JP2004318985A - Optical recording medium, recording and reproducing method of optical recording medium, and manufacturing method of optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain satisfactory recording and reproducing characteristics when the information of a coloring matter containing recording layer positioned on the far side from the light incident side is recorded and reproduced, in a one surface incidence optical recording medium having a plurality of the coloring matter containing recording layers. <P>SOLUTION: The optical recording medium is provided with a first and a second coloring matter-containing recording layers 22 and 25 and in the recording and reproducing method of the optical recording medium, information of the first and second coloring matter-containing recording layers 22 and 25 are recorded or reproduced by making the light incident from the one surface. The second coloring matter-containing recording layer 25 has a thick film part 25A and a thin film part 25B and recording or reproduction of the information of the second coloring matter-containing recording layer 25 is performed by making the light incident on the thin film part 25B via the first coloring matter containing recording layer 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４１】
（環Ａ^１及びＡ^２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Ｂ^１及びＢ^２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。
本光記録媒体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〜近マイクロ波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（代表的には７８０ｎｍ，８３０ｎｍなど）や、ＤＶＤ−Ｒに用いられるような波長６２０〜６９０ｎｍ程度の赤色レーザ（代表的には６３５ｎｍ，６５０ｎｍ，６８０ｎｍなど）、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。
【００４２】
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。
また第１記録層２２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。
【００４３】
さらに本光記録媒体の第１記録層２２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。
【００４４】
第１記録層２２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、本光記録媒体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。第１記録層２２の膜厚は通常、溝部とランド部で異なるが、本光記録媒体において第１記録層２２の膜厚は基板の溝部における膜厚を言う。
【００４５】
第１記録層２２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。
【００４６】
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第１記録層２２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。
【００４７】
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、第１記録層２２を形成する。
（ｃ）半透明反射層２３について
半透明反射層２３は、ある程度の光透過率を持つ反射層である。つまり、記録再生光の吸収が小さく、光透過率が４０％以上あり、かつ適度な光反射率（通常、３０％以上）を持つ反射層である。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、半透明反射層２３の上層（ここでは透明接着層２４）の浸み出しにより第１記録層２２が影響されないよう遮断性を持つことが望ましい。
【００４８】
高透過率を確保するために、半透明反射層２３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２５ｎｍ以下である。但し、第１記録層２２が半透明反射層２３の上層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。
【００４９】
半透明反射層２３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２３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。
【００５０】
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２３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。
【００５１】
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。
【００５２】
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。
【００５３】
半透明反射層２３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２３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。
【００５４】
半透明反射層２３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、第１基板２１と半透明反射層２３との間に、例えば反射率の向上，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又は接着層を設けても良い。例えば、第１基板２１上に、中間層（又は接着層），第１記録層２２，中間層（又は接着層），半透明反射層２３の順に積層させることで、第１基板２１と第１記録層２２との間に中間層（又は接着層）を設け、第１記録層２２と半透明反射層２３との間に中間層（又は接着層）を設けても良い。
（ｄ）透明接着層２４について
透明接着層２４は、透明である必要があるほか、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。
【００５５】
透明接着層２４の屈折率（記録光又は再生光の波長に対する屈折率）は、通常１．４０以上であり、好ましくは１．４５以上である。但し、通常１．７０以下であり、好ましくは１．６５以下である。
また、透明接着層２４は、第２記録層２５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、透明接着層２４は通常、樹脂からなるため第２記録層２５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間に後述のバッファー層２８を設けることが望ましい。
【００５６】
さらに、透明接着層２４は、半透明反射層２３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間に公知の無機系又は有機系の保護層を設けることもできる。
本光記録媒体において、透明接着層２４の膜厚は正確に制御することが好ましい。透明接着層２４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間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。
【００５７】
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。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。
透明接着層２４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。
【００５８】
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（加熱）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。
【００５９】
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。
【００６０】
なお、感圧式両面テープを用い、積層構造間にそのテープを挟んで押圧することによって接着層を形成することもできる。
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。
【００６１】
本光記録媒体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。
【００６２】
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。
【００６３】
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、本光記録媒体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光記録媒体に好適である。
【００６４】
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。
【００６５】
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。
【００６６】
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。
【００６７】
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。
【００６８】
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。
【００６９】
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。
（ｅ）第２記録層２５について
第２記録層２５は、通常、片面型記録媒体（例えばＣＤ−Ｒ，ＤＶＤ−Ｒ，ＤＶＤ＋Ｒ）等に用いる記録層よりも高感度である。本光記録媒体においては、入射した光ビームのパワーが第１記録層２２や半透明反射層２３の存在等で減少するため、約半分程度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。
【００７０】
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を用いることが望ましい。
ここで、第２記録層２５に用いる色素の屈折率（記録光又は再生光の波長に対する屈折率）は、通常１．００以上であり、好ましくは１．５０以上である。但し、通常３．００以下である。
【００７１】
また、第２記録層２５に用いる色素の消衰係数（記録光又は再生光の波長に対する消衰係数）は、通常０．５０以下であり、好ましくは０．３０以下である。消衰係数が大きすぎると、色素記録層による吸収が大きくなりすぎ、反射率が低くなってしまう。但し、記録が行なわれるためにはある程度吸収があることが好ましく、下限は特に無いが、通常０．００１以上である。
【００７２】
更に、第２記録層２５と反射層２６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。
第２記録層２５の材料、成膜方法等についてはほぼ第１記録層２２と同様に説明されるため、異なる点のみ説明する。
【００７３】
第２記録層２５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。ここで、第２記録層２５の膜厚は、通常、厚膜部における膜厚をいう。
【００７４】
第１記録層２２と第２記録層２５とに用いる材料は同じでも良いし異なっていてもよい。
（ｆ）反射層２６について
反射層２６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。
【００７５】
高反射率を確保するために、反射層２６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、生産のタクトタイムを短くし、コストを下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。
【００７６】
反射層２６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２６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。
【００７７】
中でも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２６は高耐久性（高耐食性）を確保するため、Ａｇは純銀よりも合金として用いるのが好ましい。
【００７８】
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。
【００７９】
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。
【００８０】
反射層２６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２６として用いることも可能である。
反射層２６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、反射層２６の上下に、例えば反射率の向上、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又は接着層を設けても良い。
（ｇ）第２基板２７について
第２基板２７は、光記録媒体がある程度の剛性を有するよう、形状安定性を備えるのが望ましい。即ち機械的安定性が高く、剛性が大きいことが好ましい。
【００８１】
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、ガラスからなるものを用いることができる。
或いは、第２基板２７は、複数の層から成るものであっても良く、例えばガラスや樹脂等の基板上に、光硬化樹脂等の放射線硬化樹脂からなる樹脂層を設けたもの等も第２基板として使用できる。
【００８２】
上述のように第１基板２１が十分な形状安定性を備えていない場合は、第２基板２７は特に形状安定性が高い必要がある。この点で吸湿性が小さいことが望ましい。
第２基板２７は透明である必要はないが、透明とする場合には、第２基板２７の屈折率（記録光又は再生光の波長に対する屈折率）は、通常１．４０以上であり、好ましくは１．４５以上である。但し、通常１．７０以下であり、好ましくは１．６５以下である。
【００８３】
このような材料としては、第１基板２１に用いうる材料と同じものが用い得るほか、例えば、Ａｌを主成分とした例えばＡｌ−Ｍｇ合金等のＡｌ合金基板や、Ｍｇを主成分とした例えばＭｇ−Ｚｎ合金等のＭｇ合金基板、シリコン、チタン、セラミックスのいずれかからなる基板やそれらを組み合わせた基板などを用いることができる。
【００８４】
なお、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、上述の樹脂が好ましく、特に、ポリカーボネートが好ましい。耐薬品性、低吸湿性などの点からは、非晶質ポリオレフィンが好ましい。また、高速応答性などの点からは、ガラス基板が好ましい。
光記録媒体に十分な剛性を持たせるために、第２基板２７はある程度厚いことが好ましく、厚さは０．３ｍｍ以上が好ましい。但し薄いほうが記録再生装置の薄型化に有利であり、好ましくは３ｍｍ以下である。より好ましくは１．５ｍｍ以下である。
【００８５】
第１基板２１と第２基板２７の好ましい組合せの一例は、第１基板２１と第２基板２７とが同一材料からなり、厚さも同一である。剛性が同等でバランスが取れているので、環境変化に対しても媒体として変形しにくく好ましい。この場合、環境が変化したときの変形の程度や方向も両基板で同様であると好ましい。
他の好ましい組合せの一例は、第１基板２１が０．１ｍｍ程度と薄く、第２基板２７が１．１ｍｍ程度と厚いものである。対物レンズが記録層に近づきやすく記録密度を上げやすいため好ましい。このとき第１基板２１はシート状であってもよい。
【００８６】
第２基板２７には、情報の記録又は再生の際に記録／再生光（記録／再生ビーム；例えばレーザ光）を案内するために用いられる溝（案内溝）３２が螺旋状又は同心円状に設けられる。このように第２基板２７に溝３２を設けると、第２基板２７の表面上に凹凸ができ、その凹部（溝）をグルーブといい、凸部をランドという。なお、第２基板２７上の溝３２は、光の入射方向に対して凹部となる。
【００８７】
ここでは、第２記録層２５は、第２基板２７上に形成された反射層２６上に塗布形成されるので、第２基板２７のグルーブ（凹部）で膜厚が厚くなり（この部分を厚膜部という）、第２基板２７のランド（凸部）で膜厚が薄くなる（この部分を薄膜部という）。
本実施形態では、ランド記録を行なう場合には、第２基板２７の溝３２の溝壁を、所定の振幅，所定の周波数で半径方向に僅かに蛇行させることで、ランドにウォブルが設けられる。また、グルーブにピットを設けることでアドレス情報や他の情報を予め記録しておいても良い。
【００８８】
このような凹凸を有する第２基板２７は、コストの観点から、凹凸を持つスタンパから樹脂を用いて射出成形により製造するのが好ましい。ガラス等の基体上に光硬化性樹脂等の放射線硬化性樹脂からなる樹脂層を設ける場合は、樹脂層に記録トラックなどの凹凸を形成してもよい。
（ｉ）バッファー層２８について
ここでは、透明接着層２４と第２記録層２５との間に中間層としてのバッファー層２８を設けている。
【００８９】
バッファー層２８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２８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２８の材料は、第２記録層２５や透明接着層２４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。
【００９０】
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（酸硫化物）；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と酸化亜鉛との混合物（Ｙ_２Ｏ_２Ｓ−ＺｎＯ）も好適である。
【００９１】
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。
【００９２】
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２８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２８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２８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おそれもある。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。
【００９３】
なお、このほか、半透明反射層２３と透明接着層２４との間などに中間層としてのバッファー層を設けてもよい。
（ｊ）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。
【００９４】
具体的には、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、ＭｇＦ_２、ＳｎＯ_２等が挙げられる。
【００９５】
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。
【００９６】
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、本光記録媒体においては、１〜５０μｍが好ましい。
【００９７】
更に、上記光記録媒体には、必要に応じて、記録光又は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、本層構成の他に記録層を設けて、記録層を３層以上としても良い。また、本層構成の光記録媒体を２枚、第１基板２１を外側にして貼合わせて、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。
【００９８】
ところで、上述のように、２つの色素含有記録層２２，２５を有する片面入射型光記録媒体では、光入射側（片面側）に近い側の第１色素含有記録層２２と遠い側の第２色素含有記録層２５とを有するものとなる。このため、光を入射させる側から遠い側に位置する第２色素含有記録層２５への情報の記録又は再生は、第１色素含有記録層２２を介して光を入射させることによって行なわれることになる。
【００９９】
このような片面入射型光記録媒体では、第１色素含有記録層２２の凹部（厚膜部２２Ａ）に記録トラックを設ければ良好な記録再生特性が得られるのに対し、第２色素含有記録層２５の凹部（厚膜部２５Ａ）に記録トラックを設けると、良好な記録再生特性（例えば反射率，極性，最大信号振幅など）が得られない場合がある。
【０１００】
そこで、本実施形態にかかる光記録媒体では、厚膜部２２Ａ及び薄膜部２２Ｂを有する第１色素含有記録層２２と、厚膜部２５Ａ及び薄膜部２５Ｂを有する第２色素含有記録層２５とを備える光記録媒体において、良好な記録再生特性が得られるようにすべく、光入射側（片面側）に近い側の第１色素含有記録層２２には、その厚膜部２２Ａに記録トラックを設け、光入射側から遠い側の第２色素含有記録層２５には、その薄膜部２５Ｂに記録トラックを設けるようにしている。
【０１０１】
上述のように、第２記録層２５では、薄膜部２５Ｂに記録すると、記録再生特性を良好なものとすることができるのは、以下の影響があるためであると推定される。
つまり、記録トラックにトラッキングを行ない、良好に記録又は再生するためには、光ビームを照射した場合の凹部（非トラック部）と凸部（トラック部）との位相差（光路長差）が重要となる。
【０１０２】
第１記録層２２では、凹部における第１記録層２２と半透明反射層２３との界面からの反射光と、凸部における同界面からの反射光との差が光路長差にあたる。この光路長差は、主に、第１記録層２２の凹部と凸部の光入射側の面同士の距離（第１記録層２２の薄膜部２２Ｂの第１基板２１側の面と、厚膜部２２Ａの第１基板２１側の面との距離）ｄ１（図１参照）と、第１記録層２２の凹部と凸部における膜厚差と、第１記録層２２の複素屈折率と、第１基板２１の複素屈折率とから求められる。
【０１０３】
一方、第２記録層２５では、凹部における第２記録層２５と反射層２６との界面からの反射光と、凸部における同界面からの反射光との差が光路長差にあたる。この光路長差は、主に、第２記録層２５の凹部と凸部の光入射側の面同士の距離［第２記録層２５の薄膜部２５Ｂの透明接着層（中間層）２４側の面と、厚膜部２５Ａの透明接着層２４側の面との距離］ｄ２（図１参照）と、第２記録層２５の凹部と凸部における膜厚差と、第２記録層２５の複素屈折率と、透明接着層２４の複素屈折率とから求められる。
【０１０４】
この場合、ｄ２はｄ１と必然的に異なってしまう。つまり、記録層を塗布して溝がある程度埋まった表面部の凹凸なので、ｄ２はｄ１に比べてかなり小さくなってしまう。
このため、光路長差、ひいては位相差が第１記録層２２とかなり異なる挙動を示し、このため、第２記録層２５では薄膜部２５Ｂに記録するのが好ましくなったと考えられる。
【０１０５】
ところで、第２記録層２５の薄膜部２５Ｂに記録トラックを設けるには、第２記録層２５の薄膜部２５Ｂを記録層として機能させるのに必要な厚さを確保する必要がある。つまり、第２記録層２５の薄膜部２５Ｂの厚さ（Ｌ膜厚）を所定厚さ（例えば７０ｎｍ）以上にするのが好ましい。例えば、色素を含む溶液をスピンコートすることによって第２記録層２５を形成する場合には、記録層塗布条件としての色素濃度を変えたり、スピン回転数を変えたりすることで、第２記録層２５の膜厚を所定厚さ以上にすることができる。
【０１０６】
ここで、第２記録層２５の厚膜部２５Ａと薄膜部２５Ｂとの膜厚差は、記録再生波長をλとし、第２記録層２５の屈折率をｎとして、１／１００×λ／ｎ以上とするのが好ましい。より好ましくは２／１００×λ／ｎ以上とし、さらに好ましくは３／１００×λ／ｎ以上とする。
但し、膜厚差は、１／３×λ／ｎ以下とするのが好ましい。より好ましくは１／４×λ／ｎ以下とし、さらに好ましくは１／５×λ／ｎ以下とする。
【０１０７】
具体的には、記録再生波長をλ＝６５０ｎｍ、第２記録層２５の屈折率をｎ＝２．２とすると、第２記録層２５の厚膜部２５Ａと薄膜部２５Ｂとの膜厚差は、３ｎｍ以上とするのが好ましい。より好ましくは６ｎｍ以上とし、さらに好ましくは９ｎｍ以上とする。一方、膜厚差は、９８ｎｍ以下とするのが好ましい。より好ましくは７４ｎｍ以下とし、さらに好ましくは５９ｎｍ以下とする。
【０１０８】
一方、第１記録層２２の厚膜部２２Ａと薄膜部２２Ｂとの膜厚差は、記録再生波長をλとし、第１記録層２２の屈折率をｎとして、１／３０×（λ／ｎ）以上とするのが好ましい。より好ましくは２／３０×（λ／ｎ）以上とし、さらに好ましくは３／３０×（λ／ｎ）以上とする。
但し、膜厚差は、４／４×（λ／ｎ）以下とするのが好ましい。より好ましくは４／５×（λ／ｎ）以下とし、さらに好ましくは４／６×（λ／ｎ）以下とする。
【０１０９】
具体的には、記録再生波長をλ＝６５０ｎｍ、第１記録層２２の屈折率をｎ＝２．２とすると、第１記録層２２の厚膜部２２Ａと薄膜部２２Ｂとの膜厚差は、１０ｎｍ以上とするのが好ましい。より好ましくは２０ｎｍ以上とし、さらに好ましくは３０ｎｍ以上とする。一方、膜厚差は、２９５ｎｍ以下とするのが好ましい。より好ましくは２３６ｎｍ以下とし、さらに好ましくは１９７ｎｍ以下とする。
【０１１０】
本実施形態では、第１記録層２２の厚膜部２２Ａ及び薄膜部２２Ｂは、光入射側に位置する第１基板２１の凹部及び凸部にそれぞれ対応して形成されるため、第１基板２１のグルーブ（凹部）、即ち、光の入射方向に突出する第１記録層２２の凸部（厚膜部２２Ａ）に記録トラックを設けるようにしている。
このため、光記録媒体の情報の記録又は再生は、第１基板２１のグルーブ（凹部）、即ち第１記録層２２の凸部（厚膜部２２Ａ）に光を入射させて（照射して）情報の記録又は再生を行なうことになる。
【０１１１】
一方、本実施形態では、第２記録層２５の厚膜部２５Ａ及び薄膜部２５Ｂは、光入射側とは反対側に位置する第２基板２７の凹部及び凸部にそれぞれ対応して形成されるため、第２基板２７のランド（凸部）、即ち、光の入射方向に突出する第２記録層２５の凸部（薄膜部２５Ｂ）に記録トラックを設けるようにしている。
【０１１２】
このため、光記録媒体の情報の記録又は再生は、第２基板２７のランド（凸部）、即ち第２記録層２５の凸部（薄膜部２５Ｂ）に光を入射させて（照射して）情報の記録又は再生を行なうことになる。
なお、本実施形態では、第１基板２１のグルーブに記録トラックを設ける一方、第２基板２７のランドに記録トラックを設けるため、それぞれの記録層の情報の記録又は再生の際にはトラッキング極性を変えることが必要になる場合がある。
【０１１３】
ところで、本実施形態では、第２基板２７のランドに記録トラックを設けるようにしているが（ランド記録）、第２基板２７の溝３２の深さを、一般的な色素系の光記録媒体の溝の深さよりも浅くすることで、第２記録層２５の情報の記録又は再生を行なうのに十分な反射率が得られるようにすれば、ＤＶＤ−ＲＯＭとの互換性が取り易くなる。また、第２基板２７の溝の深さが浅くても良くなると、成形性が良くなり、案内溝を有する第２基板２７の生産性も向上する（量産性）。
【０１１４】
具体的には、以下のように第２基板２７の溝３２の深さを設定すれば良い。
まず、第２基板２７の溝３２の深さ（溝深さ）は、記録再生波長をλとすると、１／１００×λ以上とするのが好ましい。より好ましくは２／１００×λ以上とし、さらに好ましくは３／１００×λ以上とするのが好ましい。トラッキングを良好にかけるためには、ある程度の深さがある方が好ましいからである。
【０１１５】
例えば、記録再生波長をλ＝６５０ｎｍとすると、第２基板２７の溝３２の深さは、７ｎｍ以上とするのが好ましい。より好ましくは１３ｎｍ以上とし、さらに好ましくは２０ｎｍ以上とする。
但し、第２基板２７の溝３２の深さは、１／６×λ以下とするのが好ましい。より好ましくは１／８×λ以下とし、さらに好ましくは１／１０×λ以下とする。これは、十分な反射率を得るためには、溝を深くしすぎないことが望ましいためである。
【０１１６】
例えば、第２基板２７の溝３２の深さは、記録再生波長をλ＝６５０ｎｍとすると、１０８ｎｍ以下とするのが好ましい。より好ましくは８１ｎｍ以下とし、さらに好ましくは６５ｎｍ以下とする。
また、第２基板２７の溝３２の幅（溝幅，Ｇ幅；半値幅）は、トラックピッチをＴとして、１／１０×Ｔ以上とするのが好ましい。より好ましくは２／１０×Ｔ以上とし、さらに好ましくは３／１０×Ｔ以上とする。これは、溝幅が狭すぎると、トラッキングがかかりにくくなる傾向があるからである。
【０１１７】
例えば、トラックピッチを７４０ｎｍとすると、第２基板２７の溝３２の幅は、７４ｎｍ以上とするのが好ましい。より好ましくは１４８ｎｍ以上とし、さらに好ましくは２２２ｎｍ以上とする。
但し、第２基板２７の溝３２の幅は、９／１０×Ｔ以下とするのが好ましい。より好ましくは８／１０×Ｔ以下とし、さらに好ましくは７／１０×Ｔ以下とする。これは、溝幅が広すぎると、トラッキングがかかりにくくなり、また、記録を良好に行なうのが難しくなる傾向があるからである。
【０１１８】
例えば、トラックピッチを７４０ｎｍとすると、第２基板２７の溝３２の幅は、６６６ｎｍ以下とするのが好ましい。より好ましくは５９２ｎｍ以下とし、さらに好ましくは５１８ｎｍ以下とする。
上述のように、本実施形態では、第２基板２７の溝３２の深さが、一般的な色素系光記録媒体の溝の深さよりも浅くなるようにしているが、第２基板２７の溝３２の深さは、第１基板２１の溝３１の深さよりも浅くなるようにするのが好ましい。
【０１１９】
また、第２基板２７の溝３２の深さを一般的な光記録媒体の溝の深さよりも浅くすることで、第２記録層２５の情報の記録又は再生を行なうのに十分な反射率が得られるようになるため、第２記録層２５の薄膜部２５Ｂ又は厚膜部２５Ａの双方を記録トラックとして用いることができる場合もあると考えられる。つまり、第２基板２７のランド（凸部）、即ち第２記録層２５の凹部（薄膜部２５Ｂ）に光を入射させて（照射して）情報の記録又は再生を行なうこともできるし、第２基板２７のグルーブ（凹部）、即ち第２記録層２５の凸部（厚膜部２５Ａ）に光を入射させて（照射して）情報の記録又は再生を行なうこともできる。
【０１２０】
通常は、第２基板２７の溝３２の深さを、第１基板２１の溝３１の深さの９０％以下とするのが好ましく、より好ましくは８０％以下であり、更に好ましくは７０％以下である。但し、通常、第１基板２１の溝３１の深さの５％以上であり、好ましくは１０％以上である。
（２）光記録媒体の製造方法
次に、上述したように構成される光記録媒体の製造方法について説明する。
【０１２１】
まず、透明な第１基板２１上に、色素を含む第１記録層２２、半透明反射層２３をこの順に有する積層構造（第１情報記録体）を作製する。一方、第２基板２７上に反射層２６、色素を含む第２記録層２５、バッファー層２８をこの順に有する積層構造（第２情報記録体）を作成する。そして、第１情報記録体と第２情報記録体とを、互いに記録層を内側にして透明接着層２４を介して貼り合わせる。
【０１２２】
具体的には、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２１を、射出成形または２Ｐ法（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方法）等により作製する。
次に、少なくとも有機色素を溶媒に溶解させた後、第１基板２１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て第１記録層２２を形成する。
【０１２３】
更にその上に、Ａｇ合金などをスパッタ、蒸着することにより半透明反射層２３を成膜して、第１情報記録体を作製する。
次に、表面に凹凸で溝及びランド、ピットが形成された第２基板２７を、射出成形または２Ｐ法等により作成する。第２基板２７の凹凸を有する側の表面に、Ａｇ合金などをスパッタ、蒸着することにより反射膜２６を成膜する。
【０１２４】
更に、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て第２記録層２５を形成する。
次いで、誘電体などをスパッタすることによりバッファー層２８を成膜して、第２情報記録体を作製する。
そして、第１情報記録体上に紫外線硬化性樹脂等の接着剤を塗布したのち、第２情報記録体を載置し、高速回転、押圧等により接着剤を全面に広げる。これは、接着層の膜厚が所定範囲になるように調節しつつ行なう。
【０１２５】
その後、第１情報記録体側から半透明反射層２３を介して紫外線を照射し、紫外線硬化性樹脂等の接着剤を硬化させて接着させることで、光記録媒体が製造される。
なお、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。また、感圧式両面テープを用い、第１情報記録体と第２情報記録体との間にその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。或いは、遅延硬化型の接着剤を使用し、第１情報記録体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第２情報記録体を載置し、押圧しても接着層を形成できる。但し、遅延硬化型接着剤は通常、不透明である場合が多い。
【０１２６】
次に、案内溝（凹凸）を有する基板２１，２７の作製方法について説明する。例えば、これらの基板２１，２７に凹凸（溝）を形成するには、所望の凹凸を有する金属スタンパを用い、射出成形によって樹脂材に凹凸を転写することで第１基板２１を作製するとともに、その逆の凹凸を有する金属スタンパを用いて射出成形によって樹脂材に凹凸を転写することで第２基板２７を作製する方法がある。
【０１２７】
特に、記録トラックに、例えばウォブルを付与することで、同期情報，アドレス情報等をもたせることがある。
本実施形態では、上述したように、第１記録層２２の厚膜部２２Ａに記録トラックを設け、第２記録層２５の薄膜部２５Ｂに記録トラックを設けるため、第１基板２１の凹部及び第２基板２７の凸部にウォブルを付与することになる。
【０１２８】
第１基板２１の凹部にウォブルを付与する場合の手順は、次のようになる。
まず、ガラス基板／フォトレジスト上に、ビームを蛇行させながら露光し、現像し、凹凸原盤を得る。この凹凸原盤では、通常、凹部（溝部）にウォブルがある。
次に、この凹凸原盤を用いてスタンパを作製し、作製されたスタンパを用いて射出成形によって凹凸（溝，案内溝）を有する第１基板２１を作製する。この場合、スタンパの凸部にウォブルがあるため、第１基板２１の凹部にウォブルができることになる。
【０１２９】
しかしながら、第２基板２７の凸部にウォブルを付与するためには、スタンパの凹部にウォブルがあることが必要である。このため、上述の方法では第２基板２７の凸部にウォブルを付与することができない。
そこで、まず、上述の第１基板２１に凹凸（溝，案内溝）を形成するのに用いたスタンパと同様の手法でスタンパを作製する。但し、凹凸の形状（溝深さ，溝幅，蛇行の幅など）は第２基板２７に形成すべき凹凸に合わせて変更が必要である。
【０１３０】
次に、このスタンパから凹凸を転写して、逆の凹凸を有するネガ型スタンパを作製する。この場合、スタンパの凸部にウォブルがあるため、ネガ型スタンパの凹部にウォブルができることになる。
次に、このネガ型スタンパを用いて射出成形によって凹凸（溝，案内溝）を有する第２基板２７を作製する。この場合、ネガ型スタンパの凹部にウォブルがあるため、第２基板２７の凸部にウォブルができることになる。
（３）光記録媒体の記録再生方法
次に、本実施形態にかかる光記録媒体の記録再生方法について説明する。
【０１３１】
上述のように構成される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２１側から照射することにより行なう。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。
一方、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。
【０１３２】
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２２と第２記録層２５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２２に対応する位置と第２記録層２５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２２と第２記録層２５のどちらを記録再生するかを選択可能である。
【０１３３】
本実施形態では、第１記録層２２の情報の記録又は再生の際には、第１基板２１のグルーブ（凹部）、即ち第１記録層２２の凸部（厚膜部２２Ａ）に光を入射させて（照射して）情報の記録又は再生を行なう。一方、第２記録層２５の情報の記録又は再生の際には、第２基板２７のランド（凸部）、即ち第２記録層２５の凸部（薄膜部２５Ｂ）に光を入射させて（照射して）情報の記録又は再生を行なう。
【０１３４】
本実施形態の光記録媒体について使用されるレーザ光は、Ｎ_２、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。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。
【０１３５】
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ＬｉＳｒＡｌＦ_６結晶（基本発振波長８６０ｎｍ）からの倍波の４３０ｎｍなどが挙げられる。
（４）作用・効果
したがって、本実施形態にかかる光記録媒体，光記録媒体の製造方法及び光記録媒体の記録再生方法によれば、片面側から光を入射させて情報の記録又は再生を行なう複数の記録層２２，２５を有する光記録媒体において、光を入射させる側から遠い側に位置する第２記録層２５の薄膜部２５Ｂに光を入射させて第２記録層２５の情報の記録又は再生を行なうため、光を入射させる側から遠い側に位置する第２記録層２５の情報の記録又は再生に際して良好な記録再生特性（例えば反射率，極性，最大信号振幅など）が得られるという利点がある。この結果、複数の記録層２２，２５のいずれにおいても良好な記録再生特性が得られることになる。
（５）その他
なお、本実施形態では、貼り合わせ型のデュアルレイヤタイプの片面入射型ＤＶＤ−Ｒに本発明を適用した例を説明したが、これに限られるものではなく、片面側から光を入射させて情報の記録又は再生を行なう複数の色素含有記録層を有する光記録媒体であれば、他の構成の光記録媒体であっても本発明を適用することができる。
【０１３６】
例えば、図２に示すように、ディスク状の透明な（光透過性の）第１基板（第１光透過性基板）１上に、色素を含む第１記録層（第１色素含有記録層）２、半透明の反射層（半透明反射層）３、中間樹脂層（中間層）４、色素を含む第２記録層（第２色素含有記録層）５、反射層６、第２基板７８（接着層７と基体８とからなる）をこの順に有してなる、積層型のデュアルレイヤタイプの片面入射型ＤＶＤ−Ｒに本発明を適用することもできる。なお、符号１１，１２は案内溝（溝，凹部）である。
【０１３７】
この場合、光を入射させる側から遠い側に位置する第２記録層５の情報の記録又は再生には、第２基板７８に設けられる案内溝（溝，凹部）１２が用いられるため、十分な反射率が得られるにようにするためには、この案内溝１２の深さを、記録再生波長をλとして、１／１００×λ〜１／６×λの範囲内とすれば良い。
【０１３８】
また、良好な記録再生特性が得られるようにするためには、第２基板７８の溝（グルーブ，凹部）１２、即ち、第２記録層５の凹部（薄膜部）に記録トラックを設けるのが好ましい。つまり、第２基板７８の溝（グルーブ，凹部）１２、即ち第２記録層５の凹部（薄膜部）に光を入射させて（照射して）情報の記録又は再生を行なうようにするのが好ましい。
【０１３９】
なお、本発明は上記の実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で種々変形して実施することができる。
【０１４０】
【実施例】
次に、実施例によって本発明を更に詳細に説明する。なお、本発明は、以下の実施例によって限定されるものではない。
（光記録媒体の作製）
本発明にかかる光記録媒体は、例えば、案内溝を有する第１基板上に、少なくとも、第１の色素を含有する第１色素含有記録層と半透明反射層とを順次積層させてなる第１情報記録体と、案内溝を有する第２基板上に、少なくとも、反射層と第２の色素を含有する第２色素含有記録層とを順次積層させてなる第２情報記録体とを備え、第１情報記録体と第２情報記録体とを基板の反対側の面を対向させ、光学的に透明な接着層を介して貼り合わされてなる。
【０１４１】
以下、第２情報記録体の作製を中心に説明する。
まず、マザースタンパ（ネガ型スタンパ）を用い、射出成形によって、トラックピッチ７４０ｎｍ、所定の溝深さ及び溝幅の案内溝を有する、厚さ０．６ｍｍのポリカーボネート製の第２基板（屈折率１．５６）を作製した。
次に、この第２基板上に、Ａｇを９７ａｔｏｍ％以上含む銀合金をスパッタして反射層を形成した。
【０１４２】
次いで、この反射層上に、含金属アゾ色素のオクタフルオロペンタノール溶液を所定の塗布条件（色素濃度）でスピンコートし、１００℃で３０分乾燥して、第２色素含有記録層を形成した。ここでは、塗布条件を変えることで、第２色素含有記録層の膜厚が所定の膜厚になるようにした。本記録層の屈折率は２．２５、消衰係数は０．０２であった。
【０１４３】
次に、この第２色素含有記録層上に、Ａｇを９７ａｔｏｍ％以上含む銀合金，（ＺｎＳ）_８０（ＳｉＯ_２）_２０，ＳｉＯ_２のいずれかをスパッタしてバッファー層を形成し、その上に、紫外線硬化樹脂（日本化薬製ＳＰＣ−９２０）を膜厚約５〜７μｍの厚さにスピンコートして、保護層を形成した。
そして、通常、この保護層上に、ラジカル系紫外線硬化樹脂（接着剤）をスピンコートして塗布し、別途作製した記録層（第１記録層）を含む第１基板の反射層側と貼り合わせて、光記録媒体を作製する。
【０１４４】
但し、ここでは、第１情報記録体の影響をなくし、第２記録層の特性を精密に評価できるように、第１情報記録体としては、記録層及び半透明反射層を有しない、厚さ０．６ｍｍの溝のないポリカーボネート基板（屈折率１．５６）を用いた。硬化後の接着層の屈折率は１．５３であった。
（測定方法）
波長６５７ｎｍ（ＮＡ＝０．６５）の半導体レーザを搭載した評価機（パルステック社製ＤＤＵ−１０００，最大記録パワー１５ｍＷ）を用い、まず、未記録の第２記録層の反射率を測定し、次いで、記録線速度３．８ｍ／ｓ（１倍速）で、８−１６変調のＥＦＭ＋信号を、記録信号のアシンメトリーがほぼ０となる記録パワーで記録し、その反射率，記録信号の極性及び最大信号振幅（最長マークの振幅；いわゆるＭｏｄｕｌａｔｉｏｎ；Ｉ１４／Ｉ１４Ｈ）を測定した。
【０１４５】
なお、本実施例においては、反射率２５％以上を優れているとし、反射率３０％をより優れているとした。通常、ＤＶＤ−ＲＯＭと互換性を取るためには、第２記録層の未記録部の反射率は十数％あれば良い。本実施例は、第１記録層及び半透明反射層を有しないので、実際よりも反射率が高めに出る傾向があるが、本実施例において反射率２５％以上が得られれば、実際の第１情報記録体の影響を考慮しても十数％の反射率が得られると考える。
【０１４６】
また、ＤＶＤ−ＲＯＭ等との互換性を取るためには、記録信号の極性はＨｔｏＬが望ましい。
さらに、最大信号振幅は一般に大きい方が好ましい。通常、０．５以上が望ましく、更に望ましくは０．６以上である。
各実施例及び比較例の測定結果は、下記表１に示すようになった。
【０１４７】
【表１】

【０１４８】
（実施例１）
実施例１では、第２基板に、溝深さ６５ｎｍ（ほぼλ／１０に相当），溝幅（Ｇ幅）３２０ｎｍ，ランド幅（Ｌ幅）４２０ｎｍとなるように案内溝を形成した。
また、バッファー層はＡｇ合金をスパッタして形成した。そして、塗布条件としての色素濃度を３．５５ｗｔ％として含金属アゾ色素をスピンコートして第２記録層を形成した。
【０１４９】
このようにして形成した第２記録層の溝部分の膜厚（厚膜部，Ｇ膜厚）は８５ｎｍであり、ランド部分の膜厚（薄膜部，Ｌ膜厚）は７０ｎｍであった。つまり、第２記録層の厚膜部と薄膜部の膜厚差は１５ｎｍであった。
このようにして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定したところ、表１に示すように、反射率は４０．０％、記録信号の極性はＨｔｏＬ（Ｈｉｇｈ ｔｏ Ｌｏｗ）、最大信号振幅は０．７９であった。
（比較例１）
比較例１では、上述の実施例１と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は３０．７％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．１よりも小さかった（記録パワー１５ｍＷで記録した場合）。
【０１５０】
このように、同様にして作製した光記録媒体であっても、本比較例１のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例１のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例２）
実施例２では、第２基板に、溝深さ５０ｎｍ（ほぼλ／１３に相当），溝幅（Ｇ幅）４１０ｎｍ，ランド幅（Ｌ幅）３３０ｎｍとなるように案内溝を形成した。
【０１５１】
また、バッファー層はＳｉＯ_２をスパッタして形成した。そして、塗布条件としての色素濃度を３．５５ｗｔ％として含金属アゾ色素をスピンコートして第２記録層を形成した。
このようにして形成した第２記録層の溝部分の膜厚（厚膜部，Ｇ膜厚）は１０５ｎｍであり、ランド部分の膜厚（薄膜部，Ｌ膜厚）は７５ｎｍであった。つまり、第２記録層の厚膜部と薄膜部の膜厚差は３０ｎｍであった。
【０１５２】
このようにして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定したところ、表１に示すように、反射率は３６．４％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．７４であった。
このように、バッファー層をＳｉＯ_２とし、第２記録層の膜厚，溝形状を変えても良い記録再生特性が得られることがわかった。
（比較例２）
比較例２では、上述の実施例２と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は３０．９％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．３６であった。
【０１５３】
このように、同様にして作製した光記録媒体であっても、本比較例２のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例２のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例３）
実施例３では、バッファー層をＡｇ合金とした点、塗布条件としての色素濃度を４．４３ｗｔ％とすることで、第２記録層の溝部分の膜厚（厚膜部，Ｇ膜厚）を１３０ｎｍとし、ランド部分の膜厚（薄膜部，Ｌ膜厚）を９５ｎｍとした点（即ち、第２記録層の厚膜部と薄膜部の膜厚差を３５ｎｍとした点）以外は、上述の実施例２と同様にして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定したところ、表１に示すように、反射率は３１．１％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．７１であった。
【０１５４】
このように、バッファー層をＳｉＯ_２からＡｇ合金に代え、第２記録層の膜厚を変えても良い記録・再生特性が得られることがわかった。
（比較例３）
比較例３では、上述の実施例３と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は２９．１％、記録信号の極性はＨｔｏＬ、最大信号振幅はＬＳ（感度不良で記録不能；記録パワー１５ｍＷで記録した場合）であった。
【０１５５】
このように、同様にして作製した光記録媒体であっても、本比較例３のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例３のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例４）
実施例４では、バッファー層をＺｎＳ−ＳｉＯ_２とした以外は、上述の実施例３と同様にして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定したところ、表１に示すように、反射率は３８．２％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．６６であった。
【０１５６】
このように、バッファー層をＡｇ合金からＺｎＳ−ＳｉＯ_２に代えても良い記録・再生特性が得られることがわかった。
（比較例４）
比較例４では、上述の実施例４と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は３１．３％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．３１であった。
【０１５７】
このように、同様にして作製した光記録媒体であっても、本比較例４のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例４のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例５）
実施例５では、バッファー層をＳｉＯ_２とした以外は、上述の実施例３と同様にして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定したところ、表１に示すように、反射率は３６．１％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．７３であった。
【０１５８】
このように、バッファー層をＡｇ合金からＳｉＯ_２に代えても良い記録・再生特性が得られることがわかった。
（比較例５）
比較例５では、上述の実施例５と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は３１．２％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．３であった。
【０１５９】
このように、同様にして作製した光記録媒体であっても、本比較例５のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例５のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例６）
実施例６では、第２基板に、溝深さ３０ｎｍ（ほぼλ／２０に相当），溝幅（Ｇ幅）２２０ｎｍ，ランド幅（Ｌ幅）５２０ｎｍとなるように案内溝を形成した。
【０１６０】
また、バッファー層はＺｎＳ−ＳｉＯ_２をスパッタして形成した。そして、塗布条件としての色素濃度を３．１０ｗｔ％として含金属アゾ色素をスピンコートして第２記録層を形成した。
このようにして形成した第２記録層の溝部分の膜厚（厚膜部，Ｇ膜厚）は１１０ｎｍであり、ランド部分の膜厚（薄膜部，Ｌ膜厚）は７０ｎｍであった。つまり、第２記録層の厚膜部と薄膜部の膜厚差は４０ｎｍであった。
【０１６１】
このようにして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定したところ、表１に示すように、反射率は４３．９％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．７２であった。
このように、バッファー層をＺｎＳ−ＳｉＯ_２とする場合に、第２記録層の膜厚，溝幅，ランド幅を変えると、より良い記録・再生特性が得られることがわかった。
（比較例６）
比較例６では、上述の実施例６と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は３９．０％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．２２であった。
【０１６２】
このように、同様にして作製した光記録媒体であっても、本比較例６のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例６のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例７）
実施例７では、バッファー層をＳｉＯ_２とした以外は上述の実施例６と同様にして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は４９．５％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．５８であった。
【０１６３】
このように、バッファー層をＺｎＳ−ＳｉＯ_２からＳｉＯ_２に代えると、反射率は良くなるものの、最大信号振幅がやや悪くなるが、記録・再生に必要な特性は得られることがわかった。
（比較例７）
比較例７では、上述の実施例７と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は４３．２％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．１１であった。
【０１６４】
このように、同様にして作製した光記録媒体であっても、本比較例７のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例７のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例８）
実施例８では、バッファー層をＡｇ合金とした点、塗布条件としての色素濃度を３．５５ｗｔ％とすることで、第２記録層の溝部分の膜厚（厚膜部，Ｇ膜厚）を１３５ｎｍとし、ランド部分の膜厚（薄膜部，Ｌ膜厚）を９０ｎｍとした点（即ち、第２記録層の厚膜部と薄膜部の膜厚差を４５ｎｍとした点）以外は、上述の実施例６と同様にして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定したところ、表１に示すように、反射率は３３．９％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．７９であった。
【０１６５】
このように、バッファー層をＺｎＳ−ＳｉＯ_２からＡｇ合金に代え、第２記録層の膜厚を変えると、反射率はやや悪くなるものの、最大信号振幅は良くなり、記録・再生に必要な特性は得られることがわかった。
（比較例８）
比較例８では、上述の実施例８と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は３０．２％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．１よりも小さかった（記録パワー１５ｍＷで記録した場合）。
【０１６６】
このように、同様にして作製した光記録媒体であっても、本比較例８のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例８のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（実施例９）
実施例９では、バッファー層をＳｉＯ_２とした以外は上述の実施例８と同様にして作製した光記録媒体に、上述のような条件でランド記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は４４．２％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．５５であった。
【０１６７】
このように、バッファー層をＡｇ合金からＳｉＯ_２に代えると、反射率は良くなるものの、最大信号振幅がやや悪くなるが、記録・再生に必要な特性は得られることがわかった。
（比較例９）
比較例９では、上述の実施例９と同様にして作製した光記録媒体に、上述のような条件でグルーブ記録を行ない、反射率，記録信号の極性及び最大信号振幅を測定した。その結果、表１に示すように、反射率は４１．７％、記録信号の極性はＨｔｏＬ、最大信号振幅は０．１よりも小さかった（記録パワー１５ｍＷで記録した場合）。
【０１６８】
このように、同様にして作製した光記録媒体であっても、本比較例９のようにグルーブ記録を行なうと、記録・再生に必要な特性が得られないのに対し、実施例９のようにランド記録を行なえば、記録・再生に必要な特性が得られることがわかった。
（まとめ）
上述の各比較例１〜９のように、グルーブ記録とすると、光を入射させる側から遠い側に位置する第２色素含有記録層の情報の記録又は再生に必要な記録再生特性（反射率，極性，最大信号振幅）が得られないのに対し、上述の各実施例１〜９のように、ランド記録とすると、光を入射させる側から遠い側に位置する第２色素含有記録層の情報の記録又は再生に必要な記録再生特性（反射率，極性，最大信号振幅）が得られることがわかった。
【０１６９】
なお、上述の各実施例においては、第１情報記録体の影響をなくし、できるだけ精密に第２記録層の特性を評価するために、第１情報記録体として、記録層及び半透明反射層を有しない、溝のない基板を用いたが、通常の第１情報記録体を用いても、第２記録層の評価には大きな影響はない。
また、実施例１〜９の媒体では、記録層膜厚以外の構成を適宜選ぶことで、他の記録再生特性にも優れた光記録媒体を得ることができると思われる。
【０１７０】
【発明の効果】
以上詳述したように、本発明の光記録媒体，光記録媒体の記録再生方法及び光記録媒体の製造方法によれば、片面側から光を入射させて情報の記録又は再生を行なう複数の色素含有記録層を有する光記録媒体において、光を入射させる側から遠い側に位置する色素含有記録層の情報の記録又は再生に際し、良好な記録再生特性が得られるという利点がある。
【図面の簡単な説明】
【図１】本発明の一実施形態にかかる光記録媒体の全体構成を示す模式図である。
【図２】本発明の一実施形態にかかる他の光記録媒体の全体構成を示す模式図である。
【符号の説明】
１，２１ 第１基板
２，２２ 第１記録層（第１色素含有記録層）
３，２３ 半透明反射層
４ 中間樹脂層（中間層）
５，２５ 第２記録層（第２色素含有記録層）
６，２６ 反射層
７ 接着層
８ 基体
２７ 第２基板
２８ バッファー層
１１，１２，３１，３２ 溝（案内溝）
２２Ａ，２５Ａ 厚膜部
２２Ｂ，２５Ｂ 薄膜部
２４ 透明接着層（中間層）
７８ 第２基板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium having a plurality of recording layers for recording or reproducing information by irradiating light from one side, such as a DVD-R, a recording / reproducing method of the optical recording medium, and a method of manufacturing the optical recording medium. .
[0002]
[Prior art]
At present, various types of optical recording media such as CD-R, CD-RW, and MO are widely recognized as external storage devices in information processing devices such as computers because they can store a large amount of information and can be easily accessed at random. It is becoming popular. Further, it is desired to increase the storage density by increasing the amount of information to be handled.
[0003]
Among various optical recording media, optical disks having a recording layer containing an organic dye (also referred to as a dye-containing recording layer), such as CD-R, DVD-R, and DVD + R, are relatively inexpensive and compatible with read-only optical disks. It is widely used because of its properties.
As an example, a medium such as a CD-R, which is a typical optical disk having a dye-containing recording layer, has a dye-containing recording layer and a reflective layer on a transparent disk substrate in this order. It has a laminated structure with a protective layer to cover, and performs recording / reproduction with laser light through the substrate.
[0004]
A single-sided DVD-R (single-sided single-layer DVD-R) also has a dye-containing recording layer, a reflective layer, and a protective layer covering these layers in this order on a first transparent disk substrate. A laminated structure in which a so-called dummy disk on which a reflective layer is formed as necessary on a second disk substrate (which may be transparent or opaque) with or without an adhesive layer on the layer is provided. The recording / reproduction is performed by laser light from one side through the transparent disk substrate. The dummy disk may be a transparent or opaque disk substrate alone, or may have a layer other than the reflective layer.
[0005]
It should be noted that DVD + R has almost the same configuration as DVD-R, and will be represented in the description of DVD-R.
Also, in order to further increase the recording capacity of the optical recording medium, a single-sided DVD-R as described above is bonded to form a medium having two recording layers, and each recording layer is irradiated with laser light from both sides. (I.e., irradiate laser light from one side of the medium and perform recording / reproduction on the recording layer closer to this one side, and irradiate laser light also from the other side of the medium). Also, a double-sided DVD-R (double-sided dual-layer DVD-R) for performing recording / reproduction on the recording layer closer to the other side is also known.
[0006]
By the way, in recent years, in an optical recording medium having a plurality of recording layers, in order to prevent the recording / reproducing apparatus from becoming large-sized and complicated, and to enable continuous reproduction over a plurality of recording layers, a laser is used from one side. It is desired to realize a single-sided incident type optical recording medium (for example, a single-sided incident dual-layer DVD-R) that can record and reproduce data on and from these multiple recording layers by irradiating light.
[0007]
For this reason, for example, as a single-sided incident type optical recording medium having the following configuration, for example, a dual-layer single-sided incident type DVD-R having two recording layers (single-sided dual-layer DVD-R) has been proposed. (See, for example, Patent Document 1).
For example, a single-sided DVD-R of a laminated dual layer type has a first recording layer made of an organic dye capable of optically recording information by irradiating a recording laser beam on a first translucent substrate. A first reflective layer composed of a semi-transmissive reflective film capable of transmitting a part of a reproducing laser beam, an intermediate layer having a transmissive property with respect to a recording laser beam and a reproducing laser beam, A second recording layer made of an organic dye capable of optically recording information by irradiating a laser beam for use, a second reflective layer for reflecting a laser beam for reproduction, and a second substrate in this order.
[0008]
[Patent Document 1]
JP-A-11-066662
[0009]
[Problems to be solved by the invention]
In general, grooves (guide grooves, concave portions) for guiding recording light or reproduction light are provided spirally or concentrically on a substrate of an optical recording medium such as a CD or DVD.
For example, when a recording layer is applied on a substrate in order to produce an optical recording medium having a dye-containing recording layer (hereinafter, referred to as a recording layer) such as a CD-R or DVD-R, the recording is performed so that the concave portions on the substrate are filled. Since the layer is formed, the thickness of the recording layer is increased in the concave portion. Usually, when recording tracks are provided in such a thick portion (thick film portion; concave portion), it is said that recording / reproducing characteristics (for example, reflectance, maximum signal amplitude, polarity, etc.) are good. .
[0010]
Here, the maximum signal amplitude is a value obtained by standardizing the signal amplitude of the longest mark / longest space (14T mark / 14T space in a DVD-based medium) by the reflectance.
For this reason, all commercially available optical recording media are provided with recording tracks in the thick film portion (concave portion). The concave portions (grooves, grooves) of the substrate are convex portions when viewed from the incident side of light irradiated during recording or reproduction. That is, the dye-containing recording layer becomes a convex portion in the concave portion of the substrate.
[0011]
Currently, a single-sided incident type optical recording medium having a plurality of dye-containing recording layers (for example, a dual-layer single-sided incident type DVD-R) is being developed.
For example, in a single-sided incident type optical recording medium having two dye-containing recording layers, the first dye-containing recording layer closer to the light incident side (light incident side, one side) and the second dye-containing recording farther side. And a layer. In such a single-sided incident type optical recording medium, recording or reproduction of information on the second dye-containing recording layer is performed by irradiating light through the first dye-containing recording layer.
[0012]
In such a single-sided incidence type optical recording medium, good recording / reproducing characteristics can be obtained by providing a recording track in a concave portion (thick film portion) of the first dye-containing recording layer, similarly to a commercially available optical recording medium. However, if a recording track is provided in the concave portion (thick film portion) of the second dye-containing recording layer, good recording / reproducing characteristics may not be obtained.
The present invention has been made in view of such a problem, and in an optical recording medium having a plurality of dye-containing recording layers for recording or reproducing information by irradiating light from one side, from the side where light is incident. Provided are an optical recording medium, a recording / reproducing method for an optical recording medium, and a method for manufacturing an optical recording medium, which can obtain good recording / reproducing characteristics when recording or reproducing information on a dye-containing recording layer located on a far side. The purpose is to:
[0013]
[Means for Solving the Problems]
For this reason, the recording / reproducing method for an optical recording medium according to the present invention includes a first dye-containing recording layer and a second dye-containing recording layer having a thick portion and a thin film portion. A recording / reproducing method for an optical recording medium for recording or reproducing, wherein light is incident on a thin film portion of a second dye-containing recording layer to record or reproduce information (claim 1).
[0014]
In particular, the present invention is applied to an optical recording medium in which the thick film portion and the thin film portion of the second dye-containing recording layer are formed corresponding to the concave and convex portions of the substrate provided on the side opposite to the side where light is incident. Is preferable (claim 2).
Further, it is preferable that the first dye-containing recording layer has a thick film portion and a thin film portion, and light is incident on the thick film portion to record or reproduce information (claim 3).
[0015]
Further, the present invention is preferably applied to an optical recording medium in which the thick film portion and the thin film portion of the first dye-containing recording layer are formed corresponding to the concave and convex portions of the substrate provided on the side where light is incident ( Claim 4).
Further, the optical recording medium of the present invention has a first information in which at least a first dye-containing recording layer containing a first dye and a translucent reflective layer are sequentially laminated on a first substrate having a guide groove. A recording medium, and a second information recording body in which at least a reflective layer and a second dye-containing recording layer containing a second dye are sequentially laminated on a second substrate having a guide groove; The information recording body and the second information recording body are bonded together with an optically transparent adhesive layer facing the opposite side of the substrate, and the information recording or the information recording is performed by irradiating light from the first substrate side. An optical recording medium for performing reproduction, wherein the second dye-containing recording layer has a thick film portion and a thin film portion, and light is incident on the thin film portion to record or reproduce information. (Claim 5).
[0016]
In particular, it is preferable that the first dye-containing recording layer has a thick film portion and a thin film portion, and light is incident on the thick film portion to record or reproduce information (claim 6).
The optical recording medium of the present invention is an optical recording medium having a plurality of dye-containing recording layers for recording or reproducing information by irradiating light from one side, wherein a dye positioned farther from the light incident side. It is characterized in that the containing recording layer has a thick film portion and a thin film portion, and is configured to record or reproduce information by making light incident on the thin film portion.
[0017]
The method for manufacturing an optical recording medium according to the present invention is a method for manufacturing an optical recording medium for manufacturing an optical recording medium according to any one of claims 5 to 7, wherein the optical recording medium is formed on a second substrate using a negative stamper. The method further comprises the step of forming a guide groove (claim 8).
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an optical recording medium (recordable optical recording medium) and a recording / reproducing method of the optical recording medium according to an embodiment of the present invention will be described with reference to FIGS.
The optical recording medium according to the present embodiment is a single-sided incident type optical recording medium that has a plurality of recording layers and can record or reproduce information on each recording layer by irradiating a laser beam from one side. is there.
[0019]
In the present embodiment, for example, a dual-layer single-sided incidence DVD-R (single-sided dual-layer DVD-R, dual-layered single-sided DVD-R having two recording layers) is used as the bonded single-sided incidence type optical recording medium (single-sided incidence DVD-R). A single-sided dual-layer DVD recordable disc) will be described as an example.
(1) Structure of optical recording medium
FIG. 1 is a schematic sectional view showing an optical recording medium (optical disc) according to the present embodiment.
[0020]
As shown in FIG. 1, the optical recording medium according to the present embodiment has a first recording layer containing a dye on a transparent (light transmitting) first substrate (first light transmitting substrate) 21 in the form of a disk. (First dye-containing recording layer) 22, translucent reflective layer (hereinafter referred to as translucent reflective layer) 23, transparent adhesive layer (intermediate layer) 24, buffer layer 28, second recording layer containing dye (second dye) (Containing recording layer) 25, a reflective layer 26, and a disk-shaped second substrate 27 in this order. The light beam is irradiated from the first substrate 21 side, and recording or reproduction is performed.
[0021]
That is, the present optical recording medium has a first dye-containing recording layer 22 containing a first dye and a translucent reflective layer 13 sequentially laminated on a first substrate 21 having a guide groove. An information recording body and a second information recording body in which at least a reflective layer 26 and a second dye-containing recording layer 25 containing a second dye are sequentially laminated on a second substrate 27 having a guide groove are provided. The first information recording body and the second information recording body are attached to each other with the surface opposite to the substrate facing each other via an optically transparent adhesive layer.
[0022]
In the present embodiment, being transparent (having optical transparency) means being transparent (having optical transparency) with respect to a light beam used for recording or reproduction of an optical recording medium. Further, the transparent (light-transmitting) layer also includes a layer that slightly absorbs a light beam used for recording or reproduction. For example, if the light beam used for recording or reproduction has a transmittance of 50% or more (preferably 60% or more), it is assumed that the light beam is substantially light-transmissive (transparent).
[0023]
Next, each layer will be described.
(A) First substrate 21
The first substrate 21 is desirably excellent in optical characteristics such as being transparent and having a small birefringence. The refractive index of the first substrate 21 (refractive index with respect to the wavelength of the recording light or the reproduction light) is usually 1.40 or more, and preferably 1.45 or more. However, it is usually 1.70 or less, preferably 1.65 or less. Furthermore, it is desirable that the moldability is excellent, such as easy injection molding. Furthermore, low hygroscopicity is desirable because warpage and the like can be reduced.
[0024]
Further, it is desirable that the optical recording medium has a shape stability so as to have a certain rigidity. However, as long as the second substrate 27 has sufficient shape stability, the first substrate 21 may not have high shape stability.
Examples of such a material include resins made of acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin (especially amorphous polyolefin), polyester resin, polystyrene resin, epoxy resin, and the like, and those made of glass. Can be used. The first substrate 21 may be composed of a plurality of layers. For example, a substrate in which a resin layer composed of a radiation-curable resin such as a photocurable resin is provided on a substrate such as glass or resin may be used.
[0025]
In addition, polycarbonate is preferable in terms of high productivity such as optical characteristics and moldability, cost, low moisture absorption, shape stability, and the like. Amorphous polyolefin is preferred from the viewpoints of chemical resistance, low hygroscopicity and the like. Further, a glass substrate is preferable in terms of high-speed response and the like.
The first substrate 21 is preferably thinner, and usually has a thickness of preferably 2 mm or less, more preferably 1 mm or less. This is because the smaller the distance between the objective lens and the recording layer and the thinner the substrate, the smaller the coma aberration tends to be and the higher the recording density. However, in order to obtain sufficient optical properties, hygroscopicity, moldability, and shape stability, a certain thickness is required, and it is usually preferably 10 μm or more, more preferably 30 μm or more.
[0026]
In the present optical recording medium, it is desirable to appropriately adjust the distance between the objective lens and the two recording layers in order to perform good recording or reproduction on both the first recording layer 22 and the second recording layer 25. For example, it is preferable to set the focal point of the objective lens at a substantially intermediate point between the two recording layers, since both the recording layers can be easily accessed.
More specifically, in the DVD-ROM and DVD-R systems, the distance between the objective lens and the recording layer is adjusted to be optimum when the substrate thickness is 0.6 mm.
[0027]
Therefore, in the case of DVD-ROM compatibility in this layer configuration, the thickness of the first substrate 21 is a thickness obtained by subtracting half the thickness of the transparent adhesive layer 24 as an intermediate layer from 0.6 mm. Most preferably. At this time, the approximate middle point between the two recording layers is about 0.6 mm, and focus servo can be easily applied to both the recording layers.
When there is another layer such as a buffer layer or a protective layer between the second recording layer 25 and the translucent reflective layer 23, the thickness of these layers and the thickness of the transparent adhesive layer 24 is set to 0.6 mm. Most preferably, the thickness is reduced by a factor of one.
[0028]
A groove (guide groove) 31 used to guide recording / reproducing light (recording / reproducing beam; for example, laser light) at the time of recording or reproducing information is provided in the first substrate 21 in a spiral or concentric manner. Can be When the groove 31 is provided in the first substrate 21 as described above, irregularities are formed on the surface of the first substrate 21, and the concave portion (groove) is called a groove, and the convex portion is called a land. Then, information is recorded or reproduced on the first recording layer 22 using these grooves and / or lands as recording tracks. Note that the groove 31 on the first substrate 21 becomes a convex portion in the light incident direction.
[0029]
For example, in the case of a so-called DVD-R disc in which recording or reproduction is performed 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 first recording layer 22 is usually formed of a first substrate. Since the film is formed by coating on the first substrate 21, the thickness of the groove (concave portion) of the first substrate 21 is increased. Since the thicker film is more suitable for recording or reproduction, the groove is preferably used as a recording track.
[0030]
Here, the depth of the groove 31 provided on the first substrate 21 (groove depth; the height of the convex portion of the first dye-containing recording layer) is 1/10 × λ or more, where λ is the recording / reproducing wavelength. Is preferred. More preferably, it is １ ／ × λ or more. More preferably, it is set to １ ／ × λ or more. For example, if the wavelength of the recording / reproducing light (recording / reproducing wavelength) is λ = 650 nm, it is preferable that the depth of the groove 31 of the first substrate 21 be 65 nm or more. More preferably, the thickness is 81 nm or more. More preferably, the thickness is 108 nm or more.
[0031]
However, it is preferable that the depth of the groove 31 of the first substrate 21 be equal to or less than ／ × λ. It is more preferably 2/5 × λ or less, and further preferably 2/6 × λ or less. For example, if the recording / reproducing wavelength is λ = 650 nm, it is preferable that the depth of the groove 31 of the first substrate 21 be 325 nm or less. It is more preferably at most 260 nm, and still more preferably at most 217 nm.
[0032]
The width (groove width, G width; width of the convex portion of the first dye-containing recording layer; half width) of the groove 31 of the first substrate 21 is 1/10 × T or more, where T is the track pitch. Is preferred. It is more preferably at least 2/10 × T, further preferably at least 3/10 × T. For example, when the track pitch is 740 nm, it is preferable that the width of the groove 31 of the first substrate 21 be 74 nm or more. It is more preferably at least 148 nm, and still more preferably at least 222 nm.
[0033]
However, the width of the groove 31 of the first substrate 21 is preferably set to 9/10 × T or less. It is more preferably 8/10 × T or less, and still more preferably 7/10 × T or less. For example, when the track pitch is 740 nm, the width of the groove 31 of the first substrate 21 is preferably 666 nm or less. It is more preferably at most 592 nm, further preferably at most 518 nm.
[0034]
For example, in the case of groove recording, the groove 31 of the first substrate 21 is provided with a wobble by slightly meandering in a radial direction at a predetermined amplitude and a predetermined frequency. In addition, isolated pits (address pits) are formed on lands between the grooves 31 of the first substrate 21 according to a certain rule (this is called land pre-pit, LPP; Land Pre-Pit), and the address is formed by the land pre-pit. Information may be recorded in advance. In addition, it may have a concave and convex pit (pre-pit) if necessary.
[0035]
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.
(B) First recording layer 22
The first recording layer 22 generally has the same sensitivity as a recording layer used for a single-sided recording medium (eg, CD-R, DVD-R, DVD + R) or the like.
[0036]
In order to realize good recording / reproducing characteristics, it is desirable to use a dye having a low heat generation and a high refractive index.
Here, the refractive index (refractive index with respect to the wavelength of recording light or reproduction light) of the dye used for the first recording layer 22 is usually 1.00 or more, and preferably 1.50 or more. However, it is usually 3.00 or less.
[0037]
The extinction coefficient (extinction coefficient with respect to the wavelength of recording light or reproduction light) of the dye used for the first recording layer 22 is usually 0.50 or less, and preferably 0.30 or less. If the extinction coefficient is too large, the absorption by the dye recording layer becomes too large, and the reflectance becomes low. However, in order to perform recording, it is preferable that there is some absorption, and although there is no particular lower limit, it is usually 0.001 or more.
[0038]
Further, in the combination of the first recording layer 22 and the translucent reflection layer 23, it is desirable that the reflection, transmission, and absorption of light be in appropriate ranges. The recording sensitivity can be increased and the thermal interference during recording can be reduced.
Such organic dye materials include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, Examples include azurenium dyes, metal-containing azo dyes, and metal-containing indoaniline dyes.
[0039]
Among the various organic dyes described above, metal-containing azo dyes are preferable because they have excellent recording sensitivity and excellent durability and light resistance. In particular, the following general formula (I) or (II)
[0040]
Embedded image

[0041]
(Ring A ¹ And A ² Are each independently a nitrogen-containing aromatic heterocyclic ring which may have a substituent, and a ring B ¹ And B ² Are each independently an aromatic ring which may have a substituent. X is an alkyl group having 1 to 6 carbon atoms and substituted by at least two fluorine atoms. ) Is preferred.
The organic dye used in the recording layer of the present optical recording medium has a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 to 900 nm, and is preferably a dye compound suitable for recording with a blue to near microwave laser. . A near-infrared laser (typically 780 nm or 830 nm or the like) having a wavelength of about 770 to 830 nm used for a normal CD-R or a red laser having a wavelength of about 620 to 690 nm (typically used for a DVD-R) 635 nm, 650 nm, 680 nm, etc.), or a dye suitable for recording with a so-called blue laser having a wavelength of 410 nm or 515 nm is more preferable.
[0042]
One type of dye may be used, or two or more types of the same type or different types may be mixed and used. Further, a dye suitable for recording at each of the above-mentioned plurality of wavelengths may be used in combination with the recording light, so that an optical recording medium corresponding to recording with laser light in a plurality of wavelength ranges can be obtained.
The first recording layer 22 is formed of a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-) as a singlet oxygen quencher in order to improve the stability and light resistance of the recording layer. And a recording sensitivity improver such as a metal compound for improving the recording sensitivity. 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 an atom, an ion, a cluster, or the like.For example, an ethylenediamine-based complex, an azomethine-based complex, a phenylhydroxyamine-based complex, a phenanthroline-based complex, Organometallic compounds such as dihydroxyazobenzene-based complexes, dioxime-based complexes, nitrosoaminophenol-based complexes, pyridyltriazine-based complexes, acetylacetonate-based complexes, metallocene-based complexes, and porphyrin-based complexes are exemplified. The metal atom is not particularly limited, but is preferably a transition metal.
[0043]
Further, a binder, a leveling agent, an antifoaming agent and the like can be used in combination in the first recording layer 22 of the present optical recording medium, if necessary. Preferred binders include polyvinyl alcohol, polyvinylpyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.
[0044]
The thickness of the first recording layer 22 is not particularly limited because a suitable thickness varies depending on a recording method or the like, but is usually preferably 5 nm or more, more preferably 10 nm or more in order to obtain a sufficient degree of modulation. And particularly preferably 20 nm or more. However, in the present optical recording medium, the thickness is usually not more than 3 μm, preferably not more than 1 μm, more preferably not more than 200 nm because it is necessary that the thickness is not too thick in order to transmit light appropriately. The film thickness of the first recording layer 22 usually differs between the groove and the land, but in the present optical recording medium, the film thickness of the first recording layer 22 refers to the film thickness in the groove of the substrate.
[0045]
Examples of the method for forming the first recording layer 22 include thin film forming methods generally used such as a vacuum evaporation method, a sputtering method, a doctor blade method, a casting method, a spin coating method, and an immersion method. From the viewpoint, the spin coating method is preferred. From the viewpoint that a recording layer having a uniform thickness can be obtained, the vacuum deposition method is more preferable than the coating method.
[0046]
In the case of film formation by spin coating, the number of rotations is preferably 10 to 15000 rpm, and after spin coating, treatment such as heating or exposure to solvent vapor may be performed.
A coating solvent for forming the first recording layer 22 by a coating method such as a doctor blade method, a casting method, a spin coating method, and a dipping method is not particularly limited as long as it is a solvent that does not attack the substrate. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolve solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane A cyclic hydrocarbon solvent such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; a perfluoroalkyl alcohol such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Solvents such as hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate and methyl 2-hydroxyisobutyrate.
[0047]
In the case of the vacuum vapor deposition method, for example, an organic dye and, if necessary, recording layer components such as various additives are put into a crucible placed in a vacuum vessel, and the inside of the vacuum vessel is placed in an appropriate vacuum pump for 10 minutes. ^-2 -10 ^-5 After evacuation to about Pa, the crucible is heated to evaporate the recording layer components, and the first recording layer 22 is formed by vapor deposition on a substrate placed facing the crucible.
(C) Translucent reflective layer 23
The translucent reflection layer 23 is a reflection layer having a certain light transmittance. In other words, it is a reflective layer that absorbs recording / reproducing light little, has a light transmittance of 40% or more, and has an appropriate light reflectivity (generally, 30% or more). For example, an appropriate transmittance can be provided by thinly providing a metal having high reflectance. Also, it is desirable to have some corrosion resistance. Further, it is desirable that the first recording layer 22 has a blocking property so that the upper layer (the transparent adhesive layer 24 in this case) of the translucent reflection layer 23 does not affect the first recording layer 22.
[0048]
In order to ensure high transmittance, the thickness of the translucent reflective layer 23 is usually preferably 50 nm or less. More preferably, it is 30 nm or less. More preferably, it is 25 nm or less. However, since the first recording layer 22 is not affected by the upper layer of the translucent reflection layer 23, a certain thickness is required, and is usually 3 nm or more. More preferably, the thickness is 5 nm or more.
[0049]
As a material of the translucent reflection layer 23, one 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 It is possible to use a metal alone or as an alloy. Among them, Au, Al, and Ag have high reflectivity and are suitable as the material of the translucent reflective layer 23. In addition to these as main components, other components may be included.
[0050]
Among them, those containing Ag as a main component are particularly preferable because of their low cost and high reflectivity. Here, the main component means one having a content of 50% or more.
The translucent reflective layer 23 has a small thickness, and if the crystal grains of the film are large, it causes reproduction noise. Therefore, it is preferable to use a material having small crystal grains. Since pure silver tends to have large crystal grains, Ag is preferably used as an alloy.
[0051]
Above all, 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 metal. When containing two or more of Ti, Zn, Cu, Pd, Au and rare earth metals, each may be 0.1 to 15 atomic%, but the total thereof is preferably 0.1 to 15 atomic%. .
[0052]
A particularly preferred alloy composition is one containing Ag as a main component, containing at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au in an amount of 0.1 to 15 atomic%, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Among rare earth metals, neodymium is particularly preferred. Specifically, it is AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, or the like.
[0053]
As the translucent reflection layer 23, a layer made of Au alone has small crystal grains and is excellent in corrosion resistance and is suitable. However, they are more expensive than Ag alloys.
Further, a layer made of Si can be used as the translucent reflection layer 23.
It is also possible to form a multilayer film by alternately stacking low-refractive-index thin films and high-refractive-index thin films with a material other than a metal and use it as a reflective layer.
[0054]
Examples of a method for forming the translucent reflective layer 23 include a sputtering method, an ion plating method, a chemical vapor deposition method, and a vacuum vapor deposition method. In addition, a known inorganic or organic intermediate layer or adhesive layer is provided between the first substrate 21 and the translucent reflective layer 23, for example, to improve the reflectance, the recording characteristics, and the adhesion. It may be provided. For example, by stacking an intermediate layer (or an adhesive layer), a first recording layer 22, an intermediate layer (or an adhesive layer), and a translucent reflective layer 23 on the first substrate 21 in this order, the first substrate 21 and the first An intermediate layer (or an adhesive layer) may be provided between the recording layer 22 and an intermediate layer (or an adhesive layer) may be provided between the first recording layer 22 and the translucent reflective layer 23.
(D) Transparent adhesive layer 24
The transparent adhesive layer 24 needs to be transparent, and preferably has a high adhesive strength and a small shrinkage ratio during curing and bonding because the shape stability of the medium is high.
[0055]
The refractive index (refractive index with respect to the wavelength of recording light or reproduction light) of the transparent adhesive layer 24 is usually 1.40 or more, and preferably 1.45 or more. However, it is usually 1.70 or less, preferably 1.65 or less.
Further, it is desirable that the transparent adhesive layer 24 be made of a material that does not damage the second recording layer 25. However, since the transparent adhesive layer 24 is usually made of resin, it is easily compatible with the second recording layer 25, and it is desirable to provide a buffer layer 28 described later between both layers to prevent this and suppress damage.
[0056]
Further, it is desirable that the transparent adhesive layer 24 be made of a material that does not damage the translucent reflective layer 23. However, a known inorganic or organic protective layer may be provided between both layers in order to suppress damage.
In the present optical recording medium, the thickness of the transparent adhesive layer 24 is preferably controlled accurately. The thickness of the transparent adhesive layer 24 is usually preferably 5 μm or more. In order to separately apply focus servo to the two recording layers, there must be a certain distance between the two recording layers. Although it depends on the focus servo mechanism, it usually needs to be 5 μm or more, preferably 10 μm or more.
[0057]
In general, the higher the numerical aperture of the objective lens, the smaller the distance tends to be. However, if the thickness is too large, it takes time to adjust the focus servo to the two recording layers, and the moving distance of the objective lens is undesirably long. In addition, since there is a problem such as a long time for curing and a decrease in productivity, usually 100 μm or less is preferable.
Examples of the material of the transparent adhesive layer 24 include a thermoplastic resin, a thermosetting resin, an electron beam-curable resin, and an ultraviolet-curable resin (including a delay-curable resin).
[0058]
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 coating solution, and drying (heating). The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, applying the coating solution, and irradiating with ultraviolet light to cure the coating solution. There are various types of ultraviolet curable resins, and any of them can be used as long as they are transparent. These materials may be used alone or as a mixture, or may be used as a multilayer film instead of a single layer.
[0059]
As a coating method, a coating method such as a spin coating method or a casting method is used as in the case of the recording layer. Among them, the spin coating method is preferable. Alternatively, a resin having a high viscosity can be applied and formed by screen printing or the like. It is preferable to use a UV-curable resin that is liquid at a productivity of 20 to 40 ° C. because it can be applied without using a solvent. Further, it is preferable to adjust the viscosity to be 20 to 1000 mPa · s.
[0060]
Note that an adhesive layer can also be formed by using a pressure-sensitive double-sided tape and pressing the tape between the laminated structures.
Now, as the ultraviolet curable adhesive, there are a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, and both can be used.
All known compositions can be used as the radical type ultraviolet curable adhesive, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, a monofunctional (meth) acrylate or a polyfunctional (meth) acrylate can be used as a polymerizable monomer component. Each of 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.
[0061]
Examples of the polymerizable monomer that can be used in the present optical recording medium include the following. Examples of the monofunctional (meth) acrylate include, as a substituent, 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, nonylphenoxyethyltetrahydrofurfuryl, caprolactone-modified tetrahydrofurfuryl, isobornyl , Dicyclopentenyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like, and a (meth) acrylate having a group.
[0062]
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. , Neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, di (meth) glycol such as polypropylene glycol Acrylate, di (meth) acrylate of tris (2-hydroxyethyl) isocyanurate, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol Di (meth) acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A, and triol obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole 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) Acrylates, poly (meth) acrylates of dipentaerythritol, ethylene oxide-modified phosphoric acid (meth) acrylate, ethylene oxide-modified alkylated phosphoric acid (meth) acrylate, and the like. It is.
[0063]
Examples of those which can be used together with the polymerizable monomer include polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, and urethane (meth) acrylate as the polymerizable oligomer.
Further, as the photopolymerization initiator used in the present optical recording medium, any known one that can cure an ultraviolet curable compound represented by a polymerizable oligomer and / or a 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 optical recording medium.
[0064]
Such examples 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 and the like are preferably used. 1-hydroxycyclohexylphenyl 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 and the like may be used in combination, and benzophenone, 4-phenylbenzophenone, and isophthalphenone which are hydrogen abstraction type photopolymerization initiators , 4-benzoyl-4'-methyl-diphenyl sulfide and the like can also be used in combination.
[0065]
Examples of sensitizers for the photopolymerization initiator include, for example, trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzyl Amines such as amine and 4,4'-bis (diethylamino) benzophenone which do not cause an addition reaction with the above-mentioned polymerizable component can be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that have excellent solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.
[0066]
In addition, all known compositions can be used as the cationic ultraviolet curable adhesive, 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 the 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 hexafluoroa Chimoneto, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrakis (pentafluorophenyl) borate, and the like.
[0067]
The epoxy resin may be any of various types such as bisphenol A-epichlorhydrin 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.
[0068]
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. In order to more effectively use the wavelength in the near-ultraviolet region or the visible region of the wavelength range of the ultraviolet light source, a known photosensitizer can be used in combination. In this case, examples of the photosensitizer include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, acetophenone and the like.
[0069]
In addition, the UV curable adhesive may further include, if necessary, other additives such as a thermal polymerization inhibitor, an antioxidant represented by a hindered phenol, a hindered amine, and a phosphite, a plasticizer, an epoxy silane, and a mercapto. A silane coupling agent typified by silane, (meth) acryl silane, or the like can be blended for the purpose of improving various characteristics. These are selected from those having excellent solubility in ultraviolet curable compounds and those which do not inhibit ultraviolet transmittance.
(E) Second recording layer 25
The second recording layer 25 generally has higher sensitivity than a recording layer used for a single-sided recording medium (eg, CD-R, DVD-R, DVD + R) or the like. In the present optical recording medium, since the power of the incident light beam is reduced due to the presence of the first recording layer 22 and the translucent reflective layer 23, the sensitivity needs to be particularly high in order to record at about half the power. There is.
[0070]
In order to realize good recording / reproducing characteristics, it is desirable to use a dye having a low heat generation and a high refractive index.
Here, the refractive index of the dye used for the second recording layer 25 (the refractive index with respect to the wavelength of recording light or reproduction light) is usually 1.00 or more, and preferably 1.50 or more. However, it is usually 3.00 or less.
[0071]
The extinction coefficient (extinction coefficient with respect to the wavelength of recording light or reproduction light) of the dye used for the second recording layer 25 is usually 0.50 or less, and preferably 0.30 or less. If the extinction coefficient is too large, the absorption by the dye recording layer becomes too large, and the reflectance becomes low. However, in order to perform recording, it is preferable that there is some absorption, and although there is no particular lower limit, it is usually 0.001 or more.
[0072]
Further, in the combination of the second recording layer 25 and the reflection layer 26, 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.
Since the material of the second recording layer 25, the film forming method, and the like are substantially the same as those of the first recording layer 22, only different points will be described.
[0073]
The thickness of the second recording layer 25 is not particularly limited because a suitable thickness varies depending on a recording method or the like, but is usually preferably 10 nm or more, more preferably 30 nm or more in order to obtain a sufficient degree of modulation. And particularly preferably 50 nm or more. However, the thickness is usually 3 μm or less, preferably 1 μm or less, and more preferably 200 nm or less, because it is necessary that the thickness be not too thick in order to obtain an appropriate reflectance. Here, the film thickness of the second recording layer 25 usually refers to the film thickness in the thick film portion.
[0074]
The materials used for the first recording layer 22 and the second recording layer 25 may be the same or different.
(F) Regarding the reflection layer 26
The reflection layer 26 needs to have high reflectance. Further, it is desirable to have high durability.
[0075]
In order to ensure a high reflectance, the thickness of the reflective layer 26 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 shorten the production tact time and reduce the cost, it is preferable that the thickness be somewhat thin, and usually 400 nm or less. More preferably, the thickness is 300 nm or less.
[0076]
As the material of the reflection layer 26, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal of Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta and Pd is used alone or in an alloy. It is possible. Among them, Au, Al, and Ag have high reflectance and are suitable as the material of the reflection layer 26. In addition to these as main components, the following 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, and Pb. , Po, Sn, Bi and rare earth metals.
[0077]
Above all, those containing Ag as a main component are particularly preferable in that they are inexpensive, easily produce high reflectivity, and when a print accepting 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 to ensure high durability (high corrosion resistance) of the reflective layer 26, Ag is preferably used as an alloy rather than pure silver.
[0078]
Above all, 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 metal. When containing two or more of Ti, Zn, Cu, Pd, Au and rare earth metals, each may be 0.1 to 15 atomic%, but the total thereof is preferably 0.1 to 15 atomic%. .
[0079]
A particularly preferred alloy composition is one containing Ag as a main component, containing at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au in an amount of 0.1 to 15 atomic%, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Among rare earth metals, neodymium is particularly preferred. Specifically, it is AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, or the like.
[0080]
As the reflective layer 26, a layer composed of only Au is preferable because it has high durability (high corrosion resistance). However, they are more expensive than Ag alloys.
It is also possible to form a multilayer film by alternately stacking low-refractive-index thin films and high-refractive-index thin films with a material other than a metal, and use it as the reflective layer 26.
Examples of the method for forming the reflective layer 26 include a sputtering method, an ion plating method, a chemical vapor deposition method, and a vacuum vapor deposition method. Further, a known inorganic or organic intermediate layer or adhesive layer may be provided above and below the reflective layer 26, for example, to improve the reflectance, the recording characteristics, and the adhesion.
(G) Second substrate 27
The second substrate 27 desirably has shape stability so that the optical recording medium has some rigidity. That is, it is preferable that the mechanical stability is high and the rigidity is high.
[0081]
Examples of such a material include resins made of acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin (especially amorphous polyolefin), polyester resin, polystyrene resin, epoxy resin, and the like, and those made of glass. Can be used.
Alternatively, the second substrate 27 may be composed of a plurality of layers. For example, a substrate in which a resin layer made of a radiation curable resin such as a photocurable resin is provided on a substrate such as glass or resin may be used. Can be used as a substrate.
[0082]
As described above, when the first substrate 21 does not have sufficient shape stability, the second substrate 27 needs to have particularly high shape stability. In this respect, it is desirable that the hygroscopicity is small.
The second substrate 27 need not be transparent, but when it is transparent, the refractive index of the second substrate 27 (refractive index with respect to the wavelength of recording light or reproduction light) is usually 1.40 or more, and is preferably Is 1.45 or more. However, it is usually 1.70 or less, preferably 1.65 or less.
[0083]
As such a material, the same material as the material that can be used for the first substrate 21 can be used. For example, for example, an Al alloy substrate such as an Al—Mg alloy containing Al as a main component, or a material containing Mg as a main component, for example, A Mg alloy substrate such as an Mg-Zn alloy, a substrate made of any of silicon, titanium, and ceramics, a substrate obtained by combining them, and the like can be used.
[0084]
The above-mentioned resins are preferred from the viewpoint of high productivity such as moldability, cost, low hygroscopicity, shape stability and the like, and particularly preferred is polycarbonate. Amorphous polyolefin is preferred from the viewpoints of chemical resistance, low hygroscopicity and the like. Further, a glass substrate is preferable in terms of high-speed response and the like.
In order to provide the optical recording medium with sufficient rigidity, the second substrate 27 is preferably thick to some extent, and the thickness is preferably 0.3 mm or more. However, a thinner one is advantageous for making the recording / reproducing apparatus thinner, and is preferably 3 mm or less. It is more preferably 1.5 mm or less.
[0085]
In an example of a preferred combination of the first substrate 21 and the second substrate 27, the first substrate 21 and the second substrate 27 are made of the same material and have the same thickness. Since the rigidity is the same and the balance is maintained, it is preferable that the medium does not easily deform as a medium against environmental changes. In this case, it is preferable that the degree and direction of the deformation when the environment changes are the same for both substrates.
An example of another preferable combination is that the first substrate 21 is as thin as about 0.1 mm and the second substrate 27 is as thick as about 1.1 mm. This is preferable because the objective lens can easily approach the recording layer and increase the recording density. At this time, the first substrate 21 may be in a sheet shape.
[0086]
A groove (guide groove) 32 used for guiding recording / reproducing light (recording / reproducing beam; for example, laser light) at the time of recording or reproducing information is provided in the second substrate 27 in a spiral or concentric manner. Can be When the grooves 32 are provided in the second substrate 27 in this way, irregularities are formed on the surface of the second substrate 27, and the concave portions (grooves) are called grooves, and the convex portions are called lands. Note that the groove 32 on the second substrate 27 becomes a concave portion in the light incident direction.
[0087]
Here, since the second recording layer 25 is applied and formed on the reflective layer 26 formed on the second substrate 27, the thickness of the groove (concave portion) of the second substrate 27 increases (this portion is thickened). The film thickness is reduced at the land (convex portion) of the second substrate 27 (this portion is called a thin film portion).
In the present embodiment, when performing land recording, a wobble is provided on the land by slightly meandering the groove wall of the groove 32 of the second substrate 27 in a radial direction at a predetermined amplitude and a predetermined frequency. Alternatively, address information and other information may be recorded in advance by providing pits in the groove.
[0088]
From the viewpoint of cost, the second substrate 27 having such irregularities is preferably manufactured by injection molding using a resin 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.
(I) About buffer layer 28
Here, a buffer layer 28 as an intermediate layer is provided between the transparent adhesive layer 24 and the second recording layer 25.
[0089]
The buffer layer 28 prevents mixing of the two layers and prevents compatibility. The buffer layer 28 may also have another function other than preventing the mixing phenomenon. Further, another intermediate layer may be interposed as necessary.
The material of the buffer layer 28 is required to be incompatible with the second recording layer 25 and the transparent adhesive layer 24 and to have a certain degree of light transmittance, but known inorganic and organic substances can be used. In terms of characteristics, an inorganic substance is preferably used. For example, (1) metal or semiconductor, (2) oxide, nitride, sulfide, oxysulfide, fluoride or carbide of metal or semiconductor, or (3) amorphous carbon is used. Above all, a layer made of a substantially transparent dielectric or a very thin metal layer (including an alloy) is preferable.
[0090]
Specifically, silicon oxides, particularly silicon dioxide, oxides such as zinc oxide, cerium oxide and yttrium oxide; sulfides such as zinc sulfide and yttrium sulfide; nitrides such as silicon nitride; silicon carbide; (Oxysulfide); and alloys described below are preferred. Further, a mixture of silicon oxide and zinc sulfide in a ratio of about 30:70 to 90:10 (weight ratio) is also suitable. A mixture of sulfur, yttrium dioxide and zinc oxide (Y ₂ O ₂ (S-ZnO) is also suitable.
[0091]
As the metal or alloy, silver or a material containing silver as a main component and further containing 0.1 to 15 atomic% of at least one element selected from the group consisting of titanium, zinc, copper, palladium, and gold is preferable. is there. Further, those containing silver as a main component and containing at least one kind of rare earth element in an amount of 0.1 to 15 atomic% are also suitable. As the rare earth, neodymium, praseodymium, cerium and the like are suitable.
[0092]
In addition, a resin layer may be used as long as it does not dissolve the dye in the recording layer during the preparation of the buffer layer. In particular, a polymer film that can be formed by vacuum evaporation or CVD is useful.
The thickness of the buffer layer 28 is preferably 2 nm or more, more preferably 5 nm or more. If the thickness of the buffer layer 28 is excessively thin, the prevention of the above-mentioned mixing phenomenon may be insufficient. However, it is preferably 2000 nm or less, more preferably 500 nm or less. If the buffer layer 28 is excessively thick, not only is it unnecessary to prevent miscibility, but also the light transmittance may decrease. In the case of a layer made of an inorganic substance, it takes a long time to form the film, which may lower the productivity or increase the film stress. In particular, in the case of metal, the thickness is preferably about 20 nm or less in order to excessively reduce the light transmittance.
[0093]
In addition, a buffer layer as an intermediate layer may be provided between the translucent reflective layer 23 and the transparent adhesive layer 24.
(J) About other layers
In the laminated structure, any other layer may be interposed as necessary. Alternatively, any other layer may be provided on the outermost surface of the medium.
[0094]
Specifically, 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 protects 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. In addition, as the inorganic substance, silicon oxide, silicon nitride, MgF ₂ , SnO ₂ And the like.
[0095]
A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in a suitable 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 an appropriate solvent, applying the coating solution, and irradiating with UV light to cure the resin. As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used singly or as a mixture, or may be used not only as a single layer but also as a multilayer film.
[0096]
As a method of forming the protective layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used as in the case of the recording layer. Among them, the spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 to 100 μm, but is preferably 1 to 50 μm in the present optical recording medium.
[0097]
Further, the optical recording medium may be printed on a surface other than the incident surface of the recording light or the reproduction light, if necessary, with various printers such as ink jet and thermal transfer, or various writing tools. A layer may be provided.
Alternatively, a recording layer may be provided in addition to the main layer structure, and three or more recording layers may be provided. In addition, two optical recording media having the present layer configuration and the first substrate 21 facing outward can be bonded together to form a larger capacity medium having four recording layers.
[0098]
As described above, in the single-sided incident type optical recording medium having the two dye-containing recording layers 22 and 25, the first dye-containing recording layer 22 closer to the light incident side (one side) and the second dye-side recording layer 22 farther to the light incident side (one side). And a dye-containing recording layer 25. For this reason, recording or reproduction of information on the second dye-containing recording layer 25 located on the side farther from the light incident side is performed by irradiating the light through the first dye-containing recording layer 22. Become.
[0099]
In such a single-sided incident type optical recording medium, good recording / reproducing characteristics can be obtained by providing a recording track in the concave portion (thick film portion 22A) of the first dye-containing recording layer 22, whereas the second dye-containing recording medium can be obtained. If a recording track is provided in the concave portion (thick film portion 25A) of the layer 25, good recording / reproducing characteristics (eg, reflectance, polarity, maximum signal amplitude, etc.) may not be obtained.
[0100]
Therefore, in the optical recording medium according to the present embodiment, the first dye-containing recording layer 22 having the thick film portion 22A and the thin film portion 22B and the second dye-containing recording layer 25 having the thick film portion 25A and the thin film portion 25B are formed. In the optical recording medium provided, a recording track is provided in the thick film portion 22A of the first dye-containing recording layer 22 on the side close to the light incident side (one side) in order to obtain good recording / reproducing characteristics. In the second dye-containing recording layer 25 farther from the light incident side, a recording track is provided in the thin film portion 25B.
[0101]
As described above, in the second recording layer 25, when recording is performed on the thin film portion 25B, it is estimated that the recording and reproduction characteristics can be improved due to the following effects.
That is, in order to perform tracking on a recording track and perform good recording or reproduction, the phase difference (optical path length difference) between the concave portion (non-track portion) and the convex portion (track portion) when irradiated with a light beam is important. It becomes.
[0102]
In the first recording layer 22, the difference between the light reflected from the interface between the first recording layer 22 and the translucent reflective layer 23 in the concave portion and the light reflected from the interface in the convex portion corresponds to the optical path length difference. This optical path length difference mainly depends on the distance between the light incident side surfaces of the concave portion and the convex portion of the first recording layer 22 (the surface of the thin film portion 22B of the first recording layer 22 on the first substrate 21 side and the thick film portion). The distance between the portion 22A and the surface of the first substrate 21 side) d1 (see FIG. 1), the difference in film thickness between the concave and convex portions of the first recording layer 22, the complex refractive index of the first recording layer 22, It is obtained from the complex refractive index of one substrate 21.
[0103]
On the other hand, in the second recording layer 25, the difference between the reflected light from the interface between the second recording layer 25 and the reflective layer 26 in the concave portion and the reflected light from the same interface in the convex portion corresponds to the optical path length difference. This difference in optical path length is mainly determined by the distance between the light incident side surfaces of the concave and convex portions of the second recording layer 25 [the surface of the thin film portion 25B of the second recording layer 25 on the side of the transparent adhesive layer (intermediate layer) 24]. And the distance between the thick film portion 25A and the surface on the side of the transparent adhesive layer 24] d2 (see FIG. 1), the difference in film thickness between the concave portion and the convex portion of the second recording layer 25, and the complex refraction of the second recording layer 25. And the complex refractive index of the transparent adhesive layer 24.
[0104]
In this case, d2 is necessarily different from d1. In other words, d2 is considerably smaller than d1 because of the unevenness of the surface portion in which the grooves are filled to some extent by applying the recording layer.
For this reason, the optical path length difference and, consequently, the phase difference behave considerably different from those of the first recording layer 22, and it is considered that recording on the thin film portion 25B in the second recording layer 25 has become preferable.
[0105]
By the way, in order to provide a recording track on the thin film portion 25B of the second recording layer 25, it is necessary to secure a thickness necessary for the thin film portion 25B of the second recording layer 25 to function as a recording layer. That is, it is preferable that the thickness (L film thickness) of the thin film portion 25B of the second recording layer 25 be equal to or more than a predetermined thickness (for example, 70 nm). For example, in the case where the second recording layer 25 is formed by spin-coating a solution containing a dye, the second recording layer is formed by changing the dye concentration as a recording layer application condition or changing the spin speed. The thickness of the film 25 can be set to a predetermined thickness or more.
[0106]
Here, the film thickness difference between the thick film portion 25A and the thin film portion 25B of the second recording layer 25 is 1/100 × λ / n, where λ is the recording / reproducing wavelength and n is the refractive index of the second recording layer 25. It is preferable to make the above. It is more preferably at least 2/100 × λ / n, and further preferably at least 3/100 × λ / n.
However, it is preferable that the thickness difference be 1/3 × λ / n or less. It is more preferably at most １ ／ × λ / n, further preferably at most １ ／ × λ / n.
[0107]
Specifically, assuming that the recording / reproducing wavelength is λ = 650 nm and the refractive index of the second recording layer 25 is n = 2.2, the thickness difference between the thick film portion 25A and the thin film portion 25B of the second recording layer 25 is , And preferably 3 nm or more. The thickness is more preferably 6 nm or more, and further preferably 9 nm or more. On the other hand, the difference in film thickness is preferably 98 nm or less. It is more preferably at most 74 nm, further preferably at most 59 nm.
[0108]
On the other hand, the film thickness difference between the thick film portion 22A and the thin film portion 22B of the first recording layer 22 is 1/30 × (λ / n) where λ is the recording / reproducing wavelength and n is the refractive index of the first recording layer 22. ) Or more. It is more preferably at least 2/30 × (λ / n), and still more preferably at least 3/30 × (λ / n).
However, it is preferable that the thickness difference be 4/4 × (λ / n) or less. It is more preferably at most 4/5 × (λ / n), further preferably at most 4/6 × (λ / n).
[0109]
Specifically, assuming that the recording / reproducing wavelength is λ = 650 nm and the refractive index of the first recording layer 22 is n = 2.2, the thickness difference between the thick film portion 22A and the thin film portion 22B of the first recording layer 22 is , And preferably 10 nm or more. It is more preferably at least 20 nm, and still more preferably at least 30 nm. On the other hand, the difference in thickness is preferably 295 nm or less. The thickness is more preferably 236 nm or less, and further preferably 197 nm or less.
[0110]
In the present embodiment, the thick film portion 22A and the thin film portion 22B of the first recording layer 22 are formed corresponding to the concave and convex portions of the first substrate 21 located on the light incident side, respectively. In other words, recording tracks are provided in the grooves (concave portions) of the first recording layer 22, that is, the convex portions (thick film portions 22A) protruding in the light incident direction.
Therefore, information is recorded or reproduced on the optical recording medium by irradiating (irradiating) light with a groove (concave portion) of the first substrate 21, that is, a convex portion (thick film portion 22A) of the first recording layer 22. Recording or reproduction of information is performed.
[0111]
On the other hand, in the present embodiment, the thick film portion 25A and the thin film portion 25B of the second recording layer 25 are formed respectively corresponding to the concave portion and the convex portion of the second substrate 27 located on the side opposite to the light incident side. Therefore, the recording tracks are provided on the lands (convex portions) of the second substrate 27, that is, the convex portions (thin film portions 25B) of the second recording layer 25 that protrude in the light incident direction.
[0112]
For this reason, information is recorded or reproduced on the optical recording medium by irradiating (irradiating) light with a land (convex portion) of the second substrate 27, that is, a convex portion (thin film portion 25B) of the second recording layer 25. Recording or reproduction of information is performed.
In the present embodiment, since the recording tracks are provided in the grooves of the first substrate 21 and the recording tracks are provided in the lands of the second substrate 27, the tracking polarity is set when recording or reproducing the information of each recording layer. You may need to change it.
[0113]
In the present embodiment, the recording tracks are provided on the lands of the second substrate 27 (land recording). However, the depth of the groove 32 of the second substrate 27 is adjusted to the depth of a general dye-based optical recording medium. If the depth is made shallower than the depth of the groove so that a reflectivity sufficient for recording or reproducing information on the second recording layer 25 is obtained, compatibility with a DVD-ROM can be easily obtained. In addition, when the depth of the groove of the second substrate 27 may be small, the moldability is improved, and the productivity of the second substrate 27 having the guide groove is also improved (mass productivity).
[0114]
Specifically, the depth of the groove 32 of the second substrate 27 may be set as follows.
First, it is preferable that the depth (groove depth) of the groove 32 of the second substrate 27 be 1/100 × λ or more, where λ is the recording / reproducing wavelength. It is more preferably at least 2/100 × λ, further preferably at least 3/100 × λ. This is because it is preferable to have a certain depth for good tracking.
[0115]
For example, if the recording / reproducing wavelength is λ = 650 nm, it is preferable that the depth of the groove 32 of the second substrate 27 be 7 nm or more. The thickness is more preferably 13 nm or more, and further preferably 20 nm or more.
However, it is preferable that the depth of the groove 32 of the second substrate 27 be 1/6 × λ or less. It is more preferably 1/8 × λ or less, and still more preferably 1/10 × λ or less. This is because it is desirable not to make the groove too deep in order to obtain a sufficient reflectance.
[0116]
For example, when the recording / reproducing wavelength is λ = 650 nm, the depth of the groove 32 of the second substrate 27 is preferably set to 108 nm or less. It is more preferably at most 81 nm, further preferably at most 65 nm.
The width (groove width, G width; half width) of the groove 32 of the second substrate 27 is preferably 1/10 × T or more, where T is the track pitch. It is more preferably at least 2/10 × T, further preferably at least 3/10 × T. This is because if the groove width is too narrow, tracking tends to be difficult.
[0117]
For example, when the track pitch is 740 nm, it is preferable that the width of the groove 32 of the second substrate 27 be 74 nm or more. It is more preferably at least 148 nm, and still more preferably at least 222 nm.
However, it is preferable that the width of the groove 32 of the second substrate 27 be 9/10 × T or less. It is more preferably 8/10 × T or less, and still more preferably 7/10 × T or less. This is because if the groove width is too wide, tracking tends to be difficult, and good recording tends to be difficult.
[0118]
For example, when the track pitch is 740 nm, it is preferable that the width of the groove 32 of the second substrate 27 be 666 nm or less. It is more preferably at most 592 nm, further preferably at most 518 nm.
As described above, in the present embodiment, the depth of the groove 32 of the second substrate 27 is set to be smaller than the depth of the groove of a general dye-based optical recording medium. It is preferable that the depth of the groove 32 be smaller than the depth of the groove 31 of the first substrate 21.
[0119]
Further, by making the depth of the groove 32 of the second substrate 27 smaller than the depth of the groove of a general optical recording medium, a reflectivity sufficient for recording or reproducing information on the second recording layer 25 can be obtained. Therefore, it is considered that both the thin film portion 25B and the thick film portion 25A of the second recording layer 25 may be used as recording tracks. That is, information can be recorded or reproduced by irradiating (irradiating) light to the lands (convex portions) of the second substrate 27, that is, the concave portions (thin film portions 25B) of the second recording layer 25. Recording or reproduction of information can also be performed by irradiating (irradiating) light to the groove (concave portion) of the two substrates 27, that is, the convex portion (thick film portion 25A) of the second recording layer 25.
[0120]
Usually, the depth of the groove 32 of the second substrate 27 is preferably 90% or less of the depth of the groove 31 of the first substrate 21, more preferably 80% or less, further preferably 70% or less. It is. However, it is usually at least 5% of the depth of the groove 31 of the first substrate 21, preferably at least 10%.
(2) Manufacturing method of optical recording medium
Next, a method of manufacturing the optical recording medium configured as described above will be described.
[0121]
First, a laminated structure (first information recording body) having a first recording layer 22 containing a dye and a translucent reflective layer 23 in this order on a transparent first substrate 21 is prepared. On the other hand, a laminated structure (second information recording body) having a reflective layer 26, a second recording layer 25 containing a dye, and a buffer layer 28 in this order on the second substrate 27 is formed. Then, the first information recording body and the second information recording body are bonded to each other with the recording layer facing inward via the transparent adhesive layer 24.
[0122]
Specifically, first, a transparent first substrate 21 having grooves, lands, and prepits formed on the surface with irregularities is formed by injection molding or a 2P method (a curable resin such as a photocurable resin using a resin stamper having irregularities). (A method of manufacturing by transferring and curing).
Next, after at least dissolving the organic dye in the solvent, the first recording layer 22 is formed by forming a film on the surface of the first substrate 21 having the unevenness by spin coating or the like.
[0123]
Further, a semitransparent reflective layer 23 is formed thereon by sputtering or vapor-depositing an Ag alloy or the like, thereby producing a first information recording medium.
Next, a second substrate 27 having grooves, lands, and pits formed on the surface with irregularities is formed by injection molding or 2P method. The reflective film 26 is formed on the surface of the second substrate 27 having the irregularities by sputtering and depositing an Ag alloy or the like.
[0124]
Further, after dissolving at least an organic dye in a solvent, the second recording layer 25 is formed by forming a film by spin coating or the like.
Next, the buffer layer 28 is formed by sputtering a dielectric or the like, thereby producing a second information recording body.
Then, after applying an adhesive such as an ultraviolet curable resin on the first information recording body, the second information recording body is placed, and the adhesive is spread over the entire surface by high-speed rotation, pressing, or the like. This is performed while adjusting the thickness of the adhesive layer to be within a predetermined range.
[0125]
Thereafter, ultraviolet light is irradiated from the first information recording medium side through the semi-transparent reflective layer 23, and an adhesive such as an ultraviolet curable resin is cured and adhered, whereby an optical recording medium is manufactured.
Note that ultraviolet light can be applied from the side of the medium. In any case, care must be taken to prevent the dye recording layer from being damaged by the ultraviolet rays. Alternatively, an adhesive layer can be formed by using a pressure-sensitive double-sided tape and pressing the tape between the first information recording body and the second information recording body while pressing the tape. Alternatively, the adhesive layer may be applied by using a delayed-curing adhesive, applying the adhesive on the first information recording body by screen printing or the like, irradiating with ultraviolet light, placing the second information recording body, and pressing. Can be formed. However, the delay hardening type adhesive is usually opaque in many cases.
[0126]
Next, a method for manufacturing the substrates 21 and 27 having guide grooves (irregularities) will be described. For example, in order to form irregularities (grooves) on these substrates 21 and 27, a first stamper 21 is manufactured by transferring irregularities to a resin material by injection molding using a metal stamper having desired irregularities. There is a method of manufacturing the second substrate 27 by transferring the unevenness to a resin material by injection molding using a metal stamper having the opposite unevenness.
[0127]
In particular, a recording track may be provided with synchronization information, address information, or the like, for example, by giving wobbles.
In the present embodiment, as described above, a recording track is provided in the thick film portion 22A of the first recording layer 22 and a recording track is provided in the thin film portion 25B of the second recording layer 25. The wobble is given to the convex portion of the two substrates 27.
[0128]
The procedure for giving a wobble to the concave portion of the first substrate 21 is as follows.
First, the glass substrate / photoresist is exposed while the beam is meandering, and developed to obtain an irregular master. In this irregular master, there is usually a wobble in a concave portion (groove portion).
Next, a stamper is manufactured by using the uneven master, and a first substrate 21 having unevenness (grooves, guide grooves) is manufactured by injection molding using the manufactured stamper. In this case, since there is a wobble in the convex portion of the stamper, the wobble is formed in the concave portion of the first substrate 21.
[0129]
However, in order to provide a wobble to the convex portion of the second substrate 27, it is necessary that the concave portion of the stamper has the wobble. For this reason, the wobble cannot be given to the convex portion of the second substrate 27 by the above-described method.
Therefore, first, a stamper is manufactured by the same method as the stamper used to form the irregularities (grooves, guide grooves) on the first substrate 21 described above. However, the shape of the unevenness (groove depth, groove width, meandering width, etc.) needs to be changed according to the unevenness to be formed on the second substrate 27.
[0130]
Next, the concavities and convexities are transferred from this stamper, and a negative stamper having reverse concavities and convexities is manufactured. In this case, since there is a wobble in the convex portion of the stamper, the wobble is formed in the concave portion of the negative stamper.
Next, a second substrate 27 having irregularities (grooves, guide grooves) is manufactured by injection molding using the negative stamper. In this case, since there is a wobble in the concave portion of the negative stamper, the wobble is formed in the convex portion of the second substrate 27.
(3) Recording / reproducing method of optical recording medium
Next, a recording / reproducing method for the optical recording medium according to the present embodiment will be described.
[0131]
Recording on the optical recording medium configured 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 21 side. In the portion irradiated with the laser light, thermal deformation of the recording layer such as decomposition, heat generation, and melting occurs due to absorption of laser light energy, and optical characteristics change.
On the other hand, the reproduction of the recorded information is performed by reading the difference in reflectance between a portion where the optical characteristics have changed and a portion where the optical characteristics have not changed, using a laser beam.
[0132]
Recording and reproduction are individually performed on the two recording layers as follows. The focus position of the focused laser can be distinguished between the first recording layer 22 and the second recording layer 25 by a focus error signal obtained by a knife edge method, an astigmatism method, a Foucault method, or the like. That is, when the objective lens that focuses the laser light is moved up and down, an S-shaped curve is obtained at a position corresponding to the first recording layer 22 and a position corresponding to the second recording layer 25, respectively. Depending on which S-shaped curve is used for focus servo, it is possible to select which of the first recording layer 22 and the second recording layer 25 to record and reproduce.
[0133]
In the present embodiment, when recording or reproducing information on the first recording layer 22, light is incident on a groove (concave portion) of the first substrate 21, that is, a convex portion (thick film portion 22 </ b> A) of the first recording layer 22. Then, recording or reproduction of information is performed. On the other hand, when recording or reproducing information on the second recording layer 25, light is made incident on the lands (convex portions) of the second substrate 27, that is, the convex portions (thin film portions 25B) of the second recording layer 25 ( Recording or reproduction of information).
[0134]
The laser beam used for the optical recording medium of the present embodiment is N ₂ , He-Cd, Ar, He-Ne, ruby, semiconductor, dye laser, and the like, but a semiconductor laser is preferable because of its light weight, compactness, and easy handling.
The shorter the wavelength of the laser light used is for high-density recording, the more preferable is the laser light of 350 to 530 nm. Representative examples of such laser light include laser lights having center wavelengths of 405 nm, 410 nm, and 515 nm. An example of a laser beam 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, and in addition, 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-state laser excited by the semiconductor laser and capable of continuous oscillation having a fundamental oscillation wavelength of 740 to 960 nm is subjected to a second harmonic generation element (SHG). It can also be obtained by wavelength conversion.
[0135]
The SHG may be any piezo element that lacks inversion symmetry, but is preferably KDP, ADP, BNN, KN, LBO, or a compound semiconductor. Specific examples of the second harmonic include a semiconductor laser having a fundamental oscillation wavelength of 860 nm, a harmonic of 430 nm, and a solid-state laser pumped by a semiconductor laser includes a Cr-doped LiSrAlF. ₆ 430 nm, which is a harmonic wave from a crystal (a fundamental oscillation wavelength of 860 nm).
(4) Action / effect
Therefore, according to the optical recording medium, the method for manufacturing the optical recording medium, and the method for recording / reproducing the optical recording medium according to the present embodiment, the plurality of recording layers 22 for recording or reproducing information by irradiating light from one side. In the optical recording medium having the optical recording medium 25, light is incident on the thin film portion 25B of the second recording layer 25 located farther from the light incident side to record or reproduce information on the second recording layer 25. There is an advantage that good recording / reproducing characteristics (for example, reflectance, polarity, maximum signal amplitude, etc.) can be obtained when recording or reproducing information on the second recording layer 25 located on the side farther from the side from which light is incident. As a result, good recording / reproducing characteristics can be obtained in any of the plurality of recording layers 22 and 25.
(5) Other
In the present embodiment, an example in which the present invention is applied to a bonded dual layer type single-sided DVD-R has been described. However, the present invention is not limited to this. The present invention can be applied to an optical recording medium having another configuration as long as the optical recording medium has a plurality of dye-containing recording layers for performing recording or reproduction of the optical recording medium.
[0136]
For example, as shown in FIG. 2, a first recording layer containing a dye (a first dye-containing recording layer) is provided on a disk-shaped transparent (light-transmitting) first substrate (first light-transmitting substrate) 1. 2, translucent reflective layer (translucent reflective layer) 3, intermediate resin layer (intermediate layer) 4, second recording layer containing dye (second dye-containing recording layer) 5, reflective layer 6, second substrate 78 ( The present invention can also be applied to a laminated dual-layer type single-sided incidence DVD-R having an adhesive layer 7 and a base 8 in this order. Reference numerals 11 and 12 are guide grooves (grooves, concave portions).
[0137]
In this case, the guide groove (groove, concave portion) 12 provided on the second substrate 78 is used for recording or reproducing information on the second recording layer 5 located on the side farther from the side on which light is incident. In order to obtain the reflectivity, the depth of the guide groove 12 may be set in a range of 1/100 × λ to 1/6 × λ, where λ is the recording / reproducing wavelength.
[0138]
Further, in order to obtain good recording / reproducing characteristics, it is preferable to provide a recording track in the groove (groove, concave portion) 12 of the second substrate 78, that is, the concave portion (thin film portion) of the second recording layer 5. preferable. That is, information is recorded or reproduced by irradiating (irradiating) light into the groove (groove, concave portion) 12 of the second substrate 78, that is, the concave portion (thin film portion) of the second recording layer 5. preferable.
[0139]
It should be noted that the present invention is not limited to the above embodiment, and can be implemented with various modifications without departing from the spirit of the present invention.
[0140]
【Example】
Next, the present invention will be described in more detail by way of examples. The present invention is not limited by the following embodiments.
(Preparation of optical recording medium)
The optical recording medium according to the present invention includes, for example, a first substrate in which at least a first dye-containing recording layer containing a first dye and a translucent reflective layer are sequentially laminated on a first substrate having a guide groove. An information recording body, and a second information recording body in which at least a reflective layer and a second dye-containing recording layer containing a second dye are sequentially laminated on a second substrate having a guide groove; The first information recording body and the second information recording body are bonded together with an optically transparent adhesive layer facing the opposite side of the substrate.
[0141]
Hereinafter, description will be made focusing on production of the second information recording medium.
First, using a mother stamper (negative stamper), a second substrate made of polycarbonate having a track pitch of 740 nm, a guide groove having a predetermined groove depth and a predetermined groove width and a thickness of 0.6 mm (refractive index 1 .56).
Next, a reflective layer was formed on the second substrate by sputtering a silver alloy containing 97 atom% or more of Ag.
[0142]
Next, an octafluoropentanol solution of a metal-containing azo dye was spin-coated on the reflective layer under predetermined application conditions (dye concentration), and dried at 100 ° C. for 30 minutes to form a second dye-containing recording layer. . Here, the coating conditions were changed so that the film thickness of the second dye-containing recording layer became a predetermined film thickness. The recording layer had a refractive index of 2.25 and an extinction coefficient of 0.02.
[0143]
Next, on the second dye-containing recording layer, a silver alloy containing 97 atom% or more of Ag, (ZnS) ₈₀ (SiO ₂ ) ₂₀ , SiO ₂ Was sputtered to form a buffer layer, and a UV-curable resin (Nippon Kayaku SPC-920) was spin-coated thereon to a thickness of about 5 to 7 μm to form a protective layer. .
Then, usually, a radical ultraviolet curable resin (adhesive) is spin-coated on the protective layer and applied, and is bonded to the reflective layer side of the first substrate including the separately prepared recording layer (first recording layer). Thus, an optical recording medium is manufactured.
[0144]
However, in order to eliminate the influence of the first information recording medium and accurately evaluate the characteristics of the second recording layer, the first information recording medium has no recording layer and no translucent reflective layer. A 0.6 mm groove-free polycarbonate substrate (refractive index 1.56) was used. The cured adhesive layer had a refractive index of 1.53.
(Measuring method)
First, the reflectivity of the unrecorded second recording layer was measured using an evaluator equipped with a semiconductor laser having a wavelength of 657 nm (NA = 0.65) (DDU-1000 manufactured by Pulstec, maximum recording power 15 mW). Next, an EFM + signal of 8-16 modulation is recorded at a recording linear velocity of 3.8 m / s (1 × speed) at a recording power at which the asymmetry of the recording signal becomes almost 0, and its reflectance, polarity and maximum of the recording signal are recorded. The signal amplitude (the amplitude of the longest mark; so-called Modulation; I14 / I14H) was measured.
[0145]
In this example, the reflectivity was 25% or more, and the reflectivity was 30%. Usually, in order to obtain compatibility with a DVD-ROM, it is sufficient that the reflectance of the unrecorded portion of the second recording layer is more than 10%. Since the present embodiment does not have the first recording layer and the translucent reflective layer, the reflectivity tends to be higher than the actual one. However, if the reflectivity is 25% or more in the present embodiment, the actual It is considered that a reflectance of more than 10% can be obtained even if the influence of one information recording medium is considered.
[0146]
Further, in order to obtain compatibility with a DVD-ROM or the like, the polarity of the recording signal is preferably HtoL.
Furthermore, it is generally preferred that the maximum signal amplitude be large. Usually, it is preferably 0.5 or more, more preferably 0.6 or more.
The measurement results of the respective examples and comparative examples are as shown in Table 1 below.
[0147]
[Table 1]

[0148]
(Example 1)
In Example 1, a guide groove was formed on the second substrate so as to have a groove depth of 65 nm (corresponding to approximately λ / 10), a groove width (G width) of 320 nm, and a land width (L width) of 420 nm.
The buffer layer was formed by sputtering an Ag alloy. Then, the second recording layer was formed by spin-coating a metal-containing azo dye with a dye concentration of 3.55 wt% as a coating condition.
[0149]
The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 85 nm, and the film thickness (thin film portion, L film thickness) of the land portion was 70 nm. That is, the thickness difference between the thick film portion and the thin film portion of the second recording layer was 15 nm.
Land recording was performed on the optical recording medium thus manufactured under the above-mentioned conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. 0%, the polarity of the recording signal was HtoL (High to Low), and the maximum signal amplitude was 0.79.
(Comparative Example 1)
In Comparative Example 1, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 1 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 30.7%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was less than 0.1 (when recording was performed at a recording power of 15 mW).
[0150]
Thus, even with an optical recording medium manufactured in the same manner, if the groove recording is performed as in Comparative Example 1, the characteristics required for recording and reproduction cannot be obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 2)
In Example 2, a guide groove was formed on the second substrate so as to have a groove depth of 50 nm (corresponding to approximately λ / 13), a groove width (G width) of 410 nm, and a land width (L width) of 330 nm.
[0151]
The buffer layer is made of SiO. ₂ Was formed by sputtering. Then, the second recording layer was formed by spin-coating a metal-containing azo dye with a dye concentration of 3.55 wt% as a coating condition.
The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 105 nm, and the film thickness of the land portion (thin film portion, L film thickness) was 75 nm. That is, the thickness difference between the thick film portion and the thin film portion of the second recording layer was 30 nm.
[0152]
Land recording was performed on the optical recording medium thus manufactured under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As shown in Table 1, the reflectance was 36. 4%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.74.
Thus, the buffer layer is formed of SiO ₂ It was found that good recording and reproduction characteristics can be obtained even when the thickness and groove shape of the second recording layer were changed.
(Comparative Example 2)
In Comparative Example 2, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 2 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 30.9%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.36.
[0153]
Thus, even with an optical recording medium manufactured in the same manner, if the groove recording is performed as in Comparative Example 2, the characteristics necessary for recording and reproduction cannot be obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 3)
In the third embodiment, the thickness (thick film portion, G film thickness) of the groove portion of the second recording layer is set by setting the buffer layer to an Ag alloy and setting the dye concentration as a coating condition to 4.43 wt%. 130 nm and the thickness of the land portion (thin film portion, L film thickness) was 95 nm (that is, the difference in thickness between the thick film portion and the thin film portion of the second recording layer was 35 nm). Land recording was performed on the optical recording medium manufactured in the same manner as in Example 2 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. Was 31.1%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.71.
[0154]
Thus, the buffer layer is formed of SiO ₂ From this, it was found that recording / reproducing characteristics could be obtained even when the film thickness of the second recording layer was changed in place of the Ag alloy.
(Comparative Example 3)
In Comparative Example 3, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 3 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 29.1%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was LS (recording was impossible due to poor sensitivity; recording was performed at a recording power of 15 mW).
[0155]
Thus, even with an optical recording medium manufactured in the same manner, if the groove recording is performed as in Comparative Example 3, the characteristics required for recording and reproduction cannot be obtained, whereas the optical recording medium according to Example 3 is not obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 4)
In Example 4, the buffer layer was made of ZnS-SiO ₂ The land recording was performed on the optical recording medium produced in the same manner as in Example 3 except that the above conditions were satisfied, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As shown in the figure, the reflectance was 38.2%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.66.
[0156]
As described above, the buffer layer is made of ZnS-SiO ₂ It was found that good recording / reproducing characteristics could be obtained.
(Comparative Example 4)
In Comparative Example 4, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 4 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 31.3%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.31.
[0157]
As described above, even if the optical recording medium is manufactured in the same manner, when the groove recording is performed as in Comparative Example 4, the characteristics required for recording and reproduction cannot be obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 5)
In the fifth embodiment, the buffer layer is made of SiO ₂ The land recording was performed on the optical recording medium produced in the same manner as in Example 3 except that the above conditions were satisfied, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As shown in the figure, the reflectance was 36.1%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.73.
[0158]
As described above, the buffer layer is formed from the Ag alloy to the SiO 2 ₂ It was found that good recording / reproducing characteristics could be obtained.
(Comparative Example 5)
In Comparative Example 5, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 5 under the above-described conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 31.2%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.3.
[0159]
As described above, even if the optical recording medium is manufactured in the same manner, when the groove recording is performed as in Comparative Example 5, the characteristics required for recording and reproduction cannot be obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 6)
In Example 6, a guide groove was formed in the second substrate so as to have a groove depth of 30 nm (corresponding to approximately λ / 20), a groove width (G width) of 220 nm, and a land width (L width) of 520 nm.
[0160]
The buffer layer is made of ZnS-SiO ₂ Was formed by sputtering. Then, a metal-containing azo dye was spin-coated at a dye concentration of 3.10 wt% as a coating condition to form a second recording layer.
The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 110 nm, and the film thickness of the land portion (thin film portion, L film thickness) was 70 nm. That is, the thickness difference between the thick film portion and the thin film portion of the second recording layer was 40 nm.
[0161]
Land recording was performed on the optical recording medium thus manufactured under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As shown in Table 1, the reflectance was 43. 9%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.72.
Thus, the buffer layer is formed of ZnS-SiO ₂ In this case, it was found that better recording / reproducing characteristics could be obtained by changing the film thickness, groove width, and land width of the second recording layer.
(Comparative Example 6)
In Comparative Example 6, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 6 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 39.0%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.22.
[0162]
Thus, even with an optical recording medium manufactured in the same manner, if the groove recording is performed as in Comparative Example 6, the characteristics required for recording / reproduction cannot be obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 7)
In Example 7, the buffer layer was made of SiO ₂ Land recording was performed on the optical recording medium manufactured in the same manner as in Example 6 except that the above conditions were satisfied, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 49.5%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.58.
[0163]
Thus, the buffer layer is formed of ZnS-SiO ₂ From SiO ₂ It was found that, when the reflectance was changed, the reflectance was improved, but the maximum signal amplitude was slightly lowered, but the characteristics required for recording and reproduction could be obtained.
(Comparative Example 7)
In Comparative Example 7, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 7 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 43.2%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.11.
[0164]
As described above, even if the optical recording medium is manufactured in the same manner, when the groove recording is performed as in Comparative Example 7, the characteristics necessary for recording and reproduction cannot be obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 8)
In Example 8, the thickness (thick film portion, G film thickness) of the groove portion of the second recording layer was changed by setting the buffer layer to an Ag alloy and setting the dye concentration as a coating condition to 3.55 wt%. 135 nm and the thickness of the land portion (thin film portion, L film thickness) was 90 nm (that is, the difference in thickness between the thick film portion and the thin film portion of the second recording layer was 45 nm). Land recording was performed on the optical recording medium manufactured in the same manner as in Example 6 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. Was 33.9%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.79.
[0165]
Thus, the buffer layer is formed of ZnS-SiO ₂ From this, it was found that when the film thickness of the second recording layer was changed in place of the Ag alloy, the reflectivity was slightly deteriorated, but the maximum signal amplitude was improved, and characteristics necessary for recording and reproduction could be obtained.
(Comparative Example 8)
In Comparative Example 8, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 8 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 30.2%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was smaller than 0.1 (when recording was performed at a recording power of 15 mW).
[0166]
As described above, even if the optical recording medium is manufactured in the same manner, when the groove recording is performed as in Comparative Example 8, the characteristics necessary for recording and reproduction cannot be obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Example 9)
In the ninth embodiment, the buffer layer is made of SiO ₂ Land recording was performed on the optical recording medium manufactured in the same manner as in Example 8 except that the above conditions were satisfied, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectance was 44.2%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was 0.55.
[0167]
As described above, the buffer layer is formed from the Ag alloy to the SiO 2 ₂ It was found that, when the reflectance was changed, the reflectance was improved, but the maximum signal amplitude was slightly lowered, but the characteristics required for recording and reproduction could be obtained.
(Comparative Example 9)
In Comparative Example 9, groove recording was performed on the optical recording medium manufactured in the same manner as in Example 9 under the above conditions, and the reflectance, the polarity of the recording signal, and the maximum signal amplitude were measured. As a result, as shown in Table 1, the reflectivity was 41.7%, the polarity of the recording signal was HtoL, and the maximum signal amplitude was less than 0.1 (when recording was performed at a recording power of 15 mW).
[0168]
As described above, even if the optical recording medium is manufactured in the same manner, if the groove recording is performed as in Comparative Example 9, the characteristics required for recording and reproduction cannot be obtained, whereas the optical recording medium according to Example 9 is obtained. It was found that if land recording was performed, characteristics required for recording and reproduction could be obtained.
(Summary)
As described in Comparative Examples 1 to 9 above, if groove recording is used, recording / reproducing characteristics (reflectance, reflectance, etc.) required for recording or reproducing information of the second dye-containing recording layer located on the side farther from the side where light is incident. Polarity and maximum signal amplitude) cannot be obtained, but when land recording is performed as in the above-described Examples 1 to 9, information of the second dye-containing recording layer located far from the light incident side is obtained. It was found that the recording / reproducing characteristics (reflectance, polarity, maximum signal amplitude) necessary for recording or reproducing the data were obtained.
[0169]
In each of the above-described embodiments, in order to eliminate the influence of the first information recording medium and evaluate the characteristics of the second recording layer as accurately as possible, the recording layer and the translucent reflection layer are used as the first information recording medium. Although a substrate having no groove and having no groove was used, the evaluation of the second recording layer does not have a significant effect even if a normal first information recording medium is used.
Further, in the media of Examples 1 to 9, it is considered that an optical recording medium excellent in other recording / reproducing characteristics can be obtained by appropriately selecting a configuration other than the recording layer thickness.
[0170]
【The invention's effect】
As described above in detail, according to the optical recording medium, the recording / reproducing method of the optical recording medium, and the manufacturing method of the optical recording medium of the present invention, a plurality of dyes for recording or reproducing information by irradiating light from one side. In an optical recording medium having a content-containing recording layer, there is an advantage that good recording / reproduction characteristics can be obtained when recording or reproducing information in a dye-containing recording layer located on a side farther from a side from which light is incident.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of an optical recording medium according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing an overall configuration of another optical recording medium according to an embodiment of the present invention.
[Explanation of symbols]
1,21 1st substrate
2,22 First recording layer (first dye-containing recording layer)
3,23 translucent reflective layer
4 Intermediate resin layer (intermediate layer)
5,25 Second recording layer (second dye-containing recording layer)
6,26 reflective layer
7 Adhesive layer
8 Substrate
27 Second substrate
28 buffer layer
11, 12, 31, 32 groove (guide groove)
22A, 25A Thick film part
22B, 25B Thin film part
24 Transparent adhesive layer (intermediate layer)
78 Second substrate

Claims (8)

Optical recording including a first dye-containing recording layer and a second dye-containing recording layer, and recording or reproducing information of the first dye-containing recording layer and the second dye-containing recording layer by irradiating light from one side. A method for recording and reproducing a medium,
The second dye-containing recording layer has a thick film portion and a thin film portion, and information is recorded or reproduced on the second dye-containing recording layer by irradiating light to the thin film portion via the first dye-containing recording layer. A recording / reproducing method for an optical recording medium, wherein the recording / reproducing method is performed. The thick film portion and the thin film portion of the second dye-containing recording layer are formed so as to correspond to concave portions and convex portions of a substrate provided on a side opposite to a side on which light is incident, respectively. 3. The recording / reproducing method of the optical recording medium according to item 2. The first dye-containing recording layer has a thick film portion and a thin film portion, and information recording or reproduction of the first dye-containing recording layer is performed by irradiating light to the thick film portion. 3. The recording / reproducing method for an optical recording medium according to claim 1 or 2. 4. The method according to claim 3, wherein the thick film portion and the thin film portion of the first dye-containing recording layer are formed so as to correspond to concave portions and convex portions of a substrate provided on a light incident side, respectively. A recording / reproducing method for an optical recording medium. A first information recording body in which at least a first dye-containing recording layer containing a first dye and a translucent reflective layer are sequentially laminated on a first substrate having a guide groove; and a second information recording body having a guide groove. A second information recording body in which at least a reflective layer and a second dye-containing recording layer containing a second dye are sequentially laminated on a substrate, wherein the first information recording medium and the second information recording are provided. An optical recording medium that is attached to a body with an opposite surface of the substrate facing through an optically transparent adhesive layer and records or reproduces information by irradiating light from the first substrate side. So,
An optical recording medium, wherein the second dye-containing recording layer has a thick film portion and a thin film portion, and is configured to record or reproduce information by making light incident on the thin film portion. 6. The recording medium according to claim 5, wherein the first dye-containing recording layer has a thick film portion and a thin film portion, and is configured to record or reproduce information by making light incident on the thick film portion. The optical recording medium according to the above. An optical recording medium having a plurality of dye-containing recording layers for recording or reproducing information by irradiating light from one side,
The dye-containing recording layer located farther from the light incident side has a thick film portion and a thin film portion, and is configured to record or reproduce information by making light incident on the thin film portion. An optical recording medium, characterized by: A method of manufacturing an optical recording medium for manufacturing the optical recording medium according to claim 5,
A method for manufacturing an optical recording medium, comprising a step of forming a guide groove on the second substrate using a negative stamper.

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