JP2004079154A - Optical recording medium and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium made of an organic material capable of attaining recording in a blue laser wavelength region, in particular, even in a wavelength region near 405 nm, and to provide the optical recording medium capable of attaining high density, a high degree of modulation, having a small change in a reflectance or the like and a recording characteristic such as recording sensitivity, the degree of modulation, jitter, and an error rate against variations in a recording and reproducing wavelength and excellent keeping quality, and to provide a manufacturing method thereof. <P>SOLUTION: The optical recording medium includes at least one coloring matter and has a 3-layer structure wherein an optical absorbing layer whose film thickness is 5 to 200 nm is inserted between first and second layers, the thermal conductivity of the first layer is in a relation of a multiple of 3 to 310 with respect to the thermal conductivity of the second layer in a relative ratio, and the first and second layers are characterized in to contain a metallic material. <P>COPYRIGHT: (C)2004,JPO

Description

【００２２】
上記式中、Ｍは、Ｃｕ、ＶＯ、Ｎｉ、Ｈ、Ｚｎ、Ｐｄ、Ｃｄ、Ｃｏ、Ｆｅの何れかであり、Ｒとしては、下記表１〜表８に示すものが挙げられる。
但し、表８に示した化合物のＭは、表に記載した通りの有機置換基を有するものである。また、表１〜表８中、（１／４）とあるのは、４個のＲのうち１個がその置換基であることを意味し、同様に（２／４）（３／４）（４／４）とあるのは、２〜４個がその置換基であることを意味する。また（１／３）とあるのは、４個のＲのうち一個は水素であり、残りの３個のＲのうち１個がその置換基であることを意味し、同様に（２／３）とあるのは、２個がその置換基であることを意味する。また、上記のような表示が無いものは、４個のＲが全てその置換基であることを意味する。
【表１】

【表２】

【表３】

【表４】

【表５】

【表６】

【表７】

【表８】

【００２３】
また、アミニウム系色素などの各種クエンチャが添加された色素材料を用いることもできる。更には、上記色素材料群より選択される１種又は２種以上の色素材料を樹脂中に分散したものを用いることもできる。
色素材料を分散可能な樹脂材料としては、アクリル樹脂、ビニル樹脂、フェノール樹脂、フッ素樹脂、シリコーン樹脂、ポリアミド樹脂、セルロース樹脂などを挙げることができる。
光吸収層４は、先に例示的に列挙した色素材料群より選択された色素材料の溶剤溶液をスピンコートして形成する。基板の溝状のプリフォーマットパターン２に対応して形成されている第一の層の溝内に色素材料を充填した後、該溝の間の平坦部（基板のプリフォーマットパターン２の間のランド部２ｃに対応して形成されている平坦部）に付着した色素材料を選択的に除去し、第一の層の表面を露出すると共に、前記溝内にのみ色素材料を充填することによって形成できる。
なお、色素材料の溶剤としては、アルコール系溶剤又はセルソルブ系溶剤などを用いることができる。
【００２４】
更に、二座配位を取り得るキレート材を含有させて色素の褪色防止を図ることもできる。このようなキレート材としては、無機酸類、ジカルボン酸類、オキシカルボン酸類、ジオキシ化合物類、オキシオキシム類、オキシアルデヒド及び誘導体類、ジケトン及び類似化合物類、オキシキノン類、トロボロン類、Ｎ−オキシド化合物類、アミノカルボン酸及び類似化合物類、ヒドロキシルアミン類、オキシン類、アルジミン類、オキシアゾ化合物類、ニトロソナフトール類、トリアゼン類、ピウレット類、ホルマザン類及びジチゾン類、ビクアリド類、グリオキシム類、ジアミン及び類似化合物類、ヒドラジン誘導体類、チオエーテル類などが挙げられる。
更に、イミノ基を有する誘導体も使用可能である。
【００２５】
光吸収層４を成膜するための溶剤は、第一の層３にマイクロポアがある場合は、マイクロポアに進入しない一定の接触角を有する溶液を形成しうる材料を選択する必要があるが、それ以外には特に限定はない。
ここで、マイクロポアに進入しない一定の接触角は、マイクロポアのサイズにより必要とされる表面張力が異なるため、その値を数値で示すことはできない。しかし、成膜後のマイクロポア部分に発生する平均膜厚よりも平均膜厚の２％以上薄い部分の面積は２２５μｍ^２が上限であり、２２５μｍ^２を超えるとトラッキング精度、エラー訂正が不可能になるなどの問題が発生するので、マイクロポアに溶液が浸透した場合でも上記の範囲以上に浸透が広がらなければ、マイクロポアに進入しない一定の接触角を有する溶液に相当すると判断する。
【００２６】
上記マイクロポアに進入しない一定の接触角を有する溶液を形成することができる溶剤としては、例えば、酢酸ブチル、セロソルブアセテートなどのエステル；メチルエチルケトン、シクロヘキサノン、メチルイソブチルケトンなどのケトン；ジクロルメタン、１，２−ジクロルエタン、クロロホルムなどの塩素化炭化水素；ジメチルホルムアミドなどのアミド；シクロヘキサンなどの炭化水素；テトラヒドロフラン、エチルエーテル、ジオキサンなどのエーテル；エタノール、ｎ−プロパノール、イソプロパノール、ｎ−ブタノール、ジアセトンアルコールなどのアルコール；２，２，３，３−テトラフルオルプロパノールなどのフッ素系溶剤；エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、プロピレングリコールモノメチルエーテルなどのグリコールエーテル類などが挙げられる。
また、これらの溶剤としては、使用する色素の溶解度が５ｍｇ／１ｍｌ以上あるものを用いる必要がある。そこで使用する色素の溶解性を考慮して適宜単独で又は二種以上併用して用いる。また、塗布液中には、必要に応じて酸化防止剤、ＵＶ吸収剤、可塑剤、潤滑剤など各種の添加剤を添加してもよい。
【００２７】
光吸収層４の材料として結合剤を併用する場合の結合剤の例としては、ゼラチン、セルロース誘導体、デキストラン、ロジン、ゴムなどの天然有機高分子物質；ポリエチレン、ポリプロピレン、ポリスチレン、ポリイソブチレン等の炭化水素系樹脂；ポリ塩化ビニル、ポリ塩化ビニリデン、ポリ塩化ビニル・ポリ酢酸ビニル共重合体等のビニル系樹脂；ポリアクリル酸メチル、ポリメタクリル酸メチル等のアクリル樹脂；ポリビニルアルコール、塩素化ポリエチレン、エポキシ樹脂、ブチラール樹脂、ゴム誘導体、フェノール・ホルムアルデヒド樹脂等の熱硬化性樹脂の初期縮合物などの合成有機高分子を挙げることができる。
上記結合剤の使用量は、一般に色素に対して０．０１〜５０倍量（質量比）の範囲とし、好ましくは０．１〜５倍量（質量比）の範囲とする。
このようにして調製される塗布液の濃度は、一般に０．０１〜１０質量％の範囲とし、好ましくは０．１〜５質量％の範囲とする。
塗布方法としては、スプレー法、スピンコート法、ディップ法、ロールコート法、ブレードコート法、ドクターロール法、スクリーン印刷法などを挙げることができる。
【００２８】
また、光吸収層の材料としては、芳香族化合物、脂肪族化合物、アミド、エステル、アミン、ウレア、硫黄化合物及びヒドロキシ化合物からなる群から選択される少なくとも１つを用いることもできる。
更に、光吸収層は、分解温度が１６０〜５００℃の有機物質を含有することが望ましい。このような有機物質は、上記例示化合物の中から適宜選択すればよい。
分解温度が１６０℃よりも低いと環境に影響され、保存性に問題が発生する。また、分解温度が５００℃よりも高いと記録時に材料の分解を誘発することができず記録感度が低下する問題ある。
【００２９】
一方、光吸収層４は光を吸収して変形、変質するか又は光学的に変化する。
光吸収層の変形、変質に伴なって、第一の層、第二の層、基板、保護層も変形、変質することがある。
第一の層にＡｇ、Ｃｕ、Ａｌなどの金属を選択し、第二の層にＳｉＣ、ＳｉＯ_２などの誘電体又はＴｅなどの金属を選択した場合、熱伝導率の比は３〜３１０倍の範囲となり、変質部分が記録マーク領域とほぼ等しく、ジッターやディビエーションの少ない良好な記録をすることができた。この場合の光吸収層は変質が促進され変形は僅かであった。
光吸収層４の膜厚は、５ｎｍより薄いと熱の吸収が十分でなく、変形や変化が不十分となる。また、２００ｎｍより厚いと体積が大きいため変形が抑えられたり、熱的な影響を受けて光学的に変化できない部分が存在するため問題である。
光吸収層は単層でも重層でもよい。
【００３０】
第二の層５に用いる材料としては、金属材料を含有すること以外、特に限定はなく、例えば前記の第一の層に用いるのと同様の材料を使用することができる。保護層１０は、例えばＳｉＯ、ＳｉＮ、ＡｌＮ等の無機材料や、光硬化性樹脂などの有機材料を用いて形成することができる。
無機保護層は、真空成膜法によって形成することができ、有機保護層は、第二の層５上に光硬化性樹脂膜（例えば、大日本インキ化学工業社製のＳＤ１７００、ＳＤ３１８、ＳＤ３０１）をスピンコートした後、樹脂硬化光を照射することによって形成できる。
また、高密度化を図るため高ＮＡのレンズを用いる場合には、保護層を光透過性とする必要がある。
例えば高ＮＡ化すると、再生光が透過する部分の膜厚を薄くする必要がある。これは、高ＮＡ化に伴い、光学ピックアップの光軸に対してディスク面が垂直からズレる角度（いわゆるチルト角、光源の波長の逆数と対物レンズの開口数の積の２乗に比例する）により発生する収差の許容量が小さくなるためであり、このチルト角が基板の厚さによる収差の影響を受け易いためである。
従って、基板の厚さを薄くしてチルト角に対する収差の影響をなるべく小さくするようにしている。
【００３１】
そこで、例えば基板上に凹凸を形成して記録層とし、その上に反射膜を設け、更にこの上に光を透過する薄膜である光透過性の保護層を設けるようにし、保護層側から再生光を照射して記録層の情報を再生するような光記録媒体や、基板上に反射膜を設け、その上に熱受容層、光吸収層を形成して記録層とし、更にこの上に光透過性を有する保護層を設けるようにし、保護層側から再生光を照射して記録層の情報を再生するような光記録媒体が提案されている。
このようにすれば、カバー層を薄型化していくことで対物レンズの高ＮＡ化に対応可能である。つまり、薄いカバー層を設け、このカバー層側から記録再生することで、更なる高記録密度化を図ることができる。
なお、このような保護層は、ポリカーボネートシートや紫外線硬化型樹脂により形成されるのが一般的である。厚みは０．１ｍｍ以下が好適である。またポリカーボネートシートは変性アクリル樹脂系両面接着剤で固定される。
【００３２】
一方、第一、第二の層には超解像技術を付加することも可能である。通常光ディスクの再生限界はλ／２ＮＡで表される。（ここで、λは波長、ＮＡは光の絞り込み角度の正弦である）
この限界を超える分解能を実現するため、以下の超解像技術を適応する。即ち、対物レンズでレーザー光を媒体の上に集光させた再生ビームの強度分布Ｉは
Ｉ＝Ｉ_０×ｅｘｐ〔−２（ｒ／ｒ_０）^２〕
で表される（ここで、Ｉ_０はレーザービームの中心部の強度、ｒ_０はレーザービームの強度が１／ｅ^２になる半径である）。
このように強度分布がガウス分布の再生ビームで記録媒体が加熱されると、ビームが照射された部分の温度分布も同じようにガウス分布に近いものとなる。
ビームの中心付近の温度が高い部分を再生領域とし、周辺部分の温度の低い部分を記録再生に関与しない部分とすることで実効的なビームスポットの径が小さくなり分解能が向上する。
ガウス分布では中心温度のおよそ０．６倍のところ、即ち半径ｒ_０／２のところで傾斜が急になる。この部分に合わせると安定した記録再生が可能となる。
【００３３】
ディスク形態としては、第一の層、光吸収層、第二の層からなる３層構造（以下、３層構造という）を内側にはさむ形で２枚の基板を貼り合わせた構造とすることができる。また、２枚の基板を貼り合わせず、いわゆる単板の構造とすることもできる。
これら２枚の基板は、それぞれが３層構造を有しており、光ビームをどちらか一方の基板から照射することによって、それぞれの光吸収層に情報の記録を行い、光ビームを照射する側の基板及び３層構造が上記光ビームのうち４０％以上を透過する構成としてもよい。
また、ディスク形態として、１枚の基板上に３層構造を２組以上設けることも可能である。
このとき、光ビームを基板側から照射することによって、それぞれの光吸収層に情報の記録を行ってもよいし、光ビームを基板と反対側から照射することによって、それぞれの光吸収層に情報の記録を行ってもよい。
【００３４】
上記のように、光ビームをある一方向から照射して複数の光吸収層に情報の記録を行うような場合、光ビーム入射側の光吸収層と、その反対側の光吸収層とが異なる膜厚を有していてもよい。
また、光ビーム入射側の第一の層の主成分となる元素と、その反対側の第一の層の主成分となる元素とが同一であり、該主成分となる元素の含有量が光ビーム入射側の第一の層とその反対側の第一の層とで異なっていてもよい。
更に、光ビーム入射側の第一の層の主成分となる元素のうち少なくとも１種類の元素と、その反対側の第一の層の主成分となる元素のうち少なくとも１種類の元素とが、異なる元素であってもよい。
光ビーム入射側の光吸収層の融点と、その反対側の光吸収層の融点とが異なっていてもよい。
【００３５】
基板上に螺旋状又は同心円状に案内溝を形成し、案内溝上又は隣接する２本の案内溝の間（案内溝間と呼ぶ）のどちらか一方を記録トラックとし、該記録トラックに情報を記録する構成を取ることができる。また、基板上に螺旋状又は同心円状に案内溝を形成し、案内溝上及び案内溝間の両方を記録トラックとし、該記録トラックに情報を記録する構成を取ることもできる。
２枚の基板のそれぞれが３層構造を有しており、光ビームをどちらか一方の基板から照射することによってそれぞれの光吸収層に情報の記録を行う場合、基板上に形成された螺旋状又は同心円状の案内溝の形状が、光ビーム入射側とその反対側とで異なっていることが好ましい。
このとき、光ビーム入射側の基板の案内溝の深さが、その反対側の基板の案内溝の深さよりも浅いか、又は光ビーム入射側の基板の案内溝の幅が、その反対側の基板の案内溝の幅よりも広ければ、より好ましい。
【００３６】
光記録媒体のアドレス情報等をプリフォーマット信号として基板に予め形成することができる。その形態としては、凹形状又は凸形状のエンボスピット、或いは情報に応じてグルーブ部やランド部の幅を変調するウォーブル方式が可能である。ウォーブル方式としては、グルーブ部の内周側又は外周側の一方の側面のみ、或いはグルーブ部の内周側及び外周側の両方の側面を蛇行させる方式を採用することができる。
【００３７】
上記二組の３層構造を有する場合において、第一組の反射率、透過率、吸収率をｒ１、ｔ１、ａ１、第二組の反射率、透過率、吸収率をｒ２、ｔ２、ａ２とし、第一組からの全反射率をＲ１、第二組からの全反射率をＲ２とし、更に第一組の全吸収率をＡ１、第二組の全反射率をＡ２とすると、これらのパラメータに対して次の関係が成立する。
ｒ１＋ｔ１＋ａ１＝１
ｒ２＋ｔ２＋ａ２＝１
Ｒ１＝ｒ１
Ｒ２＝ｒ２×ｔ１２
Ａ１＝ａ１
Ａ２＝ａ２×ｔ１
第一組と第二組の信号品質が同じであるためには両者の反射率が同一であることが、また、両者の記録感度が同じであるためには両者の吸収率が同一であることが必要条件であり、従って、次式を満足する必要がある。
ｒ１＝ｒ２×ｔ１２
ａ１＝ａ２×ｔ１
ここで、ｔ１は１より小さい値であるため、
ｒ１＜ｒ２
ａ１＜ａ２
を満たさなければならない。即ち第一組の反射率は第二組の反射率より小さく、第一組の吸収率は第二組の吸収率よりも小さくなければならない。第一組の透過率ｔ１を４０％以上とすると、この関係を満たすことが容易になり好ましい。
【００３８】
第一組の反射率、吸収率と、第二組の反射率、吸収率を異なる値に設定する方法として、第一組と第二組の膜厚を変える方法がある。第一組の膜厚を第二組の膜厚よりも薄く設定すると、上記の関係式を満たすことができる。このとき第二組の透過率を略０（ゼロ）にすると第二組の反射率、吸収率をより大きくすることが可能になり好ましい。
一方、信号強度の点からｒ１＜ｒ２を満たす必要があるが、ａ１≧ａ２であっても第一組と第二組の記録感度をほぼ同等にする方法がある。それは第二組の光吸収層の融点を第一組の光吸収層の融点よりも低くして少ない吸収率でも記録が可能となるようにする方法である。この方法によれば第二組の吸収率が低くても記録可能になる温度が低いため、第一組と同じパワーのレーザ光照射で記録が可能になる。融点を変える方法としては、光吸収層の組成を変えるといった方法がある。
上記のように、一方の側からレーザ光を入射して２組の各々の光吸収層に対して情報の記録再生を行う場合、本発明のような媒体は、記録感度が良好であるため光吸収層自身の吸収率を従来の媒体のように大きくする必要がなく、反射率を大きくとることができる。光吸収層として高反射率かつ低融点の材料を選べば更にこの効果が高い。
【００３９】
光吸収層や第一の層を、スパッタ法、蒸着法、スピンコート法などによって成膜すると、各層の基板側と反対の面が、基板の形状と異なる場合がある。特に、スピンコート法によって成膜すると、基板に形成されたグルーブや凹凸ピットが埋まってしまう傾向があり、基板形状と、基板と反対側の膜の形状とが大きく異なる。
前述した３層構造を内側にはさむ形で２枚の基板を貼り合わせた構造の媒体に対し、一方から光を入射して両方の光吸収層に記録再生を行う場合、第一組は光入射側の面が基板面であり、第二組は光入射側の面が基板面と反対側の面であるため、同一の基板を使用すると、基板に予め形成された溝又はピットに関わるパラメータ、即ち、プッシュプル信号、デバイデッドプッシュプル信号、プリピットの信号振幅などが、第一組と第二組とで異なってしまう。そこで、第一組を担持する基板と第二組を担持する基板の溝形状、ピット形状を変えてやれば溝又はピットに関わるパラメータを揃えることが可能になる。
【００４０】
次に、本発明に係る光記録媒体（ディスク）の製造工程の一例のフローチャートを図４に示す。各工程は公知であるが、簡単に説明すると以下の通りである。
Ｓ１：ガラス円盤を研磨、洗浄する。
Ｓ２：シランコートを行う。
Ｓ３：ガラス円盤上にフォトレジストをスピンコートし、所定の膜厚を有す
るレジスト層を形成する。
Ｓ４：溶剤をとばすためプリベークを行う。
Ｓ５：集光レンズを介してレジスト層にレーザーを照射する（カッティン
グ）。
Ｓ６：この露光済みガラス円盤を現像処理する。
Ｓ７：レジストをＴｇ以上に加熱し溝形状を整形する（第一ベーク）。
Ｓ８：パターンの固化のためベークを行う（第二ベーク）。
Ｓ９：蒸着、メッキを行う。
Ｓ１０：ガラス円盤の凹凸面に金属膜を形成し、該金属膜を剥離することによ
りスタンパを作成する。
Ｓ１１：スタンパを用いて射出成形を行い、所定の膜厚を有するレプリカを形
成する。
Ｓ１２：必要に応じて透明基板の片面にスピンコート法によりハードコート層
を形成する。
Ｓ１３：透明基板のもう一方の片面にスパッタ法により第一の層を形成する。
Ｓ１４：第一の層の上にスピンコート法により光吸収層を形成する。
Ｓ１５：光吸収層の上にスパッタ法により第二の層を形成する。
Ｓ１６：必要に応じて保護層などの他の層を積層し、ディスク単板とする。
（単板のままで使用する場合）
Ｓ１７：必要に応じて保護層などの他の層を積層して得られる単板ディスクを
２枚貼り合わせて両面ディスクとする。
Ｓ１８：ディスクをカートリッジに収納する。
Ｓ１９：特性の評価を行う。
このフローチャートにおいて、Ｓ７とＳ８の工程は同時に行うこともできる。また、Ｓ７工程の溝形状の整形は、加熱温度９０〜１８０℃、時間５〜９０分の範囲から任意に選択できる。
【００４１】
【実施例】
以下、実施例により本発明を具体的に説明するが、本発明はこれらの実施例により限定されるものではない。特に実施例では、ディスク状光記録媒体を対象としているが、本発明は、例えばカード状、スティック状、テープ状など、他の形態の光記録媒体にも応用できることは勿論である。
これらの実施例から、本発明の光記録媒体の層構成と記録原理が、青色レーザ波長対応の有機材料からなる光記録媒体、更には高変調度が確保できる光記録媒体の実現に非常に有効であることが分る。
【００４２】
実施例１
図１及び図２に示すプリフォーマットパターンを有するポリカーボネート基板上に、次に示す材料を用いて膜厚１００ｎｍの第一の層、膜厚８０ｎｍの第二の層をスパッタ法により成膜した。
・第一の層（カッコ内の数値は、熱伝導率Ｗ／ｍ・ｋ　ａｔ３００ｋ）
ＳｉＯ_２（１．３８）、Ａｌ_２Ｏ_３（４６）、Ｔｅ（３．９６）、Ｇｅ
（５９．９）、ＭｇＯ（６０）の何れか一つ
・第二の層（カッコ内の数値は、熱伝導率Ｗ／ｍ・ｋ　ａｔ３００ｋ）
Ａｇ（４２７）、Ａｕ（３１５）、Ａｌ（２３７）の何れか一つ
上記第一の層と第二の層の熱伝導率の比は、何れの組み合わせについても３〜３１０倍の範囲内にあり、第二の層の方が熱伝導率が高い。
なお、第二の層を形成する前に、第一の層の上に、下記〔化２〕で示される基本骨格を有し、中心金属ＭがＶＯ、Ｚｎ、Ｐｄ、Ｃｏの何れかであり、４個のＲがＣ_６Ｈ_６−（ＣＦ_３）_２Ｃ−Ｏ−である４種のフタロシアニン化合物の等量混合溶液をスピンコート法により成膜し（平均膜厚１００ｎｍ）光吸収層を形成した。
次に、第二の層の上に大日本インキ化学工業社製のＳＤ１７００（熱伝導率１．０以下）を膜厚５μｍで積層し保護層とした。
【化２】

【００４３】
上記光記録媒体に対し、パルステック工業社製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、以下の条件で記録を行なった。第一の層にＴｅを用い、第二の層にＡｇを用いた場合の結果を図３に示す。

この光記録媒体では、光吸収層に１０個以上のφ＝２μｍのマイクロポア、４個のφ＝５μｍのマイクロポア、１個のφ＝１０μｍのマイクロポアが存在し、この影響により、２２５μｍ^２の範囲で、平均膜厚より平均膜厚の２％以上薄い部分があったが、プレヤーでエラー訂正され良好に再生することができた。
また、マイクロポアが存在しない部分でも島状に平均膜厚より平均膜厚の２％以上薄い部分があることが確認できた。この部分は連続気泡ではなく、独立気泡となっていた。
【００４４】
第一の層と第二の層の熱伝導率の比に関して、３〜３１０倍の範囲外の場合、例えば、第一及び第二の層に同じ材料を用いた場合（相対比＝１）は、第一又は第二のどちらかの層に光吸収層の色素が選択的に癒着することがなくなり、特に反射を決定する界面での色素の変質が少なくなり、光学的特性の変化が小さくなった。
また、無機材料含有層を用いた系で３１０倍を越えた場合、例えば、第一の層をガラス（Ｐｙｒｅｘ７７４０、熱伝導率＝１．１０Ｗ／ｍ・ｋ）、第二の層をＡｇとした場合（相対比＝３８８）では、色素層が変質してＡｇに優先的に癒着し、光学的特性の変化は得られるが、無機材料含有層である第一の層が堅いために、熱により亀裂、剥離などの問題が起きた。
【００４５】
フタロシアニンからなる光吸収層の膜厚は、１０〜１００ｎｍの範囲で任意に選定できる。１０ｎｍより薄いと光吸収量が少なくなり、良好な記録が行われなかった。また、１００ｎｍ以上では吸収率が高くなって反射率が不足し、更に、体積が大きくなり過ぎ、記録ピットを形成することができなかった。
上記の光学的特性は、フタロシアニンのＢ帯の分子吸光係数εを用いて、その強度をｌｏｇ１０εで表した場合、３．５以上の値が必要であった。３．５より小さい場合は、膜厚を厚くしても吸収が不純分であり、良好な記録を行うことができなかった。
また、光吸収層に隣接する第一、第二の層の熱伝導率は、Ｇｅの５９．９（Ｗ／ｍ・ｋ　ａｔ３００ｋ）以下である必要がある。熱伝導率が６０．０（Ｗ／ｍ・ｋ　ａｔ３００ｋ）のＭｇＯを用いた場合、熱伝導率が高いために良好な記録ができなかった。
また、第一の層に用いたＴｅは、保存性を向上するために酸化又は窒素化すると良い。その方法はＴｅを酸素又は窒素存在下でスパッタするか、Ｔｅ成膜後、大気中で３時間程度放置することにより達成できる。
酸素又は窒素存在下でスパッタする場合は、その含有量はアルゴン量１００に対して５〜３０％の範囲が好適であった。
【００４６】
実施例２
図１及び図２に示すプリフォーマットパターンを有するポリカーボネート基板上に、次に示す材料を用いて膜厚５０ｎｍの第一の層、膜厚９０ｎｍの第二の層をスパッタ法により成膜した。
・第一の層：Ｂｉ_１５Ｔｅ_８５、ＳｉＣ、Ａｇ_６０Ｓｂ_４０、Ａｇ_６０Ｃｕ_４０、Ｇｅ_１５Ｔｅ_８５、Ｇｅ_１５Ｓｂ_８５、Ａｕ_７０Ｂｉ_３０の何
れか一つ
・第二の層：Ａｇ
なお、第二の層を形成する前に、第一の層の上に実施例１と同じ〔化２〕で示される色素４種の混合物からなる有機材料層をスピンコート法によって成膜し（平均膜厚１００ｎｍ）、光吸収層を形成した。
その他の層は実施例１と同様にして成膜した。
以上の様にして作製した追記型光記録媒体に対して、実施例１と同様の記録を行ったところ、明瞭な信号が得られた。
【００４７】
実施例３
図１及び図２に示すプリフォーマットパターンを有するポリカーボネート基板上に、第一の層として膜厚１５ｎｍのＴｅをスパッタ法で成膜し、その上に下記〔化３〕のシアニン色素と下記〔化４〕のメロシアニン色素の混合物からなる有機材料層をスピンコート法によって成膜し（平均膜厚１００ｎｍ）、光吸収層を形成した。
この光吸収層上に、スパッタ法によりＡｇからなる膜厚８０ｎｍの第二の層を積層した。
更に、この第二の層上に大日本インキ化学工業社製のＳＤ１７００（熱伝導率１．０以下）を膜厚５μｍで積層し保護層とした。
以上の様にして作製した追記型光記録媒体に対して、実施例１と同様の記録を行ったところ、短マーク、長マークとも、変調度が充分大きく非常に明瞭な信号が得られた。
【化３】

【化４】

【００４８】
実施例４
図１及び図２に示すプリフォーマットパターンを有するポリカーボネート基板上に、第一の層として酸素を含有した膜厚１５ｎｍのＴｅをスパッタ法で成膜し、その上にバナジル５，１４，２３，３２−テトラフェニル−２，３−ナフタロシアニンをスピンコート法によって成膜し（平均膜厚１００ｎｍ）、光吸収層を形成した。
この光吸収層上に、スパッタ法によりＡｇを材料とする膜厚８０ｎｍの第二の層を積層した。
更に、この第二の層上に大日本インキ化学工業社製のＳＤ１７００（熱伝導率１．０以下）を膜厚５μｍで積層し保護層とした。
以上の様にして作製した追記型光記録媒体に対して、実施例１と同様の記録を行ったところ、短マーク、長マークとも、変調度が充分大きく非常に明瞭な信号が得られた。
【００４９】
実施例５
図１及び図２に示すプリフォーマットパターンを有するポリカーボネート基板上に、第一の層として窒素を含有した膜厚１０ｎｍのＴｅをスパッタ法で成膜し、その上に下記一般式〔化５〕で示されるアゾ染料からなる有機材料層をスピンコート法によって成膜し（平均膜厚１００ｎｍ）、光吸収層を形成した。
この光吸収層上に、スパッタ法によりＡｇを材料とする膜厚９０ｎｍの第二の層を積層した。
更に、この第二の層上に大日本インキ化学工業社製のＳＤ１７００（熱伝導率１．０以下）を膜厚５μｍで積層し保護層とした。
以上の様にして作製した追記型光記録媒体に対して、実施例１と同様の記録を行ったところ、短マーク、長マークとも、変調度が充分大きく非常に明瞭な信号が得られた。
【化５】

（式中、Ｒ_１はフェニル基、Ｒ_２〜Ｒ_６は水素原子を表す。）
【００５０】
実施例６
光吸収層として、次に示す色素の何れかを用いた点以外は、実施例１と同様にして追記型光記録媒体を作製し、実施例１と同様の記録を行ったところ、何れも良好な信号が得られた。
１，４−ビス（５′−フェニルオキサゾール−２′−イル）ベンゼン、１，４−ビス（４′−メチル−５′−フェノキサゾール−２′−イル）ベンゼン、４，４′−ビス（２′−スルホスチリル）ビフェニル、２，５−ビス（５′−メチルベンゾオキサゾール−２′−イル）チオフェン、ＮＫ１３４２、ＮＫ１９７７、ＮＫ１８８６、ＮＫ１８１９、ＮＫ１３３１、ＮＫ１８３７、ＮＫ８６３、ＮＫ３２１２、ＮＫ８８、ＮＫ３９８９、ＮＫ１２０４、ＮＫ７２３、ＮＫ３９８４（何れも日本感光色素社製）、
【化６】

【化７】

【化８】

【化９】

【化１０】

【化１１】

【化１２】

【００５１】
実施例７〜１６
射出成形により、表面に下記のようなトラックピッチ、グルーブ幅、グルーブ深さのスパイラル状のプレグルーブが形成された、直径１２０ｍｍ、厚さ１．１ｍｍのポリカーボネート基板上に、スパッタ法により膜厚６０ｎｍのＡｇからなる第一の層を設け、その上に下記〔化１３〕のフタロシアニン色素をＴＨＦ（テトラヒドロフラン）２．６ｇ、エチルシクロヘキサン６．２ｇ、ＩＰＡ（イソプロピルアルコール）２．４ｇ、１−メトキシ−２−プロパノール４．６ｇの混合溶媒に溶解した塗布液をスピンコート法により塗布し、光吸収層（プレグルーブ内の厚さ約３５〜４５ｎｍ）を形成した。

【化１３】

〔式中、ＭはＶＯであり、４個のＲはＣ_６Ｈ_６−（ＣＦ_３）_２Ｃ−Ｏ−である。〕
次いで、その上に第二の層として厚さ約４０ｎｍのＺｎＳ−ＳｉＯ_２層をスパッタにより形成した。
なお、光吸収層の波長λ＝４０５ｎｍにおける吸光度は０．２とした。
更にその上に、ＵＶ硬化接着剤（大日本インキ化学工業社製、商品名：ＳＤ−３４７）をスピンコート法により２００ｒｐｍで塗布し、３００ｒｐｍから４０００ｒｐｍまで変化させながら全面に接着剤を広げた後、０．０７ｍｍ厚のポリカーボネート樹脂シート（帝人社製、商品名：ピュアエース）からなるカバー層を重ね、紫外線を照射して接着剤を硬化させカバー層を貼り合わせて光記録媒体を作製した。
【００５２】
上記光記録媒体に対し、パルステック工業社製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．８５）を用いて、下記の条件で記録を行なったところ、短マーク、長マーク共に、変調度が充分大きく、非常に明瞭な信号が得られた。

上記〔化１３〕の色素の光吸収スペクトルを図５に示す。図から明らかなように、波長λ＝３５０ｎｍ付近に副吸収の極大を有する。
比較のため、副吸収の極大が波長λ＝３２０ｎｍ付近に存在するフタロシアニン色素の光吸収スペクトルを図６に示す。
なお、図５、図６の吸光度は、石英基板上に材料をスピンコート又はスパッタし、そのサンプルを島津製作所社製ＵＶ−２５００（ＰＣ）ＳＧＬＰを用いて測定した値である。
副吸収の極大が３３０ｎｍより長波長にある色素を用いた実施例７の場合、ジッタは８．８％と良好であった。これに対して、副吸収の極大が３３０ｎｍより短波長にある図６のフタロシアニン色素を用いて実施例７と同様にして作製した光記録媒体の場合は、記録感度が悪く、短いピットを形成することができなかった。
従って、波長４０５ｎｍで記録を行う場合、色素の吸収は３３０ｎｍ以上の長波長側に存在する必要がある。なお、実施例８〜１６の光記録媒体は何れも実施例７と近似したアイパターンとジッタを示した。
また、波長４０５ｎｍで記録を行う場合、副吸収の極大が４００ｎｍより長波長側にある場合は、吸収が大きくなり過ぎるために良好な記録を行うことができなかった。
以上の結果から、第一の光吸収層は、波長λが３３０〜４００ｎｍの範囲に吸収極大を有することが好適である。
【００５３】
一方、記録再生消去に用いる波長をλ１として、λ１±１０ｎｍの範囲の測定光を基板側より入射して得られる第一の光吸収層の反射率が７％以上あれば、干渉効果により高いコントラストが得られる。
同様に、記録再生消去に用いる波長をλ１として、λ１±１０ｎｍの範囲の測定光を光吸収層側より入射して得られる第一の光吸収層の反射率が８％以上であることが好ましい。
なお、上記記録再生消去に用いる波長λ１は、現状では３９０〜４２０ｎｍの範囲が一般的であり、更に詳しくは、７８０ｎｍのＳＨＧ（非線形効果）を利用した場合は３９０〜４００ｎｍ、ブルーレーザを使用した場合は４００〜４１０ｎｍ、８３０ｎｍのＳＨＧを使用した場合は４１０〜４２０ｎｍである。
ブルーレーザを使用した場合は、波長λ１＝３９５〜４１５ｎｍの範囲の測定光を基板側より入射して得られる第一の光吸収層の反射率が７％以上であることが必要であり、また、波長λ１＝３９５〜４１５ｎｍの範囲の測定光を光吸収層側より入射して得られる第一の光吸収層の反射率が８％以上であることが好ましい。
更に、第一の光吸収層の膜厚を、記録再生に用いる波長において反射極大を示す膜厚より厚くすることにより、記録前後のコントラスト比を大きく取ることができる。
図７〜図８に実施例７の記録再生消去に用いる波長での反射を有する場合のスペクトルを示す。図中のＲｇは基板側からの測定光を照射した場合、Ｒｌは膜面側から光を照射した場合である。
図７、図８の反射率は、石英基板上に材料をスピンコート又はスパッタし、そのサンプルを島津製作所社製ＵＶ−２５００（ＰＣ）ＳＧＬＰを用いて測定した絶対反射率である。
【００５４】
実施例１７
図１及び図２に示すプリフォーマットパターンを有するポリカーボネート基板上に、ＺｎＳ・ＳｉＯ_２からなる膜厚１５０ｎｍの第一の層、Ｉｎ_２Ｏ_３・ＺｎＯ_２からなる膜厚５０ｎｍの第二の層をスパッタ法により成膜した。
なお、第二の層を形成する前に、第一の層の上に、バナジル５，１４，２３，３２−テトラフェニル−ナフタロシアニンをスピンコート法によって成膜し（平均膜厚１００ｎｍ）、光吸収層を形成した。
その他の層は実施例１と同様にして成膜した。
以上の様にして作製した追記型光記録媒体に対して、実施例１と同様の記録を行ったところ、明瞭な信号が得られた。
また、本実施例の媒体は、記録後、２００℃で３０分以上ベークすることにより記録を消去することができた。
【００５５】
【発明の効果】
本発明１〜２０によれば、青色レーザ波長領域、特に４０５ｎｍ近傍の波長領域であっても記録可能な、有機材料からなる光記録媒体、また、高密度化が図れ、変調度が大きく、更には、記録再生波長の変動に対し、記録感度、変調度、ジッタ、エラー率といったような記録特性や、反射率等の変化が少なく、保存性にも優れた光記録媒体及びその製造方法を提供できる。
【図面の簡単な説明】
【図１】本発明の光記録媒体の層構成の一例を示す要部拡大断面図。
【図２】本発明の光記録媒体（光ディスク）の構成の一例を示す斜視図。
【図３】実施例１の光記録媒体に対して記録を行なった結果を示す図。
【図４】本発明に係る光ディスク製造のフローチャートを示す図。
【図５】〔化１３〕の色素の光吸収スペクトルを示す図。
【図６】副吸収の極大が波長λ＝３２０ｎｍ付近に存在するフタロシアニン色素の光吸収スペクトルを示す図。
【図７】実施例７の記録再生消去に用いる波長での反射を有する場合のスペクトルを示す図（基板側からの測定光を照射した場合）。
【図８】実施例７の記録再生消去に用いる波長での反射を有する場合のスペクトルを示す図（膜面側から光を照射した場合）。
【符号の説明】
１　透明基板
１ａ　センタ孔
２　プリフォーマットパターン
２ａ　案内溝
２ｂ　プリピット
２ｃ　ランド部
３　第一の層
４　光吸収層
５　第二の層
１０　保護層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium on which information can be recorded and reproduced by a laser, and a method for manufacturing the same.
[0002]
[Prior art]
The development of a blue laser capable of recording at a very high density is progressing rapidly, and a write-once optical recording medium corresponding to the development is being developed.
Patent Documents 1 to 5 disclose, for example, organic materials compatible with a blue laser. However, in these publications, only the spectra of the solution and the thin film are measured in the examples, and there is no description about recording / reproducing.
In Patent Documents 6 to 8, although recording is described in Examples, the recording wavelength is 488 nm, and there is no description on recording conditions or recording density, only that a good recording pit was formed. It is.
In Patent Document 9, although recording is described in Examples, the recording wavelength is 430 nm, and there is no description about recording conditions or recording density, but only a statement that a good degree of modulation was obtained. .
Patent Documents 10 to 19 include examples in which recording is performed at a recording wavelength of 430 nm and an NA of 0.65 in Examples, but the recording density is as low as 0.4 μm (the recording density is equivalent to that of DVD).
Patent Document 20 describes a recording / reproducing wavelength of 405 to 408 nm, but does not specifically describe a recording density, and is a low recording density condition of recording a 14T-EFM signal.
[0003]
Further, regarding the layer configuration and recording method different from the conventional CD and DVD optical recording media, the following technologies are disclosed.
Patent Document 21 discloses a technique in which recording is performed by changing the extinction coefficient (absorption coefficient in the present invention) of a saturable absorbing dye in a structure of a substrate / a layer containing a saturable absorbing dye / a reflective layer.
Patent Document 22 discloses a technique in which recording is performed by discoloring or deforming a metal vapor deposited layer by heat generated by the light absorbing layer in a configuration of a substrate / metal vapor deposited layer / light absorbing layer / protective sheet. .
Patent Document 23 discloses a technique of performing recording by changing the film thickness of a recording layer and changing the depth of a groove in a configuration of a substrate / dielectric layer / recording layer including a light absorber / reflection layer. .
Patent Document 24 discloses a technique of performing recording by changing the thickness of a recording layer by 10 to 30% in a configuration of a substrate / a recording layer including a light absorber / a metal reflection layer.
[0004]
Patent Document 25 discloses a technique of performing recording by increasing the groove width of a substrate by 20 to 40% with respect to an unrecorded portion in a configuration of a substrate / a recording layer containing an organic dye / a metal reflective layer / a protective layer. It has been disclosed.
Patent Document 26 discloses a technique of performing recording by forming a bubble by deforming a metal thin film in a configuration of a substrate / intermediate layer / metal thin film.
Patent Literature 27 discloses a technique in which heat is released to an insulating film to correct a recording portion by using a structure of a substrate / insulating layer / cyanine recording film / reflective film / protective film.
Patent Document 28 discloses that a recording auxiliary layer is deformed into a concave shape, and a light reflecting layer is deformed into a concave shape along with the deformation of the recording auxiliary layer in a configuration of a substrate / a light absorbing layer / a recording auxiliary layer / a light reflecting layer. Discloses a technique for performing recording.
Patent Document 29 discloses that a recording auxiliary layer is formed in a concave shape with a configuration of a substrate / a light absorbing layer / a porous recording auxiliary layer / a light reflecting layer or a substrate / a porous recording auxiliary layer / a light absorbing layer / a light reflecting layer. There is disclosed a technique of performing recording by deforming the light reflection layer in a concave shape along with the deformation of the recording auxiliary layer.
[0005]
Patent Document 30 discloses a configuration in which a substrate / porous light absorbing layer / light reflecting layer has a configuration in which the light absorbing layer is deformed concavely and the light reflecting layer is deformed concavely along the deformation of the light absorbing layer. Is disclosed.
Patent Literature 31 discloses a configuration of a substrate / a recording layer containing an organic dye / a recording auxiliary layer, in which the recording auxiliary layer and the organic dye are compatible with each other and the absorption spectrum of the organic dye is shifted to a shorter wavelength side to perform recording. Performing techniques are disclosed.
However, none of the above techniques aims at realizing an optical recording medium in the blue laser wavelength range, and is not a layer configuration or a recording method effective in the blue laser wavelength range.
[0006]
[Patent Document 1]
JP 2001-181524 A
[Patent Document 2]
JP 2001-158865 A
[Patent Document 3]
JP 2000-343824 A
[Patent Document 4]
JP 2000-343825 A
[Patent Document 5]
JP 2000-335110 A
[Patent Document 6]
JP-A-11-221964
[Patent Document 7]
JP-A-11-334206
[Patent Document 8]
JP 2000-43423 A
[Patent Document 9]
JP-A-11-58955
[Patent Document 10]
JP 2001-39034 A
[Patent Document 11]
JP-A-2000-149320
[Patent Document 12]
JP 2000-113504 A
[Patent Document 13]
JP 2000-108513 A
[Patent Document 14]
JP 2000-222772 A
[Patent Document 15]
JP 2000-218940 A
[Patent Document 16]
JP-A-2000-222771
[Patent Document 17]
JP 2000-158818 A
[Patent Document 18]
JP 2000-280621 A
[Patent Document 19]
JP 2000-280620 A
[Patent Document 20]
JP 2001-146074 A
[Patent Document 21]
JP-A-7-304258
[Patent Document 22]
JP-A-8-83439
[Patent Document 23]
JP-A-8-138245
[Patent Document 24]
JP-A-8-2977838
[Patent Document 25]
JP-A-9-198714
[Patent Document 26]
Japanese Patent No. 2506374
[Patent Document 27]
Japanese Patent No. 250667
[Patent Document 28]
Japanese Patent No. 2591939
[Patent Document 29]
Japanese Patent No. 2591940
[Patent Document 30]
Japanese Patent No. 2591941
[Patent Document 31]
Japanese Patent No. 2982925
[0007]
[Problems to be solved by the invention]
In view of the above-mentioned prior art, the present invention provides an optical recording medium made of an organic material that can record even in a wavelength region near 405 nm in particular, a high density, a high degree of modulation, jitter, and an error rate. It is an object of the present invention to provide an optical recording medium which has little change in recording characteristics, reflectance and the like, and is excellent in storability and a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
The above-mentioned object is solved by the following inventions 1) to 20) (hereinafter, the present invention 1 to 20).
1) A light absorption layer containing at least one dye and having a thickness of 5 to 200 nm has a three-layer structure sandwiched between a first layer and a second layer, and includes a first layer and a second layer. An optical recording medium, wherein the layer contains a metal material and / or an inorganic material.
2) When the first layer and the second layer contain a metal material, the relative thermal conductivity of the first layer is 3 to 310 times the thermal conductivity of the second layer. The optical recording medium according to 1), wherein
3) The optical recording medium according to 1) or 2), wherein the light absorbing layer has an absorption maximum in a wavelength range of 330 to 400 nm.
4) Assuming that the wavelength used for recording / reproduction / erasing is λ1, the reflectance of the light absorbing layer obtained by irradiating the measurement light from the substrate side in the range of λ1 ± 10 nm is 7% or more. The optical recording medium according to any one of the above).
5) Assuming that the wavelength used for recording / reproducing and erasing is λ1, the reflectance of the light absorbing layer obtained by irradiating the measuring light from the light absorbing layer side in the range of λ1 ± 10 nm is 8% or more 1). An optical recording medium according to any one of claims 1 to 3,
6) The optical recording medium according to 4) or 5), wherein the wavelength λ1 is 390 to 420 nm.
7) The optical recording medium according to 6), wherein the wavelength λ1 is 405 nm.
8) The dye is at least one selected from the group consisting of cyanine, phthalocyanine, naphthalocyanine, merocyanine, azo, squarylium, porphyrin, polyene, basestyryl and formazan chelate dyes. The optical recording medium according to any one of 1) to 7), wherein
9) The optical recording medium according to 8), wherein the dye is a material having a porphyrin ring as a basic skeleton.
10) The optical recording medium according to 9), wherein the material having a porphyrin ring as a basic skeleton contains a tetraazaporphyrin ring.
11) The optical recording medium according to 10), wherein the material containing a tetraazaporphyrin ring is a phthalocyanine dye.
12) In the case where the phthalocyanine dye shows, in a solution state, absorption in the B band caused by the porphyrin ring between wavelengths λ = 300 to 400 nm, and the intensity is represented by log10ε (ε is a molecular absorption coefficient). The optical recording medium according to 11), wherein the number is 5 or more.
13) The optical recording medium according to 11) or 12), wherein the thickness of the light absorbing layer is 10 to 100 nm.
14) The optical recording medium according to any one of 1) to 13), wherein the light absorbing layer further contains an organic substance having a decomposition temperature of 160 to 500 ° C.
15) The optical recording medium according to any one of 1) to 14), wherein the inorganic material contains an inorganic oxide or an inorganic carbide as a main component.
16) The optical recording medium according to 15), wherein the inorganic oxide or the inorganic carbide is any oxide or carbide of In, Si, Sn, and Zn.
17) The optical recording medium according to any one of 1) to 16), wherein one of the first and second layers has a thermal conductivity of 59.9 (W / m · kat 300 k) or less. .
18) The optical recording medium according to any one of 1) to 17), wherein one of the first and second layers is made of silver, copper, or aluminum.
19) The light according to any one of 1) to 18), wherein one of the first and second layers contains Te, or Te and another metal, and also contains oxygen and / or nitrogen. recoding media.
20) At the time of forming the first or second layer containing Te or other metal and containing oxygen and / or nitrogen, while introducing oxygen and / or nitrogen into the atmosphere, And another metal is sputtered, or Te is introduced without introducing oxygen and / or nitrogen, or a film is formed by sputtering Te and another metal to take in nitrogen and oxygen in the atmosphere. 19) The method for producing an optical recording medium according to the above item 19).
[0009]
Hereinafter, the present invention will be described in detail.
Conventionally, the light absorption layer absorbs light to perform light-to-heat conversion, and the heat is used to decompose, degrade, or deform the material of the light absorption layer to perform recording. Most of the heat is used for recording. On the other hand, the optical recording medium of the present invention is characterized in that heat used for recording is controlled by two adjacent layers.
Further, in the conventional optical recording medium using many organic dyes, since contrast was obtained by the interference effect using reflection, high power was not required and high contrast could be obtained in a small recording range. However, a limitation has been imposed on the use of a material having a high reflectivity as the light absorbing layer material.
On the other hand, in the optical recording medium of the present invention, even when a high power is used for recording, by controlling the heat by releasing the heat to the adjacent layer, the recording with a small recording range and high contrast can be achieved. Therefore, the organic light absorbing layer does not need to have a high reflectance as in the related art.
Further, in the dye material, since a transition other than the transition from HOMO to LUMO is used, a large number of absorption regions can be used for recording, and the absorption wavelength of the dye matches the wavelength of the laser beam used for recording / reproduction. It is easy to adjust.
[0010]
An example of the configuration of the optical recording medium of the present invention will be described with reference to FIGS. FIG. 1 is an enlarged sectional view of an essential part showing an example of a layer configuration of an optical recording medium of the present invention, and FIG. 2 is a perspective view showing an example of a configuration of an optical recording medium (optical disc) of the present invention.
As is clear from these figures, this optical recording medium has a transparent substrate 1, a first layer 3, a light absorbing layer 4, a second layer 5, and a protective layer having a fine irregular preformat pattern 2 on one side. It has a configuration in which the layers 10 are stacked in this order.
[0011]
The transparent substrate 1 is made of a material which maintains transparency with respect to a laser, has an excellent impact strength, and easily expands, deforms or deteriorates at a temperature of 80 to 200 ° C.
For example, a transparent resin material (preferably having a glass transition temperature Tg of 100 to 200 ° C.) such as polycarbonate, polymethyl methacrylate, polymethyl pentene, epoxy resin, polyester, or amorphous polyolefin is formed into a desired shape, and the desired shape is formed on one surface thereof. Any known transparent materials such as those obtained by transferring a preformat pattern or a transparent resin plate having a desired preformat pattern transferred onto one surface of a transparent ceramic plate such as glass formed in a desired shape. A substrate can be used. As shown in FIG. 2, a transparent substrate 1 constituting a disc-shaped optical recording medium (hereinafter, referred to as an optical disc) is formed in a disc shape having a center hole 1a in the center. Note that the transparent substrate 1 can be manufactured by a known method.
A pregroove for guiding incident laser light during recording or reproduction is formed on the surface of the substrate, and its depth is desirably 10 to 200 nm. When the depth of the pre-groove is less than 10 nm, the reflectivity is greatly increased due to the expansion of the substrate after recording, and the recording signal has much noise. When the depth exceeds 200 nm, the pre-groove is deep in the light absorbing layer. Therefore, it is difficult to form a uniform film.
[0012]
The preformat pattern 2 includes at least a beam guide for causing a recording / reproducing laser beam to follow a recording track.
In the example of FIGS. 1 and 2, the beam guide portion is configured to have a spirally or concentrically formed guide groove 2 a concentric with the center hole 1 a, and along the guide groove 2 a, an address pit or a clock is formed. Pre-pits 2b such as pits are formed.
When the prepit 2b is formed on the guide groove 2a so as to be optically distinguishable, the guide groove 2a and the prepit 2b are formed at different depths as shown in FIG. I do. When the pre-pits 2b are formed between adjacent guide grooves 2a, they can be formed at the same depth.
In addition, instead of the guide groove 2a, a wobble pit can be formed along the recording track as the beam guide. Alternatively, the pre-pits 2b may be omitted, and may be formed only by the guide grooves.
[0013]
Examples of the material of the first layer 3 include Fe, Ti, Zr, Ta, Cr, Mo, W, Ni, Rh, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Si, Ge, Te, At least one substance selected from the group consisting of Sn, Bi, Sb, Tl, Na, Ga, and Pt can be used. Various ceramic materials can also be used.
In particular, a material containing at least two types of elements as main components and having a melting point of 600 ° C. or less is preferable. For example, a material made of Bi, In, Pb, Sn, Te, Tl, Zn, Na, Ga, or the like is preferable. You can choose at least two of them. Specifically, In-Bi-based, Bi-Na-based, Pb-Bi-based, Sn-Bi-based, In-Pb-based, In-Sn-based, In-Tl-based, In-Zn-based, Sn-Pb-based, Combinations of Tl-Sn type, Zn-Sn type and the like are possible. Further, those having a eutectic composition with a melting point of 600 ° C. or lower and a content of the eutectic composition or a composition near the eutectic composition may be used.
[0014]
Furthermore, two kinds of elements are main components, and at least one element has a melting point of 600 ° C. or more, and the element has a eutectic composition with a melting point of 600 ° C. or less with another element, Materials in which the content of the two elements is a eutectic composition or a composition near the eutectic composition are more preferred. For example, Bi, In, Pb, Sn, Te, Tl, Zn, Na, Ga, Ag, Al, Ca, Ge, Sb, Si, Au, Cu, Ni, Ce, La, Mg, Pr, Pd, Pt, etc. At least two types can be selected from the materials consisting of: Specifically, Ag-Al system, Ag-Bi system, Ag-Ca system, Ag-In system, Ag-Pb system, Ag-Sb system, Ag-Sn system, Ag-Te system, Ag-Tl system, Al-Au system, Al-Cu system, Al-Ge system, Al-Si system, Al-Sn system, Al-Te system, Al-Zn system, Au-Bi system, Au-Ge system, Au-Pb system, Au-Sb system, Au-Sn system, Au-Si system, Au-Te system, Au-Tl system, Ni-Ce system, Cu-La system, Cu-Mg system, Cu-Pr system, Cu-Sb system, Combinations of Ga-Te, Ge-Te, Zn-Ge, In-Sb, Pb-Pd, Pt-Pb, Pb-Sb, Sb-Te, and Tl-Sb are possible. is there.
[0015]
As ceramics, Al ₂ O ₃ , MgO, BeO, ZrO ₂ , ZnO ₂ , UO ₂ , ThO ₂ Oxides such as simple oxides; SiO ₂ , 2MgO ・ SiO ₂ , MgO / SiO ₂ , CaO ・ SiO ₂ , ZrO ₂ ・ SiO ₂ , 3Al ₂ O ₃ ・ 2SiO ₂ 2MgO.2Al ₂ O ₃ ・ 5SiO ₂ , Li ₂ O ・ Al ₂ O ₃ ・ 4SiO ₂ Silicate-based oxides such as Al; ₂ TiO ₅ , MgAl ₂ O ₄ , Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , BaTiO ₃ , LiNbO ₃ , PZT [Pb (Zr, Ti) O ₃ ], PLZT [(Pb, La) (Zr, Ti)], double-oxide based oxides such as ferrite; SiN, Si ₃ N ₄ , Si _6-Z Al _Z O _Z N _8-Z , AlN, BN, TiN and other nitride-based non-oxides; SiC, B ₄ Carbide-based non-oxide such as C, TiC, WC; LaB ₆ , TiB ₂ , ZrB ₂ Boride-based non-oxides such as CdS, MoS ₂ Sulfide-based non-oxide such as MoSi ₂ For example, a silicide-based non-oxide such as amorphous carbon, graphite, and diamond can be used.
[0016]
Further, from Fe, Ti, Zr, Ta, Cr, Mo, W, Ni, Rh, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Si, Ge, Te, Sn, Bi, Sb and Tl It is desirable to contain oxides, sulfides, nitrides, and carbides of at least one substance selected from the group consisting of: Specific examples of the oxide include SiO and ZnO-SiO. _2, SiC, ZnO ₂ , In ₂ O ₃ -SnO ₂ , In ₂ O ₃ -Specific examples of sulfides, such as ZnS, specific examples of nitrides, such as SiN and AlN, and specific examples of carbides, such as TiC, ZnC, TaC, NbC, and TiC-TiO. _2, TaC-TaO _2, NbC-NbO ₂ And the like.
Among these, oxides and carbides of In, Si, Sn, and Zn are particularly preferable because of their high light transmittance and low absorbance (low light absorption). Here, the absorbance means the degree of light absorption of the material. When the absorbance of a material having reflection is measured by a spectroscope, the amount of light detected by the detector decreases due to reflection, and the apparent absorbance may increase. Is not taken into account, and only the amount of light absorbed by the material is taken as the absorbance.
On the other hand, for a material whose reflection is negligibly small, the absorbance calculated from the amount of light detected by the detector, that is, the value obtained from the analytical instrument can be directly used as the absorbance.
[0017]
Further, the first layer 3 may be formed of a material having a function as a reflective layer in some cases. Although there is no particular limitation on the material used, a metal material such as silver, copper, or aluminum or an alloy material containing these as a main component can be used. In particular, it is preferable to use silver or an alloy mainly containing silver. Here, “mainly composed of silver” means that the silver content is 80 to 100 atomic%, preferably 90 to 100 atomic%.
Aluminum can also be used because it is inexpensive and has been used in compact discs.
When a metal or alloy material is used, a film can be formed by a vacuum film forming method such as sputtering or vacuum evaporation. In this case, a technique is employed in which the degree of vacuum in the vacuum chamber is changed (for example, about 10 to 5 torr) to form a film having a different density or crystallization state, thereby increasing the reflectance of the first layer. You can also.
[0018]
Further, N and O can be added to various metals. N has the effect of reducing the crystal grain size and reducing noise when the first layer is a crystal. O exists as an oxide of at least one of the elements constituting the first layer, and has the effect of reducing the thermal conductivity of the first layer and improving the recording sensitivity. The addition amount is preferably 20 atomic% or less, particularly preferably 15 atomic% or less.
Further, when S, Se, or Sb is added, the oxidation resistance is improved. Oxidation resistance is further improved by including a large amount of these elements near the surface of the first layer. Note that Sb is listed as an element used in the first layer, but is used as an additive element only when Sb is not used as a main component of the first layer.
[0019]
The thickness of the first layer 3 is preferably 1 to 200 nm. If it is thinner than 1 nm, heat conduction is insufficient, and if it is thicker than 200 nm, the absorptance increases and the reflectivity decreases.
Preferably, the thickness is 8 to 14 nm when SiC is selected as the material, 10 to 40 nm when Ag is selected, and 1 to 10 nm when the Te alloy is selected.
Micropores may be present in the first layer, and a penetrating open cell type may be present.
[0020]
Examples of the dye material capable of forming the light absorbing layer 4 include polymethine dyes, anthraquinone dyes, cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, xanthene dyes, triphenylmethane dyes, pyrylium dyes, and azulene. Dyes, metal-containing azo dyes, azo dyes, benzobisazole dyes, naphthopyran dyes, merocyanine dyes, squarylium dyes, porphyrin dyes, polyene dyes, basestyryl dyes, and formazan chelate dyes. Can be.
Of these, cyanine, phthalocyanine, naphthalocyanine, merocyanine, azo, squarylium, porphyrin, polyene, basestyryl and formazan chelate dyes are preferably used.
In particular, as the phthalocyanine dye, a compound represented by the following formula 1 is preferable.
[0021]
Embedded image

[0022]
In the above formula, M is any of Cu, VO, Ni, H, Zn, Pd, Cd, Co, and Fe, and examples of R include those shown in Tables 1 to 8 below.
However, M in the compounds shown in Table 8 has an organic substituent as described in the table. In Tables 1 to 8, (1/4) means that one of the four Rs is a substituent thereof, and similarly (2/4) (3/4) The term (4/4) means that 2 to 4 substituents are present. Also, (1/3) means that one of the four Rs is hydrogen and one of the remaining three Rs is a substituent thereof. Similarly, (2/3) ) Means that two are its substituents. Those without the above-mentioned indication mean that all four Rs are the substituents.
[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

[Table 8]

[0023]
Alternatively, a dye material to which various quencher such as an aminium dye is added can be used. Furthermore, one in which one or more dye materials selected from the above dye material group are dispersed in a resin can also be used.
Examples of the resin material capable of dispersing the coloring material include an acrylic resin, a vinyl resin, a phenol resin, a fluororesin, a silicone resin, a polyamide resin, and a cellulose resin.
The light absorbing layer 4 is formed by spin-coating a solvent solution of a dye material selected from the dye material groups exemplified above. After filling the groove of the first layer formed corresponding to the groove-shaped preformat pattern 2 of the substrate with the dye material, a flat portion between the grooves (land between the preformat patterns 2 of the substrate) It can be formed by selectively removing the dye material attached to the flat portion formed corresponding to the portion 2c, exposing the surface of the first layer, and filling the groove only with the dye material. .
In addition, as a solvent of the coloring material, an alcohol-based solvent, a cellosolve-based solvent, or the like can be used.
[0024]
Further, the dye can be prevented from fading by containing a chelating material capable of taking bidentate coordination. Such chelating materials include inorganic acids, dicarboxylic acids, oxycarboxylic acids, dioxy compounds, oxioximes, oxyaldehydes and derivatives, diketones and similar compounds, oxyquinones, troborones, N-oxide compounds, Aminocarboxylic acids and similar compounds, hydroxylamines, oxines, aldimines, oxyazo compounds, nitrosonaphthols, triazenes, piuretes, formazans and dithizones, biqualides, glyoximes, diamines and similar compounds, Hydrazine derivatives, thioethers and the like can be mentioned.
Furthermore, derivatives having an imino group can also be used.
[0025]
When the first layer 3 has micropores, a solvent capable of forming a solution having a certain contact angle that does not enter the micropores must be selected as a solvent for forming the light absorbing layer 4. There is no particular limitation other than that.
Here, for a certain contact angle that does not enter the micropore, the required surface tension varies depending on the size of the micropore, and thus the value cannot be indicated by a numerical value. However, the area of a portion that is 2% or more of the average film thickness smaller than the average film thickness generated in the micropore portion after film formation is 225 μm. ² Is the upper limit and 225 μm ² Exceeding the range will cause problems such as tracking accuracy and error correction, so even if the solution penetrates into the micropore, if the penetration does not spread beyond the above range, a certain contact angle that will not enter the micropore Is determined to correspond to a solution having
[0026]
Examples of the solvent capable of forming a solution having a certain contact angle that does not enter the micropore include esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; dichloromethane; Chlorinated hydrocarbons such as dichloroethane and chloroform; amides such as dimethylformamide; hydrocarbons such as cyclohexane; ethers such as tetrahydrofuran, ethyl ether and dioxane; ethanol, n-propanol, isopropanol, n-butanol, diacetone alcohol and the like. Alcohols; Fluorinated solvents such as 2,2,3,3-tetrafluoropropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene Such as glycol ethers such as glycol monomethyl ether.
In addition, as these solvents, it is necessary to use those having a solubility of 5 mg / 1 ml or more of the dye used. Therefore, the dyes are used singly or in combination of two or more in consideration of the solubility of the dye used. In addition, various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be added to the coating solution as needed.
[0027]
Examples of the binder when a binder is used in combination as the material of the light absorbing layer 4 include natural organic high molecular substances such as gelatin, cellulose derivatives, dextran, rosin, and rubber; Hydrogen resin; vinyl resin such as polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride / polyvinyl acetate copolymer; acrylic resin such as polymethyl acrylate and polymethyl methacrylate; polyvinyl alcohol, chlorinated polyethylene, epoxy Examples include synthetic organic polymers such as resins, butyral resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol / formaldehyde resins.
The amount of the binder used is generally in the range of 0.01 to 50 times (mass ratio), preferably in the range of 0.1 to 5 times (mass ratio) based on the dye.
The concentration of the coating solution thus prepared is generally in the range of 0.01 to 10% by mass, preferably in the range of 0.1 to 5% by mass.
Examples of the application method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method.
[0028]
Further, as a material of the light absorbing layer, at least one selected from the group consisting of aromatic compounds, aliphatic compounds, amides, esters, amines, ureas, sulfur compounds, and hydroxy compounds can also be used.
Further, the light absorbing layer desirably contains an organic substance having a decomposition temperature of 160 to 500 ° C. Such an organic substance may be appropriately selected from the above exemplified compounds.
If the decomposition temperature is lower than 160 ° C., it is affected by the environment and causes a problem in storage stability. On the other hand, if the decomposition temperature is higher than 500 ° C., it is not possible to induce the decomposition of the material at the time of recording, and the recording sensitivity is lowered.
[0029]
On the other hand, the light absorption layer 4 absorbs light, deforms, degrades, or changes optically.
The first layer, the second layer, the substrate, and the protective layer may be deformed or deteriorated as the light absorbing layer is deformed or deteriorated.
A metal such as Ag, Cu, or Al is selected for the first layer, and SiC or SiO is used for the second layer. ₂ When a dielectric material such as Te or a metal such as Te is selected, the thermal conductivity ratio is in the range of 3 to 310 times, the deteriorated portion is almost equal to the recording mark area, and good recording with little jitter and deviation is performed. Was completed. In this case, deterioration of the light absorbing layer was promoted and deformation was slight.
If the thickness of the light absorbing layer 4 is less than 5 nm, heat absorption is not sufficient, and deformation and change are insufficient. On the other hand, if the thickness is more than 200 nm, the volume is large, so that deformation is suppressed, and there is a portion which cannot be changed optically due to thermal influence, which is a problem.
The light absorbing layer may be a single layer or a multilayer.
[0030]
The material used for the second layer 5 is not particularly limited except that it contains a metal material. For example, the same material as that used for the first layer can be used. The protective layer 10 can be formed using an inorganic material such as SiO, SiN, or AlN, or an organic material such as a photocurable resin.
The inorganic protective layer can be formed by a vacuum film forming method, and the organic protective layer is a photocurable resin film (for example, SD1700, SD318, SD301 manufactured by Dainippon Ink and Chemicals, Inc.) on the second layer 5. And then irradiating resin curing light.
When a high NA lens is used to increase the density, the protective layer needs to be light-transmissive.
For example, when the NA is increased, it is necessary to reduce the thickness of a portion through which the reproduction light is transmitted. This is due to an angle (a so-called tilt angle, which is proportional to the square of the product of the reciprocal of the wavelength of the light source and the numerical aperture of the objective lens) in which the disk surface deviates from the perpendicular to the optical axis of the optical pickup with the increase in NA. This is because the allowable amount of the generated aberration is small, and the tilt angle is easily affected by the aberration due to the thickness of the substrate.
Therefore, the influence of the aberration on the tilt angle is made as small as possible by reducing the thickness of the substrate.
[0031]
Therefore, for example, a recording layer is formed by forming irregularities on a substrate, a reflective film is provided thereon, and a light-transmitting protective layer, which is a thin film that transmits light, is further provided thereon. An optical recording medium that reproduces information on a recording layer by irradiating light, a reflective film is provided on a substrate, and a heat receiving layer and a light absorbing layer are formed thereon to form a recording layer. There has been proposed an optical recording medium in which a protective layer having transparency is provided, and reproducing information is irradiated from the protective layer side to reproduce information on the recording layer.
With this configuration, it is possible to cope with an increase in the NA of the objective lens by reducing the thickness of the cover layer. That is, by providing a thin cover layer and performing recording and reproduction from the cover layer side, it is possible to further increase the recording density.
Note that such a protective layer is generally formed of a polycarbonate sheet or an ultraviolet curable resin. The thickness is preferably 0.1 mm or less. The polycarbonate sheet is fixed with a modified acrylic resin-based double-sided adhesive.
[0032]
On the other hand, a super-resolution technique can be added to the first and second layers. Usually, the reproduction limit of an optical disc is represented by λ / 2NA. (Where λ is the wavelength and NA is the sine of the aperture angle of the light)
In order to realize a resolution exceeding this limit, the following super-resolution technology is applied. That is, the intensity distribution I of the reproduction beam obtained by condensing the laser light on the medium by the objective lens is
I = I ₀ × exp [-2 (r / r ₀ ) ² ]
(Where I ₀ Is the intensity at the center of the laser beam, r ₀ Means that the laser beam intensity is 1 / e ² Radius).
When the recording medium is heated by the reproducing beam having the intensity distribution of Gaussian distribution, the temperature distribution of the portion irradiated with the beam also becomes similar to the Gaussian distribution.
By setting a high temperature part near the center of the beam as a reproduction area and a low temperature part around the center as a part not involved in recording / reproduction, the diameter of the effective beam spot is reduced and the resolution is improved.
In the Gaussian distribution, the temperature is about 0.6 times the center temperature, that is, the radius r ₀ The slope becomes steep at / 2. When this portion is matched, stable recording / reproduction becomes possible.
[0033]
As a disk form, a structure in which two substrates are bonded to each other so as to sandwich a three-layer structure (hereinafter, referred to as a three-layer structure) including a first layer, a light absorption layer, and a second layer inside. it can. In addition, a so-called single-plate structure can be employed without bonding two substrates.
Each of these two substrates has a three-layer structure. By irradiating a light beam from one of the substrates, information is recorded on each light absorption layer, and the light beam is irradiated on the light absorbing layer. The substrate and the three-layer structure may transmit 40% or more of the light beam.
Further, as a disk form, two or more sets of three-layer structures can be provided on one substrate.
At this time, information may be recorded on each light absorbing layer by irradiating the light beam from the substrate side, or information may be recorded on each light absorbing layer by irradiating the light beam from the side opposite to the substrate. May be recorded.
[0034]
As described above, when recording information on a plurality of light absorbing layers by irradiating a light beam from a certain direction, the light absorbing layer on the light beam incident side and the light absorbing layer on the opposite side are different. It may have a film thickness.
Further, the element serving as the main component of the first layer on the light beam incident side is the same as the element serving as the main component of the first layer on the opposite side, and the content of the element serving as the main component is light. The first layer on the beam incident side may be different from the first layer on the opposite side.
Furthermore, at least one element among the elements that are the main components of the first layer on the light beam incident side and at least one element among the elements that are the main components of the first layer on the opposite side, Different elements may be used.
The melting point of the light absorbing layer on the light beam incident side may be different from the melting point of the light absorbing layer on the opposite side.
[0035]
A guide groove is formed spirally or concentrically on the substrate, and either the guide groove or between two adjacent guide grooves (referred to as a guide groove) is used as a recording track, and information is recorded on the recording track. Can be taken. It is also possible to adopt a configuration in which guide grooves are formed spirally or concentrically on the substrate, and both the guide grooves and between the guide grooves are used as recording tracks, and information is recorded on the recording tracks.
Each of the two substrates has a three-layer structure, and when information is recorded on each of the light absorbing layers by irradiating a light beam from one of the substrates, a spiral formed on the substrate is formed. Alternatively, it is preferable that the shape of the concentric guide groove is different between the light beam incident side and the opposite side.
At this time, the depth of the guide groove of the substrate on the light beam incident side is smaller than the depth of the guide groove of the substrate on the opposite side, or the width of the guide groove of the substrate on the light beam incident side is opposite to that of the opposite side. It is more preferable that the width is larger than the width of the guide groove of the substrate.
[0036]
The address information and the like of the optical recording medium can be formed in advance on the substrate as a preformat signal. As a form thereof, a concave or convex emboss pit, or a wobble method of modulating the width of a groove portion or a land portion according to information is possible. As the wobble method, a method of meandering only one of the inner and outer peripheral sides of the groove, or both the inner and outer peripheral sides of the groove can be employed.
[0037]
In the case where the two sets of three-layer structure are used, the reflectance, transmittance, and absorptance of the first set are r1, t1, and a1, and the reflectance, transmittance, and absorptance of the second set are r2, t2, and a2. If the total reflectance from the first set is R1, the total reflectance from the second set is R2, and the total absorptance of the first set is A1, and the total reflectance of the second set is A2, these parameters are as follows. The following relationship holds.
r1 + t1 + a1 = 1
r2 + t2 + a2 = 1
R1 = r1
R2 = r2 × t12
A1 = a1
A2 = a2 × t1
In order for the signal quality of the first set and the second set to be the same, the reflectivity of both must be the same, and for the same recording sensitivity, the absorptance of both must be the same Is a necessary condition, and therefore it is necessary to satisfy the following expression.
r1 = r2 × t12
a1 = a2 × t1
Here, since t1 is a value smaller than 1,
r1 <r2
a1 <a2
Must be satisfied. That is, the reflectance of the first set must be less than the reflectance of the second set, and the absorptance of the first set must be less than the absorptance of the second set. It is preferable that the transmittance t1 of the first set is 40% or more, because this relationship can be easily satisfied.
[0038]
As a method of setting the reflectance and the absorptance of the first set and the reflectance and the absorptance of the second set to different values, there is a method of changing the film thickness of the first set and the second set. When the thickness of the first set is set to be smaller than the thickness of the second set, the above relational expression can be satisfied. At this time, it is preferable that the transmittance of the second set is substantially 0 (zero) because the reflectance and the absorptance of the second set can be further increased.
On the other hand, it is necessary to satisfy r1 <r2 from the point of signal strength, but there is a method of making the recording sensitivity of the first set and the second set almost equal even if a1 ≧ a2. That is a method in which the melting point of the second set of light absorbing layers is lower than the melting point of the first set of light absorbing layers so that recording can be performed with a small absorption rate. According to this method, the temperature at which recording is possible is low even if the absorptance of the second set is low, so that recording can be performed with laser light irradiation of the same power as that of the first set. As a method of changing the melting point, there is a method of changing the composition of the light absorbing layer.
As described above, when recording and reproducing information with respect to each of two sets of light absorbing layers by irradiating a laser beam from one side, the medium as in the present invention has good recording sensitivity, It is not necessary to increase the absorptance of the absorbing layer itself as in a conventional medium, and the reflectivity can be increased. This effect is further enhanced if a material having a high reflectance and a low melting point is selected as the light absorbing layer.
[0039]
When the light absorption layer or the first layer is formed by a sputtering method, an evaporation method, a spin coating method, or the like, the surface of each layer opposite to the substrate may have a shape different from that of the substrate. In particular, when the film is formed by the spin coating method, the grooves and uneven pits formed on the substrate tend to be buried, and the shape of the substrate and the shape of the film on the side opposite to the substrate are greatly different.
In the case where recording and reproduction are performed on both light absorbing layers by irradiating light from one side to a medium having a structure in which two substrates are bonded together with the above-described three-layer structure sandwiched therebetween, the first set includes light incident. The surface on the side is the substrate surface, and the second set is the surface on the light incident side is the surface on the opposite side to the substrate surface, so if the same substrate is used, parameters relating to grooves or pits formed in advance on the substrate, That is, the push-pull signal, the divided push-pull signal, the signal amplitude of the pre-pit, and the like differ between the first set and the second set. Therefore, by changing the groove shape and pit shape of the substrate carrying the first set and the substrate carrying the second set, it becomes possible to make parameters relating to the grooves or pits uniform.
[0040]
Next, FIG. 4 shows a flowchart of an example of a manufacturing process of the optical recording medium (disk) according to the present invention. Although each step is publicly known, it is briefly described as follows.
S1: Polish and wash the glass disk.
S2: Perform silane coating.
S3: spin-coating a photoresist on a glass disk to have a predetermined film thickness
A resist layer is formed.
S4: Prebake is performed to blow off the solvent.
S5: Irradiate the resist layer with a laser through a condenser lens (Kuttin
G).
S6: The exposed glass disk is developed.
S7: The resist is heated above Tg to shape the groove shape (first bake).
S8: Baking is performed to solidify the pattern (second baking).
S9: Vapor deposition and plating are performed.
S10: By forming a metal film on the uneven surface of the glass disk and peeling the metal film
Create a stamper.
S11: Injection molding is performed using a stamper to form a replica having a predetermined film thickness.
To achieve.
S12: If necessary, a hard coat layer on one side of the transparent substrate by a spin coat method
To form
S13: A first layer is formed on the other side of the transparent substrate by a sputtering method.
S14: A light absorption layer is formed on the first layer by a spin coating method.
S15: A second layer is formed on the light absorbing layer by a sputtering method.
S16: If necessary, other layers such as a protective layer are laminated to form a disk single plate.
(When using as single veneer)
S17: A single disk obtained by laminating other layers such as a protective layer as necessary
Two sheets are laminated to form a double-sided disc.
S18: The disc is stored in the cartridge.
S19: The characteristics are evaluated.
In this flowchart, steps S7 and S8 can be performed simultaneously. Further, the shaping of the groove shape in the step S7 can be arbitrarily selected from a range of a heating temperature of 90 to 180 ° C. and a time of 5 to 90 minutes.
[0041]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In particular, although the embodiments are directed to a disk-shaped optical recording medium, the present invention can, of course, be applied to other forms of optical recording medium such as a card, a stick, and a tape.
From these examples, the layer configuration and the recording principle of the optical recording medium of the present invention are very effective in realizing an optical recording medium made of an organic material corresponding to a blue laser wavelength and further realizing an optical recording medium capable of securing a high degree of modulation. It turns out that it is.
[0042]
Example 1
On a polycarbonate substrate having a preformat pattern shown in FIGS. 1 and 2, a first layer having a thickness of 100 nm and a second layer having a thickness of 80 nm were formed by a sputtering method using the following materials.
・ First layer (The value in parentheses is the thermal conductivity W / m · kat at 300k)
SiO ₂ (1.38), Al ₂ O ₃ (46), Te (3.96), Ge
(59.9), one of MgO (60)
・ Second layer (The value in parentheses is the thermal conductivity W / m · kat at 300k)
Any one of Ag (427), Au (315), and Al (237)
The ratio of the thermal conductivity of the first layer to the thermal conductivity of the second layer is in the range of 3 to 310 times for any combination, and the thermal conductivity of the second layer is higher.
Before forming the second layer, the first layer has a basic skeleton represented by the following [Chemical Formula 2] on the first layer, and the central metal M is VO, Zn, Pd, or Co. , Four R are C ₆ H ₆ − (CF ₃ ) ₂ A mixed solution of an equal amount of four types of C—O— phthalocyanine compounds was formed by spin coating to form a light absorbing layer (average thickness: 100 nm).
Next, on the second layer, SD1700 (thermal conductivity: 1.0 or less) manufactured by Dainippon Ink and Chemicals, Inc. was laminated with a film thickness of 5 μm to form a protective layer.
Embedded image

[0043]
Recording was performed on the optical recording medium under the following conditions using an optical disk evaluation device DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. FIG. 3 shows the results when Te was used for the first layer and Ag was used for the second layer.

In this optical recording medium, 10 or more φ = 2 μm micropores, 4 φ = 5 μm micropores, and one φ = 10 μm micropore exist in the light absorbing layer. ² In the range, there was a portion which was thinner than the average film thickness by 2% or more than the average film thickness, but the error was corrected by the player, and good reproduction was possible.
In addition, it was confirmed that even in the portion where the micropores did not exist, there was a portion in an island shape which was thinner than the average thickness by 2% or more of the average thickness. This portion was not an open cell but a closed cell.
[0044]
When the ratio of the thermal conductivity between the first layer and the second layer is out of the range of 3 to 310 times, for example, when the same material is used for the first and second layers (relative ratio = 1), The dye in the light absorbing layer does not selectively adhere to either the first or the second layer, and the deterioration of the dye at the interface which determines the reflection is reduced, and the change in the optical characteristics is reduced. Was.
When the ratio exceeds 310 times in the system using the inorganic material-containing layer, for example, the first layer is made of glass (Pyrex 7740, thermal conductivity = 1.10 W / m · k), and the second layer is made of Ag. In the case (relative ratio = 388), the pigment layer is altered and adheres preferentially to Ag, and a change in optical properties is obtained. However, since the first layer, which is the inorganic material-containing layer, is hard, it is heated by heat. Problems such as cracks and peeling occurred.
[0045]
The thickness of the light absorbing layer made of phthalocyanine can be arbitrarily selected in the range of 10 to 100 nm. When the thickness is less than 10 nm, the amount of light absorption is small, and good recording is not performed. Above 100 nm, the absorptance was high and the reflectivity was insufficient, and the volume was too large to form recording pits.
The above optical characteristics required a value of 3.5 or more when the intensity was expressed as log10ε using the molecular extinction coefficient ε of the B band of phthalocyanine. When it is smaller than 3.5, even if the film thickness is increased, the absorption is impure, and good recording could not be performed.
Further, the thermal conductivity of the first and second layers adjacent to the light absorbing layer needs to be 59.9 (W / m · kat300 k) or less of Ge. When MgO having a thermal conductivity of 60.0 (W / m · kat at 300 k) was used, good recording could not be performed due to high thermal conductivity.
Further, Te used for the first layer is preferably oxidized or nitrogenated in order to improve the storage stability. This method can be achieved by sputtering Te in the presence of oxygen or nitrogen, or by leaving it in the air for about 3 hours after forming the Te film.
When sputtering is performed in the presence of oxygen or nitrogen, the content is preferably in the range of 5 to 30% based on 100 of argon.
[0046]
Example 2
On the polycarbonate substrate having the preformat pattern shown in FIGS. 1 and 2, a first layer having a thickness of 50 nm and a second layer having a thickness of 90 nm were formed by a sputtering method using the following materials.
・ First layer: Bi _Fifteen Te ₈₅ , SiC, Ag ₆₀ Sb ₄₀ , Ag ₆₀ Cu ₄₀ , Ge _Fifteen Te ₈₅ , Ge _Fifteen Sb ₈₅ , Au ₇₀ Bi ₃₀ What
One
-Second layer: Ag
Before the formation of the second layer, an organic material layer composed of a mixture of four dyes represented by the same [Chemical Formula 2] as in Example 1 was formed on the first layer by spin coating ( An average thickness of 100 nm) and a light absorbing layer were formed.
Other layers were formed in the same manner as in Example 1.
When the same recording as in Example 1 was performed on the write-once optical recording medium manufactured as described above, a clear signal was obtained.
[0047]
Example 3
A 15 nm-thick film of Te is formed as a first layer on a polycarbonate substrate having a preformat pattern shown in FIGS. 1 and 2 by a sputtering method, and a cyanine dye represented by the following chemical formula 3 is formed thereon. 4] An organic material layer composed of a mixture of merocyanine dyes was formed by spin coating (average thickness: 100 nm) to form a light absorbing layer.
A second layer of Ag having a thickness of 80 nm was formed on the light absorbing layer by a sputtering method.
Further, on this second layer, SD1700 (thermal conductivity: 1.0 or less) manufactured by Dainippon Ink and Chemicals, Inc. was laminated with a film thickness of 5 μm to form a protective layer.
When recording was performed on the write-once optical recording medium manufactured as described above in the same manner as in Example 1, both the short mark and the long mark had sufficiently large modulation degrees and very clear signals were obtained.
Embedded image

Embedded image

[0048]
Example 4
On a polycarbonate substrate having a preformat pattern shown in FIGS. 1 and 2, a 15 nm-thick layer of Te containing oxygen is formed as a first layer by sputtering, and vanadyl 5, 14, 23, 32 is formed thereon. -Tetraphenyl-2,3-naphthalocyanine was formed into a film by spin coating (average thickness: 100 nm) to form a light absorbing layer.
An 80 nm-thick second layer made of Ag was laminated on the light absorbing layer by a sputtering method.
Further, on this second layer, SD1700 (thermal conductivity: 1.0 or less) manufactured by Dainippon Ink and Chemicals, Inc. was laminated with a film thickness of 5 μm to form a protective layer.
When recording was performed on the write-once optical recording medium manufactured as described above in the same manner as in Example 1, both the short mark and the long mark had sufficiently large modulation degrees and very clear signals were obtained.
[0049]
Example 5
On a polycarbonate substrate having a preformat pattern shown in FIGS. 1 and 2, a 10 nm-thick layer of Te containing nitrogen is formed as a first layer by a sputtering method, and a first layer is formed by the following general formula [Chemical Formula 5]. An organic material layer made of the indicated azo dye was formed by spin coating (average film thickness: 100 nm) to form a light absorbing layer.
On this light absorbing layer, a second layer having a thickness of 90 nm and made of Ag was laminated by a sputtering method.
Further, on this second layer, SD1700 (thermal conductivity: 1.0 or less) manufactured by Dainippon Ink and Chemicals, Inc. was laminated with a film thickness of 5 μm to form a protective layer.
When recording was performed on the write-once optical recording medium manufactured as described above in the same manner as in Example 1, both the short mark and the long mark had sufficiently large modulation degrees and very clear signals were obtained.
Embedded image

(Where R ₁ Is a phenyl group, R ₂ ~ R ₆ Represents a hydrogen atom. )
[0050]
Example 6
A write-once optical recording medium was produced in the same manner as in Example 1 except that any of the following dyes was used as the light absorbing layer, and the same recording as in Example 1 was performed. Signal was obtained.
1,4-bis (5'-phenyloxazol-2'-yl) benzene, 1,4-bis (4'-methyl-5'-phenoxazol-2'-yl) benzene, 4,4'-bis (2'-sulfostyryl) biphenyl, 2,5-bis (5'-methylbenzoxazol-2'-yl) thiophene, NK1342, NK1977, NK1886, NK1819, NK1331, NK1837, NK863, NK3212, NK88, NK3989, NK1204 , NK723, NK3984 (all manufactured by Nippon Kogaku Dyeing Co., Ltd.),
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[0051]
Examples 7 to 16
Spiral pre-grooves having the following track pitch, groove width and groove depth are formed on the surface by injection molding. A polycarbonate substrate having a diameter of 120 mm and a thickness of 1.1 mm is formed by sputtering to a thickness of 60 nm. Of a phthalocyanine dye represented by the following chemical formula (2.6), THF (tetrahydrofuran) 2.6 g, ethylcyclohexane 6.2 g, IPA (isopropyl alcohol) 2.4 g, and 1-methoxy- A coating solution dissolved in a mixed solvent of 4.6 g of 2-propanol was applied by spin coating to form a light absorbing layer (with a thickness of about 35 to 45 nm in the pregroove).

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Wherein M is VO and the four Rs are C ₆ H ₆ − (CF ₃ ) ₂ CO-. ]
Then, a ZnS-SiO layer having a thickness of about 40 nm is formed thereon as a second layer. ₂ The layers were formed by sputtering.
The absorbance of the light absorbing layer at a wavelength λ = 405 nm was 0.2.
Furthermore, a UV curing adhesive (manufactured by Dainippon Ink and Chemicals, Inc., trade name: SD-347) is applied thereon at 200 rpm by a spin coating method, and after the adhesive is spread over the entire surface while changing from 300 rpm to 4000 rpm. Then, a cover layer made of a 0.07 mm thick polycarbonate resin sheet (trade name: Pure Ace, manufactured by Teijin Limited) was overlaid, the adhesive was cured by irradiating ultraviolet rays, and the cover layer was attached to prepare an optical recording medium.
[0052]
When recording was performed on the optical recording medium under the following conditions using an optical disk evaluation device DDU-1000 (wavelength: 405 nm, NA: 0.85) manufactured by Pulstec Industrial Co., Ltd., both short marks and long marks were recorded. , The degree of modulation was sufficiently large, and a very clear signal was obtained.

FIG. 5 shows the light absorption spectrum of the dye of the above formula [13]. As is clear from the figure, there is a local maximum of sub absorption near the wavelength λ = 350 nm.
For comparison, FIG. 6 shows a light absorption spectrum of a phthalocyanine dye in which the maximum of the sub-absorption exists near the wavelength λ = 320 nm.
The absorbances in FIGS. 5 and 6 are values obtained by spin-coating or sputtering a material on a quartz substrate and measuring the sample using UV-2500 (PC) SGLP manufactured by Shimadzu Corporation.
In the case of Example 7 using the dye having the maximum side absorption at a wavelength longer than 330 nm, the jitter was as good as 8.8%. On the other hand, in the case of an optical recording medium produced in the same manner as in Example 7 using the phthalocyanine dye of FIG. 6 having a maximum of sub-absorption at a wavelength shorter than 330 nm, the recording sensitivity is poor and short pits are formed. I couldn't do that.
Therefore, when recording at a wavelength of 405 nm, the absorption of the dye must be on the longer wavelength side of 330 nm or more. The optical recording media of Examples 8 to 16 all showed an eye pattern and jitter similar to those of Example 7.
Further, when recording was performed at a wavelength of 405 nm, when the maximum of sub-absorption was on the longer wavelength side than 400 nm, good recording could not be performed because the absorption was too large.
From the above results, it is preferable that the first light absorbing layer has an absorption maximum in a wavelength range of 330 to 400 nm.
[0053]
On the other hand, if the wavelength used for recording / reproduction and erasure is λ1, and the reflectance of the first light absorbing layer obtained by irradiating the measurement light in the range of λ1 ± 10 nm from the substrate side is 7% or more, a higher contrast due to the interference effect is obtained. Is obtained.
Similarly, assuming that the wavelength used for recording / reproduction / erasing is λ1, it is preferable that the reflectance of the first light absorption layer obtained by making the measurement light in the range of λ1 ± 10 nm incident from the light absorption layer side is 8% or more. .
At present, the wavelength λ1 used for recording / reproducing and erasing is generally in the range of 390 to 420 nm. More specifically, when SHG (non-linear effect) of 780 nm is used, 390 to 400 nm and blue laser are used. In this case, it is 400 to 410 nm, and when 830 nm SHG is used, it is 410 to 420 nm.
When a blue laser is used, it is necessary that the reflectance of the first light absorbing layer obtained by making the measurement light having a wavelength λ1 = 395 to 415 nm incident from the substrate side be 7% or more, and It is preferable that the reflectance of the first light-absorbing layer obtained by making the measurement light having a wavelength λ1 = 395 to 415 nm incident from the light-absorbing layer side be 8% or more.
Further, the contrast ratio before and after recording can be increased by making the thickness of the first light absorbing layer larger than the thickness showing the reflection maximum at the wavelength used for recording and reproduction.
7 and 8 show spectra in the case of having reflection at the wavelength used for recording / reproduction / erasing in Example 7. In the figure, Rg is the case where the measurement light is irradiated from the substrate side, and Rl is the case where the light is irradiated from the film surface side.
The reflectivity in FIGS. 7 and 8 is an absolute reflectivity obtained by spin-coating or sputtering a material on a quartz substrate and measuring the sample using UV-2500 (PC) SGLP manufactured by Shimadzu Corporation.
[0054]
Example 17
On a polycarbonate substrate having a preformat pattern shown in FIG. 1 and FIG. ₂ A first layer having a thickness of 150 nm made of ₂ O ₃ ・ ZnO ₂ Was formed by sputtering with a thickness of 50 nm.
Before forming the second layer, vanadyl 5,14,23,32-tetraphenyl-naphthalocyanine was formed on the first layer by spin coating (average thickness: 100 nm). An absorption layer was formed.
Other layers were formed in the same manner as in Example 1.
When the same recording as in Example 1 was performed on the write-once optical recording medium manufactured as described above, a clear signal was obtained.
In addition, the recording of the medium of this example could be erased by baking at 200 ° C. for 30 minutes or more after recording.
[0055]
【The invention's effect】
According to the inventions 1 to 20, an optical recording medium made of an organic material capable of recording even in a blue laser wavelength region, particularly in a wavelength region near 405 nm, a high density can be achieved, a high degree of modulation, and Provides an optical recording medium that has little change in recording characteristics such as recording sensitivity, degree of modulation, jitter, and error rate and changes in reflectance with respect to fluctuations in recording / reproducing wavelength, and has excellent storability and a method of manufacturing the same. it can.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view of a main part showing an example of a layer configuration of an optical recording medium of the present invention.
FIG. 2 is a perspective view showing an example of the configuration of an optical recording medium (optical disc) of the present invention.
FIG. 3 is a diagram showing the result of recording on the optical recording medium of Example 1.
FIG. 4 is a view showing a flowchart of manufacturing an optical disc according to the present invention.
FIG. 5 is a graph showing a light absorption spectrum of a dye represented by the formula [13].
FIG. 6 is a diagram showing a light absorption spectrum of a phthalocyanine dye in which a maximum of sub-absorption exists near a wavelength λ = 320 nm.
FIG. 7 is a diagram showing a spectrum when reflection occurs at a wavelength used for recording / reproduction / erasing in Example 7 (when measurement light is irradiated from the substrate side).
FIG. 8 is a view showing a spectrum when light is reflected at a wavelength used for recording / reproduction and erasing in Example 7 (when light is irradiated from the film surface side).
[Explanation of symbols]
1 Transparent substrate
1a Center hole
2 Preformat pattern
2a Guide groove
2b Pre-pit
2c Land part
3 First layer
4 Light absorption layer
5 Second layer
10 Protective layer

Claims (20)

A light-absorbing layer containing at least one dye and having a thickness of 5 to 200 nm has a three-layer structure sandwiched between a first layer and a second layer, wherein the first layer and the second layer are An optical recording medium comprising a metal material and / or an inorganic material. When the first layer and the second layer contain a metal material, the thermal conductivity of the first layer is in a relative ratio of 3 to 310 times the thermal conductivity of the second layer. The optical recording medium according to claim 1, wherein: 3. The optical recording medium according to claim 1, wherein the light absorbing layer has an absorption maximum in a wavelength range of 330 to 400 nm. The wavelength of light used for recording / reproduction / erasing is λ1, and the reflectance of the light absorbing layer obtained by irradiating measurement light from the substrate side in the range of λ1 ± 10 nm is 7% or more. The optical recording medium according to any one of the above. The wavelength of light used for recording / reproduction / erasing is λ1, and the reflectance of the light absorbing layer obtained by irradiating measurement light from the light absorbing layer side in the range of λ1 ± 10 nm is 8% or more. 4. The optical recording medium according to any one of 3. The optical recording medium according to claim 4, wherein the wavelength λ1 is 390 to 420 nm. 7. The optical recording medium according to claim 6, wherein the wavelength λ1 is 405 nm. The dye is at least one selected from the group consisting of cyanine, phthalocyanine, naphthalocyanine, merocyanine, azo, squarylium, porphyrin, polyene, basestyryl and formazan chelate dyes The recording medium according to claim 1, wherein: 9. The optical recording medium according to claim 8, wherein the dye is a material having a porphyrin ring as a basic skeleton. The optical recording medium according to claim 9, wherein the material having a porphyrin ring as a basic skeleton contains a tetraazaporphyrin ring. The optical recording medium according to claim 10, wherein the material containing a tetraazaporphyrin ring is a phthalocyanine dye. When the phthalocyanine-based dye exhibits a B-band absorption due to a porphyrin ring between wavelengths λ = 300 to 400 nm in a solution state, and its intensity is represented by log10ε (ε is a molecular absorption coefficient), it is 3.5 or more. The optical recording medium according to claim 11, wherein: 13. The optical recording medium according to claim 11, wherein the light absorbing layer has a thickness of 10 to 100 nm. 14. The optical recording medium according to claim 1, wherein the light absorbing layer further contains an organic substance having a decomposition temperature of 160 to 500C. 15. The optical recording medium according to claim 1, wherein the inorganic material contains an inorganic oxide or an inorganic carbide as a main component. The optical recording medium according to claim 15, wherein the inorganic oxide or the inorganic carbide is any oxide or carbide of In, Si, Sn, and Zn. 17. The optical recording medium according to claim 1, wherein one of the first and second layers has a thermal conductivity of 59.9 (W / m · k @ at 300 k) or less. 18. The optical recording medium according to claim 1, wherein one of the first and second layers is made of silver, copper, or aluminum. 19. The optical recording medium according to claim 1, wherein one of the first and second layers contains Te, or Te and another metal, and contains oxygen and / or nitrogen. . In forming the first or second layer containing Te or Te and another metal and also containing oxygen and / or nitrogen, while introducing oxygen and / or nitrogen into the atmosphere, Te, or Te and other The film is formed by a method of sputtering Te or a method of introducing Te or another metal without introducing oxygen and / or nitrogen to take in nitrogen and oxygen in the atmosphere. A method for manufacturing an optical recording medium according to claim 19.

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