９〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．２０とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．２０×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレ−ションを行なった。
その結果は、図２８（ａ）〜（ｉ）のようになった。
【００７９】
〔実施例２０〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．２５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．２５×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図２９（ａ）〜（ｉ）のようになった。
【００８０】
〔実施例２１〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．２５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．２５×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３０（ａ）〜（ｉ）のようになった。
【００８１】
〔実施例２２〕
有機化合物層の未記録時の複素屈折率を、１．５０−ｉ０．２５とし、記録後の複素屈折率を（１．５０×[χ]）−ｉ（０．２５×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３１（ａ）〜（ｉ）のようになった。
【００８２】
〔実施例２３〕
有機化合物層の未記録時の複素屈折率を、１．７０−ｉ０．０５とし、記録後の複素屈折率を（１．７０×[χ]）−ｉ（０．０５×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２，１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３２（ａ）〜（ｉ）のようになった。
【００８３】
〔実施例２４〕
有機化合物層の未記録時の複素屈折率を、１．７０−ｉ０．０５とし、記録後の複素屈折率を（１．７０×[χ]）−ｉ（０．０５×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３３（ａ）〜（ｉ）のようになった。
【００８４】
〔実施例２５〕
有機化合物層の未記録時の複素屈折率を、１．７０−ｉ０．０５とし、記録後の複素屈折率を（１．７０×[χ]）−ｉ（０．０５×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３４（ａ）〜（ｉ）のようになった。
【００８５】
〔実施例２６〕
有機化合物層の未記録時の複素屈折率を、１．９０−ｉ０．０５とし、記録後の複素屈折率を（１．９０×[χ]）−ｉ（０．０５×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３５（ａ）〜（ｉ）のようになった。
【００８６】
〔実施例２７〕
有機化合物層の未記録時の複素屈折率を、１．９０−ｉ０．０５とし、記録後の複素屈折率を（１．９０×[χ]）−ｉ（０．０５×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３６（ａ）〜（ｉ）のようになった。
【００８７】
〔実施例２８〕
有機化合物層の未記録時の複素屈折率を、１．９０−ｉ０．０５とし、記録後の複素屈折率を（１．９０×[χ]）−ｉ（０．０５×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３７（ａ）〜（ｉ）のようになった。
【００８８】
〔実施例２９〕
有機化合物層の未記録時の複素屈折率を、１．３０−ｉ０．０５とし、記録後の複素屈折率を（１．３０×[χ]）−ｉ（０．０５×２．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２，１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３８（ａ）〜（ｉ）のようになった。
【００８９】
〔実施例３０〕
有機化合物層の未記録時の複素屈折率を、１．３０−ｉ０．０５とし、記録後の複素屈折率を（１．３０×[χ]）−ｉ（０．０５×４．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図３９（ａ）〜（ｉ）のようになった。
【００９０】
〔実施例３１〕
有機化合物層の未記録時の複素屈折率を、１．３０−ｉ０．０５とし、記録後の複素屈折率を（１．３０×[χ]）−ｉ（０．０５×６．０）と仮定し（なお、記録再生波長は４０５ｎｍであり、χは０．８、１．０、１．２、１．５である）、実施例２と同様なシュミレーションを行なった。
その結果は、図４０（ａ）〜（ｉ）のようになった。
【００９１】
なお、上記実施例３〜３１での計算結果を示す図、すなわち図１２〜４０では、（ａ）は未記録時の反射率（Ｒ）を表す図であり、（ｂ）はχ＝０．８の時の変調度（ＭＡ）を表す図、（ｃ）はχ＝０．８の時の変調度×反射率（ＭＡ×Ｒ）を示す図であり、（ｄ）はχ＝１．０の時の変調度（ＭＡ）を表す図、（ｅ）はχ＝１．０の時の変調度×反射率（ＭＡ×Ｒ）を示す図であり、（ｆ）はχ＝１．２の時の変調度（ＭＡ）を表す図、（ｇ）はχ＝１．２の時の変調度×反射率（ＭＡ×Ｒ）を示す図であり、（ｈ）はχ＝１．５の時の変調度（ＭＡ）を表す図、（ｉ）はχ＝１．５の時の変調度×反射率（ＭＡ×Ｒ）を示す図である。なお、上記結果で変調度×反射率（ＭＡ×Ｒ）を示したのは、高い変調度と高い反射率が得られる領域を明確にするためである。
また、いずれの図も横軸は有機化合物層（色素層）の膜厚、縦軸はＳｉ層の膜厚を示す。
【００９２】
以上、実施例２〜３１の計算結果から、高変調度と高反射率を確保するためには、記録前後で有機化合物層の屈折率が低下しないことが必要であり（すなわち、（記録後の有機化合物層の複素屈折率実部）≧（記録前の有機化合物層の複素屈折率実部））、記録による吸収係数の増加の程度によらず、Ｓｉ膜厚が１０ｎｍ以上、さらに好ましくは１０〜３０ｎｍの範囲にあれば、高変調度と高反射率が達成できることがわかる。
また、記録によって吸収係数が増加する割合が高いほど、高変調度と高反射率を達成できる有機化合物層膜厚が薄膜化できることがわかる。
本実施例では、基板側からの記録再生を考えた基板／有機化合物層／光吸収機能と光反射機能を兼用する層という構成で反射率や変調度の計算を行なったが、記録再生波長に対しカバー層が充分厚いこと、および基板とカバー層の屈折率がほぼ同一であることから、カバー側からの記録再生を考えた基板／光吸収機能と光反射機能を兼用する層／有機化合物層／カバー層という構成での反射率や変調度もほとんど同一となることは明白である。
【００９３】
〔実施例３２〕
次いで、記録によって有機化合物層の吸収係数（複素屈折率の虚部）が増加することを確かめた。
案内溝（溝深さ５５ｎｍ）を有するポリカーボネート基板上に、下記式（２）［（株）林原生物化学研究所製の色素（ＮＫ３５７８）］からなる有機化合物層をスピンコート法によって形成し、さらにその上にＳｉ層（光吸収機能と光反射機能を兼用する層）２５ｎｍを設け、さらにその上に紫外線硬化型樹脂からなる保護層を約２μｍ設けた光記録媒体を作成した。
なお、４０５ｎｍにおける下記式（２）の複素屈折率は、１．５１０−ｉ０．０５０であり、従来の追記型の光記録媒体に用いる有機化合物に要求される複素屈折率に対し、著しく劣った複素屈折率である（例えばＤＶＤ−Ｒに用いられている色素の、記録再生波長近傍での複素屈折率は、例えば ２．５−ｉ ０．１０程度である）。
上記光記録媒体に対し、パルステック工業（株）製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、以下の条件で記録を行なった。
その結果、変調度約５８％の信号が得られた。
また、この光記録媒体の光吸収機能と光反射機能を兼用する層を剥がし、記録部分と未記録部分の色素をエタノールで溶かし、それぞれスペクトルを測定した。
その結果、図４１に示すように、記録部分では吸収係数（複素屈折率の虚部）が明らかに増加していることが認められ（記録はグルーブ部のみに行なわれたため、記録部のスペクトルには多量の未記録部成分が存在する）、本発明の光記録媒体における記録原理を確認できた。
また、実施例１で仮定したように、記録によって有機化合物層の吸収係数（複素屈折率の虚部）が約２．５倍に増加すると仮定した根拠が裏付けられた（実際、下記式（２）では６倍以上の吸収係数の増加が確認できたため、吸収係数が約２．５倍増加すると仮定した実施例１の結果は、充分な信頼性を持つ）。
但し、本発明では、記録による有機化合物層の吸収係数（複素屈折率の虚部）の増加が約２．５倍であることに限定するものではない。
また、この光記録媒体をＦＩＢ（集束イオンビーム加工装置：Focused Ion Beam）で切断し、記録部の様子をＳＥＭおよびＴＥＭにより観察した。その結果、Ｓｉ層が有機化合物層側へ平均約３０ｎｍほど変形していることが確認できた。これは、言い換えれば有機化合物層が記録によって体積減少したことを裏付ける結果でもある。
【００９４】
【化２】

【００９５】
（記録条件）
記録線密度：１Ｔ＝０．０９１７（μｍ）
記録線速度：６．０（ｍ／ｓ）
記録ストラテジ：Basic strategy Ｔ_ｔｏｐ−Ｔ_ｍｐ＝１．４０−０．７５（Ｔ）
記録パワー：８．５（ｍｗ）
記録パタ−ン：８−１６変調信号
【００９６】
以上、本発明の実施例１〜３２から、本発明の光記録媒体の層構成と記録原理が、青色レーザ波長対応の有機化合物からなる追記型光記録媒体の実現に非常に有効であることが確認できた。
また、従来有機化合物を用いた光記録媒体では、有機化合物層で熱を発生させる必要があったため、有機化合物層を薄膜化できず、深い溝（例えば１５０〜１８０ｎｍ）を必要としていたが、本発明の記録原理によって、有機化合物の薄膜化が可能となるため、５０ｎｍ程度という非常に浅い溝を有する基板が適用できることが確かめられた。
但し、本発明では、基板の溝深さを約５０ｎｍに限定するものではない。
【００９７】
〔実施例３３〕
従来のＤＶＤ−Ｒに用いることができる下記一般式（３）で示される色素の複素屈折率（屈折率ｎと吸収係数ｋ）、本発明で使用でき、かつ従来のＤＶＤ−Ｒにも用いることができる色素（ＮＫ４３８２、（株）林原生物化学研究所製）の複素屈折率（屈折率ｎと吸収係数ｋ）、およびＳｉの複素屈折率（屈折率ｎと吸収係数ｋ）を測定した。
従来のＤＶＤ−Ｒに用いることができる下記一般式（３）で示される色素の複素屈折率（屈折率ｎと吸収係数ｋ）は図４２に、本発明で使用でき、かつ従来のＤＶＤ−Ｒにも用いることができる色素（ＮＫ４３８２）の複素屈折率（屈折率ｎと吸収係数ｋ）は図４３に、およびＳｉの複素屈折率（屈折率ｎと吸収係数ｋ）は図４４に示すとおりである。
その結果、従来の記録材料に対し、記録再生波長を有機化合物の吸収帯の長波長側に位置させるような従来の記録方法の場合（図４２）、記録再生波長の変動に対し、屈折率ｎや吸収係数ｋが大きく変動することが確認できた。
一方、本発明では、従来の記録材料に対し、記録再生波長を有機化合物の吸収帯から充分短波長側に位置させる記録方法であるため（図４３）、記録再生波長の変動に対し、屈折率ｎや吸収係数ｋがほとんど変動しないことが確認できた。
また、光吸収機能と光反射機能を兼用する層として用いるＳｉも記録再生波長の変動に対し、屈折率ｎや吸収係数ｋが大きく変動しないことが確認できた。
以上、本発明の光記録媒体の層構成によって、記録再生波長の変動に対し、記録感度や変調度、ジッタやエラー率といったような記録特性や、反射率等の変化が少ない追記型光記録媒体が実現できることが確認できた。
【００９８】
【化３】

【００９９】
【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、本発明の光記録媒体とその記録原理によって、青色レーザ波長以下対応の有機化合物からなる追記型の光記録媒体、転写性のよい浅溝基板が利用可能な有機化合物からなる追記型の光記録媒体、記録再生波長の変動に対し、記録感度や変調度、ジッタやエラー率といったような記録特性や、反射率等の変化が少ない追記型の光記録媒体を容易に、しかも安価に提供することができる。
また、本発明の請求項１の追記型光記録媒体の層構成によって、従来の追記型光記録媒体の記録層に要求される光学定数と同程度の光学定数が得ることが困難な青色レーザ波長以下の領域であっても、基板側からの記録再生で、高密度化が図れ、かつ良好な記録再生特性が得られる追記型光記録媒体を実現できる。また、転写性のよい浅溝基板でも記録再生が容易に行なえる追記型光記録媒体、および、記録再生波長の変動に対し、記録再生特性の変化が少ない追記型光記録媒体が実現できる。
また、本発明の請求項２および請求項３の追記型光記録媒体の層構成と有機化合物の規定によって、従来の追記型光記録媒体の記録層に要求される光学定数と同程度の光学定数が得ることが困難な青色レーザ波長以下の領域であっても、基板側からの記録再生で、高密度化が図れ、かつ良好な記録再生特性が得られる追記型光記録媒体を実現できる。また、転写性のよい浅溝基板でも記録再生が容易に行なえる追記型光記録媒体、および、記録再生波長の変動に対し、記録再生特性の変化が少ない追記型光記録媒体が実現できる。
また、本発明の請求項４の追記型光記録媒体の層構成によって、従来の追記型光記録媒体の記録層に要求される光学定数と同程度の光学定数が得ることが困難な青色レーザ波長以下の領域であっても、カバー層側からの記録再生で、高密度化が図れ、かつ良好な記録再生特性が得られる追記型光記録媒体を実現できる。また、転写性のよい浅溝基板でも記録再生が容易に行なえる追記型光記録媒体、および、記録再生波長の変動に対し、記録再生特性の変化が少ない追記型光記録媒体が実現できる。
また、本発明の請求項５および請求項６の追記型光記録媒体の層構成と有機化合物の規定によって、従来の追記型光記録媒体の記録層に要求される光学定数と同程度の光学定数が得ることが困難な青色レーザ波長以下の領域であっても、カバー層側からの記録再生で、高密度化が図れ、かつ良好な記録再生特性が得られる追記型光記録媒体を実現できる。また、転写性のよい浅溝基板でも記録再生が容易に行なえる追記型光記録媒体、および、記録再生波長の変動に対し、記録再生特性の変化が少ない追記型光記録媒体が実現できる。
また、本発明の請求項７乃至１１の記録再生波長と光吸収機能と光反射機能を兼用する層として用いる材料の規定によって、請求項１〜６の追記型光記録媒体の記録再生特性を向上させることが可能となる。
また、本発明の請求項１２および請求項１３の光記録媒体の記録方法によって、従来の追記型光記録媒体の記録層に要求される光学定数と同程度の光学定数が得ることが困難な青色レーザ波長以下の領域であっても、基板側からの記録再生で、高密度化が図れ、かつ良好な記録再生特性が得られる追記型光記録媒体の記録方法（記録原理）が実現できる。また、転写性のよい浅溝基板でも記録再生が容易に行なえる追記型光記録媒体の記録方法が実現できる。
また、本発明の請求項１４および請求項１５の光記録媒体の記録方法によって、従来の追記型光記録媒体の記録層に要求される光学定数と同程度の光学定数が得ることが困難な青色レーザ波長以下の領域であっても、カバー層側からの記録再生で、高密度化が図れ、かつ良好な記録再生特性が得られる追記型光記録媒体の記録方法（記録原理）が実現できる。 また、転写性のよい浅溝基板でも記録再生が容易に行なえる追記型光記録媒体の記録方法が実現できる。
【図面の簡単な説明】
【図１】従来の光記録媒体の層構成を説明するための図である。
【図２】本発明の光記録媒体の層構成を説明するための図である。
【図３】本発明の光記録媒体の別の層構成を説明するための図である。
【図４】従来の光記録媒体の記録原理を説明するための図である。
【図５】本発明の光記録媒体の記録原理を説明するための図である。
【図６】本発明の光記録媒体に用いられる有機化合物の特性を説明するための図である。
【図７】本発明の光記録媒体に用いられる有機化合物の特性を説明するための図である。
【図８】実施例１での変調度（ＭＡ）の計算結果を示す図である。
【図９】実施例１での反射率（Ｒ）の計算結果を示す図である。
【図１０】実施例１での変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１１】実施例２での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１２】実施例３での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１３】実施例４での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１４】実施例５での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１５】実施例６での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１６】実施例７での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１７】実施例８での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１８】実施例９での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図１９】実施例１０での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２０】実施例１１での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２１】実施例１２での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２２】実施例１３での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２３】実施例１４での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２４】実施例１５での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２５】実施例１６での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２６】実施例１７での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２７】実施例１８での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２８】実施例１９での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図２９】実施例２０での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３０】実施例２１での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３１】実施例２２での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３２】実施例２３での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３３】実施例２４での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３４】実施例２５での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３５】実施例２６での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３６】実施例２７での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３７】実施例２８での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３８】実施例２９での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図３９】実施例３０での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図４０】実施例３１での変調度（ＭＡ）、反射率（Ｒ）、および変調度×反射率（ＭＡ×Ｒ）の計算結果を示す図である。
【図４１】実施例３２で用いた色素の記録前後のスペクトル変化を示す図である。
【図４２】従来の記録再生波長領域での複素屈折率を示す図である。
【図４３】本発明の記録再生波長領域での複素屈折率を示す図である。
【図４４】本発明で用いるＳｉの複素屈折率を示す図である。
【符号の説明】
１ 基板
２ 有機化合物層
３ 光吸収機能と光反射機能を兼用する層
４ カバー層
５ 反射層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a write once (WORM: Write Once Read Many) optical recording medium and an optical recording method thereof, and more particularly to a write once optical recording medium capable of high density recording even in a blue laser wavelength region and an optical recording method thereof. About.
[0002]
[Prior art]
The development of a blue laser capable of ultra-high density recording is progressing rapidly, and a write-once type optical recording medium corresponding to that is being developed.
In a conventional write-once type optical recording medium, a recording pit is formed by irradiating a recording layer made of an organic compound with a laser beam and causing a refractive index change mainly due to decomposition and alteration of the organic compound. It is an important factor for forming recording pits with good optical constants and decomposition behavior of organic compounds used in the above.
Therefore, it is necessary to select an appropriate organic compound used for the recording layer in terms of optical properties and decomposition behavior with respect to the blue laser wavelength.
[0003]
In other words, the recording / reproducing wavelength has a large absorption band in order to increase the reflectivity when not recorded, and to decompose the organic compound by laser irradiation and cause a large change in the refractive index (this provides a large degree of modulation). It is selected so as to be located at the bottom of the long wavelength side.
This is because the tail on the long wavelength side of the large absorption band is a wavelength region having an appropriate absorption coefficient and a large refractive index.
[0004]
However, no material has been found that has a conventional optical property with respect to the blue laser wavelength.
In order to have an organic compound absorption band near the blue laser wavelength, it is necessary to reduce the molecular skeleton or shorten the conjugated system. This reduces the absorption coefficient, that is, the refractive index. This is to invite.
That is, there are many organic compounds having an absorption band near the blue laser wavelength, and the absorption coefficient can be controlled. However, since there is no large refractive index, a large degree of modulation cannot be obtained.
[0005]
Examples of organic compounds compatible with blue laser include those described in Patent Documents 1 to 5.
However, in these publications, only the spectra of the solution and the thin film are measured in the examples, and there is no description regarding recording and reproduction.
[0006]
In Patent Documents 6 to 8, although there is a description of recording in the examples, the recording wavelength is 488 (nm), and there is no description regarding recording conditions and recording density, and a description that good recording pits can be formed. There is only there.
[0007]
In Patent Document 9, although there is a description of recording in the examples, the recording wavelength is 430 (nm), and there is no description regarding recording conditions and recording density, and there is a description that a good degree of modulation was obtained. Only.
[0008]
In Patent Documents 10 to 19, there is an example of recording with a recording wavelength of 430 (nm) and NA = 0.65 in the embodiment, but the low recording density condition (the same as DVD) where the shortest pit is 0.4 (μm). Recording density).
[0009]
In Patent Document 20, the recording / reproducing wavelength is 405 to 408 (nm), but there is no specific description regarding the recording density, and a low recording density condition of recording a 14T-EFM signal.
[0010]
Further, the following technologies are disclosed regarding the layer configuration and recording method different from those of conventional CD and DVD optical recording media.
Patent Document 21 proposes a technique of recording by changing the extinction coefficient (absorption coefficient in the present invention) of a saturable absorbing dye in a configuration of substrate / saturable absorbing dye-containing layer / reflective layer.
Patent Document 22 proposes a technique for recording by changing the color or deformation of a metal vapor deposition layer by heat generated by the light absorption layer in a configuration of substrate / metal vapor deposition layer / light absorption layer / protective sheet. .
Patent Document 23 proposes a technique of recording by changing the film thickness of the recording layer and changing the depth of the groove in the structure of substrate / dielectric layer / recording layer including light absorber / reflective layer. Yes.
Patent Document 24 proposes a technique of performing recording by changing the film thickness of the recording layer by 10 to 30% in the configuration of substrate / recording layer including light absorber / metal reflective layer.
In Patent Document 25, there is a technique for performing recording by increasing the groove width of the substrate by 20 to 40% with respect to the unrecorded portion in the configuration of substrate / recording layer containing organic dye / metal reflective layer / protective layer. Proposed.
Patent Document 26 proposes a technique for recording by forming a bubble by deforming a metal thin film with a structure of substrate / intermediate layer / metal thin film.
In Patent Document 27, the substrate / light absorption layer / recording auxiliary layer / light reflecting layer is configured to deform the recording auxiliary layer into a concave shape and to deform the light reflecting layer into a concave shape along with the deformation of the recording auxiliary layer. A technique for recording data in the Internet has been proposed.
In Patent Document 28, a substrate / light absorbing layer / porous recording auxiliary layer / light reflecting layer or a substrate / porous recording auxiliary layer / light absorbing layer / light reflecting layer is used, and the recording auxiliary layer is formed in a concave shape. A technique has been proposed in which recording is performed by deforming the light reflecting layer into a concave shape along with deformation of the recording auxiliary layer.
In Patent Document 29, the structure of substrate / porous light absorption layer / light reflection layer is used to deform the light absorption layer into a concave shape and to deform the light reflection layer into a concave shape along with the deformation of the light absorption layer. Techniques for recording have been proposed.
In Patent Document 30, recording is performed by shifting the absorption spectrum of an organic dye to the short wavelength side in a configuration of a substrate / a recording layer containing an organic dye / a recording auxiliary layer, in which the recording auxiliary layer and the organic dye are compatible. Techniques to perform have been proposed.
Patent Document 31 proposes a technique in which recording is performed by forming bumps on the substrate and the composite functional layer in a structure in which a composite functional layer having the functions of a reflective layer and a recording layer and a protective layer are sequentially formed on the substrate. ing. In addition, as a composite functional layer, there exists a prescription | regulation with metals, such as nickel, chromium, titanium, or those alloys.
[0011]
In Patent Document 32, a metal thin film layer, a deformable buffer layer, a reflective layer, and a protective layer are sequentially formed on a substrate, and the substrate and the metal thin film layer are deformed at the same time. There has been proposed a technique for recording by reducing the thickness. Note that the metal thin film layer has a definition of a metal such as nickel, chromium, titanium, or an alloy thereof. Further, as the buffer layer, there is a description that a resin that is easily deformable and has an appropriate fluidity is used, and a pigment may be contained in order to promote the deformation.
[0012]
In Patent Document 33, a metal thin film layer, a buffer layer, and a reflective layer are sequentially stacked on a substrate, and the substrate and the metal thin film layer are deformed, and at the same time, the buffer layer thickness and the optical constant are changed at the deformed portion. A technique has been proposed in which recording is performed. In addition, as a metal thin film layer, there exists a description that metals, such as nickel, chromium, titanium, or those alloys are preferable. The buffer layer is made of a mixture of a dye and an organic polymer, and a dye having a large absorption band near the recording / reproducing wavelength is used.
[0013]
In Patent Document 34, a metal recording layer, a buffer layer, and a reflective layer are sequentially stacked on a substrate, and the substrate and the metal recording layer are deformed, and at the same time, the buffer layer thickness and the optical constant are changed at the deformed portion. By doing so, a technique for recording is provided. There is a description that the metal recording layer is preferably a metal such as nickel, chromium, titanium, or an alloy thereof. The buffer layer is made of a mixture of a dye and a resin, and a dye having a large absorption band near the recording / reproducing wavelength is used.
[0014]
As described above, the above technique is not aimed at realizing an optical recording medium in the blue laser wavelength region, and is not a layer configuration or a recording method effective in the blue laser wavelength region.
In particular, in the vicinity of 405 (nm), which is the center of the oscillation wavelength of a blue semiconductor laser currently in practical use, it has an optical constant comparable to that required for the recording layer of a conventional write-once type optical recording medium. There are almost no organic compounds.
Further, there is no example in which recording conditions are clarified in the vicinity of 405 (nm) and recording is performed at a higher recording density than DVD.
Furthermore, many of the embodiments in the above publication are experiments with a conventional disk configuration (see FIG. 1), and a configuration different from the conventional disk configuration (see FIG. 1) has been proposed. The dyes used are required to have the same optical characteristics and functions as in the past, and an effective proposal for the layer structure, recording principle, and recording method that easily realizes a write once optical recording medium made of an organic compound in the blue laser wavelength region. There is no.
[0015]
Further, in a write-once optical recording medium using a conventional organic compound, a large refractive index and a relatively small absorption coefficient (0.05 to 0.07) with respect to the recording / reproducing wavelength from the viewpoint of securing the degree of modulation and reflectance. Only organic compounds with a degree) can be used.
That is, since the organic compound does not have a large absorption capacity for the recording light, it is impossible to reduce the film thickness of the organic compound, and thus it is necessary to use a substrate having a deep groove ( Since organic compounds are usually formed by spin coating, the organic compound was buried in deep grooves to increase the film thickness).
Therefore, it becomes very difficult to form a substrate having a deep groove, which has been a factor of deteriorating the quality as an optical information recording medium.
[0016]
Further, in a write once optical recording medium using a conventional organic compound, the main absorption band of the organic compound exists in the vicinity of the recording / reproducing wavelength, so that the wavelength dependency of the optical constant of the organic compound increases (the optical constant depends on the wavelength). Recording characteristics such as recording sensitivity, modulation degree, jitter and error rate, and reflectivity greatly change with respect to fluctuations in recording / reproducing wavelength due to individual differences of lasers, environmental temperature changes, etc. There was a problem.
[0017]
[Patent Document 1]
JP 2001-181524 A
[Patent Document 2]
JP 2001-158865 A (2nd page, 1st column, 1st line to 17th line)
[Patent Document 3]
JP 2000-343824 A (2nd page, 1st column, 1st line to 32nd line)
[Patent Document 4]
JP 2000-343825 A (2nd page, 1st column, 1st line to 21st line)
[Patent Document 5]
JP-A-2000-335110 (Claim 2 on page 2, column 1, lines 1 to 28)
[Patent Document 6]
JP-A-11-221964 (Claim 2 on page 2, column 1, lines 1 to 30)
[Patent Document 7]
Japanese Patent Laid-Open No. 11-334206 (Claim 2 on page 2, column 1, lines 1 to 30)
[Patent Document 8]
JP 2000-43423 (Claim 2 on page 2, column 1, lines 1 to 44)
[Patent Document 9]
Japanese Patent Laid-Open No. 11-58955 (Claim 2 on page 2, column 1, lines 1 to 26)
[Patent Document 10]
JP-A-2001-39034 (Claims on page 2, column 1, line 1 to page 2, column 3, line 6)
[Patent Document 11]
JP-A-2000-149320 (Claim 2 on page 2, column 1, lines 1 to 41)
[Patent Document 12]
JP-A-2000-113504 (Claim 2 on page 1, column 1, lines 1 to 35)
[Patent Document 13]
Japanese Patent Laid-Open No. 2000-108513 (Claim 2 on page 2, column 1, lines 1 to 26)
[Patent Document 14]
Japanese Patent Laid-Open No. 2000-222772 (Claim 2 on page 2, column 1, lines 1 to 26)
[Patent Document 15]
JP-A-2000-218940 (Claim 2 on page 2, column 1, lines 1 to 43)
[Patent Document 16]
JP 2000-222771 A (2nd page, 1st column, 1st line to 21st line)
[Patent Document 17]
JP 2000-158818 (Claim 2 on page 2, column 1, lines 1 to 27)
[Patent Document 18]
Japanese Patent Laid-Open No. 2000-280621 (Claim 2 on page 2, column 1, lines 1 to 39)
[Patent Document 19]
JP 2000-280620 A (2nd page, 1st column, 1st line to 31st line)
[Patent Document 20]
JP 2001-146074 (Claim 2nd page, first column, first line to page 2, third column, 31st line)
[Patent Document 21]
Japanese Patent Laid-Open No. 7-304258 (Claim 2 on page 2, column 1, lines 1 to 14)
[Patent Document 22]
JP-A-8-83439 (Claim 2 on page 2, column 1, lines 1 to 19)
[Patent Document 23]
JP-A-8-138245 (Claim 2 on page 2, column 1, lines 1 to 25)
[Patent Document 24]
JP-A-8-297838 (Claim 2nd page, column 1, line 1 to line 17)
[Patent Document 25]
JP-A-9-198714 (Claim 2 on page 2, column 1, lines 1 to 40)
[Patent Document 26]
Japanese Patent No. 2506374
[Patent Document 27]
Japanese Patent No. 2591939
[Patent Document 28]
Japanese Patent No. 2591940
[Patent Document 29]
Japanese Patent No. 2591941
[Patent Document 30]
Japanese Patent No. 2998925
[Patent Document 31]
Japanese Patent Laid-Open No. 9-265660 (claims on page 2, column 1, line 1 to column 2, line 31)
[Patent Document 32]
Japanese Patent Laid-Open No. 10-134415 (claims on page 2, column 1, line 1 to column 2, line 44)
[Patent Document 33]
Japanese Patent Laid-Open No. 11-306591 (Claim 2nd page 1st column 1st line to 2nd page 3rd column 23rd line claim)
[Patent Document 34]
Japanese Patent Laid-Open No. 10-124926 (claims on page 2, column 1, line 1 to column 2, line 24)
[0018]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to solve the above problems and to realize a write-once type optical recording medium made of an organic compound even in a region below a blue laser wavelength, particularly in a wavelength region near 405 (nm). Even with shallow groove substrates with good transferability, it is possible to realize write-once optical recording media made of organic compounds, recording characteristics such as recording sensitivity, modulation degree, jitter and error rate, and reflection with respect to fluctuations in recording and reproduction wavelengths. An object is to realize a write-once type optical recording medium with little change in rate and the like.
[0019]
[Means for solving the problems]
The above-described problem is (1) “an organic compound layer having at least a main absorption band at the time of non-recording on the long wavelength side with respect to the recording / reproducing wavelength, a light absorption function and a light reflection function. An optical recording medium having a structure in which layers are sequentially stacked and recording / reproducing is performed from the substrate side ”, (2)“ on the substrate, at least a main absorption band at the time of unrecording corresponds to the recording / reproducing wavelength ” An organic recording layer having a structure in which an organic compound layer existing on the long wavelength side and a layer having both a light absorption function and a light reflection function are sequentially laminated, and recording and reproduction are performed from the substrate side. An optical recording medium characterized by using an organic compound whose absorption coefficient at the recording / reproducing wavelength increases due to heat generated by the light absorption function of the layer having both the light absorption function and the light reflection function as the organic compound constituting , (3) "At least not on the substrate The main absorption band at the time of recording has a structure in which an organic compound layer that exists on the long wavelength side with respect to the recording / reproducing wavelength and a layer that combines the light absorption function and the light reflection function are sequentially laminated, and recording / reproduction is performed from the substrate side. As an organic compound constituting the organic compound layer, a layer having both a light absorption function and a light reflection function is generated by heat generated by the light absorption function of the layer having both a light absorption function and a light reflection function. An optical recording medium characterized by using an organic compound that causes a volume reduction so as to be deformed toward the organic compound layer side ”, (4)“ A layer that combines at least a light absorption function and a light reflection function on the substrate, An optical recording characterized by having a structure in which an organic compound layer having a main absorption band during recording on the long wavelength side with respect to the recording / reproducing wavelength and a cover layer are sequentially laminated, and recording / reproducing is performed from the cover layer side Medium ”, (5)“ On the substrate, At least a layer that has both a light absorption function and a light reflection function, an organic compound layer in which a main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a cover layer are sequentially laminated, An optical recording medium which performs recording / reproduction from the cover layer side, and the organic compound constituting the organic compound layer is heated at a recording / reproducing wavelength by heat generated by the light absorption function of the layer having both the light absorption function and the light reflection function. An optical recording medium characterized by using an organic compound having an increased absorption coefficient ”, (6)“ A layer on which at least a light absorption function and a light reflection function are combined on a substrate, a main absorption band at the time of unrecording is recorded An optical recording medium having a structure in which an organic compound layer and a cover layer which are present on the long wavelength side with respect to a reproduction wavelength are sequentially laminated, and recording and reproduction are performed from the cover layer side. Light absorption function as a compound It is characterized by using an organic compound that causes volume reduction so that the layer that also functions as a light absorbing function and a light reflecting function is deformed to the organic compound layer side due to heat generated by the light absorbing function of the layer that also functions as a light reflecting function. And (7) “(the complex refractive index imaginary part of the layer having both the light absorption function and the light reflecting function)> (the complex refractive index imaginary part of the organic compound layer). The optical recording medium according to any one of items (1) to (6) ”, (8)“ (the complex refractive index real part of a layer having both a light absorption function and a light reflection function)> (organic compound layer) (The complex refractive index real part of the optical recording medium according to any one of items (1) to (6)), (9) “(the organic compound layer after recording) The complex refractive index real part) ≧ (the complex refractive index real part of the organic compound layer before recording). Thru | or the optical recording medium of any one of (6) term | claim, (10) "The recording / reproducing wavelength is 500 nm or less, and the layer which combines a light absorption function and a light reflection function mainly has Si or Ge. The optical recording medium according to any one of (1) to (8) above, wherein the recording / reproducing wavelength is 500 nm or less, and the optical absorption function The optical recording medium in which the layer that also serves as a light reflecting function is mainly composed of Si, and the film thickness of the layer that serves as both a light absorbing function and a light reflecting function is 10 nm or more. The optical recording medium according to any one of items 1) to (8) is achieved.
[0020]
In addition, the above-mentioned problem is (12) “an organic compound layer on which a main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, a light absorption function and a light reflection function. A recording method of an optical recording medium having a structure in which multiple layers are sequentially stacked and recording and reproduction are performed from the substrate side, mainly due to heat generated by the light absorption function of the layer that also functions as a light absorption function and a light reflection function Recording method for optical recording medium, wherein recording is performed by increasing absorption coefficient at recording / reproducing wavelength of organic compound layer ”, (13)“ Main absorption band at least when unrecorded on substrate ” A recording method for an optical recording medium having a structure in which an organic compound layer existing on a long wavelength side with respect to a recording / reproducing wavelength, and a layer having both a light absorption function and a light reflection function are sequentially laminated, and recording / reproducing is performed from the substrate side And mainly light absorption function and light reflection A recording method of an optical recording medium, wherein recording is performed by deforming the layer that also functions as a light absorption function and a light reflection function to the organic compound layer side by heat generated by the light absorption function of the layer that also functions as a function '', (14) “A layer that combines at least a light absorption function and a light reflection function, an organic compound layer in which a main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a cover layer are sequentially laminated on the substrate. A recording method of an optical recording medium having the structure described above, in which recording / reproduction is performed from the cover layer side, mainly due to heat generated by the light absorption function of the layer having both the light absorption function and the light reflection function, Recording method of optical recording medium characterized in that recording is performed by increasing absorption coefficient at recording / reproducing wavelength ”, (15)“ A layer on the substrate having at least a light absorption function and a light reflection function, The main absorption band at the time of recording A recording method for an optical recording medium having a structure in which an organic compound layer and a cover layer which are present on the long wavelength side with respect to the recording / reproducing wavelength are sequentially laminated, and recording / reproducing is performed from the cover layer side. An optical recording medium characterized in that recording is performed by deforming a layer that combines the light absorption function and the light reflection function to the organic compound layer side by heat generated by the light absorption function of the layer that combines the function and the light reflection function. This is achieved by the “recording method”.
[0021]
That is, the item (1) is a substrate even in a region of a blue laser wavelength or less where it is difficult to obtain an optical constant equivalent to the optical constant required for the recording layer of a conventional write once optical recording medium. Provides a layer structure of a write-once optical recording medium that can achieve high recording density and good recording / reproducing characteristics by recording / reproducing from the side, and can be easily recorded / reproduced even on a shallow groove substrate with good transferability. The layer structure of a write-once optical recording medium is provided, and the layer structure of the write-once optical recording medium with little change in recording / reproducing characteristics with respect to fluctuations in recording / reproducing wavelength is provided.
Further, the items (2) and (3) are regions of a blue laser wavelength or less where it is difficult to obtain an optical constant equivalent to the optical constant required for the recording layer of a conventional write once optical recording medium. Even so, it provides a layer structure of a write-once optical recording medium that can achieve high recording density and good recording / reproducing characteristics by recording / reproducing from the substrate side, and a recording method (recording principle). Provides the layer structure and recording principle of a write-once optical recording medium that can be easily recorded / reproduced even on a shallow groove substrate with good transferability. A layer structure of an optical recording medium and a recording principle are provided.
Further, the above item (4) covers the area below the blue laser wavelength where it is difficult to obtain an optical constant comparable to that required for the recording layer of a conventional write-once optical recording medium. Provides a layer structure of a write-once optical recording medium that can achieve high recording density and good recording / reproducing characteristics by recording / reproducing from the layer side, and can be easily recorded / reproduced even on a shallow groove substrate with good transferability The present invention provides a layer structure of a write-once optical recording medium that can be performed, and further provides a layer structure of a write-once optical recording medium with little change in recording / reproduction characteristics with respect to fluctuations in recording / reproduction wavelength.
Further, the items (5) and (6) are regions below the blue laser wavelength where it is difficult to obtain an optical constant comparable to that required for the recording layer of a conventional write-once optical recording medium. Even so, it is possible to provide a layer structure and a recording method (recording principle) of a write-once optical recording medium that can achieve high recording density and good recording and reproduction characteristics by recording and reproduction from the cover layer side. Provides a layer structure and recording principle of a write-once optical recording medium that can be easily recorded / reproduced even on a shallow groove substrate with good transferability, and additionally has little change in recording / reproduction characteristics with respect to fluctuations in recording / reproduction wavelength The layer structure of a recording optical recording medium and the recording principle are provided.
Further, in order to solve the problems of the items (1) to (6), the items (7) to (11) are layers that combine a recording / reproducing wavelength, a light absorption function, and a light reflection function, Alternatively, the material used for the organic compound layer is defined.
[0022]
Further, the items (12) and (13) are regions of a blue laser wavelength or less in which it is difficult to obtain an optical constant equivalent to the optical constant required for the recording layer of the conventional write once optical recording medium. Even so, it provides a recording method (recording principle) for a write-once optical recording medium that can achieve high recording density and good recording / reproducing characteristics by recording / reproducing from the substrate side, and has good transferability. It is an object of the present invention to provide a recording method for a write-once optical recording medium that can be easily recorded and reproduced even on a shallow groove substrate.
Further, the items (14) and (15) are regions below the blue laser wavelength in which it is difficult to obtain an optical constant equivalent to the optical constant required for the recording layer of the conventional write once optical recording medium. Even so, it provides a recording method (recording principle) for a write-once optical recording medium that can achieve high recording density and good recording / reproduction characteristics by recording / reproduction from the cover layer side, and also provides transferability. It is an object of the present invention to provide a recording method for a write-once optical recording medium that can be easily recorded and reproduced even with a good shallow groove substrate.
[0023]
In order to solve the above problems, in the present invention, an organic compound layer in which at least a main absorption band at the time of non-recording exists on the long wavelength side with respect to a recording / reproducing wavelength, and a light absorption function and a light reflection function are combined An optical recording medium having a structure in which layers are sequentially stacked and recording / reproducing is performed from the substrate side, or a layer on the substrate that has at least both a light absorption function and a light reflection function, There is provided an optical recording medium having a structure in which an organic compound layer having an absorption band on a long wavelength side with respect to a recording / reproducing wavelength and a cover layer are sequentially laminated, and recording / reproducing is performed from the cover layer side. The
[0024]
Further, for these optical recording media, the absorption coefficient at the recording / reproducing wavelength of the organic compound layer is increased mainly by the heat generated by the light absorption function of the layer having both the light absorption function and the light reflection function, and / or The recording is performed mainly by deforming the layer that combines the light absorption function and the light reflection function to the organic compound layer side by the heat generated by the light absorption function of the layer that combines the light absorption function and the light reflection function. A recording method for an optical recording medium is provided.
[0025]
In the present invention, one of the basic principles of recording is to decompose the organic compound in the organic compound layer and increase the absorption on the shorter wavelength side than the main absorption band by the heat generation of the layer having both the light absorption function and the light reflection function. It is. The basic recording principle will be described below.
The optical recording medium of the present invention is an organic compound layer composed of an organic compound that has conventionally functioned as a light absorbing layer and a recording layer due to a change in refractive index (real part of complex refractive index) caused by decomposition and alteration. The light absorption function and the recording function were separated.
That is, from the organic compound layer, except for the light absorption function (in the sense of reducing the proportion of the entire optical recording medium in the light absorption function, it is not limited to eliminating the light absorption function of the organic material layer), A structure is provided in which a layer having both a light absorption function and a light reflection function is provided adjacent to the organic compound layer.
In addition, the light absorption layer is made of a material having a large difference in refractive index from the organic compound layer and having a large absorption coefficient, and also functions as a light reflection layer (referred to as a layer having both a light absorption function and a light reflection function). This is why)
[0026]
In a conventional write-once optical recording medium, the absorption coefficient at the recording / reproducing wavelength is lowered by the decomposition and alteration of the organic compound, and the degree of modulation is generated by utilizing a large change in the refractive index (see FIG. 4). Indicates recording / reproducing wavelength).
However, in the write-once optical recording medium of the present invention, the decomposition and alteration of the organic compound cause the absorption of the molecules and molecular groups constituting the organic compound (the absorption coefficient on the short wavelength side of the large absorption band is increased). increase).
That is, the absorption coefficient at the recording / reproducing wavelength is increased, thereby generating the degree of modulation (see FIG. 5).
Therefore, the organic compound layer has no refractive index limitation, and the organic compound layer does not need to have a light absorption capability with respect to the recording / reproducing wavelength.
[0027]
Here, the principle of increasing the absorption coefficient at the recording / reproducing wavelength will be described in more detail.
The organic compound used in the present invention is an organic compound in which a small molecule or molecular group is bonded, or a complex or aggregate is formed to form a large conjugated system, which is inherent to the molecule or molecular group. An absorption spectrum having a large absorption band on the longer wavelength side than the absorption wavelength (corresponding to absorption spectra A and B in FIG. 6), and extinguishing or attenuating the intrinsic absorption bands of individual molecules and molecular groups. (Corresponding to the absorption spectrum C in FIG. 7).
[0028]
For such an organic compound, λ as shown in FIG. ₁ Is selected as the recording / playback wavelength. ₁ In the state where the absorption was low, the intrinsic absorption of molecules and molecular groups that had formed large molecules increased due to decomposition and alteration (see FIG. 6). ₁ As a result, the recording area can be formed by changing the absorption coefficient.
Therefore, a molecule that is merely bonded to a small molecule or molecular group and does not form a conjugated system is in the state shown in FIG. 7, that is, the intrinsic absorption band that the molecule or molecular group has. Since a state where a large sharp absorption band is formed is not realized because of disappearance or attenuation, a change in absorption coefficient before and after recording does not increase, and a recording pit cannot be formed.
The conjugated system is a general term for molecules or free radicals in which multiple bonds are not localized and some structures resonate, and is due to non-localization of π electrons. A typical example is a group having a double bond with a single bond sandwiched between them such as = CH-CH = CH-).
Note that an unpaired electron or a lone electron may participate in resonance instead of the double bond.
The only requirement for an organic compound is that it is surely decomposed by irradiation with laser light and its decomposition characteristics (decomposition temperature or intensity, decomposition speed, amount of decomposition, etc.) are excellent.
This recording principle does not mainly use the change in refractive index (real part of complex refractive index), which is the conventional recording principle, but mainly uses an increase in absorption coefficient (imaginary part of complex refractive index). There are no strict restrictions as in the past.
In the present invention, in addition to the recording principle described above, the layer that combines the light absorption function and the light reflection function is deformed to the organic compound layer side by the heat generated by the light absorption function of the layer that combines the light absorption function and the light reflection function. Is the basic principle of recording. The basic recording principle will be described below.
[0029]
The optical recording medium of the present invention is an organic compound layer composed of an organic compound that has conventionally functioned as a light absorbing layer and a recording layer due to a change in refractive index (real part of complex refractive index) caused by decomposition and alteration. The light absorption function and the recording function were separated.
That is, the organic compound layer has a structure in which the light absorption function is excluded and a layer that combines the light absorption function and the light reflection function is provided adjacent to the organic compound layer.
In a conventional write-once optical recording medium, the absorption coefficient at the recording / reproducing wavelength is lowered by the decomposition and alteration of the organic compound, and the degree of modulation is generated by utilizing a large change in the refractive index (see FIG. 4). Indicates recording / reproducing wavelength).
However, in the write-once type optical recording medium of the present invention, the layer that combines the light absorption function and the light reflection function is expanded and deformed by the heat generation of the layer that combines the light absorption function and the light reflection function, so that the light absorption function and the light reflection function are achieved. The layer that also functions is deformed to the organic compound layer side.
Alternatively, the heat absorption function and the light can be reduced by changing the aggregation state of the organic compound (for example, decomposition and alteration) by the heat generation of the layer that combines the light absorption function and the light reflection function, thereby causing the volume of the organic compound layer to decrease. The layer that also serves as a reflection function is deformed to the organic compound layer side.
In this way, a signal having a recording polarity of High to Low can be easily obtained by deforming the layer having both the light absorption function and the light reflection function to the organic compound layer side (however, in the present invention, the recording polarity is It is not limited to High to Low).
That is, in this recording principle, in order not to actively use the optical constant change of the organic compound layer, but to utilize the volume change of the organic compound layer and the expansion deformation of the layer that combines the light absorption function and the light reflection function, The organic compound layer does not have a strict limit on the refractive index, and the organic compound layer does not need to have a light absorption capability with respect to the recording / reproducing wavelength.
[0030]
Therefore, the recording principle of the present invention has a large absorption band in the red laser wavelength region as the organic compound layer, regardless of which basic principle is used, despite the fact that recording and reproduction are performed in the blue region, and A material that does not have a large absorption band in the blue laser wavelength region and has excellent decomposition characteristics, such as a dye for CD-R or DVD-R, can be used.
Conventionally, it has been necessary to use a complex substituent or a dye having high synthesis difficulty as a recording layer for wavelength control. However, the organic compound layer of the present invention does not allow such complicated wavelength control. Since it is necessary, it is possible to select an organic compound at a low cost.
[0031]
Further, in the conventional optical recording medium, since the organic compound has both the recording layer and the light absorption function, it is essential for the organic compound to have a large refractive index n and a relatively small absorption coefficient k with respect to the recording / reproducing wavelength. Therefore, in order to reach the temperature at which the organic compound is decomposed, a relatively thick film thickness is necessary (and the groove depth of the substrate is very deep with respect to the phase change type optical recording medium). )
However, in the recording medium of the present invention, since the light absorption function and the recording function are separated, the film thickness of the organic compound layer can be made thinner than before.
Since the organic compound layer can be made thin, it is possible to use a substrate having a shallow groove depth with excellent transferability (moldability), and the signal quality of the optical recording medium is greatly improved.
[0032]
Furthermore, since the layer having both the light absorption function and the light reflection function in the present invention can use a material whose refractive index shows normal dispersion, the organic compound layer has a larger absorption band than the recording / reproducing wavelength. Because organic compounds such as dyes that exist on the long wavelength side are used (in the vicinity of a large absorption band, the refractive index exhibits anomalous dispersion and the refractive index varies greatly depending on the wavelength, but is sufficiently distant from the large absorption band. In the wavelength region, the refractive index shows normal dispersion, and the refractive index shows a gradual change with respect to the wavelength), and the recording sensitivity and modulation factor against recording / reproducing wavelength fluctuations due to individual differences in the laser and changes in the environmental temperature. In addition, the conventional problem that the recording characteristics such as the jitter and the error rate, the reflectance, and the like change greatly can be solved.
[0033]
In the present invention, the absorption coefficient at the recording / reproducing wavelength of the organic compound layer is mainly increased by the heat generated by the light absorption function of the layer having both the light absorption function and the light reflection function, and / or the light absorption function. Recording is performed by changing the layer that also functions as a light absorption function and a light reflection function to the organic compound layer side by heat generated by the light absorption function of the layer that also functions as a light reflection function. Physical deformation of a layer other than the layer also serving as a light reflection function (hereinafter referred to as another layer, for example, the substrate corresponds to the other layer) can also be used.
However, in this case, recording by deformation of the other layer is performed by recording polarity due to an increase in absorption coefficient due to decomposition of the organic compound (indicates whether the reproduction signal decreases or increases due to recording), light absorption function and light reflection. It is preferable to make the recording polarity the same as that due to the deformation of the layer that also functions as an organic compound layer.
The recording polarity due to the deformation of the other layer can be controlled by the groove shape of the substrate, the deformation direction of the other layer, the film thickness of the other layer, the optical constant of the other layer, and the like.
[0034]
In the present invention, recording is performed by the light absorption function of the layer that combines the light absorption function and the light reflection function, but this is only recorded by the light absorption function of the layer that combines the light absorption function and the light reflection function. This means that the recording principle that the organic compound is decomposed and altered by the light absorption function in the organic compound layer as before is not denied or excluded.
However, in the present invention, the absorption coefficient (imaginary part of the complex refractive index) of the unrecorded organic compound layer at the recording / reproducing wavelength can be lowered in order to improve the reflectance and the modulation degree when not recorded. preferable.
This is because molecules and molecular groups having absorption below the blue region basically have a small molecular skeleton, and both the real and imaginary parts of the complex refractive index are small. For example, the reproduction wavelength when not recorded (unrecorded region) This is because the increase ratio of the absorption coefficient due to recording is likely to be relatively small when the absorption at is high.
[0035]
Therefore, in order to improve the reflectance and the modulation degree when not recorded, it is preferable to reduce the absorption coefficient when the organic compound layer is unrecorded at the recording / reproducing wavelength. Or the like cannot be sufficiently generated by the light absorption function of the organic compound itself.
Therefore, in the present invention, in order to cause decomposition / degeneration of the organic compound that causes an increase in the absorption coefficient at the reproduction wavelength, a layer that combines the light absorption function and the light reflection function is provided separately from the organic compound layer.
[0036]
That is, in the present invention, it is necessary to lower the absorption coefficient of the organic compound layer at the recording / reproducing wavelength and to increase the absorption coefficient of the layer having both the light absorption function and the light reflection function. Specifically, it is preferable that (the complex refractive index imaginary part of the layer having both the light absorption function and the light reflecting function)> (the complex refractive index imaginary part of the organic compound layer).
Further, in order to increase the reflectance when not recorded and improve the reproduction signal quality, it is preferable to increase the difference in refractive index between the organic compound layer and the layer that combines the light absorption function and the light reflection function.
In this case, the refractive index of the layer having both the light absorption function and the light reflection function may be larger or smaller than the refractive index of the organic compound.
However, in general, in the present invention, since the refractive index of the layer that combines the light absorption function and the light reflection function is sufficiently smaller than the refractive index of the organic compound, many materials have high thermal conductivity. It is preferable that the complex refractive index real part of the layer having both the absorption function and the light reflection function> (the complex refractive index real part of the organic compound layer).
[0037]
In the present invention, the recording / reproducing wavelength is preferably 500 nm or less. This is due to the following reasons.
(1) In the wavelength region of 500 nm or more (for example, if the recording / reproducing wavelength is near 400 nm, the main absorption band of the dye needs to be positioned on the longer wavelength side than 400 nm), the molecular skeleton becomes large, so the decomposition characteristics There are many excellent materials. Therefore, when an organic compound having a main absorption band or a maximum absorption wavelength at 500 nm or more is used, a recording / reproducing wavelength of 500 nm or less is suitable from the recording principle of the present invention.
(2) The absorption wavelength of molecules and molecular groups generated by the decomposition of the dye should be approximately 500 nm or less.
(3) The absorption coefficient (and refractive index) of a layer having both a light absorption function and a light reflection function, such as Si, Ge, or SiC, decreases as the wavelength increases (in the red laser wavelength region, the light absorption layer or Si and Ge do not function sufficiently as a light reflecting layer).
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Specifically explaining the constituent elements, the optical recording medium of the present invention is basically composed of a substrate, an organic compound layer in which the main absorption band at the time of unrecording is on the long wavelength side with respect to the recording / reproducing wavelength, and a light absorption function And a layer that also serves as a light reflecting function, an undercoat layer, an overcoat layer, an intermediate layer, a protective layer, and the like may be further provided as necessary.
As the material of the substrate in the optical recording medium of the present invention, basically, when recording / reproduction is performed from the substrate side, it is preferably transparent at the wavelength of the recording light and the reproduction light, and recording / reproduction without passing through the substrate. In the case of the above, it is not necessary to be transparent at the wavelength of the recording light and the reproducing light. The substrate may have guide grooves and pits for recording / reproducing light.
There are no particular restrictions on the material of the substrate as long as it has excellent thermal and mechanical properties, and has excellent light transmission properties when recording / reproducing is performed from the substrate side (through the substrate). .
[0039]
Examples of such materials include acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like, and glass materials. A glass having a resin layer made of a radiation curable resin such as a photocurable resin can be used.
From the viewpoints of high productivity, cost, moisture absorption resistance, etc., injection molded polycarbonate is preferred.
Amorphous polyolefin is preferred from the standpoint of chemical resistance and moisture absorption resistance.
Moreover, a glass substrate is preferable from the viewpoint of high-speed response.
The thickness of the substrate varies depending on the application and is not particularly limited.
[0040]
In the present invention, by using a layer having both a light absorption function and a light reflection function, an organic compound is decomposed (for example, a methine chain that is a conjugated system connecting molecules and molecular groups is cleaved) to absorb at a recording / reproducing wavelength. Can be increased.
In order for the layer having both the light absorption function and the light reflection function to function as the light absorption layer, it is preferable that the thermal conductivity is relatively low compared to a metal material such as Ag or Au (even if it is a metal compared to Ag or Au or the like). Metals with low thermal conductivity can be used in the present invention and do not deny metallic materials).
A relatively low thermal conductivity compared to metal materials such as Ag and Au is also necessary for efficiently decomposing organic compounds (with low recording power).
Further, in order to cause decomposition of the organic compound with a low recording power, it is preferable to use a layer having a light absorption function and a light reflection function, both having a large absorption coefficient with respect to the recording wavelength.
That is, the absorption coefficient (imaginary part of the complex refractive index) of the layer having both the light absorption function and the light reflection function is preferably sufficiently larger than the absorption coefficient of the organic compound layer, and the absorption coefficient is preferably 0.3 or more. Further preferred.
Further, in order to increase the reflectivity and improve the quality of the recording / reproducing signal, the layer having both the light absorption function and the light reflection function preferably functions as a light reflection layer.
For this reason, the refractive index of the layer having both the light absorption function and the light reflection function is preferably different from the refractive index of the organic compound layer, and more preferably has a refractive index difference of 1.0 or more.
In this case, the refractive index of the layer having both the light absorption function and the light reflection function may be larger or smaller than the refractive index of the organic compound layer.
In the present invention, a layer made of a material satisfying the physical property conditions of thermal conductivity, refractive index (real part of complex refractive index), and absorption coefficient (imaginary part of complex refractive index) is used in the present invention. And a layer that combines the light-reflecting function (if the above physical properties are satisfied even if the light-absorbing function and the light-reflecting function are not considered, it is determined that the layer has both the light-absorbing and light-reflecting functions ).
In view of the above points, SiC, B are used as a layer having both a light absorption function and a light reflection function. ₄ Carbide-based non-oxides such as C, TiC, WC, carbon-based non-oxides such as amorphous carbon, graphite, diamond, ceramics represented by ferrite, or Te-TeO ₂ , Te-TeO ₂ -Pd, Sb ₂ Se ₃ / Bi ₂ Te ₃ , Ge-Te-Sb-S, Te-TeO ₂ -Ge-Sn, Te-Ge-Sn-Au, Ge-Te-Sn, Sn-Se-Te, Sb-Se-Te, Sb-Se, Ga-Se-Te, Ga-Se-Te-Ge, In -Se, In-Se-Tl-Co, Ge-Sb-Te, In-Se-Te, Ag-In-Sb-Te, Ag-Zn, Cu-Al-Ni, In-Sb, In-Sb-Se , In-Sb-Te, phase change recording materials, pure metals such as nickel, chromium, titanium, tantalum, etc., alloys such as copper / aluminum, nickel / iron, semimetals such as silicon, semiconductors such as Ge, etc. It is possible. Alternatively, a material containing Si or Ge (eg, Si, Ge, SixGe1-x, Mg ₂ Ge, Mg ₂ Si, SiC, etc.); metals such as Nb, Ta, Be, V, or metal oxides thereof (for example, Ta ₂ O ₅ , Nb ₂ O ₅ Etc.) Semiconductors such as AlSb, AlxGa1-xAs, CdSe, GaSb, Hg1-xCdxTe, Se, Te, ZnTe, ZnS, PbS, InP, and GaP can be preferably used.
Among them, it is preferable to use Si or Ge, or a mixture thereof as a layer having both the light absorption function and the light reflection function.
[0041]
As a material used for the organic compound layer, for example, a dye is preferable.
Examples of dyes include polymethine dyes, naphthalocyanine, phthalocyanine, squarylium, croconium, pyrylium, naphthoquinone, anthraquinone (indanthrene), xanthene, triphenylmethane, azulene, tetrahydrocholine, phenanthrene And triphenothiazine dyes and metal complex compounds.
For example, a cyanine dye, which is known to have a decomposition behavior in which a methine chain that binds left and right heterocycles is cleaved by heat and tarred, and left and right heterocycles remain, general formula (1) is an example of a dye suitable for the present invention. It is.
[0042]
[Chemical 1]

(In the formula, X and Y represent organic substituents such as alkyl and aryl, Z represents an anion, and n represents a positive number.)
[0043]
However, among the above cyanine dyes, cyanine dyes having n of 2 or 3 are preferable as dyes having particularly good decomposition characteristics.
For cyanine dyes where n is 2 or 3, when the wavelength below the blue laser wavelength region becomes the recording / reproducing wavelength, the reflectance at the recording / reproducing wavelength can be improved, and the main absorption band can be moved away from the recording / reproducing wavelength. This is because the wavelength dependence of the optical constant of the dye can be greatly improved. However, in the present invention, the value of n is not limited to 2 or 3.
[0044]
Further, the left and right heterocycles in the general formula (1) are preferably molecules / molecular groups having an absorption peak at 300 nm or more alone. More specifically, in order to increase a large absorption coefficient by recording in the blue laser wavelength region, in the general formula (1), at least one of the left and right heterocycles is tricyclic or more. It is preferable that it is a polycyclic fused ring.
Thereby, an increase in the absorption coefficient during decomposition can be detected largely in the blue region.
[0045]
The dye layer can be formed by ordinary means such as vapor deposition, sputtering, CVD or solvent coating. When using the coating method, the above-mentioned dye or the like can be dissolved in an organic solvent, and a conventional coating method such as spraying, roller coating, dipping or spin coating can be used.
The spin coating method is preferable from the viewpoint of mass productivity and cost.
Further, from the viewpoint that a recording layer having a uniform thickness can be obtained, the vacuum deposition method or the like is preferable to the coating method.
In the case of film formation by the spin coating method, the rotation speed is preferably 500 to 15000 rpm, and after spin coating, a treatment such as heating or solvent vapor may be performed in some cases.
The coating solvent for forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method, or a dipping method may be any solvent that does not attack the substrate and is not particularly limited.
[0046]
As the organic solvent to be used, alcohols such as diacetone alcohol, methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone and 3-hydroxy-3-methyl-2-butanone, N, N-dimethylacetamide Amides such as N, N-dimethylformamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, diethyl ether and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, methyl lactate and ethyl lactate Hydroxy carboxylic acid solvents such as methyl isobutyrate, aliphatic halogenated carbons such as chloroform, methylene chloride, dichloroethane, carbon tetrachloride, trichloroethane, Perfluoroalkyl alcohol solvents such as fluoropropanol, octafluoropentanol, hexafluorobutanol, etc., aromatics such as benzene, xylene, monochlorobenzene, dichlorobenzene, or cellsolves such as methoxyethanol, ethoxyethanol, hexane, pentane , Hydrocarbons such as cyclohexane and methylcyclohexane.
The film thickness of the dye layer is 100 to 10 μm, preferably 100 to 2000 μm.
[0047]
In addition, the organic compound layer has a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone as a singlet oxygen quencher to improve stability and light resistance of the organic compound. Etc.) and a recording sensitivity improver such as a metal compound may be contained for improving the recording sensitivity.
[0048]
Here, the metal compound refers to a compound in which a metal such as a transition metal is included in the compound in the form of atoms, ions, clusters, etc., for example, ethylenediamine complex, azomethine complex, phenylhydroxyamine complex, phenanthroline complex. Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex, and porphyrin complex. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.
[0049]
Furthermore, other types of pigments can be used in combination as necessary.
Other dyes include metal-containing azo dyes, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes, metal-containing indoaniline dyes, triarylmethane dyes, merocyanine dyes, Examples include azulenium dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes, and pyrylium dyes.
[0050]
Furthermore, a binder, a leveling agent, an antifoaming agent, etc. can also be used together as needed.
Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.
[0051]
A reflective layer may be further formed directly or via an overcoat layer or the like on the layer having both the light absorption function and the light reflection function, and the thickness thereof is preferably 50 to 300 nm. .
As the material of the reflective layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Cr, and Pb metals are used alone or in an alloy. It is possible to use.
Among these, Au, Al, and Ag have high reflectivity and are suitable as the material for the reflective layer. In addition to these as main components, the following may be included.
For example, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Mention may be made of metals such as Bi and metalloids.
Among these, those containing Ag as a main component are particularly preferable because of low cost and high reflectivity.
[0052]
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.
Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.
In addition, a known inorganic or organic overcoat layer, undercoat layer, or adhesive layer is provided on the substrate or under the reflective layer in order to improve reflectivity, improve recording characteristics, and improve adhesion. You can also.
[0053]
As a material of the layer that combines the light absorption function and the light reflection function, or the protective layer formed on the reflection layer, a layer that combines the light absorption function and the light reflection function, or a material that protects the reflection layer from external force. If it does not specifically limit. Examples of the organic material include thermoplastic resins, thermosetting resins, electron beam curable resins, and UV curable resins.
In addition, as an inorganic substance, SiO ₂ , SiN ₄ , MgF ₂ , SnO ₂ Etc.
A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying.
The UV curable resin can be formed by preparing a coating solution as it is or by dissolving in a suitable solvent, and then applying the coating solution and curing it by irradiating with UV light.
As the UV 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 in combination, and may be used not only as a single layer but also as a multilayer film.
[0054]
As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the case of the organic compound layer. Among these, a spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 to 100 μm, but is preferably 3 to 30 μm in the present invention.
In addition, a substrate may be further bonded to the layer that combines the light absorption function and the light reflection function, or the surface of the reflection layer, or the layer that combines the light absorption function and the light reflection function, or the reflection layer surfaces are opposed to each other. Two recording media may be bonded together.
An ultraviolet curable resin layer, an inorganic thin film, or the like may be formed on the mirror surface side of the substrate in order to protect the surface and prevent the adhesion of dust and the like.
[0055]
The cover layer is necessary when using a lens with a high NA in order to increase the density.
For example, when the NA is increased, it is necessary to reduce the thickness of the portion through which the reproduction light is transmitted.
This is due to the angle at which the disk surface deviates from the optical axis of the optical pickup as the NA increases (so-called tilt angle, proportional to the square of the product of the reciprocal of the wavelength of the light source and the numerical aperture of the objective lens). This is because the allowable amount of generated aberration is reduced, and this tilt angle is easily affected by the aberration due to the thickness of the substrate.
Therefore, the thickness of the substrate is reduced to minimize the influence of aberration on the tilt angle.
[0056]
Therefore, for example, a recording layer is formed by forming irregularities on a substrate, a reflective film is provided on the recording layer, and a light-transmitting cover layer, which is a thin film that transmits light, is provided on the recording layer. An optical recording medium that reproduces information on the recording layer by irradiating light, or a reflective film on the substrate, and a recording film is formed thereon to form a recording layer. There has been proposed an optical recording medium in which a layer is provided and information on the recording layer is reproduced by irradiating the reproducing light from the cover layer side. In this way, the NA of the objective lens can be increased by reducing the thickness of the cover layer. That is, it is possible to further increase the recording density by providing a thin cover layer and recording / reproducing data from the cover layer side.
Such a cover layer is generally formed of a polycarbonate sheet or an ultraviolet curable resin. Further, the cover layer referred to in the present invention may include a layer for adhering the cover layer.
[0057]
The principle of information recording in the optical recording medium according to the present invention will be described with reference to FIG. 2 or FIG.
Using a laser with a wavelength of 500 nm or less as a light source and irradiating an optical recording medium with a power of about 5 to 15 mW, the layer that combines the light absorption function and the light reflection function absorbs light, raises the temperature and releases heat To do. This heat is transferred to the organic compound layer to induce decomposition and alteration of the organic compound. By this decomposition and alteration, the organic compound is divided into individual molecules and molecular groups constituting the organic compound, thereby increasing the intensity of the absorption bands of these individual molecules and molecular groups. The recorded pits formed by increasing the intensity of the absorption bands of the individual molecules and molecular groups produce a large difference in reflectance from the unrecorded part, so that they can be clearly detected by irradiating the reproduction laser. .
Alternatively, when a laser having a wavelength of 500 nm or less is used as the light source and the optical recording medium is irradiated with a power of about 5 to 15 mW, the layer that combines the light absorption function and the light reflection function absorbs light, raises the temperature and heats it. Release. This heat is transferred to the organic compound layer to induce decomposition and alteration of the organic compound. Due to this decomposition and alteration, the organic compound is reduced in volume, and the layer that has both the light absorption function and the light reflection function is deformed on the organic material layer side. Alternatively, when a laser having a wavelength of 500 nm or less is used as the light source and the optical recording medium is irradiated with a power of about 5 to 15 mW, the layer that combines the light absorption function and the light reflection function absorbs the light and raises the temperature by itself. Thermally expands and deforms to the organic material layer side.
The recorded pit formed by the deformation of the layer that functions as both the light absorption function and the light reflection function generates a large difference in reflectance from the unrecorded part. Therefore, it can be clearly detected by irradiating the reproduction laser. .
[0058]
Hereinafter, the function of each component in FIG. 2 or FIG. 3 will be described.
FIG. 2 shows an example of a layer structure for realizing a write-once type optical recording medium corresponding to a blue laser wavelength. A structure in which an organic compound layer and a layer having both a light absorption function and a light reflection function are sequentially provided on a substrate. Have In this structure, normal recording / reproduction is performed from the substrate side. In this structure, the layer that combines the light absorption function and the light reflection function generates heat when irradiated with laser light from the substrate side, and this heat induces state changes such as decomposition or alteration of organic compounds, and absorption at the recording / reproducing wavelength. By increasing the coefficient or by this heat, it induces a state change such as decomposition or alteration of the organic compound, causing the volume of the organic compound layer to decrease, and the layer that combines the light absorption function and the light reflection function is the organic compound layer Recording is performed by deforming to the side, or by thermally expanding the layer that combines the light absorption function and the light reflection function by this heat, and deforming the layer that combines the light absorption function and the light reflection function to the organic compound layer side. Done. In order to improve the reflectivity when not recorded, reduce the load on the recording / reproducing apparatus, and improve the recording / reproducing characteristics, the refractive index difference between the organic compound layer and the layer that combines the light absorption function and the light reflection function is set. It is preferable to enlarge it.
[0059]
FIG. 3 shows another example of a layer configuration for realizing a write-once type optical recording medium corresponding to a blue laser wavelength. A layer that combines a light absorption function and a light reflection function, an organic compound layer, and a cover layer are formed on a substrate. It has a structure provided sequentially. In this structure, normal recording / reproduction is performed from the cover layer side. In this structure, the layer that combines the light absorption function and the light reflection function is heated by laser light irradiation from the cover layer side, and this heat induces state changes such as decomposition or alteration of the organic compound, and at the recording / reproducing wavelength. By increasing the absorption coefficient or by this heat, it induces a state change such as decomposition or alteration of the organic compound, causing the volume of the organic compound layer to decrease, and the layer that combines the light absorption function and the light reflection function is formed into the organic compound. By deforming to the layer side, or by thermally expanding the layer that combines the light absorption function and the light reflection function by this heat, by deforming the layer that combines the light absorption function and the light reflection function to the organic compound layer side, Alternatively, recording is performed by thermally expanding the substrate by this heat and deforming the layer having both the light absorption function and the light reflection function to the organic compound layer side. In order to improve the reflectivity when not recorded, reduce the load on the recording / reproducing apparatus, and improve the recording / reproducing characteristics, the refractive index difference between the organic compound layer and the layer that combines the light absorption function and the light reflection function is set. It is preferable to enlarge it.
[0060]
【Example】
Examples of the present invention will be specifically described below, but the present invention is not necessarily limited thereto.
[Example 1]
It will be verified that good recording and reproduction can be realized by the layer structure and recording principle of the present invention.
For an optical recording medium in which an organic compound layer in which a main absorption band at the time of non-recording exists on the long wavelength side with respect to the recording / reproducing wavelength and a layer (Si) having both a light absorption function and a light reflection function are laminated on a substrate The reflectance and the degree of modulation were calculated when the thickness of the organic compound layer and the thickness of the Si layer were changed.
The complex refractive index of the organic compound layer when not recorded was 1.50-i0.050, and the complex refractive index after recording was assumed to be 1.50-i0.125 (note that the recording / reproducing wavelength is 405 nm). Is).
As a result, the degree of modulation (MA) is as shown in FIG. 8, and the reflectance (R) is as shown in FIG.
Further, in order to clarify a region where a high degree of modulation and a high reflectance can be obtained, the degree of modulation × the reflectance (MA × R) is shown in FIG.
In each figure, the horizontal axis represents the film thickness of the organic compound layer (dye layer), and the vertical axis represents the film thickness of the Si layer.
From this result, for example, the thickness of the organic compound layer is 60 nm or more and the thickness of the Si layer is 10 to 40 nm, or the thickness of the organic compound layer is 80 nm or more and the thickness of the Si layer is 50 nm or more. Thus, it can be seen that a modulation degree of about 50% and a reflectance of 30 to 40% can be obtained, and it is confirmed that high reflectance and high modulation degree can be achieved in an optical recording medium using an organic compound even in a blue laser wavelength region. It was.
The optimum conditions are those when the change in the complex refractive index of the organic compound layer by recording is 1.50-i0.050 to 1.50-i0.125, and the present invention is limited to this. Is not to be done.
If the increase in the absorption coefficient of the organic compound layer (imaginary part of the complex refractive index) increases, the range of the optimum condition is further expanded. For example, the film thickness of the organic compound layer can be further reduced (that is, the shallow groove Board can be used).
In this embodiment, the reflectance and the modulation factor are calculated in the configuration of the substrate / organic compound layer / layer that combines the light absorption function and the light reflection function in consideration of recording / reproduction from the substrate side. Because the cover layer is sufficiently thick with respect to the wavelength, and the refractive index of the substrate and the cover layer is almost the same, the substrate considering the recording / reproduction from the cover side / the layer that combines the light absorption function and the light reflection function / organic It is obvious that the reflectance and modulation degree in the compound layer / cover layer configuration are almost the same.
[0061]
[Example 2]
It will be verified that good recording and reproduction can be realized by the layer structure and recording principle of the present invention.
For an optical recording medium in which an organic compound layer in which a main absorption band at the time of non-recording exists on the long wavelength side with respect to the recording / reproducing wavelength and a layer (Si) having both a light absorption function and a light reflection function are laminated on a substrate The reflectance and the degree of modulation were calculated when the thickness of the organic compound layer and the thickness of the Si layer were changed.
The complex refractive index of the organic compound layer when not recorded is 1.50−i0.02, and the complex refractive index after recording is (1.50 × [χ]) − i (0.02 × 2. 0) (note that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5).
The results were as shown in FIGS. 11 (a) to (i).
(A) is a diagram showing the reflectance (R) when unrecorded, (b) is a diagram showing the degree of modulation (MA) when χ = 0.8, and (c) is a diagram showing χ = 0.8. It is a figure which shows the modulation | alteration degree x reflectance (MAxR) of time, (d) is a figure showing the modulation degree (MA) at the time of (chi) = 1.0, (e) is a time at (chi) = 1.0. (F) is a diagram showing the modulation factor (MA) when χ = 1.2, and (g) is a diagram when χ = 1.2. It is a figure which shows a modulation degree x reflectance (MAxR), (h) is a figure showing the modulation degree (MA) when χ = 1.5, and (i) is a modulation when χ = 1.5. It is a figure which shows degree x reflectance (MAxR). The above result shows the modulation degree × reflectance (MA × R) in order to clarify a region where a high modulation degree and a high reflectance can be obtained.
In each figure, the horizontal axis represents the film thickness of the organic compound layer (dye layer), and the vertical axis represents the film thickness of the Si layer.
From this calculation result, in order to ensure a high degree of modulation and a high reflectance, it is necessary that the refractive index of the organic compound layer does not decrease before and after recording (that is, (the complex refractive index of the organic compound layer after recording). Real part) ≧ (Real part of complex refractive index of organic compound layer before recording)), regardless of the degree of increase in absorption coefficient due to recording, if the Si film thickness is in the range of 10 nm or more, more preferably 10-30 nm It can be seen that a high degree of modulation and a high reflectance can be achieved.
It can also be seen that the higher the rate of increase in the absorption coefficient by recording, the thinner the organic compound layer thickness that can achieve a high degree of modulation and a high reflectance.
In this example, the reflectance and the modulation factor were calculated in the configuration of the substrate / organic compound layer / layer that combines the light absorption function and the light reflection function in consideration of recording / reproduction from the substrate side. On the other hand, since the cover layer is sufficiently thick, and the refractive index of the substrate and the cover layer is almost the same, the substrate considering the recording / reproduction from the cover side / the layer combining the light absorption function and the light reflection function / organic compound layer / It is clear that the reflectance and modulation degree in the structure of the cover layer are almost the same.
[0062]
Example 3
The complex refractive index of the organic compound layer when not recorded is 1.50−i0.02, and the complex refractive index after recording is (1.50 × [χ]) − i (0.02 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 12 (a) to (i).
[0063]
Example 4
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.02, and the complex refractive index after recording is (1.50 × [χ])-i (0.02 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 13 (a) to (i).
[0064]
Example 5
The unrecorded complex refractive index of the organic compound layer is 1.50−i0.05, and the complex refractive index after recording is (1.50 × [χ]) − i (0.05 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 14 (a) to (i).
[0065]
Example 6
The unrecorded complex refractive index of the organic compound layer is 1.50−i0.05, and the complex refractive index after recording is (1.50 × [χ]) − i (0.05 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 15 (a) to (i).
[0066]
Example 7
The unrecorded complex refractive index of the organic compound layer is 1.50−i0.05, and the complex refractive index after recording is (1.50 × [χ]) − i (0.05 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 16 (a) to (i).
[0067]
Example 8
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.07, and the complex refractive index after recording is (1.50 × [χ]) − i (0.07 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are shown in FIGS. 17 (a) to (i).
[0068]
Example 9
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.07, and the complex refractive index after recording is (1.50 × [χ])-i (0.07 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 18 (a) to (i).
[0069]
Example 10
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.07, and the complex refractive index after recording is (1.50 × [χ])-i (0.07 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 19 (a) to (i).
[0070]
Example 11
The unrecorded complex refractive index of the organic compound layer is 1.50-i0.10, and the complex refractive index after recording is (1.50 × [χ])-i (0.10 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 20 (a) to (i).
[0071]
Example 12
The complex refractive index of the organic compound layer when not recorded is 1.50-i 0.10, and the complex refractive index after recording is (1.50 × [χ]) − i (0.10 × 4.0). (The recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5), and the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 21 (a) to (i).
[0072]
Example 13
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.10, and the complex refractive index after recording is (1.50 × [χ])-i (0.10 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 22 (a) to (i).
[0073]
Example 14
The complex refractive index of the organic compound layer when not recorded is 1.50−i0.15, and the complex refractive index after recording is (1.50 × [χ]) − i (0.15 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 23 (a) to (i).
[0074]
Example 15
The complex refractive index of the organic compound layer when not recorded is 1.50−i0.15, and the complex refractive index after recording is (1.50 × [χ]) − i (0.15 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are shown in FIGS. 24 (a) to (i).
[0075]
Example 16
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.15, and the complex refractive index after recording is (1.50 × [χ])-i (0.15 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are shown in FIGS. 25 (a) to (i).
[0076]
Example 17
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.20, and the complex refractive index after recording is (1.50 × [χ])-i (0.20 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 26 (a) to (i).
[0077]
Example 18
The complex refractive index of the organic compound layer when not recorded is 1.50−i0.20, and the complex refractive index after recording is (1.50 × [χ]) − i (0.20 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are shown in FIGS. 27 (a) to (i).
[0078]
Example 19
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.20, and the complex refractive index after recording is (1.50 × [χ])-i (0.20 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results were as shown in FIGS. 28 (a) to (i).
[0079]
Example 20
When the organic compound layer is not recorded, the complex refractive index is 1.50-i0.25, and the complex refractive index after recording is (1.50 × [χ])-i (0.25 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 29 (a) to (i).
[0080]
Example 21
The unrecorded complex refractive index of the organic compound layer is 1.50−i0.25, and the complex refractive index after recording is (1.50 × [χ]) − i (0.25 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 30 (a) to (i).
[0081]
[Example 22]
The complex refractive index of the organic compound layer when not recorded is 1.50-i0.25, and the complex refractive index after recording is (1.50 × [χ]) − i (0.25 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 31 (a) to (i).
[0082]
Example 23
The unrecorded complex refractive index of the organic compound layer is 1.70-i0.05, and the complex refractive index after recording is (1.70 × [χ])-i (0.05 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 32 (a) to (i).
[0083]
Example 24
The complex refractive index of the organic compound layer when not recorded is 1.70-i0.05, and the complex refractive index after recording is (1.70 × [χ])-i (0.05 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 33 (a) to (i).
[0084]
Example 25
The complex refractive index of the organic compound layer when not recorded is 1.70-i0.05, and the complex refractive index after recording is (1.70 × [χ]) − i (0.05 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 34 (a) to (i).
[0085]
Example 26
The complex refractive index of the organic compound layer when not recorded is 1.90-i0.05, and the complex refractive index after recording is (1.90 × [χ])-i (0.05 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 35 (a) to (i).
[0086]
Example 27
The complex refractive index of the organic compound layer when not recorded is 1.90-i0.05, and the complex refractive index after recording is (1.90 × [χ])-i (0.05 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 36 (a) to (i).
[0087]
Example 28
The complex refractive index of the organic compound layer when not recorded is 1.90-i0.05, and the complex refractive index after recording is (1.90 × [χ])-i (0.05 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 37 (a) to (i).
[0088]
Example 29
An unrecorded complex refractive index of the organic compound layer is 1.30−i0.05, and a complex refractive index after recording is (1.30 × [χ]) − i (0.05 × 2.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are shown in FIGS. 38 (a) to (i).
[0089]
Example 30
The unrecorded complex refractive index of the organic compound layer is 1.30−i0.05, and the complex refractive index after recording is (1.30 × [χ]) − i (0.05 × 4.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 39 (a) to (i).
[0090]
Example 31
An unrecorded complex refractive index of the organic compound layer is 1.30−i0.05, and a complex refractive index after recording is (1.30 × [χ]) − i (0.05 × 6.0). Assuming that the recording / reproducing wavelength is 405 nm and χ is 0.8, 1.0, 1.2, and 1.5, the same simulation as in Example 2 was performed.
The results are as shown in FIGS. 40 (a) to (i).
[0091]
In addition, in the figure which shows the calculation result in the said Examples 3-31, ie, FIGS. 12-40, (a) is a figure showing the reflectance (R) at the time of unrecording, (b) is (chi) = 0. FIG. 8 is a diagram showing the modulation factor (MA) when 8; (c) is a diagram showing the modulation factor × reflectance (MA × R) when χ = 0.8; and (d) is χ = 1.0. (E) is a diagram showing the degree of modulation × reflectance (MA × R) when χ = 1.0, and (f) is a diagram showing χ = 1.2. (G) is a diagram showing the modulation factor × reflectance (MA × R) when χ = 1.2, and (h) is a diagram showing the modulation factor (MA) at the time. (I) is a figure which shows the modulation degree x reflectance (MAxR) at the time of (chi) = 1.5. The above result shows the modulation degree × reflectance (MA × R) in order to clarify a region where a high modulation degree and a high reflectance can be obtained.
In each figure, the horizontal axis represents the film thickness of the organic compound layer (dye layer), and the vertical axis represents the film thickness of the Si layer.
[0092]
As described above, from the calculation results of Examples 2 to 31, in order to ensure a high degree of modulation and a high reflectance, it is necessary that the refractive index of the organic compound layer does not decrease before and after recording (that is, (after recording) The real part of the complex refractive index of the organic compound layer) ≧ (the real part of the complex refractive index of the organic compound layer before recording)), regardless of the increase in the absorption coefficient due to recording, the Si film thickness is 10 nm or more, more preferably 10 It can be seen that a high degree of modulation and a high reflectance can be achieved in the range of ˜30 nm.
It can also be seen that the higher the rate of increase in the absorption coefficient by recording, the thinner the organic compound layer thickness that can achieve a high degree of modulation and a high reflectance.
In this example, the reflectance and the modulation factor were calculated in the configuration of the substrate / organic compound layer / layer that combines the light absorption function and the light reflection function in consideration of recording / reproduction from the substrate side. On the other hand, since the cover layer is sufficiently thick, and the refractive index of the substrate and the cover layer is almost the same, the substrate considering the recording / reproduction from the cover side / the layer combining the light absorption function and the light reflection function / organic compound layer / It is clear that the reflectance and modulation degree in the structure of the cover layer are almost the same.
[0093]
[Example 32]
Next, it was confirmed that the absorption coefficient (imaginary part of the complex refractive index) of the organic compound layer was increased by recording.
On a polycarbonate substrate having a guide groove (groove depth 55 nm), an organic compound layer composed of the following formula (2) [Dye (NK3578) manufactured by Hayashibara Biochemical Laboratories Co., Ltd.] is formed by spin coating, An optical recording medium was prepared in which a Si layer (a layer having both a light absorption function and a light reflection function) of 25 nm was provided thereon, and a protective layer made of an ultraviolet curable resin was further provided thereon with a thickness of about 2 μm.
The complex refractive index of the following formula (2) at 405 nm is 1.510-i0.050, which is significantly inferior to the complex refractive index required for organic compounds used in conventional write-once optical recording media. The complex refractive index (for example, the complex refractive index in the vicinity of the recording / reproducing wavelength of the dye used in DVD-R is, for example, about 2.5-i 0.10).
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
As a result, a signal having a modulation degree of about 58% was obtained.
Further, the layer having both the light absorption function and the light reflection function of this optical recording medium was peeled off, and the dyes in the recorded part and the unrecorded part were dissolved in ethanol, and the spectra were measured respectively.
As a result, as shown in FIG. 41, it is recognized that the absorption coefficient (imaginary part of the complex refractive index) is clearly increased in the recording part (recording was performed only on the groove part, so There is a large amount of unrecorded part components), and the recording principle of the optical recording medium of the present invention was confirmed.
Further, as assumed in Example 1, the basis for assuming that the absorption coefficient (imaginary part of the complex refractive index) of the organic compound layer increases by about 2.5 times by recording was supported (actually, the following formula (2) ), An increase in absorption coefficient of 6 times or more was confirmed, and the result of Example 1 assuming that the absorption coefficient increased by about 2.5 times has sufficient reliability).
However, in the present invention, the increase in the absorption coefficient (imaginary part of the complex refractive index) of the organic compound layer by recording is not limited to about 2.5 times.
Further, this optical recording medium was cut with an FIB (Focused Ion Beam), and the state of the recording part was observed with SEM and TEM. As a result, it was confirmed that the Si layer was deformed by an average of about 30 nm toward the organic compound layer side. In other words, this is also a result of supporting that the volume of the organic compound layer was reduced by recording.
[0094]
[Chemical formula 2]

[0095]
(Recording conditions)
Recording linear density: 1T = 0.0917 (μm)
Recording linear velocity: 6.0 (m / s)
Recording strategy: Basic strategy T _top -T _mp = 1.40-0.75 (T)
Recording power: 8.5 (mw)
Recording pattern: 8-16 modulation signal
[0096]
As described above, from Examples 1 to 32 of the present invention, the layer configuration and recording principle of the optical recording medium of the present invention are very effective for realizing a write-once type optical recording medium made of an organic compound corresponding to the blue laser wavelength. It could be confirmed.
In addition, in the conventional optical recording medium using an organic compound, it is necessary to generate heat in the organic compound layer. Therefore, the organic compound layer cannot be thinned and a deep groove (for example, 150 to 180 nm) is required. It was confirmed that a substrate having a very shallow groove of about 50 nm can be applied because an organic compound can be thinned by the recording principle of the invention.
However, in the present invention, the groove depth of the substrate is not limited to about 50 nm.
[0097]
Example 33
Complex refractive index (refractive index n and absorption coefficient k) of a dye represented by the following general formula (3) that can be used for a conventional DVD-R, can be used in the present invention, and is also used for a conventional DVD-R The complex refractive index (refractive index n and absorption coefficient k) of the dye (NK4382 manufactured by Hayashibara Biochemical Laboratories Co., Ltd.) and the complex refractive index of Si (refractive index n and absorption coefficient k) were measured.
The complex refractive index (refractive index n and absorption coefficient k) of the dye represented by the following general formula (3) that can be used for the conventional DVD-R is shown in FIG. 42 and can be used in the present invention. The complex refractive index (refractive index n and absorption coefficient k) of the dye (NK4382) that can also be used in FIG. 43 and the complex refractive index of Si (refractive index n and absorption coefficient k) are as shown in FIG. is there.
As a result, in the case of the conventional recording method in which the recording / reproducing wavelength is positioned on the long wavelength side of the absorption band of the organic compound with respect to the conventional recording material (FIG. 42), the refractive index n against the fluctuation of the recording / reproducing wavelength. It was confirmed that the absorption coefficient k greatly fluctuated.
On the other hand, the present invention is a recording method in which the recording / reproducing wavelength is positioned sufficiently shorter than the absorption band of the organic compound with respect to the conventional recording material (FIG. 43). It was confirmed that n and the absorption coefficient k hardly fluctuate.
It was also confirmed that Si used as a layer having both the light absorption function and the light reflection function did not vary greatly in the refractive index n and the absorption coefficient k with respect to the change in the recording / reproducing wavelength.
As described above, with the layer structure of the optical recording medium of the present invention, the write-once type optical recording medium has less changes in recording characteristics such as recording sensitivity, modulation degree, jitter and error rate, and reflectance, etc., with respect to fluctuations in the recording / reproducing wavelength. It was confirmed that can be realized.
[0098]
[Chemical 3]

[0099]
【The invention's effect】
As described above, as is clear from the detailed and specific description, the write-once type optical recording medium made of an organic compound corresponding to the blue laser wavelength or less, the shallow groove substrate having good transferability, according to the optical recording medium of the present invention and its recording principle. Is a write-once type optical recording medium made of an organic compound that can be used for recording / reproducing wavelengths, recording characteristics such as recording sensitivity, modulation degree, jitter, error rate, etc. An optical recording medium can be provided easily and inexpensively.
Further, the layer structure of the write once optical recording medium according to claim 1 of the present invention makes it difficult to obtain an optical constant comparable to the optical constant required for the recording layer of a conventional write once optical recording medium. Even in the following areas, it is possible to realize a write-once type optical recording medium that can achieve high density and obtain good recording / reproducing characteristics by recording / reproducing from the substrate side. In addition, it is possible to realize a write-once type optical recording medium that can be easily recorded and reproduced even on a shallow groove substrate with good transferability, and a write-once type optical recording medium that has little change in recording and reproduction characteristics with respect to fluctuations in the recording and reproduction wavelength.
Further, according to the layer configuration of the write-once type optical recording medium according to claims 2 and 3 of the present invention and the definition of the organic compound, an optical constant comparable to the optical constant required for the recording layer of the conventional write-once type optical recording medium Even in the region where the wavelength of the blue laser beam is difficult to obtain, it is possible to realize a write-once type optical recording medium that can achieve high recording density and good recording / reproducing characteristics by recording / reproducing from the substrate side. In addition, it is possible to realize a write-once type optical recording medium that can be easily recorded and reproduced even on a shallow groove substrate with good transferability, and a write-once type optical recording medium that has little change in recording and reproduction characteristics with respect to fluctuations in the recording and reproduction wavelength.
Further, the layer structure of the write-once optical recording medium according to claim 4 of the present invention makes it difficult to obtain an optical constant comparable to the optical constant required for the recording layer of a conventional write-once optical recording medium. Even in the following regions, it is possible to realize a write-once type optical recording medium that can achieve high density and obtain good recording and reproducing characteristics by recording and reproducing from the cover layer side. In addition, it is possible to realize a write-once type optical recording medium that can be easily recorded and reproduced even on a shallow groove substrate with good transferability, and a write-once type optical recording medium that has little change in recording and reproduction characteristics with respect to fluctuations in the recording and reproduction wavelength.
Further, according to the layer configuration of the write-once type optical recording medium according to claims 5 and 6 of the present invention and the definition of the organic compound, an optical constant comparable to the optical constant required for the recording layer of the conventional write-once type optical recording medium Even in the region of the blue laser wavelength or less that is difficult to obtain, it is possible to realize a write-once optical recording medium that can achieve high recording density and good recording / reproducing characteristics by recording / reproducing from the cover layer side. In addition, it is possible to realize a write-once type optical recording medium that can be easily recorded and reproduced even on a shallow groove substrate with good transferability, and a write-once type optical recording medium that has little change in recording and reproduction characteristics with respect to fluctuations in the recording and reproduction wavelength.
Further, the recording / reproducing characteristics of the write-once optical recording medium according to any one of claims 1 to 6 can be improved by defining the recording / reproducing wavelength, the material used as the layer having both the light absorbing function and the light reflecting function. It becomes possible to make it.
In addition, it is difficult to obtain an optical constant comparable to the optical constant required for the recording layer of a conventional write-once type optical recording medium by the optical recording medium recording method according to claims 12 and 13 of the present invention. Even in the region below the laser wavelength, it is possible to realize a recording method (recording principle) of a write-once type optical recording medium that can achieve high density by recording / reproducing from the substrate side and obtain good recording / reproducing characteristics. Further, it is possible to realize a recording method for a write-once type optical recording medium that can be easily recorded and reproduced even with a shallow groove substrate having good transferability.
In addition, it is difficult to obtain an optical constant comparable to the optical constant required for the recording layer of a conventional write-once optical recording medium by the optical recording medium recording method according to claims 14 and 15 of the present invention. Even in the region below the laser wavelength, it is possible to realize a recording method (recording principle) for a write-once optical recording medium that can achieve high recording density and good recording / reproducing characteristics by recording / reproducing from the cover layer side. Further, it is possible to realize a recording method for a write-once type optical recording medium that can be easily recorded and reproduced even with a shallow groove substrate having good transferability.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a layer structure of a conventional optical recording medium.
FIG. 2 is a diagram for explaining a layer structure of an optical recording medium of the present invention.
FIG. 3 is a diagram for explaining another layer configuration of the optical recording medium of the present invention.
FIG. 4 is a diagram for explaining the recording principle of a conventional optical recording medium.
FIG. 5 is a diagram for explaining the recording principle of the optical recording medium of the present invention.
FIG. 6 is a diagram for explaining the characteristics of an organic compound used in the optical recording medium of the present invention.
FIG. 7 is a diagram for explaining the characteristics of an organic compound used in the optical recording medium of the present invention.
8 is a diagram illustrating a calculation result of a modulation factor (MA) in Example 1. FIG.
9 is a diagram showing the calculation result of reflectance (R) in Example 1. FIG.
10 is a diagram showing a calculation result of modulation degree × reflectance (MA × R) in Example 1. FIG.
11 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 2. FIG.
12 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × the reflectance (MA × R) in Example 3. FIG.
13 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 4. FIG.
14 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 5. FIG.
15 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 6. FIG.
16 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 7. FIG.
17 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 8. FIG.
18 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 9. FIG.
19 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 10. FIG.
20 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 11. FIG.
FIG. 21 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 12.
22 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 13. FIG.
23 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 14. FIG.
24 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 15. FIG.
25 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 16. FIG.
FIG. 26 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 17.
27 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 18. FIG.
28 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 19. FIG.
29 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 20. FIG.
30 is a diagram showing the calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × the reflectance (MA × R) in Example 21. FIG.
FIG. 31 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 22.
32 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectivity (MA × R) in Example 23. FIG.
33 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 24. FIG.
34 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 25. FIG.
FIG. 35 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 26.
36 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflection (MA × R) in Example 27. FIG.
FIG. 37 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × reflectance (MA × R) in Example 28.
38 is a diagram showing calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × the reflectance (MA × R) in Example 29. FIG.
FIG. 39 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × the reflectance (MA × R) in Example 30.
40 is a diagram illustrating calculation results of the degree of modulation (MA), the reflectance (R), and the degree of modulation × the reflectance (MA × R) in Example 31. FIG.
41 is a diagram showing changes in spectrum before and after recording of the dye used in Example 32. FIG.
FIG. 42 is a diagram showing a complex refractive index in a conventional recording / reproducing wavelength region.
FIG. 43 is a diagram showing a complex refractive index in the recording / reproducing wavelength region of the present invention.
FIG. 44 is a diagram showing a complex refractive index of Si used in the present invention.
[Explanation of symbols]
1 Substrate
2 Organic compound layer
3 Layer that combines light absorption and light reflection functions
4 Cover layer
5 reflective layers

Claims (15)

On the substrate, there is a structure in which an organic compound layer in which at least a main absorption band at the time of non-recording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a layer that combines a light absorption function and a light reflection function are sequentially laminated, An optical recording medium, wherein recording / reproduction is performed from the substrate side. On the substrate, there is a structure in which an organic compound layer in which at least a main absorption band at the time of non-recording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a layer that combines a light absorption function and a light reflection function are sequentially laminated, An optical recording medium that performs recording / reproduction from the substrate side, and the organic compound constituting the organic compound layer absorbs at the recording / reproducing wavelength by heat generation by the light absorption function of the layer that combines the light absorption function and the light reflection function. An optical recording medium using an organic compound having an increased coefficient. On the substrate, there is a structure in which an organic compound layer in which at least a main absorption band at the time of non-recording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a layer that combines a light absorption function and a light reflection function are sequentially laminated, An optical recording medium that performs recording / reproduction from the substrate side. As an organic compound constituting the organic compound layer, the light absorption function and the light reflection are caused by the heat generated by the light absorption function of the layer that combines the light absorption function and the light reflection function. An optical recording medium comprising an organic compound that causes a volume reduction so that a layer that also functions is deformed toward the organic compound layer. A structure in which a layer that combines at least a light absorption function and a light reflection function, an organic compound layer in which the main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a cover layer are sequentially laminated on the substrate. An optical recording medium having recording and reproduction from the cover layer side. A structure in which a layer that combines at least a light absorption function and a light reflection function, an organic compound layer in which the main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a cover layer are sequentially laminated on the substrate. An optical recording medium that performs recording and reproduction from the cover layer side, and records and reproduces the organic compound constituting the organic compound layer by heat generated by the light absorption function of the layer that combines the light absorption function and the light reflection function An optical recording medium comprising an organic compound having an increased absorption coefficient at a wavelength. A structure in which a layer that combines at least a light absorption function and a light reflection function, an organic compound layer in which the main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a cover layer are sequentially laminated on the substrate. And an optical recording medium that performs recording / reproduction from the cover layer side, and the organic compound constituting the organic compound layer absorbs light by heat generated by the light absorption function of the layer that combines the light absorption function and the light reflection function. An optical recording medium comprising an organic compound that causes a volume reduction so that a layer that has both a function and a light reflection function is deformed toward the organic compound layer. The complex refractive index imaginary part of a layer that serves both as a light absorption function and a light reflection function >> (imaginary complex refractive index imaginary part of an organic compound layer), according to any one of claims 1 to 6 Optical recording medium. 7. (Real part of complex refractive index of layer having both light absorption function and light reflection function)> (real part of complex refractive index of organic compound layer) Optical recording medium. The optical recording according to any one of claims 1 to 6, wherein (real part of complex refractive index of organic compound layer after recording) ≥ (real part of complex refractive index of organic compound layer before recording). Medium. 9. The light according to claim 1, wherein a recording / reproducing wavelength is 500 nm or less, and a layer having both a light absorption function and a light reflection function is mainly composed of Si or Ge. recoding media. An optical recording medium having a recording / reproducing wavelength of 500 nm or less and a layer having both a light absorption function and a light reflection function mainly composed of Si, and a film thickness of the layer having both a light absorption function and a light reflection function The optical recording medium according to claim 1, wherein the optical recording medium is 10 nm or more. On the substrate, there is a structure in which an organic compound layer in which at least a main absorption band at the time of non-recording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a layer that combines a light absorption function and a light reflection function are sequentially laminated, A recording method for an optical recording medium in which recording / reproduction is performed from the substrate side, wherein the absorption coefficient at the recording / reproducing wavelength of the organic compound layer is mainly determined by heat generated by the light absorption function of the layer having both the light absorption function and the light reflection function. A recording method for an optical recording medium, wherein recording is performed by increasing the number. On the substrate, there is a structure in which an organic compound layer in which at least a main absorption band at the time of non-recording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a layer that combines a light absorption function and a light reflection function are sequentially laminated, A recording method for an optical recording medium in which recording / reproduction is performed from the substrate side, wherein a layer that combines the light absorption function and the light reflection function is mainly formed by heat generated by the light absorption function of the layer that combines the light absorption function and the light reflection function. A recording method for an optical recording medium, wherein recording is performed by deforming toward the organic compound layer side. A structure in which a layer that combines at least a light absorption function and a light reflection function, an organic compound layer in which the main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a cover layer are sequentially laminated on the substrate. A recording method of an optical recording medium in which recording / reproduction is performed from the cover layer side, and mainly at the recording / reproducing wavelength of the organic compound layer due to heat generation by the light absorption function of the layer having both the light absorption function and the light reflection function. A recording method for an optical recording medium, wherein recording is performed by increasing the absorption coefficient of the recording medium. A structure in which a layer that combines at least a light absorption function and a light reflection function, an organic compound layer in which the main absorption band at the time of unrecording exists on the long wavelength side with respect to the recording / reproducing wavelength, and a cover layer are sequentially laminated on the substrate. A recording method of an optical recording medium in which recording / reproduction is performed from the cover layer side, and the light absorption function and the light reflection function are mainly generated by heat generation by the light absorption function of the layer having both the light absorption function and the light reflection function. A recording method for an optical recording medium, wherein recording is performed by deforming a layer that also serves as an organic compound layer.

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