JP3691501B2 - Optical recording medium - Google Patents
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Description
本発明は、高速記録が可能な相変化型光記録媒体に関する。 The present invention relates to a phase change optical recording medium capable of high-speed recording.
DVDの高速記録化に伴い記録層組成の組成比マージンが非常に限定されてきている。そして特許文献の多くは、Sb−TeをベースにGa、Ge、In等が添加された系を採用している(特許文献1〜16、非特許文献1参照)。これはカルコゲン元素(S、Se、Te)が「多くの元素と結合して多種の非晶質状態を作る」という特徴を有するためであり、この事が特にTeを中心に相変化材料の必須構成元素として注目されてきた理由の一つである。しかしながら本発明者らの研究によれば、DVD8倍速相当の高速記録をターゲットとした最適Ga−Sb系、Ge−Sb、In−Sb系組成領域でTeを添加すると、Teが記録層材料の結晶化速度を低下させてしまうため良好な高速記録特性が得られないことが分った。また本発明の記録層には、Au、Ag、Cuから選ばれる少なくとも一種の元素が必須構成元素として含まれ、かつそれらが記録層内部で結晶性粒子となっているが、上記文献においてこのような特徴が明記されたものはない。 With the increase in recording speed of DVDs, the composition ratio margin of the recording layer composition has been very limited. Many of patent documents employ a system in which Ga, Ge, In or the like is added based on Sb—Te (see Patent Documents 1 to 16 and Non-Patent Document 1). This is because the chalcogen elements (S, Se, Te) have the characteristic of “combining with many elements to form various amorphous states”, which is essential for phase change materials, especially Te. This is one of the reasons that has attracted attention as a constituent element. However, according to the study by the present inventors, when Te is added in the optimum Ga—Sb, Ge—Sb, and In—Sb composition region targeted for high-speed recording equivalent to DVD 8 × speed, Te becomes a crystal of the recording layer material. It has been found that good high-speed recording characteristics cannot be obtained because the conversion speed is lowered. The recording layer of the present invention contains at least one element selected from Au, Ag, and Cu as essential constituent elements, and these are crystalline particles inside the recording layer. There are no specific features.
本発明は、DVD8倍速相当の高速記録に適し、かつ記録材料の初期化が容易で初期化後の反射率分布が一様な相変化光記録媒体の提供を目的とする。
半導体レーザービームの照射により情報の書換えが可能な光記録媒体の一つに、結晶―非晶質間又は結晶―結晶間の相転移を利用した、いわゆる相変化光記録媒体が知られている。この相変化光記録媒体は単一ビーム繰り返し記録が可能で、またドライブ側の光学系がより単純であることを特徴とし、コンピュータ関連や映像音響に関する記録媒体として応用され世界的に普及している。そしてCD−R、CD−RWなどの光記録媒体は、普及と共に高速記録化が進んでおり、相変化光記録媒体も高密度画像記録などへの展望から、記録媒体の容量・密度の増加、従って高速記録が必須となっている。
このような相変化光記録媒体は、一般に基板と記録層を有し、この記録層の両面に耐熱性及び透光性を有す保護層が設けられている。また光ビーム入射方向と反対側の保護層上には、金属又は合金などからなる金属反射層が積層されている。そしてレーザー光のパワーを変化させるだけで記録・消去が可能であり、記録方式は一般に結晶状態を未記録・消去状態とし、非晶質状態を記録マーク(アモルファスマーク)としている。
An object of the present invention is to provide a phase change optical recording medium suitable for high-speed recording equivalent to DVD 8 × speed, easy to initialize a recording material, and having a uniform reflectance distribution after initialization.
As one of optical recording media in which information can be rewritten by irradiation with a semiconductor laser beam, a so-called phase change optical recording medium using a phase transition between crystal and amorphous or between crystal and crystal is known. This phase-change optical recording medium is capable of single-beam repetitive recording and has a simpler optical system on the drive side, and is widely used worldwide as a recording medium related to computers and audiovisuals. . Optical recording media such as CD-Rs and CD-RWs have been used for high-speed recording with the spread, and phase change optical recording media are also increasing in capacity and density of recording media from the perspective of high-density image recording. Therefore, high speed recording is essential.
Such a phase change optical recording medium generally has a substrate and a recording layer, and protective layers having heat resistance and translucency are provided on both sides of the recording layer. A metal reflection layer made of metal or alloy is laminated on the protective layer opposite to the light beam incident direction. Recording and erasing can be performed only by changing the power of the laser beam. In general, the recording system uses a crystalline state as an unrecorded / erased state and an amorphous state as a recording mark (amorphous mark).
相変化光記録媒体の記録原理は次のようである。記録層の結晶状態/非晶質状態の切り替えには3つの出力レベルでパルス化された集束レーザビームを用いる。その際、最も高い出力レベルは記録層の溶融に使用され、中間の出力レベルは融点直下、結晶化温度よりも高い温度まで記録層を加熱するのに使用し、最も低いレベルは記録層の加熱又は冷却の制御に使用される。最も高い出力レベルのレーザパルスにより溶融した記録層は、続く急冷により非晶質ないしは微結晶となって反射率低下が起こり、記録マークとなる。また、中間出力のレーザパルスでは全て結晶質となり消去が可能となる。このように、出力レベル間で書込みレーザパルスを変化させる事により記録層に交互に結晶領域と非晶質領域を作成することができ、情報が記憶される。 The recording principle of the phase change optical recording medium is as follows. To switch the crystalline state / amorphous state of the recording layer, a focused laser beam pulsed at three output levels is used. In this case, the highest output level is used to melt the recording layer, the intermediate output level is used to heat the recording layer just below the melting point and higher than the crystallization temperature, and the lowest level is used to heat the recording layer. Or it is used for control of cooling. The recording layer melted by the laser pulse with the highest output level becomes amorphous or microcrystalline by the subsequent rapid cooling, resulting in a decrease in reflectivity and a recording mark. Further, all laser pulses with an intermediate output become crystalline and can be erased. As described above, by changing the writing laser pulse between the output levels, a crystalline region and an amorphous region can be alternately formed in the recording layer, and information is stored.
高速記録を実現するに当っては、記録層材料として速い結晶化速度を有する相変化材料が求められる。このような相変化材料として、これまでにGe−Te、Ge−Te−Se、In−Sb、Ga−Sb、Ge−Sb−Te、Ag−In−Sb−Te等が、結晶化速度が速く、かつ高速記録時の消去比が高いことで注目されてきている。
しかしながら、高速記録の実現は記録層材料の結晶化速度を速めるだけでは不充分であり、別の大きな課題として「初期化の容易さの確保」という問題がある。例えば高速記録材料の一つとして知られるGa−Sb系の相変化材料は、結晶化速度が極めて速いことが報告されているが(非特許文献1)、その結晶化温度は350℃と非常に高く初期化が困難であり、また仮に高い初期化パワーを照射して初期化を行っても、初期化後の反射率にばらつきが生じ、記録特性に大きな影響を与えてしまう。
In order to realize high-speed recording, a phase change material having a high crystallization speed is required as a recording layer material. As such a phase change material, Ge-Te, Ge-Te-Se, In-Sb, Ga-Sb, Ge-Sb-Te, Ag-In-Sb-Te, etc. have been fast so far. In addition, it has been attracting attention because of its high erasure ratio during high-speed recording.
However, in order to realize high-speed recording, it is not sufficient to simply increase the crystallization speed of the recording layer material, and there is a problem of “ensuring easy initialization” as another big problem. For example, a Ga—Sb phase change material known as one of high-speed recording materials has been reported to have an extremely high crystallization speed (Non-patent Document 1), but the crystallization temperature is as high as 350 ° C. Initialization is difficult, and even if initialization is performed by irradiating with a high initialization power, the reflectance after the initialization varies, which greatly affects the recording characteristics.
今回本発明者らは、DVD8倍速相当の高速記録をターゲットとした光記録媒体の開発過程において、上記課題を解決する方法として、本発明者らが8倍速記録に特に適すと考えるGa―Sb系相変化材料に着目し、これにAu、Ag、Cuから選ばれる少なくとも一種類以上の元素を添加し、初期結晶化を行う過程で記録層内部に結晶性粒子を生成させることで、初期化が飛躍的に改善され、かつ初期化後の反射率分布が均一となることを見出し、本発明を完成するに至った。
即ち、上記課題は、次の1)〜6)の発明(本発明1〜6という)によって解決される。
1) 透明基板上に少なくとも第一保護層、相変化記録層、第二保護層、金属反射層を有し、相変化記録層が次の組成式で表される合金からなることを特徴とする光記録媒体。
(X1)αSbβ(X2)γ
(但し、X1はGa、Ge、Inから選ばれる少なくとも一種の元素、X2はAu、Ag、Cuから選ばれる少なくとも一種の元素、α、β、γは原子%、2≦α≦20、55≦β≦95、0<γ≦10、α+β+γ=100)
2) 合金が、Al、Zn、Mg、Tl、Pb、Sn、Bi、Cd、Hg、Se、C、N、Mn、Dyから選ばれた少なくとも一種の添加元素を1〜40原子%含むことを特徴とする請求項1記載の光記録媒体。
3) 保護層が、ZnSとSiO2の混合物からなることを特徴とする1)又は2)記載の光記録媒体。
4) 金属反射層が、Ag又はAgを主成分とする合金からなることを特徴とする1)〜3)の何れかに記載の光記録媒体。
5) 第二保護層と金属反射層との間に、Si又はSiCを主成分とする第三保護層を設けることを特徴とする4)記載の光記録媒体。
6) 最適記録線速度が、28.0±3m/sの範囲にあることを特徴とする1)〜5)の何れかに記載の光記録媒体。
In the process of developing an optical recording medium targeted for high-speed recording equivalent to DVD 8 × speed, the present inventors have proposed a Ga—Sb system that the present inventors consider to be particularly suitable for 8 × speed recording as a method for solving the above problems. Focusing on the phase change material, at least one element selected from Au, Ag, and Cu is added thereto, and crystalline particles are generated in the recording layer in the process of initial crystallization. The present invention has been completed by remarkably improving and finding that the reflectance distribution after initialization becomes uniform.
That is, the above-mentioned problems are solved by the following inventions 1) to 6) (referred to as the present inventions 1 to 6).
1) It has at least a first protective layer, a phase change recording layer, a second protective layer, and a metal reflective layer on a transparent substrate, and the phase change recording layer is made of an alloy represented by the following composition formula: Optical recording medium.
(X 1 ) αSbβ (X 2 ) γ
(Where X 1 is at least one element selected from Ga, Ge, In, X 2 is at least one element selected from Au, Ag, Cu, α, β, γ are atomic%, 2 ≦ α ≦ 20, 55 ≦ β ≦ 95, 0 <γ ≦ 10, α + β + γ = 100)
2) The alloy contains 1 to 40 atomic% of at least one additive element selected from Al, Zn, Mg, Tl, Pb, Sn, Bi, Cd, Hg, Se, C, N, Mn, and Dy. The optical recording medium according to claim 1.
3) The optical recording medium according to 1) or 2), wherein the protective layer comprises a mixture of ZnS and SiO 2 .
4) The optical recording medium according to any one of 1) to 3), wherein the metal reflective layer is made of Ag or an alloy containing Ag as a main component.
5) The optical recording medium according to 4), wherein a third protective layer mainly comprising Si or SiC is provided between the second protective layer and the metal reflective layer.
6) The optical recording medium according to any one of 1) to 5), wherein the optimum recording linear velocity is in a range of 28.0 ± 3 m / s.
以下、上記本発明について詳しく説明する。
本発明では、DVD8倍速相当の高速記録に適し、かつ初期化が容易で初期化後の反射率分布が一様となる相変化材料として、本発明1の組成式の合金を用いる。主要構成元素であるSbは高速記録を実現できる優れた相変化材料であり、Sb比を変化させることで結晶化速度を調整でき、比率を高くすれば結晶化速度を速めることができる。しかしSb単独では、DVD8倍速相当の速い結晶化速度及び保存安定性に優れた記録層材料を実現することが困難であるため、オーバーライト特性や保存信頼性を損なわずに結晶化速度を速める方法として、Ga、Inから選ばれる少なくとも一種の元素を添加し、また保存信頼性を向上させる方法としてGa、In、特にGeを添加する。
Hereinafter, the present invention will be described in detail.
In the present invention, an alloy having the composition formula of the present invention 1 is used as a phase change material that is suitable for high-speed recording equivalent to DVD 8 × speed, is easy to initialize, and has a uniform reflectance distribution after initialization. Sb, which is a main constituent element, is an excellent phase change material capable of realizing high-speed recording. The crystallization speed can be adjusted by changing the Sb ratio, and the crystallization speed can be increased by increasing the ratio. However, with Sb alone, it is difficult to realize a recording layer material having a high crystallization speed equivalent to DVD 8 × speed and excellent storage stability. Therefore, a method for increasing the crystallization speed without impairing overwrite characteristics and storage reliability. As a method for adding at least one element selected from Ga and In, and for improving storage reliability, Ga, In, and especially Ge are added.
Gaは少ない添加量で結晶化速度を速くすることができ、また相変化材料の結晶化温度を高める効果を持つことからマークの安定性(保存信頼性)に効果的である。
Geは結晶化速度を速める効果は持たないが、Gaほど結晶化温度を上げず少量の添加で保存信頼性を飛躍的に向上させることができるため、Gaと同様に重要な元素である。
InはGaと同様の効果を持ち、Gaほど結晶化温度を高くしないというメリットがあるため、初期化の問題を考慮した場合、Gaを補う元素として用いると有効である。
このようなX1−Sb系(X1はGa、Ge、Inから選ばれる少なくとも一種の元素)の相変化材料は、組成比の調整で結晶化速度が速くかつ保存安定性に優れた記録層材料を設計することができる。しかしながら先に述べたように、このような材料は一般に結晶化温度が高いという欠点を有し、初期化不良の問題を新たに生じさせてしまう。
Ga can increase the crystallization speed with a small addition amount, and also has an effect of increasing the crystallization temperature of the phase change material, which is effective in the stability (storage reliability) of the mark.
Although Ge does not have an effect of increasing the crystallization speed, it is an important element similar to Ga because it does not raise the crystallization temperature as much as Ga and can improve storage reliability with a small amount of addition.
In has the same effect as Ga and has the advantage of not raising the crystallization temperature as much as Ga. Therefore, when considering the problem of initialization, it is effective to use it as an element supplementing Ga.
Such an X 1 -Sb-based phase change material (X 1 is at least one element selected from Ga, Ge, and In) is a recording layer having a high crystallization speed and excellent storage stability by adjusting the composition ratio. Material can be designed. However, as described above, such a material generally has a drawback of a high crystallization temperature, which newly causes a problem of initialization failure.
そこで検討した結果、本発明者らは、記録層材料中にAu、Ag、Cuから選ばれる少なくとも一種の元素を添加し、結晶性粒子を生成させれば、記録層中に予め「結晶核」を生成させておくことになり、高速結晶化材料の初期化問題が解決できることを見出した。
金属結晶性粒子は、記録層中に存在する金属原子をX2 0とすると、次の〔式1〕の過程を経て生成されるものと思われる。
〔式1〕 nX2 0+加熱→(X2 0)n(結晶性粒子)
また、記録層中に金属原子がイオンと存在している場合は、次の〔式2〕の過程も考えられる。
〔式2〕 X2 ++Sb2++hν→X2 0+Sb4+(Sbによる還元反応)
Sbによる還元反応は、通常、感光反応とされており、紫外線照射等によって反応が進行するとされているが、この場合、例えば紫外線硬化樹脂を硬化する際に用いる紫外線の影響で金属原子が生成することも考えられる。
何れにせよ記録層中に存在する金属原子X2 0が、初期化時のレーザー照射によって得た熱により〔式1〕に示すように微細な金属結晶性粒子へと変換され、このような「結晶核」の役目をする粒子が記録層中の内部に均等に形成されることで、初期化が容易となり、かつ反射率分布の一様な初期化を可能にするものと思われる。
As a result, the present inventors have previously added “crystal nuclei” in the recording layer by adding at least one element selected from Au, Ag and Cu to the recording layer material to generate crystalline particles. It was found that the initialization problem of the high-speed crystallization material can be solved.
It is considered that the metal crystalline particles are generated through the following process of [Formula 1], where X 2 0 is the metal atom present in the recording layer.
[Formula 1] nX 2 0 + heating → (X 2 0 ) n (crystalline particles)
Further, when metal atoms are present as ions in the recording layer, the following process of [Formula 2] is also conceivable.
[Formula 2] X 2 + + Sb 2+ + hν → X 2 0 + Sb 4+ (reduction reaction with Sb)
The reduction reaction by Sb is usually a photosensitive reaction, and it is said that the reaction proceeds by ultraviolet irradiation or the like. In this case, for example, metal atoms are generated by the influence of ultraviolet rays used when curing an ultraviolet curable resin. It is also possible.
Metal atoms X 2 0 present in the recording layer in any case, are converted by heat obtained by laser irradiation at the time of initialization into fine metal crystal particles as shown in [Equation 1], such " It seems that the particles that act as “crystal nuclei” are uniformly formed inside the recording layer, thereby facilitating initialization and enabling uniform initialization of the reflectance distribution.
更に、Au、Ag、Cuは、保存信頼性に効果的な添加元素であるため、初期化不良を解決するばかりでなく、保存信頼性にも優れた相変化材料を設計することができる。
従って、本発明1は、記録層材料として、X1−Sb系化合物(X1はGa、Ge、Inから選ばれる少なくとも一種の元素)の持つ高速結晶化特性に注目し、その特性を利用する一方で、前記化合物の欠点である高い結晶化温度によりもたらされる初期化不良の問題を、Au、Ag、Cuから選ばれる少なくとも一種の元素を添加して記録層材料中に結晶性粒子を生成させることで改善したものであり、本発明1によって高速記録と保存信頼性の両特性を満足し、かつ記録材料の初期化が容易で初期化後の反射率分布が一様な光学的情報記録媒体を実現できる。
Furthermore, since Au, Ag, and Cu are additive elements effective for storage reliability, it is possible to design a phase change material that not only solves initialization failure but also has excellent storage reliability.
Therefore, the present invention 1 pays attention to the high-speed crystallization characteristic of the X 1 -Sb compound (X 1 is at least one element selected from Ga, Ge, In) as the recording layer material, and uses the characteristic. On the other hand, the problem of poor initialization caused by a high crystallization temperature, which is a defect of the above compound, is produced by adding at least one element selected from Au, Ag, and Cu to generate crystalline particles in the recording layer material. An optical information recording medium satisfying both the characteristics of high-speed recording and storage reliability according to the first aspect of the present invention, the initialization of the recording material being easy, and the reflectance distribution after the initialization is uniform Can be realized.
DVD8倍速相当の高速記録に適した相変化記録材料を設計するためには、記録層材料中のAu、Ag、Cuの添加量γを10原子%以下とする。先に述べたようにAu、Ag、Cuは保存信頼性に優れ、かつ高速記録材料の初期化不良を改善するのに有効な元素であるが、反面、記録層材料の結晶化限界速度を低下させ高速記録を妨げる働きをする特性も備えている。そのためAu、Ag、Cuの添加量が10原子%を超えると、DVD8倍速相当の高速記録に適した相変化記録材料を設計することが困難となるため、添加量の上限は10原子%とする必要がある。しかし、少なすぎると、Au、Ag、Cuの添加効果が不明瞭となってしまうため下限は1原子%とすることが好ましい。 In order to design a phase change recording material suitable for high-speed recording equivalent to DVD 8 × speed, the additive amount γ of Au, Ag, and Cu in the recording layer material is set to 10 atomic% or less. As described above, Au, Ag, and Cu are elements that are excellent in storage reliability and effective in improving the initialization failure of the high-speed recording material, but on the other hand, the crystallization limit speed of the recording layer material is lowered. It also has the property of preventing high-speed recording. Therefore, if the addition amount of Au, Ag, and Cu exceeds 10 atomic%, it becomes difficult to design a phase change recording material suitable for high-speed recording equivalent to DVD 8 × speed, so the upper limit of the addition amount is 10 atomic%. There is a need. However, if the amount is too small, the effect of adding Au, Ag, and Cu becomes unclear, so the lower limit is preferably 1 atomic%.
SbとGa、Ge、Inの組成比に関しては、式中のαを2原子%以上とする必要がある。例えばX1がGa及び/又はInからなりαが2原子%未満の場合、或いはβが55原子%より少ない場合は、結晶化速度が低下し、DVD8倍速に相当する28m/sの記録線速下でのオーバーライトが困難となる。またαが2原子%未満の場合は、保存信頼性も低下してしまう。Ga及び/又はInは、少ない添加量で結晶化速度を速くすることができ、また特にGaは相変化材料の結晶化温度を高める効果を持つことからマークの安定性向上に効果的な元素である。しかし、式中のαが20原子%より大きいと初期化が極めて難しくなり、特にGaの添加量が多いと逆に結晶化温度が高くなり過ぎ、初期化時に均一で高い反射率を持つ結晶状態を得ることが難しくなる。一方InはGaと同様の効果を持ち、またGaほど結晶化温度を高くしないというメリットがあるため、初期化の問題を考慮した場合、Gaを補う元素として用いると有効である。しかし、Inの過剰な添加も繰り返し記録特性を低下させ、また反射率低下の原因となるため、20原子%以下とすることが好ましい。 Regarding the composition ratio of Sb, Ga, Ge, and In, α in the formula needs to be 2 atomic% or more. For example, when α becomes X 1 from Ga and / or In is less than 2 atomic%, or if β is less than 55 atomic%, the crystallization rate is lowered, the recording linear velocity of 28 m / s, which corresponds to DVD8 speed Overwriting below becomes difficult. Further, when α is less than 2 atomic%, the storage reliability is also lowered. Ga and / or In can increase the crystallization speed with a small addition amount, and in particular, Ga has an effect of increasing the crystallization temperature of the phase change material. is there. However, when α in the formula is larger than 20 atomic%, initialization becomes extremely difficult. In particular, when the amount of Ga added is large, the crystallization temperature becomes excessively high, and the crystalline state has a uniform and high reflectance at the time of initialization. It becomes difficult to get. On the other hand, In has the same effect as Ga and has the advantage of not raising the crystallization temperature as much as Ga. Therefore, when considering the problem of initialization, it is effective to use it as an element supplementing Ga. However, excessive addition of In repeatedly degrades the recording characteristics and causes a decrease in reflectivity.
X1がGe単独の場合、GeはGaほど結晶化温度を上げず少量の添加で保存信頼性を飛躍的に向上させることができるため、保存信頼性に特に優れた記録材料を実現できる。Geは結晶化速度の速い記録層のアモルファス安定化に特に効果を奏し、その効果は添加量が2原子%以上で現われ、添加量が増えるに従いその効果は高くなる。しかし一方で、Geには結晶化速度を低下させてしまう効果があり、また過剰の添加はオーバーライトによるジッター上昇などの弊害も招くことから、上限は20原子%以下とすることが好ましい。Geの添加量を20原子%としても、βが95原子%を超える場合は、結晶化速度の上昇が急激となりマーク形成が困難となる他、保存信頼性が低下するため、βは95原子%以下とすることが好ましい。
更に、X1がGa及び/又はInとGeからなる場合は、Ga及び/又はIn量を減らしてその分Geを添加し、αを2原子%以上とすることによっても良好な保存信頼性を得ることができる。
When X 1 is Ge alone, Ge does not raise the crystallization temperature as much as Ga, and storage reliability can be drastically improved by addition of a small amount. Therefore, a recording material having particularly excellent storage reliability can be realized. Ge is particularly effective for stabilizing an amorphous recording layer having a high crystallization speed. The effect appears when the addition amount is 2 atomic% or more, and the effect increases as the addition amount increases. On the other hand, Ge has an effect of decreasing the crystallization speed, and excessive addition also causes adverse effects such as an increase in jitter due to overwriting. Therefore, the upper limit is preferably 20 atomic% or less. Even if the addition amount of Ge is 20 atomic%, if β exceeds 95 atomic%, the increase in crystallization speed becomes abrupt and mark formation becomes difficult, and the storage reliability decreases, so β is 95 atomic%. The following is preferable.
Furthermore, if X 1 is composed of Ga and / or In and Ge, Ga and / or by reducing the amount of In added correspondingly Ge, good storage reliability by making the 2 atomic percent or more α Obtainable.
本発明2のように、DVD8倍速相当の高速記録に適し、かつ初期化が容易で初期化後の反射率分布が一様となる相変化材料として、本発明1で規定する組成式の合金に、更に添加元素としてAl、Zn、Mg、Tl、Pb、Sn、Bi、Cd、Hg、Se、C、N、Mn、Dyから選ばれる少なくとも一種の元素を加えた合金は、本発明を構成する記録材料としてより一層好適である。これらの元素は、それぞれが記録特性、保存信頼性を向上させる独自の効果を有するため、適量の添加によりX1‐Sb‐X2合金の特性を更に向上させることができる。
上記添加元素の効果について説明すると、Ga、In以外に、Tl、Pb、Sn、Bi、Al、Zn、Mg、Cd、Hgにも結晶化限界速度を速くする効果がある。中でもSbに最も原子番号が近くSbとの親和性が高いと思われるSnが好ましく、結晶化限界速度を速くすると共にオーバーライト特性も改善する。しかし、添加量が多すぎると再生光劣化や初期ジッターの劣化を引き起すため、組成範囲は何れの元素の場合も40原子%以下とする必要がある。
As a phase change material suitable for high-speed recording equivalent to DVD 8 × speed as in the present invention 2 and easy to initialize and having a uniform reflectance distribution after initialization, an alloy having a composition formula defined in the present invention 1 is used. Further, an alloy in which at least one element selected from Al, Zn, Mg, Tl, Pb, Sn, Bi, Cd, Hg, Se, C, N, Mn, and Dy is added as an additional element constitutes the present invention. It is even more suitable as a recording material. Since each of these elements has a unique effect of improving recording characteristics and storage reliability, the characteristics of the X 1 -Sb-X 2 alloy can be further improved by adding an appropriate amount.
The effect of the additive element will be described. In addition to Ga and In, Tl, Pb, Sn, Bi, Al, Zn, Mg, Cd, and Hg also have an effect of increasing the crystallization limit speed. Among them, Sn, which has an atomic number closest to Sb and is considered to have a high affinity with Sb, is preferable, and increases the crystallization limit speed and improves the overwrite characteristics. However, if the addition amount is too large, it causes deterioration of reproduction light and initial jitter, so the composition range needs to be 40 atomic% or less for any element.
保存信頼性に関しては、Ge以外に、Al、C、N、Seも効果を奏する。更にAl、Seの場合は高速結晶化にも寄与する。またSeは記録感度の向上にも寄与する。
更に本発明者等の研究によって、MnやDyもInと同様の効果を奏することが判り、特にMnはGe添加量をそれほど増やす必要のない保存信頼性に優れた添加元素であることが判った。Mnの最適添加量は1〜15原子%であり、1原子%より少ないと効果が現われず、15原子%より多いと未記録状態(結晶状態)の反射率が低くなり過ぎる。
記録層の膜厚は6〜20nmとする。6nmよりも薄いと繰り返し記録による記録特性の劣化が著しく、また20nmよりも厚いと繰り返し記録による記録層の移動が起り易くジッター増加が激しくなるので好ましくない。更に、結晶と非晶質の吸収率差をなるべく小さくして消去特性を向上させるためには、記録層の厚さが薄い方がよいので、好ましい厚さは8〜16nmである。
Regarding storage reliability, Al, C, N, and Se are also effective in addition to Ge. Further, Al and Se contribute to high-speed crystallization. Se also contributes to an improvement in recording sensitivity.
Furthermore, it has been found through research by the present inventors that Mn and Dy have the same effect as In, and in particular, Mn is an additive element with excellent storage reliability that does not require much addition of Ge. . The optimum addition amount of Mn is 1 to 15 atomic%, and if it is less than 1 atomic%, the effect does not appear, and if it exceeds 15 atomic%, the reflectivity in the unrecorded state (crystalline state) becomes too low.
The film thickness of the recording layer is 6 to 20 nm. When the thickness is less than 6 nm, the recording characteristics are remarkably deteriorated by repeated recording. When the thickness is more than 20 nm, the recording layer easily moves due to repeated recording, and the increase in jitter becomes severe. Furthermore, in order to reduce the difference in absorption between crystal and amorphous as much as possible to improve the erasing characteristics, it is preferable that the thickness of the recording layer is thin, so the preferred thickness is 8 to 16 nm.
第一保護層の膜厚は、熱的及び光学的条件から最適な範囲が選定されるが、通常は40〜200nm、好ましくは40〜100nmとする。
第二保護層の膜厚については、記録層の冷却に関係し直接的な影響が大きいので、良好な消去特性・繰り返し記録耐久性を得るために2nm以上は必要である。これよりも薄いとクラック等の欠陥を生じ繰り返し記録耐久性が低下するほか、記録感度が悪くなるため好ましくない。しかし、20nmを越えると記録層の冷却速度が遅くなるためマーク形成が難しくなり、マーク面積が小さくなってしまうので好ましくない。好ましい膜厚範囲は4〜15nmである。
本発明3では、保護層にZnSとSiO2の混合物を用いる。ZnSとSiO2の混合物は、保護層に求められる耐熱性、低熱伝導率性、化学的安定性に優れており、膜の残留応力が小さく、記録/消去の繰り返しによっても記録感度、消去比などの特性劣化が起き難く、更には記録層との密着性にも優れるという点で本発明を構成する保護層として適切である。
The optimum thickness of the first protective layer is selected from the thermal and optical conditions, but is usually 40 to 200 nm, preferably 40 to 100 nm.
The film thickness of the second protective layer is directly related to the cooling of the recording layer, so that it is 2 nm or more in order to obtain good erasing characteristics and repeated recording durability. If it is thinner than this range, defects such as cracks are caused, and the recording durability is repeatedly lowered, and the recording sensitivity is deteriorated, which is not preferable. However, if the thickness exceeds 20 nm, the cooling rate of the recording layer becomes slow, so that mark formation becomes difficult and the mark area becomes small. A preferable film thickness range is 4 to 15 nm.
In the present invention 3, a mixture of ZnS and SiO 2 is used for the protective layer. A mixture of ZnS and SiO 2 is excellent in heat resistance, low thermal conductivity, and chemical stability required for the protective layer, has a small residual stress in the film, and has a recording sensitivity, an erasing ratio, etc. even by repeated recording / erasing. It is suitable as a protective layer constituting the present invention in that the characteristic deterioration is difficult to occur and the adhesiveness to the recording layer is excellent.
本発明4のように純Ag又はAg合金を金属反射層に用いると、ZnSとSiO2の混合物のような硫黄を含む保護層を用いた場合、硫黄が硫化反応によってAgを腐食し欠陥となる不具合が生じてしまう。従って、このような反応を防止するために第三保護層を設けると良い。この第三保護層には、次の(1)〜(5)の観点から適切な材料を選定するが、好ましい具体例としてはSi又はSiCを主成分とする材料が挙げられる。
(1)Agの硫化反応を防ぐバリヤ能力があること。
(2)レーザー光に対して光学的に透明であること。
(3)アモルファスマーク形成のため熱伝導率が低いこと。
(4)保護層や金属反射層との密着性が良いこと。
(5)形成が容易であること。
第三保護層の膜厚は、Agの硫化反応を防止するため少なくとも2nm必要である。
反射層の膜厚は、通常100〜300nmとする。
When pure Ag or an Ag alloy is used for the metal reflection layer as in the present invention 4, when a protective layer containing sulfur such as a mixture of ZnS and SiO 2 is used, sulfur corrodes Ag due to a sulfurization reaction and becomes a defect. A malfunction will occur. Therefore, a third protective layer is preferably provided to prevent such a reaction. An appropriate material is selected for the third protective layer from the viewpoints of the following (1) to (5). A preferable specific example includes a material mainly composed of Si or SiC.
(1) It has a barrier ability to prevent the sulfurization reaction of Ag.
(2) It is optically transparent to laser light.
(3) Low thermal conductivity due to formation of amorphous marks.
(4) Good adhesion to the protective layer and the metal reflective layer.
(5) It is easy to form.
The thickness of the third protective layer is required to be at least 2 nm in order to prevent the sulfurization reaction of Ag.
The thickness of the reflective layer is usually 100 to 300 nm.
本発明によれば、DVD8倍速相当の高速記録に適し、かつ記録材料の初期化が容易で初期化後の反射率分布が一様な相変化光記録媒体を提供できる。 According to the present invention, it is possible to provide a phase change optical recording medium suitable for high-speed recording equivalent to DVD 8 × speed, easy to initialize a recording material, and having a uniform reflectance distribution after initialization.
以下、実施例及び比較例により本発明を更に具体的に説明するが、本発明は、これらの実施例や使用した初期化装置等により何ら制限されるものではない。例えば、成膜の順序が逆になる表面記録型の書換え型光記録媒体や、DVD系に見られるような、貼り合せ用基板8に代えて樹脂保護層を介して同一又は異なる光記録媒体が互いに2枚貼り合わされた記録媒体等に対しても適用しうる。
また、図1は、実施例及び比較例として作製した相変化光ディスク(以下、光ディスクという)の概略断面図であり、レーザー光の案内溝が設けられた透明な基板1の上面に、第一保護層2、結晶と非晶質の可逆的相変化をする相変化記録層3、第二保護層4、第三保護層5、金属反射層6、樹脂保護層7を備え、最後に基板と同様な貼り合せ用基板8が貼着された層構成を有する。
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not restrict | limited at all by these Examples, the initialization apparatus used, etc. For example, a surface recording type rewritable optical recording medium in which the order of film formation is reversed, or an optical recording medium that is the same or different via a resin protective layer instead of the bonding substrate 8 as seen in a DVD system. The present invention can also be applied to a recording medium or the like in which two sheets are bonded together.
FIG. 1 is a schematic cross-sectional view of a phase change optical disk (hereinafter referred to as an optical disk) manufactured as an example and a comparative example. The first protection is provided on the upper surface of a transparent substrate 1 provided with a laser light guide groove. A layer 2, a phase change recording layer 3 that reversibly changes between crystalline and amorphous, a second protective layer 4, a third protective layer 5, a metal reflective layer 6, and a resin protective layer 7, and finally the same as the substrate It has a layer structure in which a substrate for bonding 8 is attached.
[実施例1〜5]
基板1の上にスパッタリング法により、第一保護層2、相変化記録層3、第二保護層4、第三保護層5、金属反射層6をこの順に成膜し、その上にスピンコート法により樹脂保護層7を塗布し、更に貼り合せ用基板8を貼り合せて光ディスクを作製した。次いで、初期化装置として日立コンピュータ機器社製の‘PCR DISK INITIALIZER’を使用し、上記光ディスクを一定線速度で回転させ、パワー密度10〜20mW/μm2のレーザー光を、半径方向に一定の送り量で移動させながら照射することにより初期化した。
基板1には、直径12cm、厚さ0.6mmのポリカーボネート製で、トラックピッチ
0.74μmの案内溝付き基板を用いた。第一保護層2は、厚さ65nmのZnS(80モル%)−SiO2(20モル%)とした。相変化記録層3は厚さ16nmとし、Ga9Sb86Ag5(実施例1)、Ge16Sb79Ag5(実施例2)、In13Sb82Ag5(実施例3)、Ga9Ge3Sb85Ag3(実施例4)、Ga8In4Sb83Ag5(実施例5)とした。第二保護層4は、厚さ14nmのZnS(80モル%)−SiO2(20モル%)とした。第三保護層5は、厚さ4nmのSiCとした。金属反射層6は、厚さ140nmのAgとした。貼り合せ用基板8は、基板1と同一の直径12cm、厚さ0.6mmのポリカーボネート製基板を用いた。
[Examples 1 to 5]
A first protective layer 2, a phase change recording layer 3, a second protective layer 4, a third protective layer 5, and a metal reflective layer 6 are formed in this order on the substrate 1 by a sputtering method, and a spin coating method is formed thereon. Then, the resin protective layer 7 was applied, and the bonding substrate 8 was further bonded to produce an optical disk. Next, 'PCR DISK INITIALIZER' manufactured by Hitachi Computer Equipment Co., Ltd. is used as an initialization device, the optical disk is rotated at a constant linear velocity, and a laser beam with a power density of 10 to 20 mW / μm 2 is sent at a constant rate in the radial direction. It was initialized by irradiating while moving by the amount.
As the substrate 1, a substrate with a guide groove made of polycarbonate having a diameter of 12 cm and a thickness of 0.6 mm and having a track pitch of 0.74 μm was used. The first protective layer 2, the thickness 65nm of ZnS (80 mol%) - was SiO 2 (20 mol%). The phase change recording layer 3 has a thickness of 16 nm, Ga 9 Sb 86 Ag 5 (Example 1), Ge 16 Sb 79 Ag 5 (Example 2), In 13 Sb 82 Ag 5 (Example 3), Ga 9 Ge 3 Sb 85 Ag 3 (Example 4) and Ga 8 In 4 Sb 83 Ag 5 (Example 5). The second protective layer 4 was made of ZnS (80 mol%)-SiO 2 (20 mol%) having a thickness of 14 nm. The third protective layer 5 was made of SiC having a thickness of 4 nm. The metal reflective layer 6 was made of Ag having a thickness of 140 nm. As the bonding substrate 8, a polycarbonate substrate having a diameter of 12 cm and a thickness of 0.6 mm, which is the same as that of the substrate 1, was used.
[比較例1]
記録層をGa10Sb90に変更した点以外は、実施例1と同様の層構成及び製造方法で光ディスクを作製した。実施例1に比べ本比較例では記録層材料にAgが含まれない組成となっている。
[Comparative Example 1]
An optical disc was manufactured by the same layer configuration and manufacturing method as in Example 1 except that the recording layer was changed to Ga 10 Sb 90 . Compared to Example 1, this comparative example has a composition in which Ag is not contained in the recording layer material.
[比較例2]
記録層をGa9Sb81Ag5Te5に変更した点以外は、実施例1と同様の層構成及び製造方法で光ディスクを作製した。本比較例は実施例1の記録層材料にTeを5原子%添加したものである。
[Comparative Example 2]
An optical disc was manufactured by the same layer configuration and manufacturing method as in Example 1 except that the recording layer was changed to Ga 9 Sb 81 Ag 5 Te 5 . This comparative example is obtained by adding 5 atomic% of Te to the recording layer material of Example 1.
初期化後の各光ディスクについて、反射率分布及び記録特性を評価した。
反射率分布の評価は、光ディスクから得られるRf信号の信号幅を測定することにより行った。記録特性の評価は、波長660nm、NA0.65のピックアップを有する光ディスク評価装置(パルステック社製DDU−1000)を用いて、記録線速度28m/s(DVDの8倍速に相当)、線密度0.267μm/bitの条件で、EFM+変調方式により3Tシングルパターンを10回オーバーライトしたときのC/N比を評価することで行った。評価基準は次の通りである。
・反射率分布の評価:現在市販されている2.4倍速記録対応DVD+RW(表2に比較例3として示した)の初期化後の反射率分布をおおよその基準として比較した。
また実施例1と比較例1については、初期化後の記録層の状態を透過電子顕微鏡(TEM)により観察し、結晶状態の違いについても評価を行った(図2参照)。
・記録特性の評価:書換え型の光ディスクシステムを実現する場合、そのC/N比は少なくとも45dB以上必要であるとされており、50dB以上あれば更に安定したシステムが実現できるとされているので、C/N比が45dB未満の場合を「×」、45dB以上50dB未満の場合を「○」、50dB以上の場合を「◎」とした。
表1〜表3に結果を纏めて示すが、実施例1〜5は何れも初期化後の反射率分布が小さく、45dB以上の高いCN比を有し良好な記録特性であった。また、初期化後の反射率分布についてのTEM観察結果は、図2に示すように、実施例1では小さな結晶粒径が均一に分布したイメージが得られたのに対し、比較例1では小さな結晶粒径と大きな結晶粒径が不均一に混在したイメージが得られ、反射率分布を生む原因となっていることが確認された。
また、比較例1の初期化後のRf信号は実施例1〜5に比べて非常に幅広であり、従って初期化後の反射率が不均一で充分な初期化を行うことが困難であることが分った。
また、比較例1及び2について、実施例1と同様に記録特性の評価も行ったが、比較例1では反射率変動が大きいことが原因で、良好な特性は得られず、比較例2では実施例1に比べ記録材料の結晶化速度が低下してしまい、記録線速度28m/sにおける記録特性で良好な結果を得ることはできなかった。
For each optical disc after initialization, the reflectance distribution and the recording characteristics were evaluated.
The reflectance distribution was evaluated by measuring the signal width of the Rf signal obtained from the optical disc. The recording characteristics were evaluated using an optical disk evaluation apparatus (DDU-1000 manufactured by Pulstec Corp.) having a pickup with a wavelength of 660 nm and NA of 0.65, a recording linear velocity of 28 m / s (equivalent to 8 times the speed of DVD), and a linear density of 0. The evaluation was performed by evaluating the C / N ratio when the 3T single pattern was overwritten 10 times by the EFM + modulation method under the condition of 267 μm / bit. The evaluation criteria are as follows.
Evaluation of reflectance distribution: The reflectance distribution after initialization of DVD + RW (currently shown as Comparative Example 3 in Table 2) that is currently commercially available for 2.4 × speed recording was compared as an approximate reference.
For Example 1 and Comparative Example 1, the state of the recording layer after initialization was observed with a transmission electron microscope (TEM), and the difference in crystal state was also evaluated (see FIG. 2).
Evaluation of recording characteristics: When realizing a rewritable optical disk system, the C / N ratio is required to be at least 45 dB, and if it is 50 dB or more, a more stable system can be realized. The case where the C / N ratio was less than 45 dB was indicated as “×”, the case where it was 45 dB or more and less than 50 dB was indicated as “◯”, and the case where it was 50 dB or more was indicated as “◎”.
The results are summarized in Tables 1 to 3. In each of Examples 1 to 5, the reflectance distribution after initialization was small, the CN ratio was high as 45 dB or more, and the recording characteristics were good. Further, as shown in FIG. 2, the TEM observation result regarding the reflectance distribution after the initialization shows an image in which small crystal grain sizes are uniformly distributed in Example 1, whereas it is small in Comparative Example 1. An image in which the crystal grain size and the large crystal grain size are mixed unevenly was obtained, and it was confirmed that this was the cause of the reflectance distribution.
In addition, the Rf signal after initialization in Comparative Example 1 is very wide as compared with Examples 1 to 5, and therefore, the reflectance after initialization is uneven and it is difficult to perform sufficient initialization. I found out.
In Comparative Examples 1 and 2, the recording characteristics were evaluated in the same manner as in Example 1. However, in Comparative Example 1, good characteristics could not be obtained due to the large variation in reflectance. Compared to Example 1, the crystallization speed of the recording material was lowered, and good results could not be obtained with the recording characteristics at a recording linear velocity of 28 m / s.
1 プラスチック基板
2 第一保護層
3 相変化記録層
4 第二保護層
5 第三保護層
6 金属反射層
7 樹脂保護層
8 貼り合せ用基板
DESCRIPTION OF SYMBOLS 1 Plastic substrate 2 1st protective layer 3 Phase change recording layer 4 2nd protective layer 5 3rd protective layer 6 Metal reflective layer 7 Resin protective layer 8 Substrate for bonding
Claims (6)
(X1)αSbβ(X2)γ
(但し、X1はGa、Ge、Inから選ばれる少なくとも一種の元素、X2はAu、Ag、Cuから選ばれる少なくとも一種の元素、α、β、γは原子%、2≦α≦20、55≦β≦95、0<γ≦10、α+β+γ=100) An optical recording comprising at least a first protective layer, a phase change recording layer, a second protective layer, and a metal reflective layer on a transparent substrate, wherein the phase change recording layer is made of an alloy represented by the following composition formula Medium.
(X 1 ) αSbβ (X 2 ) γ
(Where X 1 is at least one element selected from Ga, Ge and In, X 2 is at least one element selected from Au, Ag and Cu, α, β and γ are atomic%, 2 ≦ α ≦ 20, 55 ≦ β ≦ 95, 0 <γ ≦ 10, α + β + γ = 100)
The optical recording medium according to claim 1, wherein the optimum recording linear velocity is in a range of 28.0 ± 3 m / s.
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PCT/JP2004/016635 WO2005044578A1 (en) | 2003-11-10 | 2004-11-10 | Optical recoding medium and its manufacturing method, sputtering target, usage of optical recording medium, and optical recorder |
US11/429,140 US20060233998A1 (en) | 2003-11-10 | 2006-05-04 | Optical recording medium, method for manufacturing the same, sputtering target, method for using optical recording medium, and optical recording apparatus |
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