JP4125566B2 - Multi-layer phase change optical information recording medium and recording / reproducing method thereof - Google Patents

Description

【００３１】
実施例２
本実施例に用いた熱拡散層のターゲットは、酸化亜鉛を主体とし、表２の「ドープ元素Ａ」欄に示す元素が「Ａ／（Ｚｎ＋Ａ）」欄に示す原子比で添加されている。これらのターゲットを熱拡散層に用いた点以外は、実施例１と同様にして、サンプル２−１〜２−９の２層相変化型光ディスクを作成した。
作成された各サンプルに対して実施例１と同条件で記録を行い、第１情報層、第２情報層のジッター、及び１０００回オーバーライト後の第１情報層、第２情報層のジッターを測定した。
サンプル１−１と比較すると、Ｂ、Ａｌ、Ｇａ、Ｉｎを、０．０１〜０．１の範囲の原子比で添加することによって、１０００回書き換え後のジッターが低下し、オーバーライト特性が向上することが分った。サンプル２−８は、Ａｌの添加量が０．００５であり、Ａｌが含まれていないサンプル１−１とジッター値も同程度であり、Ａｌ添加による効果は見られなかった。反対に、サンプル２−９は、Ａｌの添加量は０．２であり、光透過率も低下し、第１情報層のオーバーライト特性も低下した。しかし、比較例であるサンプル１−２〜１−４と比べると透過率は大きく、１０００回繰り返し記録後のジッター値も大きいながらも測定可能であったから、熱拡散層に酸化亜鉛を主成分とする材料を用いたことによる本発明の効果は得られていると考えられる。
以上の結果から、ドープ元素Ａの割合は０．０１≦Ａ／（Ｚｎ＋Ａ）≦０．１の範囲が好ましいことが分る。
また、その他の試作実験からも、第１情報層の記録層の膜厚が３〜１５ｎｍ、反射層の膜厚が３〜２０ｎｍ、熱拡散層の膜厚が２０〜２００ｎｍの範囲であると、第１情報層、第２情報層ともに良好な記録再生ができ、また、第２情報層を良好に記録再生するためには、第１情報層の光透過率が４０％以上必要であることが確認された。
【００３２】
【表２】

【００３３】
実施例３
本実施例に用いた熱拡散層のターゲットは、酸化亜鉛を主体とし、Ａｌ及び、Ｃｒ又はＶが含まれており、Ａｌは、原子比においてＡｌ／（Ｚｎ＋Ａｌ＋Ｘ）＝０．０５（Ｘ：Ｃｒ、Ｖ）の割合で含まれている。Ｃｒ又はＶの含有量（原子比）は、表３の「Ｘ／（Ｚｎ＋Ａｌ＋Ｘ）」欄に示す通りである。
これらのターゲットを熱拡散層に用いた点以外は、実施例１と同様にしてサンプル３−１〜３−６の２層相変化型光ディスクを作成した。
作成された各サンプルに対して実施例１と同条件で記録を行い、第１情報層、第２情報層のジッターを測定した。更に保存信頼性を調べるため、初期記録した各サンプルを８０℃８５％ＲＨで３００時間保存した後、初期記録マークの３Ｔ再生信号のジッターを測定した。
各サンプルの測定結果を表３に示す。Ｃｒ又はＶを０．００５〜０．０５の範囲の原子比で添加したサンプル３−１〜３−４、及びＶを０．１添加したサンプル３−５は、無添加のサンプル３−６に比べて、第１情報層の保存後のジッター値が小さく、光ディスクとして優れていることが分った。しかし、サンプル３−５は、光透過率が低下し、第２情報層のジッター値が増大している。以上の結果から、ドープ元素Ｘの割合は、０．００５≦Ｘ／（Ｚｎ＋Ａ＋Ｘ）≦０．０５の範囲が好ましいことが分る。
【００３４】
【表３】

【００３５】
実施例４
第１反射層にＡｇを用い、第１上部保護層と第１反射層との間に第１バリア層として膜厚３ｎｍのＳｉＣを設けた点以外は、実施例２のサンプル２−２と同様にして、実施例であるサンプル４−１の２層相変化型光ディスクを作成した。
また、バリア層を設けない点以外は、サンプル４−１と同様にして、比較例であるサンプル４−２を作成した。
作成された各サンプルに対して実施例１と同条件で記録を行い、第１情報層、第２情報層のジッターを測定した。更に保存信頼性を調べるため、初期記録した各サンプルを８０℃８５％ＲＨで３００時間保存した後、初期記録マークの３Ｔ再生信号のジッターを測定した。結果は表４に示すとおりであり、第１反射層にＡｇを用いた場合、バリア層を設けたサンプルは、保存後のジッターも良好で、光ディスクとして優れていることが分った。
【００３６】
【表４】

【００３７】
実施例５
直径１２ｃｍ、厚さ１．１ｍｍで表面に連続溝によるトラッキングガイド用の凹凸を持つポリカーボネート樹脂からなる第２基板上に、Ａｌ−Ｔｉからなる厚さ１２０ｎｍの第２反射層、ＺｎＳ・ＳｉＯ_２からなる厚さ２０ｎｍの第２上部保護層、Ｇｅ_４Ａｇ_１Ｉｎ_３Ｓｂ_７０Ｔｅ_２２からなる厚さ１２ｎｍの第２記録層、ＺｎＳ・ＳｉＯ_２からなる厚さ１３０ｎｍの第２下部保護層の順にＡｒガス雰囲気中のスパッタ法により製膜し、第２情報層を形成した。
この第２情報層上に、樹脂を塗布し、２Ｐ（ｐｈｏｔｏ ｐｏｌｙｍｅｒｉｚａｔｉｏｎ）法によって、連続溝によるトラッキングガイド用の凹凸を持つ中間層を形成した。中間層の厚さは３０μｍとした。
更にその上に、サンプル２−２と同様のターゲットを用いて厚さ１２０ｎｍの第１熱拡散層を設け、Ａｇ−Ｐｄ−Ｃｕからなる厚さ１０ｎｍの第１反射層、ＺｎＳ・ＳｉＯ_２からなる厚さ１５ｎｍの第１上部保護層、Ｇｅ_４Ａｇ_１Ｉｎ_３Ｓｂ_７０Ｔｅ_２２からなる厚さ６ｎｍの第１記録層、ＺｎＳ・ＳｉＯ_２からなる厚さ１２０ｎｍの第１下部保護層の順にＡｒガス雰囲気中のスパッタ法で製膜し、第１情報層を形成した。熱拡散層に関しては、ＡｒとＯ_２の混合ガスをスパッタガスとし、電気伝導率、光透過率が大きくなるＡｒガスとＯ_２ガスの比で成膜を行なった。
更に第１情報層膜面上に、直径１２ｃｍ、厚さ５０μｍのポリカーボネートフィルムからなる第１基板を、４５μｍの厚さの両面粘着シートからなる透明層を介して貼り合わせ、２層相変化型光ディスクを作成した。
また、これとは別に、光透過率測定用として、厚さ１．１ｍｍの基板に第１情報層と透明層、第１基板を同様に設け、第１基板側からの光透過率を測定した。
本実施例の光ディスクの、第１情報層の初期化前の光透過率は、波長４０５ｎｍで４８％、波長８１０ｎｍで４５％、波長１０６０ｎｍで２０％であった。
【００３８】
次に、本実施例の２層相変化型光ディスクに対して、２つのレーザーを持つ２層媒体用初期化装置を用いて、初期化を行なった。本実施例で用いた初期化装置の構成を図８に模式的に示す。この初期化装置は、半導体レーザーと対物レンズから構成される光ヘッドが、２つ設けられている。２つの光ヘッドは、それぞれ波長１０６０ｎｍ及び８１０ｎｍの発光がなされる半導体レーザーとフォーカシング機能を持つ光学系装置とを組み合わせて構成されている。スピンドルモータによって光ディスクを回転させながら、内周から外周へ２つの光ヘッドが移動し（図の矢印の方向）初期化を行なう。
本実施例では、第１情報層に対して波長１０６０ｎｍのレーザーを、第２情報層に対して波長８１０ｎｍのレーザーを用い、線速度３ｍ／ｓｅｃ、光ヘッドの外周への送りピッチ３５μｍ／回転で初期化を行なった。
また、光透過率測定用のディスクも同様に、波長１０６０ｎｍで初期化した後、４０５ｎｍでの光透過率を測定したところ、５１％であった。
初期化された２層光ディスクの各情報層の信号をオシロスコープで観察した。ＲＦ信号は、各層とも変動が少なく良好であった。これは、第１情報層に本発明の熱拡散層を用いたことで、波長１０６０ｎｍでの光透過率が小さくなり、第１情報層は、波長１０６０ｎｍのレーザーでフォーカスが外れることなく、効率よく初期化できたことによると考えられる。また、反対に波長８１０ｎｍでの第１情報層の光透過率が大きいために、第２情報層を波長８１０ｎｍのレーザーで初期化するときの光量損失が少なく、効率よく初期化できたことによると考えられる。
【００３９】
上記のようにして作成したそれぞれの媒体について次の条件で記録を行った。
レーザー波長：４０５ｎｍ
ＮＡ：０．８５
線速：６．５ｍ／ｓ
トラックピッチ：０．３２μｍ
線密度０．１６μｍ／ｂｉｔでの第１情報層、第２情報層のジッター、及び、１０００回オーバーライト後の第１情報層、第２情報層のジッターを測定したところ、第１情報層、第２情報層ともに良好に記録再生を行なうことができた。
また、その他の試作実験からも、ＮＡ＝０．８５のピックアップで記録再生を行なう場合に、第２情報層を良好に記録再生するためには、第１情報層の光透過率が４０％以上必要であることが確認された。
以上のことから、本発明の光ディスクは、記録再生を行なう対物レンズの開口数ＮＡが変化した場合でも、第１基板の厚さを１０〜６００μｍの範囲で調整することによって、良好に記録再生を行なうことが出来る。また、本発明の光ディスクは、確実にかつ良好に初期化できることが分った。
【００４０】
【発明の効果】
本発明１によれば、オーバーライト特性の優れた多層相変化型光情報記録媒体を提供できる。
本発明２によれば、更に保存信頼性の優れた多層相変化型光情報記録媒体を提供できる。
本発明３〜７によれば、それぞれの層の反射率、記録感度及び光透過率（第Ｎ層をのぞく）を、記録、消去、再生条件に合わせて最適化することができ、全情報層の記録再生特性が優れた多層相変化型光情報記録媒体を提供できる。
本発明８によれば、中間層によって、第１情報層と第２情報層とを光学的に分離することができ、多種類の波長光源を持つ初期化装置を使って、２層の情報層共に良好な初期化が可能な多層相変化型光情報記録媒体を提供できる。
本発明９によれば、第１情報層、第２情報層共に感度がよく、記録再生特性の優れた多層相変化型光情報記録媒体を提供できる。
本発明１０によれば、第１基板の厚さが薄い場合でも容易に製造可能な多層相変化型光情報記録媒体を提供できる。
本発明１１によれば、反射層の腐食が抑えられ保存信頼性に優れた多層相変化型光情報記録媒体を提供できる。
本発明１２によれば、対物レンズの開口数ＮＡが変化した場合でも、良好に記録・再生を行なうことが可能な多層相変化型光情報記録媒体を提供できる。
本発明１３によれば、本発明１〜１２の多層相変化型光情報記録媒体を用いて大容量の記録再生を行なうことができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る２層相変化型光情報記録媒体の概略断面図。
【図２】本発明の他の実施形態に係る２層相変化型光情報記録媒体の概略断面図。
【図３】酸化亜鉛に対するＡｌのドープ量を変化させて成膜した、厚さ２００ｎｍの膜の光透過率の波長依存性を示す図。
【図４】成膜工程、初期化工程、密着工程からなる方法で製造した２層相変化型光情報記録媒体の概略断面図。
【図５】第１成膜工程、中間層形成工程、第２成膜工程、基板貼り合わせ工程、及び初期化工程からなる方法で製造した２層相変化型光情報記録媒体の概略断面図。
【図６】本発明に係る３つの情報層を有する相変化型光情報記録媒体を示す図。
【図７】本発明に係る他の３つの情報層を有する相変化型光情報記録媒体を示す図。
【図８】実施例５で用いた初期化装置の構成を模式的に示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer phase change optical information recording medium in which information is recorded and reproduced by light such as a laser, and a recording and reproducing method thereof.
[0002]
[Prior art]
A phase-change optical disk (phase-change optical information recording medium) such as a CD-RW is generally provided with a recording layer made of a phase-change material on a plastic substrate, on which a light absorption of the recording layer is absorbed. In this structure, a reflection layer having a thermal diffusion effect is formed and the basic structure is used. Information is recorded and reproduced by entering laser light from the substrate surface side.
Phase change materials change between a crystalline state and an amorphous state by heating with laser light irradiation and subsequent cooling, become amorphous when rapidly cooled after rapid heating, and crystallize when slowly cooled. The phase change optical information recording medium applies this property to information recording and reproduction.
In order to prevent oxidation, transpiration, or deformation of the recording layer caused by heating due to light irradiation, a lower protective layer (also referred to as a lower dielectric layer), and a recording layer and a reflection layer are usually provided between the substrate and the recording layer. An upper protective layer (also referred to as an upper dielectric layer) is provided between the layers. Further, these protective layers have a function of adjusting the optical properties of the recording medium by adjusting the thickness thereof, and the lower protective layer softens the substrate by heat during recording on the recording layer. It also has a function to prevent this.
[0003]
In recent years, as the amount of information handled by computers and the like has increased, the signal recording capacity of optical disks such as DVD-RAM and DVD + RW has increased, and the density of signal information has been increasing. The current CD recording capacity is about 650 MB, and the DVD is about 4.7 GB, but it is expected that the demand for higher recording density will increase in the future.
As a method for increasing the recording density using such a phase change optical information recording medium, for example, the laser wavelength used is shortened to the blue light region, or the aperture of an objective lens used for a pickup for recording / reproducing is used. It has been proposed to increase the number NA to reduce the spot size of the laser light irradiated onto the optical recording medium.
In order to improve the recording capacity by improving the information recording medium itself, it is created by stacking at least two information layers consisting of a recording layer and a reflective layer on one side of the substrate, and bonding these information layers with an ultraviolet curable resin or the like. For example, Japanese Patent No. 2702905, Japanese Patent Application Laid-Open No. 2000-215516, Japanese Patent Application Laid-Open No. 2000-222777, and Japanese Patent Application Laid-Open No. 2001-243655 have been proposed.
[0004]
The separation layer (referred to as an intermediate layer in the present invention), which is an adhesive portion between the information layers, has a function of optically separating the two information layers, and the laser beam used for recording and reproduction is as far as possible from the information layer. Therefore, it is made of a material that absorbs as little light as possible.
Each of these two-layer phase change optical information recording media has a characteristic part in the first information layer. Similar to the case of the single-layer phase change optical information recording medium, the first protective layer and the second protective layer are provided. A layer is provided.
The two-layer phase change optical information recording medium has been announced at academic societies as described in, for example, “ODS2001 Technical Digest P22”, but many problems still exist.
For example, if the laser beam is not sufficiently transmitted through the information layer (first information layer) on the near side when viewed from the laser beam irradiation side, information is recorded on the recording layer of the information layer (second information layer) on the back side. Since it cannot be recorded or reproduced, it can be considered that the reflective layer constituting the first information layer is eliminated or made extremely thin, or the recording layer constituting the first information layer is made extremely thin.
[0005]
Recording with a phase change optical information recording medium is performed by irradiating the phase change material of the recording layer with laser light and rapidly cooling it to change the crystal to amorphous to form a mark. If it is eliminated or the thickness is very thin, such as about 10 nm, the thermal diffusion effect becomes small, and it becomes difficult to form an amorphous mark.
In particular, an Sb—Te eutectic recording material, which is one of materials generally used in phase-change optical information recording media such as CD-RW, is compared with a Ge—Sb—Te compound recording material. Since the erasure ratio is excellent and the sensitivity is high, it is known that the outline of the amorphous portion of the recording mark is clear.
However, since the Sb—Te eutectic recording material has a higher crystallization speed than the Ge—Sb—Te compound recording material, it needs to be rapidly cooled in a single hour to become amorphous. In other words, it is a material that needs to have a rapid cooling structure, and it is difficult to form a mark with a thin reflective layer.
[0006]
A method of providing a layer (referred to as a thermal diffusion layer) that assists the thermal diffusion function that the reflective layer has used on the reflective layer using nitride, carbide, or the like that has a relatively large thermal conductivity and a small light absorption rate. Japanese Patent Laid-Open No. 8-50739 relating to a single-layer phase change optical information recording medium and Japanese Patent Laid-Open No. 2000-222777 relating to a two-layer phase change optical information recording medium have been proposed. This is considered to be an effective method for solving the above-mentioned drawbacks that occur when the reflective layer constituting the thin film is thinned.
However, these materials such as nitrides and carbides have a large stress, so that the formed thermal diffusion layer is likely to crack, and as a result, an optical disk provided with the thermal diffusion layer cannot provide sufficient overwrite characteristics. There is a problem.
Also, when initializing a two-layer phase change disk, the initialization process takes twice as much time as a single-layer optical disk, and the efficiency is significantly reduced.
In order to solve this problem, Japanese Patent Application Laid-Open No. 9-91700 proposes a method for simultaneously initializing a plurality of recording layers by using a plurality of laser light sources and an initialization apparatus for the method. However, when a plurality of recording layers are initialized using a light source having the same wavelength, the recording layer located on the near side initializes the recording layer on the back side unless the laser beam is transmitted to some extent at the initialization wavelength. It is not possible. In such a case, it is difficult to focus the recording layer on the near side, and in-plane variation occurs in the reflectance after initialization, or the transmitted light may affect the crystallization state of the recording layer on the back side. There is sex.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a multilayer phase change type optical information recording medium that has excellent overwrite characteristics and can reliably initialize a plurality of recording layers even when the reflective layer in the information layer is thin, and a method for recording and reproducing the same. To do.
[0008]
[Means for Solving the Problems]
As a result of intensive studies in order to solve the problems of the prior art, the present inventors have found the following multilayer phase change type optical information recording medium and its recording / reproducing method.
That is, the above-mentioned problems are as follows: 13 ) Invention (hereinafter referred to as the present invention 1) 13 It is solved by.
1) An optical information recording medium in which an information layer having a recording layer capable of recording information by causing a phase change between a crystalline state and an amorphous state by incidence of light is provided (N: an integer of 2 or more). When each of the information layers is a first information layer, a second information layer,... An Nth information layer as viewed from the light incident side, at least one information layer other than the Nth information layer is , A lower protective layer, a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer. The heat diffusion layer is composed mainly of zinc oxide. And A (= one selected from B, Al, Ga, and In) in an atomic ratio of 0.01 ≦ A / (Zn + A) ≦ 0.1 A multilayer phase change optical information recording medium characterized by:
2 ) The thermal diffusion layer further contains X (= Cr or V) in an atomic ratio of 0.005 ≦ X / (Zn + A + X) ≦ 0.05. 1) The multilayer phase change optical information recording medium described.
3 1) The thickness of the heat diffusion layer is 20 to 200 nm. Or 2) The multilayer phase change optical information recording medium described.
4 ) The recording layer in the information layer having the thermal diffusion layer is mainly composed of Sb and Te, Ag, In, Ge, Se, Sn, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga , Bi, Si, Dy, Pd, Pt, Au, S, B, C, and at least one of P, 1) to 3 The multilayer phase change optical information recording medium according to any one of the above.
5 The thickness of the recording layer in the information layer having the thermal diffusion layer is 3 to 15 nm. 4 The multilayer phase change optical information recording medium according to any one of the above.
6 The reflective layer in the information layer having the thermal diffusion layer is mainly composed of at least one of Au, Ag, Cu, W, Al, Ta 1) to 5 The multilayer phase change optical information recording medium according to any one of the above.
7 The thickness of the reflective layer in the information layer having the heat diffusion layer is 3 to 20 nm. 6 The multilayer phase change optical information recording medium according to any one of the above.
8 A multilayer phase change optical information recording medium capable of recording / reproducing information, in which two information layers are provided between the first substrate and the second substrate, and an intermediate layer is provided between the two information layers. The first information layer includes a first lower protective layer, a first recording layer, a first upper protective layer, a first reflective layer, and a first thermal diffusion layer, and the second information layer includes a second lower protective layer. A first substrate, a first lower protective layer, a first recording layer, a first recording layer, a second recording layer, a second upper protective layer, and a second reflective layer. 1. An upper protective layer, a first reflective layer, a first thermal diffusion layer, an intermediate layer, a second lower protective layer, a second recording layer, a second upper protective layer, a second reflective layer, and a second substrate are laminated in this order. 1) ~ 7 The multilayer phase change optical information recording medium according to any one of the above.
9 ) The light transmittance of the first information layer is 40 to 70% with respect to light having a wavelength of 350 to 700 nm. 8 The multilayer phase change optical information recording medium described in the above.
10 ) A transparent layer is provided between the first substrate and the first lower protective layer. 8 Or 9 The multilayer phase change optical information recording medium described in the above.
11 ) A barrier layer is provided between the first upper protective layer and the first reflective layer and / or between the second upper protective layer and the second reflective layer. 8 ) ~ 10 The multilayer phase change optical information recording medium according to any one of the above.
12 ) The thickness of the first substrate is 10 to 600 μm 8 ) ~ 11 The multilayer phase change optical information recording medium according to any one of the above.
13 1) ~ 12 The information recording / reproducing is performed by making a light beam having a wavelength of 350 to 450 nm incident on each information layer of the multilayer phase change optical information recording medium according to any one of the above) from the first information layer side A recording / reproducing method for a multilayer phase change optical information recording medium.
[0009]
Hereinafter, the present invention will be described in detail.
In the present invention, an information layer of N layers (N: an integer of 2 or more) is provided on a substrate, and the information layer is made of a material that changes phase between a crystalline state and an amorphous state by light irradiation. And a multilayer phase change optical information recording medium capable of recording / reproducing information, wherein an intermediate layer is provided between the information layers, on the side on which recording / reproducing light is incident In view of this, at least one information layer other than the information layer formed at the innermost side is composed of a lower protective layer, a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer in order, and the heat diffusion layer is oxidized. It is characterized by containing zinc as a main component. Here, the main component means to occupy 50% by weight or more of the whole.
For the lower protective layer, the recording layer made of a phase change recording material, the upper protective layer, and the reflective layer, conventionally known techniques can be applied, but the multilayer phase change optical information recording medium of the present invention is characterized. Is that the above-mentioned problems of the present invention are solved by using a specific material for the thermal diffusion layer.
[0010]
Here, among the plurality of information layers, the information layer formed at the innermost side when viewed from the light incident side does not need to transmit light, and therefore the reflective layer can be thickened, so there is no need to provide a heat diffusion layer. . Further, when a heat diffusion layer is provided in the innermost information layer, it is not necessary to use a material mainly composed of zinc oxide as described above as a material constituting the heat diffusion layer.
As a material for the reflective layer, an Ag-based material has heretofore been known as a preferable material for a multilayer phase change optical information recording medium. This is because, for example, as described in ISOM 2001 Technical Digest P202, the refractive index n is as small as 0.5 or less even in the blue wavelength region, and light absorption can be suppressed to a low level.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The multilayer phase change optical information recording medium according to the present invention will be described in detail below.
FIG. 1 is a schematic cross-sectional view of a two-layer phase change optical information recording medium according to an embodiment of the present invention. The first information layer 1, the intermediate layer 4, the second information layer 2, and the second substrate 5 are sequentially stacked on the first substrate 3.
The first information layer 1 includes a first lower protective layer 11, a first recording layer 12, a first upper protective layer 13, a first reflective layer 14, and a first thermal diffusion layer 15, and the second information layer 2 includes 2 comprises a lower protective layer 21, a second recording layer 22, a second upper protective layer 23, and a second reflective layer 24. In addition, the 1st information layer 1 and the 2nd information layer 2 of this invention are not limited to the said layer structure at all.
FIG. 2 is a schematic cross-sectional view of a two-layer phase change optical information recording medium according to another embodiment of the present invention. As shown in the figure, the first upper protective layer 13, the first reflective layer 14, The first barrier layer 16 and the second barrier layer 25 may be provided between the second upper protective layer 23 and the second reflective layer 24.
Further, the transparent layer 6 may be provided between the first substrate 3 and the first lower protective layer 11. Such a transparent layer 6 is provided when a thin sheet-like material is used for the first substrate 3 and the manufacturing method is different from that of the optical information recording medium of FIG.
[0012]
The first substrate 3 needs to transmit light to be irradiated for recording / reproduction, and those conventionally known in the technical field are used.
As the material, glass, ceramics, resin and the like are usually used, and resin is particularly preferable in terms of moldability and cost.
Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Acrylic resins such as polycarbonate resin and polymethyl methacrylate (PMMA), which are excellent in terms of moldability, optical characteristics, and cost, are preferable.
On the surface of the first substrate 3 on which the film is to be formed, a spiral or concentric groove for tracking laser light is formed as necessary, and a concave / convex pattern, usually called a groove portion and a land portion, is formed. Such a groove is usually formed by an injection molding method or a photopolymer method.
The thickness of the first substrate 3 is preferably about 10 to 600 μm.
As the material of the second substrate 5, the same material as that of the first substrate 3 may be used, but a material opaque to the recording / reproducing light may be used. May be different. The thickness of the second substrate 5 is not particularly limited, but it is preferable to select a thickness such that the total thickness with the first substrate is 1.2 mm.
[0013]
The intermediate layer 4 and the transparent layer 6 preferably have low light absorption at the wavelength of light irradiated for recording and reproduction, and the material is preferably a resin in terms of moldability and cost, and an ultraviolet curable resin, A slow-acting resin, a thermoplastic resin, or the like can be used.
On the second substrate 5 and the intermediate layer 4, similarly to the first substrate 3, uneven patterns such as grooves and guide grooves may be formed by injection molding or a photopolymer method.
The intermediate layer 4 is a layer for enabling the pickup to distinguish between the first information layer and the second information layer and optically separate them during recording and reproduction, and the thickness is preferably 10 to 50 μm. . If it is thinner than 10 μm, interlayer crosstalk occurs, and if it is thicker than 50 μm, spherical aberration occurs during recording / reproduction of the second recording layer, and recording / reproduction tends to be difficult. Although the thickness of the transparent layer 6 is not particularly limited, the optimum thickness of the first substrate 3 of the optical information recording medium prepared by the manufacturing method without the transparent layer 6 as shown in FIG. It is necessary to adjust the thicknesses of the first substrate 3 and the transparent layer 6 so that the total thickness of the substrate 3 and the transparent layer 6 of the optical information recording medium is approximately the same.
For example, assuming that NA = 0.85 and good recording / erasing performance is obtained when the thickness of the first substrate 3 of the optical information recording medium of FIG. 1 is 100 μm, the optical information of FIG. If the thickness of the first substrate 3 of the recording medium is 50 μm, the thickness of the transparent layer is preferably 50 μm.
[0014]
The material of the first recording layer 12 and the second recording layer 22 is not particularly limited as long as it is a material that changes phase between crystal and amorphous by heating and cooling by light irradiation, and is conventionally known in the technical field. What is being applied applies.
For example, chalcogen alloys such as Ge—Te, Ge—Te—Sb, Ge—Sn—Te, and Sb—Te eutectic materials may be mentioned. Sb—Te eutectic materials are particularly preferred in terms of speed and erase ratio.
For these recording layer materials, Ag, In, Ge, Se, Sn, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Other elements and impurities such as Bi, Si, Dy, Pd, Pt, Au, S, B, C, and P can be added.
These recording layers can be formed by various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition, etc. Excellent film quality. In the sputtering method, film formation is generally performed while flowing an inert gas such as argon. At this time, reactive sputtering may be performed while oxygen, nitrogen, or the like is mixed.
The thickness of the first recording layer 12 is not particularly limited, but is preferably 3 to 15 nm. If it is less than 3 nm, it tends to be difficult to form a uniform film. If it is thicker than 15 nm, the light transmittance tends to decrease, such being undesirable.
The thickness of the second recording layer 22 is also not particularly limited, but is preferably 3 to 20 nm. If it is less than 3 nm, it tends to be difficult to form a uniform film, and if it is thicker than 20 nm, the recording sensitivity tends to decrease, such being undesirable.
[0015]
The first reflective layer 14 and the second reflective layer 24 have functions such as using incident light efficiently and improving the cooling rate to make it easy to become amorphous. For example, Au, Ag, Cu, W, Al, Ta, or an alloy thereof can be used. Further, Cr, Ti, Si, Pd, Ta, Nd, Zn or the like is used as an additive element.
Among these, Ag-based materials have a low refractive index even in the blue wavelength region, and n is 0.5 or less, so that light absorption can be suppressed. Therefore, the reflective layer of the multilayer optical information recording medium as in the present invention, particularly the first It is preferable as a material used for the reflective layer of the information layer.
The manufacturing method of the reflective layer is the same as that of the recording layer.
Since the first information layer 1 requires high light transmittance, the first reflective layer 14 is preferably made of Ag or an alloy thereof having a low refractive index and high thermal conductivity, and the thickness is It is preferable that it is about 3-20 nm. If the thickness is less than 3 nm, it becomes difficult to form a dense film having a uniform thickness. If it is thicker than 20 nm, the light transmittance decreases, and recording / reproduction of the second information layer 2 becomes difficult.
The second reflective layer 24 constituting the second information layer 2 has a thickness of 50 to 200 nm, preferably 80 to 150 nm. If it is less than 50 nm, the repetitive recording characteristics are deteriorated, and if it is more than 200 nm, the sensitivity tends to be lowered.
[0016]
The functions and materials of the first lower protective layer 11, the second lower protective layer 21, the first upper protective layer 13, and the second upper protective layer 23 are the same as in the case of the single-layer phase change optical information recording medium. The first recording layer 12 and the second recording layer 22 have functions such as preventing deterioration and deterioration, increasing adhesive strength, and improving recording characteristics.
As the material, SiO, SiO ₂ ZnO, SnO ₂ , Al ₂ O ₃ TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂ Metal oxide such as Si; ₃ N ₄ Nitrides such as AlN, TiN, ZrN; ZnS, In ₂ S ₃ , TaS ₄ Sulfides such as SiC, TaC, B ₄ Carbides such as C, WC, TiC and ZrC; diamond-like carbon; or a mixture thereof.
These materials can be used alone as a protective layer, but may also be a mixture of each other. Moreover, you may contain an impurity as needed.
The melting point of the protective layer needs to be higher than that of the recording layer. Specifically, ZnS and SiO ₂ It is believed that the mixture with is most preferred.
The manufacturing method of the protective layer is the same as that of the recording layer.
[0017]
The thicknesses of the first lower protective layer 11 and the second lower protective layer 21 are preferably 60 to 200 nm, respectively. If it is less than 60 nm, the first substrate or the intermediate layer may be deformed by heat during recording. When it is thicker than 200 nm, there is a tendency that a problem arises in mass productivity. In these ranges, the film thickness is designed so as to obtain an optimum reflectance.
Moreover, it is preferable that the film thicknesses of the first upper protective layer 13 and the second upper protective layer 23 are 3 to 40 nm, respectively. When the thickness is less than 3 nm, the recording sensitivity is lowered, and when it is thicker than 40 nm, the heat dissipation effect tends to be not obtained.
[0018]
In the multilayer phase change optical information recording medium of the present invention, barrier layers 16 and 25 may be provided between the upper protective layer and the reflective layer. As described above, the reflective layer is made of an Ag alloy, and the protective layer is made of ZnS and SiO. ₂ However, when these two layers are adjacent to each other, sulfur in the protective layer may corrode Ag in the reflective layer, which may reduce storage reliability. In order to eliminate this problem, it is preferable to provide a barrier layer when Ag-based is used for the reflective layer. The barrier layer does not contain sulfur and must have a melting point higher than that of the recording layer. Specifically, SiO, ZnO, SnO ₂ , Al ₂ O ₃ TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂ Oxides such as Si; ₃ N ₄ Nitrides such as AlN, TiN, ZrN; ZnS, In ₂ S ₃ , TaS ₄ Sulfides such as SiC, TaC, B ₄ Carbides such as C, WC, TiC, ZrC; or a mixture thereof.
These barrier layers are desired to have a low absorptance at the laser wavelength.
The manufacturing method of the barrier layer is the same as that of the recording layer.
The thickness of the barrier layer is preferably 2 to 10 nm. If it is less than 2 nm, the effect of preventing corrosion of Ag cannot be obtained, and the storage reliability is lowered. When it is thicker than 10 nm, there is a tendency that the heat dissipation effect cannot be obtained.
[0019]
The first thermal diffusion layer 15 is desired to have a high thermal conductivity in order to rapidly cool the recording layer irradiated with the laser. It is also desirable that the absorption rate at the laser wavelength is small so that the information layer on the back side can be recorded and reproduced.
The thermal diffusion layer is a characteristic part of the present invention, and by using a material mainly composed of zinc oxide, the above function can be exhibited and the overwrite characteristics can be improved. Further, by adding at least one element selected from B, Al, Ga, and In to zinc oxide, thermal conductivity and light transmittance can be improved, and the addition amount is adjusted. Therefore, the initialization can be performed satisfactorily.
When B, Al, Ga, and In are A, A is included in the atomic ratio in the range of 0.01 ≦ A / (Zn + A) ≦ 0.1. To make . If the amount is less than this, the thermal conductivity and the film forming speed are lowered, and if it is more, the light transmittance is lowered.
[0020]
In addition, Cr or V can be added for the purpose of further improving characteristics and improving reliability. When these additive elements are X, X is preferably included in the range of 0.005 ≦ X / (Zn + A + X) ≦ 0.05. If it is less than this, the effect tends not to be obtained, and if it is more, the extinction coefficient increases and the light transmittance decreases.
The extinction coefficient is preferably 1.0 or less, and more preferably 0.5 or less, at the wavelength of the laser beam used for recording / reproducing information. If it is greater than 1.0, the absorptance in the first information layer increases, and recording / reproduction of the second information layer becomes difficult.
The manufacturing method of the thermal diffusion layer is the same as that of the recording layer.
The film thickness of the first thermal diffusion layer 15 is preferably 20 to 200 nm. If it is thinner than 20 nm, the heat dissipation effect cannot be obtained. If it is thicker than 200 nm, the stress increases, and not only the repeated recording characteristics deteriorate, but also a problem arises in mass productivity.
[0021]
FIG. 3 is a diagram showing the wavelength dependence of the light transmittance of a film having a thickness of 200 nm formed by changing the Al doping amount with respect to zinc oxide. From FIG. 3, it can be seen that the light transmittance on the long wavelength side decreases as the doping amount increases. Utilizing this fact, when the first information layer is initialized, if a laser having a longer wavelength than that of a laser having a wavelength of 810 nm, which has been conventionally used for initialization, is used, transmission to the second information layer Since there is almost no error, initialization can be performed with low power and uniformity. If a conventional 810 nm laser is used for initialization of the second information layer, the amount absorbed by the first information layer is small, so that the initialization can be satisfactorily performed with low power.
In addition, the present invention Many The first information layer 1 of the layer phase change type optical information recording medium preferably has a light transmittance of 40 to 70% at a laser beam wavelength (for example, 350 to 700 nm) used for recording and reproduction, and more preferably 45 to 45%. 60% is preferable.
In a two-layer phase change optical information recording medium on which recording is performed after initialization, the area in which the recording layer is in the amorphous state is smaller than the area in the crystalline state, so the light transmittance in the amorphous state is the light transmission in the crystalline state. It may be smaller than the rate.
[0022]
The method for producing the multilayer phase change optical information recording medium of the present invention will be described below.
One of the methods for producing a two-layer phase change optical information recording medium according to the present invention includes a film forming process, an initialization process, and a bonding process, and each process is basically performed in this order. FIG. 4 is a schematic sectional view of a two-layer phase change optical information recording medium manufactured by this method. Grooves are formed on the first substrate 3 and the second substrate 5.
In the film forming process, the first information layer 1 is formed on the surface of the first substrate 3 provided with the groove, and the second information layer 2 is formed on the surface of the second substrate 5 provided with the groove. Create separately.
The method of forming each layer constituting each of the first information layer 1 and the second information layer 2 is as described in the recording layer.
[0023]
In the initialization step, the first information layer 1 and the second information layer 2 are irradiated with energy light such as a laser beam over the entire surface to initialize, that is, crystallize the recording layer.
If there is a possibility that the film may be lifted by laser light energy during the initialization process, before the initialization process, a UV resin or the like is spin-coated on the first information layer and the second information layer and ultraviolet rays are applied. May be irradiated and cured to give an overcoat.
Next, the first information layer 1 formed on the surface of the first substrate 3 and the second information layer 2 formed on the surface of the second substrate 5 initialized as described above. Are bonded through the intermediate layer 4 while the first information layer 1 and the second information layer 2 face each other.
For example, one of the film surfaces is spin-coated with an ultraviolet curable resin as an intermediate layer, the film surfaces face each other, both substrates are pressed and adhered, and then the resin is cured by irradiating with ultraviolet rays. be able to.
In addition, after performing the said bonding process, you may initialize a 1st information layer and a 2nd information layer from the 1st board | substrate side.
[0024]
Next, another method for manufacturing the two-layer phase change optical information recording medium according to the present invention as shown in FIG. 2 will be described. This method includes a first film forming process, an intermediate layer forming process, a second film forming process, a substrate bonding process, and an initialization process, and each process is basically performed in this order.
FIG. 5 is a schematic cross-sectional view of a two-layer phase change optical information recording medium manufactured by this method. Grooves are formed on the intermediate layer 4 and the second substrate 5.
As the first film formation step, the second information layer 2 is formed on the surface of the second substrate 5 where the guide groove is provided. The film forming method is as described above.
As the intermediate layer forming step, the intermediate layer 4 having guide grooves is formed on the second information layer 2. For example, if a UV curable resin is applied to the entire surface of the second information layer 2 and a stamper made of a material capable of transmitting UV is pressed and cured by irradiating with UV, a groove is formed. can do.
As the second film forming step, the first information layer 1 is formed on the intermediate layer 4. The film forming method is as described above.
[0025]
As a substrate bonding step, the first information layer 1 and the first substrate 3 are bonded through the transparent layer 6. For example, an ultraviolet curable resin, which is a material of the transparent layer 6, is spin-coated on the first information layer 1 or the first substrate 3, and the first information layer 1 and the first substrate 3 are bonded to each other before the ultraviolet ray is bonded. Can be formed by irradiation. Alternatively, the first substrate 3 may be formed by applying a resin, which is a material of the first substrate 3, onto the first information layer 1 and curing it without forming the transparent layer 6.
As an initialization process, the first information layer 1 and the second information layer 2 are irradiated with energy light such as laser light over the entire surface from the transparent layer 6 side, whereby initialization, that is, crystallization of the recording layer is performed. . There is no problem even if the second information layer 2 is initialized immediately after the formation process of the intermediate layer 4.
[0026]
Next, the manufacture of a phase change optical information recording medium having three information layers as shown in FIG. 6 is performed in the following process sequence.
First film forming step (forming the first information layer on the first substrate and forming the third information layer on the second substrate) → intermediate layer forming step (forming the second intermediate layer on the third information layer of the second substrate) → The second film formation step (deposition of the second information layer on the intermediate layer of the second substrate) → Adhesion step (the first substrate and the second substrate face each other with the first information layer and the second information layer facing each other) While bonding through the first intermediate layer) → initialization step.
The initialization process may be performed immediately after each information layer is formed.
Next, the manufacture of a phase change optical information recording medium having three information layers as shown in FIG. 7 is performed in the following process sequence.
First film formation step (deposition of the third information layer) → First intermediate layer formation step (formation of the second intermediate layer) → Second film formation step (deposition of second information layer) → Formation of the second intermediate layer Step (formation of first intermediate layer) → Third film formation step (formation of first information layer) → First substrate bonding step (bonding via transparent layer) → Initialization step
The initialization process is performed after the first film formation process or immediately after the formation of the second intermediate layer for the third information layer, and after the second film formation process or immediately after the formation of the first intermediate layer for the second information layer. The layer may be after the third film formation step.
[0027]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited at all by these Examples.
[0028]
Example 1
As a preliminary experiment, a target of zinc oxide used for a thermal diffusion layer was sputtered on a glass substrate using a single wafer sputtering apparatus manufactured by Balzers to provide a film having a thickness of about 200 nm. At that time, Ar and O ₂ As a sputter gas, the Ar gas flow rate is kept constant while O gas is mixed. ₂ Sputtering while changing the gas flow rate, the thin film has the lowest electrical resistivity. ₂ The gas flow rate was determined. The electrical resistivity was measured using the four probe method.
On a first substrate made of a polycarbonate resin having a diameter of 12 cm and a thickness of 0.6 mm and having irregularities for tracking guides by continuous grooves on the surface, ZnS · SiO ₂ A first lower protective layer having a thickness of 120 nm comprising Ge, ₄ Ag ₁ In ₃ Sb ₇₀ Te ₂₂ 6 nm thick first recording layer made of ZnS · SiO ₂ Ar gas atmosphere in the order of a 15 nm thick first upper protective layer made of Ag, a 10 nm thick first reflective layer made of Ag—Pd—Cu, and a 120 nm thick first thermal diffusion layer made of each material shown in Table 1. A film was formed by the sputtering method. For the thermal diffusion layer using zinc oxide, the flow rate of Ar and O determined in the preliminary experiment ₂ The mixed gas was used.
Further, a substrate similar to the first substrate is used as the second substrate, and a second reflective layer made of Al—Ti and having a thickness of 120 nm is formed thereon, ZnS · SiO ₂ A 20 nm thick second upper protective layer comprising Ge, ₄ Ag ₁ In ₃ Sb ₇₀ Te ₂₂ A 12 nm thick second recording layer comprising ZnS · SiO ₂ The second lower protective layer having a thickness of 130 nm was formed in this order by sputtering in an Ar gas atmosphere. Here, the light transmittance at a wavelength of 405 nm of the first information layer was measured from the first substrate side using a spectrophotometer manufactured by SHIMADZU.
Next, the first information layer and the second information layer were irradiated with laser light from the first substrate side and the second information layer film surface side, respectively, and an initialization process was performed. Here, the light transmittance of the first information layer at a wavelength of 405 nm was also measured.
Next, an ultraviolet curable resin is applied on the film surface of the first information layer, and the second substrate is placed thereon with the second information layer surface side down, and is bonded by spin coating. Then, an intermediate layer was formed by irradiating ultraviolet rays to cure the ultraviolet curable resin, and two-layer phase change optical disks of Samples 1-1 to 1-4 having two information layers were produced. The thickness of the intermediate layer was 30 μm. Sample 1-1 is an example, and samples 1-2 to 1-4 are comparative examples.
[0029]
Recording was performed under the following conditions for each produced disc.
Laser wavelength: 405 nm
NA: 0.65
Line speed: 6.0 m / s
Track pitch: 0.40 μm
The jitter of the first information layer and the second information layer at a linear density of 0.18 μm / bit, and the jitter of the first information layer and the second information layer after overwriting 1000 times were measured.
Table 1 shows the measurement results for each sample.
Sample 1-1, which is a two-layer phase change optical disc according to the present invention, uses zinc oxide for the thermal diffusion layer, the light transmittance exceeds 40%, and the jitter value after recording once is the first information layer. The second information layer was 9% or less, and was found to be excellent as an optical disc. In Sample 1-2, aluminum nitride was used for the thermal diffusion layer. However, when the film was formed with a thickness of 120 nm, visible cracks frequently occurred, and recording / reproduction could not be performed. In Samples 1-3 and 1-4, silicon carbide and titanium oxide were used for the thermal diffusion layer, respectively. However, the light transmittance of the first information layer was 40% or less, the sensitivity of the second information layer was poor, and the jitter value was low. It was too large to be rewritten 1000 times. From the above results, it was confirmed that zinc oxide is preferable as the material of the heat diffusion layer of the first information layer.
[0030]
[Table 1]

[0031]
Example 2
The target of the thermal diffusion layer used in this example is mainly composed of zinc oxide, and the elements shown in the “Doping Element A” column of Table 2 are added at the atomic ratio shown in the “A / (Zn + A)” column. Except that these targets were used for the heat diffusion layer, the two-layer phase change type optical discs of Samples 2-1 to 2-9 were produced in the same manner as in Example 1.
Recording was performed on the created samples under the same conditions as in Example 1, and the jitter of the first information layer and the second information layer, and the jitter of the first information layer and the second information layer after overwriting 1000 times were recorded. It was measured.
Compared with Sample 1-1, the addition of B, Al, Ga, and In at an atomic ratio in the range of 0.01 to 0.1 reduces the jitter after 1000 rewrites and improves the overwrite characteristics. I found out that In Sample 2-8, the amount of Al added was 0.005, the jitter value was the same as that of Sample 1-1 containing no Al, and the effect of Al addition was not observed. On the other hand, in Sample 2-9, the amount of Al added was 0.2, the light transmittance was lowered, and the overwrite characteristics of the first information layer were also lowered. However, since the transmittance is large compared to Samples 1-2 to 1-4 as comparative examples and the jitter value after 1000 times of repeated recording is large, it can be measured. It is considered that the effect of the present invention by using the material is obtained.
From the above results, it can be seen that the ratio of the doping element A is preferably in the range of 0.01 ≦ A / (Zn + A) ≦ 0.1.
Also, from other prototype experiments, the recording layer thickness of the first information layer is 3 to 15 nm, the reflective layer thickness is 3 to 20 nm, and the thermal diffusion layer thickness is 20 to 200 nm. Both the first information layer and the second information layer can be recorded and reproduced satisfactorily, and in order to record and reproduce the second information layer satisfactorily, the light transmittance of the first information layer needs to be 40% or more. confirmed.
[0032]
[Table 2]

[0033]
Example 3
The target of the thermal diffusion layer used in this example is mainly composed of zinc oxide and contains Al and Cr or V. Al is Al / (Zn + Al + X) = 0.05 (X: Cr in atomic ratio). , V). The content (atomic ratio) of Cr or V is as shown in the “X / (Zn + Al + X)” column of Table 3.
Except for using these targets in the thermal diffusion layer, Samples 3-1 to 3-6 were produced as two-layer phase change optical discs in the same manner as in Example 1.
Recording was performed on the created samples under the same conditions as in Example 1, and the jitters of the first information layer and the second information layer were measured. Further, in order to check the storage reliability, each initially recorded sample was stored at 80 ° C. and 85% RH for 300 hours, and then the jitter of the 3T reproduction signal of the initial recording mark was measured.
Table 3 shows the measurement results of each sample. Samples 3-1 to 3-4 to which Cr or V was added at an atomic ratio in the range of 0.005 to 0.05, and Sample 3-5 to which 0.1 V was added were added to Sample 3-6 to which no additive was added. In comparison, it was found that the jitter value after storage of the first information layer was small, and it was excellent as an optical disk. However, in Sample 3-5, the light transmittance is decreased, and the jitter value of the second information layer is increased. From the above results, it can be seen that the ratio of the doping element X is preferably in the range of 0.005 ≦ X / (Zn + A + X) ≦ 0.05.
[0034]
[Table 3]

[0035]
Example 4
Similar to Sample 2-2 of Example 2, except that Ag is used for the first reflective layer and SiC with a film thickness of 3 nm is provided as the first barrier layer between the first upper protective layer and the first reflective layer. Thus, a two-layer phase change type optical disc of Sample 4-1 as an example was produced.
A sample 4-2 as a comparative example was prepared in the same manner as the sample 4-1, except that no barrier layer was provided.
Recording was performed on the created samples under the same conditions as in Example 1, and the jitters of the first information layer and the second information layer were measured. Further, in order to check the storage reliability, each initially recorded sample was stored at 80 ° C. and 85% RH for 300 hours, and then the jitter of the 3T reproduction signal of the initial recording mark was measured. The results are as shown in Table 4. It was found that when Ag was used for the first reflective layer, the sample provided with the barrier layer had good jitter after storage and was excellent as an optical disk.
[0036]
[Table 4]

[0037]
Example 5
On a second substrate made of a polycarbonate resin having a diameter of 12 cm and a thickness of 1.1 mm, and having irregularities for tracking guides by continuous grooves on the surface, a second reflective layer made of Al—Ti and having a thickness of 120 nm, ZnS · SiO ₂ A 20 nm thick second upper protective layer comprising Ge, ₄ Ag ₁ In ₃ Sb ₇₀ Te ₂₂ A 12 nm thick second recording layer comprising ZnS · SiO ₂ A second lower protective layer having a thickness of 130 nm was formed in this order by sputtering in an Ar gas atmosphere to form a second information layer.
On this second information layer, a resin was applied, and an intermediate layer having irregularities for tracking guides by continuous grooves was formed by a 2P (photopolymerization) method. The thickness of the intermediate layer was 30 μm.
Further thereon, a first thermal diffusion layer having a thickness of 120 nm is provided using the same target as that of Sample 2-2, and a first reflective layer made of Ag—Pd—Cu having a thickness of 10 nm, ZnS · SiO ₂ A first upper protective layer having a thickness of 15 nm comprising Ge, ₄ Ag ₁ In ₃ Sb ₇₀ Te ₂₂ 6 nm thick first recording layer made of ZnS · SiO ₂ A first information layer was formed in the order of the first lower protective layer having a thickness of 120 nm by sputtering in an Ar gas atmosphere. For thermal diffusion layers, Ar and O ₂ As a sputtering gas, Ar gas and O which increase the electrical conductivity and light transmittance are used. ₂ Film formation was performed at a gas ratio.
Further, a first substrate made of a polycarbonate film having a diameter of 12 cm and a thickness of 50 μm is bonded onto the first information layer film surface through a transparent layer made of a double-sided adhesive sheet having a thickness of 45 μm, and a two-layer phase change optical disc. It was created.
Separately, for light transmittance measurement, the first information layer, the transparent layer, and the first substrate were similarly provided on a substrate having a thickness of 1.1 mm, and the light transmittance from the first substrate side was measured. .
The optical transmittance of the optical disk of this example before initialization of the first information layer was 48% at a wavelength of 405 nm, 45% at a wavelength of 810 nm, and 20% at a wavelength of 1060 nm.
[0038]
Next, the two-layer phase change type optical disk of this example was initialized using a two-layer medium initialization apparatus having two lasers. The configuration of the initialization apparatus used in this example is schematically shown in FIG. This initialization apparatus is provided with two optical heads composed of a semiconductor laser and an objective lens. The two optical heads are configured by combining a semiconductor laser that emits light with wavelengths of 1060 nm and 810 nm and an optical system device having a focusing function, respectively. While rotating the optical disk by the spindle motor, the two optical heads move from the inner periphery to the outer periphery (in the direction of the arrow in the figure), and initialization is performed.
In this embodiment, a laser with a wavelength of 1060 nm is used for the first information layer, a laser with a wavelength of 810 nm is used for the second information layer, the linear velocity is 3 m / sec, and the feed pitch to the outer periphery of the optical head is 35 μm / rotation. Initialization was performed.
Similarly, the disk for measuring light transmittance was initialized at a wavelength of 1060 nm, and the light transmittance at 405 nm was measured and found to be 51%.
The signal of each information layer of the initialized two-layer optical disk was observed with an oscilloscope. The RF signal was good in each layer with little fluctuation. This is because the light transmittance at a wavelength of 1060 nm is reduced by using the thermal diffusion layer of the present invention for the first information layer, and the first information layer is efficiently focused without being out of focus by a laser of a wavelength of 1060 nm. This is probably because the initialization was successful. On the other hand, since the light transmittance of the first information layer at the wavelength of 810 nm is large, there is little light loss when the second information layer is initialized with the laser of the wavelength of 810 nm, and the initialization can be performed efficiently. Conceivable.
[0039]
Recording was performed on each medium prepared as described above under the following conditions.
Laser wavelength: 405 nm
NA: 0.85
Line speed: 6.5m / s
Track pitch: 0.32 μm
When the jitter of the first information layer and the second information layer at a linear density of 0.16 μm / bit and the jitter of the first information layer and the second information layer after overwriting 1000 times were measured, the first information layer, Both the second information layer could be recorded and reproduced satisfactorily.
Also, from other prototype experiments, when recording / reproduction is performed with a pickup with NA = 0.85, the light transmittance of the first information layer is 40% or more in order to record / reproduce the second information layer satisfactorily. It was confirmed that it was necessary.
From the above, the optical disk of the present invention can be recorded and reproduced satisfactorily by adjusting the thickness of the first substrate in the range of 10 to 600 μm even when the numerical aperture NA of the objective lens for recording and reproduction is changed. Can be done. It has also been found that the optical disc of the present invention can be initialized reliably and satisfactorily.
[0040]
【The invention's effect】
The present invention 1 Accordingly, it is possible to provide a multilayer phase change optical information recording medium having excellent overwrite characteristics.
The present invention 2 Accordingly, it is possible to provide a multilayer phase change optical information recording medium with further excellent storage reliability.
The present invention 3 ~ 7 According to the above, the reflectivity, recording sensitivity and light transmittance (except for the Nth layer) of each layer can be optimized according to the recording, erasing and reproducing conditions, and the recording / reproducing characteristics of all information layers An excellent multilayer phase change optical information recording medium can be provided.
The present invention 8 According to the present invention, the first information layer and the second information layer can be optically separated by the intermediate layer, Many A multilayer phase change optical information recording medium capable of satisfactorily initializing both of the two information layers by using an initialization apparatus having various types of wavelength light sources can be provided.
The present invention 9 According to the above, both the first information layer and the second information layer have good sensitivity and excellent recording / reproduction characteristics. Many A layer phase change type optical information recording medium can be provided.
The present invention 10 Can be easily manufactured even when the first substrate is thin. Many A layer phase change type optical information recording medium can be provided.
The present invention 11 According to the above, corrosion of the reflective layer is suppressed and storage reliability is excellent. Many A layer phase change type optical information recording medium can be provided.
The present invention 12 According to the above, even when the numerical aperture NA of the objective lens changes, it is possible to perform good recording / reproduction. Many A layer phase change type optical information recording medium can be provided.
The present invention 13 According to the present invention 1 12 Large-capacity recording / reproduction can be performed using the multilayer phase change optical information recording medium.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a two-layer phase change optical information recording medium according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a two-layer phase change optical information recording medium according to another embodiment of the present invention.
FIG. 3 is a graph showing the wavelength dependence of the light transmittance of a film having a thickness of 200 nm formed by changing the Al doping amount with respect to zinc oxide.
FIG. 4 is a schematic cross-sectional view of a two-layer phase change optical information recording medium manufactured by a method including a film forming process, an initialization process, and an adhesion process.
FIG. 5 is a schematic cross-sectional view of a two-layer phase change optical information recording medium manufactured by a method including a first film formation step, an intermediate layer formation step, a second film formation step, a substrate bonding step, and an initialization step.
FIG. 6 is a view showing a phase change optical information recording medium having three information layers according to the present invention.
FIG. 7 is a view showing a phase change optical information recording medium having three other information layers according to the present invention.
FIG. 8 is a diagram schematically showing a configuration of an initialization apparatus used in Embodiment 5.

Claims (13)

In an optical information recording medium in which an information layer having a recording layer capable of recording information by causing a phase change between a crystalline state and an amorphous state by incidence of light is provided (N: an integer of 2 or more). When each information layer is a first information layer, a second information layer,... An Nth information layer as viewed from the light incident side, at least one information layer other than the Nth information layer is at the bottom. It has a layer structure in which a protective layer, a recording layer, an upper protective layer, a reflective layer, and a heat diffusion layer are laminated in this order. The heat diffusion layer is mainly composed of zinc oxide , and A (= B, Al, Ga, A multilayer phase change optical information recording medium comprising: an atomic ratio of 0.01 ≦ A / (Zn + A) ≦ 0.1 . Thermal diffusion layer, the further X (= Cr or V), in atomic ratio, 0.005 ≦ X / (Zn + A + X) ≦ 0.05, multi-phase according to claim 1, characterized in that it contains in the range of Changeable optical information recording medium. 3. The multilayer phase change optical information recording medium according to claim 1, wherein the thickness of the thermal diffusion layer is 20 to 200 nm. The recording layer in the information layer having the thermal diffusion layer is mainly composed of Sb and Te, Ag, In, Ge, Se, Sn, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Bi, Si, Dy, Pd, Pt, Au, S, B, C, multilayer phase-change type optical information recording according to any one of claims 1 to 3, characterized in that it comprises at least one of P Medium. The thickness of the recording layer of the information layer having the thermal diffusion layer, multi-layer phase-change optical information recording medium according to any one of claims 1-4, characterized in that the 3 to 15 nm. The multilayer phase change optical information according to any one of claims 1 to 5 , wherein the reflective layer in the information layer having the thermal diffusion layer is mainly composed of at least one of Au, Ag, Cu, W, Al, and Ta. recoding media. The thickness of the reflective layer of the information layer having the thermal diffusion layer, multi-layer phase-change optical information recording medium according to any one of claims 1 to 6, characterized in that a 3 to 20 nm. A multilayer phase change optical information recording medium capable of recording / reproducing information, wherein two information layers are provided between a first substrate and a second substrate, and an intermediate layer is provided between the two information layers. The first information layer includes a first lower protective layer, a first recording layer, a first upper protective layer, a first reflective layer, and a first thermal diffusion layer, and the second information layer is a second lower protective layer. , The second recording layer, the second upper protective layer, and the second reflective layer, and the first substrate, the first lower protective layer, the first recording layer, the first, The upper protective layer, the first reflective layer, the first thermal diffusion layer, the intermediate layer, the second lower protective layer, the second recording layer, the second upper protective layer, the second reflective layer, and the second substrate are laminated in this order. A multilayer phase change optical information recording medium according to any one of claims 1 to 7 . 9. The multilayer phase change optical information recording medium according to claim 8 , wherein the light transmittance of the first information layer is 40 to 70% with respect to light having a wavelength of 350 to 700 nm. The first substrate and a multilayer phase-change type optical information recording medium according to claim 8, wherein providing a transparent layer between the first lower protective layer. According to any one of claims 8 to 10, characterized in that a barrier layer between the during and / or second upper protective layer and a second reflective layer between the first upper protective layer and the first reflective layer Multi-layer phase change optical information recording medium. The multilayer phase change optical information recording medium according to any one of claims 8 to 11 , wherein the thickness of the first substrate is 10 to 600 µm. For each information layer of a multilayer phase-change type optical information recording medium according to any one of claims 1 to 12, that the first information layer side by applying a light beam having a wavelength of 350~450nm for recording and reproducing of information A recording / reproducing method for a multilayer phase change optical information recording medium.

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