JP3611170B2 - Optical recording medium - Google Patents

Description

（式中、Ｓ^１およびＳ^２それぞれアルキル基、アリール基またはアルコキシル基のいずれかであり、Ｗ^１およびＷ^２はハロゲン原子、水素原子、アルキル基、アルコキシル基、アリール基、アルコキシスルホニル基、スルホニルアルキル基、シアノ基等の置換を表し、Ｚ^１およびＺ^２はそれぞれイオウ原子、酸素原子、セレン原子またはエチレン等の置換基を表す）で表されるシアニン系色素（特開昭５９−２４６９２号公報、特開平２−８７３４１号公報、特開平６−３２０８６９号公報、特開平６−３３８０５９号公報、特開平６−１９９０４５号公報、特開平７−２６２６１１号公報、特開昭６２−２０１２８８号公報、特公平７−４９８１号公報、特公平８−２５４７０３３号公報等）等が知られている。
【０００７】
上述の色素系のうち、主に高感度で高Ｓ／Ｎ比等を得ることができ、更に熱的特性および薄膜化等の点からシアニン系が主に用いられている。その中でも特にＣＤに準拠させる為に、一般に半導体レーザー波長から７８０ｎｍ〜８３０ｎｍ付近に吸収と反射率を持つ色素で、上記式（ＩＩ）中の分子構造の中央のメチレン鎖ｑが２となるものが一般に多く用いられている。しかしながら、このような色素記録膜は本目的の短波長レーザーには対応できないという致命的な課題がある。
【０００８】
また再生劣化、色素膜の長期安定性、Ｃ／Ｎ比およびジッター成分等に問題があるとされている。これらの原因は、（ｉ）長時間に及ぶ読み出し光の露光による記録膜部分の熱蓄積により、色素そのものが劣化退色する現象、（ｉｉ）読み出し光がピット部分と無記録部分を判別すべき記録膜の境界面において吸収され、徐々に境界面の溶融ないし熱変形をおこす現象が生じ、その上に同様の熱蓄積によりピットの輪郭のくずれ等が重なる現象、（ｉｉｉ）色素が光励起された際に、色素から雰囲気中に存在する酸素へのエネルギー移動により生じる一重項酸素による色素の酸化劣化（色素の退色）、（ｉｖ）さらに長期保存時の劣化現象として、自然光とシアニン色素の酸化等による色素の透過率変化と酸素・水分等による色素同士の会合・凝集等により、透過率の変化とノイズの発生を引き起こすことなどが考えられる。この問題を解決すべく、従来から種々の提案がなされている（例えば、特開昭６２−２０１２８８号公報、特開昭６２−２０１２８９号公報、特開昭５７−６６５４１号公報、特開昭５９−１２４８９４号公報、特開昭５９−２０３２４７号公報、特開昭６２−１３３１７３号公報、特開昭６３−１９８０９６号公報、特開昭５９−２１３３９号公報、特開昭５７−１１０９０号公報、特開昭６０−４４３８９号公報、特開昭６０−７１２９６号公報、特開昭６３−１５９４号公報、特開昭５７−１１０９０号公報、特開平５−３８８７９号公報、特開平７−２６２６１１号公報、特公平７−４９８１号公報等）。しかしながら、いまだに十分な解決に至っていないのが実状である。
【０００９】
更に、ＤＶＤ−ＲＯＭ規格に準拠した記録密度の高い光記録媒体の開発が進められている。これは、半導体レーザーの波長を現行のＣＤ用より短い６００〜６８０ｎｍ前後とし、またＳＨＧ素子等を利用して光の波長を短くし、レーザー回折限界まで対物レンズを絞り込んでビームスポット径を小さくすることにより記録密度を高めようとする方法である。
【００１０】
このようなＤＶＤ−ＲＯＭ用の色素材料を開発するために、前記一般式（ＩＩ）に代表されるＣＤ用シアニン系色素の改良の試みや、短波長用シアニン色素の提案がなされている（例えば、特開平５−３８８７９号公報、特開平６−４０１６２号公報、特開平６−３２０８６９号公報、特開平６−１８６５３０号公報、特開平６−１９９０４５号公報、特開平７−２６２６１１号公報、特開平８−３０６０７４号公報、特公平１−２１７９８号公報、特公平７−４９８１号公報等）。
【００１１】
【発明が解決しようとする課題】
しかしながら、記録層が目的の波長に対応した感度、膜の安定性（信頼性）等が得られず、高密度化の際、隣り合ったピット同士の熱干渉等によって再生信号に含まれるジッター成分が増大するなど多くの問題が解決するに至っていない。
【００１２】
本発明は上述の点に鑑みてなされ、その目的は、短波長の半導体レーザー（波長５００〜７００ｎｍ）に対応できる光学特性、化学的、光化学的、物理的、熱的安定性が良好な有機色素薄膜と媒体構成を見出すことにより、光記録媒体の特性として高感度でかつ色素膜の安定性に優れ、特に高密度記録化においてＣ／Ｎ比が高く、また再生信号に含まれるジッター成分を低減させることのできる、ＤＶＤの規格に対応した光記録媒体を提供することにある。
【００１３】
【課題を解決するための手段】
本発明者は、上記課題を解決すべく種々の色素について鋭意研究した結果、特定のスチル系シアニン色素を主成分とした記録層を用いた構成からなる光記録媒体が、短波長（５００〜７００ｎｍ）に対応し、高感度であり、かつ再生劣化が低減して長期信頼性を有し、また高密度化におけるピット同士の熱干渉、熱蓄積が低減され、特に高密度化においてＣ／Ｎ比を向上させ、かつジッター成分を低減させることができ、ＤＶＤに対応できることを見出し、本発明を完成するに至った。
【００１４】
すなわち、本発明は下記の通りである。
（１）グルーブが形成された、レーザー光に対して透過性の樹脂基板の表面に、少なくとも記録層と金属反射層とが積層されてなる光記録媒体において、
前記記録層が下記の一般式（Ｉ）、

（式中、Ｒ^１は炭素数３から１８の不飽和結合基を有する置換基、Ｒ^２はアルキル基またはアリール基、陰イオンＸ⁻はＩ⁻、Ｂｒ⁻、ＣｌＯ_４ ⁻、ＢＦ_４ ⁻、ＰＦ_４ ⁻、ＳｂＦ_４ ⁻、ＣＨ_３ＳＯ_４ ⁻またはＣＨ_３−Ｃ_６Ｈ_４−ＳＯ_３ ⁻、Ｙ^１ａおよびＹ^１ｂは双方とも電子吸引基またはいずれか一方が電子吸引基で他方が水素原子、Ｙ^２は電子供与基を示す）で表されるスチリル系シアニン色素を主成分とした、短波長レーザーに対応する有機薄膜からなることを特徴とする光記録媒体である。
【００１５】
（２）前記光記録媒体において、Ｙ^1aおよびＹ^1bは双方ともニトロ基、水酸基、カルボキシル基、カルボニル基、シアノ基、アルコキシシアノ基、ハロゲン原子またはこれらのいずれかを末端に有する電子吸引基か、あるいはいずれか一方が該電子吸引基で他方が水素原子であり、Ｙ²は−ＮＨ₂；−Ｎ（Ｒ³）₂（式中、Ｒ³は炭素数１〜７のアルキル基またはアリール基）；−Ｎ（Ｒ⁴Ｒ⁵）₂（式中、Ｒ⁴およびＲ⁵は個々に独立して炭素数１〜７のアルキル基またはアリール基）；末端に−ＮＨ₂、−Ｎ（Ｒ³）₂（式中、Ｒ³は前記のものと同じもの）または−Ｎ（Ｒ⁴Ｒ⁵）₂（式中、Ｒ⁴およびＲ⁵は前記のものと同じもの）を有する炭素数１から１８のアルキル基、アリール基、アリールアルケニル基、アリールアゾ基またはアルコキシル基；およびヒドラジノカルボニル基からなる群から選択される含窒素化合物誘導体およびアルキル基の電子供与基である光記録媒体である。
【００１６】
（３）前記光記録媒体において、前記記録層が前記一般式（Ｉ）で表されるスチリル系シアニン色素を２種以上含む複合系からなる有機薄膜である光記録媒体である。
【００１７】
（４）前記光記録媒体において、前記記録層が酸素クエンチャーを１％以上含有する光記録媒体である。
【００１８】
（５）前記光記録媒体において、前記記録層上に、該記録層より高融点であり、かつ反射率がレーザ光の波長に対して５５％以上有するＡｌ、Ａｕ、Ａｇ、Ｃｕ、Ｎｉ、Ｔｉおよびカルコゲナイド系金属からなる群から選ばれる単独または合金からなる金属薄膜の金属反射層が積層されてなる光記録媒体である。
【００１９】
（６）前記光記録媒体において、前記記録層上に逐次金属反射層および保護層が積層されてなる光記録媒体である。
【００２０】
（７）前記光記録媒体において、グルーブ形成された基板上に記録層と金属反射層を順次積層し、さらに保護層を積層した一面型の基板と、無グルーブ基板とを接着剤で貼り合せてなる光記録媒体である。
【００２１】
（８）前記光記録媒体において、基板上に記録層と金属反射層を順次積層し、さらに保護層を積層した一面型同士を保護層を介して接着剤で貼り合せてなる両面型の光記録媒体である。
【００２２】
（９）前記光記録媒体において、基板の両面にグルーブが成型時に形成されているとともに、該基板の両面上に記録層と、金属反射層と、更に保護層とが順次積層されてなる光記録媒体である。
【００２３】
【発明の実施の形態】
以下に、本発明の具体的構成について図面に基づき詳細に説明する。
図１〜４に本発明の光記録媒体の構成例を示す。
図示する基板１はディスク形状をなし、図１、２および３に示す基板１の片側表面に、トラッキング用のプリピットまたはプリグルーブが同心円状にまたはスパイラル状に形成されている。このようなプリピットまたはプリグルーブを有する基板１は生産性の観点等から、射出成形樹脂からなり、好ましくは記録光および再生光（５００〜７００ｎｍ程度）の半導体レーザー光、特に６００〜６８０ｎｍ）に対し、実質的に透明（レーザー光の透過率が８５％以上）な樹脂から形成される。基板１の厚さは、図１に示す構成例おいては１．０〜１．５ｍｍ程度であり、図２および３に示すタイプでは０．５〜０．６５ｍｍ程度である。
【００２４】
また、図４に示す構成例では、基板１の両面にプリピットまたはプリグルーブが同時成形で形成され、基板１の厚さは１．０〜１．５ｍｍ程度である。
【００２５】
図１〜４に示す基板１の直径はいずれも５０〜１２０ｍｍ程度である。また、基板１を構成する樹脂は特に限定されないが、成形性および光透過性の観点から、ポリカーボネート樹脂、ポリアクリル樹脂、ポリエステル樹脂、アモルファスオレフィン樹脂、ＴＰＸ、アートン樹脂等の熱可塑性樹脂を主成分とする。
【００２６】
基板１のトラックピッチは０．７〜１．６μｍからなる。また、グルーブの深さはレーザー光の位相により、トラッキング制御や情報の担持等に利用される。グルーブの深さは、５０〜２３０ｎｍ位であり、好ましくは７０〜２００ｎｍ位である。グルーブが浅すぎるとグルーブ底面の変形率と金属反射膜への変形による影響が大きくなり易く、再生信号歪みを誘発しやすくなり、Ｃ／Ｎ比の低下およびジッターが大きくなる傾向となり、変調度が小さくなる原因となる。一方、グルーブが深すぎると、記録マーク部のグルーブ底面の変形量が不安定となり、ジッターが増大する。これにより、再生信号やトラッキング信号の波長依存性が大きくなる。よって、高密度記録の際における半導体レーザー光の波長に対してグルーブの深さは重要であり、記録層２の有機薄膜の特性、成膜性等によって深さ、形状等を最適化する必要があり、記録層２の材料構造、組成が大きくグルーブに影響する。
【００２７】
この基板１、１’の上に形成されている記録層２は、前記一般式（Ｉ）で表されるスチリル系シアニン色素を主成分とした有機薄膜である。本発明に係るスチリル系シアニン色素は、いずれも薄膜化した際に５００〜７００ｎｍに吸収・反射波長を有し、目的とするレーザー波長（６００〜６８０ｎｍ）に対して十分な感度と反射率を有する。
【００２８】
特には、前記一般式（Ｉ）で表されるスチリル系シアニン色素の置換基Ｒ^１は炭素数３から１８、好ましくは３から９位の不飽和結合基を有する置換基であり、好適例としてはアリル、ビニル、アリリデン、アリレオキシ、クロトノイル、スチリル、ビニリデン、ビニレン、メチリジン、アクリルキシ、メタアルリルオキシ、イソプロペニル、エチニル、ブテニル等を挙げることができ、かかる基は、溶解性に影響し、特に成膜性と基板の表面との相性が非常に良好となり、安定性が向上する。
【００２９】
また、Ｒ¹に不飽和結合基を導入するとともに、Ｙ^1aおよびＹ^1bは双方とも電子吸引基またはいずれか一方が電子吸引基で他方が水素原子であり、好ましくは双方ともニトロ基、水酸基、カルボキシル基、カルボニル基、シアノ基、アルコキシシアノ基、ハロゲン原子またはこれらのいずれかを末端に有する電子吸引基か、あるいはいずれか一方が該電子吸引基で他方が水素原子である。また、Ｙ²は電子供与基であり、好ましくは−ＮＨ₂；−Ｎ（Ｒ³）₂（式中、Ｒ³は炭素数１〜７のアルキル基またはアリール基）；−Ｎ（Ｒ⁴Ｒ⁵）₂（式中、Ｒ⁴およびＲ⁵は個々に独立して炭素数１〜７のアルキル基またはアリール基）；末端に−ＮＨ₂、−Ｎ（Ｒ³）₂（式中、Ｒ³は前記のものと同じもの）または−Ｎ（Ｒ⁴Ｒ⁵）₂（式中、Ｒ⁴およびＲ⁵は前記のものと同じもの）を有する炭素数１から１８のアルキル基、アリール基、アリールアルケニル基、アリールアゾ基またはアルコキシル基；およびヒドラジノカルボニル基からなる群から選択される含窒素化合物誘導体およびアルキル基の電子供与基である。これらの置換基を導入することにより、例えば、下記式（Ｉ−２）で表されるスチリル系シアニン色素の分光図は、図５に示すように光学特性に優れたものとなる。よって、高感度でＳ／Ｎ比が高く、かつ均一な薄膜が得られ易い点から、高Ｃ／Ｎ比が得られる。また、本発明に係るスチリル系シアニン色素を複合化等により薄膜化することにより色素の凝集、会合現象等を抑制することができる。以上の効果により高感度、高Ｓ／Ｎ比、高Ｃ／Ｎが得られ、かつ均一な成膜安定性、信頼性に優れた光記録媒体を得ることができる。
【００３０】
本発明に係るスチリル系シアニン色素は公知である合成法（例えば、米国特許第２，７３４，９００号、米国特許第２，１１２，２１３９号、米国特許第２，８８７，４７９等）を参照して合成することができ、具体例を下記に示す。
【００３１】

【００３２】

【００３３】

【００３４】

【００３５】
本発明に係るスチリル系シアニン色素は単独で用いてもよいが、２種以上複合化することにより、その分光、例えばレーザー光の吸収、反射率等を調整することができるともに、より薄膜化におけるアモルファス状態での膜の安定性が得られ、かかる機能から高感度、ジッター成分の抑制、ノイズの発生防止を行うことができ、長期保存性が向上する。
【００３６】
また、記録層２は、このような色素とともに酸素クエンチャー（光安定剤）を１％以上、好ましくは３〜２０％含有していてもよい。記録層における酸素クエンチャーの含有量が多すぎると、クエンチャーがブリードなどを起こし、ノイズ発生の要因となることがある。このクエンチャーは、紫外線およびレーザー光等によるスチリル系シアニン色素の劣化により発生したラジカルを捕捉し、連鎖反応を停止させるものである。これにより、光安定性を向上させ、特に再生光による脱色を防止することができる。以上の結果、本発明に係る記録層は長期保存性を実現でき、また光により発生する熱による膜の流動を抑制することができ、ノイズの発生とジッターの上昇を抑制することができる。
【００３７】
本発明に係るスチリル系シアニン色素と共に用いられる酸素クエンチャーは、単独又は複合化することができ、特に限定されないが、一般的に使用されている以下のものが具体例として挙げられる。
【００３８】
金属錯体系
Ｑ１：ビス（４−テトラ−ブチル−１，２−ジチオフェノレート）Ｍ−テトラ−ｎ−ブチルアンモニウム（ＭはＣｕ、Ｃｏ、Ｎｉ、Ｆｅ等）
住友精化（株）社製ＢＢＴシリーズ
Ｑ２：ビス［４−（ジエチルアミノ）−α、β−スチルベンヂチオレート］ニッケル
（株）日本感光色素研究所社製ＮＫＸ−１１４
Ｑ３：ビス［３−メトキシ−４−（２−メトトオキシエトオキシ）−２’−クロロ−α、β−スチルベンジチオレート］ニッケル
（株）日本感光色素研究所社製ＮＫＸ−１１９９
Ｑ４：１，２−ベンゼンジチオールニッケル錯体
三井東圧化学（株）社製 ＰＡ−１００６ 等
【００３９】
アミン／アンモニウム塩系
Ｑ５：ビスイミニウム塩
日本化薬（株）社製 ＩＲＧ−０３
Ｑ６：Ｎ，Ｎ，Ｎ’，Ｎ”−テトラキス（ｐ−ジブチルアミノフェニル）ｐ−フェニレンジアミン
帝国化学（株）社製 ＮＩＲ−ＡＭ１
Ｑ７：４−ニトロソ−４’−（ジメチルアミノ）ジフェニルアミン
（株）日本感光色素研究所社製ＮＫＸ−１５４９
【００４０】
酸素クエンチャーは、特にこれら具体例のものに限定されず、また単独または併用して添加してもよい。
【００４１】
本発明に係るスチリル系シアニン色素を主成分として含有する記録層２は、図１〜４に示されるように、基板１、１’の面上に積層される。かかる記録層剤は、基板を侵さない塗布用溶媒として、例えば、メチルセロソルブ、エチルセロソルブ、メタノール、エタノール、イソプロパノール、ジアセトンアルコール、ジメチルホルムアミド、シクロヘキサノン、アセチルアセトン、テトラフルオロプロパノール、ジクロロエタン、ジオキサンなどの単独又は混合液を用いて色素を十分に溶解させ、一般的にスピンコート法等の常用手段により、グルーブが形成された成形基板上１、１’に成膜される。
【００４２】
この記録層２の厚さは約５０〜５００ｎｍ程度であり、好ましくは５０〜３００ｎｍ程度である。この厚さが５０ｎｍ未満では記録感度および反射率が不足し、理想的な記録ができない。一方、この厚さが５００ｎｍを超えるとトラッキング信号が得られなくなったり、ピットの重なりが生じる場合がある。この結果、ジッターが大きくなり、再生信号の波形歪みが生じやすく、クロストークの増大の原因となったりする。記録層２の膜厚は膜形成条件、色素濃度およびグルーブ形状を加味して、調整することができる。
【００４３】
記録膜２の上に設けられる金属反射層（光反射膜）３は、本発明に係る記録層２より高融点であり、反射率がレーザー光に対して５５％以上、好ましくは６０％以上有するＡｌ、Ａｕ、Ａｇ、Ｃｕ、Ｎｉ、Ｔｉおよびカルコゲナイド系金属からなる群から選ばれる単独または合金からなる金属薄膜で、膜厚は３０〜１５０ｎｍ、好ましくは５０〜１００ｎｍ程度である。この金属反射層３は、スパッタリング、真空蒸着、イオンプレーティング法等により積層される。
【００４４】
図１〜４に示すように金属反射層３上に設けられる保護膜４は、一般に光硬化性（紫外線硬化樹脂または可視硬化性樹脂）をスピンコート法をはじめ、スプレーコート法、グラビヤコート法等により塗設した後、紫外線または可視光を照射し、塗膜を硬化させて形成されたものである。更に、エポキシ樹脂、アクリル樹脂、シリコーン樹脂等を湿式法で形成させることができる。また、ＳｉＯｘ層等の無機膜をスパッタ、蒸着法等によって形成してもよく、更にはパリレン、ポリアミド、ポリイミド等の樹脂を蒸着、プラズマ等の方法によって重合させた高分子膜でもよい。また、シート状であってもよい。この保護膜４の膜厚は、０．５〜５０μｍ程度の厚さに設層すればよい。
【００４５】
図２および３における両面貼り合わせ媒体においては、ホットメルト型、紫外線・可視線硬化型をはじめとした接着剤および粘着テープなどで張り合わせて、両面記録／再生可能な高密度光記録媒体を得ることができる。
【００４６】
本発明の光記録媒体は特定の構造のスチリル系シアニン色素を主成分とした特定の記録層を基板上に設けた構成で、短波長レーザー５００〜７００ｎｍに対応し十分な高感度および高反射率を有し、記録特性に優れ、且つ再生劣化せず、長期保存性、信頼性に優れた高密度記録が達成され、またＤＶＤに準拠した光記録媒体が提供される。
【００４７】
【実施例】
以下に本発明を実施例より説明するが、本発明はこれらに限定されるものではない。
なお、以下の実施例において、基板は６ｍｍ厚で、グルーブのトラックピッチが０．７５μｍに形成されたポリカーボネート基板を使用した。
【００４８】
実施例１
前記式（Ｉ−２）で表されるスチリル系シアニン色素に対してクエンチャー（前記Ｑ３と前記Ｑ７とを２：１の重量比で混合）を１０重量％になるように添加し、混合溶媒液（エチルセロソルブ／エタノール／ジアセトンアルコール＝５：２：３の重量比）で混合して記録層剤を調製した。得られた記録層剤を５重量％の濃度にて超音波を用いて十分に溶解し、フィルターでろ過後、前記基板上にスピンコート法により塗布して、約６０ｎｍの厚さに均一に形成された記録層を得た。続いて、金属反射層をスパッタ法により、厚さ６０ｎｍのＡｌ−Ｔｉ合金薄膜として形成した。さらに、保護膜として、多官能性エポキシアクリレート系の紫外線硬化塗料をスピンコート法で塗布し、硬化させた。その際の膜厚は約６μｍであった。
単板の記録媒体は上述の方法で得た。両面型にするためには、接着層に紫外線硬化型の接着剤を使用し、低温圧着で保護層同士を対面に貼り合せて、所望の両面型光記録媒体を得た。
【００４９】
実施例２
スチリル系シアニン色素として、夫々前記式（Ｉ−２）と（Ｉ−１）で表されるをものを重量比２：１で複合化した系に、実施例１と同じクエンチャーを加えて、実施例１と同様の手段および構成で所望の光記録媒体を得た。
【００５０】
実施例３
スチリル系シアニン色素として、夫々前記式（Ｉ−４）と（Ｉ−８）で表されるものを重量比２：１で複合化した系に、クエンチャー（前記Ｑ１のＣｕ錯体と前記Ｑ７とを２：１の重量比で混合）を使用して、実施例１と同様の手段・構成で所望の光記録媒体を得た。
【００５１】
実施例４
スチリル系シアニン色素として、夫々前記式（Ｉ−１２）と（Ｉ−１）で表されるものを重量比１：１で複合化した系に、実施例１と同じクエンチャーを加えて、実施例１と同様の手段および構成で所望の光記録媒体を得た。
【００５２】
比較例１
レーザー吸収色素として、下記構造式、

で表される色素ＤＹ１（（株）日本感光色素研究所社製ＮＫ−４２８８）を使用し、実施例１と同様のクエンチャーを使用し、かつ実施例１と同様の手段・構成で所望の光記録媒体を得た。
【００５３】
比較例２
レーザー吸収色素として、下記構造式、

で表される色素ＤＹ２（（株）日本感光色素研究所社製ＮＫ−３８３）を使用し、実施例１と同様のクエンチャーを使用し、かつ実施例１と同様の手段・構成で所望の光記録媒体を得た。
【００５４】
比較例３
レーザー吸収色素として、前記構造式の色素ＤＹ２と下記構造式、

で表される色素ＤＹ３（（株）日本感光色素研究所社製ＮＫ−１９７７）を重量比２：１で複合化した系に、実施例１と同様のクエンチャーを使用し、かつ実施例１と同様の手段・構成で所望の光記録媒体を得た。
【００５５】
比較例４
レーザー吸収色素として、前記構造式の色素ＤＹ２と前記構造式の色素ＤＹ１を重量比１：１で複合化した系に、実施例１と同様のクエンチャーを使用し、かつ実施例１と同様の手段・構成で所望の光記録媒体を得た。
【００５６】
以上の実施例および比較例について、光記録媒体特性、すなわち反射率と再生信号特性（Ｃ／Ｎ，エラレート）を評価した。再生信号特性は、ディスクの線速度３．３ｍ／ｓで、発振波長６３５ｎｍの半導体レーザーを対物レンズの開口数（ＮＡ）０．６０で集光させ、記録Ｐｗで記録し、評価機を用いて評価した。また、初期特性と、長時間再生（１×１０^４回）後と高温・高湿度（８０℃、８０％、２４時間）後の加速耐光性とを試験し、これらの評価を行った。
【００５７】
その結果、比較例１は波長があわず評価ができなかった。しかし、その他の媒体は初期特性で反射率は５５％以上、Ｃ／Ｎ比は５２ｄＢ以上、エラーレートは１×１０^−５以下であった。
実施例１〜４は特にジッターは１５％位であるのに対し、比較例１、２はいずれも２０％以上であった。耐久試験後の測定の結果を下記の表１に示す。
【００５８】
【表１】

【００５９】
【発明の効果】
本発明の光記録媒体は、特定の構造のスチリル系シアニン色素を主成分とした特定の記録層を基板上に設けた構成で、短波長レーザー５００〜７００ｎｍに対応し十分な感度および反射率を有し、再生劣化、長期保存性、信頼性に優れ、ジッター成分を減少させることにより高密度記録が達成され、またＤＶＤの規格に準拠した光記録媒体である。
【図面の簡単な説明】
【図１】本発明の一例光記録媒体の概念的断面図である。
【図２】本発明の他の一例光記録媒体の概念的断面図である。
【図３】本発明の更に他の一例光記録媒体の概念的断面図である。
【図４】本発明の更に他の一例光記録媒体の概念的断面図である。
【図５】前記式（Ｉ−２）で表されるスチリル系シアニン色素の分光図である。
【符号の説明】
１ 基板
１’無グルーブ基板
２ 記録層（有機薄膜）
３ 金属反射層（光反射膜）
４ 保護膜
６ 記録変形層ピット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording medium that performs high-density writing (recording) and reading (reproduction) with a short-wavelength laser beam. In particular, by using a highly sensitive and reliable organic dye thin film whose light reflectance changes depending on the wavelength of the laser beam, it is possible to reduce the spot light and to record and reproduce information at a high density. The present invention relates to a write-once type optical recording medium compliant with the DVD standard.
[0002]
[Prior art]
Recordable optical information recording media are very widespread. In optical recording, since the medium and the recording / reproducing head are not in contact with each other, the recording medium has a feature that the recording medium does not wear and deteriorate. By making the spot diameter of the light beam smaller, it has attracted attention as a large-capacity information carrier. Development is underway. Such an optical information recording medium, for example, condenses a laser beam on the recording layer and converts it into thermal energy, and changes the properties of the recording film by melting, decomposing, removing, etc. (recording pits), and recording is not performed. Reproduction is performed by changing the amount of reflected light with the part.
[0003]
As the recording film, a chalcogenide-type metal film represented by tellurium was initially put into practical use, but it is harmful to the human body, the film formation is a dry method and the manufacturing cost is high, and the recording density is increased. As a result of the increasing need to perform recording, proposals and reports on media using recording layers based on organic dyes instead of recording layers composed of inorganic metal thin films typified by tellurium have increased. . The reason is that the recording layer mainly composed of organic dye has a lower reflectance than the metal recording layer,
(1) The recording film can be formed into a thin film by a low-cost wet method typified by a spin coating method.
(2) Excellent oxidation resistance and not corroded
(3) Since the thermal conductivity is lower than that of metal, the influence of heat does not reach the peripheral part compared to metal recording film, and local heating can be performed.
(4) Clearly shaped recording pits can be formed and high sensitivity can be achieved.
This is because it has many excellent properties.
[0004]
Further, structurally, an optical information recording having a so-called air sandwich structure in which an air layer is provided on a recording layer made of a conventionally used dye film, or a structure capable of obtaining a reproduction signal corresponding to the CD standard. Many media have been proposed (Japanese Patent Publication No. 3-759343, Japanese Patent Laid-Open No. 2-87341, Japanese Patent Laid-Open No. 5-67352, etc. and Nikkei Electronics, 1989, January 23, No. 469, page 107). .
[0005]
As an example of a medium structure conforming to the CD standard, a light absorbing layer made of an organic dye on a translucent resin substrate, a light reflecting layer such as Au directly or via a hard layer, and a resin protective layer in order. What is formed is known. That is, since a high reflectance of 65% or more cannot be obtained with only an organic dye film, a light absorbing layer made of an organic dye is formed on a translucent resin substrate and directly or via a hard layer. By forming a light reflecting layer typified by Au and further forming a resin protective layer thereon, an optical recording disk conforming to the CD standard is produced.
[0006]
When this optical recording disk is irradiated with laser light, the organic dye layer absorbs light, melts or decomposes, softens the substrate, mixes the dye material and the substrate at the interface, and finally deforms the interface. A recording pit is formed. In the recording deformation layer pit portion formed in this way, the reflectance changes with the optical phase difference as in the case of CD, and reading can be performed. Organic dyes used in these are squarylium dyes (Japanese Patent Laid-Open Nos. 56-46221, 63-218398, 1-178494, Japanese Laid-Open Patent Application No. 5-13947, Japanese Laid-Open Patent Application No. 7-44904). Naphthoquinone dyes (JP-A 61-290092, JP-A 62-432, JP-A 63-168201, JP-A-5-139047, etc.), azo dyes (JP 7-161069, JP-A-7-251567, JP-A-8-99467, etc.), phthalocyanine dyes (JP-A 57-82094, JP-A 57-82095, JP-A-7- 156550, JP-A-7-16068, JP-A-7-52544, etc.) and the following general formula (II),

(Where S¹And S²Each is an alkyl group, an aryl group or an alkoxyl group, and W¹And W²Represents a substitution of a halogen atom, a hydrogen atom, an alkyl group, an alkoxyl group, an aryl group, an alkoxysulfonyl group, a sulfonylalkyl group, a cyano group, etc.¹And Z²Are each a cyanine dye represented by a sulfur atom, an oxygen atom, a selenium atom, or a substituent such as ethylene) (Japanese Patent Laid-Open Nos. 59-24692, 2-87341, and 6-320869). JP-A-6-338059, JP-A-6-199045, JP-A-7-262611, JP-A-62-201288, JP-B-7-4981, JP-B-8-2547033 Etc.) are known.
[0007]
Of the dye systems described above, cyanine systems are mainly used from the viewpoints of high sensitivity, high S / N ratio, etc., and thermal characteristics and thinning. Among them, a dye having absorption and reflectance generally in the vicinity of 780 nm to 830 nm from the wavelength of the semiconductor laser in order to comply with CD, in which the methylene chain q at the center of the molecular structure in the above formula (II) is 2. Generally used a lot. However, there is a fatal problem that such a dye recording film cannot cope with the short wavelength laser for this purpose.
[0008]
In addition, it is said that there are problems with reproduction deterioration, long-term stability of the dye film, C / N ratio, jitter component, and the like. The reasons for this are (i) a phenomenon in which the dye itself deteriorates and fades due to heat accumulation in the recording film portion due to exposure of reading light over a long period of time, and (ii) recording in which the reading light should distinguish between a pit portion and a non-recording portion. Absorption at the boundary surface of the film, causing a phenomenon that the boundary surface is gradually melted or thermally deformed, and a phenomenon in which the pit contour is broken due to the same heat accumulation, (iii) When the dye is photoexcited In addition, oxidative degradation of the pigment due to singlet oxygen (dye fading) caused by energy transfer from the pigment to the oxygen present in the atmosphere, and (iv) as a degradation phenomenon during long-term storage, due to oxidation of natural light and cyanine pigment, etc. It is conceivable that the change in transmittance and the generation of noise are caused by the change in transmittance of the dye and the association / aggregation of the dyes due to oxygen, moisture, and the like. In order to solve this problem, various proposals have been conventionally made (for example, Japanese Patent Laid-Open Nos. 62-201288, 62-201289, 57-66541, 59). JP-A-124894, JP-A-59-203247, JP-A-62-133173, JP-A-63-198096, JP-A-59-21339, JP-A-57-11090, JP-A-60-44389, JP-A-60-71296, JP-A-63-1594, JP-A-57-11090, JP-A-5-38879, JP-A-7-262611 Gazette, Japanese Patent Publication No. 7-4981). However, the reality is that it has not yet been fully resolved.
[0009]
Furthermore, development of an optical recording medium having a high recording density conforming to the DVD-ROM standard is in progress. This is because the wavelength of the semiconductor laser is about 600 to 680 nm shorter than that for the current CD, and the wavelength of the light is shortened by using an SHG element or the like, and the objective lens is narrowed down to the laser diffraction limit to reduce the beam spot diameter. In this way, the recording density is increased.
[0010]
In order to develop such a dye material for DVD-ROM, attempts have been made to improve cyanine dyes for CDs represented by the general formula (II), and proposals for cyanine dyes for short wavelengths (for example, JP-A-5-38879, JP-A-6-40162, JP-A-6-320869, JP-A-6-186530, JP-A-6-199045, JP-A-7-262611, (Kaihei No. 8-306074, Japanese Patent Publication No. 21-21798, Japanese Patent Publication No. 7-4981).
[0011]
[Problems to be solved by the invention]
However, the recording layer does not have the sensitivity corresponding to the target wavelength, the stability (reliability) of the film, and the jitter component included in the reproduction signal due to thermal interference between adjacent pits when the density is increased. Many problems have not been solved.
[0012]
The present invention has been made in view of the above points, and an object of the present invention is to provide an organic dye having good optical characteristics, chemical, photochemical, physical, and thermal stability that can be used for a short-wavelength semiconductor laser (wavelength: 500 to 700 nm). By finding the thin film and medium structure, the optical recording medium has high sensitivity and excellent dye film stability, and has a high C / N ratio, especially in high-density recording, and reduces jitter components contained in the reproduced signal. It is an object of the present invention to provide an optical recording medium compatible with the DVD standard.
[0013]
[Means for Solving the Problems]
As a result of intensive studies on various dyes to solve the above problems, the present inventor has found that an optical recording medium comprising a recording layer containing a specific still cyanine dye as a main component has a short wavelength (500 to 700 nm). ), High sensitivity, long-term reliability with reduced degradation of reproduction, and reduced thermal interference and heat accumulation between pits at higher density, especially C / N ratio at higher density It was found that the jitter component can be reduced and the DVD can be used, and the present invention has been completed.
[0014]
That is, the present invention is as follows.
(1) In an optical recording medium in which at least a recording layer and a metal reflective layer are laminated on the surface of a resin substrate that is permeable to laser light on which grooves are formed,
The recording layer has the following general formula (I),

(Wherein R¹Is a substituent having an unsaturated bond group having 3 to 18 carbon atoms, R²Is an alkyl or aryl group, anion X⁻Is I⁻, Br⁻, ClO₄ ⁻, BF₄ ⁻, PF₄ ⁻, SbF₄ ⁻, CH₃SO₄ ⁻Or CH₃-C₆H₄-SO₃ ⁻, Y^1aAnd Y^1bAre both electron withdrawing groups or one is an electron withdrawing group and the other is a hydrogen atom, Y²Is an organic thin film corresponding to a short wavelength laser, the main component of which is a styryl cyanine dye represented by the formula (1).
[0015]
(2) In the optical recording medium, Y^1aAnd Y^1bAre both an electron-withdrawing group having a nitro group, a hydroxyl group, a carboxyl group, a carbonyl group, a cyano group, an alkoxycyano group, a halogen atom, or any of these at the terminal, or one of them is the electron-withdrawing group and the other is hydrogen. Atom, Y²Is -NH₂-N (R^Three)₂(Wherein R^ThreeIs an alkyl or aryl group having 1 to 7 carbon atoms); -N (R^FourR^Five)₂(Wherein R^FourAnd R^FiveAre each independently an alkyl group or aryl group having 1 to 7 carbon atoms;₂, -N (R^Three)₂(Wherein R^ThreeIs the same as above) or -N (R^FourR^Five)₂(Wherein R^FourAnd R^FiveAnd a nitrogen-containing compound derivative selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an aryl group, an arylalkenyl group, an arylazo group or an alkoxyl group; and a hydrazinocarbonyl group. This is an optical recording medium that is an electron donating group.
[0016]
(3) The optical recording medium is an optical recording medium in which the recording layer is an organic thin film composed of a composite system containing two or more styryl cyanine dyes represented by the general formula (I).
[0017]
(4) The optical recording medium is an optical recording medium in which the recording layer contains 1% or more of an oxygen quencher.
[0018]
(5) In the optical recording medium, Al, Au, Ag, Cu, Ni, Ti having a higher melting point than the recording layer and having a reflectance of 55% or more with respect to the wavelength of the laser beam on the recording layer. And an optical recording medium in which a metal reflective layer of a metal thin film made of a single or alloy selected from the group consisting of chalcogenide-based metals is laminated.
[0019]
(6) The optical recording medium, wherein a metal reflective layer and a protective layer are sequentially laminated on the recording layer.
[0020]
(7) In the optical recording medium, a recording layer and a metal reflection layer are sequentially laminated on a groove-formed substrate, and a single-sided substrate on which a protective layer is further laminated and a groove-free substrate are bonded with an adhesive. An optical recording medium.
[0021]
(8) Double-sided optical recording in which in the optical recording medium, a recording layer and a metal reflective layer are sequentially laminated on a substrate, and a single-sided type in which a protective layer is further laminated with an adhesive via a protective layer. It is a medium.
[0022]
(9) In the optical recording medium, an optical recording in which grooves are formed on both surfaces of a substrate at the time of molding, and a recording layer, a metal reflective layer, and a protective layer are sequentially stacked on both surfaces of the substrate. It is a medium.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The specific configuration of the present invention will be described below in detail with reference to the drawings.
1 to 4 show a configuration example of the optical recording medium of the present invention.
The illustrated substrate 1 has a disk shape, and tracking prepits or pregrooves are formed concentrically or spirally on one surface of the substrate 1 shown in FIGS. The substrate 1 having such pre-pits or pre-grooves is made of injection-molded resin from the viewpoint of productivity and the like, and preferably for recording laser light and reproducing light (about 500 to 700 nm) of semiconductor laser light, particularly 600 to 680 nm. , Formed from a resin that is substantially transparent (laser light transmittance of 85% or more). The thickness of the substrate 1 is about 1.0 to 1.5 mm in the configuration example shown in FIG. 1, and is about 0.5 to 0.65 mm in the type shown in FIGS.
[0024]
In the configuration example shown in FIG. 4, prepits or pregrooves are formed on both surfaces of the substrate 1 by simultaneous molding, and the thickness of the substrate 1 is about 1.0 to 1.5 mm.
[0025]
The diameter of the substrate 1 shown in FIGS. 1 to 4 is about 50 to 120 mm. The resin constituting the substrate 1 is not particularly limited, but from the viewpoint of moldability and light transmittance, a thermoplastic resin such as polycarbonate resin, polyacrylic resin, polyester resin, amorphous olefin resin, TPX, arton resin, etc. is the main component. And
[0026]
The track pitch of the substrate 1 is 0.7 to 1.6 μm. The depth of the groove is used for tracking control, information holding, and the like depending on the phase of the laser beam. The depth of the groove is about 50 to 230 nm, preferably about 70 to 200 nm. If the groove is too shallow, the deformation rate of the groove bottom surface and the effect of deformation on the metal reflecting film are likely to increase, and it becomes easy to induce reproduction signal distortion, and the C / N ratio tends to decrease and the jitter increases, and the modulation degree is increased. Causes it to become smaller. On the other hand, when the groove is too deep, the deformation amount of the groove bottom surface of the recording mark portion becomes unstable and jitter increases. This increases the wavelength dependency of the reproduction signal and tracking signal. Therefore, the depth of the groove is important with respect to the wavelength of the semiconductor laser light during high-density recording, and it is necessary to optimize the depth, shape, etc. according to the characteristics of the organic thin film of the recording layer 2, film formability, etc. Yes, the material structure and composition of the recording layer 2 greatly affect the groove.
[0027]
The recording layer 2 formed on the substrates 1 and 1 'is an organic thin film mainly composed of a styryl cyanine dye represented by the general formula (I). All of the styryl cyanine dyes according to the present invention have an absorption / reflection wavelength at 500 to 700 nm when thinned, and have sufficient sensitivity and reflectivity for the target laser wavelength (600 to 680 nm). .
[0028]
In particular, the substituent R of the styryl cyanine dye represented by the general formula (I)¹Is a substituent having an unsaturated bond group of 3 to 18 carbon atoms, preferably 3 to 9 positions. Preferred examples include allyl, vinyl, arylidene, arylenyloxy, crotonoyl, styryl, vinylidene, vinylene, methylidyne, acryloxy, Examples include methallyloxy, isopropenyl, ethynyl, butenyl, etc., and such groups affect the solubility, and especially the compatibility between the film formability and the surface of the substrate is very good and the stability is improved. .
[0029]
R¹Introducing an unsaturated bond group into Y^1aAnd Y^1bAre both electron withdrawing groups or one of them is an electron withdrawing group and the other is a hydrogen atom, preferably both are nitro, hydroxyl, carboxyl, carbonyl, cyano, alkoxycyano, halogen atoms or any of these Or an electron withdrawing group having one of them at the terminal, or one of the electron withdrawing groups and the other is a hydrogen atom. Y²Is an electron donating group, preferably -NH₂-N (R^Three)₂(Wherein R^ThreeIs an alkyl or aryl group having 1 to 7 carbon atoms); -N (R^FourR^Five)₂(Wherein R^FourAnd R^FiveAre each independently an alkyl group or aryl group having 1 to 7 carbon atoms;₂, -N (R^Three)₂(Wherein R^ThreeIs the same as above) or -N (R^FourR^Five)₂(Wherein R^FourAnd R^FiveAnd a nitrogen-containing compound derivative selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an aryl group, an arylalkenyl group, an arylazo group or an alkoxyl group; and a hydrazinocarbonyl group. Electron donating group of the group. By introducing these substituents, for example, the spectrogram of a styryl cyanine dye represented by the following formula (I-2) becomes excellent in optical properties as shown in FIG. Therefore, a high C / N ratio can be obtained from the viewpoint that a high sensitivity, a high S / N ratio, and a uniform thin film can be easily obtained. Further, aggregation of the dye, association phenomenon, and the like can be suppressed by making the styryl cyanine dye according to the present invention into a thin film by compounding or the like. With the above effects, high sensitivity, a high S / N ratio, and a high C / N can be obtained, and an optical recording medium excellent in uniform film forming stability and reliability can be obtained.
[0030]
For styryl cyanine dyes according to the present invention, refer to known synthesis methods (eg, US Pat. No. 2,734,900, US Pat. No. 2,112,2139, US Pat. No. 2,887,479, etc.). Specific examples are shown below.
[0031]

[0032]

[0033]

[0034]

[0035]
The styryl cyanine dye according to the present invention may be used alone, but by combining two or more, the spectrum, for example, the absorption of laser light, the reflectance, etc. can be adjusted, and the film thickness can be further reduced. The stability of the film in an amorphous state can be obtained, and from such functions, high sensitivity, suppression of jitter components, and prevention of noise generation can be performed, and long-term storage stability is improved.
[0036]
The recording layer 2 may contain 1% or more, preferably 3 to 20%, of an oxygen quencher (light stabilizer) together with such a dye. If the content of the oxygen quencher in the recording layer is too large, the quencher may bleed and cause noise. This quencher captures radicals generated by the deterioration of the styryl cyanine dye caused by ultraviolet rays and laser light, and stops the chain reaction. Thereby, the light stability can be improved, and in particular, decolorization due to reproduction light can be prevented. As a result of the above, the recording layer according to the present invention can realize long-term storage, can suppress the flow of the film due to heat generated by light, and can suppress the generation of noise and the increase in jitter.
[0037]
The oxygen quencher used together with the styryl cyanine dye according to the present invention can be used alone or in combination, and is not particularly limited, but the following examples are generally used.
[0038]
Metal complex system
Q1: Bis (4-tetra-butyl-1,2-dithiophenolate) M-tetra-n-butylammonium (M is Cu, Co, Ni, Fe, etc.)
BBT series manufactured by Sumitomo Seika Co., Ltd.
Q2: Bis [4- (diethylamino) -α, β-stilbenylthiolate] nickel
NKX-114 manufactured by Nippon Sensitive Dye Research Co., Ltd.
Q3: bis [3-methoxy-4- (2-methoxyoxyoxy) -2'-chloro-α, β-stilbenethiolate] nickel
NKX-1199 manufactured by Nippon Sensitive Dye Research Co., Ltd.
Q4: 1,2-benzenedithiol nickel complex
Mitsui Toatsu Chemical Co., Ltd. PA-1006 etc.
[0039]
Amine / ammonium salt system
Q5: Bisiminium salt
IRG-03 manufactured by Nippon Kayaku Co., Ltd.
Q6: N, N, N ′, N ″ -tetrakis (p-dibutylaminophenyl) p-phenylenediamine
NIR-AM1 manufactured by Teikoku Chemical Co., Ltd.
Q7: 4-nitroso-4 '-(dimethylamino) diphenylamine
NKX-1549 manufactured by Nippon Sensitive Dye Research Co., Ltd.
[0040]
The oxygen quencher is not particularly limited to those of these specific examples, and may be added alone or in combination.
[0041]
The recording layer 2 containing the styryl cyanine dye according to the present invention as a main component is laminated on the surfaces of the substrates 1 and 1 'as shown in FIGS. Such a recording layer agent is a coating solvent that does not attack the substrate, for example, methyl cellosolve, ethyl cellosolve, methanol, ethanol, isopropanol, diacetone alcohol, dimethylformamide, cyclohexanone, acetylacetone, tetrafluoropropanol, dichloroethane, dioxane, Alternatively, the dye is sufficiently dissolved using a mixed solution, and is generally formed on the molded substrate 1 or 1 ′ on which the groove is formed by a conventional means such as a spin coating method.
[0042]
The thickness of the recording layer 2 is about 50 to 500 nm, preferably about 50 to 300 nm. If the thickness is less than 50 nm, recording sensitivity and reflectance are insufficient, and ideal recording cannot be performed. On the other hand, if the thickness exceeds 500 nm, tracking signals may not be obtained or pits may overlap. As a result, the jitter becomes large, the waveform distortion of the reproduced signal is likely to occur, and the crosstalk may increase. The film thickness of the recording layer 2 can be adjusted in consideration of the film forming conditions, the dye concentration, and the groove shape.
[0043]
The metal reflection layer (light reflection film) 3 provided on the recording film 2 has a higher melting point than the recording layer 2 according to the present invention, and has a reflectance of 55% or more, preferably 60% or more with respect to the laser beam. It is a metal thin film made of a single material or an alloy selected from the group consisting of Al, Au, Ag, Cu, Ni, Ti and chalcogenide-based metals, and the film thickness is about 30 to 150 nm, preferably about 50 to 100 nm. The metal reflective layer 3 is laminated by sputtering, vacuum deposition, ion plating method or the like.
[0044]
As shown in FIGS. 1 to 4, the protective film 4 provided on the metal reflective layer 3 is generally made of a photo-curable (ultraviolet curable resin or visible curable resin) spin coating method, spray coating method, gravure coating method, or the like. After coating, the film is formed by irradiating with ultraviolet rays or visible light to cure the coating film. Furthermore, an epoxy resin, an acrylic resin, a silicone resin, or the like can be formed by a wet method. In addition, an inorganic film such as a SiOx layer may be formed by sputtering, vapor deposition, or the like, or a polymer film obtained by polymerizing a resin such as parylene, polyamide, or polyimide by vapor deposition, plasma, or the like. Moreover, a sheet form may be sufficient. The protective film 4 may be formed to a thickness of about 0.5 to 50 μm.
[0045]
2 and 3, a high-density optical recording medium capable of double-sided recording / reproduction is obtained by pasting together with an adhesive and an adhesive tape such as a hot-melt type, an ultraviolet ray / visible ray curable type. Can do.
[0046]
The optical recording medium of the present invention has a structure in which a specific recording layer mainly composed of a styryl cyanine dye having a specific structure is provided on a substrate, and has sufficient sensitivity and high reflectance corresponding to a short wavelength laser of 500 to 700 nm. In addition, high-density recording with excellent recording characteristics, no reproduction deterioration, long-term storage stability and reliability is achieved, and an optical recording medium compliant with DVD is provided.
[0047]
【Example】
The present invention will be described below with reference to examples, but the present invention is not limited thereto.
In the following examples, a polycarbonate substrate having a thickness of 6 mm and a groove track pitch of 0.75 μm was used.
[0048]
Example 1
A quencher (mixed Q3 and Q7 in a 2: 1 weight ratio) is added to the styryl cyanine dye represented by the formula (I-2) so as to be 10% by weight, and a mixed solvent The recording layer agent was prepared by mixing in a liquid (ethyl cellosolve / ethanol / diacetone alcohol = 5: 2: 3 weight ratio). The obtained recording layer agent is sufficiently dissolved using ultrasonic waves at a concentration of 5% by weight, filtered through a filter, and then applied onto the substrate by spin coating to form a uniform thickness of about 60 nm. The obtained recording layer was obtained. Subsequently, a metal reflective layer was formed as an Al—Ti alloy thin film having a thickness of 60 nm by sputtering. Furthermore, as a protective film, a polyfunctional epoxy acrylate UV curable coating was applied by a spin coating method and cured. The film thickness at that time was about 6 μm.
A single-plate recording medium was obtained by the method described above. In order to obtain a double-sided type, an ultraviolet curable adhesive was used for the adhesive layer, and the protective layers were bonded to each other by low-temperature pressure bonding to obtain a desired double-sided optical recording medium.
[0049]
Example 2
As a styryl cyanine dye, the same quencher as in Example 1 was added to a system in which the compounds represented by the above formulas (I-2) and (I-1) were combined at a weight ratio of 2: 1. A desired optical recording medium was obtained by the same means and configuration as in Example 1.
[0050]
Example 3
As a styryl cyanine dye, a system in which the compounds represented by the above formulas (I-4) and (I-8) are combined at a weight ratio of 2: 1, a quencher (the Cu complex of Q1 and Q7 and Were mixed at a weight ratio of 2: 1) to obtain a desired optical recording medium by the same means and configuration as in Example 1.
[0051]
Example 4
As a styryl cyanine dye, the same quencher as in Example 1 was added to a system in which the compounds represented by the formulas (I-12) and (I-1) were combined at a weight ratio of 1: 1. A desired optical recording medium was obtained by the same means and configuration as in Example 1.
[0052]
Comparative Example 1
As a laser absorbing dye, the following structural formula,

The dye DY1 represented by the formula (NK-4288 manufactured by Nippon Sensitive Dye Research Co., Ltd.) is used, the same quencher as in Example 1 is used, and the same means and configuration as in Example 1 are used. An optical recording medium was obtained.
[0053]
Comparative Example 2
As a laser absorbing dye, the following structural formula,

The dye DY2 represented by the formula (NK-383, manufactured by Japan Photosensitive Dye Research Co., Ltd.), the same quencher as in Example 1, and the same means and configuration as in Example 1 are used. An optical recording medium was obtained.
[0054]
Comparative Example 3
As the laser-absorbing dye, the dye DY2 of the above structural formula and the following structural formula,

The same quencher as in Example 1 was used in a system in which a dye DY3 represented by the formula (NK-1977, manufactured by Nippon Sensitive Dye Research Co., Ltd.) was combined at a weight ratio of 2: 1. A desired optical recording medium was obtained by the same means and configuration as in Example 1.
[0055]
Comparative Example 4
As a laser absorbing dye, a quencher similar to that in Example 1 is used in a system in which the dye DY2 having the above structural formula and the dye DY1 having the above structural formula are combined at a weight ratio of 1: 1, and the same as in Example 1. A desired optical recording medium was obtained by means and configuration.
[0056]
The optical recording medium characteristics, that is, the reflectance and the reproduction signal characteristics (C / N, ellarate) were evaluated for the above examples and comparative examples. The reproduction signal characteristics are as follows: a semiconductor laser with an oscillation wavelength of 635 nm is condensed with a numerical aperture (NA) of 0.60 of the objective lens at a linear velocity of the disk of 3.3 m / s, and recorded with a recording Pw. evaluated. Also, initial characteristics and long-time playback (1 × 10⁴And accelerated light resistance after high temperature and high humidity (80 ° C., 80%, 24 hours) were evaluated.
[0057]
As a result, Comparative Example 1 could not be evaluated because the wavelength was not sufficient. However, other media have initial characteristics and reflectivity of 55% or more, C / N ratio of 52 dB or more, and error rate of 1 × 10.^-5It was the following.
In Examples 1 to 4 in particular, the jitter was about 15%, while in Comparative Examples 1 and 2, both were 20% or more. The measurement results after the durability test are shown in Table 1 below.
[0058]
[Table 1]

[0059]
【The invention's effect】
The optical recording medium of the present invention has a structure in which a specific recording layer mainly composed of a styryl cyanine dye having a specific structure is provided on a substrate, and has sufficient sensitivity and reflectance corresponding to a short wavelength laser of 500 to 700 nm. It is an optical recording medium that is excellent in reproduction deterioration, long-term storage stability and reliability, achieves high density recording by reducing jitter components, and conforms to the DVD standard.
[Brief description of the drawings]
FIG. 1 is a conceptual cross-sectional view of an example optical recording medium of the present invention.
FIG. 2 is a conceptual cross-sectional view of another example optical recording medium of the present invention.
FIG. 3 is a conceptual cross-sectional view of still another example optical recording medium of the present invention.
FIG. 4 is a conceptual cross-sectional view of still another example optical recording medium of the present invention.
FIG. 5 is a spectroscopic view of a styryl cyanine dye represented by the formula (I-2).
[Explanation of symbols]
1 Substrate
1 'no groove substrate
2 Recording layer (organic thin film)
3 Metal reflective layer (light reflective film)
4 Protective film
6 Recording deformation layer pit

Claims (9)

In an optical recording medium in which at least a recording layer and a metal reflective layer are laminated on the surface of a resin substrate that is permeable to laser light on which grooves are formed,
The recording layer has the following general formula (I),

Wherein R ¹ is a substituent having an unsaturated bond group having 3 to 18 carbon atoms, R ² is an alkyl group or an aryl group, and the anion X ⁻ is I ⁻ , Br ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , PF ₄ ⁻ , SbF ₄ ⁻ , CH ₃ SO ₄ ^— or CH ₃ —C ₆ H ₄ —SO ₃ ⁻ , Y ^1a and Y ^1b are both electron withdrawing groups or one is an electron withdrawing group and the other is a hydrogen atom. , Y ² represents an electron donating group), and an organic thin film corresponding to a short wavelength laser, the main component of which is a styryl cyanine dye. Y ^1a and Y ^1b are both nitro group, a hydroxyl group, a carboxyl group, a carbonyl group, shea Anomoto, alkoxy cyano group, or a halogen atom or an electron withdrawing group terminated with any of these, or one of the electronic An attractive group and the other is a hydrogen atom; Y ² is —NH ₂ ; —N (R ³ ) ₂ (wherein R ³ is an alkyl or aryl group having 1 to 7 carbon atoms); —N (R ⁴ R ⁵ ) ₂ (wherein R ⁴ and R ⁵ are each independently an alkyl group or aryl group having 1 to 7 carbon atoms); —NH ₂ , —N (R ³ ) ₂ (wherein R ³ Are the same as those described above) or —N (R ⁴ R ⁵ ) ₂ (wherein R ⁴ and R ⁵ are the same as those described above), an alkyl group having 1 to 18 carbon atoms, an aryl group, an aryl alkenyl group, an arylazo group or an alkoxyl group; and hydrazino The optical recording medium of claim 1, wherein the electron donating group of the nitrogen-containing compound derivative and an alkyl group selected from carbonyl group or Ranaru group. 3. The optical recording medium according to claim 1, wherein the recording layer is an organic thin film composed of a composite system containing two or more styryl cyanine dyes represented by the general formula (I). 4. The optical recording medium according to claim 1, wherein the recording layer contains 1% or more of an oxygen quencher. On the recording layer, selected from the group consisting of Al, Au, Ag, Cu, Ni, Ti and chalcogenide-based metals having a melting point higher than that of the recording layer and having a reflectance of 55% or more with respect to the wavelength of the laser beam. The optical recording medium according to claim 1, wherein a metal reflective layer of a metal thin film made of a single material or an alloy is laminated. The optical recording medium according to claim 1, wherein a metal reflective layer and a protective layer are sequentially laminated on the recording layer. The recording layer and the metal reflective layer are sequentially laminated on the substrate on which the groove is formed, and the single-sided substrate on which the protective layer is further laminated and the non-grooved substrate are bonded with an adhesive. An optical recording medium according to claim 1. The double-sided type according to any one of claims 1 to 5, wherein a recording layer and a metal reflective layer are sequentially laminated on a substrate, and a single-sided type obtained by further laminating a protective layer is bonded with an adhesive via a protective layer. The optical recording medium described. The double-sided type according to any one of claims 1 to 5, wherein grooves are formed on both sides of the substrate at the time of molding, and a recording layer, a metal reflective layer, and a protective layer are sequentially laminated on both sides of the substrate. An optical recording medium according to claim 1.

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