JP2004348881A - Phase change type optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase change type optical recording medium having satisfactory recording sensitivity even to light having a short wavelength and low output such as a blue laser, free from the occurrence of noise such as jitter, having excellent O/W characteristics and satisfactory archival characteristics and realizing high density recording. <P>SOLUTION: The phase change type optical recording medium has at least a first recording structure layer, a resin intermediate layer 6 and a second recording structure layer 200 on a substrate 1 in this order. The first recording structure layer has a reflection layer 2, a first interface layer 14, a first protective layer 3, a first recording layer 4 and a second protective layer 5 in this order from the substrate 1 side, the second recording structure layer has a third protective layer 7, a heat radiation layer 8, a second interface layer 15, a fourth protective layer 9, a second recording layer 10, a fifth protective layer 11 and a sixth protective layer in this order from the resin intermediate layer 6 side and the third and the sixth protective layers are translucent layers having ≥70% light transmittance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

表１から分るように、第１界面層を設けた方がアーカイバル特性が良好である。
【００２９】
また、第１界面層、第２界面層の材料として、（ＴｉＣ）_８０（ＴｉＯ_２）_２０、（ＺｒＣ） _８０ （ＺｒＯ_２） _２０、（ＳｉＣ）_８０（ＳｉＯ_２）_２０，（ＣｒＣ）_８０（ＣｒＯ_２）_２０の何れかを用いると、これらの材料は安定である上に、材料中の酸素量が１０重量％以下と少量であるため、反射層や放熱層にＡｇやＡｌ等を使用しても、酸化による変化は殆ど見受けられない。上記材料とＡｇからなる反射層及び放熱層を組み合わせた光記録媒体のアーカイバル保存性（８０℃８５％ＲＨで２００時間保存）を調べたところ、記録したマークのジッタが変化せず、良好な特性を示した。
しかし、第二の記録構成層の放熱性は、前述のように第３保護層の放熱性だけでは不十分であり、特にＳｂＴｅ系合金からなる記録層では、最初の急冷によりアモルファスマークを形成するので、放熱性を改善するため第３保護層と放熱層と第２界面層を組み合わせた構成とすることにより、高密度記録特性、Ｏ／Ｗ特性、保存性を改善できる。
【００３０】
次に、放熱機能を担う反射層と放熱層について説明する。
反射層はとりわけ高熱伝導率の材料を用いることにより、消去比及び消去パワーマージンを改善できる。検討の結果、広い消去パワー範囲において本発明の記録層が持つ良好な消去特性を発揮させるには、単に膜厚方向の温度分布や時間変化のみならず膜面方向（記録ビーム走査方向に対して垂直方向）の温度分布をできるだけ平坦化できるような層構成を用いるのが好ましい。本発明においては、非常に高熱伝導率で３００ｎｍ以下の薄い反射層を用いて、横方向の放熱効果を促進することが好ましい。
また一般に薄膜の熱伝導率はバルク状態の熱伝導率に比べて小さくなる。特に、４０ｎｍ未満の薄膜では成長初期の島状構造の影響で熱伝導率が１桁以上小さくなる場合があり好ましくない。更に、成膜条件によって結晶性や不純物量が異なるため、同じ組成の膜を作成したつもりでも熱伝導率が異なることもあり、配慮が必要である。
【００３１】
第一の記録構成層の反射層による放熱は、反射層の厚みを厚くしても促進できるが、反射層の厚みが３００ｎｍを超えると、第１記録層の膜面方向よりも膜厚方向の熱伝導が顕著になり、膜面方向の温度分布改善効果が得られない。また、反射層自体の熱容量が大きくなり、反射層ばかりでなく、ひいては第１記録層の冷却に時間がかかるようになって非晶質マークの形成が阻害される。最も好ましいのは、高熱伝導率の反射層を薄く設けて横方向への放熱を選択的に促進することである。従来用いられていた急冷構造は、膜厚方向の１次元的な熱の逃げのみに注目し、第１記録層から反射層に早く熱を逃すことのみを意図しており、この平面方向の温度分布の平坦化に十分な注意が払われていなかった。
反射層の材料としては、Ａｇ又はＡｇ合金、Ａｌ合金等が挙げられる。
Ａｇ合金としては、後述の放熱層に用いられると同じＡｇ合金が挙げられる。Ａｇ合金を反射層として用いる場合、好ましい膜厚は３０〜２００ｎｍである。３０ｎｍ未満では純Ａｇでも放熱効果は不十分である。２００ｎｍを超えると熱が水平方向より垂直方向に逃げて水平方向の熱分布改善に寄与しないし、不必要な厚膜は生産性を低下させる。また、膜表面の微視的な平坦性も悪くなる。
【００３２】
Ａｌ合金としては、例えば、Ｔａ、Ｔｉ、Ｃｏ、Ｃｒ、Ｓｉ、Ｓｃ、Ｈｆ、Ｐｄ、Ｐｔ、Ｍｇ、Ｚｒ、Ｍｏ、Ｍｎの少なくとも１種を０．２〜２原子％添加した合金が挙げられ、これらは添加元素濃度に比例して体積抵抗率が増加し、また耐ヒロック性が改善されるので、耐久性、体積抵抗率、成膜速度等を考慮して用いることができる。添加不純物量が０．２原子％未満では、成膜条件にもよるが、耐ヒロック性が不十分であることが多い。また、２原子％より多いと上記の低抵抗率を得難い。経時安定性をより重視する場合には添加成分としてはＴａが好ましい。
更に、Ｃｕを０．３〜５．０原子％含有するＡｌ−Ｃｕ系合金も好ましい。特に、ＺｎＳとＳｉＯ_２との混合系組成の膜とＴａ_２Ｏ_５の膜を積層した２層構成保護層とする場合には、Ｃｕを０．５〜４．０原子％含有するＡｌ−Ｃｕ系合金が耐食性、密着性、高熱伝導率の全てをバランス良く満足するので望ましい。また、Ｓｉを０．３〜０．８原子％、Ｍｇを０．３〜１．２原子％含有するＡｌ−Ｍｇ−Ｓｉ系合金も好ましい。
上記Ａｌ合金を反射層として用いる場合、好ましい膜厚は１５０〜３００ｎｍである。１５０ｎｍ未満では純Ａｌでも放熱効果が不十分であり、３００ｎｍを超えると、Ａｇ合金の場合と同様に、熱が水平方向より垂直方向に逃げて水平方向の熱分布改善に寄与しないし、反射層そのものの熱容量が大きくなり、そのため記録層の冷却速度が遅くなってしまう。また、膜表面の微視的な平坦性も悪くなる。
【００３３】
次に放熱層について説明する。
本発明の第２記録層は結晶化温度（Ｔｍ）近傍での再凝固時の結晶成長が再結晶化の律速になっている。Ｔｍ近傍での冷却速度を極限まで大きくして非晶質マーク及びそのエッジの形成を確実かつ明確なものとするには、超急冷構造が有効であり、かつ膜面方向の温度分布の平坦化で、元々Ｔｍ近傍で高速消去可能であったものがより高消去パワーまで確実に再結晶化による消去を確保できる。このため、いわゆる「第３保護層での熱伝導遅延効果を考慮した超急冷構造」を本発明に係る第二の記録構成層に適用すると、従来のＧｅＴｅ−Ｓｂ_２Ｔｅ_３記録層に比べて一層効果がある。
本発明では、このような超急冷のために放熱層を設ける。放熱層の形成に際しては、製膜時のデポジションレートを反射層の場合よりも遅くして膜厚不均一性をなくす必要がある。その膜厚は、４〜１０ｎｍが望ましく、４ｎｍ未満ではデポジションレートを遅くしても不均一になる。また、１０ｎｍ以下にしないと第２の記録層構成の光透過率が高くならないため第１の記録層に光が到達しない。第２の記録層構成の光透過率は４５％以上が望ましい。
【００３４】
放熱層の材料としては、前述した反射層と同じ材料を用いることができるが、上記超急冷構造とするためには、Ａｇ又はＡｇ合金が好ましい。
Ａｇ合金としては、ＡｇにＣｕ、Ｔｉ、Ｖ、Ｔａ、Ｎｂ、Ｗ、Ｃｏ、Ｃｒ、Ｓｉ、Ｇｅ、Ｓｎ、Ｓｃ、Ｈｆ、Ｐｄ、Ｒｈ、Ａｕ、Ｐｔ、Ｍｇ、Ｚｒ、Ｍｏ、Ｍｎの少なくとも１種を０．２〜５原子％添加した合金が挙げられる。経時安定性をより重視する場合には添加成分としてはＴｉ、Ｍｇが好ましい。
本発明者等は反射層や放熱層に用いるＡｌ合金又はＡｇ合金は、その添加元素濃度に比例して体積抵抗率が増加することを確認している。一方、不純物の添加は一般的に結晶粒径を小さくし、粒界の電子散乱を増加させて熱伝導率を低下させると考えられる。添加不純物量を調節することは、結晶粒径を大きくすることで材料本来の高熱伝導率を得るために必要である。
【００３５】
なお、反射層や放熱層は通常スパッタ法や真空蒸着法で形成されるが、ターゲットや蒸着材料そのものの不純物量もさることながら、成膜時に混入する水分や酸素量も含めて全不純物量を２原子％以下とする必要がある。このためにプロセスチャンバの到達真空度は１×１０^−３Ｐａ以下とすることが望ましい。また、１０^−４Ｐａより悪い到達真空度で成膜する場合には、成膜レートを１ｎｍ／秒以上、好ましくは１０ｎｍ／秒以上として不純物が取り込まれるのを防ぐことが望ましい。或いは、意図的な添加元素を１原子％より多く含む場合は、成膜レートを１０ｎｍ／秒以上として付加的な不純物混入を極力防ぐことが望ましい。
【００３６】
成膜条件は不純物量とは無関係に結晶粒径に影響を及ぼす場合もある。例えば、ＡｌにＴａを２原子％程度混入した合金膜は、結晶粒の間に非晶質相が混在するが結晶相と非晶質相の割合は成膜条件に依存する。また、低圧でスパッタするほど結晶部分の割合が増え、体積抵抗率が下がり、熱伝導率が増加する。
膜中の不純物組成或いは結晶性は、スパッタに用いる合金ターゲットの製法やスパッタガス（Ａｒ、Ｎｅ、Ｘｅ等）にも依存する。このように薄膜状態の体積抵抗率は、金属材料、組成のみによっては決まらない。高熱伝導率を得るためには、上記のように不純物量を少なくすることが望ましいが、一方でＡｌやＡｇの純金属は耐食性や耐ヒロック性に劣る傾向があるため、両者のバランスを考慮して最適組成を決める必要がある。
【００３７】
更なる高熱伝導と高信頼性を得るため反射層や放熱層を多層化することも有効である。この場合、少なくとも１層は、全層合計膜厚の５０％以上の膜厚を有し実質的に放熱効果に寄与する前記高熱伝導性材料（低体積抵抗率材料）からなり、他の層が耐食性や保護層との密着性、耐ヒロック性の改善に寄与するように構成される。
具体的には、金属の中で最も高熱伝導率及び低体積抵抗率であるＡｇを用いた場合、Ａｇに隣接する保護層中にＳが含まれると、硫化による腐食を起し易く、繰返しオーバーライト（Ｏ／Ｗ）した場合の劣化がやや速いという傾向がある。また、高温高湿の加速試験環境下で腐食を生じ易い傾向がある。
【００３８】
そこで、低体積抵抗率材料としてＡｇ又はＡｇ合金を用いる際には、隣接保護層との間に界面層としてＡｌ合金層を厚さ１〜１００ｎｍ設けることも有効である。Ａｌ合金としては反射層のところで述べたのと同じ材料を用いることができる。界面層の厚さは１ｎｍ未満では保護効果が不十分で、１００ｎｍを超えると放熱効果が犠牲になる。また、厚さを５ｎｍ以上とすれば、層が島状構造とならず均一に形成され易い。
更に、Ａｇ合金放熱層とＡｌ合金界面層を用いる場合、ＡｇとＡｌは比較的相互拡散し易い組み合わせなので、Ａｌ表面を厚さ１ｎｍ以上酸化して界面酸化層を設けることが一層好ましい。なお、界面酸化層が５ｎｍ、特に１０ｎｍを越えると、それが熱抵抗となり本来の趣旨である極めて放熱性の高い放熱層としての機能が損なわれるので好ましくない。
【００３９】
本発明において良好な特性を示す高熱伝導率の反射層及び放熱層を規定するために、それぞれの熱伝導率を直接測定することも可能であるが、その熱伝導の良否を電気抵抗を利用して見積ることができる。金属膜のように電子が熱又は電気伝導を主として司る材料においては、熱伝導率と電気伝導率との間に良好な比例関係があるためである。薄膜の電気抵抗は、その膜厚や測定領域の面積で規格化された抵抗率値で表す。体積抵抗率と面積抵抗率は、通常の４探針法で測定でき、ＪＩＳ Ｎ ７１９４によって規定されている。本法により、薄膜の熱伝導率そのものを実測するよりも遥かに簡便かつ再現性の良いデータが得られる。
【００４０】
好ましい反射層及び放熱層の特性としては、体積抵抗率が２０〜１５０ｎΩ・ｍであり、より好ましくは２０〜１００ｎΩ・ｍである。２０ｎΩ・ｍ未満の材料は薄膜状態では実質的に得難い。また１５０ｎΩ・ｍより体積抵抗率が大きい場合でも、例えば３００ｎｍを超える厚膜とすれば面積抵抗率を下げることはできるが、本発明者等の検討によれば、このような高体積抵抗率材料で面積抵抗率のみを下げても十分な放熱効果は得られなかった。厚膜では単位面積当りの熱容量が増大してしまうためと考えられる。また、このような厚膜では成膜に時間がかかり材料費も増えるため、製造コストの観点から好ましくないばかりでなく、膜表面の微視的な平坦性も悪くなってしまう。膜厚３００ｎｍ以下で面積抵抗率０．２〜０．９Ω／□が得られるような低体積抵抗率材料を用いるのが好ましく、０．５Ω／□が更に好ましい。また、放熱層の場合は、光透過率の関係から膜厚２０ｎｍ以下が望ましい。
【００４１】
前述した反射層や放熱層の多層化は、高体積抵抗率材料と低体積抵抗率材料を組み合わせることにより所望の膜厚で所望の面積抵抗率を得るためにも有効である。合金化による体積抵抗率調節は、合金ターゲットの使用によりスパッタ工程を簡素化できるが、ターゲット製造コスト、ひいては媒体の原材料比を上昇させる要因にもなる。従って、純Ａｌや純Ａｇの薄膜と上記添加元素そのものの薄膜を多層化して所望の体積抵抗率を得ることも有効である。層数が３層程度までであれば初期の装置コストは増加するものの、媒体コストは却って抑制できる場合がある。反射層を複数の金属膜からなる全膜厚が４０〜３００ｎｍの多層構造とし、全膜厚の５０％以上が体積抵抗率２０〜１５０ｎΩ・ｍの金属薄膜層（複数の層であってもよい）とするのが好ましい。
【００４２】
次に、図１に示すようにカバー基板を薄く設ける構成で、高ＮＡの対物レンズを用いる場合には、カバー基板の厚さは０．３ｍｍ以下、好ましくは０．０６〜０．２０ｍｍの厚さが要求されるため、シート状であることが好ましい。ＮＡが０．５０〜０．７０では、厚さ０．６ｍｍのカバー基板を用いる。
カバー基板の材料としては、ポリカーボネート樹脂、アクリル樹脂、エポキシ樹脂、ポリスチレン樹脂、アクリロニトリル−スチレン共重合体樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、シリコーン系樹脂、フッ素系樹脂、ＡＢＳ樹脂、ウレタン樹脂などが挙げられるが、光学特性、コストの点で優れるポリカーボネート樹脂、アクリル系樹脂が好ましい。
これらの材料からなる透明シートを用いて薄型カバー基板を形成する方法としては、紫外線硬化性樹脂又は透明な両面粘着シートを介して、透明シートを貼り付ける方法が挙げられる。また、紫外線（ＵＶ）硬化樹脂を保護層上に塗布してこれを硬化させ薄型カバー基板を形成してもよい。
樹脂中間層や接着層にも上記樹脂を用いることができるが、ＵＶ硬化樹脂がコストの面で優れているので好ましい。
【００４３】
【実施例】
以下、実施例及び比較例を示して本発明を更に詳細に説明するが、本発明はこれらの実施例により何ら限定されるものではない。
【００４４】
実施例１
図２に示す層構成で、ポリカーボネート製基板２１上に、反射層２２（Ａｇ_９７Ｃｕ_１Ｐｔ_１Ｐｄ_１）、第１界面層３４〔（ＴｉＣ）_８０（ＴｉＯ_２）_２０〕、第１保護層２３（ＺｎＳ・ＳｉＯ_２）、第１記録層２４（Ａｇ_５Ｉｎ_５Ｓｂ_６５Ｔｅ_２５）、第２保護層２５（ＺｎＳ・ＳｉＯ_２）、樹脂中間層２６（ＵＶ硬化樹脂、三菱マテリアル社製ＳＤ３１８）、第３保護層２７（ＩＺＯ）、放熱層２８（Ａｇ_９７Ｃｕ_１Ｐｔ_１Ｐｄ_１）、第２界面層３５（ＴｉＣ・ＴｉＯ_２）、第４保護層２９（ＺｎＳ・ＳｉＯ_２）、第２記録層３０（Ｇｅ_５Ａｇ_２Ｓｂ_７０Ｔｅ_２３）、第５保護層３１（ＺｎＳ・ＳｉＯ_２）、第６保護層３２（ＩＴＯ）、カバー基板３３（ポリカーボネート）を順次形成して相変化型光記録媒体を作製した。なお、樹脂中間層２６（厚さ３５μｍ）、カバー基板３３（厚さ０．６ｍｍ）以外は、スパッタ法により下記のような厚さに制御しながら形成した。
基板２１：０．６ｍｍ、反射層２２：１２０ｎｍ、第１界面層３４：３ｎｍ、第１保護層２３：１０ｎｍ、第１記録層２４：１２ｎｍ、第２保護層２５：６０ｎｍ、第３保護層２７：７０ｎｍ、放熱層２８：１０ｎｍ、第２界面層３５：３ｎｍ、第４保護層２９：１０ｎｍ、第２記録層３０：７ｎｍ、第５保護層３１：１０ｎｍ、第６保護層３２：６５ｎｍ
【００４５】
実施例２
第１界面層３４の材質を（ＺｒＣ）_８０（ＺｒＯ_２）_２０に変え、第３保護層の材質をＩＴＯに変え、第６保護層の材質をＩＺＯに変えた他は、実施例１と全く同様にして相変化型光記録媒体を作製した。
【００４６】
実施例３
第１界面層３４の材質を（ＳｉＣ）_８０（ＳｉＯ_２）_２０に変え、第６保護層の材質をＡＺＯに変えた他は、実施例１と全く同様にして相変化型光記録媒体を作製した。
【００４７】
実施例４
第６保護層の材質を（Ａｌ_２Ｏ_３）_８０（ＳｉＯ_２）_２０に変えた他は、実施例１と全く同様にして相変化型光記録媒体を作製した。
【００４８】
実施例５
第６保護層の材質を（ＭｇＯ）_８０（ＳｉＯ_２）_２０に変え、第１界面層と第２界面層を（ＣｒＣ）_８０（ＣｒＯ）_２０に変えた他は、実施例１と全く同様にして相変化型光記録媒体を作製した。
【００４９】
実施例６
第６保護層の材質を（Ｉｎ_２Ｏ_３）_８０（ＺｎＯ）_１０（ＳｎＯ）_１０に変えた他は、実施例１と全く同様にして相変化型光記録媒体を作製した。
【００５０】
比較例１
第１界面層を無くし、第６保護層の材質を第５保護層と同じＺｎＳ・ＳｉＯ_２に変え、第５保護層と第６保護層の総膜厚を１５０ｎｍとした点以外は実施例１と全く同様にして相変化型光記録媒体を作製した。
【００５１】
上記実施例１〜６及び比較例１の光記録媒体の各層の構成材料を纏めて表２に示す。
【表２】

【００５２】
＜評価＞
上記実施例１〜６及び比較例１の各光記録媒体に対し、波長４０２ｎｍ、開口数ＮＡ０．６５の光学系を用いて集束光ビームを照射し、線速：６．０ｍ／ｓ、０．１６０μｍ／ｂｉｔの条件で、初期ジッタ（Ｊｉｔｔｅｒ）、記録感度（記録パワー、即ち、ジッタ最小を示すパワー）、アーカイバル特性、Ｏ／Ｗ特性を評価した。
結果を表３に示す。評価判断基準は次の通りである。
・アーカイバル特性：８０℃、８５％（ＲＨ）の保存でジッタ上昇が２０％以上となる時間（Ｈ）。
・Ｏ／Ｗ特性：オーバーライト（Ｏ／Ｗ）によるジッタ上昇が２０％に到達したオーバーライト回数（回）。
・記録感度（記録パワー）：ジッタ最小となるパワー
【表３】

表から分るように、実施例１〜６の光記録媒体は、比較例１に比べて何れも優れた記録感度、アーカイバル特性、Ｏ／Ｗ特性を示した。
比較例１は、保存特性（アーカイバル特性）が非常に悪く、記録パワーも高く、感度が良好ではなかった。
【００５３】
実施例７
第５保護層と第６保護層の膜厚を下記表４に示すように変えた点以外は、実施例１と同様にしてサンプルＮｏ．１〜８の相変化型光記録媒体を作成し、評価を行った。
膜厚評価は分光エリプソメトリーを用いて測定した。また、記録再生評価は、波長４０５ｎｍ、ＮＡ＝０．６５のパルステック工業のＤＤＵ−１０００を用い、線速６ｍ／ｓ、記録パワー１４ｍＷ、イレースパワー６ｍＷ、再生パワー０．９ｍＷ、ボトムパワー０．１ｍＷで記録再生を行った。
表から分るように、総膜厚が１００ｎｍ以下で再生信号（ＲＦ）レベルの変動が５％以下と小さく、ジッタも９％以下で、記録再生特性が良好となっている。
【表４】

【００５４】
【発明の効果】
本発明によれば、青色レーザーなどの短波長の低出力光に対しても記録感度が良く、ジッタなどのノイズが発生せず、Ｏ／Ｗ特性が優れ、アーカイバル特性も良好で高密度記録可能な相変化型光記録媒体を提供できる。
【図面の簡単な説明】
【図１】本発明の相変化型光記録媒体の一例を示す層構成断面図である。
【図２】実施例の相変化型光記録媒体の層構成を示す断面図である。
【符号の説明】
１ 基板
２ 反射層
３ 第１保護層
４ 第１記録層
５ 第２保護層
６ 樹脂中間層
７ 第３保護層
８ 放熱層
９ 第４保護層
１０ 第２記録層
１１ 第５保護層
１２ 第６保護層
１３ カバー基板
１４ 第１界面層
１５ 第２界面層
２１ 基板（ポリカーボネート）
２２ 反射層（Ａｇ_９７Ｃｕ_１Ｐｔ_１Ｐｄ_１）
２３ 第１保護層（ＺｎＳ・ＳｉＯ_２）
２４ 第１記録層（Ａｇ_５Ｉｎ_５Ｓｂ_６５Ｔｅ_２５）
２５ 第２保護層（ＺｎＳ・ＳｉＯ_２）
２６ 樹脂中間層（ＵＶ硬化樹脂 ＳＤ３１８）
２７ 第３保護層（ＩＺＯ）
２８ 放熱層（Ａｇ_９７Ｃｕ_１Ｐｔ_１Ｐｄ_１）
２９ 第４保護層（ＺｎＳ・ＳｉＯ_２）
３０ 第２記録層（Ｇｅ_５Ａｇ_２Ｓｂ_７０Ｔｅ_２３）
３１ 第５保護層（ＺｎＳ・ＳｉＯ_２）
３２ 第６保護層（ＩＺＯ）
３３ カバー基板（ポリカーボネート）
３４ 第１界面層（ＴｉＣ・ＴｉＯ_２）
３５ 第２界面層（ＴｉＣ・ＴｉＯ_２）
１００ 第一の記録構成層
２００ 第二の記録構成層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium for high-density recording (phase-change optical recording medium) having a rewritable phase-change optical recording layer such as DVR.
[0002]
[Prior art]
Generally, compact discs (CDs) and DVDs are recorded by detecting a binary signal and a tracking signal using a change in reflectivity caused by interference of light from the bottom of the concave pit and the mirror surface. In recent years, a phase-change rewritable compact disc (CD-RW: CD-rewritable) has been widely used as a medium compatible with the reproduction of a CD, and a phase-change rewritable DVD has also been used. Various possible DVDs have been proposed. Further, while the capacity of DVD is 4.7 GB, a system high-density DVR is proposed in which the recording / reproducing wavelength is reduced to 350 nm to 420 nm, and the numerical aperture NA (Numerical Aperture) is increased to 20 GB or more. (For example, Non-Patent Document 1).
[0003]
These phase-change type rewritable CDs, DVDs, and DVRs detect a recording information signal using a reflectance difference and a phase difference change caused by a refractive index difference between an amorphous state and a crystalline state. A typical phase-change optical recording medium has a structure in which a lower protective layer, a phase-change recording layer, an upper protective layer, and a reflective layer are provided on a substrate. In addition, it is possible to control the phase difference and provide compatibility with CDs and DVDs. In a CD-RW, within a range where the reflectance is reduced to about 15 to 25%, compatibility between a CD and a recording signal and a groove signal can be secured, and a CD drive to which an amplification system for covering a low reflectance is added. Reproduction is possible if used. In the case of a phase-change optical recording medium, the erasing and re-recording processes can be performed only by the intensity modulation of one focused light beam. Includes overwrite (O / W) recording in which recording and erasing are performed simultaneously.
For recording information using a phase change, a crystal, an amorphous state, or a mixed state thereof can be used, and a plurality of crystal phases can be used. Generally, a phase-change optical recording medium records an unrecorded / erased state in a crystalline state and forms an amorphous mark.
[0004]
As a material of the phase change recording layer, a chalcogen element, that is, a chalcogenide alloy containing S, Se, and Te is often used. For example, GeTe-Sb ₂ Te ₃ GeSbTe based on pseudo binary alloy, InTe-Sb ₂ Te ₃ InSbTe based on pseudo binary alloy, Sb _0.7 Te _0.3 AgInSbTe-based, GeSbTe-based, and the like containing a eutectic alloy as a main component. Among them, GeTe-Sb ₂ Te ₃ Pseudo-binary alloy with excess Sb added, especially Ge ₁ Sb ₂ Te ₄ Or Ge ₂ Sb ₂ Te ₅ Compositions in the vicinity of intermetallic compounds such as these have been mainly put to practical use. These compositions are characterized by crystallization without phase separation peculiar to intermetallic compounds, are easy to initialize due to a high crystal growth rate, and have a high recrystallization rate during erasing. For this reason, conventionally, as a recording layer exhibiting practical O / W characteristics, a pseudo binary alloy system or a composition near an intermetallic compound has been noted (Non-Patent Document 2 and the like).
[0005]
Conventionally, reports have been made on a GeSbTe ternary composition or a recording layer composition containing an additional element based on the ternary composition (Patent Documents 1 to 4).
However, development of a material having such a composition has only just begun, and there are many problems that must be solved in order to apply it to an optical recording medium for high-density recording such as rewritable DVR.
In particular, in the case of an optical system having a short wavelength such as a blue laser, the beam output is low, and therefore, there is a disadvantage that noise is easily generated in the recording layer. If the thickness is not large, it is difficult to satisfy both the O / W characteristics and the storage characteristics (since the thickness of the protective layer is likely to fluctuate and the storage characteristics are difficult if the film thickness is large). It has become.
Patent Document 5 discloses a metal oxide such as ZnO or ZrO, a carbide such as TiC, or a mixture thereof as a heat-resistant protective layer material. However, there is no effect of satisfying the recording / reproducing characteristics while being sulfide-resistant and ensuring the storage stability.
[0006]
Non-Patent Document 3 discloses that the recording layer has one layer, but ZnS.SiO. ₂ / AlN / ZnS ・ SiO ₂ The invention in which a three-layer structure is provided is disclosed. However, as a result, the total layer thickness cannot be reduced.
Further, the invention of Japanese Patent Application No. 2002-334303, which is a prior application of the present applicant, has one recording layer and does not have a two-layer structure as in the present invention.
In addition, the invention of Japanese Patent Application No. 2002-334303, which is a prior application of the present applicant, discloses that at least a first recording component layer, a resin intermediate layer, and a second recording component layer are provided in this order on a substrate. One recording constituent layer is composed of a heat dissipation layer, an interface layer, a first protective layer, a first recording layer, and a second protective layer in this order from the substrate side, and the second recording constituent layer is in that order from the resin intermediate layer side. A phase-change type optical recording medium comprising a third protective layer, a heat-dissipating layer, an interface layer, a fourth protective layer, a second recording layer, and a fifth protective layer. " (The present invention has a new effect by adding the sixth protective layer).
[0007]
[Patent Document 1]
JP-A-61-258787
[Patent Document 2]
JP-A-62-152786
[Patent Document 3]
JP-A-1-63195
[Patent Document 4]
JP-A 1-211249
[Patent Document 5]
JP-A-6-60426
[Non-patent document 1]
ISOM Technical Digest, '00 (2000), 210
[Non-patent document 2]
SPIE, vol. 2514 (1995), pp 294-301.
[Non-Patent Document 3]
ODS2001, Technical Digest P28
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described circumstances, and has a good recording sensitivity even for low output light of a short wavelength such as a blue laser, does not generate noise such as jitter, and has excellent O / W characteristics. It is an object of the present invention to provide a phase-change optical recording medium having good archival characteristics and capable of high-density recording.
[0009]
[Means for Solving the Problems]
The above object is achieved by the following inventions 1) to 8) (hereinafter referred to as inventions 1 to 8).
1) At least a first recording component layer, a resin intermediate layer, and a second recording component layer are provided in this order on a substrate, and the first recording component layer is a reflective layer, a first interface layer, a A first protective layer, a first recording layer, and a second protective layer. The second recording component layer includes a third protective layer, a heat dissipation layer, a second interface layer, a fourth protective layer, 2. A phase-change optical recording medium, comprising: a second recording layer, a fifth protective layer, and a sixth protective layer, wherein the third protective layer and the sixth protective layer are translucent layers having a light transmittance of 70% or more. .
2) The phase-change optical recording medium according to 1), wherein the first recording layer and the second recording layer are made of an alloy containing SbTe as a main component.
3) The first protective layer, the second protective layer, the fourth protective layer, and the fifth protective layer are made of ZnS.SiO. ₂ A phase-change optical recording medium according to 1) or 2), wherein
4) The phase-change optical recording medium according to any one of 1) to 3), wherein the third protective layer is made of ITO or IZO.
5) The sixth protective layer is made of ITO, IZO, AZO, In ₂ O ₃ Mixed composition of ZnO and SnO, Al ₂ O ₃ And SiO ₂ Mixture composition of MgO and SiO ₂ 4. The phase-change optical recording medium according to any one of 1) to 4), wherein
6) The first interface layer and / or the second interface layer is made of TiC.TiO. ₂ , ZrC / ZrO ₂ , SiC / SiO ₂ , CrC / CrO ₂ The phase-change optical recording medium according to any one of 1) to 5), characterized by comprising:
7) The phase-change optical recording medium according to any one of 1) to 6), wherein the reflection layer and / or the heat dissipation layer is made of Ag, an Ag alloy, or an Al alloy.
8) The phase-change optical recording medium according to any one of 1) to 7), wherein the total thickness of the fifth protective layer and the sixth protective layer is 100 nm or less.
[0010]
Hereinafter, the present invention will be described in detail.
As described above, the present invention is characterized in that a sixth protective layer is further added to the invention according to the earlier application of the present applicant.
That is, in the second recording constituent layer, the third protective layer and the heat dissipation layer are formed thin (preferably 20 nm or less) to improve heat dissipation, thereby improving O / W characteristics and recording at high density. By further providing a sixth protective layer between the fifth protective layer and the cover substrate using a material having a light transmittance of 70% or more and a high thermal conductivity, the heat radiation layer and the third protective layer can be formed. Since heat can be released not only in the direction of the third protective layer but also in the opposite direction of the sixth protective layer, the sensitivity is improved, and the distance between the recording layer and the cover substrate on the light incident side is higher than that of the related art. The total thickness of the protective layer (the total thickness of the fifth protective layer and the sixth protective layer in the present invention) can be reduced to, for example, 100 nm or less.
[0011]
Further, by using a material having a light transmittance of 70% or more and a high thermal conductivity for the third protective layer, the light transmittance of the second recording constituent layer is improved, and the amount of light reaching the first recording layer is increased. However, the recording sensitivity is improved, and noise such as jitter does not occur, and a phase-change optical recording medium having improved O / W characteristics, archival characteristics, and high-density recording performance can be obtained.
In the first recording component layer, a first interface layer is provided between the reflective layer and the first protective layer. In the second recording component layer, a second interface layer is provided between the heat radiation layer and the fourth protective layer. It is provided to prevent mixing and reaction of materials between the reflective layer or the heat radiation layer and the protective layer. TiC / TiO is used as a material for these interface layers. ₂ , ZrC / ZrO ₂ , SiC / SiO ₂ , CrC / CrO ₂ Is used as the protective layer material, ZnS.SiO. ₂ In the case where Ag or an Ag alloy is used for the reflection layer or the heat dissipation layer, the sulfuration of Ag or the Ag alloy can be prevented, and the storage characteristics can be improved.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 schematically shows a cross section of a layer structure showing an example of the phase change type optical recording medium of the present invention, and shows a substrate 1 / a reflective layer 2 / a first interface layer 14 / a first protective layer 3 / a first protective layer 3. 1 recording layer 4 / second protective layer 5 / resin intermediate layer 6 / third protective layer 7 / heat dissipation layer 8 / second interface layer 15 / fourth protective layer 9 / second recording layer 10 / fifth protective layer 11 / It has the configuration of the sixth protective layer 12 / cover substrate 13.
As a material of the substrate 1, a transparent resin such as polycarbonate, acrylic resin, or polyolefin, or transparent glass can be used. Among them, polycarbonate resin is the most preferred material because it is most widely used in CD and is inexpensive. The substrate 1 is usually provided with a groove having a pitch of 0.8 μm or less for guiding the recording / reproducing light, but this groove is not necessarily required to be a geometrically rectangular or trapezoidal groove. Grooves may be formed optically by forming waveguides having different rates.
[0013]
Preferred phase-change recording materials used for the first and second recording layers include alloys containing Sb and Te as main components. Among them, those containing Ge, Sb, and Te as constituent elements are preferable. If necessary, other elements may be added to each recording layer made of such constituent elements up to a total of about 10 atomic%. Further, the optical constant of the recording layer can be finely adjusted by further adding at least one element selected from O, N and S to each recording layer in an amount of 0.1 to 5 atomic%. However, adding more than 5 atomic% is not preferable because it lowers the crystallization speed and deteriorates the erasing performance.
In order to improve the stability over time without lowering the crystallization rate during O / W, at least one selected from V, Nb, Ta, Cr, Co, Pt, and Zr is added in an amount of 8 atomic% or less. Preferably, more preferable addition amount is 0.1 to 5 atomic%. It is desirable that the total amount of these elements and Ge added to SbTe is 15 atomic% or less. If it exceeds 15 atomic%, phase separation of components other than Sb will be induced. The effect of the addition is particularly large when the Ge content is 3 to 5 atomic%.
[0014]
In order to improve the stability over time and finely adjust the refractive index, it is preferable to add at least one element selected from Si, Sn, and Pb to 5 atomic% or less. The total added amount of these elements and Ge is preferably 15 atomic% or less. Note that Si, Sn, and Pb are elements having a four-coordinate network, like Ge.
By adding at least one element selected from Al, Ga, and In at 8 atomic% or less, the crystallization temperature can be increased, and at the same time, the jitter can be reduced and the recording sensitivity can be improved. Therefore, the content is preferably set to 6 atomic% or less. The total added amount of these elements and Ge is preferably 15 atomic% or less, more preferably 13% or less.
Further, when Ag is added in an amount of 8 atomic% or less, there is an effect in improving the recording sensitivity, and the effect is particularly remarkable when used when the amount of Ge exceeds 5 atomic%. However, if the addition amount of Ag exceeds 8 atomic%, it is not preferable because the jitter increases or the stability of the amorphous mark is impaired. On the other hand, if the total amount of Ag and Ge exceeds 15 atomic%, segregation is likely to occur, which is not preferable. A particularly preferable Ag content is 5 atomic% or less.
[0015]
The first and second recording layers are phase change recording layers, and the thickness thereof is generally preferably in the range of 5 to 100 nm. If the thickness is less than 5 nm, it is difficult to obtain a sufficient contrast, and the crystallization speed tends to be slow, so that erasing in a short time tends to be difficult. On the other hand, if it exceeds 100 nm, it is still difficult to obtain optical contrast, and cracks are likely to occur. The contrast needs to be compatible with a read-only disc such as a DVD.
For high-density recording in which the shortest mark length is 0.5 μm or less, the thickness of the first and second recording layers is preferably 5 to 25 nm. If it is less than 5 nm, the reflectance is too low, and the influence of a non-uniform composition and a sparse film in the initial stage of film growth tends to appear, which is not preferable. On the other hand, if the thickness is more than 25 nm, the heat capacity is increased and the recording sensitivity is deteriorated, and the crystal growth becomes three-dimensional, so that the edge of the amorphous mark is disturbed and the jitter tends to be increased. Further, the volume change due to the phase change of the first and second recording layers becomes remarkable, and the repeated overwrite (O / W) durability deteriorates, which is not preferable. From the viewpoint of mark end jitter and repetitive overwrite (O / W) durability, it is more preferable to set the thickness to 20 nm or less.
[0016]
The density of the first and second recording layers is at least 80% of the bulk density, preferably at least 90%. In order to increase the density in the sputter film forming method, the recording layer is irradiated by lowering the pressure of a sputter gas (a rare gas such as Ar) at the time of film formation or by disposing a substrate close to the front of the target. It is necessary to increase the amount of high energy Ar.
High-energy Ar is one in which Ar ions applied to a target for sputtering are partially repelled and reach the substrate side, or Ar ions in plasma are accelerated by a sheath voltage on the entire surface of the substrate and reach the substrate. Is. Such a high-energy rare gas irradiation effect is referred to as an "atomic peening effect". In sputtering generally used in Ar gas, Ar is mixed into a sputtered film by an atomic peening effect. The atomic peening effect can be estimated from the amount of Ar in the mixed film. That is, if the amount of Ar is small, it means that the high-energy Ar irradiation effect is small, and a film having a low density is easily formed. On the other hand, if the amount of Ar is too large, high energy Ar irradiation is intense and the density increases, but Ar taken in the film is repeatedly released at the time of overwriting (O / W), and Ar is released to generate voids. , Deteriorating repeated durability. An appropriate amount of Ar in the recording layer film is 0.1 to 1.5 atomic%. Further, it is preferable to use high-frequency sputtering rather than DC sputtering because a high-density film can be obtained by reducing the amount of Ar in the film.
[0017]
In addition, the state after the formation of the first and second recording layers is usually amorphous. Therefore, it is necessary to crystallize the entire surface of each recording layer after the film is formed to be in an initialized state (unrecorded state). As the initialization method, initialization by annealing in a solid phase is also possible, but initialization by so-called melt recrystallization, in which the recording layer is once melted and slowly cooled and crystallized during resolidification, is desirable. Each of the above recording layers has almost no crystal growth nuclei immediately after film formation and is difficult to crystallize in a solid phase.However, according to melt recrystallization, a small number of crystal nuclei are formed and then melted. Recrystallization proceeds at high speed mainly due to crystal growth.
Since the crystal formed by the melt recrystallization and the crystal formed by the annealing in the solid phase have different reflectivities, if they are mixed, they cause noise. Then, in actual O / W recording, since the erased portion becomes a crystal by melt recrystallization, it is preferable that initialization is also performed by melt recrystallization.
[0018]
At the time of initialization by melt recrystallization, the recording layer is preferably melted locally and in a short time of about 1 millisecond or less. The reason for this is that if the melting region is wide or the melting time or cooling time is too long, each layer is destroyed by heat or the surface of the plastic substrate is deformed. In order to provide a thermal history suitable for initialization, high-power semiconductor laser light having a wavelength of about 600 to 1000 nm is focused and irradiated in an elliptical shape having a major axis of 100 to 300 μm and a minor axis of 1 to 3 μm, and scanning in the minor axis direction. It is desirable to scan at a linear velocity of 1 to 10 m / s as an axis. Even with the same focused light, if it is close to a circle, the melting region is too wide and re-amorphization is likely to occur, and the multilayer structure and the substrate are greatly damaged, which is not preferable.
[0019]
The fact that the initialization was performed by melt recrystallization can be confirmed as follows. That is, the recording medium having the recording power Pw sufficient to melt the recording layer focused to a spot diameter smaller than about 1.5 μm is radiated to the initialized medium at a constant linear velocity in a DC manner. If there is a guide groove, the tracking is performed while the tracking servo and the focus servo are applied to the track formed between the grooves or between the grooves.
Thereafter, if the reflectivity in the erased state obtained by irradiating the same track with erasing light of erasing power Pe (≦ Pw) in DC is almost the same as the reflectivity in the unrecorded initial state, the initialization is performed. The state can be confirmed as a molten recrystallization state. The reason is that the recording layer is once melted by the irradiation of the recording light, and is completely recrystallized by the irradiation of the erasing light. This is because it is in a recrystallized state. Note that the reflectance of the initialized state Rini and the reflectance of the molten and recrystallized state Rcry are substantially the same, when the difference between the two reflectances defined by (Rini−Rcry) / {(Rini + Rcry) / 2}. 0.2 or less (ie, 20% or less). Normally, only by solid-phase crystallization such as annealing, the reflectance difference is larger than 20%.
[0020]
As shown in FIG. 1, the first recording layer is provided between the first protective layer and the second protective layer, and the second recording layer is provided between the fourth protective layer and the fifth protective layer. .
The first, second, fourth, and fifth protective layers sandwiching these recording layers will be described below.
The first protective layer also has a function of efficiently releasing heat to the reflective layer. The second protective layer is effective mainly for preventing the surface of the resin intermediate layer from being deformed due to high temperature during recording. The fourth protective layer has a function of releasing heat to the heat dissipation layer, the third protection layer, and the second interface layer, and a function of preventing mutual diffusion between the second recording layer and the second interface layer or the heat dissipation layer. The fifth protective layer is effective for adjusting the reflectance and preventing the sixth protective layer and the cover substrate from being deformed due to high temperature during recording.
The material of the first, second, fourth, and fifth protective layers is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. It is desirable that the material has low thermal conductivity, but the standard is 1 × 10 ^-3 pJ / (μm · N · nsec). Note that it is difficult to directly measure the thermal conductivity of such a low thermal conductivity material in a thin film state, and as an alternative to the direct measurement, a guide can be obtained from the thermal simulation and the actual recording sensitivity measurement result. .
[0021]
Examples of the low thermal conductivity material that provides favorable results include ZnS, ZnO, and TaS. ₂ And a composite dielectric containing 50 to 90 mol% of at least one of rare earth sulfides and a heat-resistant compound having high transparency and a melting point or a decomposition point of 1000 ° C. or more. Specific examples of the rare earth sulfide include a composite dielectric containing 60 to 90 mol% of a rare earth sulfide such as La, Ce, Nd, and Y. Furthermore, ZnS, ZnO, TaS ₂ Alternatively, the ratio of the rare earth sulfide is preferably set to 70 to 90 mol%.
As the heat-resistant compound having a melting point or a decomposition point of 1000 ° C. or more, Mg, Ca, Sr, Y, La, Ce, Ho, Er, Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Si, Examples include oxides, nitrides, and carbides such as Ge and Pb, and fluorides such as Ca, Mg, and Li.
The above oxides, sulfides, nitrides, carbides, and fluorides do not necessarily have to have a stoichiometric composition, and it is effective to change the composition for controlling the refractive index and the like, or to use a mixture. is there.
Considering the above considerations and the compatibility with the materials of the first and second recording layers, ZnS and SiO 2 are used as the materials of the first, second, fourth, and fifth protective layers. ₂ Is most preferable, and from the viewpoint of cost reduction in production, it is advantageous to use the same material for each protective layer.
[0022]
Subsequently, the function and the like of each protective layer will be described in more detail.
The layer configuration of the present invention belongs to a type of a layer configuration called a quenching structure. The quenching structure employs a layer configuration that promotes heat radiation and increases the cooling rate during resolidification of the recording layer, thereby avoiding the problem of recrystallization during the formation of amorphous marks, and achieving high crystallization by high-speed crystallization. This realizes an erasing ratio.
The thicknesses of the first and fourth protective layers greatly affect the durability in repeated overwriting (O / W), and are particularly important in suppressing the deterioration of jitter. The thickness is generally 5 to 30 nm. If the thickness is less than 5 nm, the effect of delaying the heat conduction in the protective layer is insufficient, and the recording sensitivity is significantly reduced, which is not preferable. If the film thickness is more than 30 nm, a sufficient flattening effect of the temperature distribution in the mark width direction cannot be obtained, and the temperature between the recording layer side of the second and fifth protective layers and the reflection layer or the heat radiation layer side during recording. The difference becomes large, and the protective layer itself is likely to be deformed asymmetrically due to the difference in thermal expansion on both sides of the protective layer. This repetition is not preferable because it causes microscopic plastic deformation to accumulate inside the protective layer and causes an increase in noise.
[0023]
More specifically, the film thickness of the first and fourth protective layers is preferably 15 to 25 nm when the recording laser beam has a wavelength of 600 to 700 nm, 3 to 20 nm when the wavelength is 350 to 600 nm, more preferably 3 to 20 nm. 15 nm.
Further, the thickness of the second and fifth protective layers needs to be 3 to 60 nm. If the thickness is less than 3 nm, the recording layer is easily broken by deformation or the like at the time of melting, and the O / W characteristics deteriorate. On the other hand, if the thickness exceeds 60 nm, the variation in the reflectivity tends to be large due to the total thickness of the fifth protective layer and the sixth protective layer, and it is difficult to record uniformly. From the viewpoint of O / W characteristics, 5 to 50 nm is more preferable.
[0024]
By using the above-described phase-change optical recording material, low jitter can be realized in high-density recording with a minimum mark length of 0.3 μm or less. In the case of using a short-wavelength laser diode (for example, a wavelength of 410 nm or less), it is necessary to pay more attention to the layer structure of the quenching structure. In particular, in the study of one-beam overwrite (O / W) characteristics using a small focused light beam having a wavelength of 500 nm or less and a numerical aperture NA of 0.55 or more, it is often necessary to flatten the temperature distribution in the mark width direction. It has been found that it is important to widen the erase ratio and the erase power margin. The above tendency is the same in an optical system compatible with DVR using an optical system with a wavelength of 350 to 420 nm and NA of about 0.85.
Therefore, the present inventors have studied an appropriate layer configuration of a phase change type optical recording medium having a two-layer recording layer structure so as to meet the above requirements, and have a light transmission property, a heat dissipation property, and a high recording sensitivity. Was designed to improve the recording sensitivity by providing an interface layer.
[0025]
In the high-density mark length modulation recording using the above-described optical system, it is important to use a material having particularly low thermal conductivity for the first and fourth protective layers, and preferably to set the film thickness to 3 to 20 nm. It is. For this reason, the first interface layer provided on the first protective layer needs to have high thermal conductivity. With this configuration, heat does not escape rapidly during high-speed recording, and heat is transmitted to the reflective layer. Becomes possible.
Further, since the light reaching the first recording constituent layer is transmitted light transmitted through the second recording constituent layer, the incident light amount is less than half of the incident light amount of the second recording constituent layer. It is desirable to increase the incident light of the recording constituent layer or to improve the sensitivity of the first recording layer.
According to the present invention, in the first recording constituent layer with little incident light, the recording sensitivity is improved by sandwiching the first recording layer between layers having low thermal conductivity, and the thickness of the first protective layer is reduced to 3 to 20 nm. In this way, the recording sensitivity can be improved by easily absorbing heat.
[0026]
In the above-described layer configuration, when only thermal conductivity is considered, the heat radiation effect is promoted even if the thermal conductivity coefficient of the first protective layer or the fourth protective layer is increased, but if the heat radiation is promoted too much. Since the irradiation power required for recording is increased and the recording sensitivity is remarkably reduced, it is necessary to keep the thermal conductivity low.
Then, by using the thin thermal protective layer having a low thermal conductivity, a time delay is given to the heat conduction from the recording layer to the reflection layer or the heat radiation layer at several nsec to several tens nsec (nanosecond) at the start of the recording power irradiation, Thereafter, heat radiation to the reflection layer and the heat radiation layer can be promoted, so that the recording sensitivity does not unnecessarily decrease due to the heat conduction characteristics of the protective layer.
For this reason, the conventionally known SiO 2 ₂ , Ta ₂ O ₅ , Al ₂ O ₃ It is not preferable to use a protective layer material mainly composed of, for example, AlN, SiN, etc. because it has too high a thermal conductivity.
[0027]
Next, the third protective layer and the sixth protective layer will be described.
As a preferable material of the third protective layer, ITO (In) which can have a light transmittance of 70% or more is used. ₂ O ₃ ) And IZO (In ₂ O ₃ And a mixed composition of ZnO). Since these materials have high thermal conductivity, heat generated when recording is performed in the second recording layer is radiated to the third protective layer via the heat radiation layer. As a result, the recording layer made of a phase change material containing SbTe as a main component, which requires rapid cooling, is in an optimum rapid cooling state, and a small amorphous mark can be formed.
The thickness of the third protective layer is preferably as thick as possible in view of the heat radiation effect. However, if the thickness is greater than 200 nm, the stress increases and cracks occur. If it is less than 20 nm, the heat radiation effect is small. Therefore, the thickness is preferably 20 to 200 μm, and more preferably 30 to 160 nm.
In addition, ITO, IZO, AZO (Al ₂ O ₃ And SnO mixed composition), In ₂ O ₃ Mixed composition of ZnO and SnO, Al ₂ O ₃ And SiO ₂ Mixture composition of MgO and SiO ₂ When any one of the mixed compositions is used, these materials have a light transmittance of 70% or more, so that they can sufficiently transmit light and can also take part of the heat radiation of the second recording layer.
If the film thickness of the sixth protective layer is too large, the light transmittance is reduced. Therefore, the film thickness is preferably 100 nm or less, and if it is 20 nm or more, a heat radiation effect is exhibited.
[0028]
(TiC) satisfying the layer constitution of the present invention and having a thickness of 4 nm ₈₀ (TiO ₂ ) ₂₀ The recording sensitivity characteristics of the first recording layer (80) of a phase-change optical recording medium having a first interface layer made of Table 1 shows the results of comparison of archival characteristics when stored at 85 ° C. and 85% RH.
The recording / reproducing conditions were as follows: recording / reproducing light wavelength: 405 nm, NA of the objective lens = 0.85, recording linear velocity: 6.0 m / s, recording linear density: 0.160 μm / bit, recording power: 9.0 mW (jitter The minimum power), the reproduction power: 0.5 mW, the recording pattern was 1-7 modulation, and a random signal was recorded. The jitter is σ / Tw (window width).
[Table 1]

As can be seen from Table 1, the archival properties are better when the first interface layer is provided.
[0029]
Further, (TiC) is used as a material of the first interface layer and the second interface layer. ₈₀ (TiO ₂ ) ₂₀ , (ZrC) ₈₀ (ZrO ₂ ) ₂₀ , (SiC) ₈₀ (SiO ₂ ) ₂₀ , (CrC) ₈₀ (CrO ₂ ) ₂₀ When any of these materials is used, these materials are stable and the amount of oxygen in the material is as small as 10% by weight or less. Almost no change is seen. When the archival preservation (preservation at 80 ° C. and 85% RH for 200 hours) of the optical recording medium in which the reflective layer and the heat radiation layer made of the above material and Ag were combined was examined, the jitter of the recorded mark did not change and was excellent. The characteristics were shown.
However, the heat dissipation of the second recording component layer is not sufficient only by the heat dissipation of the third protective layer as described above. In particular, in the case of a recording layer made of an SbTe-based alloy, an amorphous mark is formed by the first rapid cooling. Therefore, by combining the third protective layer, the heat radiation layer, and the second interface layer in order to improve heat radiation, high density recording characteristics, O / W characteristics, and storage stability can be improved.
[0030]
Next, the reflection layer and the heat radiation layer that have a heat radiation function will be described.
The erasing ratio and the erasing power margin can be improved particularly by using a material having a high thermal conductivity for the reflective layer. As a result of the study, it has been found that not only the temperature distribution and the time change in the film thickness direction but also the film surface direction (to the recording beam scanning direction) It is preferable to use a layer configuration that can make the temperature distribution (in the vertical direction) as flat as possible. In the present invention, it is preferable to use a thin reflective layer having a very high thermal conductivity of 300 nm or less to promote the heat radiation effect in the lateral direction.
In general, the thermal conductivity of a thin film is smaller than the thermal conductivity in a bulk state. In particular, in the case of a thin film having a thickness of less than 40 nm, the thermal conductivity may be reduced by one digit or more due to the effect of the island structure at the initial stage of growth, which is not preferable. Furthermore, since the crystallinity and the amount of impurities vary depending on the film forming conditions, the thermal conductivity may differ even if the films having the same composition are intended to be prepared, and thus care must be taken.
[0031]
Although the heat dissipation by the reflective layer of the first recording component layer can be promoted by increasing the thickness of the reflective layer, when the thickness of the reflective layer exceeds 300 nm, the thickness of the first recording layer in the film thickness direction is larger than that in the film surface direction. Heat conduction becomes remarkable, and the effect of improving the temperature distribution in the film surface direction cannot be obtained. In addition, the heat capacity of the reflection layer itself increases, so that it takes time to cool not only the reflection layer but also the first recording layer, thereby hindering the formation of amorphous marks. Most preferably, a reflective layer having high thermal conductivity is provided thinly to selectively promote heat radiation in the lateral direction. The quenching structure used conventionally focuses only on one-dimensional heat dissipation in the film thickness direction, and is intended only to quickly release heat from the first recording layer to the reflective layer. Inadequate attention was paid to flattening the distribution.
Examples of the material for the reflective layer include Ag, an Ag alloy, and an Al alloy.
Examples of the Ag alloy include the same Ag alloy as used in the heat radiation layer described later. When an Ag alloy is used as the reflective layer, the preferred film thickness is 30 to 200 nm. If it is less than 30 nm, the heat radiation effect is insufficient even with pure Ag. If it exceeds 200 nm, heat escapes in the vertical direction from the horizontal direction and does not contribute to improving the heat distribution in the horizontal direction, and unnecessary thick films reduce productivity. In addition, the microscopic flatness of the film surface is deteriorated.
[0032]
Examples of the Al alloy include an alloy to which at least one of Ta, Ti, Co, Cr, Si, Sc, Hf, Pd, Pt, Mg, Zr, Mo, and Mn is added in an amount of 0.2 to 2 atomic%. Since these materials increase in volume resistivity in proportion to the concentration of the added element and improve hillock resistance, they can be used in consideration of durability, volume resistivity, film forming speed and the like. If the amount of added impurities is less than 0.2 atomic%, the hillock resistance is often insufficient, depending on the film formation conditions. On the other hand, if it is more than 2 atomic%, it is difficult to obtain the above low resistivity. When more importance is placed on the stability over time, Ta is preferred as an additive component.
Further, an Al-Cu-based alloy containing 0.3 to 5.0 atomic% of Cu is also preferable. In particular, ZnS and SiO ₂ And a film of a mixed composition of ₂ O ₅ In the case of a two-layered protective layer formed by laminating the above films, an Al—Cu alloy containing 0.5 to 4.0 atomic% of Cu satisfies all of corrosion resistance, adhesion and high thermal conductivity in a well-balanced manner. So desirable. Further, an Al-Mg-Si alloy containing 0.3 to 0.8 atomic% of Si and 0.3 to 1.2 atomic% of Mg is also preferable.
When the above-mentioned Al alloy is used as the reflection layer, the preferred film thickness is 150 to 300 nm. If it is less than 150 nm, the heat radiation effect is insufficient even with pure Al. If it exceeds 300 nm, the heat escapes in the vertical direction from the horizontal direction and does not contribute to the improvement of the heat distribution in the horizontal direction as in the case of the Ag alloy. The heat capacity of the recording layer itself becomes large, and the cooling rate of the recording layer becomes slow. In addition, the microscopic flatness of the film surface is deteriorated.
[0033]
Next, the heat radiation layer will be described.
In the second recording layer of the present invention, the crystal growth at the time of re-solidification near the crystallization temperature (Tm) is the rate of recrystallization. In order to increase the cooling rate in the vicinity of Tm to the utmost and make the formation of the amorphous marks and their edges reliable and clear, an ultra-quenched structure is effective, and the temperature distribution in the film surface direction is flattened. Thus, what was originally capable of high-speed erasing in the vicinity of Tm can reliably ensure erasing by recrystallization up to higher erasing power. For this reason, when the so-called “ultra-quenching structure taking into account the heat conduction delay effect in the third protective layer” is applied to the second recording constituent layer according to the present invention, the conventional GeTe-Sb ₂ Te ₃ It is more effective than the recording layer.
In the present invention, a heat radiation layer is provided for such rapid cooling. In forming the heat radiation layer, it is necessary to make the deposition rate at the time of film formation slower than in the case of the reflection layer to eliminate the non-uniformity of the film thickness. The film thickness is desirably 4 to 10 nm, and if it is less than 4 nm, it becomes non-uniform even if the deposition rate is reduced. If the thickness is not more than 10 nm, the light does not reach the first recording layer because the light transmittance of the second recording layer configuration does not increase. The light transmittance of the second recording layer configuration is desirably 45% or more.
[0034]
As the material of the heat radiation layer, the same material as that of the above-described reflection layer can be used. However, Ag or an Ag alloy is preferable in order to obtain the above-mentioned super-quenched structure.
As the Ag alloy, at least Cu, Ti, V, Ta, Nb, W, Co, Cr, Si, Ge, Sn, Sc, Hf, Pd, Rh, Au, Pt, Mg, Zr, Mo, and Mn are used. An alloy to which one type is added in an amount of 0.2 to 5 atomic% is exemplified. When more importance is placed on the stability over time, Ti and Mg are preferable as the additional components.
The present inventors have confirmed that the volume resistivity of the Al alloy or Ag alloy used for the reflective layer and the heat dissipation layer increases in proportion to the concentration of the added element. On the other hand, it is considered that addition of impurities generally reduces the crystal grain size, increases electron scattering at the grain boundaries, and lowers the thermal conductivity. Adjusting the amount of added impurities is necessary to increase the crystal grain size to obtain the original high thermal conductivity of the material.
[0035]
The reflection layer and the heat dissipation layer are usually formed by a sputtering method or a vacuum evaporation method, but the total impurity amount including the amount of water and oxygen mixed in at the time of film formation is reduced in addition to the impurity amount of the target and the evaporation material itself. It is necessary to be 2 atomic% or less. Therefore, the ultimate vacuum degree of the process chamber is 1 × 10 ^-3 It is desirable to set it to Pa or less. Also, 10 ^-4 When a film is formed at an ultimate vacuum degree lower than Pa, it is desirable to set the film formation rate to 1 nm / sec or more, preferably 10 nm / sec or more to prevent impurities from being taken in. Alternatively, in the case where intentional additional elements are included in excess of 1 atomic%, it is desirable to set the film formation rate to 10 nm / sec or more to minimize the addition of additional impurities.
[0036]
Film formation conditions may affect the crystal grain size regardless of the amount of impurities. For example, in an alloy film in which about 2 atomic% of Ta is mixed into Al, an amorphous phase is mixed between crystal grains, but the ratio of the crystalline phase to the amorphous phase depends on film forming conditions. Further, as the sputtering is performed at a lower pressure, the proportion of the crystal part increases, the volume resistivity decreases, and the thermal conductivity increases.
The impurity composition or crystallinity in the film also depends on the manufacturing method of the alloy target used for sputtering and the sputtering gas (Ar, Ne, Xe, etc.). As described above, the volume resistivity in the thin film state is not determined only by the metal material and the composition. In order to obtain a high thermal conductivity, it is desirable to reduce the amount of impurities as described above. On the other hand, pure metals such as Al and Ag tend to be inferior in corrosion resistance and hillock resistance. It is necessary to determine the optimum composition.
[0037]
It is also effective to form the reflective layer and the heat radiation layer in multiple layers in order to obtain higher heat conduction and higher reliability. In this case, at least one layer is made of the high thermal conductive material (low volume resistivity material) having a thickness of 50% or more of the total thickness of all layers and substantially contributing to the heat radiation effect, and the other layers are It is configured to contribute to the improvement of corrosion resistance, adhesion to a protective layer, and hillock resistance.
Specifically, in the case where Ag having the highest thermal conductivity and low volume resistivity among metals is used, if S is contained in the protective layer adjacent to Ag, corrosion due to sulfuration is likely to occur, and the overcoating is repeated. There is a tendency that deterioration when writing (O / W) is slightly faster. Further, there is a tendency that corrosion occurs easily in an accelerated test environment of high temperature and high humidity.
[0038]
Therefore, when using Ag or an Ag alloy as the low volume resistivity material, it is also effective to provide an Al alloy layer having a thickness of 1 to 100 nm as an interface layer between the protective layer and an adjacent protective layer. As the Al alloy, the same materials as described for the reflective layer can be used. If the thickness of the interface layer is less than 1 nm, the protective effect is insufficient, and if it exceeds 100 nm, the heat radiation effect is sacrificed. When the thickness is 5 nm or more, the layer is easily formed uniformly without forming an island structure.
Further, when the Ag alloy heat dissipation layer and the Al alloy interface layer are used, Ag and Al are relatively easily interdiffusion, so it is more preferable to oxidize the Al surface by 1 nm or more to provide an interface oxide layer. If the interfacial oxide layer exceeds 5 nm, especially 10 nm, it becomes a thermal resistance, which impairs the original function of the heat radiation layer having extremely high heat radiation, which is not preferable.
[0039]
In order to define a reflective layer and a heat radiation layer having a high thermal conductivity and exhibiting good characteristics in the present invention, it is possible to directly measure the thermal conductivity of each of them. Can be estimated. This is because in a material such as a metal film in which electrons mainly perform heat or electric conduction, there is a good proportional relationship between the heat conductivity and the electric conductivity. The electric resistance of a thin film is represented by a resistivity value standardized by its film thickness or the area of a measurement region. The volume resistivity and the sheet resistivity can be measured by an ordinary four-probe method, and are specified by JIS N 7194. According to this method, data that is much simpler and has better reproducibility than actually measuring the thermal conductivity itself of the thin film can be obtained.
[0040]
As preferable characteristics of the reflection layer and the heat radiation layer, the volume resistivity is 20 to 150 nΩ · m, and more preferably 20 to 100 nΩ · m. Materials of less than 20 nΩ · m are substantially difficult to obtain in a thin film state. Further, even when the volume resistivity is higher than 150 nΩ · m, the area resistivity can be reduced by forming a thick film having a thickness of more than 300 nm, for example. However, even if only the sheet resistivity was lowered, a sufficient heat radiation effect could not be obtained. It is considered that a thick film increases the heat capacity per unit area. In addition, since such a thick film takes a long time to form a film and increases the material cost, not only is it not preferable from the viewpoint of manufacturing cost, but also the microscopic flatness of the film surface is deteriorated. It is preferable to use a low volume resistivity material that can provide a sheet resistivity of 0.2 to 0.9 Ω / □ at a film thickness of 300 nm or less, and more preferably 0.5 Ω / □. In the case of the heat radiation layer, the thickness is preferably 20 nm or less from the viewpoint of light transmittance.
[0041]
The multilayering of the reflective layer and the heat dissipation layer described above is also effective for obtaining a desired sheet resistivity at a desired film thickness by combining a high volume resistivity material and a low volume resistivity material. Adjusting the volume resistivity by alloying can simplify the sputtering process by using an alloy target, but also causes an increase in the target manufacturing cost and thus the raw material ratio of the medium. Therefore, it is also effective to obtain a desired volume resistivity by forming a multilayer of a thin film of pure Al or pure Ag and a thin film of the additive element itself. If the number of layers is up to about three, the initial apparatus cost increases, but the medium cost can be suppressed. The reflective layer has a multilayer structure composed of a plurality of metal films and having a total thickness of 40 to 300 nm, and 50% or more of the total thickness is a metal thin film layer having a volume resistivity of 20 to 150 nΩ · m (a plurality of layers may be used). ) Is preferable.
[0042]
Next, as shown in FIG. 1, when a cover substrate is provided thin and a high NA objective lens is used, the cover substrate has a thickness of 0.3 mm or less, preferably 0.06 to 0.20 mm. Therefore, the sheet is preferably used. When NA is 0.50 to 0.70, a cover substrate having a thickness of 0.6 mm is used.
Examples of the material of the cover substrate include a polycarbonate resin, an acrylic resin, an epoxy resin, a polystyrene resin, an acrylonitrile-styrene copolymer resin, a polyethylene resin, a polypropylene resin, a silicone resin, a fluorine resin, an ABS resin, and a urethane resin. However, polycarbonate resins and acrylic resins which are excellent in optical characteristics and cost are preferable.
As a method of forming a thin cover substrate using a transparent sheet made of these materials, there is a method of attaching a transparent sheet via an ultraviolet curable resin or a transparent double-sided pressure-sensitive adhesive sheet. Alternatively, an ultraviolet (UV) curable resin may be applied on the protective layer and cured to form a thin cover substrate.
Although the above resin can be used for the resin intermediate layer and the adhesive layer, a UV curable resin is preferable because it is excellent in cost.
[0043]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.
[0044]
Example 1
In the layer configuration shown in FIG. 2, a reflective layer 22 (Ag) is formed on a polycarbonate substrate 21. ₉₇ Cu ₁ Pt ₁ Pd ₁ ), The first interface layer 34 [(TiC) ₈₀ (TiO ₂ ) ₂₀ ], The first protective layer 23 (ZnS.SiO ₂ ), The first recording layer 24 (Ag ₅ In ₅ Sb ₆₅ Te ₂₅ ), The second protective layer 25 (ZnS · SiO ₂ ), Resin intermediate layer 26 (UV curing resin, SD318 manufactured by Mitsubishi Materials Corporation), third protective layer 27 (IZO), heat dissipation layer 28 (Ag) ₉₇ Cu ₁ Pt ₁ Pd ₁ ), The second interface layer 35 (TiC.TiO.) ₂ ), The fourth protective layer 29 (ZnS · SiO ₂ ), The second recording layer 30 (Ge ₅ Ag ₂ Sb ₇₀ Te ₂₃ ), The fifth protective layer 31 (ZnS · SiO ₂ ), A sixth protective layer 32 (ITO), and a cover substrate 33 (polycarbonate) were sequentially formed to produce a phase-change optical recording medium. Except for the resin intermediate layer 26 (thickness: 35 μm) and the cover substrate 33 (thickness: 0.6 mm), they were formed by sputtering to a thickness as described below.
Substrate 21: 0.6 mm, reflective layer 22: 120 nm, first interface layer 34: 3 nm, first protective layer 23: 10 nm, first recording layer 24: 12 nm, second protective layer 25: 60 nm, third protective layer 27 : 70 nm, heat dissipation layer 28: 10 nm, second interface layer 35: 3 nm, fourth protection layer 29: 10 nm, second recording layer 30: 7 nm, fifth protection layer 31: 10 nm, sixth protection layer 32: 65 nm
[0045]
Example 2
The material of the first interface layer 34 is (ZrC) ₈₀ (ZrO ₂ ) ₂₀ And the material of the third protective layer was changed to ITO, and the material of the sixth protective layer was changed to IZO, to produce a phase-change optical recording medium in exactly the same manner as in Example 1.
[0046]
Example 3
The material of the first interface layer 34 is (SiC) ₈₀ (SiO ₂ ) ₂₀ And a phase-change optical recording medium was manufactured in exactly the same manner as in Example 1 except that the material of the sixth protective layer was changed to AZO.
[0047]
Example 4
The material of the sixth protective layer is (Al ₂ O ₃ ) ₈₀ (SiO ₂ ) ₂₀ A phase-change optical recording medium was manufactured in exactly the same manner as in Example 1 except that the optical recording medium was changed to.
[0048]
Example 5
The material of the sixth protective layer is (MgO) ₈₀ (SiO ₂ ) ₂₀ And the first interface layer and the second interface layer are (CrC) ₈₀ (CrO) ₂₀ A phase-change optical recording medium was manufactured in exactly the same manner as in Example 1 except that the optical recording medium was changed to.
[0049]
Example 6
Change the material of the sixth protective layer to (In ₂ O ₃ ) ₈₀ (ZnO) ₁₀ (SnO) ₁₀ A phase-change optical recording medium was manufactured in exactly the same manner as in Example 1 except that the optical recording medium was changed to.
[0050]
Comparative Example 1
The first interface layer is eliminated, and the material of the sixth protective layer is the same as that of the fifth protective layer: ZnS.SiO. ₂ A phase-change optical recording medium was produced in exactly the same manner as in Example 1, except that the total thickness of the fifth protective layer and the sixth protective layer was changed to 150 nm.
[0051]
Table 2 summarizes the constituent materials of each layer of the optical recording media of Examples 1 to 6 and Comparative Example 1.
[Table 2]

[0052]
<Evaluation>
Each of the optical recording media of Examples 1 to 6 and Comparative Example 1 is irradiated with a focused light beam using an optical system having a wavelength of 402 nm and a numerical aperture of NA 0.65, and has a linear velocity of 6.0 m / s. Under the condition of 160 μm / bit, initial jitter (Jitter), recording sensitivity (recording power, that is, power showing the minimum jitter), archival characteristics, and O / W characteristics were evaluated.
Table 3 shows the results. The evaluation criteria are as follows.
Archival characteristics: Time (H) at which jitter rises to 20% or more when stored at 80 ° C. and 85% (RH).
O / W characteristics: the number of times of overwriting (times) when the jitter increase due to overwriting (O / W) reached 20%.
・ Recording sensitivity (recording power): Power that minimizes jitter
[Table 3]

As can be seen from the table, the optical recording media of Examples 1 to 6 exhibited superior recording sensitivity, archival characteristics, and O / W characteristics as compared with Comparative Example 1.
In Comparative Example 1, the storage characteristics (archival characteristics) were very poor, the recording power was high, and the sensitivity was not good.
[0053]
Example 7
Except that the film thicknesses of the fifth protective layer and the sixth protective layer were changed as shown in Table 4 below, the sample Nos. 1 to 8 phase-change optical recording media were prepared and evaluated.
The film thickness was measured using spectroscopic ellipsometry. The recording / reproducing evaluation was performed using a pulse-tech DDU-1000 having a wavelength of 405 nm and NA = 0.65. The linear velocity was 6 m / s, the recording power was 14 mW, the erase power was 6 mW, the reproduction power was 0.9 mW, and the bottom power was 0. Recording and reproduction were performed at 1 mW.
As can be seen from the table, when the total film thickness is 100 nm or less, the fluctuation of the reproduction signal (RF) level is as small as 5% or less, the jitter is 9% or less, and the recording / reproduction characteristics are good.
[Table 4]

[0054]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the present invention, high-density recording with good recording sensitivity, low noise such as jitter, excellent O / W characteristics, good archival characteristics, and the like even for short-wavelength low-output light such as a blue laser. A possible phase-change optical recording medium can be provided.
[Brief description of the drawings]
FIG. 1 is a sectional view of a layer structure showing an example of a phase change type optical recording medium of the present invention.
FIG. 2 is a cross-sectional view illustrating a layer configuration of a phase-change optical recording medium according to an example.
[Explanation of symbols]
1 substrate
2 Reflective layer
3 First protective layer
4 First recording layer
5 Second protective layer
6 resin middle layer
7 Third protective layer
8 Heat dissipation layer
9 fourth protective layer
10 Second recording layer
11 Fifth protective layer
12 6th protective layer
13 Cover substrate
14 First interface layer
15 Second interface layer
21 Substrate (polycarbonate)
22 Reflective layer (Ag ₉₇ Cu ₁ Pt ₁ Pd ₁ )
23 First Protective Layer (ZnS / SiO ₂ )
24 First recording layer (Ag ₅ In ₅ Sb ₆₅ Te ₂₅ )
25 Second protective layer (ZnS / SiO ₂ )
26 resin middle layer (UV curing resin SD318)
27 Third protective layer (IZO)
28 Heat dissipation layer (Ag ₉₇ Cu ₁ Pt ₁ Pd ₁ )
29 Fourth protective layer (ZnS / SiO ₂ )
30 Second recording layer (Ge ₅ Ag ₂ Sb ₇₀ Te ₂₃ )
31 Fifth protective layer (ZnS / SiO ₂ )
32 6th protective layer (IZO)
33 Cover substrate (polycarbonate)
34 First interface layer (TiC / TiO ₂ )
35 Second interface layer (TiC / TiO ₂ )
100 first recording constituent layer
200 Second recording component layer

Claims (8)

On a substrate, at least a first recording component layer, a resin intermediate layer, and a second recording component layer are provided in this order, and the first recording component layer is a reflective layer, a first interface layer, and a first protective layer in this order from the substrate side. Layer, a first recording layer, and a second protective layer. The second recording component layer includes a third protective layer, a heat dissipation layer, a second interface layer, a fourth protective layer, and a second recording layer in this order from the resin intermediate layer side. A phase-change optical recording medium, comprising: a first protective layer, a fifth protective layer, and a sixth protective layer, wherein the third protective layer and the sixth protective layer are translucent layers having a light transmittance of 70% or more. 2. The phase-change optical recording medium according to claim 1, wherein the first recording layer and the second recording layer are made of an alloy containing SbTe as a main component. The first protective layer, a second protective layer, a fourth protective layer, the fifth protective layer, a phase-change optical recording medium according to claim 1 or 2, wherein the consisting of ZnS · SiO _2. 4. The phase-change optical recording medium according to claim 1, wherein the third protective layer is made of ITO or IZO. The sixth protective layer is made of any one of ITO, IZO, AZO, a mixed composition of In ₂ O ₃ , ZnO and SnO, a mixed composition of Al ₂ O ₃ and SiO _{2, and} a mixed composition of MgO and SiO _2. The phase-change optical recording medium according to claim 1. Is the first interface layer and / or the second interface _layer, any one of claims 1 to 5, characterized in that it consists of one of _{TiC · TiO 2, ZrC · ZrO} 2, SiC · SiO 2, CrC · CrO 2 3. The phase-change optical recording medium according to claim 1. 7. The phase-change optical recording medium according to claim 1, wherein the reflection layer and / or the heat dissipation layer is made of Ag, an Ag alloy, or an Al alloy. 8. The phase-change optical recording medium according to claim 1, wherein the total thickness of the fifth protective layer and the sixth protective layer is 100 nm or less.

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