JP4050993B2 - Optical recording medium, optical recording medium thickness measurement method, film thickness control method, and manufacturing method - Google Patents

Description

【００３９】
（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。
【００４０】
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。
【００４１】
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。
【００４２】
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。
【００４３】
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。
【００４４】
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。
【００４５】
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。
【００４６】
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。
【００４７】
（３）半透明反射層３について
半透明反射層３は、ある程度の光透過率を持つ反射層である。つまり、記録再生光の吸収が小さく、光透過率が少なくとも４０％以上あり、かつ適度な光反射率（通常、３０％以上）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。
【００４８】
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２５ｎｍ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。
【００４９】
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。
【００５０】
なかでもＡｇを主成分としているものはコストが安い点、反射率が高い点から特に好ましい。ここで主成分とは含有率が５０％以上のものをいう。
半透明反射層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。
【００５１】
中でもＡｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属よりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有することが好ましい。Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属のうち２種以上含む場合は、各々０．１〜１５原子％でもかまわないが、それらの合計が０．１〜１５原子％であることが好ましい。
【００５２】
特に好ましい合金組成は、Ａｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕよりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有し、かつ少なくとも１種の希土類元素を０．１〜１５原子％含有するものである。希土類金属の中では、ネオジウムが特に好ましい。具体的には、ＡｇＰｄＣｕ、ＡｇＣｕＡｕ、ＡｇＣｕＡｕＮｄ、ＡｇＣｕＮｄなどである。
【００５３】
半透明反射層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。
【００５４】
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。
【００５５】
（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。
【００５６】
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。
【００５７】
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。
【００５８】
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２００〜５００ｎｍ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。
【００５９】
このような凹凸は、コストの観点から、凹凸を持つ樹脂スタンパ等から光硬化性樹脂などの硬化性樹脂に転写、硬化させて製造するのが好ましい。以下、このような方法を２Ｐ法（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。
【００６０】
熱可塑性樹脂、熱硬化性樹脂などは適当な溶剤に溶解して塗布液を調製し、これを塗布し、乾燥（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。
【００６１】
塗布方法としては、記録層と同様にスピンコート法やキャスト法等の塗布法等の方法が用いられるが、この中でもスピンコート法が好ましい。或いは、粘度の高い樹脂はスクリーン印刷等によっても塗布形成できる。紫外線硬化性樹脂は、生産性を２０〜４０℃において液状であるものを用いると、溶媒を用いることなく塗布でき好ましい。また、粘度は２０〜１０００ｍＰａ・ｓとなるように調製するのが好ましい。
【００６２】
さて、紫外線硬化性接着剤としては、ラジカル系紫外線硬化性接着剤とカチオン系紫外線硬化性接着剤があるが、いずれも使用可能である。
ラジカル系紫外線硬化性接着剤としては、公知の全ての組成物を用いることができ、紫外線硬化性化合物と光重合開始剤を必須成分として含む組成物が用いられる。紫外線硬化性化合物としては、単官能（メタ）アクリレートや多官能（メタ）アクリレートを重合性モノマー成分として用いることができる。これらは、各々、単独または２種類以上併用して用いることができる。ここで、本発明では、アクリレートとメタアクリレートとを併せて（メタ）アクリレートと称する。
【００６３】
本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。
【００６４】
また、多官能（メタ）アクリレートとしては例えば、１，３−ブチレングリコール、１，４−ブタンジオール、１，５−ペンタンジオール、３−メチル−１，５−ペンタンジオール、１，６−ヘキサンジオール、ネオペンチルグリコール、１，８−オクタンジオール、１，９−ノナンジオール、トリシクロデカンジメタノール、エチレングリコール、ポリエチレングリコール、プロピレングリコール、ジプロピレングリコール、トリプロピレングリコール、ポリプロピレングリコール等のジ（メタ）アクリレート、トリス（２−ヒドロキシエチル）イソシアヌレートのジ（メタ）アクリレート、ネオペンチルグリコール１モルに４モル以上のエチレンオキサイドもしくはプロピレンオキサイドを付加して得たジオールのジ（メタ）アクリレート、ビスフェノールＡ１モルに２モルのエチレンオキサイドもしくはプロピレンオキサイドを付加して得たジオールのジ（メタ）アクリレート、トリメチロールプロパン１モルに３モル以上のエチレンオキサイドもしくはプロピレンオキサイドを付加して得たトリオールのジまたはトリ（メタ）アクリレート、ビスフェノールＡ１モルに４モル以上のエチレンオキサイドもしくはプロピレンオキサイドを付加して得たジオールのジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールトリ（メタ）アクリレート、ジペンタエリスリトールのポリ（メタ）アクリレート、エチレンオキサイド変性リン酸（メタ）アクリレート、エチレンオキサイド変性アルキル化リン酸（メタ）アクリレート等が挙げられる。
【００６５】
また、重合性モノマーと同時に併用できるものとしては、重合性オリゴマーとしてポリエステル（メタ）アクリレート、ポリエーテル（メタ）アクリレート、エポキシ（メタ）アクリレート、ウレタン（メタ）アクリレート等がある。
更に、本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。
【００６６】
このような例としては、ベンゾインイソブチルエーテル、２，４−ジエチルチオキサントン、２−イソプロピルチオキサントン、ベンジル、２，４，６−トリメチルベンゾイルジフェニルフォスフィンオキシド、２−ベンジル−２−ジメチルアミノ−１−（４−モルフォリノフェニル）−ブタン−１−オン、ビス（２，６−ジメトキシベンゾイル）−２，４，４−トリメチルペンチルフォスフィンオキシド等が好適に用いられ、さらにこれら以外の分子開裂型のものとして、１−ヒドロキシシクロヘキシルフェニルケトン、ベンゾインエチルエーテル、ベンジルジメチルケタール、２−ヒドロキシ−２−メチル−１−フェニルプロパン−１−オン、１−（４−イソプロピルフェニル）−２−ヒドロキシ−２−メチルプロパン−１−オンおよび２−メチル−１−（４−メチルチオフェニル）−２−モルフォリノプロパン−１−オン等を併用しても良いし、さらに水素引き抜き型光重合開始剤である、ベンゾフェノン、４−フェニルベンゾフェノン、イソフタルフェノン、４−ベンゾイル−４'−メチル−ジフェニルスルフィド等も併用できる。
【００６７】
また光重合開始剤に対する増感剤として例えば、トリメチルアミン、メチルジメタノールアミン、トリエタノールアミン、ｐ−ジエチルアミノアセトフェノン、ｐ−ジメチルアミノ安息香酸エチル、ｐ−ジメチルアミノ安息香酸イソアミル、Ｎ，Ｎ−ジメチルベンジルアミンおよび４，４'−ビス（ジエチルアミノ）ベンゾフェノン等の、前述重合性成分と付加反応を起こさないアミン類を併用することもできる。もちろん、上記光重合開始剤や増感剤は、紫外線硬化性化合物への溶解性に優れ、紫外線透過性を阻害しないものを選択して用いることが好ましい。
【００６８】
また、カチオン系紫外線硬化性接着剤としては公知のすべての組成物を用いることができ、カチオン重合型の光開始剤を含むエポキシ樹脂がこれに該当する。カチオン重合型の光開始剤としては、スルホニウム塩、ヨードニウム塩およびジアゾニウム塩等がある。
ヨードニウム塩の１例を示すと以下の通りである。ジフェニルヨードニウム ヘキサフルオロホスフェード、ジフェニルヨードニウム ヘキサフルオロアンチモネート、ジフェニルヨードニウム テトラフルオロボレート、ジフェニルヨードニウム テトラキス（ペンタフルオロフェニル）ボレート、ビス（ドデシルフェニル）ヨードニウム ヘキサフルオロホスフェート、ビス（ドデシルフェニル）ヨードニウム ヘキサフルオロアンチモネート、ビス（ドデシルフェニル）ヨードニウム テトラフルオロボレート、ビス（ドデシルフェニル）ヨードニウムテトラキス（ペンタフルオロフェニル）ボレート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム ヘキサフルオロホスフェート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム ヘキサフルオロアンチモネート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム テトラフルオロボレート、４−メチルフェニル−４−（１−メチルエチル）フェニルヨードニウム テトラキス（ペンタフルオロフェニル）ボレート、などが挙げられる。
【００６９】
エポキシ樹脂は、ビスフェノールＡ−エピクロールヒドリン型、脂環式エポキシ、長鎖脂肪族型、臭素化エポキシ樹脂、グリシジルエステル型、グリシジルエーテル型、複素環式系等種々のものがいずれであってもかまわない。
エポキシ樹脂としては、反射層にダメージを与えないよう、遊離したフリーの塩素および塩素イオン含有率が少ないものを用いるのが好ましい。塩素の量が１重量％以下が好ましく、より好ましくは０．５重量％以下である。
【００７０】
カチオン型紫外線硬化性樹脂１００重量部当たりのカチオン重合型光開始剤の割合は通常、０．１〜２０重量部であり、好ましくは０．２〜５重量部である。なお、紫外線光源の波長域の近紫外領域や可視領域の波長をより有効に利用するため、公知の光増感剤を併用することができる。この際の光増感剤としては、例えばアントラセン、フェノチアジン、ベンジルメチルケタール、ベンゾフェノン、アセトフェノン等が挙げられる。
【００７１】
また、紫外線硬化性接着剤には、必要に応じてさらにその他の添加剤として、熱重合禁止剤、ヒンダードフェノール、ヒンダードアミン、ホスファイト等に代表される酸化防止剤、可塑剤およびエポキシシラン、メルカプトシラン、（メタ）アクリルシラン等に代表されるシランカップリング剤等を、各種特性を改良する目的で配合することもできる。これらは、紫外線硬化性化合物への溶解性に優れたもの、紫外線透過性を阻害しないものを選択して用いる。
【００７２】
（５）第２記録層５について
第２記録層５は、通常、片面型記録媒体（ＣＤ−ＲやＤＶＤ−Ｒ）等に用いる記録層より高感度である。本光記録媒体においては、入射した光ビームのパワーが第１記録層２や半透明反射層３の存在等で減少するため、約半分程度のパワーで記録するために、特に感度が高い必要があるのである。
【００７３】
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。
【００７４】
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。
【００７５】
（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、生産のタクトタイムを短くしコストを下げるためにはある程度薄いことが好ましく、通常４００ｎｍ以下とする。より好ましくは３００ｎｍ以下とする。
【００７６】
反射層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。
【００７７】
中でもＡｇを主成分としているものはコストが安い点、高反射率が出やすい点、更に後で述べる印刷受容層を設ける場合には地色が白く美しいものが得られる点等から特に好ましい。ここで主成分とは含有率が５０％以上のものをいう。
反射層６は高耐久性（高耐食性）を確保するため、Ａｇは純銀よりも合金として用いるのが好ましい。
【００７８】
中でもＡｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属よりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有することが好ましい。Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕ及び希土類金属のうち２種以上含む場合は、各々０．１〜１５原子％でもかまわないが、それらの合計が０．１〜１５原子％であることが好ましい。
【００７９】
特に好ましい合金組成は、Ａｇを主成分とし、Ｔｉ、Ｚｎ、Ｃｕ、Ｐｄ、Ａｕよりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有し、かつ少なくとも１種の希土類元素を０．１〜１５原子％含有するものである。希土類金属の中では、ネオジウムが特に好ましい。具体的には、ＡｇＰｄＣｕ、ＡｇＣｕＡｕ、ＡｇＣｕＡｕＮｄ、ＡｇＣｕＮｄなどである。
【００８０】
反射層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。
【００８１】
（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。
【００８２】
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。
【００８３】
（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。
【００８４】
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。
【００８５】
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。
【００８６】
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。
【００８７】
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。
【００８８】
（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。
【００８９】
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。
【００９０】
具体的には、酸化珪素、特に二酸化珪素や、酸化亜鉛、酸化セリウム、酸化イットリウム等の酸化物；硫化亜鉛、硫化イットリウムなどの硫化物；窒化珪素などの窒化物；炭化珪素；酸化物とイオウとの混合物（酸硫化物）；および後述の合金などが好適である。また、酸化珪素と硫化亜鉛との３０：７０〜９０：１０程度（重量比）の混合物も好適である。また、イオウと二酸化イットリウムと酸化亜鉛との混合物（Ｙ₂Ｏ₂Ｓ−ＺｎＯ）も好適である。
【００９１】
金属や合金としては、銀、又は銀を主成分とし更にチタン、亜鉛、銅、パラジウム、及び金よりなる群から選ばれる少なくとも１種の元素を０．１〜１５原子％含有するものが好適である。また、銀を主成分とし、少なくとも１種の希土類元素を０．１〜１５原子％含有するものも好適である。この希土類としては、ネオジウム、プラセオジウム、セリウム等が好適である。
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。
【００９２】
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。
【００９３】
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。
【００９４】
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。
【００９５】
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。
【００９６】
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。
また、本層構成の応用例として、記録層を３層以上有する媒体も可能である。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。
【００９７】
（Ａ−２）タイプ１の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。
【００９８】
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Ｗ₁を設けるようにする。また、この所定領域Ｗ₁を、第１基板１の内周端部から例えば０．１ｍｍ以上、好ましくは５ｍｍ以上、より好ましくは１０ｍｍ以上である。但し、２０ｍｍ以下、好ましくは１８ｍｍ以下程度で形成するのが良い。
【００９９】
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Ｗ₂を形成する。また、このときの所定領域Ｗ₂を、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Ｗ₁，Ｗ₂は、後述する膜厚測定時において半透明反射層３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。
【０１００】
第１記録層２を成膜した後、図２（ｄ）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２上、そして、第１基板１の所定領域Ｗ₁，Ｗ₂上にも半透明反射層３を成膜する。
その後、図２（ｅ）に示すように、第１記録層２及び第１基板１の所定領域Ｗ₁，Ｗ₂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。
【０１０１】
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。
【０１０２】
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。
【０１０３】
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。
【０１０４】
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。
【０１０５】
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、Ｎｉ、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。
【０１０６】
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。
【０１０７】
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。
【０１０８】
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。
【０１０９】
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。
【０１１０】
（Ａ−３）タイプ１の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半透明反射層３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、特に半透明反射層３の膜厚制御をより正確に行なうことが重要である。
【０１１１】
上述したように、本実施形態に係る光記録媒体の製造方法では、半透明反射層３を、第１記録層２が成膜された領域よりも所定領域だけ広い領域に成膜している。
つまり、例えば図３（ａ）に示すように、半透明反射層３は、第１基板１の内周側において、第１記録層２上だけでなく、第１記録層２が成膜されていない第１基板１上にも形成されている。また、図３（ｂ）に示すように、第１基板１の外周側においても、第１記録層２上だけでなく、第１記録層２が成膜されていない第１基板１上にも形成されている。
【０１１２】
なお、内周側及び外周側のそれぞれにおいて、第１基板１と半透明反射層３とが接触している所定領域をＷ₁′及びＷ₂′としたとき、Ｗ₁′≦Ｗ₁、Ｗ₂′≦Ｗ₂である。また、ここでは、半透明反射層３と第１基板１とが接触する所定領域Ｗ₁′及びＷ₂′を、所定領域Ｗ₁及びＷ₂よりも小さく形成しているが、半透明反射層３を内周端部及び外周端部まで（即ち、Ｗ₁＝Ｗ₁′、Ｗ₂＝Ｗ₂′となるように）形成してもよい。
【０１１３】
そして、半透明反射層３の膜厚を測定する場合、上記の所定領域Ｗ₁′及びＷ₂′において行なう。つまり、所定領域Ｗ₁′及びＷ₂′において、半透明反射層３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、半透明反射層３と第１基板１との間には、λ１光透過性を有する第１基板１しか存在しておらず、第１記録層１等はなんら存在していないので、半透明反射層３のみの膜厚を容易且つ正確に測定することが可能である。
【０１１４】
このように、半透明反射層３の領域が、第１記録層２の領域よりも所定領域Ｗ₁′，Ｗ₂′だけ広く形成されることで、第１記録層２に邪魔されることがないので、半透明反射層３の膜厚を透過法で正確に測定できる。
これにより、半透明反射層２３の膜厚を適正な厚さに厳密に管理することができるので、良好なジッタ特性を得ることができ、光記録媒体の記録や再生時のエラーをより低減することができる。つまり、良質な光記録媒体を製造することができる。
【０１１５】
なお、所定領域Ｗ₁′，Ｗ₂′において、半透明反射層３と第１基板１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、上記と同様に半透明反射層３の膜厚を容易に測定することが可能である。
また、このような膜厚測定を、例えば第１基板１の直径方向の複数点において行ない、これらの測定値の平均を得ることで、より正確な膜厚を求めることもできる。
【０１１６】
さらに、第１記録層２の膜厚は、半透明反射層３の膜厚よりも厚いので、この第１記録層２の膜厚が影響しない位置、即ち、第１記録層２からできるだけ離れた位置（所定領域Ｗ₁′内の内周側、所定領域Ｗ₂′内の外周側）で膜厚測定を行なうことが好ましい。
なお、ここでは、第１基板１の内周側及び外周側の両方に所定領域Ｗ₁′，Ｗ₂′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、半透明反射層３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。
例えば膜厚測定装置により半透明反射層３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、半透明反射層３のスパッタや蒸着等の条件（例えばスパッタを用いた場合であれば、スパッタ時間、スパッタ電圧、第１基板１とＡｇターゲットとの距離など）が調節されて、次のディスクの半透明反射層３の膜厚が適切な膜厚になるように制御される。
【０１１８】
（Ｂ−１）タイプ２の光記録媒体の構成
図４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）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。
【０１１９】
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％以上の透過性があれば実質的に光透過性であるといえる。
【０１２０】
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。
【０１２１】
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。
【０１２２】
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。
【０１２３】
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。
【０１２４】
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２００〜５００ｎｍ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。
【０１２５】
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）タイプ２の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５を用いて説明する。なお、図５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５（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５（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。なお、このとき、図５（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２２を形成しない所定領域Ｗ₁₀を設けるようにする。また、この所定領域Ｗ₁₀を、第１基板２１の内周端部から例えば０．１ｍｍ以上、好ましくは５ｍｍ以上、より好ましくは１０ｍｍ以上である。但し、２０ｍｍ以下、好ましくは１８ｍｍ以下程度で形成するのが良い。
【０１２８】
さらに、第１基板２１の外周側を洗浄して第１記録層２２を除去し、第１基板２１が露出する所定領域Ｗ₂₀を形成する。また、このときの所定領域Ｗ₂₀を、第１基板２１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Ｗ₁₀，Ｗ₂₀は、後述する膜厚測定時において半透明反射層２３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。
【０１２９】
第１記録層２２を成膜した後、図５（ｄ）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、そして、第１基板２１の所定領域Ｗ₁₀，Ｗ₂₀上にも半透明反射層２３を成膜し、積層構造Ａとする。
一方、図５（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。
【０１３０】
そして、図５（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。
その後、図５（ｆ）に示すように、反射層２６上に、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。
【０１３１】
次いで、図５（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。
そして、図５（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）タイプ２の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、上述したタイプ１の光記録媒体と同様に、公知の透過法を用いて半透明反射層２３の膜厚を測定することができる。
つまり、図３（ａ），（ｂ）に示すように、半透明反射層２３は、第１基板２１の内周側及び外周側において、第１記録層２２上だけでなく、第１記録層２２が成膜されていない第１基板２１上にも形成されている。
【０１３４】
なお、内周側及び外周側のそれぞれにおいて、第１基板２１と半透明反射層２３とが接触している所定領域をＷ₁₀′及びＷ₂₀′としたとき、Ｗ₁₀′≦Ｗ₁₀、Ｗ₂₀′≦Ｗ₂₀である。また、ここでは、半透明反射層２３と第１基板２１とが接触する所定領域Ｗ₁₀′及びＷ₂₀′を、所定領域Ｗ₁₀及びＷ₂₀よりも小さく形成しているが、半透明反射層２３を内周端部及び外周端部まで（即ち、Ｗ₁₀＝Ｗ₁₀′、Ｗ₂₀＝Ｗ₂₀′となるように）形成してもよい。
【０１３５】
そして、半透明反射層２３の膜厚を測定する場合、上記の所定領域Ｗ₁₀′及びＷ₂₀′において行なう。つまり、所定領域Ｗ₁₀′及びＷ₂₀′において、半透明反射層２３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）を照射してその透過率の測定を行なえば、半透明反射層２３と第１基板１との間には、λ１光透過性を有する第１基板２１しか存在しておらず、第１記録層２１等はなんら存在していないので、半透明反射層２３のみの膜厚を容易且つ正確に測定することが可能である。
【０１３６】
このように、本実施形態に係るタイプ２の光記録媒体においても、半透明反射層２３の領域が、第１記録層２２の領域よりも所定領域Ｗ₁₀′，Ｗ₂₀′だけ広く形成されることで、第１記録層２２に邪魔されることがないので、半透明反射層２３の膜厚を透過法で正確に測定できる。
これにより、半透明反射層２３の膜厚を適正な厚さに厳密に管理することができるので、良好なジッタ特性を得ることができ、光記録媒体の記録や再生時のエラーをより低減することができる。つまり、良質な光記録媒体を製造することができる。
【０１３７】
なお、所定領域Ｗ₁₀′，Ｗ₂₀′において、半透明反射層２３と第１基板２１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、上記と同様に半透明反射層２３の膜厚を容易に測定することが可能である。
また、このような膜厚測定を、例えば第１基板２１の直径方向の複数点において行ない、これらの測定値の平均を得ることで、より正確な膜厚を求めることもできる。
【０１３８】
さらに、第１記録層２２の膜厚は、半透明反射層２３の膜厚よりも厚いので、この第１記録層２２の膜厚が影響しない位置、即ち、第１記録層２２からできるだけ離れた位置（所定領域Ｗ₁₀′内の内周側、所定領域Ｗ₂₀′内の外周側）で膜厚測定を行なうことが好ましい。
なお、ここでは、第１基板２１の内周側及び外周側の両方に所定領域Ｗ₁₀′，Ｗ₂₀′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。
【０１３９】
また、この膜厚測定は、上述した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、半透明反射層２３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。
【０１４０】
〔２〕第２実施形態
次に、本発明の第２実施形態に係る膜厚測定方法について説明する。なお、本膜厚測定方法は、タイプ１及びタイプ２の両方の光記録媒体で用いることができる。以下では、一例としてタイプ１の光記録媒体の場合について説明する。
【０１４１】
本実施形態では、まず、図６（ａ）に示すように、第１基板１上に第１記録層２を形成した後、透過法により第１基板１及び第１記録層２の透過光量（第１の透過光量）Ｐ₁を測定する。なお、第１基板１はλ１光透過性を有するので、このとき測定される透過光量Ｐ₁はほぼ第１記録層２の透過光量として扱うことができる。
【０１４２】
そして、第１記録層２上に半透明反射層３を形成した後、透過法により第１基板１，第１記録層２，半透明反射層３の透過光量（第２の透過光量）Ｐ₂を測定する。なお、上記と同様に、第１基板１はλ１光透過性を有するので、このとき測定される透過光量Ｐ₂をほぼ第１記録層２及び半透明反射層３の透過光量として扱うことができる。
【０１４３】
次に、このようにして得られた透過光量Ｐ₁及び透過光量Ｐ₂の差Ｐ₃を求め、予め経験により求められた透過光量と膜厚との関係（マップ）から、半透明反射層３の膜厚を得る。
このように、本実施形態に係る膜厚測定方法では、第１実施形態のような所定領域Ｗ₁，Ｗ₂，Ｗ₁′，Ｗ₂′（タイプ１の光記録媒体）、あるいは、所定領域Ｗ₁₀，Ｗ₂₀，Ｗ₁₀′，Ｗ₂₀′（タイプ２の光記録媒体）を設ける構造にする必要はなく、第１記録層２の透過光量Ｐ₁と、第１記録層２及び半透明反射層３の透過光量Ｐ₂とから、半透明反射層３の膜厚を容易に求めることができる。
【０１４４】
また、このような測定を、ディスクの直径方向や円周方向の複数点において測定し、例えばこれらの測定値の平均をとることで、半透明反射層３のより正確な膜厚を求めることが可能である。
また、第１実施形態と同様に、上記の膜厚測定及び計算は、本光記録媒体を製造する製造装置内（即ち製造過程）において膜厚測定装置により自動的に行なわれ、この膜厚測定装置で測定された膜厚情報は、半透明反射層３の膜厚を制御する膜厚制御装置にフィードバックされる。
【０１４５】
さらに、本実施形態では、ディスク面内での半透明反射層３の膜厚分布もわかるため、この膜厚分布情報を膜厚制御装置にフィードバックし、半透明反射層３形成のためのスパッタ条件または蒸着条件を調節することで、より細かな膜厚制御を行なうことも可能となる。
例えば、スパッタを用いて半透明反射層３を形成する場合であって、ディスク面内での膜厚分布のムラが大きい場合には、スパッタ電圧を小さくしてスパッタ時間（スパッタしている時間）を長くするように制御する。或いは、ディスク面内での膜厚分布のムラが大きい場合に、スパッタリングガス（通常、Ａｒ等）の流量を低減するように制御する。
【０１４６】
なお、本実施形態では、測定が容易であるという理由から、透過光量を測定することで膜厚を求める方法としたが、第１記録層２や半透明反射層の光吸収率がほぼ一定であると考えれば、これらの反射光量を測定することにより間接的に透過光量を求めることも可能である。
【０１４７】
〔３〕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。
例えば、半透明反射層３（２３）の膜厚を測定する際、第１実施形態に係る膜厚測定方法と、第２実施形態に係る膜厚測定方法との両方を行なうようにしても良い。
【０１４８】
つまり、第１実施形態に係る製造方法を用い、ディスクの内周側及び外周側に所定領域を設け、この製造過程において、第１記録層２（２２）を形成した後、透過法によりこの第１記録層２（２２）の透過光量Ｐ₁を測定しておき、第１記録層２（２２）上に半透明反射層３（２３）を形成した後、第１記録層２（２２）及び半透明反射層３（２３）の透過光量Ｐ₂を測定し、半透明反射層３（２３）だけの透過光量Ｐ₃を計算することにより、半透明反射層３（２３）の膜厚を求める。一方、ディスクの内周側及び外周側の所定領域Ｗ₁′，Ｗ₂′（Ｗ₁₀′，Ｗ₂₀′）において、透過法により半透明反射層３（２３）の透過光量を測定することにより半透明反射層３（２３）の膜厚を求める。
【０１４９】
このように、第１実施形態に係る膜厚測定方法により求められた膜厚情報と、第２実施形態に係る膜厚測定方法により求められた膜厚情報及び膜厚分布情報とから、より正確な半透明反射層３（２３）の膜厚及び膜厚分布を得ることも可能となり、これらの情報を膜厚制御装置にフィードバックすることにより、より厳密な膜厚制御を行なうことが可能である。
【０１５０】
また、本発明の趣旨の範囲内で、光記録媒体の基板や各層の積層順序や製造法を変えても良い。また、上記の実施形態では、いわゆる基板面入射媒体を例に説明したが、膜面入射媒体であっても良い。
また、本発明は、記録層を３層以上有し半透明反射層を２層以上有し、片面から光を入射して記録再生するような媒体に適用し、この２層の半透明反射層の膜厚測定と膜厚制御に用いても良い。
【０１５１】
例えば、光透過性基板／第１記録層／第１半透明反射層／第１中間層／第２記録層／第２半透明反射層／第２中間層／第３記録層／反射層、といった層構成の光記録媒体においては、第１半透明反射層を第１記録層よりも広く形成するとともに、第２半透明反射層を第１記録層、第１半透明反射層、第２記録層よりも広く形成することで、両方の半透明反射層の膜厚を正確に測定することができる。
【０１５２】
あるいは、基板上に第１の記録層を形成したのち第１の透過光量を測定し、第１半透明反射層を形成したのち第２の透過光量を測定し、両者（第１の透過光量及び第２の透過光量）の差から第１半透明反射層の膜厚を求めるとともに、さらに第２記録層を形成したのち第３の透過光量を測定し、第２半透明反射層を形成したのち第４の透過光量を測定し、両者（第３の透過光量及び第４の透過光量）の差から第２半透明反射層の膜厚を求めることができる。
【０１５３】
また、上記の実施形態では、半透明反射層３（２３）を１つだけそなえる光記録媒体の場合において、この半透明反射層３（２３）の膜厚情報を、次に製造されるディスクの半透明反射層の膜厚制御に用いるようにしたが、同材質の半透明反射層を複数そなえる光記録媒体である場合には、最初に形成された半透明反射層の膜厚情報を、その後に形成される半透明反射層の膜厚制御に用いるようにしても良い。
【０１５４】
また、本発明の光記録媒体の膜厚測定方法は、相変化型媒体にも適用できるが、上記の実施形態でも説明したように、特に色素記録層を有する色素媒体に適用するとより効果が高い。
相変化型媒体では、色素媒体と同様に、半透明反射層の膜厚を厳密に管理したいという要望があるが、相変化型媒体は、通常、全ての層をスパッタリング等の真空プロセスで成膜するので、他の層の膜厚変動が小さく、本発明のような工夫が無くても、半透明反射層の膜厚を求めることが可能である。例えば、記録層，保護層，半透明反射層等の全ての層を形成した後に、全体の透過／反射光量を測定し、各層の屈折率等をもとに計算することで、間接的に半透明反射層の膜厚を求めることができる。
【０１５５】
一方、色素媒体では、色素記録層は、通常、塗布法、特にスピンコート法によって成膜される。このような塗布プロセスは真空プロセスに比べて簡便ではあるが、膜厚変動が生じやすい。従って、色素媒体では、上述したような相変化型媒体の膜厚測定方法で半透明反射層の膜厚を求めることは困難であり、本発明の膜厚測定方法がより必要とされる。
【０１５６】
また、本発明は、プロセス上、色素媒体の方が相変化型媒体よりも適用しやすい面もある。
例えば、本発明では、半透明反射層の領域を他の層の領域よりも広く形成するが、相変化型媒体では媒体の内周／外周をマスクして全ての層を一連の真空プロセスで成膜するので、半透明反射層だけを他の層よりも広く形成することや、成膜プロセスの途中で一旦取り出して透過光量を測定することは、通常行ないにくい。
【０１５７】
一方、色素媒体では、通常、色素記録層は塗布プロセスで、半透明反射層は真空プロセスで独立して成膜するので、半透明反射層だけを他の層よりも広く形成することが容易であるし、また、色素記録層形成と半透明反射層形成との間で透過光量を測定することも容易である。
【０１５８】
【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、光透過性の基板と半透明反射層との間に他の層が設けられた積層構造であっても、半透明反射層の領域が他の層の領域よりも所定領域だけ広い領域に形成されており、この所定領域では基板と半透明反射層との間には何も介在しないので、この所定領域において透過法により半透明反射層の膜厚を容易に且つ正確に測定することができる。
【０１５９】
請求項２記載の本発明の光記録媒体によれば、光透過性の基板と半透明反射層との間に色素含有記録層が設けられた積層構造であっても、半透明反射層の領域が色素含有記録層の領域よりも所定領域だけ広い領域に形成されており、この所定領域では基板と半透明反射層との間には何も介在しないので、この所定領域において透過法により半透明反射層の膜厚を容易に且つ正確に測定することができる。
【０１６０】
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、基板と半透明反射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、透過法により半透明反射層の膜厚を容易に且つ正確に測定することができる。
請求項４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。
【０１６１】
請求項５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、透過法により半透明反射層の膜厚を容易に測定できる。
請求項６記載の本発明の光記録媒体の膜厚測定方法によれば、任意の位置の膜厚を測定することができるとともに、膜厚分布も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制御方法によれば、所定領域において透過法により半透明反射層の膜厚を測定し、この膜厚測定情報に基づいて、その後に形成される半透明反射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。
【０１６２】
請求項８記載の本発明の光記録媒体の製造方法によれば、基板上に、他の層を形成し、他の層上に、他の層の領域よりも所定領域だけ広い領域に半透明反射層を形成するので、この所定領域において透過法により半透明反射層の膜厚を容易に且つ正確に測定することが可能となる。
【図面の簡単な説明】
【図１】本発明の第１実施形態に係るタイプ１の光記録媒体を示す模式図である。
【図２】本発明の第１実施形態に係るタイプ１の光記録媒体の製造方法を説明するための工程図である。
【図３】本発明の第１実施形態に係るタイプ１の光記録媒体の膜厚測定方法を説明するための図で、（ａ）はディスク内周側の膜厚測定、（ｂ）はディスク外周側の膜厚測定を示す模式図である。
【図４】本発明の第１実施形態に係るタイプ２の光記録媒体を示す模式図である。
【図５】本発明の第１実施形態に係るタイプ２の光記録媒体の製造方法を説明するための工程図である。
【図６】本発明の第２実施形態に係るタイプ１の光記録媒体の膜厚測定方法を説明するための図で、（ａ）は第１基板及び第１記録層の透過光量測定、（ｂ）は第１基板及び第１記録層及び半透明反射層の透過光量測定を示す模式図である。
【図７】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
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
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
Ｗ₁′，Ｗ₂′，Ｗ₁₀′，Ｗ₂₀′ 所定領域[0001]
BACKGROUND OF THE INVENTION
The present invention particularly relates to an optical recording medium that has a plurality of recording layers and can be reproduced and recorded by laser light from one side, and a film thickness measurement method, film thickness control method, and manufacturing method thereof.
[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 called a dye-containing recording layer) such as CD-R, DVD-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 (or 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 on the protective layer. It has 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 with or without an adhesive layer, and recording / reproduction is performed with laser light through the first transparent disk substrate. Is. 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 two recording layers from one side. For example, an optical recording medium as shown in FIG. 7 has been developed (for example, a patent). Reference 1).
[0006]
That is, as shown in FIG. 7, 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 50 by irradiation with a recording laser beam. A layer 52, a first reflective layer 53 composed of a semi-transparent reflective film capable of transmitting a part of the reproduction laser beam, and the recording laser beam and the reproduction laser beam. An intermediate layer 51, a second information recording layer 52 ′ made of an organic dye capable of optically recording information by irradiation with a recording laser beam, and a second reflecting layer 53 ′ that reflects the reproducing laser beam The second translucent substrate 50 'is laminated in this order.
[0007]
With this configuration, information can be recorded on the first information recording layer 52 and the second information recording layer 52 ′ 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.
[0008]
As a method for manufacturing an optical recording medium having such a laminated structure, for example, a first information recording layer 52, a first reflective layer 53, an intermediate layer 51, a first layer on a first light-transmitting substrate 50 are used. The second information recording layer 52 ′ and the second reflective layer 53 ′ are formed in this order, and finally the second light-transmitting substrate 50 ′ is bonded to the substrate (type 1). A first information recording layer 52 and a first reflective layer 53 are formed in this order on the optical substrate 50 to produce a first component, while a second component is formed on the second optically transparent substrate 50 '. A reflective layer 53 ′ and a second information recording layer 52 ′ are formed in this order to produce a second component, and the first reflective layer 53 and the second component of the first component are formed via the intermediate layer 51. A method of manufacturing (type 2) by adhering the second information recording layer 52 'of the component so as to face each other is conceivable.
[0009]
[Patent Document 1]
JP 11-66622 A
[0010]
[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. In particular, as described above, the first reflective layer 53 (consisting of the above-described semi-transparent reflective film) that is essential in a single-sided dual-layer medium that records and reproduces two recording layers by laser light from one side. In the reflective layer (translucent reflective layer), it is important to control the transmittance, and strict film thickness management is required.
[0011]
For example, when the film thickness of the translucent reflective layer 53 is deviated, the recording / reproduction of both the first information recording layer 52 and the second information recording layer 52 ′ is affected, and the jitter is deteriorated.
Specifically, when the film thickness of the translucent reflective layer 53 varies, the reflectivity with respect to the first information recording layer 52 changes, so that the recording power at the time of recording fluctuates and the jitter deteriorates. Similarly, the reproduction power changes during reproduction, and jitter further deteriorates.
[0012]
Further, since the transmittance with respect to the second information recording layer 52 'is also changed, the recording power and the reproducing power are changed similarly to the above, and the jitter is deteriorated. Further, in this case, since the laser light passes through the semitransparent reflection layer 53 twice in the forward and backward directions, the fluctuation of the film thickness of the semitransparent reflection layer 53 is applied to the second information recording layer 52 ′. There is a double impact on it.
[0013]
The so-called reflective layer (non-translucent reflective layer; total reflective layer) only needs to reflect incident light and does not have to consider transmittance and absorptance. Thickness control is not required.
[0014]
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.
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, part of the 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.
[0015]
However, in the above-described dual-layer optical recording medium (single-sided dual-layer medium), when an optical recording medium is manufactured by, for example, the type 1 manufacturing method, the first transparent substrate 50 and the translucent reflective layer 53 are provided. Since the first information recording layer 52 is interposed between the first information recording layer 52 and the film thickness of the translucent reflective layer 53, the thickness of the translucent reflective layer 53 is measured by the transmission method. It is difficult to accurately measure the thickness.
Also, when an optical recording medium is manufactured by the type 2 manufacturing method, it is difficult to accurately measure the film thickness of the translucent reflective layer 53 for the same reason as described above.
[0016]
Furthermore, in the optical recording medium in which another layer such as a recording layer is provided between the transparent substrate and the semitransparent reflective layer as described above, the film thickness of the semitransparent reflective layer cannot be accurately measured. The film thickness of the translucent reflective layer of the optical recording medium to be manufactured next cannot be controlled by feeding back the measurement information to the coating process.
[0017]
The present invention was devised in view of such problems, and in an optical recording medium in which a recording layer or the like is provided between a transparent substrate and a semitransparent reflective layer, the film thickness of the semitransparent reflective layer is determined by a transmission method. An object of the present invention is to provide an optical recording medium, a method for measuring the film thickness of the optical recording medium, a method for controlling the film thickness, and a method for manufacturing the optical recording medium.
[0018]
[Means for Solving the Problems]
Therefore, the optical recording medium of the present invention (Claim 1) includes another layer between the light-transmitting substrate and the semitransparent reflective layer, and the region of the semitransparent reflective layer is the same as that of the other layer. It is characterized in that it is formed by a predetermined area wider than the area.
Thereby, the film thickness of the translucent reflective layer can be measured by the transmission method without being obstructed by other layers such as a recording layer.
[0019]
The other layer preferably includes a dye-containing recording layer on which information can be optically recorded (claim 2).
In the predetermined region, it is preferable that the substrate and the translucent reflective layer are in contact with each other directly or through a light transmissive layer.
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.
[0020]
An optical recording medium film thickness measuring method according to the present invention (Claim 5) is the optical recording medium film thickness measuring method according to any one of Claims 1 to 4, wherein the film thickness is measured in the predetermined region by a transmission method. The film thickness of the translucent reflective layer is measured.
The method for measuring the thickness of an optical recording medium according to the present invention (Claim 6) is a method for measuring the thickness of an optical recording medium comprising another layer between a light-transmitting substrate and a translucent reflective layer, The relationship between the film thickness of the translucent reflective layer and the amount of transmitted light is obtained in advance, and after forming the other layer, the first transmitted light amount of the substrate and the other layer is measured by a transmission method, After forming the transparent reflective layer, the second transmitted light amount of the substrate, the other layers, and the translucent reflective layer is measured by a transmission method, and the difference between the first transmitted light amount and the second transmitted light amount is measured. The thickness of the translucent reflective layer is obtained from the above.
[0021]
The method for controlling the film thickness of an optical recording medium according to the present invention (Claim 7) is the film thickness controlling method for an optical recording medium according to any one of Claims 1 to 4, wherein the film thickness is controlled in the predetermined region by a transmission method. The film thickness of the translucent reflective layer is measured, and the film thickness of the translucent reflective layer formed thereafter is controlled based on the film thickness measurement information.
An optical recording medium manufacturing method of the present invention (Claim 8) is the optical recording medium manufacturing method according to any one of Claims 1 to 4, wherein the other layer is formed on the substrate. Then, the translucent reflective layer is formed on the other layer in a region wider than the region of the other layer by a predetermined region.
[0022]
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.
[1] First embodiment
(A-1) Configuration of type 1 optical recording medium
FIG. 1 is a schematic cross-sectional view showing an optical recording medium (type 1) according to this embodiment.
[0023]
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 translucent reflective layer) 3, intermediate resin layer (intermediate layer) 4, second recording layer containing dye (second dye-containing recording layer) 5, 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.
[0024]
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 there is a transmittance of 50% or more (preferably 60% or more) with respect to the wavelength of the film thickness measuring light and the wavelength of the recording / reproducing light, it can be said that it is substantially light transmissive.
[0025]
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.
[0026]
Next, each layer will be described.
(1) About the first substrate 1
The first substrate 1 is required 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.
[0027]
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.
[0028]
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, and more preferably 30 μm or more.
[0029]
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.
[0030]
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.
[0031]
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.
[0032]
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 200 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.
[0033]
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.
[0034]
(2) About the first recording layer 2
The first recording layer 2 usually has a sensitivity comparable to that of a recording layer used for a single-sided recording medium (for example, CD-R, DVD-R, DVD + R).
[0035]
In order to realize good recording / reproducing characteristics, it is desirable to use a dye having low heat generation and 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.
[0036]
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.
[0037]
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)
[0038]
[Chemical 1]

[0039]
(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. More preferred are dyes suitable for recording.
[0040]
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.
[0041]
In addition, the recording layer has 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.
[0042]
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.
[0043]
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.
[0044]
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.
[0045]
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.
[0046]
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.
[0047]
(3) About translucent reflective layer 3
The translucent reflective layer 3 is a reflective layer having a certain degree of light transmittance. That is, the absorption of recording / reproducing light is small, the light transmittance is at least 40% or more, and there is an appropriate light reflectance (usually 30% or more). 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.
[0048]
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 25 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.
[0049]
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.
[0050]
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.
[0051]
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%. .
[0052]
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.
[0053]
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.
[0054]
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.
[0055]
(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.
[0056]
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.
[0057]
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.
[0058]
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 200 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.
[0059]
From the viewpoint of cost, such irregularities are preferably produced by transferring and curing from a resin stamper having irregularities to a curable resin such as a photocurable resin. Hereinafter, such a method may be referred to as a 2P method (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.
[0060]
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.
[0061]
As a coating method, a method such as a spin coating method or a casting method is used as in the recording layer, and among these, the spin coating method is preferable. Alternatively, a resin having a high viscosity can be formed by screen printing or the like. It is preferable to use an ultraviolet curable resin that is liquid at 20 to 40 ° C. because it can be applied without using a solvent. The viscosity is preferably adjusted to 20 to 1000 mPa · s.
[0062]
As the ultraviolet curable adhesive, there are a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, both of which can be used.
As the radical ultraviolet curable adhesive, all known compositions can be used, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, monofunctional (meth) acrylate or polyfunctional (meth) acrylate can be used as the polymerizable monomer component. These can be used alone or in combination of two or more. Here, in the present invention, acrylate and methacrylate are collectively referred to as (meth) acrylate.
[0063]
Examples of 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.
[0064]
Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. Di (meth) such as neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of acrylate, di (meth) acrylate of tris (2-hydroxyethyl) isocyanurate, neopentyl glycol , Di (meth) acrylate of diol obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A, and triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane. Di or tri (meth) acrylate, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) Acrylate, poly (meth) acrylate of dipentaerythritol, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkylated phosphoric acid (meth) acrylate, etc. It is.
[0065]
Moreover, what can be used together with the polymerizable monomer includes polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate and the like as polymerizable oligomers.
Furthermore, as the photopolymerization initiator used in the present 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.
[0066]
Examples of such include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- ( 4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, etc. are preferably used, and other molecular cleavage types 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Propan-1-one and -Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one or the like may be used in combination, and 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.
[0067]
Examples of sensitizers for photopolymerization initiators include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzyl. An amine that does not cause an addition reaction with the polymerizable component, such as an amine and 4,4′-bis (diethylamino) benzophenone, can also be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that are excellent in solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.
[0068]
Further, as the cationic ultraviolet curable adhesive, all known compositions can be used, and an epoxy resin containing a cationic polymerization type photoinitiator corresponds to this. Examples of cationic polymerization type photoinitiators include sulfonium salts, iodonium salts, and diazonium salts.
An example of an iodonium salt is as follows. Diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate, bis (dodecylphenyl) iodonium hexafluoroantimonate Bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium hexafluorophosphate, 4-methylphenyl-4 -(1-Methylethyl) phenyliodonium hexafluoroa Chimoneto, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyl iodonium tetrakis (pentafluorophenyl) borate, and the like.
[0069]
Epoxy resins include bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, heterocyclic type, etc. It doesn't matter.
As the epoxy resin, it is preferable to use an epoxy resin having a low free chlorine and chlorine ion content so as not to damage the reflective layer. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.
[0070]
The ratio of the cationic polymerization type photoinitiator per 100 parts by weight of the cationic ultraviolet curable resin is usually 0.1 to 20 parts by weight, preferably 0.2 to 5 parts by weight. 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.
[0071]
In addition, UV curable adhesives include, as necessary, other additives such as thermal polymerization inhibitors, antioxidants typified by hindered phenols, hindered amines, phosphites, plasticizers and epoxy silanes, mercapto. Silane coupling agents represented by silane, (meth) acrylic silane and the like can also be blended for the purpose of improving various properties. These are selected from those having excellent solubility in ultraviolet curable compounds and those that do not impair ultraviolet transparency.
[0072]
(5) About the second recording layer 5
The second recording layer 5 is usually more sensitive than a recording layer used for a single-sided recording medium (CD-R, DVD-R) or the like. In this optical recording medium, since the power of the incident light beam is reduced due to the presence of the first recording layer 2 and the semitransparent reflective layer 3, etc., it is necessary to have particularly high sensitivity in order to record at about half the power. There is.
[0073]
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.
[0074]
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.
[0075]
(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 shorten the production tact time and reduce the cost, it is preferable to be thin to some extent, and is usually 400 nm or less. More preferably, it is set to 300 nm or less.
[0076]
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.
[0077]
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 to ensure high durability (high corrosion resistance), the reflective layer 6 is preferably used as an alloy rather than pure silver.
[0078]
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%. .
[0079]
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.
[0080]
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.
[0081]
(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 adhesion 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.
[0082]
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.
[0083]
(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.
[0084]
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.
[0085]
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.
[0086]
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.
[0087]
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.
[0088]
(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.
[0089]
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.
[0090]
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.
[0091]
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.
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.
[0092]
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.
[0093]
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.
[0094]
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.
[0095]
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.
[0096]
Furthermore, in the optical recording medium, if necessary, a print receiving layer that can be filled in (printed) on various surfaces other than the recording / reproducing light incident surface by various printers such as ink jet and thermal transfer, or various writing tools. May be provided.
Further, as an application example of this layer configuration, a medium having three or more recording layers is also possible. 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.
[0097]
(A-2) Type 1 optical recording medium manufacturing method
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.
[0098]
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 W in which the first recording layer 2 is not formed on the inner peripheral side of the disk (first substrate 1). ₁ To be provided. Further, this predetermined area W ₁ Is, for example, 0.1 mm or more, preferably 5 mm or more, more preferably 10 mm or more from the inner peripheral end of the first substrate 1. However, it may be formed with a thickness of 20 mm or less, preferably about 18 mm or less.
[0099]
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 the predetermined area W where the first substrate 1 is exposed. ₂ Form. In addition, the predetermined area W at this time ₂ Is formed from the outer peripheral edge of the first substrate 1 to a thickness of, for example, 0.1 mm to 5 mm, preferably about 1 mm. This predetermined area W ₁ , W ₂ Is formed for the purpose of easily measuring the film thickness of the translucent reflective layer 3 during the film thickness measurement described below.
[0100]
After forming the first recording layer 2, as shown in FIG. 2D, a predetermined region W on the first recording layer 2 and on the first substrate 1 is formed by sputtering or vapor-depositing an Ag alloy or the like. ₁ , W ₂ A translucent reflective layer 3 is also formed thereon.
Thereafter, as shown in FIG. 2 (e), the predetermined area W of the first recording layer 2 and the first substrate 1 is used. ₁ , W ₂ An ultraviolet curable resin or the like is applied to the substrate by spin coating or the like.
[0101]
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.
[0102]
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).
[0103]
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.
[0104]
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.
[0105]
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 Ni, Ag, Au, Cu, Pt and Pd or an alloy thereof is used. It is done.
[0106]
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 is composed of only the resin substrate 16, it is desirable that the resin substrate 16 has low adhesiveness with the resin constituting the intermediate resin layer 4 and high releasability. In addition, amorphous polyolefin is preferred from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability.
[0107]
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, and the surface is uneven 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.
[0108]
Subsequently, as shown in FIG. 2 (h), a coating solution in which at least an organic dye is dissolved in a solvent is applied to the surface of the intermediate resin layer 4 by spin coating or the like to form a second recording layer 5.
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.
[0109]
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.
[0110]
(A-3) Film thickness measuring method and film thickness control method of type 1 optical recording medium
In the type 1 optical recording medium according to this embodiment, the film thickness of the translucent reflective layer 3 can be measured using a known transmission method. In producing an optical recording medium having good quality characteristics, it is particularly important to control the thickness of the translucent reflective layer 3 more accurately.
[0111]
As described above, in the method for manufacturing an optical recording medium according to the present embodiment, the translucent reflective layer 3 is formed in a region wider than the region where the first recording layer 2 is formed by a predetermined region.
That is, for example, as shown in FIG. 3A, the translucent reflective layer 3 is formed not only on the first recording layer 2 but also on the inner circumference side of the first substrate 1. It is also formed on the first substrate 1 that is not present. Further, as shown in FIG. 3B, not only on the first recording layer 2 but also on the first substrate 1 on which the first recording layer 2 is not formed on the outer peripheral side of the first substrate 1. Is formed.
[0112]
A predetermined area where the first substrate 1 and the translucent reflective layer 3 are in contact with each other on the inner peripheral side and the outer peripheral side is defined as W. ₁ ′ And W ₂ ‘W’ ₁ ′ ≦ W ₁ , W ₂ ′ ≦ W ₂ It is. Further, here, a predetermined region W where the translucent reflective layer 3 and the first substrate 1 are in contact with each other. ₁ ′ And W ₂ ′ Is a predetermined area W ₁ And W ₂ The translucent reflective layer 3 is formed to the inner peripheral end and the outer peripheral end (that is, W ₁ = W ₁ ', W ₂ = W ₂ ′).
[0113]
And when measuring the film thickness of the translucent reflective layer 3, said predetermined area | region W ₁ ′ And W ₂ In ′. That is, the predetermined area W ₁ ′ And W ₂ ′, The transmittance is measured by irradiating light (for example, red laser, He—Ne laser, He—Cd laser, preferably visible light) from the upper surface side of the translucent reflective layer 3 or from the lower surface side of the first substrate 1. , Only the first substrate 1 having λ1 light transmission exists between the translucent reflective layer 3 and the first substrate 1, and the first recording layer 1 and the like do not exist at all. It is possible to easily and accurately measure the film thickness of only the translucent reflective layer 3.
[0114]
Thus, the area of the semitransparent reflective layer 3 is a predetermined area W than the area of the first recording layer 2. ₁ ', W ₂ Since the first recording layer 2 is not obstructed by being formed widely, the film thickness of the semitransparent reflective layer 3 can be accurately measured by the transmission method.
Thereby, since the film thickness of the translucent reflective layer 23 can be strictly controlled to an appropriate thickness, good jitter characteristics can be obtained, and errors during recording and reproduction of the optical recording medium are further reduced. be able to. That is, a high-quality optical recording medium can be manufactured.
[0115]
The predetermined area W ₁ ', W ₂ ′, Even if there is a buffer layer or a protective layer between the translucent reflective layer 3 and the first substrate 1, the buffer layer or the protective layer has λ1 light transmittance, and thus the same as above. In addition, it is possible to easily measure the film thickness of the translucent reflective layer 3.
Further, such a film thickness measurement is performed, for example, at a plurality of points in the diameter direction of the first substrate 1, and an average of these measured values can be obtained to obtain a more accurate film thickness.
[0116]
Furthermore, since the film thickness of the first recording layer 2 is thicker than the film thickness of the translucent reflective layer 3, the position where the film thickness of the first recording layer 2 does not affect, that is, as far as possible from the first recording layer 2. Position (predetermined area W ₁ ′, Inner peripheral side, predetermined area W ₂ It is preferable to measure the film thickness on the outer peripheral side in the ′.
Here, the predetermined region W is provided on both the inner and outer peripheral sides of the first substrate 1. ₁ ', W ₂ However, it may be provided only on the inner peripheral side or only on the outer peripheral side.
[0117]
Further, the above film thickness measurement is automatically performed by a film thickness measuring device (not shown) in the manufacturing apparatus for manufacturing the optical recording medium (that is, the manufacturing process). It is fed back to a film thickness control device (not shown) for controlling the film thickness of the transparent reflective layer 3.
For example, when the film thickness of the translucent reflective layer 3 is measured by the film thickness measuring device, this film thickness information is transmitted to the film thickness control device, and the film thickness control device, based on this film thickness information, The conditions of the layer 3 such as sputtering and vapor deposition (for example, when sputtering is used, the sputtering time, the sputtering voltage, the distance between the first substrate 1 and the Ag target, etc.) are adjusted, and the translucent reflection of the next disk The film thickness of the layer 3 is controlled to be an appropriate film thickness.
[0118]
(B-1) Configuration of type 2 optical recording medium
FIG. 4 is a schematic cross-sectional view showing the 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 translucent reflective layer) 23, transparent adhesive layer 24, buffer layer 28, second recording layer containing a dye (second dye-containing recording layer) 25, reflective layer 26, a disk-shaped transparent second substrate (second substrate) 27 is provided in this order. The light beam is irradiated from the first substrate 21 side, and recording / reproduction is performed.
[0119]
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, it can be said that the film is substantially light transmissive.
[0120]
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.
[0121]
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.
[0122]
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.
[0123]
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.
[0124]
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 200 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.
[0125]
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 type 2 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 FIG. In addition, FIG. 5 is process drawing for demonstrating this 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. 5A, the first substrate 21 having grooves and lands and pre-pits formed on the surface with irregularities is manufactured by injection molding or 2P method.
Next, as shown in FIG. 5B, 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. At this time, as shown in FIG. 5B, a predetermined area W in which the first recording layer 22 is not formed on the inner peripheral side of the disc (first substrate 1). _Ten To be provided. Further, this predetermined area W _Ten Is, for example, 0.1 mm or more, preferably 5 mm or more, more preferably 10 mm or more from the inner peripheral end of the first substrate 21. However, it may be formed with a thickness of 20 mm or less, preferably about 18 mm or less.
[0128]
Further, the outer peripheral side of the first substrate 21 is washed to remove the first recording layer 22, and a predetermined area W where the first substrate 21 is exposed. ₂₀ Form. In addition, the predetermined area W at this time ₂₀ Is formed from the outer peripheral edge of the first substrate 21 to a thickness of, for example, 0.1 mm to 5 mm, preferably about 1 mm. This predetermined area W _Ten , W ₂₀ Is formed for the purpose of easily measuring the film thickness of the translucent reflective layer 23 during the film thickness measurement described below.
[0129]
After forming the first recording layer 22, as shown in FIG. 5D, a predetermined region W on the first recording layer 22 and on the first substrate 21 is formed by sputtering or vapor-depositing an Ag alloy or the like. _Ten , W ₂₀ A translucent reflective layer 23 is also formed thereon to form a laminated structure A.
On the other hand, as shown in FIG. 5 (d), the second substrate 27 having grooves, lands, and pits formed on the surface with irregularities is produced by injection molding or 2P method.
[0130]
Then, as shown in FIG. 5E, a reflective layer 26 is formed on the surface of the second substrate 27 on the side having irregularities by sputtering or vapor-depositing an Ag alloy or the like.
Thereafter, as shown in FIG. 5F, a coating solution in which at least an organic dye is dissolved in a solvent is applied on the reflective layer 26 by spin coating or the like to form the second recording layer 25.
[0131]
Next, as shown in FIG. 5G, a buffer layer 28 is formed by sputtering a dielectric material or the like to form a laminated structure B.
And as shown in FIG.5 (h), after apply | coating adhesives, such as ultraviolet curable resin used as the transparent contact bonding layer 24, on the laminated structure A, the laminated structure B is mounted, and it adhere | attaches by high-speed rotation, a press, etc. Spread the agent on the entire surface. 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 irradiating 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) Type 2 optical recording medium film thickness measurement method and film thickness control method
In the type 2 optical recording medium according to the present embodiment, the film thickness of the translucent reflective layer 23 can be measured using a known transmission method, similarly to the type 1 optical recording medium described above.
That is, as shown in FIGS. 3A and 3B, the translucent reflective layer 23 is not only on the first recording layer 22 on the inner peripheral side and the outer peripheral side of the first substrate 21, but also on the first recording layer. 22 is also formed on the first substrate 21 on which no film is formed.
[0134]
In each of the inner peripheral side and the outer peripheral side, a predetermined area where the first substrate 21 and the semitransparent reflective layer 23 are in contact is defined as W. _Ten ′ And W ₂₀ ‘W’ _Ten ′ ≦ W _Ten , W ₂₀ ′ ≦ W ₂₀ It is. Here, the predetermined region W where the translucent reflective layer 23 and the first substrate 21 are in contact with each other _Ten ′ And W ₂₀ ′ Is a predetermined area W _Ten And W ₂₀ The translucent reflective layer 23 is formed to the inner peripheral end and the outer peripheral end (that is, W _Ten = W _Ten ', W ₂₀ = W ₂₀ ′).
[0135]
And when measuring the film thickness of the translucent reflective layer 23, said predetermined area | region W _Ten ′ And W ₂₀ In ′. That is, the predetermined area W _Ten ′ And W ₂₀ ′, The transmittance is measured by irradiating light (for example, red laser, He—Ne laser, He—Cd laser, etc., preferably visible light) from the upper surface side of the translucent reflective layer 23 or from the lower surface side of the first substrate 21. , Only the first substrate 21 having λ1 light transmission exists between the translucent reflective layer 23 and the first substrate 1, and the first recording layer 21 and the like do not exist at all. It is possible to easily and accurately measure the film thickness of only the translucent reflective layer 23.
[0136]
Thus, also in the type 2 optical recording medium according to the present embodiment, the region of the semitransparent reflective layer 23 is larger than the region of the first recording layer 22 by the predetermined region W. _Ten ', W ₂₀ Since the first recording layer 22 is not obstructed by being formed wide by ′, the film thickness of the translucent reflective layer 23 can be accurately measured by the transmission method.
Thereby, since the film thickness of the translucent reflective layer 23 can be strictly controlled to an appropriate thickness, good jitter characteristics can be obtained, and errors during recording and reproduction of the optical recording medium are further reduced. be able to. That is, a high-quality optical recording medium can be manufactured.
[0137]
The predetermined area W _Ten ', W ₂₀ ′, Even if there is a buffer layer or a protective layer between the translucent reflective layer 23 and the first substrate 21, these buffer layers and protective layers have λ1 light transmittance, so that Further, it is possible to easily measure the film thickness of the translucent reflective layer 23.
Further, such a film thickness measurement is performed at, for example, a plurality of points in the diameter direction of the first substrate 21 and an average of these measured values can be obtained to obtain a more accurate film thickness.
[0138]
Further, since the film thickness of the first recording layer 22 is thicker than the film thickness of the translucent reflective layer 23, the position where the film thickness of the first recording layer 22 does not affect, that is, as far as possible from the first recording layer 22. Position (predetermined area W _Ten ′, Inner peripheral side, predetermined area W ₂₀ It is preferable to measure the film thickness on the outer peripheral side in the ′.
Here, the predetermined area W is provided on both the inner and outer peripheral sides of the first substrate 21. _Ten ', W ₂₀ However, it may be provided only on the inner peripheral side or only on the outer peripheral side.
[0139]
The film thickness measurement is automatically performed by the above-described film thickness measuring apparatus, and the film thickness information measured at this time is a film thickness control apparatus (not shown) for controlling the film thickness of the translucent reflective layer 23. It is supposed to be fed back to.
[0140]
[2] Second embodiment
Next, a film thickness measuring method according to the second embodiment of the present invention will be described. This film thickness measurement method can be used for both type 1 and type 2 optical recording media. In the following, a case of a type 1 optical recording medium will be described as an example.
[0141]
In this embodiment, first, as shown in FIG. 6A, after the first recording layer 2 is formed on the first substrate 1, the amount of light transmitted through the first substrate 1 and the first recording layer 2 by the transmission method ( First transmitted light amount P ₁ Measure. Since the first substrate 1 has λ1 light transmittance, the transmitted light amount P measured at this time is measured. ₁ Can be handled as the amount of light transmitted through the first recording layer 2.
[0142]
Then, after the semitransparent reflective layer 3 is formed on the first recording layer 2, the transmitted light amount (second transmitted light amount) P of the first substrate 1, the first recording layer 2, and the semitransparent reflective layer 3 by the transmission method. ₂ Measure. Similarly to the above, since the first substrate 1 has λ1 light transmittance, the transmitted light amount P measured at this time is measured. ₂ Can be handled as the amount of light transmitted through the first recording layer 2 and the semitransparent reflective layer 3.
[0143]
Next, the transmitted light amount P thus obtained is ₁ And transmitted light amount P ₂ Difference P _Three The film thickness of the translucent reflective layer 3 is obtained from the relationship (map) between the amount of transmitted light and the film thickness obtained beforehand through experience.
Thus, in the film thickness measurement method according to the present embodiment, the predetermined region W as in the first embodiment. ₁ , W ₂ , W ₁ ', W ₂ ′ (Type 1 optical recording medium) or predetermined area W _Ten , W ₂₀ , W _Ten ', W ₂₀ ′ (Type 2 optical recording medium) need not be provided, and the transmitted light amount P of the first recording layer 2 is not necessary. ₁ And the transmitted light amount P of the first recording layer 2 and the translucent reflective layer 3 ₂ Therefore, the film thickness of the translucent reflective layer 3 can be easily obtained.
[0144]
Further, such a measurement is performed at a plurality of points in the diameter direction and the circumferential direction of the disk, and for example, by taking an average of these measured values, a more accurate film thickness of the translucent reflective layer 3 can be obtained. Is possible.
Similarly to the first embodiment, the above-described film thickness measurement and calculation are automatically performed by the film thickness measuring apparatus in the manufacturing apparatus for manufacturing the optical recording medium (that is, the manufacturing process). The film thickness information measured by the apparatus is fed back to the film thickness control apparatus that controls the film thickness of the translucent reflective layer 3.
[0145]
Furthermore, in this embodiment, since the film thickness distribution of the translucent reflective layer 3 in the disk surface is also known, this film thickness distribution information is fed back to the film thickness control device, and the sputtering conditions for forming the translucent reflective layer 3 are obtained. Alternatively, finer film thickness control can be performed by adjusting the deposition conditions.
For example, when the translucent reflective layer 3 is formed by sputtering and the film thickness unevenness in the disk surface is large, the sputtering voltage is decreased to reduce the sputtering time (sputtering time). Is controlled to be longer. Alternatively, the control is performed so that the flow rate of the sputtering gas (usually Ar or the like) is reduced when the unevenness of the film thickness distribution in the disk surface is large.
[0146]
In the present embodiment, because the measurement is easy, the film thickness is obtained by measuring the amount of transmitted light. However, the light absorption rate of the first recording layer 2 and the translucent reflective layer is substantially constant. If it thinks that there exists, it is also possible to obtain | require a transmitted light quantity indirectly by measuring these reflected light quantities.
[0147]
[3] 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.
For example, when measuring the film thickness of the translucent reflective layer 3 (23), both the film thickness measuring method according to the first embodiment and the film thickness measuring method according to the second embodiment may be performed. .
[0148]
That is, the manufacturing method according to the first embodiment is used to provide predetermined areas on the inner and outer peripheral sides of the disc. In the manufacturing process, the first recording layer 2 (22) is formed, and then the first recording layer 2 (22) is formed by the transmission method. Transmitted light quantity P of one recording layer 2 (22) ₁ After the semi-transparent reflective layer 3 (23) is formed on the first recording layer 2 (22), the transmitted light amount P of the first recording layer 2 (22) and the semi-transparent reflective layer 3 (23) is measured. ₂ Is measured, and the transmitted light amount P of only the translucent reflective layer 3 (23) is measured. _Three Is calculated to determine the film thickness of the translucent reflective layer 3 (23). On the other hand, the predetermined area W on the inner and outer peripheral sides of the disk ₁ ', W ₂ ′ (W _Ten ', W ₂₀ ′), The thickness of the translucent reflective layer 3 (23) is obtained by measuring the amount of light transmitted through the translucent reflective layer 3 (23) by the transmission method.
[0149]
As described above, the film thickness information obtained by the film thickness measurement method according to the first embodiment and the film thickness information and the film thickness distribution information obtained by the film thickness measurement method according to the second embodiment are more accurate. It is also possible to obtain the film thickness and film thickness distribution of the translucent reflective layer 3 (23), and it is possible to perform more precise film thickness control by feeding back this information to the film thickness controller. .
[0150]
Further, within the scope of the present invention, the order of the layers of the optical recording medium and the layers and the manufacturing method may be changed. In the above embodiment, a so-called substrate surface incident medium has been described as an example, but a film surface incident medium may be used.
In addition, the present invention is applied to a medium having three or more recording layers and two or more translucent reflective layers, and recording and reproducing light by entering light from one side. It may be used for film thickness measurement and film thickness control.
[0151]
For example, light transmissive substrate / first recording layer / first translucent reflective layer / first intermediate layer / second recording layer / second translucent reflective layer / second intermediate layer / third recording layer / reflective layer, etc. In the optical recording medium having a layer structure, the first translucent reflective layer is formed wider than the first recording layer, and the second translucent reflective layer is the first recording layer, the first translucent reflective layer, and the second recording layer. By forming it wider than this, the film thicknesses of both translucent reflective layers can be accurately measured.
[0152]
Alternatively, after forming the first recording layer on the substrate, the first transmitted light amount is measured, and after forming the first translucent reflective layer, the second transmitted light amount is measured. After determining the film thickness of the first translucent reflective layer from the difference in the second transmitted light amount), after forming the second recording layer and measuring the third transmitted light amount, after forming the second translucent reflective layer The fourth transmitted light amount is measured, and the film thickness of the second translucent reflective layer can be obtained from the difference between the two (third transmitted light amount and fourth transmitted light amount).
[0153]
Further, in the above embodiment, in the case of an optical recording medium having only one translucent reflective layer 3 (23), the film thickness information of the translucent reflective layer 3 (23) is obtained from the next manufactured disc. Although it was used to control the film thickness of the translucent reflective layer, if it is an optical recording medium having a plurality of translucent reflective layers of the same material, the film thickness information of the semitransparent reflective layer formed first is You may make it use for film thickness control of the translucent reflective layer formed in this.
[0154]
The method for measuring the film thickness of the optical recording medium of the present invention can also be applied to a phase change medium, but as described in the above embodiment, it is more effective when applied to a dye medium having a dye recording layer. .
In the phase change medium, like the dye medium, there is a demand to strictly control the film thickness of the translucent reflective layer. However, in the phase change medium, all layers are usually formed by a vacuum process such as sputtering. Therefore, the film thickness variation of the other layers is small, and the film thickness of the translucent reflective layer can be obtained without any contrivance as in the present invention. For example, after all the layers such as the recording layer, the protective layer, and the semitransparent reflective layer are formed, the total amount of transmitted / reflected light is measured, and calculation is performed based on the refractive index of each layer. The film thickness of the transparent reflective layer can be determined.
[0155]
On the other hand, in the dye medium, the dye recording layer is usually formed by a coating method, particularly a spin coating method. Such a coating process is simpler than the vacuum process, but the film thickness tends to fluctuate. Therefore, in the dye medium, it is difficult to obtain the film thickness of the translucent reflective layer by the film thickness measuring method of the phase change medium as described above, and the film thickness measuring method of the present invention is more required.
[0156]
In addition, the present invention has an aspect that the dye medium is easier to apply than the phase change medium in the process.
For example, in the present invention, the area of the semitransparent reflective layer is formed wider than the area of the other layers, but in the phase change type medium, the inner / outer circumference of the medium is masked and all layers are formed by a series of vacuum processes. Since the film is formed, it is usually difficult to form only the translucent reflective layer wider than the other layers, or to take out and measure the amount of transmitted light once during the film formation process.
[0157]
On the other hand, in the dye medium, since the dye recording layer is usually formed independently by a coating process and the semitransparent reflective layer is independently formed by a vacuum process, it is easy to form only the semitransparent reflective layer wider than other layers. In addition, it is easy to measure the amount of transmitted light between the formation of the dye recording layer and the formation of the translucent reflective layer.
[0158]
【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 another layer is provided between a light-transmitting substrate and a translucent reflective layer, The region of the semitransparent reflective layer is formed in a region wider than the region of the other layer by a predetermined region, and nothing is interposed between the substrate and the semitransparent reflective layer in this predetermined region. The film thickness of the translucent reflective layer can be easily and accurately measured by the transmission method.
[0159]
According to the optical recording medium of the present invention as set forth in claim 2, even in a laminated structure in which a dye-containing recording layer is provided between a light-transmitting substrate and a translucent reflective layer, the region of the translucent reflective layer Is formed in a predetermined area wider than the area of the dye-containing recording layer, and nothing is interposed between the substrate and the translucent reflective layer in this predetermined area. The thickness of the reflective layer can be easily and accurately measured.
[0160]
According to the optical recording medium of the present invention described in claim 3, since the substrate and the translucent reflective layer are in contact with each other directly or through a light-transmitting layer in a predetermined region, the transmission method is used in this predetermined region. The film thickness of the translucent reflective layer can be measured easily and accurately.
According to the optical recording medium of the present invention described in claim 4, 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.
[0161]
According to the method for measuring the film thickness of the optical recording medium of the present invention described in claim 5, the film thickness of the translucent reflective layer can be easily measured by a transmission method in a predetermined region.
According to the film thickness measuring method of the optical recording medium of the present invention described in claim 6, it is possible to measure the film thickness at an arbitrary position and to obtain the film thickness distribution.
According to the film thickness control method for an optical recording medium of the present invention as set forth in claim 7, the film thickness of the translucent reflective layer is measured by a transmission method in a predetermined region, and is formed thereafter based on this film thickness measurement information. The film thickness of the semitransparent reflective layer is controlled, so that more accurate film thickness control is possible.
[0162]
According to the method for manufacturing an optical recording medium of the present invention described in claim 8, another layer is formed on the substrate, and the other layer is semitransparent in a region wider than the region of the other layer by a predetermined region. Since the reflective layer is formed, the film thickness of the translucent reflective layer can be easily and accurately measured in this predetermined region by the transmission method.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a type 1 optical recording medium according to a first embodiment of the present invention.
FIGS. 2A and 2B are process diagrams for explaining a method of manufacturing a type 1 optical recording medium according to the first embodiment of the invention. FIGS.
FIGS. 3A and 3B are diagrams for explaining a method of measuring the thickness of a type 1 optical recording medium according to the first embodiment of the present invention, in which FIG. It is a schematic diagram which shows the film thickness measurement of the outer peripheral side.
FIG. 4 is a schematic diagram showing a type 2 optical recording medium according to the first embodiment of the present invention.
FIG. 5 is a process diagram for explaining the manufacturing method of the type 2 optical recording medium according to the first embodiment of the invention.
6A and 6B are diagrams for explaining a method of measuring the thickness of a type 1 optical recording medium according to a second embodiment of the present invention, in which FIG. 6A is a measurement of transmitted light amounts of a first substrate and a first recording layer; FIG. 4B is a schematic diagram illustrating measurement of transmitted light amounts of the first substrate, the first recording layer, and the translucent reflective layer.
FIG. 7 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
4 Intermediate resin layer (intermediate layer)
5,25 Second recording layer (second dye-containing recording layer)
6,26 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
W ₁ ', W ₂ ', W _Ten ', W ₂₀ ′ Predetermined area

Claims (8)

Provide another layer between the light-transmitting substrate and the translucent reflective layer,
An optical recording medium, wherein a region of the translucent reflective layer is formed by a predetermined region wider than a region of the other layer. The optical recording medium according to claim 1, wherein the other layer includes a dye-containing recording layer on which information can be optically recorded. 3. The optical recording medium according to claim 1, wherein the substrate and the translucent reflective layer are in contact with each other directly or through a light-transmitting layer in the predetermined region. 4. The optical recording according to claim 1, wherein the substrate has a disk shape, 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 1-4,
A method for measuring a film thickness of an optical recording medium, comprising measuring the film thickness of the translucent reflective layer in the predetermined region by a transmission method. A method for measuring a film thickness of an optical recording medium having another layer between a light-transmitting substrate and a translucent reflective layer,
Obtain the relationship between the film thickness of the translucent reflective layer and the amount of transmitted light in advance,
After forming the other layer, the first transmitted light amount of the substrate and the other layer is measured by a transmission method,
After forming the translucent reflective layer, the second transmitted light amount of the substrate and the other layers and the translucent reflective layer is measured by a transmission method,
A method for measuring a film thickness of an optical recording medium, comprising determining a film thickness of the translucent reflective layer from a difference between the first transmitted light quantity and the second transmitted light quantity. It is the film thickness control method of the optical recording medium of any one of Claims 1-4,
Measuring the film thickness of the semitransparent reflective layer in the predetermined region by a transmission method, and controlling the film thickness of the semitransparent reflective layer formed thereafter based on the film thickness measurement information; A method for controlling the film thickness of a recording medium. A method for producing an optical recording medium according to any one of claims 1 to 4,
Forming the other layer on the substrate;
A method for producing an optical recording medium, comprising: forming the translucent reflective layer on a region wider than a region of the other layer by a predetermined region on the other layer.

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