JP3693125B2 - Optical recording medium - Google Patents

Description

であり、本発明は、この組成範囲において、さらに保存信頼性を確保するために好適な組成範囲である。また、本発明の記録層は、Ｃ、Ｎ、Ｏ、Ａｌ、Ｇａ、Ｓｅ、Ｇｅ、Ｐｄ、Ｐｂなどの添加元素が含むことができる。記録層は、スパッタリング、イオンプレーティング、真空蒸着、プラズマＣＶＤ法等によって作製できる。Ｃ、Ｎ、Ｏの添加には、ＣＨ₄、Ｎ₂、ＮＨ₃、ＮＯ₂、Ｎ₂Ｏなどがもちいられる。
【００２８】
本発明で使用する基板の材料は、通常、ガラス、セラミックス、あるいは、樹脂であり、なかでも樹脂基板が成型性、コストの点で好適である。樹脂の代表例として、ポリカーボネート樹脂、エポキシ樹脂、ポリスチレン樹脂、アクリルニトリル−スチレン共重合体樹脂、ポリエチレン樹脂、ポリメチルメタクリレート樹脂などが使用できるが、加工性、光学特性等から、ポリカーボネート樹脂が好ましい。また、基板の形状は、ディスク状、カード状あるいは、シート状であってもよい。基板の厚さは１．２ｍｍ、０．６ｍｍ、０．３ｍｍ等任意のものが使用できるが、クロストークの基板チルト依存性の観点から、より基板厚の小さいものが望まれる。しかし、製膜上の困難や、歩留まり等を考慮すると０．６ｍｍが好ましい。
【００２９】
本発明で使用する第１及び第２保護層は、ＳｉＯ、ＳｉＯ₂、ＺｎＯ、ＳｎＯ₂、Ａｌ₂Ｏ₃、ＴｉＯ₂、Ｉｎ₂Ｏ₃、ＭｇＯ、Ｚｒｏ₂などの酸化物、Ｓｉ₃Ｎ₄、ＡＩＮ、ＴｉＮ、ＢＮ、ＺｒＮなどの窒化物、ＺｎＳ、Ｉｎ₂Ｓ₃、ＴａＳ₄などの硫化物、ＳｉＣ、ＴａＣ₄、Ｂ₄Ｃ、ＷＣ、ＴｉＣ、ＺｒＣなどの炭化物やダイヤモンド状炭素、あるいはその混合物が好ましい。これら第１および第２保護層は、スパッタリング、イオンプレーティング、真空蒸着、プラズマＣＶＤ法等によって作製できる。第１保護層の膜厚は５０ｎｍ〜５００ｎｍ、好ましくは１００ｎｍ〜３００ｎｍ、更に好ましくは１２０ｎｍ〜２５０ｎｍである。第２保護層の膜厚は５ｎｍ〜３００ｎｍ好ましくは、１０ｎｍ〜５０ｎｍである。
スパッタ製膜の場合、第１及び第２保護層の応力は、製膜圧力、製膜電力、基板−ターゲット間距離などで制御することができる。一般に、製膜圧力を高く、製膜プラズマ電力を小さく、基板−ターゲット間距離を大きくすることで応力は軽減される。また、２種以上の複合材料を使用することでも応力の軽減を図ることができる。
【００３０】
反射放熱層としては、Ａｌ、Ａｇ、Ａｕなどの金属材料およびそれらとＴｉ、Ｃｒ、Ｓｉ、などの添加材料が使用できる。反射放熱層は、必ずしも必要ではないが、記録消去の際に生じる過剰な熱を放出し、記録媒体自身への熱ダメージを軽減するために設けるほうが望ましい。反射放熱層は、スパッタリング、イオンプレーティング、真空蒸着、プラズマＣＶＤ法等によって作製できる。
【００３１】
以下に、参考例及び実施例によって、本発明を具体的に説明する。
【００３２】
参考例１〜１６、比較例１〜８
表１にカルコパイライト構造を有する化学量論組成及び／又はそれに近い組成のＡｇＩｎＴｅ₂とが存在するスパッタリングターゲットの組成、及びそれらを用いた場合のディスク特性を示す。これは幅約０．６μｍ、深さ約６００Åのグルーブが形成されているディスク基板（厚さ１．２ｍｍ）に、ＺｎＳ・ＳｉＯ₂からなる２００ｎｍ厚の下部保護層、２５ｎｍ厚の記録層、ＺｎＳ・ＳｉＯ₂からなる３０ｎｍ厚の上部保護層、アルミニウム合金（厚さ１００ｎｍ）からなる反射放熱層、紫外線硬化型樹脂（厚さ５μｍ）からなる保護層を設置してディスクを作成する。なお、記録層のスパッタリング方法は背圧を９×１０^-7ｔｏｒｒで、アルゴンガスをいれ４×１０^-3ｔｏｒｒにして、ＲＦｐｏｗｅｒ４０ワットで行なった。
このディスクで最もＣ／Ｎが高くなる線速で測定し、マーク長約１μｍのマークの記録特性、約３μｍのマークでオーバーライトしたときの消去特性について評価した。ここで、半導体レーザーの波長は７８０ｎｍ、対物レンズのＮＡは０．５である。
ディスク特性の欄の評価値は、レベル３が最も良好な特性（Ｃ／Ｎ≧５５ｄＢ、消去比（Ｅｒｓ）≦−３５ｄＢ）を示すターゲットであることを表し、レベル２は良好な特性（５５＞Ｃ／Ｎ≧４５ｄＢ、−３５＜消去比（Ｅｒｓ）≦−２５ｄＢ）を示すターゲットであることを表し、レベル１は良好な特性を有するディスクが得られなかった（上記以外のもの）ターゲットであることを示す。
Ａｇ、Ｉｎ、Ｔｅ、Ｓｂそれぞれの組成比α、β、γ、δ（原子％）が２≦α≦３０、３≦β≦３０、１０≦γ≦５０、１５≦δ≦８３であるターゲットのとき、本発明で規定した組成比の記録層が得られ、良好なディスク特性が得られていることが判る。
【００３３】
【表１】

【００３４】
また、表２に参考例３のターゲットを用いて記録層をスパッタリングで製膜する際、アルゴンガス単独、アルゴンガスに０．６、１５、２０ｍｏｌ％の窒素ガスを混合したガスを用いた場合の記録膜の組成とオーバーライト繰り返し可能回数を示す。評価はそれぞれのディスクに適した記録条件で行った。またマーク長が約１μｍ、約３μｍのオーバーライトとなる様に記録周波長を調節した。表２より窒素量が１５ｍｏｌ％を越すと繰り返し回数が急激に低下することがわかる。
【００３５】
【表２】

【００３６】
参考例１７
参考例５のターゲット原材料を溶融急冷し、粉砕した後熱処理を行ない、続いて焼結して製造した。これと対比するために熱処理を施さなかった以外は同様にしたターゲット（参考例５と同じもの）を用意した。これらを用いて参考例５と同様のディスクを作製した。ディスクの線速５ｍ／ｓ時のオーバーライト特性を図６（熱処理を行なったもの）、図７（熱処理を施さなかったもの）に示す。
【００３７】
比較例９
参考例１〜１６のターゲットに含まれるＡｇＩｎＴｅ2の結晶子径は４５０Å以下である。参考例９と同一組成のターゲットで結晶子径が約５００Åのものを用意し、これらによって参考例９と同様にしてディスクを作製した。このディスクの線速２ｍ／ｓ時のオーバーライト特性を図８に示した。図８から明らかなように、結晶子径が５００Åのものは４５０Å以下のものに比較して特性が劣ったものである。
【００３８】
参考例１８
参考例５と同一組成で原材料溶融温度を６００℃以上、５８０℃とした以外は参考例５と同様にしてディスクを作製した。
【００３９】
実施例１
ポリカーボネート(1.2mm)／ZnSSiO₂(200nm)／Ag₈In₁₁Sb₄₇Te₃₄(20nm)／ZnSSiO₂(20nm)／A1合金(100nm)／紫外線硬化樹脂層(4μm)という構成の相変化型光ディスクをスパッタリングによって作製した。ただし、紫外線硬化樹脂は、スピンコートによって作製した。第１保護層および第２保護層は、反応圧０．００８ｔｏｒｒ、プラズマ電力１．０ｋＷで作製して、−１３０ＭＰａの応力に制御した。記録層の組成は、Ａｇ−Ｔｅ／２＝−９に制御した。また、この記録層の降伏応力は、２７０ＭＰａであった。このディスクの保存特性および繰返しオーバーライト特性を評価した。評価条件は、線速１．２ｍ／ｓ、オーバーライト記録周波数０．７２ＭＨｚ／０．２０ＭＨｚとした。寿命の判定は、ジッタ１σが１５ｎｓをこえる時間および繰返し回数とした。
その結果、８０℃８５％ＲＨの保存でアーカイバル特性、シェルフ特性、オーバーライトシェルフ特性ともに、２０００時間以上の寿命であった。一方、オーバーライトの繰返し回数は、５０００回程度であった。
【００４０】
実施例２
ポリカーボネート(1.2mm)/ZnSSiO₂(200nm)/Ag₈In₁₁Sb₄₇Te₃₄:N(20nm)/ZnSSiO₂(20nm)/Al合金(100nm)/紫外線硬化樹脂(4μm)という構成の相変化型光ディスクをスパッタリングによって作製した。記録層は、スパッタリングの際、Ｎ₂をＡｒに３％添加して作製した。ただし、紫外線硬化樹脂は、スピンコートによって作製した。第１保護層及び第２保護層は、反応圧０．００８ｔｏｒｒ、プラズマ電力１．０ｋＷで作製して、−１３０ＭＰａの応力に制御した。記録層の組成は、Ａｇ−Ｔｅ／２＝−９に制御した。また、この記録層の降伏応力は、２７０ＭＰａであった。このディスクの保存特性及び繰返しオーバーライト特性を評価した。評価条件は、線速１．２ｍ／ｓ、オーバーライト記録周波数０．７２ＭＨｚ／０．２０ＭＨｚとした。寿命の判定は、ジッタ１σが１５ｎｓをこえる時間および繰返し回数とした。
その結果、８０℃８５％ＲＨの保存でアーカイバル特性、シェルフ特性、オーバーライトシェルフ特性ともに、２０００時間以上の寿命であった。一方、オーバーライトの繰返し回数は、７０００回程度であった。Ｎの添加によって、繰返し特性が向上することが確認された。
【００４１】
実施例３
ポリカーボネート(1.2mm)/ZnSSiO₂(200nm)/Ag₈In₁₁Sb₄₇Te₃₄:Pd(20nm)/ZnSSiO₂(20nm)/Al合金(100nm)/紫外線硬化樹脂(4μm)という構成の相変化型光ディスクをスパッタリングによって作製した。記録層は、スパッタリングの際、記録層のターゲットにＰｄを０．３ｗｔ％添加して作製した。ただし、紫外線硬化樹脂は、スピンコートによって作製した。第１保護層及び第２保護層は、反応圧０．００８ｔｏｒｒ、プラズマ電力１．０ｋＷで作製して、−１３０ＭＰａの応力に制御した。記録層の組成は、Ａｇ−Ｔｅ／２＝−９に制御した。また、この記録層の降伏応力は、２７０ＭＰａであった。このディスクの保存特性及び繰返しオーバーライト特性を評価した。評価条件は、線速１．２ｍ／ｓ、オーバーライト記録周波数０．７２ＭＨｚ／０．２０ＭＨｚとした。寿命の判定は、ジッタ１σが１５ｎｓをこえる時間および繰返し回数とした。
その結果、８０℃８５％ＲＨの保存でアーカイバル特性、シェルフ特性、オーバーライトシェルフ特性ともに、２０００時間以上の寿命であった。一方、オーバーライトの繰返し回数は、７０００回程度であった。Ｐｄの添加によって、繰返し特性が向上することが確認された。
【００４２】
実施例４
ポリカーボネート(1.2mm)/ZnSSiO₂(200nm)/Ag₈In₁₁Sb₄₇Te₃₄(17nm)/ZnSSiO₂(20nm)/Al合金(100nm)/紫外線硬化樹脂(4μm)という構成の相変化型光ディスクをスパッタリングによって作製した。ただし、紫外線硬化樹脂は、スピンコートによって作製した。第１保護層及び第２保護層は、反応圧０．００８ｔｏｒｒ、プラズマ電力１．０ｋＷで作製して、−１３０ＭＰａの応力に制御した。記録層の組成は、Ａｇ−Ｔｅ／２＝−９に制御した。また、この記録層の降伏応力は、２９０ＭＰａであった。このディスクの保存特性及び繰返しオーバーライト特性を評価した。評価条件は、線速１．２ｍ／ｓ、オーバーライト記録周波数０．７２ＭＨｚ／０．２０ＭＨｚとした。寿命の判定は、ジッタ１σが１５ｎｓをこえる時間および繰返し回数とした。
その結果、８０℃８５％ＲＨの保存はアーカイバル特性、シェルフ特性、オーバーライトシェルフ特性ともに、２０００時間以上の寿命であった。一方、オーバーライトの繰返し回数は、８０００回程度であった。
【００４３】
実施例５
ポリカーボネート(1.2mm)/ZnSSiO₂(200nm)/Ag₈In₁₁Sb₄₇Te₃₄(17nm)/ZnSSiO₂(20nm)/Al合金(100nm)/紫外線硬化樹脂(4μm)という構成の相変化型光ディスクをスパッタリングによって作製した。ただし、紫外線硬化樹脂は、スピンコートによって作製した。第１保護層及び第２保護層は、反応圧０．００８ｔｏｒｒ、プラズマ電力０．８ｋＷで作製して、−１００ＭＰａの応力に制御した。記録層の組成は、Ａｇ−Ｔｅ／２＝−９に制御した。また、この記録層の降伏応力は、２９０ＭＰａであった。このディスクの保存特性及び繰返しオーバーライト特性を評価した。評価条件は、線速１．２ｍ／ｓ、オーバーライト記録周波数０．７２ＭＨｚ／０．２０ＭＨｚとした。寿命の判定は、ジッタ１σが１５ｎｓをこえる時間および繰返し回数とした。
その結果、８０℃８５％ＲＨの保存でアーカイバル特性、シェルフ特性、オーバーライトシェルフ特性は、ともに２０００時間以上の寿命であった。また、オーバーライトの繰返し回数は、１００００回程度であった。
【００４４】
参考例１９
参考例３において、ターゲットを用いてスパッタリングを行なう際の背圧と得られた記録層のＣ／Ｎの関係を図９に示す。
なお、背圧以外のスパッタリングの条件、記録媒体の層構成、評価条件等は実施例３と同様に行なった。その結果、図９に示したように３×１０^-7≦Ｐ≦５×１０^-8ｔｏｒｒの範囲の背圧でスパッタした時、良好なＣ／Ｎを示す記録層を得ることができた。
【００４５】
【発明の効果】
本発明によって、Ｃ／Ｎ、消去比、感度、ジッター、保存信頼性、繰返し信頼性に優れる情報記録媒体を提供することができた。とくに、保存信頼性、繰返し信頼性の大幅な向上ができた。
【図面の簡単な説明】
【図１】Ａｇ−Ｉｎ−Ｓｂ−Ｔｅ系相変化型光ディスクの保存特性を示したもので、（ａ）はアーカイバル特性、（ｂ）はシェルフ特性、（ｃ）はオーバーライトシェル特性、をそれぞれ表わした図。
【図２】オーバーライトシェルフの初期劣化速度の記録層組成依存性を表わした図。
【図３】（ａ）は未記録時で記録層に応力が生じない状態を表わした図、（ｂ）はレーザービーム照射（記録時）に記録層に大きな引っ張り応力が生じることを表わした図。
【図４】保護層の応力と光記録媒の繰り返し回数との関係を表わした図。
【図５】Ａｇ−Ｉｎ−Ｓｂ−Ｔｅ膜の膜厚と降伏応力との関係を表わした図。
【図６】ターゲット材料を製造する際、焼結前に熱処理を行ったターゲットを用いてつくった光記録媒体の性能を表した図。
【図７】ターゲット材料を製造する際、熱処理を行わなかったターゲットを用いてつくった光記録媒体の性能を表した図。
【図８】同一組織のターゲットで結晶子径を５００Åとして光記録媒体をつくり、その性能を表した図。
【図９】ターゲットを用いてスパッタリングを行なう際の背圧と得られた記録層のＣ／Ｎの関係を示す図。[0001]
[Industrial application fields]
The present inventionIs lightRecording mediumTo the bodyMore specifically, an information recording medium (optical recording medium) that causes phase change in the recording layer material by irradiating a light beam, records and reproduces information, and is rewritable.Body)Related.
[0002]
[Prior art]
As one of optical recording media capable of recording, reproducing and erasing information by irradiation with electromagnetic waves, particularly laser beams, so-called phase change type optical recording media utilizing the transition between crystal-amorphous phase or crystal-crystal phase are often used. Are known. In particular, since it is possible to perform overwriting with a single beam, which is difficult with magneto-optical memory, and because it is simpler than the optical system on the drive side, its research and development has recently been actively carried out.
[0003]
Typical examples thereof include so-called chalcogen-based alloy materials such as GeTe, GeTeSe, GeTeS, GeSeS, GeSeSb, GeAsSe, InTe, SeTe, and SeAs as disclosed in USP 3530441. Further, for the purpose of improving stability, high-speed crystallization, etc., Ge (Te 6-2119692), Sn and Au (JP 61-270190), Pd (JP 62-190190) are added to the Ge-Te system. Materials with added composition ratios of GeTeSeSb and GeTeSb for the purpose of improving the recording / erasing repetition performance (Japanese Patent Laid-Open Nos. 62-73438 and 63-228433). ) Has also been proposed.
[0004]
However, none of them can satisfy all the characteristics required for a rewritable phase change optical recording medium. In particular, improvement of recording sensitivity and erasing sensitivity and prevention of reduction in erasing ratio due to remaining erasing at the time of overwriting are the most important issues to be solved.
[0005]
In order to solve these problems, Ag-In-Sb-Te based mixed phase recording materials have been developed (JP-A-3-240590, JP-A-4-78031, JP-A-4-232777, JP-A-5-230). -345478 etc.). These mixed phase recording materials have recording sensitivity and erasing sensitivity with a peak power of 12 mW or less. In particular, it has a large erasure ratio and is excellent as a recording layer for mark edge recording. However, the storage reliability and repetitive reliability of the optical recording medium using the currently proposed Ag-In-Sb-Te-based mixed phase material as the recording layer are not satisfactory, and further improvements are required. ing.
[0006]
[Problems to be solved by the invention]
The object of the present invention has been made in view of the above circumstances,In an optical recording medium having a recording layer made of an Ag—In—Sb—Te mixed phase material,Excellent storage reliability and repeatabilityIn particular, the initial deterioration was suppressedInformation recording mediumBodyIt is to provide.
[0007]
[Means for Solving the Problems]
  As a result of intensive studies on the optical recording medium, the present inventors have found an optical recording medium that meets the above-mentioned problems. That is, according to the present invention, the following optical recording medium is provided.
  (1) An optical recording medium for recording and erasing by the phase change of the substance responsible for recordingThe basic layer structure is polycarbonate substrate / first protective layer / recording layer / second protective layer / reflection heat radiation layer / ultraviolet curable resin, the recording layer has a thickness of 8 to 30 nm, and the recording layer Constituent elements ofContain Ag, In, Te, and Sb, and the composition ratios α, β, γ, and δ (atomic%) are
        0 <α ≦ 30
        0 <β ≦ 30
      10 <γ ≦ 50
      10 <δ ≦ 80
      α-γ / 2 ≦ -8
      α + β + γ + δ = 100
An optical recording medium characterized by the above.
  (2) The optical recording medium according to (1), wherein the thermal stress + intrinsic stress of the first protective layer and the second protective layer is −150 MPa or more.
  (3) The optical recording medium according to (1), wherein the recording layer has a yield stress of 200 MPa or more.
  (4) In any one of the above (1) to (3), an element that can be alloyed or compounded with any of Ag, In, Te, and Sb that are constituent elements of the recording layer is further added. Optical recording media.
[0009]
  (5) An optical recording medium that performs recording and erasing by phase change of a substance that carries recordingThe basic layer structure is polycarbonate substrate / first protective layer / recording layer / second protective layer / reflection heat radiation layer / ultraviolet curable resin layer, and the thickness of the recording layer is 8 to 30 nm ”, and Constituent elements of the recording layerContains Ag, In, Te, Sb, nitrogen and / or oxygen, and each composition ratio α, β, γ, δ, ε (ε is the total of nitrogen and / or oxygen) (atomic%),
        0 <α ≦ 30
        0 <β ≦ 30
        9 <γ ≦ 50
        9 <δ ≦ 80
        0 <ε ≦ 5
        α-γ / 2 ≦ -8
        α + β + γ + δ + ε = 100
An optical recording medium characterized by the above.
  (6) The optical recording medium according to (5), wherein the thermal stress + intrinsic stress of the first protective layer and the second protective layer is −150 MPa or more.
  (7) The optical recording medium according to (5), wherein the recording layer has a yield stress of 200 MPa or more.
  (8)In any one of the above (5) to (7),An optical recording medium, further comprising an element that can be alloyed or compounded with any of Ag, In, Te, and Sb that are constituent elements of the recording layer.
[0010]
The recording layer in the optical recording medium of the present invention comprises (vi) the recording layer.StructureA nitride and / or oxide or nitrogen alone of at least one element of the constituent elements Ag, In, Te, and Sb is contained (the nitride, oxide, or nitrogen alone forms a grain boundary or interface of the recording layer). Forming).
[0011]
Used when producing the recording layer of the optical recording medium of the present inventionGood disk characteristics can be obtainedSputteringThe target composition is 2 ≦ α ≦ 30, 3 ≦ β ≦ 30, 10 ≦ γ ≦ 50, 15 ≦ δ ≦ 83, and α + β + γ + δ = 100. To obtain better disk characteristics, 2 ≦ α ≦ 27, 5 ≦ β ≦ 28, 13 ≦ γ ≦ 45, 20 ≦ δ ≦ 75, α + β + γ + δ = 100, and in order to obtain the best disk characteristics, 2 ≦ α ≦ 25, 8 ≦ β ≦ 25, 15 ≦ γ ≦ 40, 25 ≦ δ ≦ 65. The target composition most suitable for recording conditions such as a desired linear velocity and mark length can be selected according to the disk constituent material other than the recording layer such as the protective layer and the reflective layer, and the film thickness thereof.
[0012]
BookIn the sputtering target of the inventionThe LordStoichiometric composition having Sb and chalcopyrite structure and / or AgInTe having a composition close thereto₂And are preferably present. In this case, the microcrystalline AgSbTe is mainly formed by performing an appropriate heat treatment (initialization) after installing the thin recording layer.₂And a mixed phase composed of amorphous In—Sb can be obtained. By making this mixed phase state exist in the recording layer, it is possible to obtain an optical recording medium having a high erasure ratio and capable of repeating recording and erasing many times with low power.
[0013]
AgInTe having a stoichiometric composition having a chalcopyrite structure and / or a composition close thereto₂The crystallite grain size can be calculated from, for example, the line width of the main park (about 24.1 ° in the case of X-ray source Cu, λ≈1.54 mm) obtained by pulverizing the target and X-ray diffraction. . In the calculation, it is necessary to correct the line width with a reference sample having a sufficiently large crystallite diameter. AgInTe₂When the crystallite grain size is 450 mm or more, it is difficult to obtain a mixed phase state in which stable recording and erasure can be performed even if an appropriate treatment is performed after a thin recording layer is provided.
[0014]
SaidWhen a recording layer is formed using a sputtering targetIfBack pressure p before puttering is 3 × 10^-7≦ p ≦ 5 × 10^-6Although it is preferably Torr, when the back pressure is set to a value within this range, an appropriate discontinuous phase (barrier) is formed in the film, and AgInTe₂From the amorphous phase of Sb and Sb, microcrystalline AgSbTe₂And a mixed phase state of amorphous In—Sb are easily obtained. Further, as a gas at the time of sputtering, the composition of the recording layer after film formation is adjusted according to the amount of nitrogen by using a gas in which nitrogen gas is mixed with 0 mol% or more and 15 mol% or less in argon gas, and the linear velocity, layer configuration, A recording layer most suitable for the use conditions of the disc can be obtained. Further, by using a mixed gas of nitrogen gas and argon gas, the durability of repeated recording and erasure is improved. As the mixed gas, a gas mixed in advance at a desired molar ratio may be used, or the flow rate may be adjusted so that the desired molar ratio is obtained when the chamber is introduced.
[0015]
TheAs the electromagnetic wave used for the processing (initialization), recording, reproducing and erasing of the recording layer formed by the sputtering target and its manufacturing method, the film forming method, laser beam, electron beam, X-ray, ultraviolet ray, visible ray, infrared ray, Various things, such as a microwave, are employable. In particular, as an electromagnetic wave used for recording, reproduction, and erasing, a small and compact semiconductor laser is optimal when mounted on a drive.
[0016]
ThePattering targetToThe film thickness of the formed recording layer is 80 to 5000 mm, preferably 150 to 1000 mm. If the thickness is less than 80 mm, the light absorption ability is remarkably lowered, and the role as a recording layer cannot be achieved. On the other hand, if it is thicker than 5000 mm, uniform phase change is difficult to occur at high speed.
[0017]
By the way, the present inventionAg-In-Sb-Te phase changeTypeThe main technical issues of optical recording media are (1) storage reliability and (2) repeated overwriting reliability.SexImprovementThe purpose is to achieve.
[0018]
So, first, Ag-In-Sb-Te phase changeTypeThe optical recording medium was examined for storage deterioration behavior at 80 ° C. and 85% RH. The evaluation items here are archival characteristics (characteristics of stored recording signals), shelf characteristics (recording characteristics to stored initialization sections), and overwrite shelf characteristics (overwrite recording characteristics to stored recording signal sections). ). The evaluation conditions were a linear velocity of 1.2 m / s and an overwrite recording frequency of 0.72 MHz / 0.20 MHz. The evaluated samples are the following five types.
No. Configuration (film thickness nm)
1 (○) PC / ZnSSiO₂(200) / Ag₈In₁₅Sb₄₃Te₃₄(35) / AIN (30) / Ag (70)
2 (△) PC / ZnSSiO₂(200) / Ag₈In₁₁Sb₄₉Te₃₂(30) / ZnSSiO₂(20) / Al alloy (100)
3 (▲) PC / ZnSSiO₂(200) / Ag₈In₁₁Sb₄₉Te₃₂(20) / ZnSSiO₂(20) / Al alloy (100)
4 (□) PC / ZnSSiO₂(200) / Ag₁₁In₁₄Sb₄₃Te₃₂(30) / ZnSSiO₂(20) / Al alloy (100)
5 (■) PC / ZnSSiO₂(200) / Ag₁₁In₁₄Sb₄₃Te₃₂(20) / ZnSSiO₂(20) / Al alloy (100)
PC means a polycarbonate substrate, and the composition of the recording layer was evaluated by ICP analysis. Each disk was provided with 4 μm of UV curable resin.
[0019]
These five types of storage deterioration behavior are shown in FIG. Figure 1 shows Ag-In-Sb-Te phase changeTypeThe storage characteristics of the optical disk are shown. (A) shows the archival characteristics, FIG. 1 (b) shows the shelf characteristics, and FIG. 1 (c) shows the overwrite shelf. As is clear from FIG. 1, as the deterioration mode,
(1) Initial deterioration of overwrite shelf (about 200 hours)
(2) Medium-term deterioration of archival characteristics (approximately 1000 hours)
Was recognized. Above all, it was found that the initial deterioration of the overwrite shelf is a big problem.
[0020]
Subsequently, in order to take measures against the initial deterioration of the overwrite shelf, the deterioration was analyzed. As a result, it was found that there was a site that was insufficiently amorphized by high temperature and high humidity storage at 80 ° C. and 85% RH. It was also found that the deterioration rate depends on the composition of the recording layer. This is shown in FIG. FIG. 2 shows that the initial deterioration of the overwrite shelf is greatly improved when Ag—Te / 2 (atomic%) is −8 or less. In addition, it can be seen that the initial deterioration of the overwrite shelf is not significantly dependent on the layer structure such as the film thickness of the recording layer, the second protective layer material, and the reflective heat radiation layer material.
[0021]
Next, Ag-In-Sb-Te phase changeTypeThe repetition characteristics of optical recording media were investigated. When the structure of the recording layer after repeated overwriting was observed with a transmission electron microscope and subjected to electron beam diffraction, (1) formation of voids and (2) composition compilation were observed.
The formation of voids and compositional knitting are phenomena that are integrated on the front and back, and the movement source of the substance is a void, and the movement destination is observed as knitting of the composition. In other words, the mass transfer is a deterioration of the repetition characteristics of the overwrite. This driving force of mass transfer is considered to be caused by a tensile stress gradient generated in the recording layer (C. Herring, J. Appl. Phys., 21, 437 (1950)).
[0022]
Phase changeTypeIn the optical recording medium, the recording layer is melted by laser irradiation during recording. At that time, the tensile stress in the melted portion is almost eliminated, and a large tensile stress gradient is generated (FIG. 3B). The tensile stress generated in the recording layer is determined by the sum of thermal stress and intrinsic stress (particularly compressive stress) of the first protective layer and the second protective layer. Therefore, the reduction of the tensile stress of the recording layer is nothing but the reduction of the thermal stress and the compressive stress of the first protective layer and the second protective layer. FIG. 3A shows a state where no recording is performed, that is, no stress is generated.
[0023]
FIG. 4 shows the relationship between the number of overwrite repetitions and the stress of the first protective layer. When the number of repetitions is 2000 times or more, the stress of the protective layer is thermal stress + intrinsic stress, −150 MPa or more, and when the number of repetitions is 10000 times or more, the stress of the protective layer is thermal stress + intrinsic stress, − 100 MPa or more is suitable.
[0024]
Further, if the tensile stress generated in the recording layer exceeds the yield stress of the recording layer, the recording layer will eventually cause a void and break. Therefore, the yield stress of the recording layer must be larger than the tensile stress generated in the recording layer. FIG. 5 shows the relationship between the film thickness of the Ag—In—Sb—Te recording layer and its yield stress. The tensile stress generated in the Ag—In—Sb—Te recording layer is 150 to 250 MPa, and the yield stress of the recording layer needs to be higher. That is, the recording yield stress is preferably 200 MPa or more, more preferably 250 MPa or more. Therefore, the thickness of the Ag—In—Sb—Te-based recording layer is 500 nm or less, preferably 30 nm or less.
[0025]
On the other hand, voids formed by repeated overwriting are promoted by using different materials for the first protective layer and the second protective layer. In phase change optical recording media, if the protective layer material that sandwiches the recording layer is different, the wettability differs between the top and bottom of the recording layer, so the recording material moves to an interface with better wettability during melting during recording erasure. As a result, voids are formed at the interface with poor wettability. As a result, deterioration due to repeated overwriting occurs. Therefore, by using the same material for the first protective layer and the second protective layer, it is possible to improve the repetition characteristics of the overwrite.
Further, if the thermal conductivity of the first protective layer and the second protective layer are different, thermal stress distribution is generated, which also causes mass transfer. Therefore, also from such a viewpoint, it is desirable that the first protective layer and the second protective layer are made of the same material.
[0026]
Ag-In-Sb-Te phase changeTypeThe recording material is AgSbTe as described in JP-A-4-78031.₂It is known that a mixed phase structure of InSb is formed. For optical recording, AgSbTe₂Changes between crystalline and amorphous. AgSbTe at this time₂Is approximately 10 nm. In such a multiphase structure, the mass transfer amount is considered to be dominant at the multiphase interface. The amount of mass transfer increases due to the tensile stress generated in the recording layer.
Now, mass transfer is also mitigated by supplementing the mass transfer path with a mass transfer path. Specifically, each element of carbon, nitrogen, and oxygen has tetravalent, trivalent, and divalent bonds, and can supplement the mobile substance. In addition, addition of Al, Ga, Se, Ge, Pd, Pb, or the like that can be alloyed or compounded with any of the constituent elements of Ag, In, Sb, and Te is also effective.
[0027]
The recording layer used in the present invention contains Ag, In, Sb, and Te as main constituent elements. Phase changeTypeAs a recording medium, a suitable composition is

In this composition range, the present invention is a composition range suitable for further ensuring storage reliability. Further, the recording layer of the present invention can contain additional elements such as C, N, O, Al, Ga, Se, Ge, Pd, and Pb. The recording layer can be produced by sputtering, ion plating, vacuum deposition, plasma CVD, or the like. For the addition of C, N and O, CH_Four, N₂, NH_Three, NO₂, N₂O can be used.
[0028]
The material of the substrate used in the present invention is usually glass, ceramics, or resin, and among them, the resin substrate is preferable in terms of moldability and cost. As typical examples of the resin, polycarbonate resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polymethyl methacrylate resin, and the like can be used, but polycarbonate resin is preferable from the viewpoint of processability and optical characteristics. Further, the shape of the substrate may be a disk shape, a card shape, or a sheet shape. Any substrate thickness of 1.2 mm, 0.6 mm, 0.3 mm, or the like can be used, but a substrate having a smaller substrate thickness is desired from the viewpoint of substrate tilt dependency of crosstalk. However, considering the difficulty in film formation and the yield, 0.6 mm is preferable.
[0029]
The first and second protective layers used in the present invention are SiO, SiO₂ZnO, SnO₂, Al₂O_ThreeTiO₂, In₂O_Three, MgO, Zro₂Oxides such as Si_ThreeN_Four, Nitrides such as AIN, TiN, BN, ZrN, ZnS, In₂S_Three, TaS_FourSuch as sulfide, SiC, TaC_Four, B_FourCarbides such as C, WC, TiC, ZrC, diamond-like carbon, or mixtures thereof are preferred. These first and second protective layers can be produced by sputtering, ion plating, vacuum deposition, plasma CVD, or the like. The thickness of the first protective layer is 50 nm to 500 nm, preferably 100 nm to 300 nm, more preferably 120 nm to 250 nm. The thickness of the second protective layer is 5 nm to 300 nm, preferably 10 nm to 50 nm.
In the case of sputtering deposition, the stress of the first and second protective layers can be controlled by deposition pressure, deposition power, substrate-target distance, and the like. Generally, the stress is reduced by increasing the deposition pressure, decreasing the deposition plasma power, and increasing the distance between the substrate and the target. Further, the stress can be reduced by using two or more kinds of composite materials.
[0030]
As the reflective heat dissipation layer, metal materials such as Al, Ag, and Au and additive materials such as Ti, Cr, and Si can be used. The reflective heat radiation layer is not necessarily required, but it is desirable to provide it in order to release excessive heat generated at the time of recording and erasing and reduce thermal damage to the recording medium itself. The reflective heat dissipation layer can be produced by sputtering, ion plating, vacuum deposition, plasma CVD, or the like.
[0031]
less than,Reference examples andThe present invention will be specifically described with reference to examples.
[0032]
Reference Examples 1-16Comparative Examples 1-8
Table 1 shows a stoichiometric composition having a chalcopyrite structure and / or an AgInTe composition close thereto.₂The composition of the sputtering target in which and are present, and the disk characteristics when using them are shown. This is a disk substrate (thickness 1.2 mm) on which a groove having a width of about 0.6 μm and a depth of about 600 mm is formed.₂200 nm-thick lower protective layer, 25 nm-thick recording layer, ZnS · SiO₂An upper protective layer made of 30 nm thick, a reflective heat radiation layer made of an aluminum alloy (thickness 100 nm), and a protective layer made of an ultraviolet curable resin (thickness 5 μm) are installed to make a disk. The recording layer sputtering method uses a back pressure of 9 × 10.^-7Argon gas is added at 4 torr.^-3Torr and RFpower 40 watts.
This disk was measured at the linear velocity at which the C / N was highest, and the recording characteristics of a mark having a mark length of about 1 μm and the erasing characteristics when overwritten with a mark of about 3 μm were evaluated. Here, the wavelength of the semiconductor laser is 780 nm, and the NA of the objective lens is 0.5.
The evaluation value in the column of the disk characteristics indicates that level 3 is a target exhibiting the best characteristics (C / N ≧ 55 dB, erase ratio (Ers) ≦ −35 dB), and level 2 is a target with good characteristics (55> C / N ≧ 45 dB, −35 <erase ratio (Ers) ≦ −25 dB), and level 1 is a target for which a disk having good characteristics was not obtained (other than the above) It shows that.
The composition ratios α, β, γ, and δ (atomic%) of Ag, In, Te, and Sb are 2 ≦ α ≦ 30, 3 ≦ β ≦ 30, 10 ≦ γ ≦ 50, and 15 ≦ δ ≦ 83, respectively.TargetWhenA recording layer having a composition ratio defined in the present invention is obtained,It can be seen that good disk characteristics are obtained.
[0033]
[Table 1]

[0034]
Table 2Reference exampleWhen the recording layer was formed by sputtering using the target No. 3, the composition and the overwrite of the recording film in the case of using argon gas alone, or a gas in which argon gas was mixed with 0.6, 15, or 20 mol% nitrogen gas was used. Indicates the number of repetitions. Evaluation was performed under recording conditions suitable for each disc. The recording peripheral wavelength was adjusted so that the mark length was about 1 μm and the overwrite was about 3 μm. From Table 2, it can be seen that when the amount of nitrogen exceeds 15 mol%, the number of repetitions rapidly decreases.
[0035]
[Table 2]

[0036]
Reference Example 17
Reference example5 target raw materials were melted, rapidly cooled, pulverized, heat treated, and then sintered. In order to contrast with this, the same target except that no heat treatment was applied (Reference exampleThe same as 5) was prepared. With theseReference exampleA disk similar to that of No. 5 was produced. The overwrite characteristics when the linear velocity of the disk is 5 m / s are shown in FIG. 6 (heat-treated) and FIG. 7 (no heat-treated).The
[0037]
Comparative Example 9
Reference exampleThe crystallite diameter of AgInTe2 contained in the targets 1 to 16 is 450 mm or less.Reference examplePrepare a target with the same composition as 9 and a crystallite diameter of about 500 mm.Reference exampleA disc was produced in the same manner as in Example 9. FIG. 8 shows the overwrite characteristics of this disk when the linear velocity is 2 m / s. As is apparent from FIG. 8, the crystallite diameter of 500 mm is inferior in characteristics to those of 450 mm or less.
[0038]
Reference Example 18
Reference example5 except that the raw material melting temperature is 600 ° C. or higher and 580 ° C.Reference exampleMake a disc as in 5It was.
[0039]
Example 1
  Polycarbonate (1.2mm) / ZnSSiO₂(200nm) / Ag₈In₁₁Sb₄₇Te₃₄(20nm) / ZnSSiO₂(20nm) / A1 alloy (100nm) / A phase change type optical disk having an ultraviolet curable resin layer (4 μm) was prepared by sputtering. However, the ultraviolet curable resin was produced by spin coating. The first protective layer and the second protective layer were produced at a reaction pressure of 0.008 torr and a plasma power of 1.0 kW, and controlled to a stress of −130 MPa. The composition of the recording layer was controlled to be Ag−Te / 2 = −9. Further, the yield stress of this recording layer was 270 MPa. The storage characteristics and repeated overwrite characteristics of this disk were evaluated. The evaluation conditions were a linear velocity of 1.2 m / s and an overwrite recording frequency of 0.72 MHz / 0.20 MHz. Judgment of the lifetime was made the time when the jitter 1σ exceeded 15 ns and the number of repetitions.
  As a result, the storage life of 80 ° C. and 85% RH was such that the archival characteristics, shelf characteristics, and overwrite shelf characteristics were all over 2000 hours. On the other hand, the number of overwriting repetitions was about 5000 times.
[0040]
Example 2
Polycarbonate (1.2mm) / ZnSSiO₂(200nm) / Ag₈In₁₁Sb₄₇Te₃₄: N (20nm) / ZnSSiO₂Phase change of composition of (20nm) / Al alloy (100nm) / UV curable resin (4μm)TypeAn optical disk was produced by sputtering. The recording layer is N during sputtering.₂Was prepared by adding 3% to Ar. However, the ultraviolet curable resin was produced by spin coating. The first protective layer and the second protective layer were produced at a reaction pressure of 0.008 torr and a plasma power of 1.0 kW, and controlled to a stress of −130 MPa. The composition of the recording layer was controlled to Ag−Te / 2 = −9. The yield stress of this recording layer was 270 MPa. The storage characteristics and repeated overwrite characteristics of this disk were evaluated. The evaluation conditions were a linear velocity of 1.2 m / s and an overwrite recording frequency of 0.72 MHz / 0.20 MHz. Judgment of the lifetime was made the time when the jitter 1σ exceeded 15 ns and the number of repetitions.
As a result, the storage life of 80 ° C. and 85% RH was such that the archival characteristics, shelf characteristics, and overwrite shelf characteristics were all over 2000 hours. On the other hand, the number of overwriting repetitions was about 7000 times. It has been confirmed that the addition of N improves the repetition characteristics.
[0041]
Example 3
Polycarbonate (1.2mm) / ZnSSiO₂(200nm) / Ag₈In₁₁Sb₄₇Te₃₄: Pd (20nm) / ZnSSiO₂Phase change of composition of (20nm) / Al alloy (100nm) / UV curable resin (4μm)TypeAn optical disk was produced by sputtering. The recording layer was prepared by adding 0.3 wt% Pd to the target of the recording layer during sputtering. However, the ultraviolet curable resin was produced by spin coating. The first protective layer and the second protective layer were produced at a reaction pressure of 0.008 torr and a plasma power of 1.0 kW, and controlled to a stress of −130 MPa. The composition of the recording layer was controlled to be Ag−Te / 2 = −9. Further, the yield stress of this recording layer was 270 MPa. The storage characteristics and repeated overwrite characteristics of this disk were evaluated. The evaluation conditions were a linear velocity of 1.2 m / s and an overwrite recording frequency of 0.72 MHz / 0.20 MHz. Judgment of the lifetime was made the time when the jitter 1σ exceeded 15 ns and the number of repetitions.
As a result, the storage life of 80 ° C. and 85% RH was such that the archival characteristics, shelf characteristics, and overwrite shelf characteristics were all over 2000 hours. On the other hand, the number of overwriting repetitions was about 7000 times. It was confirmed that the repetition characteristics were improved by the addition of Pd.
[0042]
Example 4
Polycarbonate (1.2mm) / ZnSSiO₂(200nm) / Ag₈In₁₁Sb₄₇Te₃₄(17nm) / ZnSSiO₂Phase change of composition of (20nm) / Al alloy (100nm) / UV curable resin (4μm)TypeAn optical disk was produced by sputtering. However, the ultraviolet curable resin was produced by spin coating. The first protective layer and the second protective layer were produced at a reaction pressure of 0.008 torr and a plasma power of 1.0 kW, and controlled to a stress of −130 MPa. The composition of the recording layer was controlled to be Ag−Te / 2 = −9. The yield stress of this recording layer was 290 MPa. The storage characteristics and repeated overwrite characteristics of this disk were evaluated. The evaluation conditions were a linear velocity of 1.2 m / s and an overwrite recording frequency of 0.72 MHz / 0.20 MHz. Judgment of the lifetime was made the time when the jitter 1σ exceeded 15 ns and the number of repetitions.
As a result, storage at 80 ° C. and 85% RH had a lifetime of 2000 hours or more in all of the archival characteristics, shelf characteristics, and overwrite shelf characteristics. On the other hand, the number of overwriting repetitions was about 8000 times.
[0043]
Example 5
Polycarbonate (1.2mm) / ZnSSiO₂(200nm) / Ag₈In₁₁Sb₄₇Te₃₄(17nm) / ZnSSiO₂Phase change of composition of (20nm) / Al alloy (100nm) / UV curable resin (4μm)TypeAn optical disk was produced by sputtering. However, the ultraviolet curable resin was produced by spin coating. The first protective layer and the second protective layer were produced at a reaction pressure of 0.008 torr and a plasma power of 0.8 kW, and controlled to a stress of −100 MPa. The composition of the recording layer was controlled to be Ag−Te / 2 = −9. The yield stress of this recording layer was 290 MPa. The storage characteristics and repeated overwrite characteristics of this disk were evaluated. The evaluation conditions were a linear velocity of 1.2 m / s and an overwrite recording frequency of 0.72 MHz / 0.20 MHz. Judgment of the lifetime was made the time when the jitter 1σ exceeded 15 ns and the number of repetitions.
As a result, the archival characteristics, shelf characteristics, and overwrite shelf characteristics were all over 2000 hours when stored at 80 ° C. and 85% RH. Further, the number of overwriting repetitions was about 10,000.
[0044]
Reference Example 19
Reference example9 shows the relationship between the back pressure when sputtering using the target and the C / N ratio of the obtained recording layer.
The sputtering conditions other than the back pressure, the layer structure of the recording medium, the evaluation conditions, and the like were the same as in Example 3. As a result, as shown in FIG.^-7≦ P ≦ 5 × 10^-8When sputtering was performed at a back pressure in the range of torr, a recording layer showing good C / N could be obtained.
[0045]
【The invention's effect】
According to the present invention, an information recording medium excellent in C / N, erasure ratio, sensitivity, jitter, storage reliability, and repetition reliability can be provided. In particular, storage reliability and repetitive reliability have been greatly improved.
[Brief description of the drawings]
FIG. 1: Ag-In-Sb-Te phase changeTypeFIG. 4 shows storage characteristics of an optical disc, wherein (a) shows archival characteristics, (b) shows shelf characteristics, and (c) shows overwrite shell characteristics.
FIG. 2 is a graph showing the recording layer composition dependence of the initial deterioration rate of the overwrite shelf.
FIG. 3A is a diagram showing a state in which no stress is generated on the recording layer when recording is not performed, and FIG. .
FIG. 4 is a graph showing the relationship between the stress of the protective layer and the number of repetitions of the optical recording medium.
FIG. 5 is a graph showing the relationship between the film thickness of the Ag—In—Sb—Te film and the yield stress.
FIG. 6 is a diagram showing the performance of an optical recording medium manufactured using a target that has been heat-treated before sintering when a target material is manufactured.
FIG. 7 is a diagram showing the performance of an optical recording medium made using a target that has not been heat-treated when producing a target material.
FIG. 8 is a diagram showing the performance of an optical recording medium manufactured with a target having the same structure and a crystallite diameter of 500 mm.
FIG. 9 is a diagram showing a relationship between back pressure when sputtering using a target and C / N of the obtained recording layer.

Claims (6)

In an optical recording medium in which recording and erasing are performed by a phase change of a substance responsible for recording , the basic layer configuration is polycarbonate substrate / first protective layer / recording layer / second protective layer / reflection heat radiation layer / ultraviolet curable resin layer, The recording layer has a thickness of 8 to 30 nm, and the constituent elements of the recording layer contain Ag, In, Te, and Sb, and the respective composition ratios α, β, γ, and δ (atomic%) are:
0 <α ≦ 30
0 <β ≦ 30
10 <γ ≦ 50
10 <δ ≦ 80
α-γ / 2 ≦ -8
α + β + γ + δ = 100
An optical recording medium characterized by the above. In an optical recording medium in which recording and erasing are performed by a phase change of a substance responsible for recording , the basic layer configuration is polycarbonate substrate / first protective layer / recording layer / second protective layer / reflection heat radiation layer / ultraviolet curable resin layer, The recording layer has a thickness of 8 to 30 nm ”, and the constituent elements of the recording layer contain Ag, In, Te, Sb, nitrogen and / or oxygen, and the respective composition ratios α, β, γ, δ , Ε (ε is the total of nitrogen and / or oxygen) (atomic%)
0 <α ≦ 30
0 <β ≦ 30
9 <γ ≦ 50
9 <δ ≦ 80
0 <ε ≦ 5
α-γ / 2 ≦ -8
α + β + γ + δ + ε = 100
An optical recording medium characterized by the above. The optical recording medium according to claim 1, wherein the sum of the thermal stress and the intrinsic stress of the first protective layer and the second protective layer is −150 MPa or more. The optical recording medium according to claim 1, wherein the yield stress of the recording layer is 200 MPa or more. 3. The optical recording medium according to claim 2, wherein the recording layer contains a nitride and / or oxide or nitrogen of at least one of the constituent elements Ag, In, Te, and Sb. 3. The optical recording medium according to claim 1, further comprising an element that can be alloyed or compounded with any of Ag, In, Te, and Sb that are constituent elements of the recording layer.

Images