JP4171674B2 - Optical recording medium, optical recording medium film thickness measuring method, film thickness controlling method, manufacturing method, film thickness measuring apparatus, and film thickness controlling apparatus - Google Patents

Description

【００４０】
（環Ａ¹及びＡ²は、各々独立に置換基を有していてもよい含窒素芳香族複素環であり、環Ｂ¹及びＢ²は、各々独立に置換基を有していてもよい芳香族環である。Ｘは、少なくとも２個のフッ素原子で置換されている炭素数１〜６のアルキル基である。）で表される化合物が好ましい。
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や、ＤＶＤ−Ｒに用いられるような波長６２０〜６９０ｎｍ程度の赤色レーザ、あるいは波長４１０ｎｍや５１５ｎｍなどのいわゆるブルーレーザなどでの記録に適する色素がより好ましい。
【００４１】
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。
【００４２】
また記録層は、記録層の安定や耐光性向上のために、一重項酸素クエンチャーとして遷移金属キレート化合物（例えば、アセチルアセトナートキレート、ビスフェニルジチオール、サリチルアルデヒドオキシム、ビスジチオ−α−ジケトン等）等や、記録感度向上のために金属系化合物等の記録感度向上剤を含有していても良い。ここで金属系化合物とは、遷移金属等の金属が原子、イオン、クラスター等の形で化合物に含まれるものを言い、例えばエチレンジアミン系錯体、アゾメチン系錯体、フェニルヒドロキシアミン系錯体、フェナントロリン系錯体、ジヒドロキシアゾベンゼン系錯体、ジオキシム系錯体、ニトロソアミノフェノール系錯体、ピリジルトリアジン系錯体、アセチルアセトナート系錯体、メタロセン系錯体、ポルフィリン系錯体のような有機金属化合物が挙げられる。金属原子としては特に限定されないが、遷移金属であることが好ましい。
【００４３】
さらに本光記録媒体の記録層には、必要に応じて、バインダー、レベリング剤、消泡剤等を併用することもできる。好ましいバインダーとしては、ポリビニルアルコール、ポリビニルピロリドン、ニトロセルロース、酢酸セルロース、ケトン系樹脂、アクリル系樹脂、ポリスチレン系樹脂、ウレタン系樹脂、ポリビニルブチラール、ポリカーボネート、ポリオレフィン等が挙げられる。
【００４４】
記録層の膜厚は、記録方法などにより適した膜厚が異なるため、特に限定するものではないが、十分な変調度を得るためには通常５ｎｍ以上が好ましく、より好ましくは１０ｎｍ以上であり、特に好ましくは２０ｎｍ以上である。但し、本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。記録層の膜厚は通常、溝部とランド部で異なるが、本光記録媒体において記録層の膜厚は基板の溝部における膜厚を言う。
【００４５】
記録層の成膜方法としては、真空蒸着法、スパッタリング法、ドクターブレード法、キャスト法、スピンコート法、浸漬法等一般に行われている薄膜形成法が挙げられるが、量産性、コスト面からはスピンコート法が好ましい。また厚みの均一な記録層が得られるという点からは、塗布法より真空蒸着法の方が好ましい。
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。
【００４６】
ドクターブレード法、キャスト法、スピンコート法、浸漬法等の塗布方法により記録層を形成する場合の塗布溶媒としては、基板を侵さない溶媒であればよく、特に限定されない。例えば、ジアセトンアルコール、３−ヒドロキシ−３−メチル−２−ブタノン等のケトンアルコール系溶媒；メチルセロソルブ、エチルセロソルブ等のセロソルブ系溶媒；ｎ−ヘキサン、ｎ−オクタン等の鎖状炭化水素系溶媒；シクロヘキサン、メチルシクロヘキサン、エチルシクロヘキサン、ジメチルシクロヘキサン、ｎ−ブチルシクロヘキサン、ｔｅｒｔ−ブチルシクロヘキサン、シクロオクタン等の環状炭化水素系溶媒；テトラフルオロプロパノール、オクタフルオロペンタノール、ヘキサフルオロブタノール等のパーフルオロアルキルアルコール系溶媒；乳酸メチル、乳酸エチル、２−ヒドロキシイソ酪酸メチル等のヒドロキシカルボン酸エステル系溶媒等が挙げられる。
【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、記録層を形成する。
【００４８】
（３）半透明反射層３について
半透明反射層３は、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がある必要がある。例えば、反射率の高い金属を薄く設けることにより適度な透過率を持たせることができる。また、ある程度の耐食性があることが望ましい。更に、半透明反射層３の上層（ここでは中間樹脂層４）の浸み出しにより第１記録層２が影響されないよう遮断性を持つことが望ましい。
【００４９】
高透過率を確保するために、半透明反射層３の厚さは通常、５０ｎｍ以下が好適である。より好適には３０ｎｍ以下である。更に好ましくは２０ｎｍ以下である。但し、第１記録層２が半透明反射層３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。
【００５０】
半透明反射層３の材料としては、再生光の波長で反射率が適度に高いもの、例えば、Ａｕ、Ａｌ、Ａｇ、Ｃｕ、Ｔｉ、Ｃｒ、Ｎｉ、Ｐｔ、Ｔａ、Ｐｄ、Ｍｇ、Ｓｅ、Ｈｆ、Ｖ、Ｎｂ、Ｒｕ、Ｗ、Ｍｎ、Ｒｅ、Ｆｅ、Ｃｏ、Ｒｈ、Ｉｒ、Ｚｎ、Ｃｄ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｔｅ、Ｐｂ、Ｐｏ、Ｓｎ、Ｂｉ及び希土類金属などの金属及び半金属を単独あるいは合金にして用いることが可能である。この中でもＡｕ、Ａｌ、Ａｇは反射率が高く半透明反射層３の材料として適している。これらを主成分とする以外に他成分を含んでいても良い。
【００５１】
なかでもＡｇを主成分としているものはコストが安い点、反射率が高い点から特に好ましい。ここで主成分とは含有率が５０％以上のものをいう。
半透明反射層３は膜厚が薄く、膜の結晶粒が大きいと再生ノイズの原因となるため、結晶粒が小さい材料を用いるのが好ましい。純銀は結晶粒が大きい傾向があるためＡｇは合金として用いるのが好ましい。
【００５２】
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。
【００５３】
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。
【００５４】
半透明反射層３としてはＡｕのみからなる層は結晶粒が小さく、耐食性に優れ好適である。ただし、Ａｇ合金に比べて高価である。
また、半透明反射層３としてＳｉからなる層を用いることも可能である。
金属以外の材料で低屈折率薄膜と高屈折率薄膜を交互に積み重ねて多層膜を形成し、反射層として用いることも可能である。
【００５５】
半透明反射層３を形成する方法としては、例えば、スパッタ法、イオンプレーティング法、化学蒸着法、真空蒸着法等が挙げられる。また、第１基板１と第１記録層２との間、及び又は、第１記録層２と半透明反射層３との間、に反射率の向上、記録特性の改善、密着性の向上等のために公知の無機系または有機系の中間層、接着層を設けることもできる。
【００５６】
（４）中間樹脂層４について
中間樹脂層４は、λ１光透過性及びλ２光透過性の両方の光透過性を有している必要があるほか、凹凸により溝やピットが形成可能である必要がある。また接着力が高く、硬化接着時の収縮率が小さいと媒体の形状安定性が高く好ましい。そして、中間樹脂層４は、第２記録層５にダメージを与えない材料からなることが望ましい。但し、中間樹脂層４は通常、樹脂からなるため第２記録層５と相溶しやすく、これを防ぎダメージを抑えるために両層の間に後述のバッファー層を設けることが望ましい。
【００５７】
さらに、中間樹脂層４は、半透明反射層３にダメージを与えない材料からなることが望ましい。但し、ダメージを抑えるために両層の間に後述のバッファー層を設けることもできる。
【００５８】
本光記録媒体において、中間樹脂層４の膜厚は正確に制御することが好ましい。中間樹脂層４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。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。
【００５９】
中間樹脂層４には凹凸が螺旋状又は同心円状に設けられ、溝及びランドを形成する。通常、このような溝及び／又はランドを記録トラックとして、第２記録層５に情報が記録・再生される。通常、第２記録層５は塗布形成されるので溝部で厚膜となり記録再生に適する。本光記録媒体においては中間樹脂層４の溝部、即ち光の入射方向に対して凸部を記録トラック１２とするのが好ましい。ここで、凹部、凸部はそれぞれ光の入射方向に対する凹部、凸部を言う。通常、溝幅は５０〜５００ｎｍ程度であり、溝深さは１０〜２５０ｎｍ程度である。また記録トラックが螺旋状である場合、トラックピッチは０．１〜２．０μｍ程度であることが好ましい。この他に必要に応じ、ランドプリピット等の凹凸ピットを有してもよい。
【００６０】
このような凹凸は、コストの観点から、凹凸を持つ樹脂スタンパ等から光硬化性樹脂などの硬化性樹脂に転写、硬化させて製造するのが好ましい。以下、このような方法を２Ｐ法（Ｐｈｏｔｏ Ｐｏｌｙｍｅｒｉｚａｔｉｏｎ法）と称することがある。
中間樹脂層４の材料としては、例えば、熱可塑性樹脂、熱硬化性樹脂、電子線硬化性樹脂、紫外線硬化性樹脂（遅延硬化型を含む）等を挙げることができる。
【００６１】
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、λ１光透過性及びλ２光透過性を有してい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。
【００６２】
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。
【００６３】
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。
【００６４】
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。
【００６５】
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。
【００６６】
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。
【００６７】
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。
【００６８】
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。
【００６９】
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。
【００７０】
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。
【００７１】
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。
【００７２】
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。
【００７３】
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。
【００７４】
（５）第２記録層５について
第２記録層５は、通常ＣＤ−Ｒや片面型ＤＶＤ−Ｒ等に用いられる光記録媒体に用いる記録層より高感度である必要がある。本光記録媒体においては、入射した光ビームのパワーが半透明反射層３の存在等で２分され、第１記録層２の記録と第２記録層５の記録とに振り分けられるため、約半分のパワーで記録するために、特に感度が高い必要があるのである。
【００７５】
また、良好な記録再生特性を実現するためには低発熱で高屈折率な色素であることが望ましい。
更に、第２記録層５と反射層６との組合せにおいて、光の反射及び吸収を適切な範囲とすることが望ましい。記録感度を高くし、かつ記録時の熱干渉を小さくできる。
【００７６】
第２記録層５の材料、成膜方法等についてはほぼ第１記録層２と同様に説明されるため、異なる点のみ説明する。
第２記録層５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。
第１記録層２と第２記録層５とに用いる材料は同じでも良いし異なっていてもよい。
【００７７】
（６）反射層６について
反射層６は、高反射率である必要がある。また、高耐久性であることが望ましい。
高反射率を確保するために、反射層６の厚さは通常、２０ｎｍ以上が好適である。より好適には３０ｎｍ以上である。更に好ましくは５０ｎｍ以上である。但し、記録感度を上げるためにはある程度薄いことが好ましく、通常４００ｎｍ以下とする。より好ましくは３００ｎｍ以下とする。
【００７８】
反射層６の材料としては、再生光の波長で反射率の十分高いもの、例えば、Ａｕ、Ａｌ、Ａｇ、Ｃｕ、Ｔｉ、Ｃｒ、Ｎｉ、Ｐｔ、Ｔａ及びＰｄの金属を単独あるいは合金にして用いることが可能である。この中でもＡｕ、Ａｌ、Ａｇは反射率が高く反射層６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。
【００７９】
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６は高耐久性（高耐食性）を確保するため、Ａｇは純銀よりもＡｇは合金として用いるのが好ましい。
【００８０】
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。
【００８１】
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。
【００８２】
反射層６としてはＡｕのみからなる層は高耐久性（高耐食性）が高く好適である。ただし、Ａｇ合金に比べて高価である。
金属以外の材料で低屈折率薄膜と高屈折率薄膜を交互に積み重ねて多層膜を形成し、反射層６として用いることも可能である。
反射層６を形成する方法としては、例えば、スパッタ法、イオンプレーティング法、化学蒸着法、真空蒸着法等が挙げられる。また、反射層６の上下に反射率の向上、記録特性の改善、密着性の向上等のために公知の無機系または有機系の中間層、接着層を設けることもできる。
【００８３】
（７）接着層７について
接着層７は、λ１光透過性及びλ２光透過性を有している必要はないが、接着力が高く、硬化接着時の収縮率が小さいと媒体の形状安定性が高く好ましい。
また、接着層７は反射層６にダメージを与えない材料からなることが望ましい。但し、ダメージを抑えるために両層の間に公知の無機系または有機系の保護層を設けることもできる。
【００８４】
本光記録媒体において、接着層７の膜厚は、通常２μｍ以上が好ましい。所定の接着力を得るためにはある程度の膜厚が必要である。より好ましくは５μｍ以上である。但し光記録媒体をできるだけ薄くするために、また硬化に時間を要し生産性が低下するなどの問題があるため、通常、１００μｍ以下が好ましい。
接着層７の材料は、中間樹脂層４の材料と同様のものが用いうるほか、感圧式両面テープ等も使用可能である。感圧式両面テープを反射層６と第２基板８との間に挟んで押圧することにより、接着層７を形成できる。
【００８５】
（８）第２基板８について
第２基板８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。また接着層７との接着性が高いことが望ましい。
上述のように第１基板１が十分な形状安定性を備えていない場合は、第２基板８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。但し第２基板８は透明である必要はない（即ち、λ１光透過性及びλ２光透過性を有している必要はない）。また第２基板８は鏡面基板で良く、凹凸を形成する必要はないので射出成形による転写性は必ずしも良い必要はない。
【００８６】
このような材料としては、第１基板１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。
【００８７】
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は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８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。
【００８８】
第２基板８は凹凸を持たない鏡面基板で良いが、生産しやすさの観点から、射出成型により製造するのが望ましい。
第１基板１と第２基板８の好ましい組合せの一例は、第１基板１と第２基板８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。
【００８９】
他の好ましい組合せの一例は、第１基板１が０．１ｍｍ程度と薄く、第２基板８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１はシート状であってもよい。
【００９０】
（９）その他の層について
上記積層構造において、必要に応じて任意の他の層を挟んでも良い。或いは媒体の最外面に任意の他の層を設けても良い。具体的には、半透明反射層３と中間樹脂層４との間、中間樹脂層４と第２記録層５との間、反射層６と接着層７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。
【００９１】
バッファー層は２つの層の混和を防止し、相溶を防ぐものである。バッファー層が混和現象を防止する以外の他の機能を兼ねていても良い。また必要に応じてさらに他の中間層を挟んでも良い。
バッファー層の材料は、第２記録層５や中間樹脂層４と相溶せず、かつ、λ１光透過性及びλ２光透過性を有している必要があり、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、λ１光透過性及びλ２光透過性を有する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。
【００９２】
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（Ｙ₂Ｏ₂Ｓ−ＺｎＯ）も好適である。
【００９３】
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。
【００９４】
その他、バッファー層作製時に記録層の色素を溶解しないようなものであれば樹脂層でも構わない。特に、真空蒸着やＣＶＤ法で作製可能な高分子膜が有用である。
バッファー層の厚さは２ｎｍ以上が好ましく、より好ましくは５ｎｍ以上である。バッファー層の厚さが過度に薄いと、上記の混和現象の防止が不十分となる虞がある。但し２０００ｎｍ以下が好ましく、より好ましくは５００ｎｍ以下である。バッファー層が過度に厚いと、混和防止には不必要であるばかりでなく、光の透過率を低下させる恐れもある。また無機物からなる層の場合には成膜に時間を要し生産性が低下したり、膜応力が高くなったりする虞があり２００ｎｍ以下が好ましい。特に、金属の場合は光の透過率を過度に低下させるため、２０ｎｍ以下程度が好ましい。
【００９５】
また、記録層や反射層を保護するために保護層を設けても良い。保護層の材料としては、λ１光透過性及びλ２光透過性を有している必要があるが、記録層や反射層を外力から保護するものであれば特に限定されない。有機物質の材料としては、熱可塑性樹脂、熱硬化性樹脂、電子線硬化性樹脂、紫外線硬化性樹脂等を挙げることができる。また、無機物質としては、酸化ケイ素、窒化ケイ素、ＭｇＦ₂、ＳｎＯ₂等が挙げられる。
【００９６】
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。
【００９７】
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、３〜５０μｍが好ましい。
【００９８】
更に、上記光記録媒体には、必要に応じて、記録・再生光の入射面ではない面に、インクジェット、感熱転写等の各種プリンタ、或いは各種筆記具にて記入（印刷）が可能な印刷受容層を設けてもよい。
或いは、本層構成の光記録媒体を２枚、第１基板１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。
【００９９】
〔Ａ−２〕光記録媒体の製造方法
次に、本実施形態に係るタイプ１の光記録媒体の製造方法について図２を用いて説明する。なお、図２は本製造方法を説明するための工程図である。
まず、図２（ａ）に示すように、表面に凹凸で溝及びランド、プリピットが形成された第１基板１を、スタンパをもとに射出成形または２Ｐ法等により作製する。
【０１００】
次に、図２（ｂ）に示すように、少なくとも有機色素を溶媒に溶解させた塗布液を第１基板１の凹凸を有する側の表面にスピンコート等により塗布し、第１記録層２を成膜する。なお、このとき、図２（ｂ）に示すようにディスク（第１基板１）の内周側に第１記録層２を形成しない所定領域３０ａを設けるようにする。また、この所定領域３０ａの幅Ｗ₁を、第１基板１の内周端部から例えば０．１ｍｍ〜５ｍｍ、好ましくは１ｍｍ程度で形成するのが良い。
【０１０１】
この後、図２（ｃ）に示すように、第１基板１の外周側を洗浄して第１記録層２を除去し、第１基板１が露出する所定領域３０ｂを形成する。また、このときの所定領域３０ｂの幅Ｗ₂を、上記の領域３０ａと同様に、第１基板１の外周端部から例えば０．１ｍｍ〜５ｍｍ、好ましくは１ｍｍ程度で形成するのが良い。この所定領域３０ａ，３０ｂは、後述する膜厚測定時において第２記録層５の膜厚を容易に測定できるようにする目的で形成されている。
【０１０２】
第１記録層２を成膜した後、図２（ｄ）に示すように、第１基板１の内周側の領域３０ａ及び外周側の領域３０ｂにマスクを被せ、Ａｇ合金などをスパッタまたは蒸着することにより、第１記録層２上に半透明反射層３を成膜する。
その後、図２（ｅ）に示すように、所定領域３０ａ，３０ｂを含む第１基板１の表面全体に紫外線硬化性樹脂等をスピンコート等により塗布する。このとき、紫外線硬化性樹脂（後に中間樹脂層４となる）は、第１基板１の所定領域３０ａ，３０ｂにおいて第１基板１と直接接する。
【０１０３】
次に、型を用いて紫外線硬化性樹脂の表面に凹凸を形成する。型としては、生産性、コストなどの観点から、図２（ｆ）に示すように、樹脂からなるスタンパ１５を用いるのが好ましい。
樹脂スタンパ１５は中間樹脂層４となるべき樹脂に対して十分な剥離性を有していれば良い。透明である必要はないが、成形性が良く、形状安定性が良いことが望ましい。生産性及びコストの観点から、望ましくは、樹脂スタンパ１５は複数回の転写に使用可能であるのが望ましい。また、使用後のリサイクルが可能であることが望ましい。
【０１０４】
樹脂スタンパ１５は、図２（ｆ）に示すように樹脂基板１６上に１層以上のセパレート層１７を有しても良いし、樹脂基板１６のみから構成してもよいが、後者のほうが生産性やコストの観点から好ましい。
まず、上述の樹脂スタンパ１５とは凹凸が逆（ネガ）の金属製スタンパを用い、射出成形や２Ｐ法等により樹脂基板１６を作製する。
【０１０５】
樹脂基板１６は透明である必要はないが、成形性が良く、形状安定性が良いことが望ましい。このような材料としては、例えばアクリル系樹脂、メタクリル系樹脂、ポリカーボネート樹脂、ポリオレフィン系樹脂（特に非晶質ポリオレフィン）、ポリエステル系樹脂、ポリスチレン樹脂、エポキシ樹脂等の樹脂からなるものが挙げられる。
【０１０６】
また、樹脂基板１６の厚さは、形状安定性及びハンドリングの容易さの点で、０．５ｍｍ以上とするのが望ましい。厚さの上限は特にないが、通常、３ｍｍ以下で十分である。
樹脂スタンパ１５が樹脂基板１６上に１層以上のセパレート層１７を有する構成であれば、樹脂基板１６はセパレート層１７との密着性が高い樹脂である必要があり、その他成形性などの高生産性、コスト、低吸湿性、形状安定性などの点からポリカーボネートが好ましい。
【０１０７】
セパレート層１７は中間樹脂層４を構成する樹脂との密着性が低く剥離性が高いことが望ましい。また、成膜されたときに樹脂基板１６の凹凸を忠実に反映した凹凸が形成されることが望ましい。
セパレート層１７の材料としては、中間樹脂層４の樹脂との剥離性の点から金属または合金が好ましく、通常、Ａｇ、Ａｕ、Ｃｕ、Ｐｔ及びＰｄから選ばれる金属またはそれらの合金が用いられる。
【０１０８】
セパレート層１７の厚さは、中間樹脂層４からの剥離性を確保するためにはある程度の膜厚が必要で、２ｎｍ以上とするのが好ましい。一方、基板の凹凸を忠実に反映するためには厚すぎないことが望ましく、通常、２００ｎｍ以下が好ましい。
樹脂スタンパ１５が樹脂基板１６のみからなる構成であれば、樹脂基板１６は中間樹脂層４を構成する樹脂との密着性が低く剥離性が高いことが望ましい。その他成形性などの高生産性、コスト、低吸湿性、形状安定性などの点から非晶質ポリオレフィンが好ましい。
【０１０９】
したがって、第１基板１上に紫外線硬化性樹脂等をスピンコート等により塗布した後、上述したような樹脂スタンパ１５を載置し、紫外線硬化性樹脂に凹凸を転写する。このとき、紫外線硬化性樹脂の膜厚が所定範囲になるように調節しつつ行なう。
そして、この状態で第１基板１側から紫外線を照射するなどして紫外線硬化性樹脂を硬化させ、十分硬化したところで樹脂スタンパ１５を剥離し、図２（ｇ）に示すように、表面に凹凸を有する中間樹脂層４を形成する。或いは紫外線を媒体の側面から照射することもできる。いずれにせよ、この紫外線により第１記録層１がダメージを受けないようにする必要がある。
【０１１０】
続いて、図２（ｈ）に示すように、少なくとも有機色素を溶媒に溶解させた塗布液をスピンコート等により中間樹脂層４表面（即ち、第１記録層２及び半透明反射層３の領域よりも所定領域だけ広い領域）に塗布し、第２記録層５を成膜する。
そして、図２（ｉ）に示すように、Ａｇ合金などをスパッタ、蒸着することにより第２記録層５上に反射層６を成膜する。
【０１１１】
その後、図２（ｊ）に示すように、ポリカーボネートを射出成形して得られた第２基板８としての鏡面基板を、接着層７を介して反射層６に貼り合わせる。これにより、光記録媒体の製造が完了する。
なお、接着層７は、不透明でも、表面が多少粗くてもよく、遅延硬化型の接着剤を問題なく使用できる。反射層６上に接着剤をスクリーン印刷等で塗布し、紫外線を照射してから第２基板８を載置し押圧して接着層７を形成できる。或いは、反射層６と第２基板８との間に感圧式両面テープを挟んで押圧することにより、接着層７を形成することもできる。
【０１１２】
〔Ａ−３〕光記録媒体の膜厚測定方法及び膜厚制御方法
本実施形態に係るタイプ１の光記録媒体では、公知の透過法を用いて第１記録層２及び第２記録層５の膜厚を測定することができる。良質な特性を有する光記録媒体を製造するにあたって、第１記録層２及び第２記録層５の膜厚制御をより正確に行なうことが重要である。
【０１１３】
第１記録層２については、図２（ｂ）に示すように第１基板１上に第１記録層２を成膜した後に、第１記録層２上面側から或いは第１基板１下面側から光（例えば赤色レーザ，Ｈｅ−Ｎｅレーザ，Ｈｅ−Ｃｄレーザ等。好ましくは可視光）を照射してその透過率の測定を行なえば、第１記録層２の上下側に反射層等の透過率の低い層がなんら存在しないので第１記録層２の膜厚を容易に測定することができる。
【０１１４】
また、第２記録層５については、図２（ｈ）に示すように中間樹脂層４上に第２記録層５を成膜した後に、第２記録層５上面側から或いは第１基板１下面側から光を照射してその透過率の測定を行なうことにより膜厚を測定できるが、このとき、光を図２（ｈ）に示す矢印の位置、即ち、所定領域３０ａ又は／及び３０ｂに照射する。この所定領域３０ａ，３０ｂの範囲では、第２記録層５の下層に、λ１光透過性を有する中間樹脂層４及び第１基板１のみ存在し、反射層等の透過率の低い層はなんら存在しないので、第２記録層５の膜厚も容易に測定することが可能である。
【０１１５】
このように、第２記録層５の領域が、第１記録層２の領域及び半透明反射層３の領域よりも所定領域だけ広く形成されることで、第１記録層２及び半透明反射層３に邪魔されることなく第２記録層５の膜厚を透過法で測定できる。
なお、所定領域３０ａ，３０ｂにおいて、中間樹脂層４と第１基板１との間、或いは第２記録層５と中間樹脂層４との間にバッファー層や保護層が存在していても、これらバッファー層や保護層はλ１光透過性を有しているので、上記と同様に第２記録層５の膜厚を容易に測定することが可能である。
【０１１６】
また、第１基板１の直径方向において複数点の膜厚測定を行なうことで、より正確な膜厚を求めることが可能となる。
なお、本実施形態では、第１基板１の内周側及び外周側の両方に所定領域を設けるように構成したが、内周側のみ或いは外周側のみに設けるように構成しても良い。
【０１１７】
また、上記の膜厚測定は、本光記録媒体を製造する製造装置内（即ち製造過程）において図示省略の膜厚測定装置により自動的に行なわれ、このとき測定された膜厚情報は、第１記録層２及び第２記録層５の膜厚を制御する膜厚制御装置（図示省略）にフィードバックされるようになっている。
【０１１８】
つまり、例えば膜厚測定装置により第１記録層２の膜厚が測定されると、この膜厚情報が膜厚制御装置に送信され、膜厚制御装置では、この膜厚情報に基づいて、第１記録層２形成用の塗布液の塗布量（または濃度）、温度、湿度、塗布液を塗布する時間、塗布液を塗布する際の第１基板１の回転数、第１基板１が最高回転数に到達するまでの時間等が調節されて、次のディスクの第１記録層２の膜厚が適切な膜厚になるように制御される。また、次のディスクの第２記録層５の膜厚制御も第１記録層２の膜厚制御と同様にして行なうことができる。もちろん、第１記録層２の膜厚情報に基づいて、第１記録層２よりも上側に積層される第２記録層５の膜厚を制御したり、また、３つ以上の複数の記録層を有する光記録媒体であって第２記録層５のさらに上側に記録層が積層される場合には、その記録層の膜厚を制御したりすることも可能である。
【０１１９】
〔Ｂ〕第２実施形態
〔Ｂ−１〕光記録媒体の構成
図３は本実施形態に係る光記録媒体（タイプ２）を示す模式的な断面図である。
本実施形態に係るタイプ２の光記録媒体は、ディスク状の透明な（光透過性の）第１基板（第１の基板）２１上に、色素を含む第１記録層（第１の色素含有記録層）２２、半透明の反射層（以下、半透明反射層という。第１の反射層）２３、透明接着層２４、バッファー層２８、色素を含む第２記録層（第２の色素含有記録層）２５、反射層（第２の反射層）２６、ディスク状の透明な第２基板（第２の基板）２７をこの順に有してなる。光ビームは第１基板２１側から照射され、記録・再生が行われる。
【０１２０】
なお、本発明において「光透過性（又は透明）」とは、透過法による膜厚測定（これについては後述する）において用いられる光の波長に対する光透過性（λ１光透過性という）と、光記録媒体の記録・再生を行なう際に用いられる光の波長に対する光透過性（λ２光透過性という）との２つの光透過性を意味する。また、上記の膜厚測定光の波長及び記録再生光の波長について５０％以上、好ましくは６０％以上の透過性があれば実質的に光透過性であるといえる。
【０１２１】
第１基板２１、第２基板２７上にはそれぞれ凹凸が形成され、それぞれ記録トラックを構成する。記録トラックは凸部及び凹部のどちらでも良いが、第１基板２１上の記録トラック３１は、光の入射方向に対して凸部で構成されるのが好ましく、第２基板２７上の記録トラック３２は、光の入射方向に対して凹部で構成されるのが好ましい。この他に必要に応じ凹凸ピットを有することもある。特に断らない限り、本実施形態において凹凸は記録・再生に用いる光の入射方向に対して定義される。
【０１２２】
次に、各層について説明する。
本実施形態に係る第１基板２１，第１記録層２２，半透明反射層２３，第２記録層２５，反射層２６はそれぞれ、第１実施形態に係る第１基板１，第１記録層２，半透明反射層３，第２記録層５，反射層６と略同様の構成である。
また、中間層としての透明接着層２４は、少なくともλ２光透過性を有している必要がある。そして、凹凸により溝やピットを形成する必要がないという以外は、第１実施形態における中間樹脂層４の構成と略同様の構成である。なお、本光記録媒体では、上記の溝やピットは後述する第２基板２７に形成されている。
【０１２３】
さらに、中間層としてのバッファー層２８は、第１実施形態において説明したバッファー層と略同様の構成である。なお、このバッファー層は必要に応じて形成するようにしても良い。
第２基板２７は、少なくともλ１光透過性を有している必要があるほか、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。
【０１２４】
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。
【０１２５】
第２基板２７には、凹凸が螺旋状又は同心円状に設けられ、溝及びランドを形成する。通常、このような溝及び／又はランドを記録トラックとして、第２記録層２５に情報が記録・再生される。通常、第２記録層２５は塗布形成されるので溝部で厚膜となり記録再生に適する。本光記録媒体においては第２基板２７の溝部、即ち光の入射方向に対して凹部を記録トラック３２とするのが好ましい。ここで、凹部、凸部はそれぞれ光の入射方向に対する凹部、凸部を言う。通常、溝幅は５０〜５００ｎｍ程度であり、溝深さは１０〜２５０ｎｍ程度である。また記録トラックが螺旋状である場合、トラックピッチは０．１〜２．０μｍ程度であることが好ましい。この他に必要に応じ、ランドプリピット等の凹凸ピットを有してもよい。
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。
また、記録層や反射層を保護するために、第１実施形態で説明した保護層を設けても良い。保護層の材料としては、λ１光透過性及びλ２光透過性を有している必要があるが、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。
【０１２６】
〔Ｂ−２〕光記録媒体の製造方法
次に、本実施形態に係るタイプ２の光記録媒体の製造方法について図４を用いて説明する。なお、図４は本製造方法を説明するための工程図である。
本光記録媒体は、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の構成物）Ａを作製し、また、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の構成物）Ｂを作製した後、両積層構造Ａ，Ｂを、互いに記録層２２，２５が内側にくるように（対向するように）して透明接着層２４を介して貼り合わせることで製造される。
【０１２７】
まず、図４（ａ）に示すように、表面に凹凸で溝及びランド、プリピットが形成された第１基板２１を、射出成形または２Ｐ法等により作製する。
次に、図４（ｂ）に示すように、少なくとも有機色素を溶媒に溶解させた塗布液を第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塗布し、第１記録層２２を成膜する。
【０１２８】
第１記録層２２を形成した後、図４（ｃ）に示すように、Ａｇ合金などをスパッタまたは蒸着することにより、第１記録層２２上に半透明反射層２３を成膜し、積層構造Ａとする。
一方、図４（ｄ）に示すように、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法等により作製する。
【０１２９】
そして、図４（ｅ）に示すように、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又は蒸着することにより反射層２６を成膜する。なお、このとき、図４（ｅ）に示すようにディスク（第２基板２７）の内周側及び外周側にマスクなどを被せて反射層２６を形成しない所定領域４０ａ，４０ｂを設けるようにする。また、この所定領域４０ａの幅Ｗ₁₀を、第２基板２７の内周端部から例えば０．１ｍｍ〜５ｍｍ、好ましくは１ｍｍ程度で形成するのが良く、所定領域４０ｂの幅Ｗ₂₀を、第２基板２７の外周端部から例えば０．１ｍｍ〜５ｍｍ、好ましくは１ｍｍ程度で形成するのが良い。この所定領域４０ａ，４０ｂは、後述する膜厚測定時において第２記録層５の膜厚を容易に測定できるようにする目的で形成されている。
【０１３０】
反射層２６を成膜した後、図４（ｆ）に示すように、反射層２６の領域よりも広い領域に、少なくとも有機色素を溶媒に溶解させた塗布液をスピンコート等により塗布し、第２記録層２５を成膜する。このとき、第２記録層２５は、第２基板２７の所定領域４０ａ，４０ｂにおいて第２基板２７と直接接する。
次いで、図４（ｇ）に示すように、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、積層構造Ｂとする。
【０１３１】
そして、図４（ｈ）に示すように、積層構造Ａ上に透明接着層２４となる紫外線硬化性樹脂等の接着剤を塗布したのち積層構造Ｂを載置し、高速回転、押圧等により接着剤を全面に広げる。このとき、透明接着層２４の膜厚が所定範囲になるように調節しつつ行なう。その後、第１基板２１下面側から半透明反射層２３を介して紫外線を照射し、硬化接着させることでタイプ２の光記録媒体を製造できる。或いは紫外線を媒体の側面から照射することもできる。いずれにせよ、この紫外線により第１記録層２２がダメージを受けないように注意が必要である。
【０１３２】
また、積層構造Ａ，Ｂ間に感圧式両面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、積層構造Ａ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積層構造Ｂ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。
【０１３３】
〔Ｂ−３〕光記録媒体の膜厚測定方法及び膜厚制御方法
本実施形態に係るタイプ２の光記録媒体では、第１実施形態と同様に、公知の透過法を用いて第１記録層２２及び第２記録層２５の膜厚を測定することができる。
第１記録層２２については、図４（ｂ）に示すように第１基板２１上に第１記録層２２を成膜した後に、第１記録層２２上面側から或いは第１基板２１下面側から光（例えば赤色レーザ，Ｈｅ−Ｎｅレーザ，Ｈｅ−Ｃｄレーザ等。好ましくは可視光）を照射して第１記録層２２の透過率測定を行なえば、第１記録層２２の上下側に反射層等の透過率の低い層がなんら存在しないので第１記録層２２の膜厚を容易に測定することができる。
【０１３４】
また、第２記録層２５については、図４（ｆ）に示すように反射層２６上に第２記録層２５を成膜した後に、第２記録層２５上面側から或いは第２基板２７下面側から光を照射して第２記録層２５の透過率測定を行なうことにより膜厚を測定できるが、このとき、光を図４（ｆ）に示す矢印の位置、即ち、所定領域４０ａ又は／及び４０ｂに照射する。この所定領域４０ａ，４０ｂの範囲では、図４（ｆ）に示す第２記録層２５の下層にはλ１光透過性を有する第２基板２７のみ存在し、反射層等の透過率の低い層はなんら存在しないので、第２記録層２５の膜厚を容易に測定することが可能である。
【０１３５】
このように、第２記録層２５の領域が、第２反射層２６の領域よりも所定領域だけ広く形成されることで、第２反射層２６に邪魔されることなく第２記録層２６の膜厚を透過法で測定できる。
なお、所定領域４０ａ，４０ｂにおいて、第２基板２７と第２記録層２５との間にバッファー層や保護層が存在していても、これらバッファー層や保護層はλ１光透過性を有しているので、上記と同様に第２記録層２５の膜厚を容易に測定することが可能である。
【０１３６】
また、第２基板２７の直径方向において複数点の膜厚測定を行なうことで、より正確な膜厚を求めることが可能となる。
なお、本実施形態では、第２基板２７の内周側及び外周側の両方に所定領域を設けるように構成したが、内周側のみ或いは外周側のみに設けるように構成しても良い。
【０１３７】
また、上記の膜厚測定は、本光記録媒体を製造する製造装置内（即ち製造過程）において図示省略の膜厚測定装置により自動的に行なわれ、このとき測定された膜厚情報は、第１記録層２２及び第２記録層２５の膜厚を制御する膜厚制御装置（図示省略）にフィードバックされるようになっている。
つまり、例えば膜厚測定装置により第１記録層２２の膜厚が測定されると、この膜厚情報が膜厚制御装置に送信され、膜厚制御装置では、この膜厚情報に基づいて、第１記録層２２形成用の塗布液の塗布量（または濃度）、温度、湿度、塗布液を塗布する時間、塗布液を塗布する際の第１基板２１の回転数、第１基板２１が最高回転数に到達するまでの時間等が調節されて、次のディスクの第１記録層２２の膜厚が適切な膜厚になるように制御される。また、次のディスクの第２記録層２５の膜厚制御も第１記録層２２の膜厚制御と同様にして行なうことができる。
【０１３８】
〔Ｃ〕その他
以上、本発明の実施形態について説明したが、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。
【０１３９】
例えば、第１，２実施形態では、２つの記録層を有する光記録媒体について説明したが、光記録媒体が３つ以上の複数の記録層を有していても良い。この場合、第１実施形態に係るタイプ１の光記録媒体の製造方法により製造することが好ましい。例えば図５に示すように、第１実施形態に係る光記録媒体の第２記録層５と反射層６との間に半透明反射層３′，中間樹脂層４′，第３記録層５′を介装した積層構造とする。また、第２記録層５の膜厚測定のための所定領域３０ａ，３０ｂを設けるとともに、第３記録層５′の膜厚測定のための所定領域３０ａ′，３０ｂ′を設けるようにする。このとき、所定領域３０ａ′，３０ｂ′の幅がそれぞれ所定領域３０ａ，３０ｂの幅よりも小さくなるように形成することで、第３記録層５′の膜厚を容易に測定することができる。このように、３つ以上の複数の記録層を有する光記録媒体でも、上記のように所定領域を設けることで、透過法により各記録層の膜厚を製造過程において容易に測定することが可能となる。
【０１４０】
また、第１，２実施形態では、基板側からレーザ光を照射して情報の記録・再生を行なう基板入射型光ディスクについて説明したが、基板／反射層／記録層／保護層からなる積層構造を有し、保護層側（即ち、膜面側）からレーザ光を照射して情報の記録・再生を行なう膜面入射型光ディスクにおいても適用できる。
【０１４１】
【発明の効果】
以上詳述したように、請求項１記載の本発明の光記録媒体によれば、光透過性の基板と色素含有記録層との間に反射層が設けられた積層構造であっても、色素含有記録層の領域が反射層の領域よりも所定領域だけ広い領域に形成されているので、この所定領域において透過法により色素含有記録層の膜厚を容易に測定することができる。
【０１４２】
請求項２記載の本発明の光記録媒体によれば、第２の色素含有記録層の領域が、第１の色素含有記録層の領域及び第１の反射層の領域よりも所定領域だけ広く形成されているので、この所定領域において透過法により第２の色素含有記録層の膜厚を容易に測定することができる。
請求項３記載の本発明の光記録媒体によれば、所定領域において、第１の基板と中間層とが直接又は光透過性の層を介して接しているので、この所定領域において、透過法により第２の色素含有記録層の膜厚を容易に測定することができる。
【０１４３】
請求項４記載の本発明の光記録媒体によれば、第２の色素含有記録層の領域が、第２の反射層の領域よりも所定領域だけ広く形成されているので、この所定領域において透過法により第２の色素含有記録層の膜厚を容易に測定することができる。
請求項５記載の本発明の光記録媒体によれば、所定領域において、第２の基板と第２の色素含有記録層とが直接又は光透過性の層を介して接しているので、この所定領域において、透過法により第２の色素含有記録層の膜厚を容易に測定することができる。
【０１４４】
請求項６記載の本発明の光記録媒体によれば、所定領域が、基板の内周側及び／又は外周側に設けられているので、直径方向において複数点の膜厚測定を行なうことで、より正確な膜厚を求めることが可能である。
請求項７記載の本発明の光記録媒体の膜厚測定方法によれば、所定領域において、透過法により色素含有記録層の膜厚を容易に測定できる。
【０１４５】
請求項８記載の本発明の光記録媒体の膜厚制御方法によれば、所定領域において透過法により色素含有記録層の膜厚を測定し、この膜厚測定情報に基づいて、その後に形成される色素含有記録層の膜厚を制御するので、より正確な膜厚制御が可能である。
請求項９記載の本発明の光記録媒体の製造方法によれば、所定領域において透過法により色素含有記録層の膜厚を測定し、この膜厚測定情報に基づいて、その後に形成される色素含有記録層の膜厚を制御する工程を含んでいるので、より正確な膜厚制御が可能であり、良質な特性を有する光記録媒体を製造することができる。
【０１４６】
請求項１０記載の本発明の光記録媒体の膜厚測定装置によれば、所定領域において透過法により色素含有記録層の膜厚を容易に測定できる。
請求項１１記載の本発明の光記録媒体の膜厚制御装置によれば、所定領域において透過法により色素含有記録層の膜厚を測定し、この膜厚測定情報に基づいて、その後に形成される色素含有記録層の膜厚を制御するので、より正確な膜厚制御が可能である。
【図面の簡単な説明】
【図１】本発明の第１実施形態としての光記録媒体（タイプ１）を示す模式図である。
【図２】本発明の第１実施形態としての光記録媒体（タイプ１）の製造方法を示す工程図である。
【図３】本発明の第２実施形態としての光記録媒体（タイプ２）を示す模式図である。
【図４】本発明の第２実施形態としての光記録媒体（タイプ２）の製造方法を示す工程図である。
【図５】本発明の第１実施形態としての光記録媒体（タイプ１）の変形例を示す模式図である。
【図６】従来の光記録媒体の一例を示す模式図である。
【符号の説明】
１，２１ 第１基板（第１の基板）
２，２２ 第１記録層（第１の色素含有記録層）
３，２３ 半透明反射層（第１の反射層）
４ 中間樹脂層（中間層）
５，２５ 第２記録層（第２の色素含有記録層）
６，２６ 反射層（第２の反射層）
７ 接着層
８，２７ 第２基板（第２の基板）
２８ バッファー層（中間層）
１１，１２，３１ 凸部からなる記録トラック
２４ 透明接着層（中間層）
３２ 凹部からなる記録トラック
３０ａ，３０ｂ，３０ａ′，３０ｂ′，４０ａ，４０ｂ 所定領域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording medium, a film thickness measuring method, a film thickness controlling method, a manufacturing method, a film thickness measuring apparatus, and a film thickness controlling apparatus.
[0002]
[Prior art]
Currently, various optical recording media such as CD-R, CD-RW, and MO can store a large amount of information and are easily accessible at random, so that they are widely recognized as external storage devices in information processing apparatuses such as computers. It is becoming popular. Furthermore, it is desired to increase the storage density by increasing the amount of information handled.
[0003]
Among various optical recording media, an optical disc having a recording layer containing an organic dye (also referred to as a dye-containing recording layer) such as CD-R and DVD-R is relatively inexpensive and compatible with a read-only optical disc. In particular, it is widely used.
As an example, a medium such as a CD-R that is typical as an optical disk having a recording layer containing an organic dye has a dye-containing recording layer and a reflective layer in this order on a transparent disk substrate. And a recording / reproducing operation using a laser beam through a substrate.
[0004]
Similarly, a typical single-sided DVD-R has a dye-containing recording layer, a reflective layer, and a protective layer covering them in this order on the first transparent disk substrate, and further, via an adhesive layer on the protective layer or A laminated structure in which a so-called dummy disk in which a reflective layer is formed on a second transparent disk substrate is provided without intervention, and recording / reproduction is performed with laser light through the first transparent disk substrate. The dummy disk may be only a transparent disk substrate, or a layer other than the reflective layer may be provided.
[0005]
One means for further increasing the recording capacity of these optical recording media is to provide a plurality of recording layers, for example, two layers (dual layers) on one medium. Further, in this case, it is desired for convenience to be able to record / reproduce the two recording layers from one side. For example, an optical recording medium as shown in FIG. 6 has been developed (for example, a patent). Reference 1).
[0006]
That is, as shown in FIG. 6, the conventional optical recording medium is a first information recording composed of an organic dye capable of optically recording information on a first light-transmissive substrate 5 by irradiation with a recording laser beam. A layer 12, a reflective layer 13 composed of a semi-transparent reflective film capable of transmitting a part of the reproduction laser beam, and an intermediate layer having translucency with respect to the recording laser beam and the reproduction laser beam 11, a second information recording layer 12 ′ made of an organic dye capable of optically recording information by irradiation with a recording laser beam, a second reflecting layer 13 ′ that reflects the reproducing laser beam, and a second The light-transmitting substrate 5 'is laminated in this order.
[0007]
With this configuration, information can be recorded on the first information recording layer 12 and the second information recording layer 12 ′ from one side of the optical recording medium, and so-called dual layer type light can be recorded even during reproduction. A signal can be read from one side as a recording medium.
As a method for manufacturing an optical recording medium having such a laminated structure, for example, the first information recording layer 12, the first reflective layer 13, the intermediate layer 11, the first layer on the first translucent substrate 5 are used. A second information recording layer 12 ′ and a second reflective layer 13 ′ are formed in this order, and finally a second translucent substrate 5 ′ is bonded (type 1); The first information recording layer 12 and the first reflective layer 13 are formed in this order on the optical substrate 5 to produce the first component, while the second information is formed on the second transparent substrate 5 ′. The reflective layer 13 ′ and the second information recording layer 12 ′ are formed in this order to produce a second constituent, and the first reflective layer 13 and the second constituent of the first constituent are formed via the intermediate layer 11. A method (type 2) in which the second information recording layer 12 'of the component is bonded so as to face each other can be considered.
[0008]
[Patent Document 1]
JP 11-66622 A
[0009]
[Problems to be solved by the invention]
By the way, in order to obtain good characteristics in an optical recording medium, it is important to precisely control the film thickness of the recording layer. Various methods for measuring the film thickness are known, but the transmission method is often used because it is simpler and cheaper than the reflection method.
[0010]
In the transmission method, generally, a film to be measured is irradiated with light (for example, a red laser, a He—Ne laser, a He—Cd laser, etc., preferably visible light) to measure a transmitted light amount, and an incident light amount and a transmitted light are measured. This is a method of calculating the film thickness by deriving the transmittance from the light quantity ratio. However, even with the transmission method, some light is reflected when light is incident. Therefore, if the light absorption rate of the medium is small, the amount of transmitted light can be measured indirectly by measuring the amount of reflected light. It is.
[0011]
For example, a CD-R is composed of a substrate / dye-containing recording layer / reflection layer, and after coating the dye-containing recording layer on the substrate, the film thickness of the dye-containing recording layer was measured by a transmission method. Then, feedback is applied to the coating process so that the film thickness becomes a desired film thickness. The same applies to the film thickness control of DVD-R.
However, in the above-described dual layer optical recording medium, for example, when the optical recording medium is manufactured by the type 1 manufacturing method, the first reflective layer 13 is present below the second information recording layer 12 '. Thus, it is difficult to accurately measure the film thickness of the second information recording layer 12 '.
[0012]
Further, when an optical recording medium is manufactured by the type 2 manufacturing method, a second reflective layer 13 ′ is present between the second translucent substrate 5 ′ and the second information recording layer 12 ′. Therefore, it is difficult to accurately measure the thickness of the second information recording layer 12 'as described above.
As described above, in the optical recording medium in which the reflective layer or the like is provided between the substrate and the recording layer, the film thickness of the recording layer cannot be accurately measured. It has been difficult to control the thickness of the recording layer of the manufactured optical recording medium.
[0013]
The present invention was devised in view of such problems, and in an optical recording medium in which a reflective layer or the like is provided between a substrate and a recording layer, the film thickness of the recording layer can be easily measured by a transmission method. An object of the present invention is to provide an optical recording medium, a film thickness measuring method, a film thickness controlling method, a manufacturing method, a film thickness measuring apparatus, and a film thickness controlling apparatus.
[0014]
[Means for Solving the Problems]
For this reason, the optical recording medium of the present invention (Claim 1) includes a reflective layer between a light-transmitting substrate and a dye-containing recording layer on which information can be optically recorded. The region is characterized by being formed by a predetermined region wider than the region of the reflective layer.
Thereby, the film thickness of the dye-containing recording layer can be measured by the transmission method without being disturbed by the reflective layer.
[0015]
An optical recording medium of the present invention (Claim 2) includes a light-transmitting first substrate, a first dye-containing recording layer on which information can be optically recorded, and the first substrate. A first reflective layer on one dye-containing recording layer, a second dye-containing recording layer on which information can be optically recorded on the first reflective layer, and the second dye-containing recording layer And a second reflective layer, and a region of the second dye-containing recording layer is formed by a predetermined region wider than a region of the first dye-containing recording layer and a region of the first reflective layer. It is characterized by being. Note that the second substrate may be provided on the second reflective layer via an adhesive layer.
Thereby, the film thickness of the second dye-containing recording layer can be measured by the transmission method without being disturbed by the first dye-containing recording layer and the first reflective layer.
[0016]
A light-transmitting intermediate layer is provided between the first reflective layer and the second dye-containing recording layer, and the first substrate and the intermediate layer are directly or light-transmitting in the predetermined region. It is preferable that they are in contact with each other through a conductive layer (claim 3).
[0017]
An optical recording medium of the present invention (Claim 4) includes a first substrate that is light transmissive, a first dye-containing recording layer on which information can be optically recorded on the first substrate, and the first recording layer. A first reflective layer on one dye-containing recording layer, a second dye-containing recording layer on which information can be optically recorded on the first reflective layer, and the second dye-containing recording layer And a second reflective layer, and the region of the second dye-containing recording layer is formed by a predetermined region wider than the region of the second reflective layer.
Thereby, the film thickness of the second dye-containing recording layer can be measured by the transmission method without being obstructed by the second reflective layer.
[0018]
Further, a second substrate that is light transmissive is provided on the second reflective layer, and in the predetermined region, the second substrate and the second dye-containing recording layer are directly or light transmissive. It is preferable that they are in contact with each other (claim 5).
[0019]
The substrate is disk-shaped, and the predetermined area is preferably provided on the inner peripheral side and / or the outer peripheral side of the substrate.
The method for measuring a film thickness of an optical recording medium according to the present invention (Claim 7) is the method for measuring a film thickness of an optical recording medium according to any one of Claims 1 to 6, wherein the dye-containing recording layer is formed. Then, the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method.
[0020]
The method for controlling the film thickness of an optical recording medium according to the present invention (Claim 8) is the method for controlling the film thickness of an optical recording medium according to any one of Claims 1 to 6, wherein the dye-containing recording layer is formed. After that, the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method, and the film thickness of the dye-containing recording layer to be subsequently laminated is controlled based on the film thickness measurement information It is said.
[0021]
The method for producing an optical recording medium of the present invention (Claim 9) is the method for producing an optical recording medium according to any one of Claims 1 to 6, wherein the dye-containing recording layer is formed, Measuring the film thickness of the dye-containing recording layer in the predetermined region by a transmission method, and controlling the film thickness of the dye-containing recording layer formed thereafter based on the film thickness measurement information. It is a feature.
[0022]
An optical recording medium film thickness measuring apparatus according to the present invention (Claim 10) is the optical recording medium film thickness measuring apparatus according to any one of Claims 1 to 6, wherein the dye-containing recording layer is formed. Then, the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method.
An optical recording medium film thickness control device of the present invention (Claim 11) is the optical recording medium film thickness control device according to any one of Claims 1 to 6, wherein the dye-containing recording layer is formed. After that, the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method, and the film thickness of the dye-containing recording layer formed thereafter is controlled based on the film thickness measurement information It is said.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, two types of optical recording media having different laminated structures will be described.
[A] First embodiment
[A-1] Configuration of optical recording medium
FIG. 1 is a schematic cross-sectional view showing an optical recording medium (type 1) according to this embodiment.
[0024]
The type 1 optical recording medium according to this embodiment includes a first recording layer containing a dye (containing a first dye) on a disk-shaped transparent (light transmissive) first substrate (first substrate) 1. Recording layer 2, translucent reflective layer (hereinafter referred to as semitransparent reflective layer; first reflective layer) 3, intermediate resin layer (intermediate layer) 4, second recording layer containing a dye (second dye-containing recording) Layer) 5, a reflective layer (second reflective layer) 6, an adhesive layer 7, and a second substrate (second substrate) 8 in this order. The light beam is irradiated from the first substrate 1 side, and recording / reproduction is performed.
[0025]
In the present invention, “light transmission (or transparency)” means light transmission (referred to as λ1 light transmission) with respect to the wavelength of light used in film thickness measurement by a transmission method (which will be described later), It means two light transmissivities, ie, a light transmissivity (referred to as λ2 light transmissivity) with respect to the wavelength of light used when recording / reproducing on a recording medium. Further, if the wavelength of the film thickness measuring light and the wavelength of the recording / reproducing light are 50% or more, preferably 60% or more, it can be said that the film is substantially light transmissive.
[0026]
Concavities and convexities are formed on the first substrate 1 and the intermediate resin layer 4, respectively, and constitute recording tracks. The recording track may be a convex portion or a concave portion, but in general, the recording track 11 on the first substrate 1 is constituted by a convex portion with respect to the incident direction of light, and the recording track 12 on the intermediate resin layer 4 is also the recording track 12. In many cases, a convex portion is formed with respect to the incident direction of light. In addition, it may have uneven pits as necessary. Unless otherwise specified, in the present invention, the unevenness is defined with respect to the incident direction of light used for recording / reproducing.
[0027]
Next, each layer will be described.
(1) About the first substrate 1
The first substrate 1 needs to have both λ1 light transmittance and λ2 light transmittance, and preferably has excellent optical characteristics such as a low birefringence. Moreover, it is desirable to be excellent in moldability such as easy injection molding. Furthermore, it is desirable that the hygroscopicity is small because warpage and the like can be reduced.
[0028]
Furthermore, it is desirable to provide shape stability so that the optical recording medium has a certain degree of rigidity. However, as long as the second substrate 8 has sufficient shape stability, the first substrate 1 may not have high shape stability.
Examples of such materials include those made of resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like. Can be used. Or what provided the resin layer which consists of radiation curable resins, such as photocurable resin, on base | substrates, such as glass, can be used.
[0029]
Polycarbonate is preferable from the viewpoints of high productivity such as optical characteristics and moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoint of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.
The first substrate 1 is preferably thin, and usually the thickness is preferably 2 mm or less, more preferably 1 mm or less. As the distance between the objective lens and the recording layer is shorter and the substrate is thinner, the coma aberration tends to be smaller, and the recording density is easily increased. However, in order to obtain sufficient optical properties, hygroscopicity, moldability, and shape stability, a certain amount of thickness is required, and is usually preferably 10 μm or more, more preferably 30 μm or more.
[0030]
In the present optical recording medium, it is desirable to appropriately adjust the distance between the objective lens and both recording layers in order to perform good recording and reproduction on both the first recording layer 2 and the second recording layer 5. For example, it is preferable to set the focal point of the objective lens at a substantially middle point between the two recording layers because the both recording layers can be easily accessed.
This will be specifically described. In the single-sided DVD-R system, the distance between the objective lens and the recording layer is adjusted to be optimum when the substrate thickness is 0.6 mm.
[0031]
Therefore, in the case of single-layer DVD-R compatibility in this layer structure, the thickness of the first substrate 1 may be a thickness obtained by subtracting one half of the thickness of the intermediate resin layer 4 from 0.6 mm. Most preferred. At this time, the substantially middle point between both recording layers is about 0.6 mm, and it is easy to apply focus servo to both recording layers.
When there are other layers such as a buffer layer and a protective layer between the second recording layer 5 and the translucent reflective layer 3, the thickness of these layers and the intermediate resin layer 4 is 2 from the thickness of 0.6 mm. Most preferably, the thickness is reduced by a factor of one.
[0032]
The first substrate 1 is provided with irregularities in a spiral shape or a concentric shape to form grooves and lands. Normally, information is recorded / reproduced in / from the first recording layer 2 using such grooves and / or lands as recording tracks. In the case of a so-called DVD-R disc in which recording / 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 2 is usually formed by coating. It is thick and suitable for recording and playback.
[0033]
In the present optical recording medium, it is preferable that the groove portion of the first substrate 1, that is, the convex portion with respect to the light incident direction is the recording track 11. Here, a recessed part and a convex part say the recessed part and convex part with respect to the incident direction of light, respectively. Usually, the groove width is about 50 to 500 nm, and the groove depth is about 10 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, it may have uneven pits such as land prepits as necessary.
[0034]
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.
[0035]
(2) About the first recording layer 2
The first recording layer 2 needs to have higher sensitivity than the recording layer used for an optical recording medium usually used for CD-R, single-sided DVD-R, and the like. In the present optical recording medium, the power of the incident light beam is divided into two by the presence of the semi-transparent reflective layer 3 and the like, and is divided into the recording of the first recording layer 2 and the recording of the second recording layer 5, so about half In order to record at a high power, the sensitivity needs to be particularly high.
[0036]
In order to realize good recording / reproducing characteristics, it is desirable that the dye has a low heat generation and a high refractive index.
Further, in the combination of the first recording layer 2 and the translucent reflective layer 3, it is desirable that the reflection, transmission and absorption of light be in an appropriate range. The recording sensitivity can be increased and the thermal interference during recording can be reduced.
[0037]
Examples of such organic dye materials include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, Examples include azulenium dyes, metal-containing azo dyes, and metal-containing indoaniline dyes.
[0038]
Among the above-mentioned various organic dyes, metal-containing azo dyes are preferable because of excellent recording sensitivity and durability and light resistance. In particular, the following general formula (I) or (II)
[0039]
[Chemical 1]

[0040]
(Ring A ¹ And A ² Are nitrogen-containing aromatic heterocycles each independently having a substituent, and ring B ¹ And B ² Are each independently an aromatic ring optionally having a substituent. X is a C1-C6 alkyl group substituted with at least two fluorine atoms. ) Is preferred.
The organic dye used in the recording layer of the present optical recording medium is preferably a dye compound having a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 to 900 nm and suitable for recording with a blue to near microwave laser. . Usually, a near infrared laser having a wavelength of about 770 to 830 nm used for a CD-R, a red laser having a wavelength of about 620 to 690 nm used for a DVD-R, or a so-called blue laser having a wavelength of 410 nm or 515 nm, etc. A dye suitable for recording is more preferable.
[0041]
One kind of dye may be used, or two or more kinds of the same kind or different kinds may be used in combination. Furthermore, it is also possible to use an optical recording medium corresponding to recording with laser light in a plurality of wavelength regions by using a combination of dyes suitable for recording in each of the recording light with the plurality of wavelengths.
[0042]
The recording layer is also a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone, etc.) as a singlet oxygen quencher to improve the stability and light resistance of the recording layer. In order to improve the recording sensitivity, a recording sensitivity improving agent such as a metal compound may be contained. Here, the metal compound refers to a compound in which a metal such as a transition metal is contained in the compound in the form of atoms, ions, clusters, etc., for example, an ethylenediamine complex, an azomethine complex, a phenylhydroxyamine complex, a phenanthroline complex, Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex and porphyrin complex can be mentioned. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.
[0043]
Furthermore, a binder, a leveling agent, an antifoaming agent and the like can be used in combination in the recording layer of the optical recording medium, if necessary. Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.
[0044]
The film thickness of the recording layer varies depending on the recording method and the like, and is not particularly limited. However, in order to obtain a sufficient degree of modulation, it is usually preferably 5 nm or more, more preferably 10 nm or more, Especially preferably, it is 20 nm or more. However, in the present optical recording medium, since it is not necessary to be too thick in order to transmit light moderately, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less. The film thickness of the recording layer is usually different between the groove part and the land part, but in this optical recording medium, the film thickness of the recording layer is the film thickness in the groove part of the substrate.
[0045]
Examples of the method for forming the recording layer include vacuum film forming methods, sputtering methods, doctor blade methods, cast methods, spin coating methods, dipping methods, and the like, but from the viewpoint of mass productivity and cost, A spin coating method is preferred. From the viewpoint that a recording layer having a uniform thickness can be obtained, the vacuum vapor deposition method is preferable to the coating method.
In the case of film formation by spin coating, the rotation speed is preferably 10 to 15000 rpm, and after spin coating, treatment such as heating or application to solvent vapor may be performed.
[0046]
The coating solvent for forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method, or a dipping method may be any solvent that does not attack the substrate and is not particularly limited. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; perfluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Examples of the solvent include hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.
[0047]
In the case of the vacuum vapor deposition method, for example, an organic dye and recording layer components such as various additives as necessary are put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is filled with an appropriate vacuum pump. ^-2 -10 ^-Five After evacuating to about Pa, the crucible is heated to evaporate the recording layer components and vapor deposited on the substrate placed facing the crucible to form the recording layer.
[0048]
(3) About translucent reflective layer 3
The translucent reflective layer 3 needs to absorb recording / reproducing light, have a light transmittance of 40% or more, and have an appropriate light reflectance. For example, an appropriate transmittance can be provided by providing a thin metal with high reflectivity. Moreover, it is desirable that there is some degree of corrosion resistance. Further, it is desirable that the first recording layer 2 be blocked by the seepage of the upper layer (here, the intermediate resin layer 4) of the translucent reflective layer 3 so as not to be affected.
[0049]
In order to ensure high transmittance, the thickness of the translucent reflective layer 3 is usually preferably 50 nm or less. More preferably, it is 30 nm or less. More preferably, it is 20 nm or less. However, since the first recording layer 2 is not affected by the upper layer of the translucent reflective layer 3, a certain thickness is required, and usually 3 nm or more. More preferably, it is 5 nm or more.
[0050]
As the material of the translucent reflective layer 3, a material having a moderately high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf , V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and rare earth metals and semi-metals It is possible to use a metal alone or as an alloy. Among these, Au, Al, and Ag have high reflectivity and are suitable as materials for the translucent reflective layer 3. In addition to these as main components, other components may be included.
[0051]
Among these, those containing Ag as a main component are particularly preferable from the viewpoint of low cost and high reflectance. Here, the main component means one having a content of 50% or more.
The translucent reflective layer 3 is thin, and if the crystal grains of the film are large, it causes reproduction noise. Therefore, it is preferable to use a material with small crystal grains. Since pure silver tends to have large crystal grains, Ag is preferably used as an alloy.
[0052]
Among these, it is preferable to contain 0.1 to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au, and rare earth metals. When two or more of Ti, Zn, Cu, Pd, Au, and rare earth metal are included, each may be 0.1 to 15 atomic%, but the total of these is preferably 0.1 to 15 atomic%. .
[0053]
A particularly preferable alloy composition contains 0.1 to 15 atomic% of at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au, containing Ag as a main component, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Of the rare earth metals, neodymium is particularly preferred. Specifically, AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, and the like.
[0054]
As the translucent reflective layer 3, a layer made only of Au is suitable because it has small crystal grains and is excellent in corrosion resistance. However, it is more expensive than Ag alloy.
It is also possible to use a layer made of Si as the translucent reflective layer 3.
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.
[0055]
Examples of the method for forming the translucent reflective layer 3 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. Further, between the first substrate 1 and the first recording layer 2 and / or between the first recording layer 2 and the translucent reflective layer 3, an improvement in reflectance, an improvement in recording characteristics, an improvement in adhesion, etc. For this purpose, a known inorganic or organic intermediate layer or adhesive layer may be provided.
[0056]
(4) About the intermediate resin layer 4
The intermediate resin layer 4 needs to have both light transmission properties of λ1 light transmission and λ2 light transmission, and it is necessary that grooves and pits can be formed by unevenness. Further, it is preferable that the adhesive strength is high and the shrinkage rate at the time of curing and bonding is small, the shape stability of the medium is high. The intermediate resin layer 4 is preferably made of a material that does not damage the second recording layer 5. However, since the intermediate resin layer 4 is usually made of a resin, it is easily compatible with the second recording layer 5. In order to prevent this and prevent damage, it is desirable to provide a buffer layer described later between the two layers.
[0057]
Furthermore, the intermediate resin layer 4 is preferably made of a material that does not damage the translucent reflective layer 3. However, in order to suppress damage, a buffer layer described later can be provided between both layers.
[0058]
In the present optical recording medium, it is preferable to control the film thickness of the intermediate resin layer 4 accurately. The film thickness of the intermediate resin layer 4 is usually preferably 5 μm or more. In order to separately apply focus servo to the two recording layers, it is necessary to have a certain distance between the two recording layers. Although it depends on the focus servo mechanism, it is usually required to be 5 μm or more, preferably 10 μm or more. In general, the higher the numerical aperture of the objective lens, the smaller the distance tends to be. However, if it is too thick, it takes time to adjust the focus servo to the two recording layers, and the moving distance of the objective lens becomes long, which is not preferable. Moreover, since there are problems such as requiring time for curing and lowering productivity, the thickness is usually preferably 100 μm or less.
[0059]
The intermediate resin layer 4 is provided with irregularities in a spiral shape or concentric shape to form grooves and lands. Normally, information is recorded / reproduced in / from the second recording layer 5 using such grooves and / or lands as recording tracks. Usually, since the second recording layer 5 is formed by coating, it becomes thick at the groove and is suitable for recording and reproduction. In this optical recording medium, it is preferable that the groove of the intermediate resin layer 4, that is, the convex portion with respect to the light incident direction is the recording track 12. Here, a recessed part and a convex part say the recessed part and convex part with respect to the incident direction of light, respectively. Usually, the groove width is about 50 to 500 nm, and the groove depth is about 10 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, it may have uneven pits such as land prepits as necessary.
[0060]
From the viewpoint of cost, such irregularities are preferably produced by transferring and curing from a resin stamper having irregularities to a curable resin such as a photocurable resin. Hereinafter, such a method may be referred to as a 2P method (Photo Polymerization method).
Examples of the material of the intermediate resin layer 4 include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin (including a delayed curable type), and the like.
[0061]
A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent to prepare a coating solution, coating it, 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, and then applying the coating solution and curing it by irradiating with ultraviolet light. There are various types of ultraviolet curable resins, and any one can be used as long as it has λ1 light transmittance and λ2 light transmittance. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.
[0062]
As a coating method, a method such as a spin coating method or a casting method is used as in the recording layer, and among these, the spin coating method is preferable. Alternatively, a resin having a high viscosity can be formed by screen printing or the like. It is preferable to use an ultraviolet curable resin that is liquid at 20 to 40 ° C. because it can be applied without using a solvent. The viscosity is preferably adjusted to 20 to 1000 mPa · s.
[0063]
As the ultraviolet curable adhesive, there are a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, both of which can be used.
As the radical ultraviolet curable adhesive, all known compositions can be used, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, monofunctional (meth) acrylate or polyfunctional (meth) acrylate can be used as the polymerizable monomer component. These can be used alone or in combination of two or more. Here, in the present invention, acrylate and methacrylate are collectively referred to as (meth) acrylate.
[0064]
Examples of polymerizable monomers that can be used in the present optical recording medium include the following. Examples of the monofunctional (meth) acrylate include methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, Nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone modified tetrahydrofurfuryl, isobornyl , (Meth) acrylate having a group such as dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like.
[0065]
Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. Di (meth) such as neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of acrylate, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, neopentyl glycol Diol di (meth) acrylate obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A, triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane Di or tri (meth) acrylate, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) Acrylate, poly (meth) acrylate of dipentaerythritol, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkylated phosphoric acid (meth) acrylate, etc. It is.
[0066]
Moreover, what can be used together with the polymerizable monomer includes polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate and the like as polymerizable oligomers.
Furthermore, as the photopolymerization initiator used in the present optical recording medium, any known one that can cure an ultraviolet curable compound represented by a polymerizable oligomer and / or a polymerizable monomer can be used. As the photopolymerization initiator, a molecular cleavage type or a hydrogen abstraction type is suitable for the optical recording medium.
[0067]
Examples of such include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- ( 4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, etc. are preferably used, and other molecular cleavage types 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Propan-1-one and -Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one or the like may be used in combination, and further a hydrogen abstraction type photopolymerization initiator, benzophenone, 4-phenylbenzophenone, isophthalphenone 4-benzoyl-4′-methyl-diphenyl sulfide and the like can be used in combination.
[0068]
Examples of sensitizers for photopolymerization initiators include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzyl. An amine that does not cause an addition reaction with the polymerizable component, such as an amine and 4,4′-bis (diethylamino) benzophenone, can also be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that are excellent in solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.
[0069]
Further, as the cationic ultraviolet curable adhesive, all known compositions can be used, and an epoxy resin containing a cationic polymerization type photoinitiator corresponds to this. Examples of cationic polymerization type photoinitiators include sulfonium salts, iodonium salts, and diazonium salts.
[0070]
An example of an iodonium salt is as follows. Diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate, bis (dodecylphenyl) iodonium hexafluoroantimonate Bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium hexafluorophosphate, 4-methylphenyl-4 -(1-Methylethyl) phenyliodonium hexafluoroa Chimoneto, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrakis (pentafluorophenyl) borate, and the like.
[0071]
The epoxy resin can be any of various types such as bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. It doesn't matter.
As the epoxy resin, it is preferable to use an epoxy resin having a low free chlorine and chlorine ion content so as not to damage the reflective layer. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.
[0072]
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 addition, in order to use the near-ultraviolet region and the visible region of the ultraviolet light source more effectively, a known photosensitizer can be used in combination. Examples of the photosensitizer at this time include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, and acetophenone.
[0073]
In addition, UV curable adhesives may contain other additives as necessary, such as thermal polymerization inhibitors, antioxidants typified by hindered phenols, hindered amines, phosphites, plasticizers and epoxy silanes, mercapto. Silane coupling agents represented by silane, (meth) acrylic silane and the like can also be blended for the purpose of improving various properties. These are selected from those having excellent solubility in ultraviolet curable compounds and those that do not impair ultraviolet transparency.
[0074]
(5) About the second recording layer 5
The second recording layer 5 needs to have higher sensitivity than the recording layer used for an optical recording medium usually used for a CD-R, a single-sided DVD-R, or the like. In the present optical recording medium, the power of the incident light beam is divided into two by the presence of the semi-transparent reflective layer 3 and the like, and is divided into the recording of the first recording layer 2 and the recording of the second recording layer 5, so about half In order to record at a high power, the sensitivity needs to be particularly high.
[0075]
In order to realize good recording / reproducing characteristics, it is desirable that the dye has a low heat generation and a high refractive index.
Further, in the combination of the second recording layer 5 and the reflective layer 6, it is desirable that the reflection and absorption of light be in an appropriate range. The recording sensitivity can be increased and the thermal interference during recording can be reduced.
[0076]
Since the material of the second recording layer 5, the film forming method, and the like are described in substantially the same manner as in the first recording layer 2, only different points will be described.
The film thickness of the second recording layer 5 is not particularly limited because it varies depending on the recording method and the like. However, in order to obtain a sufficient degree of modulation, it is usually preferably 10 nm or more, more preferably 30 nm or more. And particularly preferably 50 nm or more. However, since it is not necessary to be too thick in order to obtain an appropriate reflectance, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less.
The materials used for the first recording layer 2 and the second recording layer 5 may be the same or different.
[0077]
(6) About the reflective layer 6
The reflective layer 6 needs to have a high reflectance. Moreover, it is desirable that it is highly durable.
In order to ensure high reflectivity, the thickness of the reflective layer 6 is usually preferably 20 nm or more. More preferably, it is 30 nm or more. More preferably, it is 50 nm or more. However, in order to increase the recording sensitivity, it is preferable to be thin to some extent, and it is usually set to 400 nm or less. More preferably, it is set to 300 nm or less.
[0078]
As the material of the reflective layer 6, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, and Pd are used alone or as an alloy. It is possible. Among these, Au, Al, and Ag have high reflectivity and are suitable as materials for the reflective layer 6. In addition to these as main components, the following components may be included as other components. Examples of other components include Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, Te, Pb Mention may be made of metals and metalloids such as Po, Sn, Bi and rare earth metals.
[0079]
Among them, those containing Ag as a main component are particularly preferred because they are low in cost, easily exhibit high reflectivity, and when a print receiving layer described later is provided, a white and beautiful ground color can be obtained. Here, the main component means one having a content of 50% or more.
In order for the reflective layer 6 to ensure high durability (high corrosion resistance), Ag is preferably used as an alloy rather than pure silver.
[0080]
Among these, it is preferable to contain 0.1 to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au, and rare earth metals. When two or more of Ti, Zn, Cu, Pd, Au, and rare earth metal are included, each may be 0.1 to 15 atomic%, but the total of these is preferably 0.1 to 15 atomic%. .
[0081]
A particularly preferable alloy composition contains 0.1 to 15 atomic% of at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au, containing Ag as a main component, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Of the rare earth metals, neodymium is particularly preferred. Specifically, AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, and the like.
[0082]
As the reflective layer 6, a layer made only of Au is preferable because of its high durability (high corrosion resistance). However, it is more expensive than Ag alloy.
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as the reflective layer 6.
Examples of the method for forming the reflective layer 6 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided above and below the reflective layer 6 in order to improve reflectivity, improve recording characteristics, and improve adhesion.
[0083]
(7) About adhesive layer 7
The adhesive layer 7 does not need to have λ1 light transmittance and λ2 light transmittance. However, it is preferable that the adhesive strength is high and the shrinkage rate at the time of curing and bonding is small, the shape stability of the medium is high.
The adhesive layer 7 is preferably made of a material that does not damage the reflective layer 6. However, a known inorganic or organic protective layer may be provided between both layers in order to suppress damage.
[0084]
In the present optical recording medium, the film thickness of the adhesive layer 7 is usually preferably 2 μm or more. In order to obtain a predetermined adhesive strength, a certain film thickness is required. More preferably, it is 5 μm or more. However, in order to make the optical recording medium as thin as possible, and there is a problem that it takes time for curing and productivity is lowered.
The material of the adhesive layer 7 can be the same as the material of the intermediate resin layer 4, and a pressure-sensitive double-sided tape or the like can also be used. The adhesive layer 7 can be formed by sandwiching and pressing a pressure-sensitive double-sided tape between the reflective layer 6 and the second substrate 8.
[0085]
(8) About the second substrate 8
The second substrate 8 preferably has shape stability so that the optical recording medium has a certain degree of rigidity. That is, it is preferable that mechanical stability is high and rigidity is large. Moreover, it is desirable that the adhesiveness with the adhesive layer 7 is high.
As described above, when the first substrate 1 does not have sufficient shape stability, the second substrate 8 needs to have particularly high shape stability. In this respect, it is desirable that the hygroscopicity is small. However, the second substrate 8 does not need to be transparent (that is, it does not need to have λ1 light transmittance and λ2 light transmittance). The second substrate 8 may be a mirror substrate, and it is not necessary to form irregularities, so that the transferability by injection molding is not necessarily good.
[0086]
As such a material, the same material as that which can be used for the first substrate 1 can be used. For example, an Al alloy substrate such as an Al—Mg alloy containing Al as a main component, or an Mg alloy as a main component, for example. An Mg alloy substrate such as an Mg—Zn alloy, a substrate made of any of silicon, titanium, and ceramics, a substrate that combines them, and the like can be used.
[0087]
Polycarbonate is preferred from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoint of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.
In order to give the optical recording medium sufficient rigidity, the second substrate 8 is preferably thick to some extent, and the thickness is preferably 0.3 mm or more. However, the thinner one is advantageous for thinning the recording / reproducing apparatus, and it is preferably 3 mm or less. More preferably, it is 1.5 mm or less.
[0088]
The second substrate 8 may be a mirror substrate having no irregularities, but is preferably manufactured by injection molding from the viewpoint of ease of production.
As an example of a preferable combination of the first substrate 1 and the second substrate 8, the first substrate 1 and the second substrate 8 are made of the same material and have the same thickness. Since the rigidity is equal and balanced, it is preferable that the medium is difficult to be deformed against environmental changes. In this case, it is preferable that the degree and direction of deformation when the environment changes are the same for both substrates.
[0089]
As an example of another preferable combination, the first substrate 1 is as thin as about 0.1 mm, and the second substrate 8 is as thick as about 1.1 mm. The objective lens is preferable because it easily approaches the recording layer and easily increases the recording density. At this time, the first substrate 1 may be in the form of a sheet.
[0090]
(9) Other layers
In the above laminated structure, any other layer may be sandwiched as necessary. Alternatively, any other layer may be provided on the outermost surface of the medium. Specifically, as an intermediate layer between the translucent reflective layer 3 and the intermediate resin layer 4, between the intermediate resin layer 4 and the second recording layer 5, between the reflective layer 6 and the adhesive layer 7, etc. A buffer layer may be provided.
[0091]
The buffer layer prevents the two layers from mixing and prevents compatibility. The buffer layer may also serve other functions than preventing the mixing phenomenon. Further, another intermediate layer may be interposed as required.
The material of the buffer layer must be incompatible with the second recording layer 5 and the intermediate resin layer 4 and have λ1 light transmittance and λ2 light transmittance, and known inorganic and organic materials can be used. . In view of characteristics, an inorganic material is preferably used. For example, (1) metal or semiconductor, (2) metal or semiconductor oxide, nitride, sulfide, oxysulfide, fluoride or carbide, or (3) amorphous carbon is used. Among them, a layer made of a dielectric having λ1 light transmittance and λ2 light transmittance and a very thin metal layer (including an alloy) are preferable.
[0092]
Specifically, silicon oxide, particularly silicon dioxide, oxides such as zinc oxide, cerium oxide, yttrium oxide; sulfides such as zinc sulfide and yttrium sulfide; nitrides such as silicon nitride; silicon carbide; oxide and sulfur A mixture thereof (oxysulfide); and alloys described later are suitable. Further, a mixture of about 30:70 to 90:10 (weight ratio) of silicon oxide and zinc sulfide is also suitable. A mixture of sulfur, yttrium dioxide and zinc oxide (Y ₂ O ₂ S-ZnO) is also suitable.
[0093]
As the metal or alloy, silver or one containing 0.1 to 15 atomic% of at least one element selected from the group consisting of titanium, zinc, copper, palladium, and gold, which is mainly composed of silver, is preferable. is there. Further, those containing silver as a main component and containing at least one rare earth element in an amount of 0.1 to 15 atomic% are also suitable. As this rare earth, neodymium, praseodymium, cerium and the like are suitable.
[0094]
In addition, a resin layer may be used as long as it does not dissolve the dye in the recording layer when the buffer layer is produced. In particular, a polymer film that can be produced by vacuum deposition or CVD is useful.
The thickness of the buffer layer is preferably 2 nm or more, more preferably 5 nm or more. If the thickness of the buffer layer is excessively thin, there is a possibility that the prevention of the above mixing phenomenon will be insufficient. However, it is preferably 2000 nm or less, more preferably 500 nm or less. If the buffer layer is excessively thick, it is not only necessary for preventing mixing but also may reduce light transmittance. In the case of a layer made of an inorganic material, it takes a long time to form a film, and the productivity may be lowered or the film stress may be increased. In particular, in the case of a metal, about 20 nm or less is preferable because the light transmittance is excessively lowered.
[0095]
A protective layer may be provided to protect the recording layer and the reflective layer. The material of the protective layer needs to have λ1 light transmittance and λ2 light transmittance, but 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. Examples of inorganic substances include silicon oxide, silicon nitride, and MgF. ₂ , SnO ₂ Etc.
[0096]
A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent to prepare a coating solution, and applying and drying the coating solution. The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiation with UV light. As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.
[0097]
As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 to 100 μm, but in the present optical recording medium, 3 to 50 μm is preferable.
[0098]
Furthermore, the above-mentioned optical recording medium may be provided with a print receiving layer that can be written (printed) on a surface other than the recording / reproducing light incident surface by various printers such as ink jet and thermal transfer, or various writing tools, if necessary. May be provided.
Alternatively, two optical recording media having a main layer structure and two first recording layers 1 may be bonded to form a larger capacity medium having four recording layers.
[0099]
[A-2] Manufacturing method of optical recording medium
Next, a method for manufacturing the type 1 optical recording medium according to the present embodiment will be described with reference to FIG. FIG. 2 is a process diagram for explaining the present manufacturing method.
First, as shown in FIG. 2 (a), a first substrate 1 having grooves, lands, and pre-pits on its surface is formed by injection molding or 2P method based on a stamper.
[0100]
Next, as shown in FIG. 2B, a coating solution in which at least an organic dye is dissolved in a solvent is applied to the surface of the first substrate 1 on the uneven side by spin coating or the like, and the first recording layer 2 is formed. Form a film. At this time, as shown in FIG. 2B, a predetermined area 30a in which the first recording layer 2 is not formed is provided on the inner peripheral side of the disk (first substrate 1). Further, the width W of the predetermined area 30a ₁ Is formed from the inner peripheral edge of the first substrate 1 to a thickness of, for example, 0.1 mm to 5 mm, preferably about 1 mm.
[0101]
Thereafter, as shown in FIG. 2C, the outer peripheral side of the first substrate 1 is washed to remove the first recording layer 2, and a predetermined region 30b where the first substrate 1 is exposed is formed. Further, the width W of the predetermined region 30b at this time ₂ In the same manner as in the above-described region 30a, the distance from the outer peripheral end of the first substrate 1 is, for example, 0.1 mm to 5 mm, preferably about 1 mm. The predetermined regions 30a and 30b are formed for the purpose of easily measuring the film thickness of the second recording layer 5 when measuring the film thickness described later.
[0102]
After the first recording layer 2 is formed, as shown in FIG. 2D, a mask is put on the inner peripheral side region 30a and the outer peripheral side region 30b of the first substrate 1, and Ag alloy or the like is sputtered or evaporated. Thus, the translucent reflective layer 3 is formed on the first recording layer 2.
Thereafter, as shown in FIG. 2E, an ultraviolet curable resin or the like is applied to the entire surface of the first substrate 1 including the predetermined regions 30a and 30b by spin coating or the like. At this time, the ultraviolet curable resin (which will later become the intermediate resin layer 4) is in direct contact with the first substrate 1 in the predetermined regions 30a and 30b of the first substrate 1.
[0103]
Next, unevenness is formed on the surface of the ultraviolet curable resin using a mold. As the mold, it is preferable to use a stamper 15 made of a resin as shown in FIG. 2F from the viewpoint of productivity, cost, and the like.
The resin stamper 15 only needs to have sufficient peelability with respect to the resin to be the intermediate resin layer 4. Although it is not necessary to be transparent, it is desirable that the moldability is good and the shape stability is good. From the viewpoint of productivity and cost, the resin stamper 15 is desirably usable for a plurality of times of transfer. It is desirable that recycling after use is possible.
[0104]
The resin stamper 15 may have one or more separate layers 17 on the resin substrate 16 as shown in FIG. 2 (f), or may be composed of only the resin substrate 16. From the viewpoint of property and cost.
First, a resin substrate 16 is produced by injection molding, 2P method, or the like using a metal stamper having negatives and concavities opposite to the resin stamper 15 described above (negative).
[0105]
The resin substrate 16 does not need to be transparent, but desirably has good moldability and good shape stability. Examples of such materials include those made of resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, and epoxy resins.
[0106]
The thickness of the resin substrate 16 is preferably 0.5 mm or more from the viewpoint of shape stability and ease of handling. The upper limit of the thickness is not particularly limited, but usually 3 mm or less is sufficient.
If the resin stamper 15 is configured to have one or more separate layers 17 on the resin substrate 16, the resin substrate 16 needs to be a resin having high adhesion to the separate layer 17, and other high productivity such as moldability. Polycarbonate is preferable from the viewpoints of properties, cost, low hygroscopicity, and shape stability.
[0107]
It is desirable that the separate layer 17 has low adhesion with the resin constituting the intermediate resin layer 4 and high peelability. In addition, it is desirable that unevenness that faithfully reflects the unevenness of the resin substrate 16 is formed when the film is formed.
The material of the separate layer 17 is preferably a metal or an alloy from the viewpoint of releasability from the resin of the intermediate resin layer 4, and usually a metal selected from Ag, Au, Cu, Pt and Pd or an alloy thereof is used.
[0108]
The thickness of the separate layer 17 is required to be a certain thickness in order to ensure the peelability from the intermediate resin layer 4, and is preferably 2 nm or more. On the other hand, in order to faithfully reflect the unevenness of the substrate, it is desirable that it is not too thick, and usually 200 nm or less is preferable.
If the resin stamper 15 includes only the resin substrate 16, it is desirable that the resin substrate 16 has low adhesion and high peelability with the resin constituting the intermediate resin layer 4. In addition, amorphous polyolefin is preferred from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability.
[0109]
Therefore, after applying an ultraviolet curable resin or the like on the first substrate 1 by spin coating or the like, the resin stamper 15 as described above is placed, and the unevenness is transferred to the ultraviolet curable resin. At this time, it is performed while adjusting the film thickness of the ultraviolet curable resin to be within a predetermined range.
In this state, the ultraviolet curable resin is cured by irradiating ultraviolet rays from the first substrate 1 side, and when sufficiently cured, the resin stamper 15 is peeled off. As shown in FIG. The intermediate resin layer 4 having Alternatively, ultraviolet rays can be irradiated from the side of the medium. In any case, it is necessary to prevent the first recording layer 1 from being damaged by the ultraviolet rays.
[0110]
Subsequently, as shown in FIG. 2 (h), the surface of the intermediate resin layer 4 (that is, the region of the first recording layer 2 and the translucent reflective layer 3) is applied by spin coating or the like with at least an organic dye dissolved in a solvent. The second recording layer 5 is formed by coating in a region wider than the predetermined region.
Then, as shown in FIG. 2 (i), the reflective layer 6 is formed on the second recording layer 5 by sputtering and vapor-depositing an Ag alloy or the like.
[0111]
Thereafter, as shown in FIG. 2 (j), a mirror substrate as the second substrate 8 obtained by injection molding of polycarbonate is bonded to the reflective layer 6 via the adhesive layer 7. Thereby, the manufacture of the optical recording medium is completed.
The adhesive layer 7 may be opaque or may have a slightly rough surface, and a delayed curing adhesive can be used without any problem. An adhesive layer 7 can be formed by applying an adhesive onto the reflective layer 6 by screen printing or the like, irradiating ultraviolet rays, and placing and pressing the second substrate 8. Alternatively, the adhesive layer 7 can be formed by pressing a pressure-sensitive double-sided tape between the reflective layer 6 and the second substrate 8.
[0112]
[A-3] Film thickness measuring method and film thickness control method of optical recording medium
In the type 1 optical recording medium according to this embodiment, the film thicknesses of the first recording layer 2 and the second recording layer 5 can be measured using a known transmission method. In manufacturing an optical recording medium having good characteristics, it is important to more accurately control the film thicknesses of the first recording layer 2 and the second recording layer 5.
[0113]
As for the first recording layer 2, as shown in FIG. 2 (b), after forming the first recording layer 2 on the first substrate 1, from the upper surface side of the first recording layer 2 or from the lower surface side of the first substrate 1. When the transmittance is measured by irradiating light (for example, red laser, He—Ne laser, He—Cd laser, etc., preferably visible light), the transmittance of the reflective layer or the like on the upper and lower sides of the first recording layer 2 is measured. Since there is no low layer, the film thickness of the first recording layer 2 can be easily measured.
[0114]
As for the second recording layer 5, as shown in FIG. 2 (h), after the second recording layer 5 is formed on the intermediate resin layer 4, the upper surface of the second recording layer 5 or the lower surface of the first substrate 1 is used. The film thickness can be measured by irradiating light from the side and measuring the transmittance. At this time, the light is irradiated to the position of the arrow shown in FIG. 2 (h), that is, the predetermined region 30a and / or 30b. To do. In the range of the predetermined regions 30a and 30b, only the intermediate resin layer 4 having the λ1 light transmittance and the first substrate 1 exist in the lower layer of the second recording layer 5, and there is no low transmittance layer such as a reflective layer. Therefore, the thickness of the second recording layer 5 can be easily measured.
[0115]
As described above, the region of the second recording layer 5 is formed by a predetermined region wider than the region of the first recording layer 2 and the region of the semitransparent reflective layer 3, so that the first recording layer 2 and the semitransparent reflective layer are formed. 3, the film thickness of the second recording layer 5 can be measured by the transmission method.
In the predetermined regions 30a and 30b, even if there is a buffer layer or a protective layer between the intermediate resin layer 4 and the first substrate 1 or between the second recording layer 5 and the intermediate resin layer 4, these Since the buffer layer and the protective layer have λ1 light transmittance, the film thickness of the second recording layer 5 can be easily measured in the same manner as described above.
[0116]
Further, by measuring the film thickness at a plurality of points in the diameter direction of the first substrate 1, it is possible to obtain a more accurate film thickness.
In the present embodiment, the predetermined area is provided on both the inner and outer peripheral sides of the first substrate 1. However, the predetermined area may be provided only on the inner peripheral side or only on the outer peripheral side.
[0117]
The film thickness measurement is automatically performed by a film thickness measurement device (not shown) in the manufacturing apparatus for manufacturing the optical recording medium (that is, the manufacturing process). This is fed back to a film thickness controller (not shown) that controls the film thicknesses of the first recording layer 2 and the second recording layer 5.
[0118]
That is, for example, when the film thickness of the first recording layer 2 is measured by the film thickness measuring device, the film thickness information is transmitted to the film thickness control device, and the film thickness control device performs the first measurement based on the film thickness information. The coating amount (or concentration) of the coating liquid for forming one recording layer 2, temperature, humidity, time for coating the coating liquid, the number of rotations of the first substrate 1 when coating the coating liquid, and the maximum rotation of the first substrate 1 The time until reaching the number is adjusted, and the film thickness of the first recording layer 2 of the next disk is controlled to an appropriate film thickness. Further, the film thickness control of the second recording layer 5 of the next disk can be performed in the same manner as the film thickness control of the first recording layer 2. Of course, based on the film thickness information of the first recording layer 2, the film thickness of the second recording layer 5 stacked above the first recording layer 2 is controlled, or more than two recording layers are provided. When the recording layer is laminated further above the second recording layer 5, the thickness of the recording layer can be controlled.
[0119]
[B] Second embodiment
[B-1] Configuration of optical recording medium
FIG. 3 is a schematic cross-sectional view showing an optical recording medium (type 2) according to this embodiment.
The type 2 optical recording medium according to this embodiment includes a first recording layer containing a dye (containing a first dye) on a disk-shaped transparent (light transmissive) first substrate (first substrate) 21. Recording layer) 22, translucent reflective layer (hereinafter referred to as semitransparent reflective layer; first reflective layer) 23, transparent adhesive layer 24, buffer layer 28, and second recording layer containing a dye (second dye-containing recording). Layer) 25, a reflective layer (second reflective layer) 26, and a disk-shaped transparent second substrate (second substrate) 27 in this order. The light beam is irradiated from the first substrate 21 side, and recording / reproduction is performed.
[0120]
In the present invention, “light transmission (or transparency)” means light transmission (referred to as λ1 light transmission) with respect to the wavelength of light used in film thickness measurement by a transmission method (which will be described later), It means two light transmissivities, ie, a light transmissivity (referred to as λ2 light transmissivity) with respect to the wavelength of light used when recording / reproducing on a recording medium. Further, if the wavelength of the film thickness measuring light and the wavelength of the recording / reproducing light are 50% or more, preferably 60% or more, it can be said that the film is substantially light transmissive.
[0121]
Concavities and convexities are formed on the first substrate 21 and the second substrate 27, respectively, and constitute recording tracks. The recording track may be either a convex portion or a concave portion, but the recording track 31 on the first substrate 21 is preferably constituted by a convex portion with respect to the incident direction of light, and the recording track 32 on the second substrate 27. Is preferably constituted by a recess with respect to the incident direction of light. In addition, it may have uneven pits as necessary. Unless otherwise specified, in this embodiment, the unevenness is defined with respect to the incident direction of light used for recording / reproducing.
[0122]
Next, each layer will be described.
The first substrate 21, the first recording layer 22, the translucent reflective layer 23, the second recording layer 25, and the reflective layer 26 according to the present embodiment are respectively the first substrate 1 and the first recording layer 2 according to the first embodiment. The translucent reflective layer 3, the second recording layer 5, and the reflective layer 6 have substantially the same configuration.
Further, the transparent adhesive layer 24 as an intermediate layer needs to have at least λ2 light transmittance. And it is the structure substantially the same as the structure of the intermediate | middle resin layer 4 in 1st Embodiment except that it is not necessary to form a groove | channel and a pit by an unevenness | corrugation. In the present optical recording medium, the grooves and pits are formed on the second substrate 27 described later.
[0123]
Furthermore, the buffer layer 28 as an intermediate layer has substantially the same configuration as the buffer layer described in the first embodiment. This buffer layer may be formed as necessary.
The second substrate 27 needs to have at least λ1 light transparency, and preferably has shape stability so that the optical recording medium has a certain degree of rigidity. That is, it is preferable that mechanical stability is high and rigidity is large.
[0124]
Examples of such materials include those made of resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like. Can be used.
[0125]
Concavities and convexities are provided on the second substrate 27 in a spiral shape or concentric shape to form grooves and lands. Normally, information is recorded / reproduced in / from the second recording layer 25 using such grooves and / or lands as recording tracks. Usually, since the second recording layer 25 is formed by coating, it becomes thick at the groove and is suitable for recording and reproduction. In the present optical recording medium, it is preferable that the groove portion of the second substrate 27, that is, the concave portion with respect to the light incident direction is the recording track 32. Here, a recessed part and a convex part say the recessed part and convex part with respect to the incident direction of light, respectively. Usually, the groove width is about 50 to 500 nm, and the groove depth is about 10 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, it may have uneven pits such as land prepits as necessary.
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.
Moreover, in order to protect the recording layer and the reflective layer, the protective layer described in the first embodiment may be provided. The material of the protective layer needs to have λ1 light transmittance and λ2 light transmittance, but is not particularly limited as long as it protects the recording layer and the reflective layer from external force.
[0126]
[B-2] Manufacturing method of optical recording medium
Next, a method for manufacturing a type 2 optical recording medium according to the present embodiment will be described with reference to FIGS. FIG. 4 is a process diagram for explaining the manufacturing method.
In the present optical recording medium, a laminated structure (first constituent) A having a first recording layer 22 containing a dye and a translucent reflective layer 23 in this order is formed on a first substrate 21, and the second substrate 27, a laminated structure (second component) B having a reflective layer 26, a second recording layer 25 containing a dye, and a buffer layer 28 in this order is prepared, and then both laminated structures A and B are mutually connected to the recording layer 22. , 25 are attached to each other through the transparent adhesive layer 24 so as to be inward (facing each other).
[0127]
First, as shown in FIG. 4A, the first substrate 21 having grooves, lands, and pre-pits formed on the surface with irregularities is produced by injection molding, 2P method, or the like.
Next, as shown in FIG. 4B, a coating solution in which at least an organic dye is dissolved in a solvent is applied to the surface of the first substrate 21 on the uneven side by spin coating or the like, and the first recording layer 22 is formed. Form a film.
[0128]
After forming the first recording layer 22, as shown in FIG. 4C, a translucent reflective layer 23 is formed on the first recording layer 22 by sputtering or vapor-depositing an Ag alloy or the like to form a laminated structure. A.
On the other hand, as shown in FIG. 4 (d), a second substrate 27 having grooves and lands and pits formed on the surface with irregularities is produced by injection molding or 2P method.
[0129]
Then, as shown in FIG. 4E, the reflective layer 26 is formed on the surface of the second substrate 27 on the uneven side by sputtering or vapor-depositing an Ag alloy or the like. At this time, as shown in FIG. 4E, predetermined areas 40a and 40b where the reflective layer 26 is not formed are provided by covering the inner periphery and the outer periphery of the disk (second substrate 27) with a mask or the like. . Further, the width W of the predetermined area 40a _Ten For example, 0.1 mm to 5 mm, preferably about 1 mm from the inner peripheral end of the second substrate 27, and the width W of the predetermined region 40b. ₂₀ For example, 0.1 mm to 5 mm, preferably about 1 mm from the outer peripheral edge of the second substrate 27. The predetermined regions 40a and 40b are formed for the purpose of easily measuring the film thickness of the second recording layer 5 during film thickness measurement described later.
[0130]
After forming the reflective layer 26, as shown in FIG. 4F, a coating solution in which at least an organic dye is dissolved in a solvent is applied to a region wider than the reflective layer 26 by spin coating or the like. Two recording layers 25 are formed. At this time, the second recording layer 25 is in direct contact with the second substrate 27 in the predetermined regions 40 a and 40 b of the second substrate 27.
Next, as shown in FIG. 4G, a buffer layer 28 is formed by sputtering a dielectric or the like to form a laminated structure B.
[0131]
Then, as shown in FIG. 4 (h), an adhesive such as an ultraviolet curable resin that becomes the transparent adhesive layer 24 is applied on the laminated structure A, and then the laminated structure B is placed and bonded by high-speed rotation, pressing, or the like. Spread the agent all over. At this time, it is performed while adjusting the film thickness of the transparent adhesive layer 24 to be within a predetermined range. Thereafter, the type 2 optical recording medium can be manufactured by irradiating ultraviolet rays from the lower surface side of the first substrate 21 through the translucent reflective layer 23 and curing and adhering them. Alternatively, ultraviolet rays can be irradiated from the side of the medium. In any case, care must be taken so that the first recording layer 22 is not damaged by the ultraviolet rays.
[0132]
Moreover, an adhesive layer can also be formed by pressing a pressure-sensitive double-sided tape between the laminated structures A and B. Alternatively, the adhesive layer can be formed by using a delayed-curing type adhesive, applying the adhesive on the laminated structure A by screen printing or the like, irradiating ultraviolet rays, and placing and pressing the laminated structure B. However, the delayed curable adhesive is usually opaque.
[0133]
[B-3] Film thickness measuring method and film thickness control method of optical recording medium
In the type 2 optical recording medium according to the present embodiment, the film thicknesses of the first recording layer 22 and the second recording layer 25 can be measured using a known transmission method, as in the first embodiment.
As for the first recording layer 22, as shown in FIG. 4B, after the first recording layer 22 is formed on the first substrate 21, the upper surface side of the first recording layer 22 or the lower surface side of the first substrate 21 is used. When the transmittance of the first recording layer 22 is measured by irradiation with light (for example, a red laser, a He—Ne laser, a He—Cd laser, etc., preferably visible light), a reflective layer is formed on the upper and lower sides of the first recording layer 22. Since there is no layer with low transmittance such as, the film thickness of the first recording layer 22 can be easily measured.
[0134]
As for the second recording layer 25, as shown in FIG. 4 (f), after the second recording layer 25 is formed on the reflective layer 26, from the upper surface side of the second recording layer 25 or the lower surface side of the second substrate 27. The film thickness can be measured by irradiating light from the second recording layer 25 and measuring the transmittance of the second recording layer 25. At this time, the light is irradiated at the position indicated by the arrow shown in FIG. Irradiate 40b. In the range of the predetermined areas 40a and 40b, only the second substrate 27 having λ1 light transmittance exists in the lower layer of the second recording layer 25 shown in FIG. Since there is nothing, the film thickness of the second recording layer 25 can be easily measured.
[0135]
As described above, the region of the second recording layer 25 is formed wider than the region of the second reflective layer 26 by a predetermined region, so that the film of the second recording layer 26 is not obstructed by the second reflective layer 26. Thickness can be measured by transmission method.
In the predetermined areas 40a and 40b, even if a buffer layer or a protective layer exists between the second substrate 27 and the second recording layer 25, the buffer layer or the protective layer has λ1 light transmittance. Therefore, the film thickness of the second recording layer 25 can be easily measured as described above.
[0136]
Further, by measuring the film thickness at a plurality of points in the diameter direction of the second substrate 27, it becomes possible to obtain a more accurate film thickness.
In the present embodiment, the predetermined area is provided on both the inner peripheral side and the outer peripheral side of the second substrate 27. However, the predetermined area may be provided only on the inner peripheral side or only on the outer peripheral side.
[0137]
The film thickness measurement is automatically performed by a film thickness measurement device (not shown) in the manufacturing apparatus for manufacturing the optical recording medium (that is, the manufacturing process). This is fed back to a film thickness controller (not shown) that controls the film thicknesses of the first recording layer 22 and the second recording layer 25.
That is, for example, when the film thickness of the first recording layer 22 is measured by the film thickness measurement device, the film thickness information is transmitted to the film thickness control device. The coating amount (or concentration) of the coating liquid for forming one recording layer 22, the temperature, the humidity, the time for coating the coating liquid, the number of rotations of the first substrate 21 when coating the coating liquid, and the maximum rotation of the first substrate 21. The time until reaching the number is adjusted, and the film thickness of the first recording layer 22 of the next disk is controlled to an appropriate film thickness. Further, the film thickness control of the second recording layer 25 of the next disk can be performed in the same manner as the film thickness control of the first recording layer 22.
[0138]
[C] Other
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
[0139]
For example, in the first and second embodiments, the optical recording medium having two recording layers has been described, but the optical recording medium may have three or more recording layers. In this case, it is preferable to manufacture the optical recording medium of type 1 according to the first embodiment. For example, as shown in FIG. 5, a translucent reflective layer 3 ′, an intermediate resin layer 4 ′, and a third recording layer 5 ′ are provided between the second recording layer 5 and the reflective layer 6 of the optical recording medium according to the first embodiment. A laminated structure with an intervening layer. Further, predetermined areas 30a and 30b for measuring the film thickness of the second recording layer 5 are provided, and predetermined areas 30a 'and 30b' for measuring the film thickness of the third recording layer 5 'are provided. At this time, the film thickness of the third recording layer 5 'can be easily measured by forming the predetermined regions 30a' and 30b 'so that the widths thereof are smaller than the widths of the predetermined regions 30a and 30b, respectively. As described above, even in an optical recording medium having three or more recording layers, by providing the predetermined area as described above, the thickness of each recording layer can be easily measured in the manufacturing process by the transmission method. It becomes.
[0140]
In the first and second embodiments, the substrate incident type optical disc that records and reproduces information by irradiating the laser beam from the substrate side has been described. However, the laminated structure including the substrate / reflective layer / recording layer / protective layer is used. The present invention can also be applied to a film surface incident type optical disc that records and reproduces information by irradiating a laser beam from the protective layer side (that is, the film surface side).
[0141]
【The invention's effect】
As described above in detail, according to the optical recording medium of the present invention described in claim 1, even in a laminated structure in which a reflective layer is provided between a light-transmitting substrate and a dye-containing recording layer, the dye Since the area of the contained recording layer is formed in an area wider than the area of the reflective layer by a predetermined area, the film thickness of the dye-containing recording layer can be easily measured by the transmission method in this predetermined area.
[0142]
According to the optical recording medium of the present invention, the region of the second dye-containing recording layer is formed by a predetermined region wider than the region of the first dye-containing recording layer and the region of the first reflective layer. Therefore, the film thickness of the second dye-containing recording layer can be easily measured by the transmission method in this predetermined region.
According to the optical recording medium of the present invention, the first substrate and the intermediate layer are in contact with each other directly or through a light-transmitting layer in a predetermined region. Thus, the film thickness of the second dye-containing recording layer can be easily measured.
[0143]
According to the optical recording medium of the present invention, the region of the second dye-containing recording layer is formed wider than the region of the second reflective layer by a predetermined region. The film thickness of the second dye-containing recording layer can be easily measured by the method.
According to the optical recording medium of the present invention, the second substrate and the second dye-containing recording layer are in contact with each other directly or through a light-transmitting layer in the predetermined region. In the region, the film thickness of the second dye-containing recording layer can be easily measured by the transmission method.
[0144]
According to the optical recording medium of the present invention described in claim 6, since the predetermined region is provided on the inner peripheral side and / or the outer peripheral side of the substrate, by measuring the film thickness at a plurality of points in the diameter direction, It is possible to obtain a more accurate film thickness.
According to the method for measuring the film thickness of the optical recording medium of the present invention described in claim 7, the film thickness of the dye-containing recording layer can be easily measured by a transmission method in a predetermined region.
[0145]
According to the method for controlling the film thickness of the optical recording medium of the present invention described in claim 8, the film thickness of the dye-containing recording layer is measured by a transmission method in a predetermined region, and then formed based on the film thickness measurement information. Therefore, more accurate film thickness control is possible.
According to the method for producing an optical recording medium of the present invention according to claim 9, the film thickness of the dye-containing recording layer is measured by a transmission method in a predetermined region, and the dye formed thereafter is based on the film thickness measurement information. Since the step of controlling the film thickness of the contained recording layer is included, the film thickness can be controlled more accurately, and an optical recording medium having good quality characteristics can be manufactured.
[0146]
According to the optical recording medium film thickness measuring apparatus of the present invention, the film thickness of the dye-containing recording layer can be easily measured by a transmission method in a predetermined region.
According to the film thickness control apparatus for an optical recording medium of the present invention as set forth in claim 11, the film thickness of the dye-containing recording layer is measured by a transmission method in a predetermined area, and then formed based on this film thickness measurement information. Therefore, more accurate film thickness control is possible.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an optical recording medium (type 1) as a first embodiment of the present invention.
FIG. 2 is a process diagram showing a method of manufacturing an optical recording medium (type 1) as a first embodiment of the present invention.
FIG. 3 is a schematic diagram showing an optical recording medium (type 2) as a second embodiment of the present invention.
FIG. 4 is a process diagram showing a method of manufacturing an optical recording medium (type 2) as a second embodiment of the present invention.
FIG. 5 is a schematic diagram showing a modification of the optical recording medium (type 1) as the first embodiment of the invention.
FIG. 6 is a schematic diagram showing an example of a conventional optical recording medium.
[Explanation of symbols]
1,21 First substrate (first substrate)
2,22 First recording layer (first dye-containing recording layer)
3,23 Translucent reflective layer (first reflective layer)
4 Intermediate resin layer (intermediate layer)
5,25 Second recording layer (second dye-containing recording layer)
6,26 Reflective layer (second reflective layer)
7 Adhesive layer
8, 27 Second substrate (second substrate)
28 Buffer layer (intermediate layer)
11, 12, 31 Recording track consisting of convex portions
24 Transparent adhesive layer (intermediate layer)
32 Recording track consisting of recesses
30a, 30b, 30a ', 30b', 40a, 40b predetermined area

Claims (11)

A reflective layer is provided between the light-transmitting substrate and the dye-containing recording layer on which information can be optically recorded;
An optical recording medium, wherein a region of the dye-containing recording layer is formed by a predetermined region wider than a region of the reflective layer. A light-transmissive first substrate;
A first dye-containing recording layer on which information can be optically recorded on the first substrate;
A first reflective layer on the first dye-containing recording layer;
A second dye-containing recording layer on which information can be optically recorded on the first reflective layer;
Providing a second reflective layer on the second dye-containing recording layer;
An optical recording medium characterized in that the area of the second dye-containing recording layer is formed by a predetermined area wider than the area of the first dye-containing recording layer and the area of the first reflective layer . A light transmissive intermediate layer is provided between the first reflective layer and the second dye-containing recording layer;
3. The optical recording medium according to claim 2, wherein in the predetermined region, the first substrate and the intermediate layer are in contact with each other directly or through a light-transmitting layer. A light-transmissive first substrate;
A first dye-containing recording layer on which information can be optically recorded on the first substrate;
A first reflective layer on the first dye-containing recording layer;
A second dye-containing recording layer on which information can be optically recorded on the first reflective layer;
Providing a second reflective layer on the second dye-containing recording layer;
An optical recording medium, wherein a region of the second dye-containing recording layer is formed by a predetermined region wider than a region of the second reflective layer. Providing a light transmissive second substrate on the second reflective layer;
5. The optical recording medium according to claim 4, wherein the second substrate and the second dye-containing recording layer are in contact with each other directly or through a light-transmitting layer in the predetermined region. 6. The optical recording according to claim 1, wherein the substrate is disk-shaped, and the predetermined area is provided on an inner peripheral side and / or an outer peripheral side of the substrate. Medium. It is the film thickness measuring method of the optical recording medium of any one of Claims 1-6,
A method for measuring a film thickness of an optical recording medium, comprising: measuring the film thickness of the dye-containing recording layer in the predetermined region by a transmission method after the dye-containing recording layer is formed. It is the film thickness control method of the optical recording medium of any one of Claims 1-6,
After the dye-containing recording layer is formed, the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method, and the film of the dye-containing recording layer that is subsequently laminated based on the film thickness measurement information A method for controlling a film thickness of an optical recording medium, wherein the thickness is controlled. A method for producing an optical recording medium according to any one of claims 1 to 6,
After the dye-containing recording layer is formed, the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method, and the film of the dye-containing recording layer formed thereafter based on the film thickness measurement information A method for producing an optical recording medium, comprising a step of controlling the thickness. It is a film thickness measuring device of an optical recording medium given in any 1 paragraph of Claims 1-6,
An apparatus for measuring a film thickness of an optical recording medium, wherein the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method after the dye-containing recording layer is formed. A film thickness control device for an optical recording medium according to any one of claims 1 to 6,
After the dye-containing recording layer is formed, the film thickness of the dye-containing recording layer in the predetermined region is measured by a transmission method, and the film of the dye-containing recording layer formed thereafter based on the film thickness measurement information An apparatus for controlling a film thickness of an optical recording medium, characterized by controlling a thickness.

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