JP2006116948A - Write once type optical recording medium - Google Patents
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本発明は、追記型（ＷＯＲＭ：Ｗｒｉｔｅ Ｏｎｃｅ Ｒｅａｄ Ｍａｎｙ）光記録媒体に係り、特に青色レーザ波長領域で高密度の記録が可能な追記型光記録媒体に関する。 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 in a blue laser wavelength region.
青色レーザ波長以下の短波長で記録再生が可能な追記型光記録媒体に関して、超高密度の記録が可能となる青色レーザの開発は急速に進んでおり、それに対応した追記型光記録媒体の開発が行われている。
従来の追記型光記録媒体では、有機材料からなる記録層にレーザ光を照射し、主に有機材料の分解・変質による屈折率変化を生じさせることで記録ピットを形成させており、記録層に用いられる有機材料の光学定数や分解挙動が、良好な記録ピットを形成させるための重要な要素となっている。
従って、青色レーザ対応の追記型光記録媒体の記録層に用いる有機材料としては、青色レーザ波長に対する光学的性質や分解挙動の適切な材料を選択する必要がある。即ち、未記録時の反射率を高め、またレーザの照射によって有機材料が分解し大きな屈折率変化が生じるようにするため（これによって大きな変調度が得られる）、記録再生波長は大きな吸収帯の長波長側の裾に位置するように選択される。何故ならば、有機材料の大きな吸収帯の長波長側の裾は、適度な吸収係数を有し且つ大きな屈折率が得られる波長領域となるためである。
With respect to write-once optical recording media capable of recording and reproducing at short wavelengths below the blue laser wavelength, the development of blue lasers capable of ultra-high-density recording is rapidly progressing, and the development of write-once optical recording media corresponding to it Has been done.
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.
Therefore, it is necessary to select an organic material used for the recording layer of the write-once type optical recording medium compatible with blue laser, which has an appropriate optical property 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.
しかしながら、青色レーザ波長に対する光学的性質が従来並みの値を有する材料は見出されていない。何故ならば、有機材料の吸収帯を青色レーザ波長近傍に持たせるには、分子骨格を小さくするか或いは共役系を短くする必要があるが、そうすると吸収係数の低下、即ち屈折率の低下を招くためである。つまり、青色レーザ波長近傍に吸収帯を持つ有機材料は多数存在し、吸収係数を制御することは可能であるが、大きな屈折率を持たないため、大きな変調度を得ることができないためである。
そこで、無機材料と有機材料を用いたものが検討されている（例えば、本出願人の出願に係る特願２００３−３８５８１０）。また、無機材料のみを用いたものもあり、酸化物を用いたものとして、特許文献１には、Ｂｉ、希土類、Ｇａ、Ｆｅ、Ｏを含む記録層について開示されている。この発明ではガーネットを形成できる組成について述べられている。また、特許文献２には、無機の酸化物を用いた光記録媒体について開示されている。
しかし、これらの従来技術では、記録マークを良好に形成し、良好な特性を得るのに、記録マークをどのような形態にすると効果があるかについては検討されておらず、当然ながら、本発明で問題とした、青色波長の光を用いた場合に大きな変調度を得るための記録マークの形態についても全く検討されていない。
However, no material has been found that has a conventional optical property with respect to the blue laser wavelength. This is because it is necessary to reduce the molecular skeleton or shorten the conjugated system in order to make the absorption band of the organic material near the blue laser wavelength, 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 in the vicinity of the blue laser wavelength, and the absorption coefficient can be controlled, but a large degree of modulation cannot be obtained because it does not have a large refractive index.
Then, the thing using an inorganic material and an organic material is examined (for example, Japanese Patent Application No. 2003-385810 concerning the application of the present applicant). In addition, some use only an inorganic material, and Patent Document 1 discloses a recording layer containing Bi, rare earth, Ga, Fe, and O as an oxide. In this invention, a composition capable of forming a garnet is described. Patent Document 2 discloses an optical recording medium using an inorganic oxide.
However, in these conventional techniques, it has not been studied what form the recording mark is effective for forming the recording mark well and obtaining good characteristics. The form of the recording mark for obtaining a large degree of modulation when using light of blue wavelength, which was a problem in the above, has not been studied at all.
本発明は、青色レーザ波長域以下（５００ｎｍ以下）の短波長で良好な記録再生特性を示す追記型光記録媒体、特に４０５ｎｍ近傍の波長領域で、記録再生を行うことができ、高密度記録可能な追記型光記録媒体の提供を目的とする。 INDUSTRIAL APPLICABILITY The present invention is a write-once type optical recording medium that exhibits good recording / reproducing characteristics at a short wavelength below the blue laser wavelength range (500 nm or less), particularly recording / reproducing can be performed at a wavelength range near 405 nm, and high density recording is possible. An object of the present invention is to provide a write-once type optical recording medium.
上記課題は次の１）〜８）の発明（以下、本発明１〜８という）によって解決される。
１） 記録層が、ＢｉＯｘ（０＜ｘ＜１．５）を含有し、情報が記録された記録マーク部が、Ｂｉの結晶及び／又はＢｉの酸化物の結晶を含むことを特徴とする追記型光記録媒体。
２） 記録マーク部が、Ｂｉの微結晶群及び／又はＢｉの酸化物の微結晶群を含むことを特徴とする１）記載の追記型光記録媒体。
３） 記録層が、Ｂｉ、Ｍ（ＭはＭｇ、Ａｌ、Ｃｒ、Ｍｎ、Ｃｏ、Ｆｅ、Ｃｕ、Ｚｎ、Ｌｉ、Ｓｉ、Ｇｅ、Ｚｒ、Ｔｉ、Ｈｆ、Ｓｎ、Ｍｏ、Ｖ、Ｎｂ、Ｙ、Ｔａのうちの少なくとも一つの元素）及び酸素を含有し、情報が記録された記録マーク部が、記録層に含有される元素の結晶及び／又はそれらの元素の酸化物の結晶を含むことを特徴とする追記型光記録媒体。
４） 記録マーク部が、記録層に含有される元素の微結晶群及び／又はそれらの元素の酸化物の微結晶群を含むことを特徴とする３）記載の追記型光記録媒体。
５） 記録マーク部が４価のＢｉを含むことを特徴とする１）〜４）の何れかに記載の追記型光記録媒体。
６） 記録マーク部では、記録層と隣接層との界面に微小変形を伴うことを特徴とする１）〜５）の何れかに記載の追記型光記録媒体。
７） 記録マーク部では、記録層の体積変化を伴うことを特徴とする１）〜５）の何れかに記載の追記型光記録媒体。
８） 記録マーク部では、未記録部よりも反射率が低いことを特徴とする１）〜７）の何れかに記載の追記型光記録媒体。
The above problems are solved by the following inventions 1) to 8) (hereinafter referred to as the present inventions 1 to 8).
1) Additional note, wherein the recording layer contains BiOx (0 <x <1.5), and the recording mark portion on which information is recorded contains a Bi crystal and / or a Bi oxide crystal. Type optical recording medium.
2) The write-once type optical recording medium according to 1), wherein the recording mark portion includes a Bi crystallite group and / or a Bi oxide microcrystal group.
3) The recording layer is Bi, M (M is Mg, Al, Cr, Mn, Co, Fe, Cu, Zn, Li, Si, Ge, Zr, Ti, Hf, Sn, Mo, V, Nb, Y, The recording mark portion containing at least one element of Ta) and oxygen and having information recorded thereon includes crystals of elements contained in the recording layer and / or crystals of oxides of those elements. A write-once optical recording medium.
4) The write-once type optical recording medium according to 3), wherein the recording mark portion includes a group of microcrystals of elements contained in the recording layer and / or a group of microcrystals of oxides of those elements.
5) The recordable optical recording medium according to any one of 1) to 4), wherein the recording mark portion contains tetravalent Bi.
6) The write-once type optical recording medium according to any one of 1) to 5), wherein the recording mark portion is accompanied by minute deformation at the interface between the recording layer and the adjacent layer.
7) The recordable optical recording medium according to any one of 1) to 5), wherein the recording mark portion is accompanied by a change in volume of the recording layer.
8) The recordable optical recording medium according to any one of 1) to 7), wherein the recording mark portion has a lower reflectance than the unrecorded portion.
以下、上記本発明について詳しく説明する。
青色レーザ波長域以下の短波長で良好な記録が可能な追記型光記録媒体を実現するためには、次の（１）〜（３）が課題となる。
（１）小さな記録マークが形成できる。
（２）記録マーク間の干渉が少ない。
（３）記録マークの安定性が高い。
青色レーザを用いた場合、ＣＤやＤＶＤに用いられる赤外、赤色波長領域のレーザを用いた場合とは異なり、青色波長で良好に記録を行うことが可能な材料を選択する必要がある。
Hereinafter, the present invention will be described in detail.
In order to realize a write-once type optical recording medium capable of good recording at a short wavelength below the blue laser wavelength range, the following (1) to (3) are problems.
(1) A small recording mark can be formed.
(2) There is little interference between recording marks.
(3) The stability of the recording mark is high.
In the case of using a blue laser, it is necessary to select a material capable of performing good recording at a blue wavelength, unlike the case of using an infrared and red wavelength region laser used for CDs and DVDs.
Ｂｉの酸化物は青色波長の光を吸収し易いため良好な記録の実現を期待できる。変調度を大きくするためには、記録マークと未記録部の屈折率差が大きいことが求められるが、本発明１のように、ＢｉＯｘ（０＜ｘ＜１．５）で表わされる材料を記録層に用い、記録マークにＢｉの結晶及び／又はＢｉの酸化物の結晶を形成できるようにすると、屈折率変化が大きくなり大きな変調度を実現できる。例えば未記録部が非晶質である場合、記録マークに結晶部分が含まれていると、より大きな変調度を得ることが可能である。また未記録部が酸化ビスマスからなるとき、記録マークに酸化物ではないＢｉ金属単体が析出するようにすることで更に屈折率の差が大きくなり、より大きな変調度が得られる。非晶質部分を結晶化させて記録マークを形成する方法は従来から行われてきたが、本発明では酸化物に記録する際に、記録された部分が酸化物でなくなること及び結晶化することで、より大きな効果を期待できる。また、異なる結晶構造を持つ結晶が混在することで、結晶の成長を抑えることができるため、２つ以上の異なる結晶構造の結晶からなる記録マークは、大きく成長して広がってしまうことが抑制され、小さい記録マークを形成することができる。 Since Bi oxide easily absorbs light of blue wavelength, it can be expected to realize good recording. In order to increase the degree of modulation, it is required that the difference in refractive index between the recorded mark and the unrecorded portion is large. However, as in the present invention 1, a material represented by BiOx (0 <x <1.5) is recorded. When the layer is used and a Bi crystal and / or a Bi oxide crystal can be formed on the recording mark, the refractive index change increases and a large degree of modulation can be realized. For example, when the unrecorded portion is amorphous, it is possible to obtain a greater degree of modulation if the recording mark includes a crystal portion. Further, when the unrecorded portion is made of bismuth oxide, the difference in refractive index is further increased by making Bi metal, which is not an oxide, precipitate on the recording mark, and a greater degree of modulation can be obtained. A method of forming a recording mark by crystallizing an amorphous part has been conventionally performed. However, in the present invention, when recording on an oxide, the recorded part is not an oxide and is crystallized. And you can expect a bigger effect. In addition, since crystals with different crystal structures can be mixed together, the growth of crystals can be suppressed, so that a recording mark made of two or more crystals with different crystal structures is prevented from growing and spreading. A small recording mark can be formed.
記録により生じる記録層の変化について、もう少し詳しく説明する。
ＢｉＯｘ（０＜ｘ＜１．５）、即ち、Ｂｉでもなく、完全な酸化物であるＢｉ２Ｏ３でもない、化学量論的にみて酸素欠損のＢｉ酸化物は、通常の条件では存在し難い準安定的な状態であるが、光記録媒体の場合には、記録層をスパッタリングで製膜することにより、このような状態を実現することができる。準安定的なＢｉＯｘ（０＜ｘ＜１．５）の状態の記録層に、記録光が照射され温度上昇が起ると、より安定な状態に戻ろうとするため、ＢｉとＢｉの酸化物に分離し易くなる。このとき、Ｂｉの酸化物の中には酸素を遊離し酸化物でなくなってＢｉの状態になるものもあると考えられる。そして、より安定な状態は結晶状態であるため、Ｂｉの結晶とＢｉの酸化物の結晶とが形成される。よって、記録マーク部は、Ｂｉの結晶及び／又はＢｉの酸化物の結晶を含む状態となる。
ＢｉＯｘは光の吸収が大きいので多く存在すると記録感度が向上する。逆にＢｉＯｘが少ないと記録感度が悪くなると共に変調度が低下する。そこで、記録層におけるＢｉＯｘの含有量は、３８〜１００モル％が好ましい。
A change in the recording layer caused by recording will be described in a little more detail.
BiOx (0 <x <1.5) , i.e., neither Bi, a is neither Bi 2 O 3 complete oxide, Bi oxide oxygen deficiency viewed stoichiometrically, exist under normal conditions Although it is a difficult metastable state, in the case of an optical recording medium, such a state can be realized by forming a recording layer by sputtering. When a recording layer is irradiated with a recording light in a metastable BiOx (0 <x <1.5) state and the temperature rises, the recording layer tries to return to a more stable state. It becomes easy to separate. At this time, it is considered that some of the Bi oxides liberate oxygen and become no Bi oxides. Since a more stable state is a crystal state, a Bi crystal and a Bi oxide crystal are formed. Therefore, the recording mark portion includes a Bi crystal and / or a Bi oxide crystal.
Since BiOx absorbs a large amount of light, the presence of a large amount improves recording sensitivity. On the other hand, when BiOx is small, the recording sensitivity deteriorates and the modulation degree decreases. Therefore, the BiOx content in the recording layer is preferably 38 to 100 mol%.
本発明２によると、本発明１の記録原理を使用し、より高密度化が可能な小さいマークの記録が可能となり、かつ、記録マーク部の安定性を高めることができる。
第一に、記録マーク部が、その記録マークの大きさに比べて十分小さいＢｉの微結晶群及び／又はＢｉの酸化物の微結晶群を含むようにすることで、より高密度化を図ることができる（個々の微結晶は記録されるべき記録マークに対して十分小さいため、高密度化に有利である）。
第二に、記録マーク部がＢｉの微結晶群及び／又はＢｉの酸化物の微結晶群を含むようにすることで、記録マークが大きく成長して広がるのを一層抑制でき、記録部の安定性をより一層高めることができる。
According to the present invention 2, by using the recording principle of the present invention 1, it is possible to record a small mark that can be further densified, and to improve the stability of the recording mark portion.
First, the recording mark portion includes a Bi microcrystal group and / or a Bi oxide microcrystal group that are sufficiently smaller than the size of the recording mark, thereby achieving higher density. (Individual microcrystals are sufficiently small with respect to the recording marks to be recorded, which is advantageous for high density).
Secondly, by making the recording mark portion include a Bi crystallite group and / or a Bi oxide microcrystal group, it is possible to further suppress the growth and spread of the recording mark, thereby stabilizing the recording portion. The sex can be further enhanced.
Ｂｉ及び／又はＢｉの酸化物から、それらの微結晶群を効率よく形成させるためには、記録層がＢｉＯｘ（０＜ｘ＜１．５）を含有することが必要である。何故ならば、ＢｉがＢｉ（ｘ＝０）で存在すると、Ｂｉの結晶化が促進され過ぎたり（結晶が大きくなり過ぎる）、Ｂｉが溶融して結晶化しない場合が生じ、Ｂｉの微結晶化が起こりづらくなるためで、逆にＢｉが完全にＢｉＯ１．５で存在すると、記録感度が悪化し易くなり、ＢｉＯｘ（０＜ｘ＜１．５）の場合に比べて、Ｂｉの酸化物の微結晶群が形成され難くなるためである。なお、本発明２でいう微結晶群とは、記録されるべき記録マーク内に、複数のＢｉの微結晶及び／又はＢｉの酸化物の微結晶を含有する状態をいい、微結晶群を形成する個々の微結晶は、記録する変調方式によって決まる最短マーク長よりも小さい。 In order to efficiently form these microcrystal groups from Bi and / or Bi oxides, it is necessary that the recording layer contains BiOx (0 <x <1.5). This is because if Bi is present in Bi (x = 0), crystallization of Bi is promoted too much (crystals become too large), or Bi does not crystallize due to melting. On the other hand, when Bi is completely present at BiO 1.5 , the recording sensitivity is liable to be deteriorated, and compared with the case of BiOx (0 <x <1.5), the oxide of Bi This is because it becomes difficult to form a microcrystal group. The microcrystal group referred to in the present invention 2 refers to a state in which a plurality of Bi microcrystals and / or Bi oxide microcrystals are contained in a recording mark to be recorded. The individual crystallites to be made are smaller than the shortest mark length determined by the modulation method to be recorded.
本発明３では、ＢｉとＭ（ＭはＭｇ、Ａｌ、Ｃｒ、Ｍｎ、Ｃｏ、Ｆｅ、Ｃｕ、Ｚｎ、Ｌｉ、Ｓｉ、Ｇｅ、Ｚｒ、Ｔｉ、Ｈｆ、Ｓｎ、Ｍｏ、Ｖ、Ｎｂ、Ｙ、Ｔａのうちの少なくとも一つの元素）と酸素からなる材料を記録層に含有させることで、青色波長の光に対して良好な記録を行うことができる。未記録状態の結晶構造と記録マークの結晶構造が異なるようにして変調度を得ることは、従来から相変化記録などで行われていた。これに対して本発明３では、２種類以上の酸化物の結晶が混在する状態で記録マークを形成することにより、記録マークと未記録部の屈折率差などがより大きくなり、大きな変調度が得られる。更に、それぞれの酸化物の結晶だけでなく単体元素の結晶を存在させることで、より大きな効果が得られる。また、異なる元素又は結晶構造の結晶が混在することで、結晶の成長を抑えることができるため、２つ以上の異なる元素及び／又は結晶構造の結晶からなる記録マークは、大きく成長して広がってしまうことが抑制され、小さい記録マークを形成することができる。
なお、記録層におけるＢｉとＭと酸素からなる材料の配合割合は３０〜１００モル％とする。３０モル％よりも少ないと、この材料の特性が発揮されにくくなるため好ましくない。また、この材料中のＢｉとＭの割合は、原子比で３：５〜９：１の範囲が好ましく、最も好ましいのは２：１近辺である。Ｂｉの割合が３：５よりも少なくなると、記録感度や変調度向上などのＢｉの酸化物の特性が発揮されにくくなるため好ましくなく、Ｍの割合が９：１よりも少なくなると、２種類以上の酸化物の結晶が混在する状態で記録マークを形成するというＭの添加目的が達成できなくなるため好ましくない。
In the present invention 3, Bi and M (M is Mg, Al, Cr, Mn, Co, Fe, Cu, Zn, Li, Si, Ge, Zr, Ti, Hf, Sn, Mo, V, Nb, Y, Ta When the recording layer contains a material composed of at least one element) and oxygen, good recording can be performed with respect to light having a blue wavelength. Conventionally, obtaining the degree of modulation by making the crystal structure of the unrecorded state different from the crystal structure of the recording mark has been performed in phase change recording or the like. On the other hand, in the present invention 3, by forming the recording mark in a state where two or more kinds of oxide crystals are mixed, the difference in refractive index between the recorded mark and the unrecorded portion becomes larger, and a large modulation degree is obtained. can get. Furthermore, the presence of not only each oxide crystal but also a single element crystal can provide a greater effect. In addition, since the growth of crystals can be suppressed by mixing crystals of different elements or crystal structures, a recording mark composed of crystals of two or more different elements and / or crystal structures grows and spreads greatly. This can suppress the occurrence of a small recording mark.
The mixing ratio of the material composed of Bi, M, and oxygen in the recording layer is 30 to 100 mol%. If it is less than 30 mol%, the properties of this material are hardly exhibited, which is not preferable. The ratio of Bi and M in this material is preferably in the range of 3: 5 to 9: 1 by atomic ratio, and most preferably in the vicinity of 2: 1. If the Bi ratio is less than 3: 5, it is not preferable because the characteristics of Bi oxide such as improvement in recording sensitivity and modulation degree are difficult to be exhibited. If the M ratio is less than 9: 1, two or more types are preferable. This is not preferable because the purpose of adding M, which is to form a recording mark in a state where the oxide crystals are mixed, cannot be achieved.
本発明４によると、本発明３の記録原理を使用し、より高密度化が可能な小さいマークの記録が可能となり、かつ、記録マーク部の安定性を高めることができる。
第一に、記録マーク部が、その記録マークの大きさに比べて十分小さい、記録層に含有される元素の微結晶群及び／又はそれらの元素の酸化物の微結晶群を含むようにすることで、より高密度化を図ることができる（個々の微結晶は、記録されるべき記録マークに対して十分小さいため、高密度化に有利である）。
第二に、記録マーク部が、記録層に含有される元素の微結晶群及び／又はそれらの元素の酸化物の微結晶群を含むようにすることで、記録マークが大きく成長して広がることを一層抑制でき、記録部の安定性をより一層高めることができる。
According to the present invention 4, by using the recording principle of the present invention 3, it is possible to record a small mark that can be further densified, and to improve the stability of the recording mark portion.
First, the recording mark portion includes a microcrystal group of elements contained in the recording layer and / or a microcrystal group of oxides of these elements, which is sufficiently smaller than the size of the recording mark. Thus, higher density can be achieved (since each microcrystal is sufficiently small with respect to the recording mark to be recorded, it is advantageous for higher density).
Second, when the recording mark portion includes a group of microcrystals of elements contained in the recording layer and / or a group of microcrystals of oxides of those elements, the recording mark grows and spreads greatly. Can be further suppressed, and the stability of the recording portion can be further enhanced.
記録層に含有される元素及び／又はそれらの元素の酸化物から、それらの微結晶群を効率良く形成させるためには、記録層中のＢｉ及び／又はＭが形成している酸化物の酸素量が、化学量論組成よりも少ないことが必要である。これは、記録層中に、Ｂｉ単体とＢｉの酸化物が混在して含有されること、及び／又は、Ｍ単体とＭの酸化物が混在して含有されることを意味する。記録層中に、Ｂｉ及び／又はＭが単体で存在すると、Ｂｉ及び／又はＭの結晶化が促進され過ぎたり（結晶が大きくなり過ぎる）、Ｂｉ及び／又はＭが溶融して結晶化しない場合が生じ、Ｂｉの微結晶化及び／又はＭの微結晶化は起こりづらくなる。逆に、記録層中に、Ｂｉ及び／又はＭが完全に酸化物で存在すると、記録感度が悪化し易くなり、Ｂｉの単体とその酸化物及び／又はＭの単体とその酸化物を含有する場合と比較して、Ｂｉの酸化物の微結晶群及び／又はＭの酸化物の微結晶群が形成され難くなる。
なお、本発明４でいう微結晶群とは、記録されるべき記録マーク内に、複数のＢｉの微結晶及び／又はＢｉの酸化物の微結晶、及び／又は、複数のＭの微結晶及び／又はＭの酸化物の微結晶が含有された状態をいい、微結晶群を形成する個々の微結晶は、記録する変調方式によって決まる最短マーク長よりも小さい。
In order to efficiently form the microcrystal group from the elements contained in the recording layer and / or oxides of those elements, oxygen of the oxide formed by Bi and / or M in the recording layer The amount needs to be less than the stoichiometric composition. This means that a single Bi and an oxide of Bi are mixed and / or a single M and an oxide of M are mixed in the recording layer. When Bi and / or M is present alone in the recording layer, crystallization of Bi and / or M is promoted too much (crystals become too large), or Bi and / or M melts and does not crystallize. Thus, Bi microcrystallization and / or M microcrystallization are difficult to occur. On the contrary, when Bi and / or M is completely present in the recording layer, the recording sensitivity is liable to deteriorate, and contains Bi alone and its oxide and / or M alone and its oxide. Compared to the case, it is difficult to form the Bi oxide microcrystal group and / or the M oxide microcrystal group.
The microcrystal group referred to in the present invention 4 refers to a plurality of Bi crystallites and / or Bi oxide crystallites and / or a plurality of M crystallites in a recording mark to be recorded. This refers to a state in which microcrystals of M oxide are contained, and the individual microcrystals forming the microcrystal group are smaller than the shortest mark length determined by the modulation method to be recorded.
本発明５では、記録マークが、４価のＢｉを含むことを特徴とする。通常、Ｂｉの価数は３価が安定な状態であるが、より大きな変調度を得るために４価のＢｉを用いる。Ｂｉ原子の周りの酸素の状態に依存してＢｉの価数を４価にすることができる。価数を変えることにより、物理的な特性が変化するため、大きな変調度を得ることが可能となる。
４価のＢｉの化合物としてはＢｉＯ２が挙げられる。通常、Ｂｉの酸化物はＢｉ２Ｏ３の構造を取るのが安定な状態である。しかし、条件によっては、ＢｉＯ２のような形態も取り得る。このような通常は取らないような結晶構造を持つようにすることで、より大きな変調度を得ることができる。
大きな変調度を得るためには、記録マークと記録マーク以外の未記録部との光の反射率が大きく異なることが必要であり、そのためには、記録マーク部と未記録部の光学特性が大きく異なるようにするとよい。ところで、Ｂｉが４価の化合物になると、３価のＢｉの場合に比べて光学的な特性も大きく変化するから、記録マーク部が４価のＢｉを含むことにより大きな変調度を得ることができる。したがって、記録マーク部は、Ｂｉ２Ｏ３の形で存在する割合が少ない程よいと考えられる。
The fifth aspect of the present invention is characterized in that the recording mark includes tetravalent Bi. Usually, the valence of Bi is stable in the trivalent state, but tetravalent Bi is used to obtain a larger degree of modulation. Depending on the state of oxygen around the Bi atom, the valence of Bi can be made tetravalent. By changing the valence, the physical characteristics change, so that a large degree of modulation can be obtained.
Examples of the tetravalent Bi compound include BiO 2 . In general, it is stable for Bi oxides to have a Bi 2 O 3 structure. However, depending on conditions, a form such as BiO 2 may be taken. By having such a crystal structure that is not normally taken, a greater degree of modulation can be obtained.
In order to obtain a large degree of modulation, it is necessary that the reflectance of light between the recorded mark and the non-recorded portion other than the recorded mark is greatly different. It should be different. By the way, when Bi is a tetravalent compound, the optical characteristics are greatly changed as compared with the case of trivalent Bi. Therefore, when the recording mark portion contains tetravalent Bi, a large degree of modulation can be obtained. . Therefore, it is considered that the smaller the ratio of the recording mark portion existing in the form of Bi 2 O 3 , the better.
例えば、記録前にＢｉの酸化物のみが存在している場合について考えると、Ｂｉ２Ｏ３であるものが、記録後にはＢｉとＢｉＯ２に分かれる。即ち、２Ｂｉ２Ｏ３が、記録後に３ＢｉＯ２＋Ｂｉになると考えられる。したがって、記録前にＢｉの酸化物のみが存在している場合には、記録マーク部の４価のＢｉの割合は、存在する全Ｂｉのうちの３／４程度となる。よって４価のＢｉの存在割合は最大で３／４ということになる。
次に、Ｂｉの酸化物と他の元素の酸化物などが混在する場合について考える。例えば、ＢｉＦｅＯの３元系の化合物の場合を考えてみると、ＢｉとＦｅの割合が３：５〜４：５程度よりもＢｉが多い場合に良好な特性を示す。ここで前述したように、２Ｂｉ２Ｏ３が、記録後に３ＢｉＯ２＋Ｂｉになるとすると、４価のＢｉの存在割合が、ＢｉとＦｅを併せたうちの、９／３２〜１／３程度以上であるときに良好な特性を示すことになる。
以上から、４値のＢｉの割合は、９／３２程度から３／４の範囲が好ましいことになるが、下限値については、あくまで他の元素がＦｅの場合の数値であり、他の元素の種類によって良好な特性を示すＢｉとの割合が変化するので、その値も変化する。
For example, considering the case where only Bi oxide is present before recording, Bi 2 O 3 is separated into Bi and BiO 2 after recording. That is, 2Bi 2 O 3 is considered to be 3BiO 2 + Bi after recording. Therefore, when only Bi oxide is present before recording, the ratio of tetravalent Bi in the recording mark portion is about 3/4 of the total Bi present. Therefore, the ratio of tetravalent Bi is 3/4 at maximum.
Next, a case where a Bi oxide and an oxide of another element are mixed is considered. For example, considering the case of a ternary compound of BiFeO, good characteristics are exhibited when the ratio of Bi to Fe is more than about 3: 5 to 4: 5. As described above, if 2Bi 2 O 3 becomes 3BiO 2 + Bi after recording, the ratio of tetravalent Bi is about 9/32 to 1/3 or more of Bi and Fe. It will show good characteristics at certain times.
From the above, the ratio of Bi of Bi values is preferably in the range of about 9/32 to 3/4, but the lower limit is a numerical value when the other element is Fe to the last, Since the ratio with Bi which shows a favorable characteristic changes with kinds, the value also changes.
本発明６では、ＢｉやＭの結晶及び／又はＢｉやＭの酸化物の結晶を生成させるために、あるいは、ＢｉやＭの微結晶群及び／又はＢｉやＭの酸化物の微結晶群を生成させるために、記録層と隣接層の界面に微小変形を起こさせるという記録原理を特徴とする。
記録層と隣接層の界面に微小変形を起こさせることで、ＢｉやＭの結晶及び／又はＢｉやＭの酸化物の結晶、あるいは、ＢｉやＭの微結晶群及び／又はＢｉやＭの酸化物の微結晶群が生成され易くすることができる。記録層と隣接層界面の微小変形は、記録層や隣接層の膜厚や硬度を調整することで実現することができる。
なお、この記録原理は、記録感度向上にも非常に有効である。
In the present invention 6, Bi or M crystals and / or Bi or M oxide crystals are formed, or Bi or M crystallite groups and / or Bi or M oxide crystallite groups are formed. It is characterized by the recording principle of causing micro deformation at the interface between the recording layer and the adjacent layer in order to produce it.
Bi or M crystal and / or Bi or M oxide crystal, or Bi or M microcrystal group and / or Bi or M oxidation by causing micro deformation at the interface between the recording layer and the adjacent layer. It is possible to facilitate the formation of a group of crystallites. The minute deformation at the interface between the recording layer and the adjacent layer can be realized by adjusting the film thickness and hardness of the recording layer and the adjacent layer.
This recording principle is very effective for improving the recording sensitivity.
本発明７では、ＢｉやＭの結晶及び／又はＢｉやＭの酸化物の結晶を生成させるために、あるいは、ＢｉやＭの微結晶群及び／又はＢｉやＭの酸化物の微結晶群を生成させるために、記録層に体積変化を生じさせるという記録原理を特徴とする。
記録層に体積変化を起こさせることで、ＢｉやＭの結晶及び／又はＢｉやＭの酸化物の結晶、あるいは、ＢｉやＭの微結晶群及び／又はＢｉやＭの酸化物の微結晶群が生成されや易くすることができる。記録層の体積変化は、記録層や隣接層の膜厚や硬度を調整することで実現することができる。
なお、この記録原理は、記録感度向上にも非常に有効である。
In the present invention 7, Bi or M crystals and / or Bi or M oxide crystals are formed, or Bi or M crystallite groups and / or Bi or M oxide crystallite groups are formed. It is characterized by the recording principle of causing a volume change in the recording layer in order to produce it.
Bi or M crystal and / or Bi or M oxide crystal, or Bi or M microcrystal group and / or Bi or M oxide microcrystal group by causing volume change in the recording layer Can be easily generated. The volume change of the recording layer can be realized by adjusting the film thickness and hardness of the recording layer and adjacent layers.
This recording principle is very effective for improving the recording sensitivity.
本発明８のように、記録マーク部では、未記録部よりも反射率が低い（いわゆるＨｉｇｈ ｔｏ Ｌｏｗ記録）構成にすると、高い反射率と高い変調度を両立させた、従来の追記型記録媒体と同一極性の追記型光記録媒体を実現できる。
本発明では、上述のように、ＢｉやＭの結晶及び／又はＢｉやＭの酸化物の結晶、あるいは、ＢｉやＭの微結晶群及び／又はＢｉやＭの酸化物の微結晶群から記録マークが形成されるため、複素屈折率の変化や散乱効果の増大により、容易にＨｉｇｈ ｔｏ Ｌｏｗ記録を実現することができる。
本発明のＨｉｇｈ ｔｏ Ｌｏｗ記録である追記型光記録媒体は、Ｌｏｗ ｔｏ Ｈｉｇｈ記録（記録マーク部の反射率が未記録部の反射率よりも高い）である追記型光記録媒体よりも高い反射率を有するため、多層化に非常に有利となる。但し、本発明の追記型光記録媒体は、記録極性をＨｉｇｈ ｔｏ Ｌｏｗに限定するものではなく、Ｌｏｗ ｔｏ Ｈｉｇｈ記録にも対応することができる。この記録極性を切り替えるには、記録層に隣接する層の数や複素屈折率を制御することで対応することができる。
As in the present invention 8, when the recording mark portion has a lower reflectance than the unrecorded portion (so-called High to Low recording), a conventional write-once recording medium that achieves both a high reflectance and a high degree of modulation. Can be realized.
In the present invention, as described above, recording is performed from a Bi or M crystal and / or a Bi or M oxide crystal, or a Bi or M microcrystal group and / or a Bi or M oxide microcrystal group. Since the mark is formed, High to Low recording can be easily realized by changing the complex refractive index and increasing the scattering effect.
The write-once optical recording medium that is High to Low recording of the present invention has a higher reflectance than the write-once optical recording medium that is Low to High recording (the reflectance of the recording mark portion is higher than the reflectance of the unrecorded portion). Therefore, it is very advantageous for multilayering. However, the write-once type optical recording medium of the present invention does not limit the recording polarity to High to Low, and can cope with Low to High recording. This recording polarity can be switched by controlling the number of layers adjacent to the recording layer and the complex refractive index.
本発明１〜４によれば、小さいマークを高い変調度で安定性良く記録可能な追記型光記録媒体を提供できる。
本発明５〜７によれば、高密度化が可能な小さいマークの記録を可能とし、高い変調度が得られ、マークの安定性も高い追記型光記録媒体を提供できる。
本発明８によれば、高い反射率と高い変調度を両立させた、従来の追記型光記録媒体と同一極性の追記型光記録媒体を提供できる。
According to the first to fourth aspects of the present invention, it is possible to provide a write-once type optical recording medium capable of recording a small mark with a high degree of modulation with high stability.
According to the fifth to seventh aspects of the present invention, it is possible to provide a write-once type optical recording medium that enables recording of small marks that can be densified, provides a high degree of modulation, and has high mark stability.
According to the eighth aspect of the present invention, it is possible to provide a write-once optical recording medium having the same polarity as that of a conventional write-once optical recording medium that achieves both high reflectance and high modulation.
以下、本発明を実施例により更に具体的に説明するが、本発明はこれらの実施例により限定されるものではない。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
実施例１
Ｂｉ２Ｏ３とＦｅ２Ｏ３の２：１の混合物を焼結して作成した直径７６．２ｍｍのターゲットを用い、ＲＦ電力１００Ｗ、Ａｒガス流量４０ｓｃｃｍの条件下で、カーボン基板上にＢｉ、Ｆｅ、Ｏからなる膜厚２０ｎｍの層を成膜した。
この膜の組成をＨＲ−ＲＢＳ（Ｈｉｇｈ Ｒｅｓｏｌｕｔｉｏｎ Ｒｕｔｈｅｒｆｏｒｄ Ｂａｃｋｓｃａｔｔｅｒｉｎｇ Ｓｐｅｃｔｒｏｍｅｔｒｙ）により分析した。即ち、ビームエネルギー４５０ｋｅＶのＨｅイオンを上記サンプル面の法線に対し４２．５度の角度で照射し、散乱角度９５度に散乱されたＨｅイオンを磁場型検出器により検出した。その結果を図１に示す。
膜厚範囲４〜１０ｎｍの領域で、各元素の組成を求めると、Ｂｉは３３．３±０．５（原子％）、Ｆｅは１２．５±０．８（原子％）、Ｏは５４．２±３．０（原子％）であり、本来（Ｂｉ＋Ｆｅ）：Ｏ＝２：３である状態に対し、本サンプルでは酸素が欠損していることが確認できた（但し、スパッタされた膜の組成比は、成膜条件に大きく左右されるため、Ｂｉ２Ｏ３とＦｅ２Ｏ３の２：１の混合物を焼結して作成したターゲットで成膜した膜が、必ず酸素欠損することを意味するものではない）。また、特にスパッタ初期の膜では（膜厚範囲１０〜２０ｎｍ）、より酸素が欠損した状態であることが分かる。しかし、このＨＲ−ＲＢＳの測定結果では、ＢｉとＦｅのどちらが酸素欠損を起こしているのか特定できない。
そこで、Ｘ線光電子分光法（ＸＰＳ）による分析を行なった。ＸＰＳによる分析条件は、下記の通りである。
＜ＸＰＳ分析条件＞
・測定装置 ： ＡＸＩＳ−ＵＬＴＲＡ（Ｋｒａｔｏｓ社製）
・Ｘ線源 ： Ａｌモノクロメータ使用
・Ｘ線パワー ： ４０Ｗ
・測定領域 ： １１０μφ
・測定核 ： Ｂｉ＿４ｆ
・エネルギー分解能： ｗｉｄｅ ｓｃａｎ（ワイドスキャン）＝１．０ｅＶ
ｎａｒｒｏｗ ｓｃａｎ（ナロースキャン）＝０．１ｅＶ
・入射角 ： ４５°
・取り出し角 ： ９０°
各成分に対するｎａｒｒｏｗ ｓｃａｎの測定結果を図２に示したが、図２（ａ）から、ＢｉはＢｉ０（金属ビスマス）と酸化物の混合物であることが分る。また、図２（ｂ）から、Ｆｅは酸化物として存在している（金属としては存在しない）ことが分かる。
Example 1
Using a target with a diameter of 76.2 mm prepared by sintering a 2: 1 mixture of Bi 2 O 3 and Fe 2 O 3 , Bi, on a carbon substrate under the conditions of RF power of 100 W and Ar gas flow rate of 40 sccm, A 20 nm thick layer made of Fe and O was formed.
The composition of this film was analyzed by HR-RBS (High Resolution Rutherford Backscattering Spectrometry). That is, He ions having a beam energy of 450 keV were irradiated at an angle of 42.5 degrees with respect to the normal line of the sample surface, and He ions scattered at a scattering angle of 95 degrees were detected by a magnetic field type detector. The result is shown in FIG.
When the composition of each element is determined in the film thickness range of 4 to 10 nm, Bi is 33.3 ± 0.5 (atomic%), Fe is 12.5 ± 0.8 (atomic%), O is 54. It was 2 ± 3.0 (atomic%), and it was confirmed that oxygen was deficient in this sample compared to the original (Bi + Fe): O = 2: 3 (however, in the sputtered film) Since the composition ratio greatly depends on the film forming conditions, it is confirmed that a film formed with a target prepared by sintering a 2: 1 mixture of Bi 2 O 3 and Fe 2 O 3 is always oxygen deficient. Does not mean). Further, it can be seen that oxygen is more deficient particularly in the film at the initial stage of sputtering (film thickness range: 10 to 20 nm). However, this HR-RBS measurement result cannot identify which of Bi and Fe is causing an oxygen deficiency.
Therefore, analysis by X-ray photoelectron spectroscopy (XPS) was performed. Analysis conditions by XPS are as follows.
<XPS analysis conditions>
Measurement device: AXIS-ULTRA (manufactured by Kratos)
・ X-ray source: Al monochromator used ・ X-ray power: 40W
・ Measurement area: 110μφ
・ Measurement nucleus: Bi_4f
Energy resolution: wide scan (wide scan) = 1.0 eV
narrow scan = 0.1 eV
-Incident angle: 45 °
・ Take-off angle: 90 °
FIG. 2 shows the measurement results of narrow scan for each component. From FIG. 2A, it can be seen that Bi is a mixture of Bi 0 (metal bismuth) and oxide. Further, FIG. 2B shows that Fe exists as an oxide (but does not exist as a metal).
一般に、分析サンプルが空気に触れる時間を可能な限り短くしても、表面に膜厚１ｎｍ程度の空気酸化層が見られるケースが多いので、Ｂｉ０とＢｉＯの定量を確認するため、深さ方向分析をＢｉ＿４ｆについて実施した（図３参照）。
Ｂｉ＿４ｆの深さ方向分析において、表面の空気酸化層の影響を調べるため、０．１ｎｍ程度のエッチングステップの設定を用いた。
図３から得られたＢｉ０とＢｉＯの比を図４に纏めた（定量にはＢｉ＿４ｆ ７／２を使用した）。表面近傍にＢｉＯが偏在している可能性もあるが、図４の結果から、ＢｉＯが多く存在する領域の厚さが１２Å（１．２ｎｍ）程度であることから、空気酸化の影響である可能性が高いと考えられる。そこで、厚さ１．２ｎｍ程度までの表面酸化の領域を除いた部分を平均して、ＢｉとＢｉＯの割合を求めたところ、Ｂｉ０が５７％、ＢｉＯが４３％の比で存在していることが分かった。また、Ｆｅは殆ど酸素欠損していないと判断できた。つまり、実施例で作成したＢｉ、Ｆｅ、Ｏからなる膜において、この膜がＢｉＯｘを含有し、かつ０＜ｘ＜１．５を満足することが確認できた。
In general, even if the time for which the analysis sample is exposed to air is as short as possible, an air oxide layer with a film thickness of about 1 nm is often seen on the surface, so in order to confirm the quantification of Bi 0 and BiO, the depth direction Analysis was performed on Bi_4f (see FIG. 3).
In the depth direction analysis of Bi_4f, an etching step setting of about 0.1 nm was used in order to investigate the influence of the air oxide layer on the surface.
The ratio of Bi 0 and BiO obtained from FIG. 3 is summarized in FIG. 4 (Bi_4f 7/2 was used for quantification). Although there is a possibility that BiO is unevenly distributed in the vicinity of the surface, the result of FIG. 4 shows that the thickness of the region where a large amount of BiO exists is about 12 mm (1.2 nm), which may be due to the effect of air oxidation. It is considered that the nature is high. Therefore, when the ratio of Bi and BiO was obtained by averaging the portions excluding the surface oxidation region up to about 1.2 nm in thickness, Bi 0 was present in a ratio of 57% and BiO in a ratio of 43%. I understood that. Moreover, it could be judged that Fe had almost no oxygen deficiency. That is, it was confirmed that the film made of Bi, Fe, and O prepared in the example contains BiOx and satisfies 0 <x <1.5.
次いで、案内溝（溝深さ２１ｎｍ、トラックピッチ０．４３μｍ）を有する厚さ０．６ｍｍのポリカーボネート基板上に、スパッタ法により、上記Ｂｉ、Ｆｅ、Ｏからなる膜を７ｎｍの膜厚で設け、更にその上に、膜厚９６ｎｍのＺｎＳ−ＳｉＯ２層、膜厚１００ｎｍの銀合金反射層、紫外線硬化型樹脂からなる膜厚が約５μｍの保護層を設け、本発明の追記型光記録媒体を作成した。
上記光記録媒体に対し、パルステック工業（株）製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、以下の条件で記録を行った。
・変調方式 ： １−７変調
・記録線密度 ： 最短マーク長（２Ｔ）＝０．２０４（μｍ）
・記録線速度 ： ６．６１（ｍ／ｓ）
その結果、連続記録部において、記録パワー６．８ｍＷでジッタ５．２％という良好な値（リミットイコライザ使用）が得られ、かつ変調度（Ｍｏｄｕｌａｔｅｄ ａｍｐｌｉｔｕｄｅ）６２％を有する、記録極性がＨｉｇｈ ｔｏ Ｌｏｗである良好な記録再生特性を実現することができた。また、ＨＤ ＤＶＤ−Ｒ規格に準拠した評価では（基板のトラックピッチを０．４０μｍとした）、ＰＲＳＮＲ＝２７、ＳｂＥＲ＝１×１０−８が得られ、非常に良好な記録再生特性を実現することができた。なお、ＰＲＳＮＲは、Ｐａｒｔｉａｌ Ｒｅｓｐｏｎｓｅ Ｓｉｇｎａｌ ｔｏ Ｎｏｉｚｅ Ｒａｔｉｏ（パーシャル・レスポンス・シグナル・ツー・ノイズ・レシオ）の略で、ＨＤ ＤＶＤ規格における信号品質を表す指標である。また、ＳｂＥＲは、Ｓｉｍｕｌａｔｅｄ ｂｉｔ Ｅｒｒｏｒ Ｒａｔｅ（シミュレイテッド・ビット・エラー・レイト）の略であり、ＨＤ ＤＶＤ規格におけるエラーレートを示す値である。
Next, on the polycarbonate substrate having a thickness of 0.6 mm having a guide groove (groove depth of 21 nm, track pitch of 0.43 μm), a film made of Bi, Fe, and O is provided with a thickness of 7 nm by sputtering. further thereon, ZnS-SiO 2 layer having a thickness of 96 nm, the silver alloy reflective layer with a thickness of 100 nm, the film thickness made of ultraviolet curable resin is a protective layer of about 5 [mu] m, a write-once optical recording medium of the present invention Created.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
Modulation method: 1-7 modulation Recording linear density: Shortest mark length (2T) = 0.204 (μm)
Recording linear velocity: 6.61 (m / s)
As a result, in the continuous recording portion, a good value (using a limit equalizer) of 5.2% jitter is obtained at a recording power of 6.8 mW, and the recording polarity is High to Low having a modulation degree (Modulated Amplitude) of 62%. It was possible to realize the good recording / reproducing characteristics. Further, in the evaluation based on the HD DVD-R standard (the substrate track pitch is 0.40 μm), PRSNR = 27 and SbER = 1 × 10 −8 are obtained, and very good recording / reproduction characteristics are realized. I was able to. PRSNR is an abbreviation for Partial Response Signal to Noise Ratio (Partial Response Signal to Noise Ratio), and is an index representing signal quality in the HD DVD standard. SbER is an abbreviation for Simulated Bit Error Rate, and is a value indicating an error rate in the HD DVD standard.
次いで、上記追記型光記録媒体における記録マーク部がどのような形態で形成されているかを確認する実験を行なった。
まず、上記光記録媒体の銀合金反射層をＨＮＯ３（濃度２４％）で取り除き、そのサンプルを更にＴＨＦ（テトラヒドロフラン）溶液に浸して基板を溶かし、記録層をマイクログリッド上に掬い取った。このサンプルを日本電子製の透過型電子顕微鏡（ＴＥＭ）ＪＥＭ−２０１０を用いて観察した。
その結果は図５に示すとおりで、記録マーク部が何らかの結晶群により形成されている可能性が確認できた。
そこで、上記ＴＥＭ観察サンプルの電子線回折像を観察した（回折パターンの観察には、制限視野電子線回折法を用いた）。
その結果、図５のＴＥＭ像における黒い部分から得られた電子線回折パターンは金属ビスマスの結晶による指数付けができ、記録マークがＢｉの結晶（結晶群）から構成されていることが確認できた。
なお、本追記型光記録媒体では、Ｂｉの結晶以外にも、酸化ビスマス、鉄、酸化鉄の結晶も存在する可能性があるが、結晶粒が非常に小さいため、Ｂｉの結晶以外を特定するに至らなかった。
このように、本発明の追記型光記録媒体では、微小なＢｉの結晶や結晶群から記録マーク部が形成されるため、非常に細かな記録マークが、高い精度で形成できるものと考えられる。
Next, an experiment was conducted to confirm in what form the recording mark portion of the write-once type optical recording medium was formed.
First, the silver alloy reflective layer of the optical recording medium was removed with HNO 3 (concentration 24%), the sample was further immersed in a THF (tetrahydrofuran) solution to dissolve the substrate, and the recording layer was scraped onto a microgrid. This sample was observed using a JEM-2010 transmission electron microscope (TEM) manufactured by JEOL.
The result is as shown in FIG. 5, and it was confirmed that the recording mark portion was formed of some crystal group.
Therefore, an electron diffraction image of the TEM observation sample was observed (a limited-field electron diffraction method was used to observe the diffraction pattern).
As a result, the electron diffraction pattern obtained from the black portion in the TEM image of FIG. 5 can be indexed with a metal bismuth crystal, and it was confirmed that the recording mark was composed of Bi crystals (crystal group). .
In this write-once type optical recording medium, there may be crystals of bismuth oxide, iron, and iron oxide in addition to Bi crystals, but since the crystal grains are very small, other than Bi crystals are specified. It did not lead to.
As described above, in the write-once type optical recording medium of the present invention, since the recording mark portion is formed from a fine Bi crystal or crystal group, it is considered that a very fine recording mark can be formed with high accuracy.
実施例２
本発明の追記型光記録媒体では、記録層に含有されるＢｉやＭ、及びＢｉやＭの酸化物を、記録によって効率よく結晶化又は微結晶群化させるために、記録層と隣接層の界面に微小変形を伴わせるか、あるいは記録層に体積変化を伴わせることができる。
そこで、実施例１で作成した追記型光記録媒体の記録部の断面を、日本電子製ＴＥＭ ＪＥＭ−２０１０を用いて観察した。
図６は、実施例１で作成した追記型光記録媒体を、ＦＩＢ（Ｆｏｃｕｓｅｄ ｉｏｎ ｂｅａｍ）を用いて案内溝方向に切断したサンプルのＴＥＭ像であり、（ａ）は未記録部、（ｂ）と（ｃ）は記録部である。図から分かるように、（ａ）は変形がない状態であるが、（ｂ）（ｃ）では、変形や体積変化を起している。なお、図６のサンプルは有限な厚さを有しており、実施例１で作成した追記型光記録媒体の案内溝部と溝間部を同時に観察してしまうため、二重に見えている。
図７は、実施例１で作成した追記型光記録媒体を、ＦＩＢを用いて半径方向に切断したサンプルのＴＥＭ像であり、（ａ）は記録部、（ｂ）は未記録部である。図から分かるように、（ｂ）は変形がない状態であるが、（ａ）では、変形や体積変化を起している。
この図６〜図７の結果から、本発明の追記型光記録媒体では、記録層（Ｂｉ、Ｆｅ、Ｏからなる層、以下、ＢｉＦｅＯと略す）と隣接層の界面に微小変形を伴い、また、ＢｉＦｅＯに体積変化が伴うことが確認できた。
なお、本発明では、記録層と隣接層界面の微小変形、あるいは記録層の体積変化は必ずしも必要でないが、記録特性の改善には有効である。
Example 2
In the write-once type optical recording medium of the present invention, Bi and M, and Bi and M oxides contained in the recording layer can be efficiently crystallized or formed into a microcrystal group by recording. The interface can be accompanied by minute deformation, or the recording layer can be accompanied by a volume change.
Then, the cross section of the recording part of the write-once type optical recording medium created in Example 1 was observed using TEM JEM-2010 manufactured by JEOL.
FIG. 6 is a TEM image of a sample obtained by cutting the write-once optical recording medium created in Example 1 in the direction of a guide groove using an FIB (Focused Ion Beam). (A) is an unrecorded portion, (b) And (c) are recording units. As can be seen from the figure, (a) shows no deformation, but (b) and (c) cause deformation and volume change. The sample in FIG. 6 has a finite thickness and looks double because the guide groove portion and the groove portion of the write-once type optical recording medium prepared in Example 1 are observed simultaneously.
FIG. 7 is a TEM image of a sample obtained by cutting the write-once optical recording medium created in Example 1 in the radial direction using FIB, where (a) is a recorded portion and (b) is an unrecorded portion. As can be seen from the figure, (b) shows no deformation, but (a) causes deformation and volume change.
From the results of FIGS. 6 to 7, in the write-once type optical recording medium of the present invention, the interface between the recording layer (a layer made of Bi, Fe, and O, hereinafter abbreviated as BiFeO) and the adjacent layer is slightly deformed. It was confirmed that BiFeO was accompanied by a volume change.
In the present invention, micro deformation of the interface between the recording layer and the adjacent layer or volume change of the recording layer is not necessarily required, but it is effective for improving the recording characteristics.
比較例１
案内溝（溝深さ２１ｎｍ、トラックピッチ０．４３μｍ）を有する厚さ０．６ｍｍのポリカーボネート基板上に、スパッタ法によりＢｉ（金属ビスマス、ＢｉＯｘ表記ではｘ＝０に相当する）膜を１０ｎｍの膜厚で設け、更にその上に、膜厚８０ｎｍのＺｎＳ−ＳｉＯ２層、膜厚１００ｎｍの銀合金反射層、紫外線硬化型樹脂からなる膜厚が約５μｍの保護層を設け、本比較例１の追記型光記録媒体を作成した。
上記光記録媒体に対し、パルステック工業（株）製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、以下の条件で記録を行った。
・変調方式 ： １−７変調
・記録線密度 ： 最短マーク長（２Ｔ）＝０．２０４（μｍ）
・記録線速度 ： ６．６１（ｍ／ｓ）
その結果、記録パワー１１．８ｍＷのとき、リミットイコライザ使用によるジッタ値が１２．０％となった（本発明の記録媒体に比べ、かなり悪い値となっている）。
なお、本比較例の追記型光記録媒体は、低記録パワー時は記録極性がＬｏｗ ｔｏ Ｈｉｇｈであり、記録パワーが高まると記録極性がＨｉｇｈ ｔｏ Ｌｏｗとなる特異な特性を示した。この追記型光記録媒体の記録マーク部を実施例１と同様にＴＥＭで観察した結果、図８に示すような結果が得られ、Ｂｉの結晶らしき黒点は観測されたが、Ｂｉの溶融によると思われる相分離のような形態を示す記録マークとなっていることが分かった。
この記録マーク部は明らかに図５とは異なり、記録マーク間のクロストークが大きく、位置精度の低い記録マークしか形成されないことが明らかになった。
以上の結果から、ＢｉＯｘを含有する記録層でｘ＝０は好ましくないことが確認できた。
この事実は、
・Ｂｉ単独では、熱伝導率が高く、微小な記録マーク形成には不向きである
・Ｂｉ単独では、容易に溶融が起きてしまい、記録マーク形成には不向きである
ことを意味しており、Ｂｉを、Ｂｉの酸化物、元素Ｍ（例えばＦｅ）、元素Ｍの酸化物（例えばＦｅＯ）等の低熱伝導率材料から構成されるマトリックス材料中に分散させることが重要と言える。
Comparative Example 1
A Bi (metal bismuth, corresponding to x = 0 in BiOx notation) film of 10 nm is formed on a polycarbonate substrate having a thickness of 0.6 mm having guide grooves (groove depth 21 nm, track pitch 0.43 μm) by sputtering. Provided with a thickness, and further provided thereon is a ZnS-SiO 2 layer having a thickness of 80 nm, a silver alloy reflective layer having a thickness of 100 nm, and a protective layer having a thickness of about 5 μm made of an ultraviolet curable resin. A write-once optical recording medium was created.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
Modulation method: 1-7 modulation Recording linear density: Shortest mark length (2T) = 0.204 (μm)
Recording linear velocity: 6.61 (m / s)
As a result, when the recording power was 11.8 mW, the jitter value due to the use of the limit equalizer was 12.0% (a considerably worse value than the recording medium of the present invention).
The write-once type optical recording medium of this comparative example exhibited a unique characteristic that the recording polarity was Low to High when the recording power was low and the recording polarity was High to Low when the recording power was increased. As a result of observing the recording mark portion of this write-once type optical recording medium with TEM in the same manner as in Example 1, the result shown in FIG. 8 was obtained, and a black spot like Bi crystal was observed. It was found that the recording mark showed a form like a possible phase separation.
This recording mark portion is clearly different from that shown in FIG. 5, and it has become clear that only the recording mark with low positional accuracy is formed due to the large crosstalk between the recording marks.
From the above results, it was confirmed that x = 0 was not preferable in the recording layer containing BiOx.
This fact
Bi alone has a high thermal conductivity and is not suitable for forming minute recording marks. Bi alone means that melting occurs easily and is not suitable for forming recording marks. Can be dispersed in a matrix material composed of a low thermal conductivity material such as Bi oxide, element M (for example, Fe), and oxide of element M (for example, FeO).
比較例２
案内溝（溝深さ２１ｎｍ、トラックピッチ０．４３μｍ）を有する厚さ０．６ｍｍのポリカーボネート基板上に、組成がＢｉ２Ｏ３の直径７６．２ｍｍのターゲットを用い、ＲＦ電力１００Ｗ、Ａｒガス流量４０ｓｃｃｍの条件下で、ＢｉＯｘ層を７ｎｍの膜厚で設けた。なお、この際、スパッタ膜のＢｉＯｘが化学量論組成となるように、過剰の酸素を導入した（酸素流量１０ｓｃｃｍ）。したがって、本比較例ではＢｉＯｘ層の組成は、ＢｉＯ１．５となっている。
更にＢｉＯ１．５層上に、膜厚９６ｎｍのＺｎＳ−ＳｉＯ２層、膜厚１００ｎｍの銀合金反射層、紫外線硬化型樹脂からなる膜厚が約５μｍの保護層を設け、本発明２の追記型光記録媒体を作成した。
上記光記録媒体に対し、パルステック工業（株）製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、以下の条件で記録を行った。
・変調方式 ： １−７変調
・記録線密度 ： 最短マーク長（２Ｔ）＝０．２０４（μｍ）
・記録線速度 ： ６．６１（ｍ／ｓ）
その結果、リミットイコライザ使用によるジッタ値が５．１％と非常に良好な値が得られたが、記録パワーが９．０ｍＷを超えた（酸素導入なしの場合は６．２ｍＷ）。なお、記録極性は、Ｈｉｇｈ ｔｏ Ｌｏｗであった。
以上の結果から、酸化ビスマスの酸素欠損量が完全になくなると記録感度が大きく劣化することが確認できた。したがって、本発明の追記型光記録媒体においては、ＢｉＯｘを含有する記録層でｘ＝１．５とすることは好ましくないことが確認できた。
Comparative Example 2
On a polycarbonate substrate with a thickness of 0.6 mm having guide grooves (groove depth of 21 nm, track pitch of 0.43 μm), a target having a composition of Bi 2 O 3 with a diameter of 76.2 mm was used, RF power 100 W, Ar gas flow rate A BiOx layer was provided with a thickness of 7 nm under the condition of 40 sccm. At this time, excess oxygen was introduced so that BiOx of the sputtered film had a stoichiometric composition (oxygen flow rate 10 sccm). Therefore, in this comparative example, the composition of the BiOx layer is BiO 1.5 .
More BiO 1.5 layer on, ZnS-SiO 2 layer having a thickness of 96 nm, the silver alloy reflective layer with a thickness of 100 nm, the film thickness made of ultraviolet curing resin protective layer of about 5μm provided, additional recording of the present invention 2 Type optical recording medium was prepared.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
Modulation method: 1-7 modulation Recording linear density: Shortest mark length (2T) = 0.204 (μm)
Recording linear velocity: 6.61 (m / s)
As a result, a very good jitter value of 5.1% was obtained by using a limit equalizer, but the recording power exceeded 9.0 mW (6.2 mW when oxygen was not introduced). The recording polarity was High to Low.
From the above results, it was confirmed that the recording sensitivity was greatly deteriorated when the amount of oxygen deficiency of bismuth oxide was completely eliminated. Therefore, in the write-once type optical recording medium of the present invention, it was confirmed that x = 1.5 was not preferable in the recording layer containing BiOx.
実施例３
案内溝（溝深さ２１ｎｍ）を有するポリカーボネート基板上に、スパッタ法によりＢｉＯｘ（０＜ｘ＜１．５）で表わされる組成の膜を１０ｎｍの膜厚で設け、本発明の追記型光記録媒体を作成した。この膜の成膜は、組成がＢｉ２Ｏ３の直径７６．２ｍｍのターゲットを用い、ＲＦ電力１００Ｗ、Ａｒガス流量４０ｓｃｃｍで行った。なお、実施例１と同様に、ＨＲ−ＲＢＳ、及びＸＰＳを使用してＢｉＯｘで表される膜のｘを調べた結果、０＜ｘ＜１．５であることを確認した。
上記光記録媒体に対し、パルステック工業（株）製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、以下の条件で記録を行った。
・変調方式 ： １−７変調
・記録線密度 ： 最短マーク長（２Ｔ）＝０．２３１（μｍ）
・記録線速度 ： ６．０（ｍ／ｓ）
・波形等化 ： ノーマルイコライザー
その結果、連続記録部において、記録パワー５．２ｍＷで９．９％という良好なジッタ値が得られ、かつ、変調度５５％を有する良好な二値記録特性を実現することができた。なお、記録極性は、Ｈｉｇｈ ｔｏ Ｌｏｗであった。
Example 3
A write-once optical recording medium of the present invention is formed by providing a film having a composition represented by BiOx (0 <x <1.5) with a thickness of 10 nm on a polycarbonate substrate having a guide groove (groove depth of 21 nm) by sputtering. It was created. This film was formed by using a target having a composition of Bi 2 O 3 and a diameter of 76.2 mm at an RF power of 100 W and an Ar gas flow rate of 40 sccm. As in Example 1, x of the film represented by BiOx was examined using HR-RBS and XPS, and it was confirmed that 0 <x <1.5.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
Modulation method: 1-7 modulation Recording linear density: Shortest mark length (2T) = 0.231 (μm)
・ Recording linear velocity: 6.0 (m / s)
・ Waveform equalization: Normal equalizer As a result, a good jitter value of 9.9% can be obtained at a recording power of 5.2 mW in a continuous recording section, and a good binary recording characteristic with a modulation factor of 55% is realized. We were able to. The recording polarity was High to Low.
実施例４
実施例１で作成し記録を行った追記型光記録媒体を用いて反射ＥＥＬＳ測定を行った。測定装置は、Ｐｅｒｋｉｎ−Ｅｌｍｅｒ社製、ＰＨＩ４３００改走査型オージェ電子分光装置を用いた。ＥＥＬＳはＥｌｅｃｔｒｏｎ Ｅｎａｇｙ Ｌｏｓｓ Ｓｐｅｃｔｒｏｓｃｏｐｙのことで電子エネルギー損失分光といわれる測定である。電子を測定試料に入射し、試料表面層との相互作用により散乱された電子のエネルギー分布を測定する方法である。あるエネルギーの一次電子が、測定したい原子の内殻を励起し、あるエネルギーの電子の放出が起きる。そのとき、一次電子の散乱がおきるが、近傍の原子などの影響を受け、エネルギー損失が起こるので、その散乱のされ方を調べることにより近傍の原子の動径分布関数などの情報を得ることができる。
ＥＥＬＳ測定で得られたＥＥＬＳスペクトルより、Ｏ（酸素）原子周辺の動径分布関数を測定した。動径分布関数は、近傍における原子の存在確率を表しており、原子の価数、構造などを推測することが可能である。光電子多重散乱理論を用いた解析ソフトのうち、ワシントン大学が発行しているＦＥＦＦが広く利用されている。この解析ソフトを用いて実際の測定値と照合することにより原子の価数、構造が推測可能となる。
図９は、このような方法で測定した動径分布関数の測定値であり、図１０はＦＥＦＦを用いて計算した動径分布関数である。Ｂｉが取り得ると考えられるＢｉ３価の場合、Ｂｉ３価であるが、β−Ｂｉ２Ｏ３構造の場合、Ｂｉ４価のＢｉＯ２の場合について示した。
これらを比較すると、特徴的なのは記録部の６Å付近のピーク１０１１、１０１２である。両図面を比較すると、この１０１１と１０１２のピークが一致しており、記録部には、つまり記録マークには、ＢｉＯ２即ち４価のＢｉが存在していることが明らかである。
そして、このような記録マークを持つ追記型光記録媒体は大きな変調度を有する良好な記録が可能であり、高密度記録を実現できる。
Example 4
Reflective EELS measurement was performed using the write-once type optical recording medium prepared and recorded in Example 1. The measuring device used was a Perkin-Elmer PHI4300 modified scanning Auger electron spectrometer. EELS is a measurement called Electron Energy Loss Spectroscopy called Electron Energy Loss Spectroscopy. In this method, electrons are incident on a measurement sample, and the energy distribution of the electrons scattered by the interaction with the sample surface layer is measured. A primary electron of a certain energy excites the inner shell of the atom to be measured, and an electron of a certain energy is emitted. At that time, scattering of primary electrons occurs, but energy loss occurs due to the influence of nearby atoms, etc., so it is possible to obtain information such as the radial distribution function of nearby atoms by investigating how it is scattered. it can.
From the EELS spectrum obtained by the EELS measurement, the radial distribution function around the O (oxygen) atom was measured. The radial distribution function represents the existence probability of atoms in the vicinity and can estimate the valence, structure, etc. of the atoms. Of the analysis software using the photoelectron multiple scattering theory, FEFF issued by the University of Washington is widely used. By using this analysis software and collating with actual measured values, the valence and structure of the atoms can be estimated.
FIG. 9 shows measured values of the radial distribution function measured by such a method, and FIG. 10 shows the radial distribution function calculated using FEFF. In the case of Bi trivalent, which Bi can take, it is Bi trivalent, but in the case of the β-Bi 2 O 3 structure, the case of Bi tetravalent BiO 2 is shown.
When these are compared, the characteristic is peaks 1011 and 1012 in the vicinity of 6 mm of the recording portion. Comparing the two drawings, the peaks of 1011 and 1012 coincide with each other, and it is clear that BiO 2 , that is, tetravalent Bi exists in the recording portion, that is, the recording mark.
A write-once optical recording medium having such a recording mark can perform good recording with a large degree of modulation, and can realize high-density recording.
１０１１：ＢｉＯ２（４価のＢｉ）を示すピーク（実測）
１０１２：ＢｉＯ２（４価のＢｉ）を示すピーク（計算）
1011: Peak indicating BiO 2 (tetravalent Bi) (actual measurement)
1012: Peak showing BiO 2 (tetravalent Bi) (calculation)
Claims (8)
8. The write-once type optical recording medium according to claim 1, wherein the recording mark portion has a lower reflectance than the unrecorded portion.
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| JP2005259331A JP4627704B2 (en) | 2004-09-21 | 2005-09-07 | Write-once optical recording medium |
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| WO2006129565A1 (en) * | 2005-05-30 | 2006-12-07 | Pioneer Corporation | Resist material, and resist material for electron beam recording |
| WO2008016126A1 (en) * | 2006-08-01 | 2008-02-07 | Ricoh Company, Ltd. | Recordable optical recording medium and recording method thereof |
| JP2008116990A (en) * | 2005-05-30 | 2008-05-22 | Pioneer Electronic Corp | Resist material, and resist material for electron beam recording |
| JP2008116989A (en) * | 2005-05-30 | 2008-05-22 | Pioneer Electronic Corp | Resist material, and resist material for electron beam recording |
| WO2008123620A1 (en) * | 2007-04-02 | 2008-10-16 | Ricoh Company, Ltd. | Worm optical recording medium |
| JP2008276900A (en) * | 2007-04-02 | 2008-11-13 | Ricoh Co Ltd | Write once optical recording medium |
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| US7592058B2 (en) * | 2006-01-31 | 2009-09-22 | Tdk Corporation | Optical recording medium |
| JP2010111048A (en) * | 2008-11-07 | 2010-05-20 | Ricoh Co Ltd | Write-once type optical recording medium |
| US8124211B2 (en) | 2007-03-28 | 2012-02-28 | Ricoh Company, Ltd. | Optical recording medium, sputtering target, and method for manufacturing the same |
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