JP4238518B2 - Optical recording medium and manufacturing method thereof - Google Patents

Description

【００３３】
（環Ａ¹及びＡ²は、各々独立に置換基を有していてもよい含窒素芳香族複素環であり、環Ｂ¹及びＢ²は、各々独立に置換基を有していてもよい芳香族環である。Ｘは、少なくとも２個のフッ素原子で置換されている炭素数１〜６のアルキル基である。）で表される化合物が好ましい。なお、この色素は、構造式から予想されるように、記録時に色素の分解によりＳＯ₂等の腐食性ガスが発生する。しかしながら、本発明の光記録媒体は、その反射層の耐食性がきわめて高いので、この腐食性ガスによって腐食を受けることがなく、長期にわたり保存安定性に優れる。
【００３４】
本発明の記録層に使用される有機色素は、３５０〜９００ｎｍ程度の可視光〜近赤外域に最大吸収波長λｍａｘを有し、青色〜近赤外線レーザでの記録に適する色素化合物が好ましい。通常ＣＤ−Ｒに用いられるような波長７７０〜８３０ｎｍ程度の近赤外レーザや、ＤＶＤ−Ｒに用いられるような波長６２０〜６９０ｎｍ程度の赤色レーザ、あるいは波長４１０ｎｍや５１５ｎｍなどのいわゆるブルーレーザなどでの記録に適する色素がより好ましい。
【００３５】
色素は一種でもよいし、同じ種類のものや異なる種類のものを二種以上混合して用いても良い。さらに、上記複数の波長の記録光に対し、各々での記録に適する色素を併用して、複数の波長域でのレーザ光による記録に対応する光記録媒体とすることもできる。
また記録層は、記録層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。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。
【００３６】
さらに本発明の記録層には、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。
【００３７】
記録層の膜厚は、記録方法などにより適した膜厚が異なるため、特に限定するものではないが、十分な変調度を得るためには通常５ｎｍ以上が好ましく、より好ましくは１０ｎｍ以上であり、特に好ましくは２０ｎｍ以上である。但し、本発明においては適度に光を透過させるためには厚すぎない必要があるため、通常３μｍ以下であり、好ましくは１μｍ以下、より好ましくは２００ｎｍ以下である。記録層の膜厚は通常、溝部とランド部で異なるが、本発明において記録層の膜厚は基板の溝部における膜厚を言う。
【００３８】
記録層の成膜方法としては、真空蒸着法、スパッタリング法、ドクターブレード法、キャスト法、スピンコート法、浸漬法等一般に行われている薄膜形成法が挙げられるが、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、塗布法より真空蒸着法の方が好ましい。
【００３９】
スピンコート法による成膜の場合、回転数は１０〜１５０００ｒｐｍが好ましく、スピンコートの後、加熱あるいは溶媒蒸気にあてる等の処理を行っても良い。
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。例えば、ジアセトンアルコール、３−ヒドロキシ−３−メチル−２−ブタノン等のケトンアルコール系溶媒；メチルセロソルブ、エチルセロソルブ等のセロソルブ系溶媒；ｎ−ヘキサン、ｎ−オクタン等の鎖状炭化水素系溶媒；シクロヘキサン、メチルシクロヘキサン、エチルシクロヘキサン、ジメチルシクロヘキサン、ｎ−ブチルシクロヘキサン、ｔｅｒｔ−ブチルシクロヘキサン、シクロオクタン等の環状炭化水素系溶媒；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；乳酸メチル、乳酸エチル、２−ヒドロキシ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が挙げられる。
【００４０】
真空蒸着法の場合は、例えば有機色素と、必要に応じて各種添加剤等の記録層成分を、真空容器内に設置されたるつぼに入れ、真空容器内を適当な真空ポンプで１０^-2〜１０^-5Ｐａ程度にまで排気した後、るつぼを加熱して記録層成分を蒸発させ、るつぼと向き合って置かれた基板上に蒸着させることにより、記録層を形成する。
（４）第２色素記録層５
第２色素記録層５は、通常ＣＤ−Ｒや片面型ＤＶＤ−Ｒ等に用いられる光記録媒体に用いる記録層より高感度である必要がある。本発明においては、入射した光ビームのパワーが半透明反射層の存在等で２分され、第１色素記録層の記録と第２色素記録層の記録とに振り分けられるため、約半分のパワーで記録するために、特に感度が高い必要があるのである。
【００４１】
また、良好な記録再生特性を実現するためには低発熱で高屈折率な色素であることが望ましい。
更に、第２色素記録層５と反射層６との組合せにおいて、光の反射及び吸収を適切な範囲とすることが望ましい。記録感度を高くし、かつ記録時の熱干渉を小さくできる。
【００４２】
第２色素記録層５の材料、成膜方法等についてはほぼ第１色素記録層２と同様に説明されるため、異なる点のみ説明する。
記録層の膜厚は、記録方法などにより適した膜厚が異なるため、特に限定するものではないが、十分な変調度を得るためには通常１０ｎｍ以上が好ましく、より好ましくは３０ｎｍ以上であり、特に好ましくは５０ｎｍ以上である。但し、適度な反射率を得るためには厚すぎない必要があるため、通常３μｍ以下であり、好ましくは１μｍ以下、より好ましくは２００ｎｍ以下である。
【００４３】
第１色素記録層２と第２色素記録層５に用いる材料は同じでも良いし異なっていてもよい。
（５）半透明反射層３
半透明反射層３は、光の吸収が小さく、光透過率が４０％以上あり、かつ適度な光反射率がある必要がある。例えば、反射率の高い金属を薄く設けることにより適度な透過率を持たせることができる。また、ある程度の耐食性があることが望ましい。更に、中間樹脂層４の浸み出しにより第１色素記録層２が影響されないよう遮断性を持つことが望ましい。
【００４４】
高透過率を確保するために、半透明反射層３の厚さは通常、５０ｎｍ以下が好適である。より好適には３０ｎｍ以下である。更に好ましくは２０ｎｍ以下である。但し、第１色素記録層２が中間樹脂層４により影響されないために、ある程度の厚さが必要であり、通常３ｎｍ以上とする。より好ましくは５ｎｍ以上とする。
【００４５】
半透明反射層３の材料としては、再生光の波長で反射率が適度に高いもの、例えば、Ａｕ、Ａｌ、Ａｇ、Ｃｕ、Ｔｉ、Ｃｒ、Ｎｉ、Ｐｔ、Ｔａ、Ｐｄ、Ｍｇ、Ｓｅ、Ｈｆ、Ｖ、Ｎｂ、Ｒｕ、Ｗ、Ｍｎ、Ｒｅ、Ｆｅ、Ｃｏ、Ｒｈ、Ｉｒ、Ｚｎ、Ｃｄ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｔｅ、Ｐｂ、Ｐｏ、Ｓｎ、Ｂｉ及び希土類金属などの金属及び半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は反射率が高く半透明反射層３の材料として適している。これらを主成分とする以外に他成分を含んでいても良い。
【００４６】
なかでもＡｇを主成分としているものはコストが安い点、反射率が高い点から特に好ましい。ここで主成分とは含有率が５０％以上のものをいう。
半透明反射層３は膜厚が薄く、膜の結晶粒が大きいと再生ノイズの原因となるため、結晶粒が小さい材料を用いるのが好ましい。純銀は結晶粒が大きい傾向があるためＡｇは合金として用いるのが好ましい。
【００４７】
中でもＡｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属よりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有することが好ましい。Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属のうち２種以上含む場合は、各々０．１〜１５原子％でもかまわないが、それらの合計が０．１〜１５原子％であることが好ましい。
【００４８】
特に好ましい合金組成は、Ａｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕよりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有し、かつ少なくとも１種の希土類元素を０．１〜１５原子％含有するものである。希土類金属の中では、ネオジウムが特に好ましい。具体的には、ＡｇＰｄＣｕ、ＡｇＣｕＡｕ、ＡｇＣｕＡｕＮｄ、ＡｇＣｕＮｄなどである。
【００４９】
半透明反射層３としてはＡｕのみからなる層は結晶粒が小さく、耐食性に優れ好適である。ただし、Ａｇ合金に比べて高価である。
また、半透明反射層３としてＳｉからなる層を用いることも可能である。
金属以外の材料で低屈折率薄膜と高屈折率薄膜を交互に積み重ねて多層膜を形成し、反射層として用いることも可能である。
【００５０】
半透明反射層３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中間層、接着層を設けることもできる。
（６）反射層６
反射層６は、高反射率である必要がある。また、高耐久性であることが望ましい。
【００５１】
高反射率を確保するために、反射層６の厚さは通常、２０ｎｍ以上が好適である。より好適には３０ｎｍ以上である。更に好ましくは５０ｎｍ以上である。但し、記録感度を上げるためにはある程度薄いことが好ましく、通常４００ｎｍ以下とする。より好ましくは３００ｎｍ以下とする。
反射層６の材料としては、再生光の波長で反射率の十分高いもの、例えば、Ａｕ、Ａｌ、Ａｇ、Ｃｕ、Ｔｉ、Ｃｒ、Ｎｉ、Ｐｔ、Ｔａ及びＰｄの金属を単独あるいは合金にして用いることが可能である。この中でもＡｕ、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他成分として下記のものを含んでいても良い。他成分の例としては、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及び希土類金属などの金属及び半金属を挙げることができる。
【００５２】
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、更に後で述べる印刷受容層を設ける場合には地色が白く美しいものが得られる点等から特に好ましい。ここで主成分とは含有率が５０％以上のものをいう。
反射層６は高耐久性（高耐食性）を確保するため、Ａｇは純銀よりもＡｇは合金として用いるのが好ましい。
【００５３】
中でもＡｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属よりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有することが好ましい。Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属のうち２種以上含む場合は、各々０．１〜１５原子％でもかまわないが、それらの合計が０．１〜１５原子％であることが好ましい。
【００５４】
特に好ましい合金組成は、Ａｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕよりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有し、かつ少なくとも１種の希土類元素を０．１〜１５原子％含有するものである。希土類金属の中では、ネオジウムが特に好ましい。具体的には、ＡｇＰｄＣｕ、ＡｇＣｕＡｕ、ＡｇＣｕＡｕＮｄ、ＡｇＣｕＮｄなどである。
【００５５】
反射層６としてはＡｕのみからなる層は高耐久性（高耐食性）が高く好適である。ただし、Ａｇ合金に比べて高価である。
金属以外の材料で低屈折率薄膜と高屈折率薄膜を交互に積み重ねて多層膜を形成し、反射層として用いることも可能である。
反射層６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中間層、接着層を設けることもできる。
（７）中間樹脂層４
中間樹脂層４は、透明である必要があるほか、凹凸により溝やピットが形成可能である必要がある。また接着力が高く、硬化接着時の収縮率が小さいと媒体の形状安定性が高く好ましい。
【００５６】
そして、中間樹脂層４は、色素記録層５にダメージを与えない材料からなることが望ましい。但し、中間樹脂層４は通常、樹脂からなるため色素記録層５と相溶しやすく、これを防ぎダメージを抑えるために両層のあいだに後述のバッファー層を設けることが望ましい。
さらに、中間樹脂層４は、半透明反射層３にダメージを与えない材料からなることが望ましい。但し、ダメージを抑えるために両層のあいだに後述のバッファー層を設けることもできる。
【００５７】
本発明において、保護層の膜厚は正確に制御することが好ましい。保護層の膜厚は、通常５μｍ以上が好ましい。２層の記録層に別々にフォーカスサーボをかけるためには両記録層のあいだにある程度の距離がある必要がある。フォーカスサーボ機構にもよるが、通常５μｍ以上、好ましくは１０μｍ以上が必要である。一般に、対物レンズの開口数が高いほどその距離は小さくてよい傾向がある。
【００５８】
但しあまり厚いと２層の記録層にフォーカスサーボを合わせるのに時間を要し、また対物レンズの移動距離も長くなるため好ましくない。また硬化に時間を要し生産性が低下するなどの問題があるため、通常、１００μｍ以下が好ましい。中間樹脂層４には凹凸が螺旋状又は同心円状に設けられ、溝及びランドを形成する。通常、このような溝及び／又はランドを記録トラックとして、色素記録層５に情報が記録・再生される。通常、色素記録層５は塗布形成されるので溝部で厚膜となり記録再生に適する。本発明においては中間樹脂層４の溝部、即ち光の入射方向に対して凸部を記録トラック１２とするのが好ましい。ここで、凹部、凸部はそれぞれ光の入射方向に対する凹部、凸部を言う。通常、溝幅は２００〜５００ｎｍ程度であり、溝深さは１２０〜２５０ｎｍ程度である。また記録トラックが螺旋状である場合、トラックピッチは０．１〜２．０μｍ程度であることが好ましい。この他に必要に応じ、ランドプリピット等の凹凸ピットを有してもよい。
【００５９】
このような凹凸は、コストの観点から、凹凸を持つ樹脂スタンパ等から光硬化性樹脂などの硬化性樹脂に転写、硬化させて製造するのが好ましい。以下、このような方法を２Ｐ法と称することがある。
中間樹脂層４の材料としては、例えば、熱可塑性樹脂、熱硬化性樹脂、電子線硬化性樹脂、紫外線硬化性樹脂（遅延硬化型を含む）等を挙げることができる。
【００６０】
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調製し、これを塗布し、乾燥することによって形成することができる。紫外線硬化性樹脂は、そのままもしくは適当な溶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、紫外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。紫外線硬化性樹脂には様々な種類があり、透明であればいずれも用いうる。またそれらの材料を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。
【００６１】
塗布方法としては、記録層と同様にスピンコート法やキャスト法等の塗布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。或いは、粘度の高い樹脂はスクリーン印刷等によっても塗布形成できる。紫外線硬化性樹脂は、生産性を２０〜４０℃において液状であるものを用いると、溶媒を用いることなく塗布でき好ましい。また、粘度は２０〜１０００ｍＰａ・ｓとなるように調製するのが好ましい。
【００６２】
さて、紫外線硬化性接着剤としては、ラジカル系紫外線硬化性接着剤とカチオン系紫外線硬化性接着剤があるが、いずれも使用可能である。
ラジカル系紫外線硬化性接着剤としては、公知の全ての組成物を用いることができ、紫外線硬化性化合物と光重合開始剤を必須成分として含む組成物が用いられる。紫外線硬化性化合物としては、単官能（メタ）アクリレートや多官能（メタ）アクリレートを重合性モノマー成分として用いることができる。これらは、各々、単独または２種類以上併用して用いることができる。ここで、本発明では、アクリレートとメタアクリレートとを併せて（メタ）アクリレートと称する。
【００６３】
本発明に使用できる重合性モノマーとしては例えば以下のものが挙げられる。単官能（メタ）アクリレートとしては例えば、置換基としてメチル、エチル、プロピル、ブチル、アミル、２−エチルヘキシル、オクチル、ノニル、ドデシル、ヘキサデシル、オクタデシル、シクロヘキシル、ベンジル、メトキシエチル、ブトキシエチル、フェノキシエチル、ノニルフェノキシエチル、テトラヒドロフルフリル、グリシジル、２−ヒドロキシエチル、２−ヒドロキシプロピル、３−クロロ−２−ヒドロキシプロピル、ジメチルアミノエチル、ジエチルアミノエチル、ノニルフェノキシエチルテトラヒドロフルフリル，カプロラクトン変性テトラヒドロフルフリル、イソボルニル，ジシクロペンタニル，ジシクロペンテニル，ジシクロペンテニロキシエチル等の如き基を有する（メタ）アクリレート等が挙げられる。
【００６４】
また、多官能（メタ）アクリレートとしては例えば、１，３−ブチレングリコール、１，４−ブタンジオール、１，５−ペンタンジオール、３−メチル−１，５−ペンタンジオール、１，６−ヘキサンジオール、ネオペンチルグリコール、１，８−オクタンジオール、１，９−ノナンジオール、トリシクロデカンジメタノール、エチレングリコール、ポリエチレングリコール、プロピレングリコール、ジプロピレングリコール、トリプロピレングリコール、ポリプロピレングリコール等のジ（メタ）アクリレート、トリス（２−ヒドロキシエチル）イソシアヌレートのジ（メタ）アクリレート、ネオペンチルグリコール１モルに４モル以上のエチレンオキサイドもしくはプロピレンオキサイドを付加して得たジオールのジ（メタ）アクリレート、ビスフェノールＡ１モルに２モルのエチレンオキサイドもしくはプロピレンオキサイドを付加して得たジオールのジ（メタ）アクリレート、トリメチロールプロパン１モルに３モル以上のエチレンオキサイドもしくはプロピレンオキサイドを付加して得たトリオールのジまたはトリ（メタ）アクリレート、ビスフェノールＡ１モルに４モル以上のエチレンオキサイドもしくはプロピレンオキサイドを付加して得たジオールのジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールトリ（メタ）アクリレート、ジペンタエリスリトールのポリ（メタ）アクリレート、エチレンオキサイド変性リン酸（メタ）アクリレート、エチレンオキサイド変性アルキル化リン酸（メタ）アクリレート等が挙げられる。
【００６５】
また、重合性モノマーと同時に併用できるものとしては、重合性オリゴマーとしてポリエステル（メタ）アクリレート、ポリエーテル（メタ）アクリレート、エポキシ（メタ）アクリレート、ウレタン（メタ）アクリレート等がある。
更に、本発明に使用する光重合開始剤は、用いる重合性オリゴマーおよび／または重合性モノマーに代表される紫外線硬化性化合物が硬化できる公知のものがいずれも使用できる。光重合開始剤としては、分子開裂型または水素引き抜き型のものが本発明に好適である。
【００６６】
このような例としては、ベンゾインイソブチルエーテル、２，４−ジエチルチオキサントン、２−イソプロピルチオキサントン、ベンジル、２，４，６−トリメチルベンゾイルジフェニルフォスフィンオキシド、２−ベンジル−２−ジメチルアミノ−１−（４−モルフォリノフェニル）−ブタン−１−オン、ビス（２，６−ジメトキシベンゾイル）−２，４，４−トリメチルペンチルフォスフィンオキシド等が好適に用いられ、さらにこれら以外の分子開裂型のものとして、１−ヒドロキシシクロヘキシルフェニルケトン、ベンゾインエチルエーテル、ベンジルジメチルケタール、２−ヒドロキシ−２−メチル−１−フェニルプロパン−１−オン、１−（４−イソプロピルフェニル）−２−ヒドロキシ−２−メチルプロパン−１−オンおよび２−メチル−１−（４−メチルチオフェニル）−２−モルフォリノプロパン−１−オン等を併用しても良いし、さらに水素引き抜き型光重合開始剤である、ベンゾフェノン、４−フェニルベンゾフェノン、イソフタルフェノン、４−ベンゾイル−４’−メチル−ジフェニルスルフィド等も併用できる。
【００６７】
また光重合開始剤に対する増感剤として例えば、トリメチルアミン、メチルジメタノールアミン、トリエタノールアミン、ｐ−ジエチルアミノアセトフェノン、ｐ−ジメチルアミノ安息香酸エチル、ｐ−ジメチルアミノ安息香酸イソアミル、Ｎ，Ｎ−ジメチルベンジルアミンおよび４，４’−ビス（ジエチルアミノ）ベンゾフェノン等の、前述重合性成分と付加反応を起こさないアミン類を併用することもできる。もちろん、上記光重合開始剤や増感剤は、紫外線硬化性化合物への溶解性に優れ、紫外線透過性を阻害しないものを選択して用いることが好ましい。
【００６８】
また、カチオン系紫外線硬化性接着剤としては公知のすべての組成物を用いることができ、カチオン重合型の光開始剤を含むエポキシ樹脂がこれに該当する。カチオン重合型の光開始剤としては、スルホニウム塩、ヨードニウム塩およびジアゾニウム塩等がある。
ヨードニウム塩の１例を示すと以下の通りである。ジフェニルヨードニウム ヘキサフルオロホスフェード、ジフェニルヨードニウム ヘキサフルオロアンチモネート、ジフェニルヨードニウム テトラフルオロボレート、ジフェニルヨードニウム テトラキス（ペンタフルオロフェニル）ボレート、ビス（ドデシルフェニル）ヨードニウム ヘキサフルオロホスフェート、ビス（ドデシルフェニル）ヨードニウム ヘキサフルオロアンチモネート、ビス（ドデシルフェニル）ヨードニウム テトラフルオロボレート、ビス（ドデシルフェニル）ヨードニウムテトラキス（ペンタフルオロフェニル）ボレート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム ヘキサフルオロホスフェート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム ヘキサフルオロアンチモネート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム テトラフルオロボレート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム テトラキス（ペンタフルオロフェニル）ボレート、などが挙げられる。
【００６９】
エポキシ樹脂は、ビスフェノールＡ−エピクロールヒドリン型、脂環式エポキシ、長鎖脂肪族型、臭素化エポキシ樹脂、グリシジルエステル型、グリシジルエーテル型、複素環式系等種々のものがいずれであってもかまわない。
エポキシ樹脂としては、反射層にダメージを与えないよう、遊離したフリーの塩素および塩素イオン含有率が少ないものを用いるのが好ましい。塩素の量が１重量％以下が好ましく、より好ましくは０．５重量％以下である。
【００７０】
カチオン型紫外線硬化性樹脂１００重量部当たりのカチオン重合型光開始剤の割合は通常、０．１〜２０重量部であり、好ましくは０．２〜５重量部である。なお、紫外線光源の波長域の近紫外領域や可視領域の波長をより有効に利用するため、公知の光増感剤を併用することができる。この際の光増感剤としては、例えばアントラセン、フェノチアジン、ベンジルメチルケタール、ベンゾフェノン、アセトフェノン等が挙げられる。
【００７１】
また、紫外線硬化性接着剤には、必要に応じてさらにその他の添加剤として、熱重合禁止剤、ヒンダードフェノール、ヒンダードアミン、ホスファイト等に代表される酸化防止剤、可塑剤およびエポキシシラン、メルカプトシラン、（メタ）アクリルシラン等に代表されるシランカップリング剤等を、各種特性を改良する目的で配合することもできる。これらは、紫外線硬化性化合物への溶解性に優れたもの、紫外線透過性を阻害しないものを選択して用いる。
（８）接着層７
接着層７は、透明である必要はないが、接着力が高く、硬化接着時の収縮率が小さいと媒体の形状安定性が高く好ましい。
【００７２】
また、接着層７は反射層６にダメージを与えない材料からなることが望ましい。但し、ダメージを抑えるために両層のあいだに公知の無機系または有機系の保護層を設けることもできる。
本発明において、接着層７の膜厚は、通常２μｍ以上が好ましい。所定の接着力を得るためにはある程度の膜厚が必要である。より好ましくは５μｍ以上である。但し媒体をできるだけ薄くするために、また硬化に時間を要し生産性が低下するなどの問題があるため、通常、１００μｍ以下が好ましい。
【００７３】
接着層７の材料は、中間樹脂層４の材料と同様のものが用いうるほか、感圧式両面テープ等も使用可能である。感圧式両面テープを反射層６と基板８のあいだに挟んで押圧することにより、接着層７を形成できる。
（９）その他の層について
上記積層構造において、必要に応じて任意の他の層を挟んでも良い。或いは媒体の最外面に任意の他の層を設けても良い。具体的には、半透明反射層３と中間樹脂層４のあいだ、中間樹脂層４と色素記録層５のあいだ、反射層６と接着層７のあいだ、などにバッファー層を設けてもよい。
【００７４】
バッファー層は２つの層の混和を防止し、相溶を防ぐものである。バッファー層が混和現象を防止する以外の他の機能を兼ねていても良い。また必要に応じてさらに他の中間層を挟んでも良い。
バッファー層の材料は、色素記録層５や中間樹脂層４と相溶せず、かつ、ある程度の光透過性をもつ必要があるが、公知の無機物及び有機物が用いうる。特性面からは、好ましくは無機物が用いられる。例えば、（１）金属又は半導体、（２）金属又は半導体の酸化物、窒化物、硫化物、酸硫化物、フッ化物又は炭化物、もしくは（３）非晶質カーボン、などが用いられる。中でも、ほぼ透明な誘電体からなる層や、ごく薄い金属層（合金を含む）が好ましい。
【００７５】
具体的には、酸化珪素、特に二酸化珪素や、酸化亜鉛、酸化セリウム、酸化イットリウム等の酸化物；硫化亜鉛、硫化イットリウムなどの硫化物；窒化珪素などの窒化物；炭化珪素；酸化物とイオウとの混合物；および後述の合金などが好適である。また、酸化珪素と硫化亜鉛との３０：７０〜９０：１０程度（重量比）の混合物も好適である。また、イオウと二酸化イットリウムの混合物を酸化亜鉛との混合物（Ｙ₂Ｏ₂Ｓ−ＺｎＯ）も好適である。
【００７６】
金属や合金としては、銀、又は銀を主成分とし更にチタン、亜鉛、銅、パラジウム、及び金よりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有するものが好適である。また、銀を主成分とし、少なくとも１種の希土類元素を０．１〜１５原子％含有するものも好適である。この希土類としては、ネオジウム、プラセオジウム、セリウム等が好適である。
【００７７】
その他、バッファー層作製時に記録層の色素を溶解しないようなものであれば樹脂層でも構わない。特に、真空蒸着やＣＶＤ法で作製可能な高分子膜が有用である。
バッファー層の厚さは２ｎｍ以上が好ましく、より好ましくは５ｎｍ以上である。バッファー層の厚さが過度に薄いと、上記の混和現象の防止が不十分となる虞がある。但し２０００ｎｍ以下が好ましく、より好ましくは５００ｎｍ以下である。バッファー層が過度に厚いと、混和防止には不必要であるばかりでなく、光の透過率を低下させる恐れもある。また無機物からなる層の場合には成膜に時間を要し生産性が低下したり、膜応力が高くなったりする虞があり２００ｎｍ以下が好ましい。特に、金属の場合は光の透過率を過度に低下させるため、２０ｎｍ以下程度が好ましい。
【００７８】
また、記録層や反射層を保護するために保護層を設けても良い。保護層の材料としては、記録層や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、紫外線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、酸化ケイ素、窒化ケイ素、ＭｇＦ₂、ＳｎＯ₂等が挙げられる。
【００７９】
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調製し、これを塗布、乾燥することによって形成することができる。紫外線硬化性樹脂は、そのままもしくは適当な溶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。紫外線硬化性樹脂としては、例えば、ウレタンアクリレート、エポキシアクリレート、ポリエステルアクリレートなどのアクリレート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。
【００８０】
保護層の形成方法としては、記録層と同様にスピンコート法やキャスト法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、３〜５０μｍが好ましい。
【００８１】
更に、上記光記録媒体には、必要に応じて、記録・再生光の入射面ではない面に、インクジェット、感熱転写等の各種プリンタ、或いは各種筆記具にて記入（印刷）が可能な印刷受容層を設けてもよい。
或いは、本層構成の光記録媒体を２枚、第１基板を外側にして貼合せて、記録層を４層有する、より大容量媒体とすることもできる。
［２］光記録媒体の製造法について
次に、本発明に係る光記録媒体の製造法の好ましい一例について図１及び図２を用いて説明する。図２は本製造法を説明するための模式図である。
【００８２】
まず、表面に凹凸で溝及びランド、プリピットが形成された透明な第１基板１を、スタンパをもとに射出成形または２Ｐ法等により作成する。次に、少なくとも有機色素を溶媒に溶解させた後、透明基板１の凹凸を有する側の表面にスピンコート等により成膜し色素記録層２を形成する。更にその上に、Ａｇ合金などをスパッタまたは蒸着することにより半透明反射層３を成膜する。
【００８３】
この上に、中間樹脂層４を形成するにあたり、型を用いて表面に凹凸を形成する。型としては、生産性、コストなどの観点から、樹脂からなるスタンパを用いるのが好ましい。
樹脂スタンパ１５は中間樹脂層となるべき樹脂に対して十分な剥離性を有していれば良い。透明である必要はないが、成形性が良く、形状安定性が良いことが望ましい。生産性及びコストの観点から、望ましくは、樹脂スタンパ１５は複数回の転写に使用可能であるのが望ましい。また、使用後のリサイクルが可能であることが望ましい。
【００８４】
樹脂スタンパ１５は樹脂基板１６上に１層以上のセパレート層１７を有しても良いし、樹脂基板１６のみからなってもよいが、後者のほうが生産性やコストの観点から好ましい。
まず、上述のスタンパとは凹凸が逆（ネガ）の金属製スタンパを用い、射出成形や２Ｐ法等により樹脂基板１６を作製する。樹脂基板１６は透明である必要はないが、成形性が良く、形状安定性が良いことが望ましい。
【００８５】
このような材料としては、例えばアクリル系樹脂、メタクリル系樹脂、ポリカーボネート樹脂、ポリオレフィン系樹脂（特に非晶質ポリオレフィン）、ポリエステル系樹脂、ポリスチレン樹脂、エポキシ樹脂等の樹脂からなるものが挙げられる。
樹脂スタンパ１５が樹脂基板１６上に１層以上のセパレート層１７を有する構成であれば、樹脂基板はセパレート層との密着性が高い樹脂である必要があり、その他成形性などの高生産性、コスト、低吸湿性、形状安定性などの点からポリカーボネートが好ましい。
【００８６】
樹脂スタンパ１５が樹脂基板１６のみからなる構成であれば、樹脂基板は中間樹脂層４を構成する樹脂との密着性が低く剥離性が高いことが望ましい。その他他成形性などの高生産性、コスト、低吸湿性、形状安定性などの点から非晶質ポリオレフィンが好ましい。
樹脂基板１６の厚さは、形状安定性及びハンドリングの容易さの点で、０．５ｍｍ以上とするのが望ましい。厚さの上限は特にないが、通常、３ｍｍ以下で十分である。
【００８７】
セパレート層１７は中間樹脂層４を構成する樹脂との密着性が低く剥離性が高いことが望ましい。また、成膜されたときに樹脂基板の凹凸を忠実に反映した凹凸が形成されることが望ましい。
セパレート層１７の材料としては、中間樹脂層４の樹脂との剥離性の点から金属または合金が好ましく、通常、Ａｇ、Ａｕ、Ｃｕ、Ｐｔ及びＰｄから選ばれる金属またはそれらの合金が用いられる。セパレート層１７の厚さは、中間樹脂層４からの剥離性を確保するためにはある程度の膜厚が必要で、２ｎｍ以上とするのが好ましい。一方、基板の凹凸を忠実に反映するためには厚すぎないことが望ましく、通常、２００ｎｍ以下が好ましい。
【００８８】
基板１上に形成された半透明反射層３上に紫外線硬化性樹脂等をスピンコート等により成膜したのち、樹脂スタンパ１５を載置し、紫外線硬化性樹脂に凹凸を転写する。このとき、中間樹脂層４の膜厚が所定範囲になるように調節しつつ行う。この状態で半透明反射層３側から紫外線を照射するなどして樹脂を硬化させ、十分硬化したところで樹脂スタンパ１５を剥離して、表面に凹凸が形成された凹凸が形成された中間樹脂層４を形成する。或いは紫外線を媒体の側面から照射することもできる。いずれにせよ、この紫外線により色素記録層がダメージを受けないように注意が必要である。
【００８９】
続いて図１に示すように、中間樹脂層４の凹凸を有する側の表面に、少なくとも有機色素を溶媒に溶解させた後、スピンコート等により成膜し色素記録層５を形成する。更に、Ａｇ合金などをスパッタ、蒸着することにより反射層６を成膜する。
また、ポリカーボネートを射出成形して鏡面基板８を得る。基板１の積層構造上に、接着層７を介して鏡面基板８を貼合せ、光記録媒体を製造することができる。接着層７は不透明であったり、多少表面が粗くてもよく、遅延硬化型の接着剤を問題なく使用できる。反射層６上に接着剤をスクリーン印刷等で塗布し紫外線を照射してから鏡面基板８を載置し押圧して接着層７を形成できる。或いはまた、感圧式両面テープを用い、積層構造Ａ、Ｂ間に該テープを挟んで押圧することにより、接着層を形成することもできる。
［３］光記録媒体の記録再生方法について
次に、本発明に係る光記録媒体の記録再生方法の好ましい一例について説明する。
【００９０】
上記のようにして得られた本発明の光記録媒体への記録は、記録層に直径０．５〜１μｍ程度に集束したレーザ光を第１基板側から照射することにより行う。レーザ光の照射された部分には、レーザ光エネルギーの吸収による、分解、発熱、溶解等の記録層の熱的変形が起こり、光学特性が変化する。
記録された情報の再生は、レーザ光により、光学特性の変化が起きている部分と起きていない部分の反射率の差を読みとることにより行う。
【００９１】
２層の記録層には以下のようにして個別に記録再生する。集束したレーザの集束位置をナイフエッジ法、非点収差法、フーコー法等で得られるフォーカスエラー信号によって、第１記録層２と第２記録層５とは区別できる。すなわち、レーザ光を集束する対物レンズを上下に動かすと、レーザの集束位置が第１記録層に対応する位置と第２記録層に対応する位置で、それぞれＳ字カーブが得られる。どちらのＳ字カーブをフォーカスサーボに用いるかにより、第１記録層と第２記録層のどちらを記録再生するかを選択可能である。
【００９２】
本発明において好ましくは、第１基板及び中間樹脂層にそれぞれ凹凸が形成されてなり、第１基板の凸部及び中間樹脂層の凸部を記録トラックとして記録再生を行うものとする。
通常、色素記録層は塗布形成されるので溝部で厚膜となり記録再生に適する。本発明においては第１基板１の溝部、即ち光の入射方向に対して凸部を記録トラック１１とし、中間樹脂層の溝部、即ち光の入射方向に対して凸部を記録トラック１２とするのが好ましい。
【００９３】
本発明の光記録媒体について使用されるレーザ光は、Ｎ₂、Ｈｅ−Ｃｄ、Ａｒ、Ｈｅ−Ｎｅ、ルビー、半導体、色素レーザなどが挙げられるが、軽量であること、コンパクトであること、取り扱いの容易さ等から半導体レーザが好適である。
使用されるレーザ光は、高密度記録のため波長は短いほど好ましいが、特に３５０〜５３０ｎｍのレーザ光が好ましい。かかるレーザ光の代表例としては、中心波長４０５ｎｍ、４１０ｎｍ、５１５ｎｍのレーザ光が挙げられる。
【００９４】
波長３５０〜５３０ｎｍの範囲のレーザ光の一例は、４０５ｎｍ、４１０ｎｍの青色または５１５ｎｍの青緑色の高出力半導体レーザを使用することにより得ることができるが、その他、例えば、（ａ）基本発振波長が７４０〜９６０ｎｍの連続発振可能な半導体レーザ、または（ｂ）半導体レーザによって励起され、且つ基本発振波長が７４０〜９６０ｎｍの連続発振可能な固体レーザのいずれかを第二高調波発生素子（ＳＨＧ）により波
長変換することによっても得ることができる。
【００９５】
上記のＳＨＧとしては、反転対称性を欠くピエゾ素子であればいかなるものでもよいが、ＫＤＰ、ＡＤＰ、ＢＮＮ、ＫＮ、ＬＢＯ、化合物半導体などが好ましい。第二高調波の具体例としては、基本発振波長が８６０ｎｍの半導体レーザの場合、その倍波の４３０ｎｍ、また半導体レーザ励起の固体レーザの場合は、ＣｒドープしたＬｉＳｒＡｌＦ₆結晶（基本発振波長８６０ｎｍ）からの倍波の４３０ｎｍなどが挙げられる。
【００９６】
【実施例】
以下に実施例及び比較例を挙げて本発明を具体的に説明するが、本発明はその要旨を越えない限り、以下の実施例に限定されるものではない。
（実施例１）
まず、溝及びプリピットを形成したＮｉスタンパを用いて、ポリカーボネートを射出成形することにより、溝ピッチ０．７４μｍ、溝幅０．３μｍ、溝深さ１５０〜１８０ｎｍの溝及びプリピットが形成された直径１２０ｍｍ、厚さ０．６ｍｍの基板１を得た。
【００９７】
次に、前記一般式（ＩＩ）で表される含金属アゾ色素をオクタフルオロペンタノールに溶解し、２重量％に調整した。これを基板１上に滴下し、スピナー法により塗布し、塗布後、１００℃で３０分間乾燥し記録層２を形成した。この塗布膜の最大吸収波長（λｍａｘ）は約６００ｎｍであった。次に、Ａｇ−Ｃｕ（０．９原子％）−Ａｕ（１．０原子％）−Ｎｄ（０．７原子％）なるＡｇ合金を１６ｎｍの厚さにスパッタリングし半透明反射層３を成膜した。この上に紫外線硬化性樹脂からなる保護層を５〜１０μｍの厚さに設けた。
【００９８】
次に樹脂スタンパ１５を作製した。すなわち上で用いたＮｉスタンパとはほぼ逆の凹凸を有するＮｉスタンパを用いて、ポリカーボネートを射出成形することにより、ランドピッチ０．７４μｍ、ランド幅０．３μｍ、ランド高さ１５０〜１８０ｎｍのランド及びプリピット（凸状）が形成された直径１２０ｍｍ、厚さ０．６ｍｍのスタンパ基板１６を得た。ここにＡｇを６０ｎｍの厚さにスパッタリングしセパレート層１７を成膜し、樹脂スタンパ１５を得た。
【００９９】
このように作製した基板１の積層構造上に、紫外線硬化性樹脂（三菱レーヨン社製）を塗布し、樹脂スタンパ１５を凹凸面を基板１側に向けて載置した。その後基板１側から半透明反射層３を介して紫外線を照射し、硬化させて樹脂スタンパ１５を剥離することで、凹凸が転写された厚さ約５５μｍ（ランド部同士での測定値）の中間樹脂層４を形成した。
【０１００】
続いて、同じ色素溶液を同様に塗布、乾燥して記録層５を形成し、同じＡｇ合金を、１３０ｎｍの厚さにスパッタリングし反射層６を成膜した。この上に紫外線硬化性樹脂からなる保護層を５〜１０μｍの厚さに設けた。
また、ポリカーボネートを射出成形することにより、直径１２０ｍｍ、厚さ０．６ｍｍの鏡面基板８を得た。
【０１０１】
このように作製した積層構造上に、カチオン重合型紫外線硬化性樹脂（遅延硬化型、ソニーケミカル社製、ＳＫ７０００）からなる接着剤をスクリーン印刷にて塗布した後、紫外線を照射し、鏡面基板８を載置し硬化接着させることで厚さ約５５μｍの接着層７とし、光記録媒体を製造した。
この光記録媒体に対し、波長６５０ｎｍ、開口数０．６５の記録再生評価機で記録再生を行った。記録再生光は基板１側から入射し、第１基板の凸部及び第２基板の凹部を記録トラックとして評価を行ったところ、色素記録層２及び色素記録層５の両方について記録再生が可能であった。
【０１０２】
【発明の効果】
本発明によれば、記録層を少なくとも２層設け、それぞれ異なる情報を記録できるので、従来の光記録媒体に比べて記録容量を飛躍的に大容量化することができる利点がある。
また、この層構成とすることで、第１基板側から光ビームを入射すれば、第１記録層、第２記録層ともに記録・再生を良好に行うことができるという利点がある。これにより、ユーザが媒体を反転させるなどの作業が不要なので利便性が高まる。ドライブが記録再生用光ヘッドを２個以上有する必要もなくドライブを簡素な構成で安価なものにできる。
【０１０３】
また、色素記録層が第１基板、中間樹脂層に近接することにより、記録に伴う樹脂層の変形が起こりやすく、変調度が大きくジッタ特性に優れた記録が行えるという利点がある。
更に、本媒体は第１記録層、第２記録層ともに同じ凸部を記録トラックとして記録再生が行えるので、トラッキングの極性等を層によって変える必要もなく、比較的簡単に、良好な記録再生が行えるという利点もある。
【０１０４】
更に、この層構成とすることで、第２基板は透明である必要がないので材料選択の幅が広がる利点もある。例えば、第１基板と第２基板の機能を分け、第２基板を形状安定性に優れた材料で構成して光記録媒体に十分な剛性を付与し、これにより第１基板を薄くすることもできる。対物レンズを記録層により近づけることができるため、レンズの開口数を上げて記録密度を大きくでき、さらに大容量化できるので好ましい。
【０１０５】
或いは、本層構成の光記録媒体を２枚、第１基板を外側にして貼合せて、記録層を４層有する、より大容量媒体とすることもできる。
【図面の簡単な説明】
【図１】 本発明に係る光記録媒体の一例を示す模式図である。
【図２】 本発明に係る光記録媒体の製造法の一例を説明するための模式図である。
【図３】 従来の光記録媒体の一例を示す模式図である。
【符号の説明】
１ 透明基板
２ 色素記録層
３ 半透明反射層
４ 中間樹脂層
５ 色素記録層
６ 反射層
７ 接着層
８ 基板
１１ 凸部からなる記録トラック
１２ 凸部からなる記録トラック
１５ 樹脂スタンパ
１６ スタンパ基板
１７ セパレート層
２１ 透明基板
２２ 色素記録層
２３ 反射層
２４ 接着層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording medium, and more particularly to a large-capacity optical recording medium having two recording layers capable of recording a large amount of data.
[0002]
[Prior art]
Currently, various optical recording media such as CD-R, CD-RW, and MO can store a large amount of information and are easily recognized as an external storage device in an information processing apparatus such as a computer because they can be easily accessed at random. It is becoming popular. Furthermore, it is desired to increase the recording density by increasing the amount of information handled.
[0003]
Among various optical recording media, an optical disc having a recording layer containing an organic dye (hereinafter sometimes referred to as a dye recording layer) such as CD-R and DVD-R is relatively inexpensive and is a reproduction-only optical disc. And is widely used in particular.
As an example, a medium such as a CD-R, which is a typical optical disk having a recording layer containing an organic dye, has a dye recording layer and a reflective layer in this order on a transparent disk substrate, and covers these recording layer and reflective layer. It has a laminated structure having a protective layer, and performs recording / reproduction with a laser beam through a substrate.
[0004]
Similarly, a typical single-sided DVD-R has a dye recording layer, a reflective layer, and a protective layer covering these layers on the first transparent disk substrate in this order, and further on the protective layer via an adhesive layer or A laminated structure in which a so-called dummy disk having a reflective layer provided on a second transparent disk substrate is provided, and recording / reproduction is performed with laser light through the first transparent disk substrate. The dummy disk may be only a transparent disk substrate, or may be provided with a layer other than the reflective layer.
[0005]
[Problems to be solved by the invention]
One means for further increasing the recording capacity of these optical recording media is to provide a plurality of recording layers, for example, two layers, on one medium. However, when two recording layers are provided, usually only one layer can be recorded / reproduced from one side, which is not convenient.
[0006]
FIG. 3 is a schematic cross-sectional view showing a layer structure of a double-sided DVD-R which is a typical example of an optical recording medium provided with two conventional recording layers. This optical recording medium is formed by laminating two laminated disks each having a transparent substrate 21, a recording layer 22 and a reflective layer 23 sequentially formed thereon, with the reflective layer 23 inside, and an adhesive layer 24 interposed therebetween. Thus, recording / reproduction is performed with a laser beam through the substrate. Here, a protective layer may be provided on the reflective layer 23.
[0007]
However, since the laser beam used for recording / reproduction is blocked by the reflective layer 23, recording / reproduction cannot be performed on both recording layers 22 from one side.
For this reason, conventionally, in order to perform recording / reproduction on both recording layers 22, it is necessary to provide two optical heads corresponding to both sides on the drive (recording / reproducing apparatus) side, and the drive is complicated and expensive. There was a problem of becoming. Alternatively, when the drive side has only one optical head corresponding to one side, there is a problem that it is not convenient because the user needs to replace the front and back of the optical recording medium appropriately. For this reason, there was a request to record / reproduce both layers from one side.
[0008]
By the way, in a DVD-ROM which is a read-only optical disk, a laminated structure is known in which information of two layers can be reproduced from one side by using a translucent reflective layer. A laser having a laminated structure in which a translucent reflective layer, an adhesive layer, a reflective layer, and a second substrate having information due to unevenness are provided in this order on a transparent first substrate having information due to unevenness, and a laser passing through the first substrate Information by the unevenness formed on each of the first substrate and the second substrate can be reproduced by light.
[0009]
However, an optical recording medium such as a DVD-R having a dye recording layer has a complicated layer structure as compared with a DVD-ROM and needs to satisfy various recording / reproduction characteristics. There wasn't.
In view of this, an object of the present invention is to provide a large-capacity optical recording medium having a plurality of dye recording layers that can be recorded / reproduced from one side.
[0010]
[Means for Solving the Problems]
  That is, the present inventionFirstThe gist includes a first recording layer containing a dye, a translucent reflective layer, an intermediate resin layer, a second recording layer containing a dye, a reflective layer, an adhesive layer, and a second substrate in this order on a transparent first substrate. TenaThe intermediate resin layer and the second recording layer are in contact with each other, the first substrate and the intermediate resin layer are formed with irregularities, the intermediate resin layer is made of a curable resin, and the intermediate resin layer The unevenness exists in an optical recording medium formed by transferring and curing a resin stamper made of amorphous polyolefin having unevenness to the curable resin. The second gist of the present invention includes a first recording layer containing a dye, a translucent reflective layer, an intermediate resin layer, a second recording layer containing a dye, a reflective layer, an adhesive layer, on a transparent first substrate. An optical recording comprising a second substrate in this order, wherein the intermediate resin layer and the second recording layer are in contact with each other, and irregularities are formed on the first substrate and the intermediate resin layer, respectively. A method for manufacturing a medium, wherein the intermediate resin layer is made of a curable resin, and the unevenness of the intermediate resin layer is transferred and cured from a resin stamper made of amorphous polyolefin having unevenness to the curable resin. An optical recording medium manufacturing method is characterized in that the optical recording medium is formed.
[0011]
According to the present invention, since at least two recording layers are provided and different information can be recorded, there is an advantage that the recording capacity can be dramatically increased as compared with the conventional optical recording medium.
In addition, this layer configuration has an advantage that if the light beam is incident from the first substrate side, both the first recording layer and the second recording layer can be recorded and reproduced satisfactorily. Thereby, since the user does not need to perform work such as inverting the medium, convenience is enhanced. The drive does not need to have two or more optical heads for recording and reproduction, and the drive can be made inexpensive with a simple configuration.
[0012]
Further, since the dye recording layer is close to the first substrate and the intermediate resin layer, there is an advantage that the resin layer is easily deformed due to recording, and the recording has a large modulation degree and excellent jitter characteristics.
Furthermore, since this medium can perform recording and reproduction with the same convex portion as the recording track in both the first recording layer and the second recording layer, there is no need to change the polarity of tracking depending on the layer, and good recording and reproduction can be performed relatively easily. There is also an advantage that it can be done.
[0013]
And by setting it as this layer structure, since the 2nd board | substrate does not need to be transparent, there also exists an advantage which the breadth of material selection spreads. For example, the functions of the first substrate and the second substrate may be divided, and the second substrate may be made of a material having excellent shape stability to give the optical recording medium sufficient rigidity, thereby thinning the first substrate. it can. Since the objective lens can be brought closer to the recording layer, it is preferable because the recording density can be increased by increasing the numerical aperture of the lens and the capacity can be further increased.
[0014]
Alternatively, two optical recording media having this layer structure and two first recording substrates may be bonded to form a larger capacity medium having four recording layers.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail. FIG. 1 is a schematic sectional view showing an example of an optical recording medium according to the present invention. On a disk-shaped transparent first substrate 1, a first recording layer containing a dye (hereinafter sometimes referred to as a dye recording layer) 2, a translucent reflective layer 3, an intermediate resin layer 4, a dye recording layer 5, The reflective layer 6, the adhesive layer 7, and the substrate 8 are provided in this order. The light beam is irradiated from the first substrate 1 side, and recording / reproduction is performed. In the present invention, “transparent” means transparent to a light beam used for recording / reproduction of an optical recording medium.
[0016]
Concavities and convexities are formed on the transparent first substrate 1 and the intermediate resin layer 4, respectively, and constitute recording tracks. The recording track 11 on the transparent first substrate 1 is formed of a convex portion with respect to the light incident direction. The recording track 12 on the intermediate resin layer 4 is also formed with a convex portion with respect to the light incident direction. In addition, it may have uneven pits as necessary. Unless otherwise specified, in the present invention, the unevenness is defined with respect to the incident direction of light used for recording / reproducing.
[0017]
Next, each layer will be described.
[1] Configuration of optical recording medium
(1) About the first substrate 1
The transparent first substrate 1 is desirably transparent and has excellent optical properties such as a low birefringence. Moreover, it is desirable to be excellent in moldability such as easy injection molding. It is desirable that the hygroscopicity is small.
[0018]
Furthermore, it is desirable to provide shape stability so that the optical recording medium has a certain degree of rigidity. However, if the second substrate 8 has sufficient shape stability as described above, the shape stability of the first substrate 1 may not be large.
Examples of such materials include those made of resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like. Can be used. Or what provided the resin layer which consists of radiation curable resin, such as photocurable resin, on base | substrates, such as glass, can also be used.
[0019]
Polycarbonate is preferable from the viewpoints of high productivity such as optical characteristics and moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoint of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.
The smaller the distance between the objective lens and the recording layer, the easier it is to increase the recording density. Therefore, the first substrate 1 is preferably thin, and the thickness is usually preferably 2 mm or less, more preferably 1 mm or less. However, in order to obtain sufficient optical properties, hygroscopicity, moldability, and shape stability, a certain amount of thickness is required, and is usually preferably 10 μm or more, and more preferably 30 μm or more.
[0020]
In the present invention, it is desirable to appropriately adjust the distance between the objective lens and both recording layers in order to perform good recording / reproduction on both the first recording layer and the second recording layer. The focal point of the objective lens is set to approximately the midpoint between both recording layers.
Specifically, in the single-sided DVD-R system, the distance between the objective lens and the recording layer is adjusted to be optimal when the substrate thickness is 0.6 mm.
[0021]
Therefore, in the case of single-layer DVD-R compatibility in this layer structure, the thickness of the first substrate 1 may be a thickness obtained by subtracting one half of the thickness of the intermediate resin layer 4 from 0.6 mm. Most preferred. At this time, the substantially middle point between both recording layers is about 0.6 mm, and it is easy to apply focus servo to both recording layers. When there are other layers such as a buffer layer and a protective layer between the second recording layer and the translucent reflective layer 3, from 0.6 mm to one half of the sum of the film thicknesses of those layers and the intermediate resin layer 4 Most preferably, the thickness is reduced.
[0022]
The first substrate 1 is provided with irregularities in a spiral shape or a concentric shape to form grooves and lands. Normally, information is recorded / reproduced in / from the dye recording layer 2 using such grooves and / or lands as recording tracks. Usually, in the case of a DVD-R disc that records and reproduces by condensing a laser having a wavelength of 650 nm with an objective lens having a numerical aperture of 0.6 to 0.65, the dye recording layer 2 is coated and formed, so that the groove is thick. Suitable for recording and playback. In the present invention, it is preferable that the groove portion of the first substrate 1, that is, the convex portion with respect to the light incident direction is the recording track 11. Here, a recessed part and a convex part say the recessed part and convex part with respect to the incident direction of light, respectively. Usually, the groove width is about 200 to 500 nm, and the groove depth is about 120 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, it may have uneven pits such as land prepits as necessary.
[0023]
From the viewpoint of cost, the substrate having such irregularities is preferably manufactured by injection molding from a stamper having irregularities. When a resin layer made of a radiation curable resin such as a photocurable resin is provided on a substrate such as glass, irregularities such as recording tracks may be formed on the resin layer.
(2) About the second substrate 8
The second substrate 8 preferably has shape stability so that the optical recording medium has a certain degree of rigidity. That is, it is preferable that mechanical stability is high and rigidity is large. Moreover, it is desirable that the adhesiveness with the adhesive layer 7 is high.
[0024]
As described above, when the first substrate 1 does not have sufficient shape stability, the second substrate 8 needs to have particularly high shape stability. In this respect, it is desirable that the hygroscopicity is small. However, the second substrate 8 does not need to be transparent. The second substrate 8 may be a mirror substrate, and it is not necessary to form irregularities, so that the transferability by injection molding is not necessarily good.
[0025]
As such a material, the same material as that which can be used for the first substrate 1 can be used. For example, an Al alloy substrate such as an Al—Mg alloy containing Al as a main component, or an Mg alloy as a main component, for example. An Mg alloy substrate such as an Mg—Zn alloy, a substrate made of any of silicon, titanium, and ceramics, a substrate that combines them, and the like can be used.
[0026]
Polycarbonate is preferable from the viewpoints of productivity, cost, low hygroscopicity, shape stability, and the like. Amorphous polyolefin is preferred from the standpoint of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.
In order to give the optical recording medium sufficient rigidity, the second substrate 8 is preferably thick to some extent, and the thickness is preferably 0.3 mm or more. However, the thinner one is advantageous for thinning the recording / reproducing apparatus, and it is preferably 3 mm or less. More preferably, it is 1.5 mm or less.
[0027]
The second substrate 8 may be a mirror substrate having no irregularities, but is preferably manufactured by injection molding from the viewpoint of ease of production.
As an example of a preferable combination of the first substrate and the second substrate, the first substrate and the second substrate are made of the same material and have the same thickness. Since the rigidity is equal and balanced, it is preferable that the medium is difficult to be deformed against environmental changes. In this case, it is preferable that the degree and direction of deformation when the environment changes are the same for both substrates.
[0028]
Another example of a preferable combination is that the first substrate is as thin as about 0.1 mm and the second substrate is as thick as about 1.1 mm. The objective lens is preferable because it easily approaches the recording layer and easily increases the recording density. At this time, the first substrate may be in the form of a sheet.
(3) About the first dye recording layer 2
The first dye recording layer 2 needs to have higher sensitivity than the recording layer used for an optical recording medium usually used for CD-R, single-sided DVD-R, and the like. In the present invention, the power of the incident light beam is divided into two due to the presence of the translucent reflective layer and the like, and is divided into the recording of the first dye recording layer and the recording of the second dye recording layer. In order to record, it is necessary to have particularly high sensitivity.
[0029]
In order to realize good recording / reproducing characteristics, it is desirable that the dye has a low heat generation and a high refractive index.
Further, in the combination of the first dye recording layer 2 and the translucent reflective layer 3, it is desirable that the reflection, transmission and absorption of light be in an appropriate range. The recording sensitivity can be increased and the thermal interference during recording can be reduced.
[0030]
Examples of such organic dye materials include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, stearyllium dyes, etc.), anthraquinone dyes, Examples include azulenium dyes, metal-containing azo dyes, and metal-containing indoaniline dyes. Among these, metal-containing azo dyes are preferable because they are excellent in durability and light resistance.
[0031]
Among the above-mentioned various organic dyes, metal-containing azo dyes are preferable because they are excellent in recording sensitivity and light resistance. In particular, the following general formula (I) or (II)
[0032]
[Chemical 1]

[0033]
(Ring A¹And A²Are nitrogen-containing aromatic heterocycles each independently having a substituent, and ring B¹And B²Are each independently an aromatic ring optionally having a substituent. X is a C1-C6 alkyl group substituted with at least two fluorine atoms. ) Is preferred. In addition, as expected from the structural formula, this dye is decomposed by decomposition of the dye during recording.₂Corrosive gas such as is generated. However, since the reflective layer of the optical recording medium of the present invention has a very high corrosion resistance, it is not corroded by this corrosive gas and has excellent storage stability over a long period of time.
[0034]
The organic dye used in the recording layer of the present invention is preferably a dye compound having a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 to 900 nm and suitable for recording with a blue to near infrared laser. Usually, a near infrared laser having a wavelength of about 770 to 830 nm used for a CD-R, a red laser having a wavelength of about 620 to 690 nm used for a DVD-R, or a so-called blue laser having a wavelength of 410 nm or 515 nm, etc. A dye suitable for recording is more preferable.
[0035]
One kind of dye may be used, or two or more kinds of the same kind or different kinds may be used in combination. Furthermore, it is also possible to use an optical recording medium corresponding to recording with laser light in a plurality of wavelength regions by using a combination of dyes suitable for recording in each of the recording light with the plurality of wavelengths.
The recording layer is also a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone, etc.) as a singlet oxygen quencher to improve the stability and light resistance of the recording layer. In order to improve the recording sensitivity, a recording sensitivity improving agent such as a metal compound may be contained. Here, the metal compound refers to a compound in which a metal such as a transition metal is contained in the compound in the form of atoms, ions, clusters, etc., for example, an ethylenediamine complex, an azomethine complex, a phenylhydroxyamine complex, a phenanthroline complex, Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex and porphyrin complex can be mentioned. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.
[0036]
Furthermore, a binder, a leveling agent, an antifoaming agent, etc. can be used together in the recording layer of the present invention, if necessary. 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.
[0037]
The film thickness of the recording layer varies depending on the recording method and the like, and is not particularly limited. However, in order to obtain a sufficient degree of modulation, it is usually preferably 5 nm or more, more preferably 10 nm or more, Especially preferably, it is 20 nm or more. However, in the present invention, since it is not necessary to be too thick in order to transmit light moderately, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less. The film thickness of the recording layer is usually different between the groove part and the land part. In the present invention, the film thickness of the recording layer refers to the film thickness in the groove part of the substrate.
[0038]
Examples of the method for forming the recording layer include vacuum film forming methods, sputtering methods, doctor blade methods, cast methods, spin coating methods, dipping methods, and the like, but from the viewpoint of mass productivity and cost, A spin coating method is preferred. From the viewpoint that a recording layer having a uniform thickness can be obtained, the vacuum vapor deposition method is preferable to the coating method.
[0039]
In the case of film formation by spin coating, the rotation speed is preferably 10 to 15000 rpm, and after spin coating, treatment such as heating or application to solvent vapor may be performed.
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. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; perfluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Examples of the solvent include hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.
[0040]
In the case of the vacuum vapor deposition method, for example, an organic dye and recording layer components such as various additives as necessary are put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is filled with an appropriate vacuum pump.^-2-10^-FiveAfter evacuating to about Pa, the crucible is heated to evaporate the recording layer components and vapor deposited on the substrate placed facing the crucible to form the recording layer.
(4) Second dye recording layer 5
The second dye recording layer 5 needs to be more sensitive than the recording layer used in an optical recording medium usually used for CD-R, single-sided DVD-R, and the like. In the present invention, the power of the incident light beam is divided into two due to the presence of the translucent reflective layer and the like, and is divided into the recording of the first dye recording layer and the recording of the second dye recording layer. In order to record, it is necessary to have particularly high sensitivity.
[0041]
In order to realize good recording / reproducing characteristics, it is desirable that the dye has a low heat generation and a high refractive index.
Further, in the combination of the second dye recording layer 5 and the reflective layer 6, it is desirable that the reflection and absorption of light be in an appropriate range. The recording sensitivity can be increased and the thermal interference during recording can be reduced.
[0042]
Since the material of the second dye recording layer 5, the film forming method, and the like are described in substantially the same manner as in the first dye recording layer 2, only different points will be described.
The film thickness of the recording layer varies depending on the recording method and the like, and is not particularly limited. However, in order to obtain a sufficient degree of modulation, it is usually preferably 10 nm or more, more preferably 30 nm or more, Especially preferably, it is 50 nm or more. However, since it is not necessary to be too thick in order to obtain an appropriate reflectance, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less.
[0043]
The materials used for the first dye recording layer 2 and the second dye recording layer 5 may be the same or different.
(5) Translucent reflective layer 3
The translucent reflective layer 3 needs to have low light absorption, light transmittance of 40% or more, and appropriate light reflectance. For example, an appropriate transmittance can be provided by providing a thin metal with high reflectivity. Moreover, it is desirable that there is some degree of corrosion resistance. Further, it is desirable that the first dye recording layer 2 has a blocking property so as not to be affected by the seepage of the intermediate resin layer 4.
[0044]
In order to ensure high transmittance, the thickness of the translucent reflective layer 3 is usually preferably 50 nm or less. More preferably, it is 30 nm or less. More preferably, it is 20 nm or less. However, since the first dye recording layer 2 is not affected by the intermediate resin layer 4, a certain thickness is required and is usually 3 nm or more. More preferably, it is 5 nm or more.
[0045]
As the material of the translucent reflective layer 3, a material having a moderately high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf , V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and rare earth metals and semi-metals It is possible to use a metal alone or as an alloy. Among these, Au, Al, and Ag have high reflectivity and are suitable as materials for the translucent reflective layer 3. In addition to these as main components, other components may be included.
[0046]
Among these, those containing Ag as a main component are particularly preferable from the viewpoint of low cost and high reflectance. Here, the main component means one having a content of 50% or more.
The translucent reflective layer 3 is thin, and if the crystal grains of the film are large, it causes reproduction noise. Therefore, it is preferable to use a material with small crystal grains. Since pure silver tends to have large crystal grains, Ag is preferably used as an alloy.
[0047]
Among these, it is preferable to contain 0.1 to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au, and rare earth metals. When two or more of Ti, Zn, Cu, Pd, Au, and rare earth metal are included, each may be 0.1 to 15 atomic%, but the total of these is preferably 0.1 to 15 atomic%. .
[0048]
A particularly preferable alloy composition contains 0.1 to 15 atomic% of at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au, containing Ag as a main component, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Among the rare earth metals, neodymium is particularly preferable. Specifically, AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, and the like.
[0049]
As the translucent reflective layer 3, a layer made only of Au is suitable because it has small crystal grains and is excellent in corrosion resistance. However, it is more expensive than Ag alloy.
It is also possible to use a layer made of Si as the translucent reflective layer 3.
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.
[0050]
Examples of the method for forming the translucent reflective layer 3 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or below the reflective layer in order to improve reflectivity, improve recording characteristics, and improve adhesion.
(6) Reflective layer 6
The reflective layer 6 needs to have a high reflectance. Moreover, it is desirable that it is highly durable.
[0051]
In order to ensure high reflectivity, the thickness of the reflective layer 6 is usually preferably 20 nm or more. More preferably, it is 30 nm or more. More preferably, it is 50 nm or more. However, in order to increase the recording sensitivity, it is preferable to be thin to some extent, and it is usually set to 400 nm or less. More preferably, it is set to 300 nm or less.
As the material of the reflective layer 6, 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, and Pd are used alone or as an alloy. It is possible. 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 components may be included as other components. Examples of other components include Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, Te, Pb Mention may be made of metals and metalloids such as Po, Sn, Bi and rare earth metals.
[0052]
Among these, those containing Ag as a main component are particularly preferable because of low cost, high reflectivity, and when a print receiving layer described later is provided, a white and beautiful ground color can be obtained. Here, the main component means one having a content of 50% or more.
In order for the reflective layer 6 to ensure high durability (high corrosion resistance), Ag is preferably used as an alloy rather than pure silver.
[0053]
Among these, it is preferable to contain 0.1 to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au, and rare earth metals. When two or more of Ti, Zn, Cu, Pd, Au, and rare earth metal are included, each may be 0.1 to 15 atomic%, but the total of these is preferably 0.1 to 15 atomic%. .
[0054]
A particularly preferable alloy composition contains 0.1 to 15 atomic% of at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au, containing Ag as a main component, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Among the rare earth metals, neodymium is particularly preferable. Specifically, AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, and the like.
[0055]
As the reflective layer 6, a layer made only of Au is preferable because of its high durability (high corrosion resistance). However, it is more expensive than Ag alloy.
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 6 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or below the reflective layer in order to improve reflectivity, improve recording characteristics, and improve adhesion.
(7) Intermediate resin layer 4
The intermediate resin layer 4 needs to be transparent and can be formed with grooves and pits by unevenness. Further, it is preferable that the adhesive strength is high and the shrinkage rate at the time of curing and bonding is small, the shape stability of the medium is high.
[0056]
The intermediate resin layer 4 is preferably made of a material that does not damage the dye recording layer 5. However, since the intermediate resin layer 4 is usually made of a resin, it is easily compatible with the dye recording layer 5. In order to prevent this and prevent damage, it is desirable to provide a buffer layer described later between the two layers.
Furthermore, the intermediate resin layer 4 is preferably made of a material that does not damage the translucent reflective layer 3. However, a buffer layer described later can be provided between both layers in order to suppress damage.
[0057]
In the present invention, it is preferable to accurately control the thickness of the protective layer. The thickness of the protective layer is usually preferably 5 μm or more. In order to separately apply focus servo to the two recording layers, it is necessary to have a certain distance between the two recording layers. Although it depends on the focus servo mechanism, it is usually required to be 5 μm or more, preferably 10 μm or more. In general, the higher the numerical aperture of the objective lens, the smaller the distance tends to be.
[0058]
However, if it is too thick, it takes time to adjust the focus servo to the two recording layers, and the moving distance of the objective lens becomes long, which is not preferable. Moreover, since there are problems such as requiring time for curing and lowering productivity, the thickness is usually preferably 100 μm or less. The intermediate resin layer 4 is provided with irregularities in a spiral shape or concentric shape to form grooves and lands. Normally, information is recorded / reproduced in / from the dye recording layer 5 using such grooves and / or lands as recording tracks. Usually, since the dye recording layer 5 is formed by coating, it becomes thick at the groove and is suitable for recording and reproduction. In the present invention, it is preferable that the groove of the intermediate resin layer 4, that is, the convex portion with respect to the light incident direction is the recording track 12. Here, a recessed part and a convex part say the recessed part and convex part with respect to the incident direction of light, respectively. Usually, the groove width is about 200 to 500 nm, and the groove depth is about 120 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, it may have uneven pits such as land prepits as necessary.
[0059]
From the viewpoint of cost, such irregularities are preferably produced by transferring and curing from a resin stamper having irregularities to a curable resin such as a photocurable resin. Hereinafter, such a method may be referred to as a 2P method.
Examples of the material of the intermediate resin layer 4 include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin (including a delayed curable type), and the like.
[0060]
A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent to prepare a coating solution, applying the solution, and drying. The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiating with ultraviolet light. There are various types of ultraviolet curable resins, and any of them can be used as long as it is transparent. 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.
[0061]
As a coating method, a method such as a spin coating method or a casting method is used as in the recording layer, and among these, the spin coating method is preferable. Alternatively, a resin having a high viscosity can be formed by screen printing or the like. It is preferable to use an ultraviolet curable resin that is liquid at 20 to 40 ° C. because it can be applied without using a solvent. The viscosity is preferably adjusted to 20 to 1000 mPa · s.
[0062]
As the ultraviolet curable adhesive, there are a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, both of which can be used.
As the radical ultraviolet curable adhesive, all known compositions can be used, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, monofunctional (meth) acrylate or polyfunctional (meth) acrylate can be used as the polymerizable monomer component. These can be used alone or in combination of two or more. Here, in the present invention, acrylate and methacrylate are collectively referred to as (meth) acrylate.
[0063]
Examples of the polymerizable monomer that can be used in the present invention include the following. Examples of the monofunctional (meth) acrylate include methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, Nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone modified tetrahydrofurfuryl, isobornyl , (Meth) acrylate having a group such as dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like.
[0064]
Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. Di (meth) such as neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of acrylate, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, neopentyl glycol Diol di (meth) acrylate obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A, triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane Di or tri (meth) acrylate, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) Acrylate, poly (meth) acrylate of dipentaerythritol, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkylated phosphoric acid (meth) acrylate, etc. It is.
[0065]
Moreover, what can be used together with the polymerizable monomer includes polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate and the like as polymerizable oligomers.
Furthermore, as the photopolymerization initiator used in the present invention, any known one that can cure an ultraviolet curable compound represented by the polymerizable oligomer and / or polymerizable monomer to be used can be used. As the photopolymerization initiator, a molecular cleavage type or a hydrogen abstraction type is suitable for the present invention.
[0066]
Examples of such include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- ( 4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, etc. are preferably used, and other molecular cleavage types 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Propan-1-one and -Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one or the like may be used in combination, and hydrogen extraction photopolymerization initiators such as benzophenone, 4-phenylbenzophenone, and isophthalphenone 4-benzoyl-4′-methyl-diphenyl sulfide and the like can be used in combination.
[0067]
Examples of sensitizers for photopolymerization initiators include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzyl. An amine that does not cause an addition reaction with the polymerizable component, such as an amine and 4,4′-bis (diethylamino) benzophenone, can also be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that are excellent in solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.
[0068]
Further, as the cationic ultraviolet curable adhesive, all known compositions can be used, and an epoxy resin containing a cationic polymerization type photoinitiator corresponds to this. Examples of cationic polymerization type photoinitiators include sulfonium salts, iodonium salts, and diazonium salts.
An example of an iodonium salt is as follows. Diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate, bis (dodecylphenyl) iodonium hexafluoroantimonate Bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium hexafluorophosphate, 4-methylphenyl-4 -(1-Methylethyl) phenyliodonium hexaful Roanchimoneto, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrakis (pentafluorophenyl) borate, and the like.
[0069]
The epoxy resin can be any of various types such as bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. It doesn't matter.
As the epoxy resin, it is preferable to use an epoxy resin having a low free chlorine and chlorine ion content so as not to damage the reflective layer. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.
[0070]
The ratio of the cationic polymerization type photoinitiator per 100 parts by weight of the cationic ultraviolet curable resin is usually 0.1 to 20 parts by weight, preferably 0.2 to 5 parts by weight. A known photosensitizer can be used in combination in order to use the near-ultraviolet region and the visible region of the ultraviolet light source more effectively. Examples of the photosensitizer at this time include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, and acetophenone.
[0071]
In addition, UV curable adhesives include, as necessary, other additives such as thermal polymerization inhibitors, antioxidants typified by hindered phenols, hindered amines, phosphites, plasticizers and epoxy silanes, mercapto. Silane coupling agents represented by silane, (meth) acrylic silane and the like can also be blended for the purpose of improving various properties. These are selected from those having excellent solubility in ultraviolet curable compounds and those that do not impair ultraviolet transparency.
(8) Adhesive layer 7
The adhesive layer 7 does not need to be transparent, but it is preferable that the adhesive strength is high and the shrinkage rate at the time of curing and bonding is small, so that the medium has high shape stability.
[0072]
The adhesive layer 7 is preferably made of a material that does not damage the reflective layer 6. However, a known inorganic or organic protective layer may be provided between both layers in order to suppress damage.
In the present invention, the thickness of the adhesive layer 7 is usually preferably 2 μm or more. In order to obtain a predetermined adhesive strength, a certain film thickness is required. More preferably, it is 5 μm or more. However, in order to make the medium as thin as possible, and there is a problem that productivity is reduced due to the time required for curing, 100 μm or less is usually preferable.
[0073]
The material of the adhesive layer 7 can be the same as the material of the intermediate resin layer 4, and a pressure-sensitive double-sided tape or the like can also be used. The adhesive layer 7 can be formed by sandwiching and pressing a pressure-sensitive double-sided tape between the reflective layer 6 and the substrate 8.
(9) Other layers
In the above laminated structure, any other layer may be sandwiched as necessary. Alternatively, any other layer may be provided on the outermost surface of the medium. Specifically, a buffer layer may be provided between the translucent reflective layer 3 and the intermediate resin layer 4, between the intermediate resin layer 4 and the dye recording layer 5, between the reflective layer 6 and the adhesive layer 7, and the like.
[0074]
The buffer layer prevents the two layers from mixing and prevents compatibility. The buffer layer may also serve other functions than preventing the mixing phenomenon. Further, another intermediate layer may be interposed as required.
The material of the buffer layer is not compatible with the dye recording layer 5 or the intermediate resin layer 4 and needs to have a certain degree of light transmission, but known inorganic substances and organic substances can be used. In view of characteristics, an inorganic material is preferably used. For example, (1) metal or semiconductor, (2) metal or semiconductor oxide, nitride, sulfide, oxysulfide, fluoride or carbide, or (3) amorphous carbon is used. Among them, a layer made of a substantially transparent dielectric or a very thin metal layer (including an alloy) is preferable.
[0075]
Specifically, silicon oxide, particularly silicon dioxide, oxides such as zinc oxide, cerium oxide, yttrium oxide; sulfides such as zinc sulfide and yttrium sulfide; nitrides such as silicon nitride; silicon carbide; oxide and sulfur And the following alloys are suitable. Further, a mixture of about 30:70 to 90:10 (weight ratio) of silicon oxide and zinc sulfide is also suitable. In addition, a mixture of sulfur and yttrium dioxide is mixed with zinc oxide (Y₂O₂S-ZnO) is also suitable.
[0076]
As the metal or alloy, silver or a material containing 0.1 to 15 atomic% of at least one element selected from the group consisting of titanium, zinc, copper, palladium, and gold, which is mainly composed of silver, is preferable. is there. Further, those containing silver as a main component and containing 0.1 to 15 atomic% of at least one rare earth element are also suitable. As this rare earth, neodymium, praseodymium, cerium and the like are suitable.
[0077]
In addition, a resin layer may be used as long as it does not dissolve the dye in the recording layer when the buffer layer is produced. In particular, a polymer film that can be produced by vacuum deposition or CVD is useful.
The thickness of the buffer layer is preferably 2 nm or more, more preferably 5 nm or more. If the thickness of the buffer layer is excessively thin, there is a possibility that the prevention of the above mixing phenomenon will be insufficient. However, it is preferably 2000 nm or less, more preferably 500 nm or less. If the buffer layer is excessively thick, it is not only necessary for preventing mixing but also may reduce light transmittance. In the case of a layer made of an inorganic material, it takes a long time to form a film, and the productivity may be lowered or the film stress may be increased. In particular, in the case of a metal, about 20 nm or less is preferable because the light transmittance is excessively lowered.
[0078]
A protective layer may be provided to protect the recording layer and the reflective layer. The material of the protective layer is not particularly limited as long as it can protect the recording layer and the reflective layer from external force. Examples of the material of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of inorganic substances include silicon oxide, silicon nitride, and MgF.₂, SnO₂Etc.
[0079]
A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent to prepare a coating solution, and applying and drying the coating solution. The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiation with UV light. As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.
[0080]
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 recording 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 50 μm in the present invention.
[0081]
Furthermore, in the optical recording medium, if necessary, a print receiving layer that can be filled in (printed) on various surfaces other than the recording / reproducing light incident surface by various printers such as ink jet and thermal transfer, or various writing tools. May be provided.
Alternatively, two optical recording media having this layer structure and two first recording substrates may be bonded to form a larger capacity medium having four recording layers.
[2] Manufacturing method of optical recording medium
Next, a preferred example of the method for producing an optical recording medium according to the present invention will be described with reference to FIGS. FIG. 2 is a schematic view for explaining the present production method.
[0082]
First, a transparent first substrate 1 having grooves, lands, and pre-pits formed on the surface with irregularities is formed by injection molding or 2P method based on a stamper. Next, at least the organic dye is dissolved in the solvent, and then the dye recording layer 2 is formed by forming a film on the surface of the transparent substrate 1 having the unevenness by spin coating or the like. Further thereon, a translucent reflective layer 3 is formed by sputtering or vapor-depositing an Ag alloy or the like.
[0083]
On this, when forming the intermediate resin layer 4, unevenness | corrugation is formed in the surface using a type | mold. As the mold, it is preferable to use a stamper made of resin from the viewpoint of productivity, cost, and the like.
The resin stamper 15 only needs to have sufficient peelability with respect to the resin to be the intermediate resin layer. Although it is not necessary to be transparent, it is desirable that the moldability is good and the shape stability is good. From the viewpoint of productivity and cost, the resin stamper 15 is desirably usable for a plurality of times of transfer. It is desirable that recycling after use is possible.
[0084]
The resin stamper 15 may have one or more separate layers 17 on the resin substrate 16, or may consist of only the resin substrate 16, but the latter is preferable from the viewpoint of productivity and cost.
First, the resin substrate 16 is produced by injection molding, 2P method, or the like, using a metal stamper having irregularities opposite to the above stamper (negative). The resin substrate 16 does not need to be transparent, but desirably has good moldability and good shape stability.
[0085]
Examples of such materials include those made of resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, and epoxy resins.
If the resin stamper 15 is configured to have one or more separate layers 17 on the resin substrate 16, the resin substrate needs to be a resin having high adhesion to the separate layer, and other high productivity such as moldability, Polycarbonate is preferable from the viewpoints of cost, low hygroscopicity, shape stability, and the like.
[0086]
If the resin stamper 15 includes only the resin substrate 16, it is desirable that the resin substrate has low adhesion with the resin constituting the intermediate resin layer 4 and high releasability. In addition, amorphous polyolefin is preferable from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability.
The thickness of the resin substrate 16 is preferably 0.5 mm or more from the viewpoint of shape stability and ease of handling. The upper limit of the thickness is not particularly limited, but usually 3 mm or less is sufficient.
[0087]
It is desirable that the separate layer 17 has low adhesion with the resin constituting the intermediate resin layer 4 and high peelability. In addition, it is desirable that irregularities that faithfully reflect the irregularities of the resin substrate are formed when the film is formed.
The material of the separate layer 17 is preferably a metal or an alloy from the viewpoint of peelability from the resin of the intermediate resin layer 4, and usually a metal selected from Ag, Au, Cu, Pt and Pd or an alloy thereof is used. The thickness of the separate layer 17 is required to be a certain thickness in order to ensure the peelability from the intermediate resin layer 4, and is preferably 2 nm or more. On the other hand, in order to faithfully reflect the unevenness of the substrate, it is desirable that it is not too thick, and usually 200 nm or less is preferable.
[0088]
An ultraviolet curable resin or the like is formed on the translucent reflective layer 3 formed on the substrate 1 by spin coating or the like, and then a resin stamper 15 is placed to transfer the unevenness to the ultraviolet curable resin. At this time, it is performed while adjusting the film thickness of the intermediate resin layer 4 to be within a predetermined range. In this state, the resin is cured by irradiating ultraviolet rays from the translucent reflective layer 3 side and the resin stamper 15 is peeled off when the resin is sufficiently cured, and the intermediate resin layer 4 having irregularities formed on the surface. Form. Alternatively, ultraviolet rays can be irradiated from the side of the medium. In any case, care must be taken so that the dye recording layer is not damaged by the ultraviolet rays.
[0089]
Subsequently, as shown in FIG. 1, at least the organic dye is dissolved in a solvent on the surface of the intermediate resin layer 4 having the unevenness, and then the dye recording layer 5 is formed by spin coating or the like. Further, the reflective layer 6 is formed by sputtering or vapor-depositing an Ag alloy or the like.
Further, the mirror substrate 8 is obtained by injection molding polycarbonate. An optical recording medium can be manufactured by laminating the mirror substrate 8 on the laminated structure of the substrate 1 through the adhesive layer 7. The adhesive layer 7 may be opaque or may have a slightly rough surface, and a delayed curing adhesive can be used without any problem. An adhesive layer 7 can be formed by applying an adhesive onto the reflective layer 6 by screen printing or the like and irradiating it with ultraviolet rays, and then placing and pressing the mirror substrate 8. Alternatively, the adhesive layer can be formed by using a pressure-sensitive double-sided tape and pressing the tape between the laminated structures A and B.
[3] Recording / reproducing method of optical recording medium
Next, a preferred example of the optical recording medium recording / reproducing method according to the present invention will be described.
[0090]
Recording on the optical recording medium of the present invention obtained as described above is performed by irradiating the recording layer with laser light focused to a diameter of about 0.5 to 1 μm from the first substrate side. In the portion irradiated with the laser beam, thermal deformation of the recording layer such as decomposition, heat generation, and melting due to absorption of laser beam energy occurs, and the optical characteristics change.
The recorded information is reproduced by reading the difference in reflectance between the portion where the optical characteristics change and the portion where the change does not occur with the laser beam.
[0091]
Recording and reproduction are individually performed on the two recording layers as follows. The first recording layer 2 and the second recording layer 5 can be distinguished from each other by the focus error signal obtained by the knife edge method, astigmatism method, Foucault method or the like on the focusing position of the focused laser. That is, when the objective lens that focuses the laser beam is moved up and down, S-shaped curves are obtained at the positions where the laser focusing position corresponds to the first recording layer and the second recording layer, respectively. Depending on which S-curve is used for the focus servo, it is possible to select which of the first recording layer and the second recording layer is to be recorded and reproduced.
[0092]
In the present invention, preferably, irregularities are formed on the first substrate and the intermediate resin layer, respectively, and recording / reproduction is performed using the convex portions of the first substrate and the convex portions of the intermediate resin layer as recording tracks.
Usually, since the dye recording layer is formed by coating, it becomes thick at the groove and is suitable for recording and reproduction. In the present invention, the groove portion of the first substrate 1, that is, the convex portion with respect to the light incident direction is the recording track 11, and the groove portion of the intermediate resin layer, that is, the convex portion with respect to the light incident direction is the recording track 12. Is preferred.
[0093]
The laser beam used for the optical recording medium of the present invention is N₂, He—Cd, Ar, He—Ne, ruby, semiconductor, dye laser, and the like are mentioned. A semiconductor laser is preferable because of its light weight, compactness, ease of handling, and the like.
The laser beam used is preferably as short as possible for high-density recording, but a laser beam of 350 to 530 nm is particularly preferable. Typical examples of such laser light include laser light having center wavelengths of 405 nm, 410 nm, and 515 nm.
[0094]
An example of laser light having a wavelength in the range of 350 to 530 nm can be obtained by using a high-power semiconductor laser of 405 nm, 410 nm blue or 515 nm blue-green, but for example, (a) the fundamental oscillation wavelength is Either a semiconductor laser capable of continuous oscillation of 740 to 960 nm, or (b) a solid laser capable of continuous oscillation excited by a semiconductor laser and having a fundamental oscillation wavelength of 740 to 960 nm is generated by a second harmonic generation element (SHG). wave
It can also be obtained by length conversion.
[0095]
The SHG may be any piezoelectric element that lacks inversion symmetry, but KDP, ADP, BNN, KN, LBO, a compound semiconductor, and the like are preferable. As a specific example of the second harmonic, in the case of a semiconductor laser having a fundamental oscillation wavelength of 860 nm, a harmonic of 430 nm, and in the case of a solid-state laser excited by a semiconductor laser, Cr-doped LiSrAlF₆430 nm of a double wave from a crystal (fundamental oscillation wavelength 860 nm) can be mentioned.
[0096]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist.
Example 1
First, by using a Ni stamper in which grooves and prepits are formed, polycarbonate is injection-molded to form a groove having a groove pitch of 0.74 μm, a groove width of 0.3 μm, and a groove depth of 150 to 180 nm and a diameter of 120 mm where prepits are formed. A substrate 1 having a thickness of 0.6 mm was obtained.
[0097]
Next, the metal-containing azo dye represented by the general formula (II) was dissolved in octafluoropentanol and adjusted to 2% by weight. This was dropped onto the substrate 1 and applied by a spinner method. After application, the recording layer 2 was formed by drying at 100 ° C. for 30 minutes. The maximum absorption wavelength (λmax) of this coating film was about 600 nm. Next, an Ag alloy of Ag-Cu (0.9 atomic%)-Au (1.0 atomic%)-Nd (0.7 atomic%) is sputtered to a thickness of 16 nm to form a translucent reflective layer 3. did. A protective layer made of an ultraviolet curable resin was provided on this to a thickness of 5 to 10 μm.
[0098]
Next, a resin stamper 15 was produced. In other words, by using a Ni stamper having unevenness substantially opposite to that of the Ni stamper used above, polycarbonate is injection-molded to obtain a land pitch of 0.74 μm, a land width of 0.3 μm, and a land height of 150 to 180 nm. A stamper substrate 16 having a diameter of 120 mm and a thickness of 0.6 mm on which prepits (convex shapes) were formed was obtained. Here, Ag was sputtered to a thickness of 60 nm to form a separate layer 17 to obtain a resin stamper 15.
[0099]
An ultraviolet curable resin (manufactured by Mitsubishi Rayon Co., Ltd.) was applied on the laminated structure of the substrate 1 thus manufactured, and the resin stamper 15 was placed with the uneven surface facing the substrate 1 side. Thereafter, ultraviolet rays are irradiated from the substrate 1 side through the semitransparent reflective layer 3, cured, and the resin stamper 15 is peeled off, so that an intermediate thickness of about 55 μm (measured value between the land portions) to which the unevenness is transferred. Resin layer 4 was formed.
[0100]
Subsequently, the same dye solution was applied and dried in the same manner to form the recording layer 5, and the same Ag alloy was sputtered to a thickness of 130 nm to form the reflective layer 6. A protective layer made of an ultraviolet curable resin was provided on this to a thickness of 5 to 10 μm.
Further, a mirror substrate 8 having a diameter of 120 mm and a thickness of 0.6 mm was obtained by injection molding of polycarbonate.
[0101]
An adhesive made of a cationic polymerization type ultraviolet curable resin (delay curable type, manufactured by Sony Chemical Co., SK7000) is applied by screen printing on the laminated structure thus produced, and then irradiated with ultraviolet rays to give a mirror substrate 8 And an adhesive layer 7 having a thickness of about 55 μm was obtained to produce an optical recording medium.
This optical recording medium was recorded / reproduced with a recording / reproduction evaluation machine having a wavelength of 650 nm and a numerical aperture of 0.65. The recording / reproducing light is incident from the substrate 1 side, and evaluation was performed using the convex portions of the first substrate and the concave portions of the second substrate as recording tracks. As a result, recording / reproducing was possible for both the dye recording layer 2 and the dye recording layer 5. there were.
[0102]
【The invention's effect】
According to the present invention, since at least two recording layers are provided and different information can be recorded, there is an advantage that the recording capacity can be dramatically increased as compared with the conventional optical recording medium.
In addition, this layer configuration has an advantage that if the light beam is incident from the first substrate side, both the first recording layer and the second recording layer can be recorded and reproduced satisfactorily. Thereby, since the user does not need to perform work such as inverting the medium, convenience is enhanced. The drive does not need to have two or more optical heads for recording / reproduction, and the drive can be made inexpensive with a simple configuration.
[0103]
Further, since the dye recording layer is close to the first substrate and the intermediate resin layer, there is an advantage that the resin layer is easily deformed due to recording, and the recording has a large modulation degree and excellent jitter characteristics.
Furthermore, since this medium can perform recording and reproduction with the same convex portion as the recording track in both the first recording layer and the second recording layer, there is no need to change the polarity of tracking depending on the layer, and good recording and reproduction can be performed relatively easily. There is also an advantage that it can be done.
[0104]
Furthermore, this layer configuration also has the advantage that the second substrate need not be transparent, so the range of material selection is widened. For example, the functions of the first substrate and the second substrate may be divided, and the second substrate may be made of a material having excellent shape stability to give the optical recording medium sufficient rigidity, thereby thinning the first substrate. it can. Since the objective lens can be brought closer to the recording layer, it is preferable because the recording density can be increased by increasing the numerical aperture of the lens and the capacity can be further increased.
[0105]
Alternatively, two optical recording media having this layer structure and two first recording substrates may be bonded to form a larger capacity medium having four recording layers.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of an optical recording medium according to the present invention.
FIG. 2 is a schematic view for explaining an example of a method for producing an optical recording medium according to the present invention.
FIG. 3 is a schematic diagram showing an example of a conventional optical recording medium.
[Explanation of symbols]
1 Transparent substrate
2 Dye recording layer
3 Translucent reflective layer
4 Intermediate resin layer
5 Dye recording layer
6 Reflective layer
7 Adhesive layer
8 Board
11 Recording track consisting of convex parts
12 Recording track consisting of convex parts
15 Resin stamper
16 Stamper board
17 Separate layer
21 Transparent substrate
22 Dye recording layer
23 Reflective layer
24 Adhesive layer

Claims (2)

On the transparent first substrate, it has a first recording layer containing a dye, a translucent reflective layer, an intermediate resin layer, a second recording layer containing a dye, a reflective layer, an adhesive layer, and a second substrate in this order. the intermediate resin layer and the second recording layer is contact, the result is uneven respectively formed on the first substrate and the intermediate resin layer, the result intermediate resin layer is a curable resin, the intermediate resin layer The optical recording medium is characterized in that the irregularities are formed by transferring and curing from a resin stamper made of amorphous polyolefin having irregularities to the curable resin . On the transparent first substrate, it has a first recording layer containing a dye, a translucent reflective layer, an intermediate resin layer, a second recording layer containing a dye, a reflective layer, an adhesive layer, and a second substrate in this order. The method of manufacturing an optical recording medium, wherein the intermediate resin layer and the second recording layer are in contact with each other, and irregularities are formed on the first substrate and the intermediate resin layer, respectively. An optical recording medium, wherein the layer is made of a curable resin, and the unevenness of the intermediate resin layer is formed by transferring and curing the resin stamper made of amorphous polyolefin having the unevenness to the curable resin. Manufacturing method.

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