JP4117878B2 - Write-once optical recording medium and recording method thereof - Google Patents

Description

なお、この記録において、６Ｔは記録極性がＬｏｗ ｔｏ Ｈｉｇｈであり、１４Ｔは記録極性がＨｉｇｈ ｔｏ Ｌｏｗであった。
また、記録マークが１４Ｔの場合は、その記録部の信号振幅（変調度に相当）が、６Ｔの２倍程度あった。
【００４３】
次いで、この光記録媒体をＦＩＢ（Ｆｏｃｕｓｅｄ Ｉｏｎ Ｂｅａｍ＝集束イオンビーム加工装置）でトラック方向、又は半径方向に切断し、記録部をＦＥ−ＳＥＭ（電界放射型走査電子顕微鏡）又はＴＥＭ（透過電子顕微鏡）で観察した。
その結果、図１１（ＦＩＢでトラック方向に切断しＦＥ−ＳＥＭで観察した図）に示すように、記録マーク長が６Ｔの場合は、記録部がＳｉＣ層の基板側への変形、及び色素層の状態変化によって記録部が形成されていることが確認できた。
一方、記録マーク長が１４Ｔの場合には、記録マーク長が６Ｔの場合と比べて記録極性が反転し、変調度が急増した記録部には、図１２〜１３に示すように、基板内に空隙が発生していることが確認できた（マーク長が６Ｔの場合には、基板内に空隙が発生していなかった）。即ち、記録再生特性の悪化の原因は、基板内に発生する空隙であることが確認された。
なお、図１２はＦＩＢで半径方向に切断しＴＥＭで観察した（写真）であり、図１３は同様の観察を行った（写真）の拡大図である（図１３のＴＥＭ写真は、それぞれ切断位置が異なる４枚の写真を並べて示してある。）。
更に、上記実験ではマーク長の違いによって記録極性が異なる例を示したが、記録パワーが低い時と高い時でも同様の現象（高記録パワー時には基板内に空隙が発生する）が起ることを確認した。
【００４４】
実施例１
溝深さ５０ｎｍの案内溝を有するポリカーボネート基板上に、空隙抑制層としてＺｎＳ-ＳｉＯ_２を厚さ６５ｎｍ、光吸収機能を有する層としてＳｉＣを厚さ１０ｎｍ、有機化合物からなる記録層としてＤＶＤ−Ｒに利用できる前記化１で示される化合物のＣｏ金属錯体層（色素層）を厚さ約６０ｎｍ、Ａｇ反射層を厚さ約１００ｎｍ、紫外線硬化型樹脂からなる保護層を順次積層して追記型光記録媒体を作成した。
この光記録媒体に対し、パルステック工業製の光ディスク評価装置、ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、基板側からレーザ光を照射し、グル−ブ部（入射レーザ光側から見て、手前側にある溝位置）に、記録周波数６５．４ＭＨｚ、記録線速度６．０ｍ／ｓで８−１６変調の信号を記録した。
その結果、本実施例で使用した評価装置が設定できる記録パワ−範囲内において、記録極性がＬｏｗ ｔｏ Ｈｉｇｈで単一化され、図１４に示すような、良好なジッタ特性と変調度を得ることができた。
【００４５】
比較例１
基板／ＳｉＣ（厚さ１０ｎｍ）／化１で示される化合物のＣｏ金属錯体（厚さ約６０ｎｍ）／Ａｇ反射層（厚さ１５０ｎｍ）／保護層という構成の追記型光記録媒体を作成し、下記の条件で記録を行った（実施例１において、空隙抑制層がない場合）。
＜記録条件＞
・記録線密度 ：１Ｔ＝０．０９１７μｍ
・変調方式 ：８−１６変調
・記録ストラテジ：Ｂａｓｉｃ ｓｔｒａｔｅｇｙ（基本ストラテジ）
Ｔｏｐ−Ｔｍｐ＝１．２０−０．６０（Ｔ）
その結果は図１５に示す通りで、記録パワー約９．０ｍＷでジッタ１１．６％という良好な記録を行うことができたが、本比較例で使用した評価装置が設定できる記録パワーの範囲内において、記録極性の変化が見られ（１０．５ｍｗ近傍で記録極性がＬｏｗ ｔｏ ＨｉｇｈからＨｉｇｈ ｔｏ Ｌｏｗに変わる）、ジッタの記録パワーマージンが非常に狭くなったことが確認できた。
この光記録媒体に、改めて記録パワー８．０ｍＷで６Ｔマーク及び１４Ｔマークを記録し、参考例３と同様に、この光記録媒体をＦＩＢで半径方向に切断し、記録部をＴＥＭで観察した。
その結果、記録パワー８．０ｍＷによる記録部では、基板内に空隙が発生していないことが確認できた。また、記録再生時にトラッキングエラ−（トラック外れ）を生じることがなかった。
一方、図１２〜１３のように基板内に空隙が発生するような記録パワー、即ち記録パワー９．５ｍＷ以上による記録では、ジッタが１５．０％を下回らなかった。また、９．５ｍＷ程度以上の記録パワーでは、記録パワーの増加と伴に、記録再生時のトラッキングエラ−（トラック外れ）を起す割合が増加した。
【００４６】
実施例２
溝深さ５０ｎｍの案内溝を有するポリカーボネート基板上に、空隙抑制層としてＺｒＯ_２を厚さ３５ｎｍ、光吸収機能を有する層としてＳｉを厚さ１５ｎｍ、有機化合物からなる記録層としてＤＶＤ−Ｒに利用できる前記化１で示される化合物のＣｏ金属錯体層（色素層）を厚さ約６０ｎｍ、Ａｇ反射層を厚さ約１００ｎｍ、紫外線硬化型樹脂からなる保護層を順次積層した追記型光記録媒体を作成した。
この光記録媒体に対し、パルステック工業製の光ディスク評価装置、ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、基板側からレーザ光を照射し、グル−ブ部（入射レーザ光側から見て、手前側にある溝位置）に、記録周波数６５．４ＭＨｚ、記録線速度６．０ｍ／ｓで８−１６変調の信号を記録した。
その結果、本実施例で使用した評価装置が設定できる記録パワ−範囲内において、記録極性がＬｏｗ ｔｏ Ｈｉｇｈで単一化され、図１６に示すような、良好なジッタ特性と変調度を得ることができた。
【００４７】
以上の参考例及び実施例の結果から、本発明の「基板又はカバー層に隣接して、記録光に対して光吸収機能を有する光吸収層が設けられた構造を有し、基板内又はカバー層内に空隙部を形成させずに記録部を形成した追記型光記録媒体」が、良好な記録再生特性を得る上で、非常に重要であることが裏付けられた。
なお、上記実施例の記録再生特性は一例を示すものであって、例えば記録極性をＬｏｗ ｔｏ Ｈｉｇｈに限定するものではない。
【００４８】
実施例３
図１１〜１３の観察の結果、基板内に空隙が発生し易いのは長マークであり、３Ｔ〜４Ｔのような短い記録マークには空隙が発生し難いことが確認できた。
そこで、図１５（ａ）に示すような記録ストラテジにおいて、長マークになるほどＴＥＭＰを０．０２（Ｔ）ずつ小さくする設定を用い、長マークの温度を必要以上に上昇させない（基板内に空隙が発生しない温度以下にする）ようにし、比較例１で作成したものと同じ構成の追記型光記録媒体に記録を行った。
その結果、通常の記録ストラテジ〔図１７（ａ）において、記録マーク長に拘わらずＴＥＭＰを固定〕では、約９．５ｍＷ程度で、１４Ｔマークに基板内空隙が観測されたが、本実施例での記録ストラテジを用いることにより、約９．５ｍＷ程度で記録を行っても１４Ｔマークに基板内空隙は観測されなかった。
即ち、本実施例で適用した記録ストラテジを用いることで、記録パワーを増加していっても、長マークに発生し易い空隙の発生を抑制できるため、良好なジッタ特性（ジッタの記録パワーマージンの拡大）が得られた。
なお、本実施例で用いた記録ストラテジ以外に、例えば次のイ）〜リ）などの設定でも、同様の効果を発揮する。
・図１７（ａ）において、
イ）長マークほどＴＥＬＰを小さくする。
ロ）長マークほどＴＥＦＰを小さくする。
ハ）長マークほどＰｗ１又はＰｗ２を低くする。
・図１７（ｂ）において、
ニ）長マークほどＰｗ１又はＰｗ２を小さくする。
ホ）長マークほどＴＥＦＰを小さくする。
・図１７（ｃ）において、
ヘ）長マークほどＰｗ１又はＰｗ２を小さくする。
ト）長マークほどＴＥＦＰを小さくする。
チ）長マークほどＴＥＬＰを小さくする。
リ）長マークほどＴＳＬＰを大きくする。
なお、本発明で有効な記録ストラテジの設定は、本実施例で説明したものに限定されるものではない。
【００４９】
上記参考例及び実施例では、光吸収層が基板と接する場合を取り上げたが、カバー層の場合も、基本的に基板と材料が同一であるため、カバー層と光吸収層が接する場合も同様である。
なお、本発明は、基板又はカバー層に隣接して、記録光に対して光吸収機能を有する光吸収層が設けられた構造を有する追記型光記録媒体の記録再生特性の改善を図る一つの有効な方法を示したものであって、基板内の空隙の発生がある追記型光記録媒体を否定するものではない。
また、記録極性は、色素層や光吸収層の光学定数や膜厚、光吸収層の変形形態、或いは基板の溝深さ等の形状などに依存するため、実施例における構造の追記型光記録媒体の記録極性を限定するものではない。
【００５０】
【発明の効果】
本発明の追記型光記録媒体とその記録方法によって、記録再生特性を悪化させる基板内又はカバー層内の空隙発生を抑制することが可能となるため、良好な記録再生特性、及び良好なトラッキング特性が得られる短波長レーザ対応の追記型光記録媒体とその記録方法を提供できる。
【図面の簡単な説明】
【図１】従来のディスクの層構成を示す図。
【図２】マーク長記録の記録マークを再生した場合の再生信号の波形を説明する図。
（ａ） 一般的な場合
（ｂ） 記録マークの前後エッジ近傍で変極点を持つ微分波形
（ｃ） 記録マークの中心近傍で変極点を持つ微分波形
【図３】参考例１−Ａの記録結果を示す図。
（ａ） 記録マーク長と再生信号（ＲＦレベル）及び変調度の関係を示す。
（ｂ） ３Ｔマーク、４Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｃ） ６Ｔマーク、８Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｄ） ３Ｔマーク、１４Ｔマークを連続して記録した場合の再生信号、及び未記録時の再生信号レベルを示す。
【図４】参考例１−Ｂの記録結果を示す図。
（ａ） 記録マーク長と再生信号（ＲＦレベル）及び変調度の関係を示す。
（ｂ） ３Ｔマーク、４Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｃ） ６Ｔマーク、８Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｄ） ３Ｔマーク、１４Ｔマークを連続して記録した場合の再生信号、及び未記録時の再生信号レベルを示す。
【図５】参考例１−Ｃの記録結果を示す図。
（ａ） 記録マーク長と再生信号（ＲＦレベル）及び変調度の関係を示す。
（ｂ） ３Ｔマーク、４Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｃ） ６Ｔマーク、８Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｄ） ３Ｔマーク、１４Ｔマークを連続して記録した場合の再生信号、及び未記録時の再生信号レベルを示す。
【図６】参考例１−Ｄの記録結果を示す図。
（ａ） 記録マーク長と再生信号（ＲＦレベル）及び変調度の関係を示す。
（ｂ） ３Ｔマーク、４Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｃ） ６Ｔマーク、８Ｔマークを連続して記録した場合の再生信号、及び、未記録時の再生信号レベルを示す。
（ｄ） ３Ｔマーク、１４Ｔマークを連続して記録した場合の再生信号、及び未記録時の再生信号レベルを示す。
【図７】Ｐｉｔが形成された状態における溝パラメータの説明図。
【図８】空隙の有り無しの記録状態を説明するための図。
（ａ） 空隙無しの記録状態
（ｂ） 空隙有りの記録状態
【図９】参考例２において、ランド部にＰｉｔが形成された記録部を基板側から再生した場合の結果を示す図。
【図１０】参考例２において、グル−ブ部にＰｉｔが形成された記録部を基板側から再生した場合の結果を示す図。
【図１１】参考例３の記録マーク長が６Ｔの場合について、光記録媒体をＦＩＢでトラック方向に切断しＦＥ−ＳＥＭで観察した図。
（ａ）記録部を観察した図
（ｂ）未記録部を観察した図
【図１２】参考例３の記録マーク長が１４Ｔの場合について、光記録媒体をＦＩＢで半径方向に切断しＦＥ−ＳＥＭで観察した図。
【図１３】参考例３の記録マーク長が１４Ｔの場合について、光記録媒体をＦＩＢでトラック方向に切断しＦＥ−ＳＥＭで観察した図。
【図１４】実施例１の光記録媒体に記録を行った場合のジッタ、及びスペース部とマーク部の再生信号レベルを示す図。
【図１５】比較例１の光記録媒体に記録を行った場合のジッタ、及びスペース部とマーク部の再生信号レベルを示す図。
【図１６】実施例２の光記録媒体に記録を行った場合のジッタ、及びスペース部とマーク部の再生信号レベルを示す図。
【図１７】参考例３で用いた記録ストラテジを示す図。
（ａ） 通常の記録ストラテジ
（ｂ） 他の記録ストラテジ
（ｃ） 更に他の記録ストラテジ
【符号の説明】
Ｍａｒｋ Ｌｅｎｇｔｈ マーク長
Ｔ 基準クロック
ＲＦ Ｌｅｂｅｌ（Ｖ） ＲＦ（再生信号）レベル（ボルト）
Ｍｏｄｕｌａｔｅｄ ａｍｐｌｉｔｕｄｅ 変調度
Ｕｎｒｅｃ 未記録時の再生信号（ＲＦ）レベル
Ｔｏｐ マーク列を記録した時の最大再生信号レベル（即ちスペース部）
Ｂｏｔｔｏｍ マーク列を記録した時の最小再生信号レベル（即ちマーク部）
ＭＡ． （Ｔｏｐ−Ｂｏｔｔｏｍ）／Ｔｏｐで計算される変調度
Ｔｉｍｅ０．５（μｓ／ｄｉｖ） 時間（１メモリ０．５マイクロ秒）
Ａ 基準点から隣接するランド又はグルーブの近い方の端部までの幅
Ｂ 基準点から隣接するランド又はグルーブの遠い方の端部までの幅
Ｃ 基準点から次のグルーブ又はランドの近い方の端部までの幅
Ｄ 基準点から次のグルーブ又はランドの遠い方の端部までの幅
ζ グルーブ底部からランド上面までの高さ
Ｐｉｔ レーザ光の入射方向とは逆に変形した記録マーク
Ｂｕｍｐ レーザ光の入射方向に変形した記録マーク
Ｓｕｍ 和信号（再生信号）
Ｂｅａｍ Ｐｏｓｉｔｉｏｎ（μｍ） ビーム位置（マーク中心からのビーム中心のズレ量）
Ｆｒｏｍ Ｓｕｂ，Ｌａｎｄ 基板側からランド記録
Ｆｒｏｍ Ｓｕｂ，Ｇｒｏｏｖｅ 基板側からグルーブ記録
Ｎｏ Ｂｕｂｂｌｅ 空隙無し
Ｂｕｂｂｌｅ 空隙有り
（Ｎ） 変形領域の幅が０．８５２５λの場合
（Ｗ） 変形領域の幅が１．８５２５λの場合
σ／Ｔｗ ジッタ
Ｐｗ１ 記録パワー
Ｐｗ２ ボトムパワー
Ｐｒ バイアスパワー
ＴＥＦＰ 基準時間から先頭パルス立下り時間までの時間
ＴＳＦＰ 基準時間から先頭パルス立上り時間までの時間
ＴＥＭＰ 基準時間からマルチパルス立下り時間までの時間
ＴＳＭＰ 基準時間からマルチパルス立上り時間までの時間
ＴＥＬＰ 基準時間から最終パルス立下り時間までの時間
ＴＳＬＰ 基準時間から最終パルス立上り時間までの時間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a write once read many (WORM) optical recording medium, and more particularly to a write once optical recording medium capable of high density recording even at a blue laser wavelength.
[0002]
[Prior art]
Development of blue lasers capable of ultra-high density recording is rapidly progressing, and write-once type optical recording media corresponding thereto are being developed.
In conventional write-once optical recording media, recording pits are formed by irradiating a recording layer made of an organic material with laser light and causing a change in refractive index mainly due to decomposition and alteration of the organic material. The optical constant and decomposition behavior of the organic material used are important factors for forming good recording pits.
Accordingly, it is necessary to select an organic material used for the recording layer that is suitable for optical properties and decomposition behavior with respect to the blue laser wavelength. In other words, the recording / reproducing wavelength has a large absorption band in order to increase the reflectivity when unrecorded, and to cause a large change in refractive index due to decomposition of the organic material by laser irradiation (this provides a large degree of modulation). It is selected so as to be located at the bottom of the long wavelength side.
This is because the skirt on the long wavelength side of the large absorption band of the organic material is a wavelength region having an appropriate absorption coefficient and a large refractive index.
However, an organic material having an optical property with respect to a blue laser wavelength that is the same as the conventional value has not yet been found. This is because in order to obtain an organic material having an absorption band near the blue laser wavelength, it is necessary to reduce the molecular skeleton or shorten the conjugated system, but this leads to a decrease in absorption coefficient, that is, a decrease in refractive index. Because.
That is, there are many organic materials having an absorption band near the blue laser wavelength, and the absorption coefficient can be controlled. However, since there is no large refractive index, a large degree of modulation cannot be obtained.
[0003]
For example, Patent Documents 1 to 5 describe organic materials for blue lasers.
However, these documents only measure the spectra of the solution and the thin film even when looking at the examples, and there is no description regarding recording and reproduction.
In Patent Documents 6 to 8, although there is a description of recording in the examples, the recording wavelength is 488 nm, and there is no description regarding recording conditions and recording density, and only a description that good recording pits can be formed. It is.
Although Patent Document 9 has a description of recording in the examples, the recording wavelength is 430 nm, and there is no description regarding recording conditions and recording density, but only a description that a good degree of modulation has been obtained. .
In Patent Documents 10 to 19, there is an example of recording at a recording wavelength of 430 nm and NA of 0.65 in the examples, but the low recording density condition (recording density equivalent to DVD) is that the shortest pit is 0.4 μm.
In Patent Document 20, there is recording at a recording / reproducing wavelength of 405 to 408 nm, but there is no specific description regarding the recording density, which is a low recording density condition of recording a 14T-EFM signal.
[0004]
Further, the following technologies are disclosed regarding the layer configuration and recording method different from those of conventional CD and DVD optical recording media.
Patent Document 21 discloses a technique for recording by changing the extinction coefficient (absorption coefficient in the present invention) of a saturable absorbing dye in a layer structure of substrate / saturable absorbing dye-containing layer / reflective layer. .
Patent Document 22 discloses a technique for recording by changing the color or deformation of a metal vapor deposition layer by heat generated by the light absorption layer in a layer configuration of substrate / metal vapor deposition layer / light absorption layer / protective sheet. Yes.
Patent Document 23 discloses a technique for recording by changing the depth of the groove portion by changing the film thickness of the recording layer in a layer configuration of substrate / dielectric layer / recording layer including a light absorber / reflective layer. ing.
Patent Document 24 discloses a technique for performing recording by changing the film thickness of the recording layer by 10 to 30% in a layer configuration of substrate / recording layer including light absorber / metal reflective layer.
[0005]
Patent Document 25 discloses a technique for recording by increasing the groove width of a substrate by 20 to 40% with respect to an unrecorded portion in a layer configuration of substrate / recording layer containing organic dye / metal reflective layer / protective layer. Is disclosed.
Patent Document 26 discloses a technique for recording by forming a bubble by deforming a metal thin film with a layer structure of substrate / intermediate layer / metal thin film.
In Patent Document 27, the recording auxiliary layer is deformed into a concave shape in a layer configuration of substrate / light absorption layer / recording auxiliary layer / light reflecting layer, and the light reflecting layer is deformed into a concave shape along with the deformation of the recording auxiliary layer. Thus, a technique for recording is disclosed.
In Patent Document 28, a recording auxiliary layer having a layer structure of substrate / light absorbing layer / porous recording auxiliary layer / light reflecting layer or substrate / porous recording auxiliary layer / light absorbing layer / light reflecting layer is provided. A technique is disclosed in which recording is performed by deforming into a concave shape and deforming the light reflecting layer into a concave shape along with the deformation of the recording auxiliary layer.
In Patent Document 29, the light absorption layer is deformed into a concave shape in a layer configuration of substrate / porous light absorption layer / light reflection layer, and the light reflection layer is deformed into a concave shape along with the deformation of the light absorption layer. A technique for recording with the above is disclosed.
[0006]
In Patent Document 30, recording is performed by shifting the absorption spectrum of an organic dye to the short wavelength side in a layer structure of a substrate / recording layer containing an organic dye / recording auxiliary layer, in which the recording auxiliary layer and the organic dye are compatible. Techniques for performing are disclosed.
Patent Document 31 discloses a technique in which recording is performed by forming bumps on a substrate and the composite functional layer in a layer configuration in which a composite functional layer having a function of a reflective layer and a recording layer and a protective layer are sequentially formed on the substrate. Has been. Note that the composite functional layer is prescribed to use a metal such as nickel, chromium, titanium, or an alloy thereof.
In Patent Document 32, a metal thin film layer, a deformable buffer layer, a reflective layer, and a protective layer are sequentially formed on a substrate, and the substrate and the metal thin film layer are deformed at the same time. A technique for recording by reducing the thickness is disclosed. Note that the metal thin film layer has a rule that a metal such as nickel, chromium, titanium, or an alloy thereof is used. In addition, as the buffer layer, there is a description that a resin that is easily deformable and has an appropriate fluidity is used, and a pigment may be contained in order to promote deformation.
[0007]
In Patent Document 33, a metal thin film layer, a buffer layer, and a reflective layer are sequentially laminated on a substrate, and the substrate and the metal thin film layer are deformed. At the same time, the buffer layer thickness and the optical constant at the deformed portion are set. A technique for recording by changing is disclosed. In addition, as a metal thin film layer, there exists a description that metals, such as nickel, chromium, titanium, or those alloys are preferable. The buffer layer is made of a mixture of a dye and an organic polymer, and a dye having a large absorption band near the recording / reproducing wavelength is used.
In Patent Document 34, a metal recording layer, a buffer layer, and a reflective layer are sequentially laminated on a substrate, and the substrate and the metal recording layer are deformed. At the same time, the buffer layer thickness and the optical constant at the deformed portion are set. A technique for recording by changing is disclosed. In addition, as a metal recording layer, there exists a description that metals, such as nickel, chromium, titanium, or those alloys are preferable. The buffer layer is made of a mixture of a dye and a resin, and a dye having a large absorption band near the recording / reproducing wavelength is used.
[0008]
As described above, the above-described various conventional techniques are not aimed at realizing a write-once type optical recording medium in the blue laser wavelength region, and are not a layer configuration or a recording method effective in the blue laser wavelength region. In particular, in the vicinity of 405 nm, which is the center of the oscillation wavelength of a blue semiconductor laser that is currently in practical use, most organic materials have an optical constant comparable to that required for the recording layer of conventional write-once type optical recording media. It does n’t exist.
In addition, there are no examples in which recording conditions are clarified near 405 nm and recording is performed at a higher recording density than DVD.
Further, many of the above-described prior art examples are experiments with a conventional disk configuration (see FIG. 1), and a configuration different from the conventional disk configuration has been proposed. The same optical characteristics and functions as before are required, and there is no effective proposal for a layer structure, a recording principle, and a recording method that can easily realize a write-once type optical recording medium made of an organic material in the blue laser wavelength region.
[0009]
In addition, in a write-once type optical recording medium using a conventional organic material, a large refractive index and a relatively small absorption coefficient (about 0.05 to 0.07) with respect to the recording / reproducing wavelength from the viewpoint of securing the degree of modulation and the reflectance. ) Can only be used.
That is, since the organic material does not have sufficient absorption capability for the recording light, it is impossible to reduce the film thickness of the organic material, and thus it is necessary to use a substrate having a deep groove. (Organic materials are usually formed by spin coating, so organic materials were buried in deep grooves to increase the thickness). Therefore, it becomes very difficult to form a substrate having a deep groove, which has been a factor of deteriorating the quality as a write once optical recording medium. Furthermore, in a write-once optical recording medium using a conventional organic material, the main absorption band of the organic material exists in the vicinity of the recording / reproducing wavelength, so the wavelength dependence of the optical constant of the organic material increases (the optical constant depends on the wavelength). Recording characteristics such as recording sensitivity, modulation factor, jitter, error rate, and reflectivity greatly change with respect to fluctuations in recording / reproducing wavelength due to individual differences of lasers, environmental temperature changes, etc. was there.
[0010]
In order to solve the above-described problems, the present inventor, for example, in Japanese Patent Application No. 2002-144415 (hereinafter referred to as a prior application), has been proposed a light absorption function conventionally required for a recording layer made of an organic compound. Considering the separation of the two functions of the recording function, the write-once type optical recording medium structure in which the light absorbing function is removed from the recording layer made of an organic compound, and a light absorbing layer is newly introduced as a layer responsible for the light absorbing function. Proposed.
In this write-once type optical recording medium structure, the light absorption function is removed from the organic compound, and the deformation of the light absorption layer can be used for recording. Therefore, the restrictions on the organic compound can be greatly relaxed, and the CD-R And the dye used in DVD-R and the like can be used.
In one configuration example of the above-mentioned write-once type optical recording medium proposed by the present inventor, that is, a light absorption layer having a light absorption function for recording light is provided on the substrate or adjacent to the cover layer. In a write once optical recording medium having a structure, for example, a light absorbing layer is deformed by recording, or a light absorbing function of the light absorbing layer is used to physically apply a layer adjacent to the light absorbing layer on the side opposite to the substrate or the cover layer. Recording is performed by applying a chemical or optical change.
However, this write-once type optical recording medium can obtain good jitter characteristics (recording / reproducing characteristics) when recording at low recording power, but the jitter may suddenly deteriorate when recording at high recording power. Yes, leading to a narrow power margin for jitter. In addition, although there is a similar tendency in any type of optical recording medium, there may be a phenomenon that tracking is easily lost in a portion recorded with a high recording power.
[0011]
[Patent Document 1]
JP 2001-181524 A
[Patent Document 2]
JP 2001-158865 A
[Patent Document 3]
JP 2000-343824 A
[Patent Document 4]
JP 2000-343825 A
[Patent Document 5]
JP 2000-335110 A
[Patent Document 6]
Japanese Patent Application Laid-Open No. 11-221964
[Patent Document 7]
Japanese Patent Laid-Open No. 11-334206
[Patent Document 8]
JP 2000-43423 A
[Patent Document 9]
JP-A-11-58955
[Patent Document 10]
JP 2001-39034 A
[Patent Document 11]
JP 2000-149320 A
[Patent Document 12]
JP 2000-113504 A
[Patent Document 13]
JP 2000-108513 A
[Patent Document 14]
JP 2000-222772 A
[Patent Document 15]
JP 2000-218940 A
[Patent Document 16]
JP 2000-222771 A
[Patent Document 17]
JP 2000-158818 A
[Patent Document 18]
JP 2000-280621 A
[Patent Document 19]
JP 2000-280620 A
[Patent Document 20]
Japanese Patent Laid-Open No. 2001-146074
[Patent Document 21]
JP-A-7-304258
[Patent Document 22]
JP-A-8-83439
[Patent Document 23]
JP-A-8-138245
[Patent Document 24]
JP-A-8-297838
[Patent Document 25]
JP-A-9-198714
[Patent Document 26]
Japanese Patent No. 2506374
[Patent Document 27]
Japanese Patent No. 2591939
[Patent Document 28]
Japanese Patent No. 2591940
[Patent Document 29]
Japanese Patent No. 2591941
[Patent Document 30]
Japanese Patent No. 2998925
[Patent Document 31]
JP-A-9-265660
[Patent Document 32]
Japanese Patent Laid-Open No. 10-134415
[Patent Document 33]
Japanese Patent Application Laid-Open No. 11-306591
[Patent Document 34]
JP-A-10-124926
[0012]
[Problems to be solved by the invention]
The present invention relates to a write-once type optical recording medium having a structure in which a light absorbing layer having a light absorbing function for recording light is provided adjacent to a substrate or a cover layer by further developing the above-mentioned prior invention. The purpose is to realize the following (1) to (3).
(1) Providing a write-once optical recording medium that eliminates the cause of deteriorating recording / reproducing characteristics and tracking performance.
(2) Providing a layer structure that suppresses deterioration of recording / reproduction characteristics and tracking performance.
(3) Providing a recording method that suppresses deterioration of recording / reproduction characteristics and tracking performance.
[0013]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that a write-once optical recording medium having a structure in which a light absorption layer having a light absorption function with respect to recording light is provided on a substrate or adjacent to a cover layer, Since the light absorption layer having a large absorption coefficient is in contact with the substrate or the cover layer, when the recording power is increased, the light absorption layer is deformed or adjacent to the light absorption layer opposite to the substrate or the cover layer. It has been found that in addition to changes in the physical, chemical, optical, etc. of the layer, voids may occur in the substrate or in the cover layer.
Although the gap in the substrate or cover layer has the effect of generating a large degree of modulation, the recording polarity can be changed or the reproduction signal waveform can be differentiated within the settable recording power range of the laser. It has been found that there is a case where the recording / reproducing characteristics are deteriorated by making the waveform or imbalance of the modulation degree of the short mark and the long mark. In particular, it has been found that when the recording polarity changes in the settable recording power range of the laser (when the recording polarity is mixed), the jitter and the power margin of the jitter are deteriorated and the modulation degree is decreased.
Therefore, the present invention provides a write-once type optical recording medium, a layer structure, and a recording method that suppress the generation of voids in a substrate or a cover layer, which often deteriorates recording / reproducing characteristics and tracking performance.
In general, in mark length recording, a reproduction signal (RF signal) when a recording mark is reproduced is as shown in FIG. On the other hand, as shown in FIGS. 2B and 2C, a signal having an inflection point near the front and rear edges of the recording mark and near the center of the recording mark is converted into a differential waveform (differential waveform) in the present invention. To tell.
[0014]
  That is, the above-described problems are solved by the following inventions 1) to 9).
  1) Substrate or cover layerAnd a light absorption layer made of an inorganic material having a light absorption function for recording light,Gap suppression layer for suppressing generation of voids in the substrate or cover layer due to recordingButA write-once type optical recording medium having a provided structure.
  2) On the substrate, a void suppressing layer for suppressing void generation in the substrate due to recording, and a light absorption function for recording lightMade of inorganic materialA write-once optical recording medium having a structure in which a light absorbing layer, a recording layer made of an organic compound, and a reflective layer are sequentially provided.
  3)SaidThe void suppression layer is made of SiO.₂ZnS-SiO₂, ZrO₂The main component is any of1) or 2)The write-once type optical recording medium as described.
  4)SaidThe void suppression layer is made of ZnS, ZrO.₂, Y₂O₃And SiO₂It is characterized by being an oxide consisting of1) or 2)The write-once type optical recording medium as described.
  5)SaidThe void suppressing layer is made of ZrO.₂TiO₂, SiO₂And X, where X is Al₂O₃, MgO, CaO, NbO, Y₂O₃, At least one selected from CeO1) or 2)The write-once type optical recording medium as described.
  6)The write-once type optical recording medium as described in any one of 1) to 5), which is compatible with a recording / reproducing wavelength of 405 nm.
  7)The write-once type optical recording medium according to any one of 1) to 6), wherein the recording polarity after recording is Low to High.
  8) Write-once type optical recording, wherein the write-once type optical recording medium according to any one of 1) to 7) is recorded in a recording power range in which no gap is formed in the substrate or the cover layer. Media recording method.
  9) A write-once optical recording medium according to any one of 1) to 7), wherein recording is performed with a recording strategy in which no gap is formed in a substrate or a cover layer. Recording method.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
In a write once optical recording medium having a structure in which a light absorption layer having a light absorption function for recording light is provided adjacent to the substrate or the cover layer, when the recording power is increased, the light absorption layer Deformation and changes in physical, chemical, optical, etc. of the layer adjacent to the light absorption layer on the side opposite to the substrate or cover layer occur.
For example, in a specific example, in a write-once type optical recording medium having a structure of substrate / light absorption layer / dye layer / reflection layer, the following a) to h) are performed depending on the light absorption function of the light absorption layer. A change occurs and a recording part is formed.
B) The light absorption layer is deformed
B) The complex refractive index of the light absorption layer changes.
C) The volume of the light absorption layer changes.
D) Low refractive index parts such as voids are generated in the light absorption layer.
E) Change in complex refractive index of the dye layer changes
F) The volume of the dye layer changes
G) Low refractive index parts such as voids are generated in the dye layer.
H) The substrate is deformed
[0016]
Since this write-once optical recording medium does not require a light absorption function in the dye layer as in the prior art, the degree of freedom in dye selection is greatly increased, and a write-once optical recording medium corresponding to a laser wavelength equal to or less than the blue laser wavelength is easy. There is an advantage that can be provided.
However, when the light absorption layer is difficult to deform, when the optical change of the light absorption layer is difficult to occur, or when the optical change of the dye layer is difficult to occur, the light absorption layer or the dye layer is used for recording. It is necessary to increase the recording power until an optical, chemical, or physical change occurs. At this time, in a structure in which the substrate, the cover layer, etc. are in contact with the light absorption layer, the substrate is heated more than necessary. In addition, voids may be generated in the substrate due to the heating more than necessary.
That is, when the recording power is low, the light absorption function of the light absorption layer causes an optical, chemical, or physical change in the light absorption layer or the dye layer, thereby forming a recording portion. In addition to the optical, chemical, or physical change of the light absorption layer or the dye layer, the substrate is heated more than necessary, so that the recording portion is also formed by the generation of voids in the substrate.
[0017]
The generation of voids in the substrate is generally because the generated recording power range is greatly different from the recording power range causing optical, chemical, or physical changes in the light absorption layer or the dye layer (inside the substrate). The air gap is generally generated with a recording power higher than the change of the light absorption layer and the dye layer), and causes a deterioration of jitter and a recording power margin of jitter.
In addition, since voids in the substrate generally occur with a threshold value, it often causes a sudden change in modulation degree or a change in recording polarity, which causes jitter deterioration or jitter recording power. Induces margin deterioration.
In addition, the generation of the voids in the substrate may cause the deformation of the light absorption layer to become very large, disturb the deformation shape of the light absorption layer, or greatly change the groove shape of the substrate itself. Increases or tracking performance deteriorates.
Therefore, the present invention suppresses the generation of voids in the substrate or the cover layer, which is highly likely to deteriorate the tracking performance, change in recording polarity, jitter, or reduce the recording power margin of jitter.
[0018]
As described above, the gap in the substrate or the cover layer is likely to occur when the recording power is increased or in the long mark.
Therefore, there is a phenomenon in which the jitter suddenly deteriorates on the high recording power side (the recording power margin of jitter suddenly deteriorates), the recording polarity changes depending on the recording mark length, or the amplitude changes greatly depending on the recording mark length. To do.
Due to the phenomenon that the recording polarity changes depending on the recording mark length or the amplitude changes greatly depending on the recording mark length, good recording / reproducing characteristics can be obtained with a single-period recording mark, but recording / reproducing can be performed when a random pattern is recorded. The characteristics may be deteriorated.
Examples of a method for suppressing the generation of voids in the substrate or the cover layer include the following a) to e).
B) A heat insulating layer (void suppressing layer) is provided between the substrate or cover layer and the light absorbing layer.
B) A heat dissipation layer (void suppression layer) is provided between the substrate or cover layer and the light absorption layer.
C) Control recording power (recording is performed in a recording power range in which no gap is generated).
D) Control and optimize the recording strategy (make sure the long mark does not store more heat than necessary).
E) Control the decomposition characteristics of the substrate (select a material that does not generate voids).
[0019]
When a void suppressing layer is provided between the substrate or the cover layer and the light absorbing layer, whether the void suppressing layer is a so-called heat insulating layer or a heat radiating layer depends on the size of the light absorbing function of the light absorbing layer and the light absorbing layer. Depends on thermal properties such as thermal conductivity.
That is, when the light absorption function of the light absorption layer is relatively low, the heat generated in the light absorption layer is released by the heat dissipation layer so that the recording sensitivity is not impaired (for recording with low recording power). It is more advantageous to suppress the generation of voids in the substrate by limiting the amount of heat transmitted to the substrate by the heat insulating layer, rather than suppressing the generation of.
On the contrary, when the light absorption function of the light absorption layer is relatively high, it is also effective to suppress the generation of voids in the substrate by releasing the heat generated in the light absorption layer through the heat dissipation layer.
Controlling the recording power is to control the amount of heat generated in the light absorption layer, so that the generation of voids in the substrate can be directly controlled.
Controlling the recording strategy is also controlling the amount of heat generated in the light absorption layer as well as the recording power, so that the generation of voids in the substrate can be directly controlled. Further, when controlling the recording strategy, the amount of heat generated in the light absorption layer can be controlled for each recording mark length, so that it is possible to suppress the phenomenon that the presence or absence of voids in the substrate differs depending on the recording mark length.
Controlling the decomposition characteristics of the substrate means, for example, increasing the decomposition temperature of the substrate material, and in the case of a polymer material, using a high-decomposition polymer material or increasing the molecular weight (increasing the degree of polymerization) Therefore, the generation of voids can be suppressed. It is also effective to use a glass material for the substrate.
[0020]
The write-once type optical recording medium and the recording method thereof according to the present invention include, for example, the write-once type optical recording medium having the following structures (i) and (ii), or a write-once type optical recording having a two-layer structure in which two of them are bonded. Valid for media.
(I) Write-once type optical recording medium for recording / reproducing from the substrate side
・ Substrate / light absorption layer
・ Substrate / light absorption layer / recording layer
・ Substrate / light absorption layer / undercoat layer / recording layer
・ Substrate / light absorption layer / recording layer / overcoat layer
・ Substrate / light absorption layer / recording layer / reflection layer
・ Substrate / light absorption layer / undercoat layer / recording layer / reflection layer
Substrate / light absorption layer / recording layer / overcoat layer / reflective layer
・ Substrate / light absorption layer / recording layer / reflection layer / protective layer
(Ii) Write-once optical recording medium for recording / reproduction from the cover layer side
・ Substrate / light absorption layer / cover layer
・ Substrate / light absorption layer / recording layer / cover layer
・ Substrate / light absorption layer / recording layer / undercoat layer / cover layer
・ Substrate / light absorption layer / overcoat layer / recording layer / cover layer
・ Substrate / reflection layer / recording layer / light absorption layer / cover layer
Substrate / reflection layer / recording layer / light absorption layer / undercoat layer / cover layer
Substrate / reflection layer / overcoat layer / recording layer / light absorption layer / cover layer
As a preferred embodiment, in the write-once type optical recording medium having the above structure, a void suppressing layer is provided between the substrate and the light absorbing layer or between the cover layer and the light absorbing layer.
[0021]
As shown in the above configuration example, the write-once type optical recording medium of the present invention basically comprises a substrate or a cover layer and a light absorption layer as essential components, but is provided with a void suppressing layer. Preferably, a recording layer such as an organic compound, an undercoat layer, an overcoat layer, a metal reflective layer, a protective layer, and the like may be provided on the substrate as necessary.
In the present invention, the recording layer refers to a layer that causes an optical constant change, a chemical change, or a physical change. Specifically, it is a layer that causes changes in complex refractive index, phase difference, decomposition, sublimation, aggregation, etc., crystal state change, solubility change, structural change, volume change, void formation, etc. by recording. .
Similarly, the undercoat layer and the overcoat layer are formed as an interference layer for improving recording / reproduction characteristics, a protective layer during film formation (for example, a film is formed on a film soluble in a coating solvent by a spin coating method). Protective layer), a protective layer that maintains the film state of the adjacent layer, etc. (improves storage stability, etc.).
[0022]
The material of the substrate in the write-once type optical recording medium of the present invention may basically be transparent at the wavelengths of recording light and reproducing light.
Examples of such materials include acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and other resins, glass, and glass. Those having a resin layer made of a radiation curable resin such as a photocurable resin can be used, but injection molded polycarbonate is preferable in terms of high productivity, cost, moisture absorption resistance, and the like. From the viewpoints of chemical resistance and moisture absorption resistance, amorphous polyolefin is preferable, and from the viewpoint of high-speed response or no generation of voids, a glass substrate is preferable.
Further, a resin substrate or a resin layer may be provided in contact with the recording layer, and guide grooves and pits for recording / reproducing light may be provided on the resin substrate or resin layer.
[0023]
Examples of the recording layer material include organic materials, and dyes are also preferable.
Examples of the dye include metal-containing azo dyes, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes, metal-containing indoaniline dyes, triarylmethane dyes, merocyanine dyes, and azurenium dyes. Naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes, pyrylium dyes, and the like.
In addition, the recording layer has a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone) as a singlet oxygen quencher to improve the stability and light resistance of the recording layer. And a recording sensitivity improver such as a metal compound may be contained for improving the recording sensitivity.
Here, the metal compound means a compound in which a metal such as a transition metal is contained in the compound in the form of atoms, ions, clusters, etc., for example, ethylenediamine complex, azomethine complex, phenylhydroxyamine complex, phenanthroline complex, Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex and porphyrin complex can be mentioned. Although it does not specifically limit as a metal atom, A transition metal is preferable.
[0024]
Moreover, the pigment | dye of another system | strain can also be used together as needed.
Furthermore, a binder, a leveling agent, an antifoaming agent, etc. can also be used together as needed.
Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.
The film thickness of the recording layer varies depending on the recording method and the like, and is not particularly limited, but is usually 50 to 300 nm.
[0025]
Examples of the method for forming the recording layer include generally used thin film forming methods such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spin coating method, and an immersion method.
Among them, the spin coating method is preferable from the viewpoint of mass productivity and cost, and the vacuum evaporation method is more preferable than the coating method from the viewpoint that a recording layer having a uniform thickness can be obtained.
In the case of film formation by a spin coating method, the number of rotations is preferably 500 to 15000 rpm, and after spin coating, treatment such as heating or solvent vapor may be performed in some cases.
The coating solvent for forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method, or a dipping method may be any solvent that does not attack the substrate and is not particularly limited.
[0026]
For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; perfluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Examples of the solvent include hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl isobutyrate.
As the recording layer material, in addition to the above, a polymer material, a phase change material, a photochromic material, a thermochromic material, and the like can be preferably used.
[0027]
As a material for the light absorption layer, it is preferable to use a material having a certain absorption coefficient with respect to the recording wavelength in terms of ensuring sufficient recording sensitivity.₄Carbon-based non-oxides such as C, TiC, WC, carbon-based non-oxides such as amorphous carbon, graphite, diamond, ceramics typified by ferrite, or Te-TeO₂, Te-TeO₂-Pd, Sb₂Se₃/ Bi₂Te₃, Ge-Te-Sb-S, Te-TeO₂-Ge-Sn, Te-Ge-Sn-Au, Ge-Te-Sn, Sn-Se-Te, Sb-Se-Te, Sb-Se, Ga-Se-Te, Ga-Se-Te-Ge, In -Se, In-Se-Tl-Co, Ge-Sb-Te, In-Se-Te, Ag-In-Sb-Te, Ag-Zn, Cu-Al-Ni, In-Sb, In-Sb-Se Phase change recording materials such as In-Sb-Te, pure metals such as nickel, chromium, titanium and tantalum, alloys such as copper / aluminum and nickel / iron, semimetals such as silicon, semiconductors such as Ge, etc. It is possible.
Among them, it is preferable to use a material containing Si or Ge. For example, Si, Ge, SiC, or the like is preferable.
The film thickness of the light absorption layer is usually 5 to 150 nm.
[0028]
As a material of the void suppression layer, for example, Al₂O₃, MgO, BeO, ZrO₂TiO₂, UO₂, ThO₂, CaO, NbO, Y₂O₃, Simple oxides such as CeO; SiO₂2MgO · SiO₂, MgO / SiO₂, CaO · SiO₃, ZrO₂・ SiO₂3Al₂O₃・ 2SiO₂2MgO · 2Al₂O₃・ 5SiO₂, Li₂O ・ Al₂O₃・ 4SiO₂Silicate oxides such as Al₂TiO₅, MgAl₂O₄, Ca₁₀(PO₄)₆(OH)₂, BaTiO₃LiNbO₃, PZT [Pb (Zr, Ti) O₃], PLZT [(Pb, La) (Zr, Ti) O₃], Double oxide oxides such as ferrite; or Si₃N₄, Si_6-ZAl_ZO_ZN_8-ZNon-oxides of nitrides such as AlN, BN, TiN; SiC, B₄Non-oxides of carbides such as C, TiC and WC; LaB₆TiB₂, ZrB₂Non-oxides of borides such as ZnS, CdS, MoS₂Sulfide non-oxide such as MoSi₂Silicide-based non-oxides such as amorphous carbon, graphite, diamond and other carbon-based non-oxides, or mixtures thereof can be used.
From the viewpoint of transparency to recording / reproducing light and productivity, SiO₂Material mainly composed of ZnS or SiO₂A material mainly composed of (main component) is preferred.
In order to obtain a sufficient heat insulation effect, ZrO₂It is also preferable to use as a main component (main component).
ZnS, ZrO₂, Y₂O₃And SiO₂An oxide comprising ZrO₂TiO₂, SiO₂And X, where X is Al₂O₃, MgO, CaO, NbO, Y₂O₃A material that is at least one selected from CeO is preferable.
[0029]
A reflective layer may be formed on the recording layer directly or via an overcoat layer, and the thickness thereof is preferably 50 to 300 nm.
As a material of the reflective layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal selected from Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Cr, and Pd alone or It can be used as an alloy. Among them, Au, Al, and Ag have high reflectivity and are suitable as a material for the reflective layer.
Further, the main component is the above material, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, A material containing a metal and a semimetal such as Te, Pb, Po, Sn, and Bi may be used.
Among these, those containing Ag as a main component are particularly preferable because of low cost and high reflectivity.
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.
Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.
[0030]
In addition, a known inorganic or organic overcoat layer, undercoat layer, or adhesive layer may be provided on the substrate or under the reflective layer in order to improve reflectivity, improve recording characteristics, or improve adhesion. It can also be provided.
In the case of imparting a light absorption function to the overcoat layer or the undercoat layer, a material similar to the above-described light absorption layer material can be used. In addition, when using an overcoat layer or undercoat layer as a mechanical protection, improved storage stability, improved solvent resistance, or interference layer, use the same material as the above-mentioned void suppressing layer material. Can do.
The material of the protective layer formed on the reflective layer is not particularly limited as long as it protects the reflective layer from external force. Examples of the organic material include thermoplastic resins, thermosetting resins, electron beam curable resins, Examples thereof include UV curable resins. In addition, as an inorganic material, SiO₂, SiN₄, MgF₂, SnO₂Etc.
A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying.
The UV curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiating with UV light. As the UV curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used.
[0031]
These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.
As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 to 100 μm, but is preferably 3 to 30 μm in the present invention.
Further, a substrate may be further bonded to the reflective layer surface, or two write-once optical recording media may be bonded with the reflective layer surfaces facing each other as the inner surface.
An ultraviolet curable resin layer, an inorganic thin film, or the like may be formed on the mirror surface side of the substrate in order to protect the surface and prevent adhesion of dust and the like.
[0032]
The cover layer is necessary when using a lens with a high NA in order to increase the density.
For example, when the NA is increased, it is necessary to reduce the thickness of the portion through which the reproduction light is transmitted. This is due to the angle at which the disk surface deviates from the optical axis of the optical pickup as the NA increases (so-called tilt angle, proportional to the square of the product of the reciprocal of the wavelength of the light source and the numerical aperture of the objective lens). This is because the allowable amount of generated aberration is reduced, and this tilt angle is easily affected by the aberration due to the thickness of the substrate.
Therefore, the thickness of the substrate is reduced to minimize the influence of aberration on the tilt angle.
Therefore, for example, a recording layer is formed by forming irregularities on a substrate, a reflective film is provided on the recording layer, and a light-transmitting cover layer, which is a thin film that transmits light, is provided on the recording layer. A write-once optical recording medium that reproduces information on the recording layer by irradiating the recording layer, a reflective film on the substrate, and a recording film is formed thereon to form a recording layer, which further has optical transparency A write-once optical recording medium has been proposed in which a cover layer is provided and information on the recording layer is reproduced by irradiating the reproducing light from the cover layer side.
[0033]
In this way, the NA of the objective lens can be increased by reducing the thickness of the cover layer. That is, it is possible to further increase the recording density by providing a thin cover layer and recording / reproducing from the cover layer side.
Such a cover layer is generally formed of a polycarbonate sheet or an ultraviolet curable resin.
Further, the cover layer referred to in the present invention may include a layer for adhering the cover layer.
The wavelength of the laser beam used in the write-once type optical recording medium of the present invention is preferably as short as possible for high-density recording, but is particularly preferably in the range of 350 to 530 nm. A typical example of such a laser beam is a laser beam having a center wavelength of 405 nm.
[0034]
【Example】
EXAMPLES Hereinafter, although an Example and a reference example demonstrate this invention further more concretely, this invention is not limited at all by these Examples.
[0035]
Reference example 1
First, a write-once type optical recording medium having SiC having a thickness of 10 nm as a light absorption layer was formed on a substrate, and recording / reproducing characteristics from the substrate side were evaluated.
3 to 6 show the recording results of Reference Examples 1-A to 1-D.
FIGS. 3A to 6A are diagrams showing measurement results of the recording mark length (Mark Length) dependence of the reproduction signals (RF levels) of Reference Examples 1-A to 1-D. Among them, Unrec is a reproduction signal (RF level) when recording is not performed, Top is a maximum reproduction signal level (generally a space portion) when a mark string is recorded, and Bottom is a minimum when a mark string is recorded. The reproduction signal level, MA, indicates the modulation degree calculated by (Top-Bottom) / Top.
FIGS. 3B to 6B show a reproduction signal when 3T marks are continuously recorded, a reproduction signal when 4T marks are continuously recorded, and a reproduction signal when no recording is performed. 3 (c) to FIG. 6 (c), the reproduction signal when the 6T mark is continuously recorded, the reproduction signal when the 8T mark is continuously recorded, and the reproduction when not recorded are shown in FIG. 3 (d) to 6 (d) show signal levels when a 3T mark is continuously recorded, a playback signal when a 14T mark is continuously recorded, and an unrecorded signal. The reproduction signal level is shown.
[0036]
<Reference Example 1-A>
A write-once type optical recording medium was produced in which a SiC layer having a thickness of 10 nm was provided as a deformable layer having a light absorption function on a polycarbonate substrate having a guide groove with a groove depth of 55 nm.
This optical recording medium was irradiated with 5.0 mW of laser light from the substrate side using an optical disk evaluation apparatus, DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. 3T to 14T marks were individually recorded at a recording frequency of 65.4 MHz and a recording linear velocity of 6.0 m / s at the groove position on the near side as viewed from the incident laser beam side.
Note that it was confirmed by AFM (atomic force microscope) that the SiC layer was deformed to the side opposite to the incident light (on the side opposite to the substrate).
Further, from the result of FIG. 3A, it can be confirmed that there is a possibility that High to Low recording can be performed regardless of the recording mark length.
Furthermore, it can be seen from the results of FIGS. 3B to 3D that all of 3T, 4T, 6T, 8T, and 14T show reproduced signal waveforms that allow mark length recording.
[0037]
<Reference Example 1-B>
Except that the recording power was changed to 6.0 mW, the same experiment as Reference Example 1-A was performed.
It was confirmed by AFM that the SiC layer was deformed to the side opposite to the incident light (on the side opposite to the substrate).
Further, from the result of FIG. 4A, the recording polarity changes depending on the recording mark length, that is, the high mark is high to low recording in the short mark, but the high to low recording and the low to high recording are mixed in the long mark. It can be seen that such a signal is generated and it becomes difficult to record the mark length.
Further, from the results shown in FIGS. 4B to 4D, 3T and 4T show reproduction signal waveforms that can be recorded in the mark length, but 6T, 8T, and 14T have greatly increased the RF level at the center of the mark. Reproduction signal waveform is shown [In 6T and 8T, the period of the reproduction signal appears to be double that of the original reproduction signal. This is well understood when compared with FIG. 3 (c)], and it is found that mark length recording becomes difficult.
[0038]
<Reference Example 1-C>
Except that the laser beam of 6.0 mW was irradiated from the substrate side and recorded in the land portion (groove position on the back side when viewed from the incident laser beam side), the same experiment as Reference Example 1-A was performed. .
It was confirmed by AFM that the SiC layer was deformed to the side opposite to the incident light (on the side opposite to the substrate).
Further, from the result of FIG. 5A, the recording polarity tends to change depending on the length of the recording mark, that is, slightly, that is, the high mark is high to low and the low mark is high to low and low to. It can be seen that there is a tendency to generate a signal in which high recording is mixed, and mark length recording may be difficult.
Further, from the results shown in FIGS. 5B to 5D, 3T, 4T, 6T, and 8T indicate reproduction signal waveforms that can be recorded in the mark length, but 14T has a large increase in the RF level at the center of the mark. It can be seen that it is difficult to record the mark length.
[0039]
<Reference Example 1-D>
Exactly the same experiment as Reference Example 1-A was performed, except that 7.0 mW laser light was irradiated from the substrate side and recorded in the land portion (groove position on the back side when viewed from the incident laser light side). .
It was confirmed by AFM that the SiC layer was deformed to the side opposite to the incident light (on the side opposite to the substrate).
Further, from the result of FIG. 6A, the recording polarity changes depending on the recording mark length, that is, the short mark is High to Low recording, but the long mark is a mixture of High to Low recording and Low to High recording. It can be seen that such a signal is generated and it becomes difficult to record the mark length.
Further, from the results shown in FIGS. 6B to 6D, 3T and 4T show reproduction signal waveforms that can be recorded in the mark length, but 6T, 8T, and 14T show a significant increase in the RF level at the center of the mark. [For example, at 6T, the period of the reproduced signal appears to be double that of the original reproduced signal. This is well understood when compared with FIG. 3 (c)], and it is found that mark length recording becomes difficult.
[0040]
As described above, from the results of Reference Examples 1-A to 1-D, the write-once type optical recording medium in which the SiC layer is provided on the substrate has a high to low polarity reproduction signal at low recording power. When the power is increased, so-called differential waveform occurs such that the central portion of the recording mark is raised, and it can be seen that the recording polarity looks as if it is Low to High when recording at a higher recording power. It was.
In addition, the degree of differential waveform formation differs depending on the recording mark length, and it has been confirmed that differentiation waveform formation is very likely to occur with long marks.
As described above, normally, the reflectance of the recording mark portion changes in one direction as the recording power increases. On the write-once optical recording medium used in Reference Example 1, the recording portion is reproduced. It can be easily understood that the recording / reproduction characteristics such as jitter deteriorate due to the change of the signal waveform.
[0041]
Reference example 2
Next, in Reference Example 1, simulation was performed under the following conditions in order to clarify the cause of the reproduction signal having a differential waveform.
A recording mark (assuming Pit, see FIG. 7) having a mark length of about 8T (2.0λ) is formed with a layer structure of substrate / SiC (thickness 10 nm).
i) Recording position (Land or Groove)
ii) When reproduction was performed by scanning with a laser beam from the substrate side while changing the presence or absence of a gap ([No Bubble] or [Bubble]), what kind of reproduction signal was obtained was calculated.
The groove shape of the substrate is (A, B, C, D, ζ) = (0.2, 1.0525, 1.2525, 1.8525, 0.1375), and (record mark length, record mark width) , Height) = (2.0λ, 0.8525λ, −0.3λ) (numbers are in units of wavelength λ). Forming, that is, deformation occurs in a direction away from the substrate side). The presence / absence of a gap refers to the state as shown in FIG. 8, the recording state as shown in FIG. 8A is defined as having no gap, and the recording state as shown in FIG.
FIG. 9 shows the result when the recording part with the Pit formed in the land part is reproduced from the substrate side, and FIG. 10 shows the result when the recording part with the Pit formed in the groove part is reproduced from the substrate side. FIG.
In the legend of FIG. 10, (N) indicates the case where the width of the deformation area is 0.8525λ, and (W) indicates the case where the width of the deformation area is 1.8525λ.
As a result (see FIGS. 9 to 10), it was proved that there is a possibility that differential waveform may occur when a gap is generated between the light absorption layer and the substrate or in the substrate.
[0042]
Reference example 3
The simulation of Reference Example 2 proves that the cause of the deterioration of the recording / reproducing characteristics may be a gap generated between the substrate and the light absorption layer or in the substrate.
Therefore, in this reference example, in order to clarify the location and mechanism where voids are actually generated, the substrate / SiC (thickness 15 nm) / Co metal complex of the compound represented by the formula 1 / Ag reflective layer (thickness 150 nm) A write-once optical recording medium called a protective layer was prepared, and recording was performed on the groove part under the following conditions.
<Recording conditions>
Recording linear density: 1T = 0.0917 μm
Record mark length: 6T and 14T
・ Recording power: 9.0mW
・ Recording strategy: Basic strategy
Top-Tmp = 1.20-0.60 (T)
[Chemical 1]

In this recording, 6T had a recording polarity of Low to High, and 14T had a recording polarity of High to Low.
When the recording mark was 14T, the signal amplitude (corresponding to the modulation degree) of the recording portion was about twice that of 6T.
[0043]
Next, the optical recording medium is cut in a track direction or a radial direction with an FIB (Focused Ion Beam = focused ion beam processing apparatus), and the recording unit is subjected to FE-SEM (field emission scanning electron microscope) or TEM (transmission electron microscope). ).
As a result, as shown in FIG. 11 (a view cut by FIB in the track direction and observed by FE-SEM), when the recording mark length is 6T, the recording portion is deformed to the substrate side of the SiC layer, and the dye layer It was confirmed that the recording part was formed by the state change.
On the other hand, when the recording mark length is 14T, the recording polarity is reversed as compared with the recording mark length of 6T, and the recording portion where the modulation degree has increased rapidly is formed in the substrate as shown in FIGS. It was confirmed that voids were generated (when the mark length was 6T, no voids were generated in the substrate). That is, it was confirmed that the cause of the deterioration of the recording / reproducing characteristics was a gap generated in the substrate.
12 is a photograph (photograph) cut in the radial direction by FIB and observed by TEM, and FIG. 13 is an enlarged view of (photograph) obtained by performing the same observation (the TEM photograph in FIG. Are shown side by side.
Furthermore, in the above experiment, an example in which the recording polarity is different depending on the mark length is shown. However, the same phenomenon (a gap is generated in the substrate at a high recording power) occurs when the recording power is low and high. confirmed.
[0044]
Example 1
On a polycarbonate substrate having guide grooves with a groove depth of 50 nm, ZnS-SiO as a void suppressing layer is formed.₂A thickness of 65 nm, a thickness of 6 nm of SiC as a layer having a light absorption function, and a thickness of a Co metal complex layer (dye layer) of the compound represented by Chemical Formula 1 that can be used for a DVD-R as a recording layer made of an organic compound. A write-once type optical recording medium was prepared by sequentially laminating a protective layer made of an ultraviolet curable resin with a thickness of about 60 nm, an Ag reflection layer of about 100 nm and an ultraviolet curable resin.
This optical recording medium is irradiated with laser light from the substrate side using an optical disk evaluation apparatus, DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. A signal of 8-16 modulation was recorded at a recording frequency of 65.4 MHz and a recording linear velocity of 6.0 m / s in the groove position on the near side as viewed from the light side.
As a result, the recording polarity is unified to Low to High within the recording power range that can be set by the evaluation apparatus used in this embodiment, and good jitter characteristics and modulation degree as shown in FIG. 14 are obtained. I was able to.
[0045]
Comparative Example 1
A write-once type optical recording medium having a structure of substrate / SiC (thickness 10 nm) / Co metal complex of compound represented by chemical formula (thickness: about 60 nm) / Ag reflection layer (thickness 150 nm) / protective layer was prepared. Recording was performed under the conditions (when there was no void suppression layer in Example 1).
<Recording conditions>
Recording linear density: 1T = 0.0917 μm
・ Modulation method: 8-16 modulation
・ Recording strategy: Basic strategy
Top-Tmp = 1.20-0.60 (T)
As a result, as shown in FIG. 15, a good recording with a recording power of about 9.0 mW and a jitter of 11.6% could be performed, but it was within the recording power range that can be set by the evaluation apparatus used in this comparative example. In FIG. 5, the change in recording polarity was observed (the recording polarity changed from Low to High to High to Low in the vicinity of 10.5 mw), and it was confirmed that the recording power margin of jitter was very narrow.
A 6T mark and a 14T mark were recorded again on this optical recording medium at a recording power of 8.0 mW. Similarly to Reference Example 3, this optical recording medium was cut in the radial direction by FIB, and the recording portion was observed by TEM.
As a result, it was confirmed that no gap was generated in the substrate in the recording portion with a recording power of 8.0 mW. Further, no tracking error (out of track) occurred during recording / reproduction.
On the other hand, as shown in FIGS. 12 to 13, the jitter did not fall below 15.0% in the recording power at which a gap was generated in the substrate, that is, the recording with a recording power of 9.5 mW or more. Further, at a recording power of about 9.5 mW or more, the ratio of causing a tracking error (out of track) during recording / reproduction increased with an increase in recording power.
[0046]
Example 2
On a polycarbonate substrate having a guide groove with a groove depth of 50 nm, ZrO is used as a void suppressing layer.₂35 nm in thickness, Si as a layer having a light absorption function, 15 nm in thickness, and a Co metal complex layer (dye layer) of the compound represented by Chemical Formula 1 that can be used for DVD-R as a recording layer made of an organic compound. A write-once type optical recording medium having a thickness of about 60 nm, an Ag reflecting layer thickness of about 100 nm, and a protective layer made of an ultraviolet curable resin was sequentially formed.
This optical recording medium is irradiated with laser light from the substrate side using an optical disk evaluation apparatus, DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. A signal of 8-16 modulation was recorded at a recording frequency of 65.4 MHz and a recording linear velocity of 6.0 m / s in the groove position on the near side as viewed from the light side.
As a result, the recording polarity is unified to Low to High within the recording power range that can be set by the evaluation apparatus used in the present embodiment, and good jitter characteristics and modulation degree as shown in FIG. 16 can be obtained. I was able to.
[0047]
From the results of the above reference examples and examples, the present invention “having a structure in which a light absorption layer having a light absorption function with respect to recording light is provided adjacent to the substrate or cover layer, in the substrate or in the cover. It was confirmed that the “write-once type optical recording medium in which the recording part is formed without forming the void part in the layer” is very important in obtaining good recording / reproducing characteristics.
Note that the recording / reproduction characteristics of the above-described embodiment are merely examples, and the recording polarity is not limited to, for example, Low to High.
[0048]
Example 3
As a result of the observation in FIGS. 11 to 13, it was confirmed that the long mark is likely to be generated in the substrate, and that it is difficult for the short recording mark such as 3T to 4T to be generated.
Therefore, in the recording strategy as shown in FIG. 15A, the setting is made such that the TEMP is decreased by 0.02 (T) for longer marks, and the temperature of the long marks is not increased more than necessary (there is no gap in the substrate). Recording was performed on a write-once optical recording medium having the same configuration as that prepared in Comparative Example 1.
As a result, in the normal recording strategy (in FIG. 17A, TEMP is fixed regardless of the recording mark length), a gap in the substrate was observed at about 14 m mark at about 9.5 mW. By using this recording strategy, no gap in the substrate was observed at the 14T mark even when recording was performed at about 9.5 mW.
That is, by using the recording strategy applied in the present embodiment, even when the recording power is increased, it is possible to suppress the generation of voids that are likely to occur in the long mark. (Enlarged) was obtained.
In addition to the recording strategy used in the present embodiment, the same effect can be achieved by setting, for example, the following a) to re).
In FIG. 17 (a)
B) The longer the mark, the smaller the TELP.
B) The TEFP is made smaller for longer marks.
C) Lower Pw1 or Pw2 for longer marks.
In FIG. 17 (b)
D) Decreasing Pw1 or Pw2 for longer marks.
E) The TEFP is made smaller for the longer mark.
In FIG. 17 (c)
F) Pw1 or Pw2 is made smaller for longer marks.
G) The TEFP is made smaller for the longer mark.
H) The longer the mark, the smaller the TELP.
B) Increase TSLP for longer marks.
Note that the recording strategy setting effective in the present invention is not limited to that described in this embodiment.
[0049]
In the above reference examples and examples, the case where the light absorption layer is in contact with the substrate is taken up. However, in the case of the cover layer, since the substrate and the material are basically the same, the same applies when the cover layer and the light absorption layer are in contact. It is.
The present invention is a method for improving the recording / reproducing characteristics of a write-once optical recording medium having a structure in which a light absorption layer having a light absorption function for recording light is provided adjacent to a substrate or a cover layer. This is an effective method, and does not deny a write-once optical recording medium having voids in the substrate.
The recording polarity depends on the optical constants and thicknesses of the dye layer and the light absorption layer, the deformation of the light absorption layer, the shape of the groove depth of the substrate, and the like. The recording polarity of the medium is not limited.
[0050]
【The invention's effect】
Since the write-once optical recording medium and the recording method of the present invention can suppress the generation of voids in the substrate or the cover layer that deteriorates the recording / reproducing characteristics, good recording / reproducing characteristics and good tracking characteristics The write-once type optical recording medium compatible with a short wavelength laser and the recording method therefor can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a layer structure of a conventional disk.
FIG. 2 is a diagram for explaining a waveform of a reproduction signal when a mark length recording mark is reproduced.
(A) General case
(B) Differential waveform having an inflection point near the front and rear edges of the recording mark.
(C) Differential waveform with an inflection point near the center of the recording mark
FIG. 3 is a view showing a recording result of Reference Example 1-A.
(A) The relationship between the recording mark length, the reproduction signal (RF level), and the modulation degree is shown.
(B) Reproduction signal when 3T mark and 4T mark are continuously recorded, and reproduction signal level when not recorded.
(C) Reproduction signal when 6T mark and 8T mark are continuously recorded, and reproduction signal level when not recorded.
(D) A reproduction signal when 3T mark and 14T mark are continuously recorded, and a reproduction signal level when not recorded.
FIG. 4 is a diagram showing a recording result of Reference Example 1-B.
(A) The relationship between the recording mark length, the reproduction signal (RF level), and the modulation degree is shown.
(B) Reproduction signal when 3T mark and 4T mark are continuously recorded, and reproduction signal level when not recorded.
(C) Reproduction signal when 6T mark and 8T mark are continuously recorded, and reproduction signal level when not recorded.
(D) A reproduction signal when 3T mark and 14T mark are continuously recorded, and a reproduction signal level when not recorded.
FIG. 5 is a diagram showing a recording result of Reference Example 1-C.
(A) The relationship between the recording mark length, the reproduction signal (RF level), and the modulation degree is shown.
(B) Reproduction signal when 3T mark and 4T mark are continuously recorded, and reproduction signal level when not recorded.
(C) Reproduction signal when 6T mark and 8T mark are continuously recorded, and reproduction signal level when not recorded.
(D) A reproduction signal when 3T mark and 14T mark are continuously recorded, and a reproduction signal level when not recorded.
FIG. 6 is a diagram showing a recording result of Reference Example 1-D.
(A) The relationship between the recording mark length, the reproduction signal (RF level), and the modulation degree is shown.
(B) Reproduction signal when 3T mark and 4T mark are continuously recorded, and reproduction signal level when not recorded.
(C) Reproduction signal when 6T mark and 8T mark are continuously recorded, and reproduction signal level when not recorded.
(D) A reproduction signal when 3T mark and 14T mark are continuously recorded, and a reproduction signal level when not recorded.
FIG. 7 is an explanatory diagram of groove parameters in a state where Pit is formed.
FIG. 8 is a diagram for explaining a recording state with and without a gap.
(A) Recording state without gaps
(B) Recording state with a gap
FIG. 9 is a diagram illustrating a result when a recording unit in which a Pit is formed in a land part is reproduced from the substrate side in Reference Example 2;
FIG. 10 is a diagram illustrating a result of reproducing a recording part in which a Pit is formed in a groove part from the substrate side in Reference Example 2;
FIG. 11 is a diagram in which the optical recording medium is cut in the track direction with an FIB and observed with an FE-SEM when the recording mark length in Reference Example 3 is 6T.
(A) The figure which observed the recording part
(B) The figure which observed the unrecorded part
12 is a diagram obtained by observing an optical recording medium in a radial direction with an FIB and observing with an FE-SEM when the recording mark length in Reference Example 3 is 14T. FIG.
FIG. 13 is a diagram of an optical recording medium cut in a track direction with an FIB and observed with an FE-SEM when the recording mark length of Reference Example 3 is 14T.
FIG. 14 is a diagram showing jitter and recording signal levels in a space portion and a mark portion when recording is performed on the optical recording medium of Example 1.
FIG. 15 is a diagram showing jitter when recording is performed on the optical recording medium of Comparative Example 1, and reproduction signal levels of the space portion and the mark portion.
FIG. 16 is a diagram showing jitter when recording is performed on the optical recording medium of Example 2, and reproduction signal levels of the space portion and the mark portion.
17 is a diagram showing a recording strategy used in Reference Example 3. FIG.
(A) Normal recording strategy
(B) Other recording strategies
(C) Still other recording strategies
[Explanation of symbols]
Mark Length Mark Head
T Reference clock
RF Level (V) RF (reproduction signal) level (volts)
Modulated amplitude modulation degree
Playback signal (RF) level when Unrec is not recorded
Top playback signal level (ie space part) when Top mark row is recorded
Bottom Minimum playback signal level when a mark row is recorded (ie, mark portion)
MA. Degree of modulation calculated by (Top-Bottom) / Top
Time0.5 (μs / div) Time (1 memory 0.5 microsecond)
A Width from the reference point to the near end of the adjacent land or groove
B Width from the reference point to the far end of the adjacent land or groove
C Width from the reference point to the near end of the next groove or land
D Width from the reference point to the far end of the next groove or land
ζ Height from groove bottom to land top
Recording mark deformed in the opposite direction to the incident direction of the Pit laser beam
Bump Recording mark deformed in the incident direction of laser light
Sum sum signal (playback signal)
Beam Position (μm) Beam position (deviation of beam center from mark center)
From Sub, Land Land recording from the substrate side
From Sub, Groove Groove recording from substrate side
No Bubble No gap
Bubble There is a gap
(N) When the width of the deformation area is 0.8525λ
(W) When the width of the deformation region is 1.8525λ
σ / Tw jitter
Pw1 recording power
Pw2 Bottom power
Pr bias power
Time from TEFP reference time to first pulse fall time
Time from TSFP reference time to leading pulse rise time
Time from TEMP reference time to multipulse fall time
Time from TSMP reference time to multi-pulse rise time
Time from TELP reference time to final pulse fall time
Time from TSLP reference time to final pulse rise time

Claims (9)

Between the substrate or the cover layer and the light absorption layer made of an inorganic material having a light absorption function with respect to the recording light, a void suppression layer is provided to suppress generation of voids in the substrate or the cover layer due to recording. A write-once optical recording medium characterized by having the above structure. On the substrate, there are a void suppressing layer for suppressing generation of voids in the substrate due to recording, a light absorbing layer made of an inorganic material having a light absorbing function for recording light, a recording layer made of an organic compound, and a reflective layer. A write-once optical recording medium characterized by having a sequentially provided structure. The void inhibiting _{layer, SiO 2, ZnS-SiO 2} , write-once optical recording medium according to claim 1 or 2, wherein one of ZrO _2, characterized in that a main component. The void inhibiting _{layer, ZnS, ZrO 2, Y 2} O 3 and write-once optical recording medium according to claim 1 or 2, wherein the is an oxide composed of SiO _2. The void suppression layer is made of ZrO ₂ , TiO ₂ , SiO ₂ , and X, and X is at least one selected from Al ₂ O ₃ , MgO, CaO, NbO, Y ₂ O ₃ , and CeO. The write-once type optical recording medium according to claim 1 or 2, characterized in that: The write-once type optical recording medium according to any one of claims 1 to 5, wherein the write-once type optical recording medium is compatible with a recording / reproducing wavelength of 405 nm. The write-once type optical recording medium according to any one of claims 1 to 6, wherein the recording polarity after recording is Low to High.   A write-once optical recording medium according to any one of claims 1 to 7, wherein recording is performed within a recording power range in which no gap is formed in the substrate or the cover layer. Recording method.   8. A recording method for a write-once optical recording medium according to claim 1, wherein recording is performed with a recording strategy in which no gap is formed in the substrate or the cover layer. .

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