JP4053715B2 - Optical information recording medium - Google Patents

Description

【００３７】
実施例
実際に光記録媒体（以下、光ディスクと記す）を作製し、半透明放熱層を設けた構成が半透明放熱層を設けない構成より放熱効果に優れていることを以下のようにして示した。
厚さ０．６ｍｍのポリカーボネート基板上にＺｎＳ-ＳｉＯ₂第１誘電体層（５５ｎｍ）、Ｇｅ₅Ｓｂ₇₁Ｔｅ₂₄記録層（１０ｎｍ）、ＺｎＳ-ＳｉＯ₂第２誘電体層（５ｎｍ）、ＳｉＯ₂拡散防止層（２ｎｍ）、Ａｇ半透明放熱層（２０ｎｍ）、ＳｉＯ₂拡散防止層（２ｎｍ）、ＺｎＳ-ＳｉＯ₂第３誘電体層（９０ｎｍ）、ＳｉＯ₂拡散防止層（２ｎｍ）、Ａｇ半透明反射層（１５ｎｍ）、ＳｉＯ₂拡散防止層（２ｎｍ）をスパッタリング法により作製し、この上にさらに紫外線硬化樹脂からなる保護コートをおこなった（実施例）。基板溝幅は０．３５ｕｍ、溝深さは３３ｎｍ、溝ピッチ０．７４ｕｍである。なお、記録層膜厚は、実験上、初期結晶化を容易にするために膜厚（１０ｎｍ）とした。
【００３８】
この光ディスクを初期結晶化した後、波長６３５ｎｍ、ＮＡ０．６の光学系を有する光ディスク評価装置を用いて記録特性を測定した。記録条件は、線速度４ｍ／ｓ、消去パワーＰｅと記録パワーＰｗの比Ｐｅ／Ｐｗ＝０．５、クロック周期を３８．２ｎｓとし、８−１６変調ランダム信号をパルストレイン法を用い溝内に記録した。１０回のダイレクトオーバーライト（ＤＯＷ）後のEdge to clockジッタのパワー依存性の測定結果を図１に示す。ジッタ値はクロック周期で規格化した値を用いた。
【００３９】
この光ディスクの透過率は鏡面部で記録層が結晶状態のとき３０％、記録層がアモルファス状態のとき３７％であった。透過率の算出は、１２０ｎｍ厚のＡｇ膜からの反射光量を０．６ｍｍのポリカーボネート基板を通して測定したときの値をＲ１とし、前記光ディスクを通して測定したときの値をＲ２としたとき、透過率＝（Ｒ２／Ｒ１）^1/2の式から求めた。この結果は、記録層が計算値（５ｎｍ）より厚いこともあり、光ディスクの透過率は必ずしも十分に大きいとは言えないが、２層化記録媒体の可能性を示すことは明らかである。
【００４０】
比較例１
厚さ０．６ｍｍのポリカーボネート基板上にＺｎＳ-ＳｉＯ₂誘電体層（１０５ｎｍ）、Ｇｅ₅Ｓｂ₇₁Ｔｅ₂₄記録層（１０ｎｍ）、ＺｎＳ-ＳｉＯ₂誘電体層（１１５ｎｍ）をスパッタリング法により作製し、この上にさらに紫外線硬化樹脂からなる保護コートをおこなった（比較例１）。この光ディスクにつき上記と全く同じ記録特性の評価をおこなった。その結果、８〜１４ｍＷの記録パワーではジッタの測定が可能であるような記録マークは形成されなかった。この光ディスクはアモルファスマークが形成された場合は十分な信号強度がでるように設計されたものであり、記録マークができない理由は放熱が不十分であるため、溶融後その部分が再結晶化しているためと思われる。
以上より実施例での放熱効果は比較例１と比較して十分に大きいことがわかる。透過率をさらに大きくするため記録層を薄くした場合には、逃がすべき熱量が小さくなるためさらに効率よい放熱効果が得られると考えられる。
【００４１】
比較例２
厚さ０．６ｍｍのポリカーボネート基板上にＺｎＳ-ＳｉＯ₂誘電体層（５５ｎｍ）、Ｇｅ₅Ｓｂ₇₁Ｔｅ₂₄記録層（１０ｎｍ）、ＺｎＳ-ＳｉＯ₂誘電体層（５ｎｍ）、ＳｉＯ₂拡散防止層（２ｎｍ）、Ａｇ半透明放熱層（２０ｎｍ）、ＳｉＯ₂拡散防止層（２ｎｍ）をスパッタリング法により作製し、この上にさらに紫外線硬化樹脂からなる保護コートをおこなった（比較例２）。この光ディスクの透過率は鏡面部で記録層が結晶状態のとき１６％、記録層がアモルファス状態のとき２０％であり、実施例の透過率より小さかった。
【００４２】
【発明の効果】
本発明の層構成からなる光学的情報記録用媒体においては、信号強度、放熱効果、透過率のすべてを十分に大きくすることが可能になり、特により高密度化のための多層化記録媒体への応用が期待される。
【図面の簡単な説明】
【図１】 図１は実施例のEdge to clockジッタのパワー依存性の測定結果を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rewritable high-density optical information recording medium (hereinafter sometimes referred to as an optical recording medium). In particular, the present invention relates to a phase change recording medium that has a high transmittance and is expected to be used for a multilayered recording medium in which a plurality of optical recording media are stacked.
[0002]
[Prior art]
As the amount of information increases, a recording medium capable of recording and reproducing a large amount of data at a high density and at a high speed is required. However, an optical recording medium is expected as one of recording media that can respond to such applications. . There are two types of optical recording media: a write-once type that can be recorded only once, and a rewritable type that can be repeatedly recorded and erased. Examples of the rewritable optical recording medium include a magneto-optical recording medium using a magneto-optical effect and a phase change recording medium using a change in reflectivity accompanying a reversible change in crystal-amorphous state. A phase change recording medium usually has a layer structure in which a dielectric layer, a recording layer, a dielectric layer, and a metal reflective layer are provided in this order. The metal reflection layer is used to promote thermal diffusion to enhance the heat dissipation effect and form the amorphous mark more stably, and is also referred to as a metal heat dissipation layer. For this reason, the metal heat dissipation layer is important for obtaining a sufficient heat dissipation effect necessary for forming an amorphous layer, and is usually formed of a material mainly composed of a metal having high reflectivity and high thermal conductivity. In addition, the dielectric layer provided between the recording layer and the metal heat dissipation layer promotes thermal diffusion from the recording layer during recording, contributes to the formation of amorphous marks, and acts as a heat storage layer during erasure, thus controlling the heat dissipation effect. Is important to do.
[0003]
In recent years, in order to record / reproduce a huge amount of information at a high speed, a multilayer recording medium has been studied with the aim of further increasing the density. That is, it is an attempt to increase the recording density by stacking two or more optical recording media at a distance larger than the focal depth of the optical system used. The individual optical recording media stacked here may be hereinafter referred to as a recording medium unit. In this case, the recording medium unit other than the recording medium unit farthest from the incident direction of the laser light needs to transmit the laser light. In order to transmit laser light, it is preferable not to use the metal heat-dissipating layer basically in a recording medium unit that requires light transmission, and if used, it should be thin enough to obtain sufficient light transmission. It will be necessary.
[0004]
However, when there is no metal heat dissipation layer or when it is thin, the heat dissipation effect is not sufficient. Therefore, when the recording medium unit that requires light transmission is a phase change type recording medium, there is a problem that the amorphous mark is not sufficiently formed because the portion where the amorphous is to be formed is recrystallized when cooled after being melted. is there. If the composition or the like of the recording layer is changed to reduce the crystallization rate and prevent recrystallization, the amorphous mark in the erasing laser irradiation portion will be insufficiently crystallized. That is, the range of crystallization speeds usable as a rewritable recording medium is narrowed.
[0005]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and its object is to provide sufficient transmittance required as a recording medium unit that can be used for multilayer recording media and sufficient heat dissipation necessary for forming recording marks. The goal is to achieve both effects. In order to increase the heat dissipation effect, the metal heat dissipation layer needs to have a certain thickness. On the other hand, if the film is thick, there is a problem that the amount of transmitted light decreases. As a result of investigating the control of the film thickness of the metal heat dissipation layer and the amount of transmitted light, the present invention has been found out that it can be improved by further providing a dielectric layer and a translucent reflective layer on the metal heat dissipation layer.
[0006]
[Means for Solving the Problems]
    The present invention provides an optical information recording medium that can be used for multilayer recording media, and in particular, an optical information recording medium that is expected to be used as a recording medium unit that requires light transmission. The gist is that at least a first dielectric layer, a recording layer, a second dielectric layer, a semi-transparent heat dissipation layer containing metal as a main component, a third dielectric layer, and a semi-transparent reflective layer in this order.And the transmittance is 20% or more.The present invention resides in an optical information recording medium.
  Another gist of the present invention is an optical information recording medium in which two or more recording media are laminated, wherein at least one recording medium includes at least a first dielectric layer, a recording layer, and a second dielectric layer. An optical recording medium having a translucent heat dissipation layer mainly composed of metal, a third dielectric layer, and a translucent reflective layer in this order and having a transmittance of 20% or more. An optical information recording medium is characterized in that optical recording media are laminated.
[0007]
  As a preferred aspect of the present invention, in the optical information recording medium, the translucent heat dissipation layer is made of a material mainly composed of silver, and the thickness thereof is 2 to 50 nm. The second dielectric layer [Λ / (8n)] <d <[λ / (2n) where d is the thickness of the third dielectric layer, n is the refractive index, and λ is the laser wavelength used. And the semi-transparent reflective layer is a metal-based material, and the recording layer is a phase change recording layer.
  Furthermore, in an optical information recording medium in which two or more recording media are laminated,It has at least a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat dissipation layer mainly composed of metal, a third dielectric layer, and a translucent reflective layer in this order, and a transmittance of 20 % Of optical recording mediaProvided close to the incident light side; andOptical recording mediaThe semi-transparent heat radiation layer and the semi-transparent reflection layer are made of a metal material containing silver as a main component, and the thickness of the semi-transparent reflection layer may be less than the film thickness of the semi-transparent heat radiation layer.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
    The optical information recording medium of the present invention is as described above.Used as a recording medium unit constituting a multilayer recording medium,At least a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat dissipation layer mainly composed of metal, a third dielectric layer, and a translucent reflective layer are provided in this order.And a transmittance of 20% or moreIt is.
  Generally, a metal heat dissipation layer of a phase change recording medium composed of a dielectric layer, a recording layer, a dielectric layer, and a metal heat dissipation layer is required to have a high heat dissipation effect, so that the effect is sufficiently exhibited. However, it has a certain film thickness. However, in such a film thickness having an effective heat dissipation effect, the reflectivity with respect to the laser beam is high, and the light transmittance as a recording medium becomes small. Therefore, in a multilayered recording medium that requires a large transmittance. It was not applicable as a recording medium unit, and in the case of a recording medium unit, it was generally considered that a metal heat dissipation layer could not be provided.
[0009]
The recording medium of the present invention has the above-described layer structure, and as a result, the thickness of the metal heat dissipation layer is appropriately adjusted, and a phase adjusting dielectric layer and a semitransparent reflective layer are further added to cause multiple reflection. This is based on a novel finding that the reflectance can be reduced and the transmittance can be increased and high heat dissipation can be secured.
In the present specification, the phrase “semi-transparent” means that the light transmittance is usually 3% or more. The light transmittance in the “semi-transparent heat radiation layer” and “semi-transparent reflective layer” of the present invention is preferably 3% or more, particularly preferably 5% or more, more preferably 10% or more, and most preferably 15% or more. is there. The transmittance can be calculated from the complex refractive index and the film thickness for the light of the wavelength used. The light transmittance of the “recording medium” of the present invention is usually 20% or more, preferably 30% or more.
[0010]
As described above, the present invention uses multiple reflections to reduce the amount of reflected light and increase the amount of transmitted light. In such a case, the translucent heat radiation layer and the translucent reflective layer tend to absorb light easily. is there. Therefore, it is preferable to select a material having as little light absorption as possible as the material constituting the translucent heat radiation layer and the translucent reflection layer.
The translucent heat dissipation layer has a certain amount of transmitted light as described above, but is used with a relatively thin film thickness in order to increase the transmittance of the entire recording medium.
In order to obtain an effective heat dissipation effect with a relatively thin film thickness, the material used as the translucent heat dissipation layer needs to have a sufficiently high thermal conductivity. Examples of the material having high thermal conductivity include metals having Ag, Au, Al, Cu, or the like as a main component. Among these, Ag has the highest thermal conductivity, and therefore Ag is most preferable in terms of thermal conductivity.
[0011]
On the other hand, considering light absorption, Ag is most preferable among the above metals. In particular, Au, Cu, and Al are more likely to absorb light than Ag at short wavelengths, and therefore Ag is particularly preferable when a short wavelength laser of 650 nm or less is used. Further, Ag is preferable in terms of productivity and economy because it is relatively inexpensive as a sputtering target, has a stable discharge, has a high deposition rate, and is stable in the air. Therefore, Ag is the most preferable material for the semitransparent heat dissipation layer from a comprehensive viewpoint.
Furthermore, the metals Ag, Al, Au, Cu as the main component of the material that can form the translucent heat dissipation layer have the disadvantage that the thermal conductivity decreases and the light absorption increases when impurities are mixed. Stability and film surface flatness may be improved. % Of impurity elements may be included. As impurity elements, Cr, Mo, Mg, Zr, V, Ag, In, Ga, Zn, Sn, Si, Cu, Au, Al, Pd, Pt, Pb, Cr, Co, O, Se, V, Nb , Ti, O, N and the like.
[0012]
As for the film thickness of the translucent heat dissipation layer, the optimum film thickness varies depending on the material used and the laser wavelength used. However, when the material is Ag and the laser wavelength is around 400 to 650 nm, the film thickness should be about 2 to 50 nm. More preferably, it is 5-30 nm. If it is thinner than 2 nm, the heat dissipation effect is reduced, and if it is thicker than 50 nm, the amount of transmitted light is reduced. Since the absolute value of the imaginary part of the complex refractive index is small at a short wavelength, Ag tends to have a larger transmittance at the short wavelength even when the film thickness is the same. Therefore, the compatibility between the sufficient heat radiation effect and the sufficient transmittance tends to be achieved at the short wavelength, and the effect of the present invention becomes more advantageous at the short wavelength. However, the signal intensity of the recording layer of the phase change optical disc tends to decrease at a short wavelength.
[0013]
When an interaction such as element diffusion occurs between the translucent heat dissipation layer and the second or third dielectric layer, the diffusion preventing layer is formed at the interface between the heat dissipation layer and the dielectric layer. Etc. are preferably further provided. Examples of the diffusion preventing layer material include silicon oxide, silicon nitride, silicon carbide, tantalum oxide, cerium oxide, lanthanum oxide, yttrium oxide, aluminum oxide, silver oxide, and the like. Diamond is a preferable material for the heat-dissipating layer because of its higher thermal conductivity and can be transparent, but there are difficulties in film formation.
[0014]
The translucent reflective layer is provided on the translucent heat dissipation layer via the third dielectric layer, and since the distance is slightly away from the recording layer, a large heat dissipation effect cannot be expected. It is important that the translucent reflective layer has a certain optical reflectivity and a small light absorption. When the translucent reflective layer is formed from a material containing a metal as a main component, this condition is also a necessary condition for the translucent heat radiating layer. Can be used as Of the above-mentioned metal materials mainly composed of Ag, Au, Al, Cu, etc., Ag is the most preferable.
[0015]
Regarding the film thickness of the translucent reflective layer, the optimum film thickness varies depending on the material used and the laser wavelength used. However, when the material is Ag and the laser wavelength is 400 to 650 nm, the film thickness is preferably about 50 nm or less. If it is thicker than 50 nm, the amount of transmitted light is reduced, the transmittance of the entire recording medium is lowered, and it may not be suitable for use as a recording medium unit particularly in a multilayer recording medium. The optimum film thickness of the semi-transparent reflective layer is related to the film thickness of the semi-transparent heat radiation layer, etc., and varies depending on the material and the wavelength of the laser used. Most of the thicknesses are good. However, it is usually 1 nm or more because it is too thin due to the characteristics of the recording medium and manufacturing difficulties.
When interaction such as element diffusion occurs between the translucent reflective layer and the third dielectric layer or between the translucent reflective layer and the UV curable resin layer or adhesive layer provided on the translucent reflective layer as necessary. It is preferable to further provide a diffusion preventing layer or the like at the interface between the respective layers. As a material of the diffusion preventing layer, a material used for the diffusion preventing layer provided between the translucent heat radiation layer and the dielectric layer can be used.
[0016]
As the translucent reflective layer, a dielectric mirror produced by laminating two or more types of transparent dielectric layers having different refractive indexes can also be used. The dielectric mirror may be the most preferable material that satisfies the condition that a certain degree of reflectance required by the translucent reflective layer is obtained and the absorption is small. Examples of dielectric mirrors are ZnS-SiO₂And SiO₂And the like. The dielectric mirror is preferably laminated so that the laser wavelength used is λ, the dielectric refractive index is n, and the thickness of each laminated dielectric film is λ / (4n). However, the dielectric mirror is disadvantageous in terms of time for production and complexity of the production apparatus as compared with the metal translucent reflective layer, and may cause a problem in storage stability.
[0017]
A dielectric layer (third dielectric layer) provided between the translucent heat radiation layer and the translucent reflective layer has a role of adjusting the phase during multiple reflection. The material of the dielectric layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, film formation speed, and the like. In general, oxides, sulfides, nitrides, and fluorides such as Ca, Mg, and Li, which are highly transparent and have a high melting point, can be used. These oxides, sulfides, nitrides, and fluorides do not necessarily have a stoichiometric composition, and it is also effective to use a composition or a mixture for controlling the refractive index and the like. More specifically, a mixture of heat-resistant compounds such as ZnS and rare earth sulfides and oxides, nitrides, and carbides can be mentioned. A dielectric mixture is preferable in consideration of repeated recording characteristics.
[0018]
Specifically, those containing 20 mol% or more and 90 mol% or less of sulfides such as zinc sulfide, tantalum sulfide, rare earth (Y, La, Ce, Nd, etc.) sulfides alone or as a mixture are preferable. The balance of the mixture is preferably a heat-resistant compound having a melting point or decomposition temperature of 1000 ° C. or higher. The heat-resistant compound having a melting point or decomposition temperature of 1000 ° C. or more includes Mg, Ca, Sr, Y, La, Ce, Ho, Er, Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Si. , Oxides such as Ge and Pb, nitrides, carbides, and fluorides such as Ca, Mg, and Li. Among these, ZnS and SiO₂In many cases, a mixture consisting of is used as a dielectric layer of a phase change optical recording medium. The film density of the dielectric layer is preferably 80% or more of the bulk state from the viewpoint of mechanical strength (Thin Solid Films, Vol. 278 (1996), pages 74 to 81).
[0019]
    The preferred film thickness of the third dielectric layer varies depending on the material, film thickness, laser wavelength used, etc., such as the dielectric, translucent heat radiation layer, and translucent reflective layer. In the layer structure of the recording medium of the present invention, the phenomenon is complicated because multiple reflection occurs when both the transmissivity and reflectivity of the translucent heat dissipation layer and the translucent reflection layer are large to some extent, but the phenomenon is complicated, but the translucent heat dissipation layer and the translucent reflection When the layer is made of a material whose main component is a metal, the film thickness of the third dielectric layer can be easily understood by simplifying the phenomenon as follows. That is, in order to increase the transmittance of the three-layer structure of the semitransparent heat dissipation layer, the third dielectric layer, and the semitransparent reflection layer, it is considered effective to decrease the reflectance of this portion. For that purpose, the phase of the light reflected by the translucent heat dissipation layer and the light transmitted through the translucent heat dissipation layer, reflected by the translucent reflection layer, and transmitted again through the translucent heat dissipation layer.LightIt is considered that the phase of each other should be offset by half a wavelength so as to cancel each other. That is, when the film thickness of the third dielectric layer is d, the refractive index is n, and the laser wavelength used is λ, there seems to be a suitable range near d = λ / (4n). Actually, even if there is a slight deviation from this value due to the effects of multiple reflections or the film thickness of the semi-transparent heat radiation layer and the semi-transparent reflection layer, the film thickness (d) of the third dielectric layer is [ λ / (8n)] <d <[λ / (2n)] is preferable.
[0020]
The second dielectric layer is provided between the recording layer and the translucent heat dissipation layer, and this dielectric layer has a role of controlling heat flowing from the recording layer to the translucent heat dissipation layer. The film thickness of the second dielectric layer is preferably about 2 to 30 nm, more preferably 5 to 20 nm. If the thickness exceeds 30 nm, the heat dissipation effect becomes insufficient. On the other hand, if the thickness is less than 2 nm, the recording sensitivity deteriorates, and further element diffusion occurs between the recording layer and the translucent heat dissipation layer. . As the material for the second dielectric layer, the same materials as those used for the third dielectric layer provided between the translucent heat dissipation layer and the translucent reflective layer can be used.
[0021]
The first dielectric layer is provided so as to cover the upper and lower sides of the recording layer together with the second dielectric layer. In general, the first dielectric layer is interposed between the recording layer and the substrate.
The first dielectric layer needs to suppress substrate deformation due to heat, and the film thickness is preferably 30 nm or more. If it is less than 30 nm, microscopic substrate deformation is accumulated during repeated overwriting, and reproduction light is scattered, resulting in a significant increase in noise. On the other hand, if the thickness of the dielectric layer exceeds 500 nm, the internal stress of the dielectric itself and the difference in elastic properties with the substrate become significant, and cracks are likely to occur. Although the upper limit is substantially about 200 nm from the relationship with the film formation time, if it is thicker than 200 nm, the groove shape seen on the recording layer surface is not preferable. More preferably, it is 150 nm or less. As the material for the first dielectric layer, the same materials as those used for the third dielectric layer provided between the translucent heat radiation layer and the translucent reflective layer can be used.
[0022]
As the recording layer in the optical recording medium of the present invention, a known phase change type optical recording layer can be used. For example, a series compound such as GeSbTe, InSbTe, AgSbTe, or AgInSbTe is selected as a material that can be overwritten. Among these, {(Sb₂Te_Three)_1-x(GeTe)_x}_1-ySb_yAlloy (where 0.2 <x <0.9, 0 ≦ y <0.1), or (Sb_xTe_1-x)_yM_1-yAlloy (however, 0.6 <x <0.9, 0.7 <y <1, M is Ge, Ag, In, Ga, Zn, Sn, Si, Cu, Au, Pd, Pt, Pb, Cr, A thin film composed mainly of at least one selected from Co, O, S, Se, V, Nb, and Ta) is stable in both crystalline and amorphous states, and has a high-speed phase transition between the two states. Is possible. Furthermore, there is an advantage that segregation hardly occurs when repeated overwriting, and it is the most practical material.
The recording layer is (Sb_xTe_1-x)_yM_1-yAlloy (however, 0.6 <x <0.9, 0.7 <y <1, M is Ge, Ag, In, Ga, Zn, Sn, Si, Cu, Au, Pd, Pt, Pb, Cr, In the case of a phase change medium mainly composed of at least one selected from Co, O, S, Se, V, Nb, and Ta), the difference in heat distribution is easily reflected in the mark shape. It becomes important.
[0023]
When the recording layer is a phase change optical recording layer, the thickness is preferably in the range of 3 nm to 15 nm. When the thickness of the recording layer is less than 3 nm, it is difficult to obtain sufficient contrast, and initial crystallization tends to be difficult. On the other hand, if it exceeds 15 nm, it is difficult to obtain a sufficient transmittance. More preferably, it is 5-10 nm.
[0024]
The recording layer is often obtained by sputtering an alloy target in an inert gas, particularly Ar gas. Note that the thickness of the recording layer and the dielectric layer has good laser light absorption efficiency in consideration of the interference effect associated with the multilayer structure in addition to the limitations on the mechanical strength and reliability, and the recording signal The amplitude, that is, the contrast between the recorded state and the unrecorded state is selected to be large.
[0025]
In the optical recording medium of the present invention, as the substrate, a transparent resin such as polycarbonate, acrylic or polyolefin, or glass can be used. Among these, polycarbonate is preferable because it has a track record and is inexpensive and excellent in economic efficiency. The thickness of the substrate is usually 0.05 to 5 mm, preferably 0.1 to 2 mm.
[0026]
The recording layer, the first to third dielectric layers, the translucent heat dissipation layer, the translucent reflection layer, the diffusion prevention layer, and the like are formed by a sputtering method or the like. Each of these layers can be formed by an in-line apparatus in which a sputtering target of each layer, that is, a recording film target, a dielectric film target, and, if necessary, a reflective layer material target is installed in the same vacuum chamber. This is desirable in terms of preventing interlayer oxidation and contamination. It is also excellent in terms of productivity.
[0027]
The layer structure of the optical recording medium of the present invention is basically such that when a recording / reproducing laser beam is incident from the substrate side, the first dielectric layer, the recording layer, the second dielectric layer are basically formed on the substrate. A body layer, a translucent heat dissipation layer, a third dielectric layer, and a translucent reflective layer are provided in this order, and a protective coating layer is provided thereon as necessary. On the other hand, for an optical system having a larger objective lens NA in order to obtain a higher density medium, incidence from the film surface side may be preferable. When recording / reproducing laser light is incident from the film surface, The layer structure is the reverse of the above structure. Moreover, even if each of these layers is formed on both sides of the substrate, an optical recording medium having each layer on both sides with the film surface (protective coat layer) inside can be obtained.
Further, when the optical recording medium of the present invention is used as a recording medium unit of a multilayer optical recording medium in which two or more recording media are laminated, for example, when incident light is performed from the substrate side, A substrate, a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat dissipation layer, a third dielectric layer, and a translucent reflective layer are laminated in this order, and another optical recording is performed thereon via an adhesive layer. A structure in which medium units are stacked can be adopted. As another optical recording medium unit, a known layer configuration, for example, a phase change optical recording medium having a layer structure in which a dielectric layer, a recording layer, a dielectric layer, and a metal reflection layer are provided in this order can be used. However, the present invention is not limited to these, and various types such as a reproduction-only type, a write-once type, and a magneto-optical type can be used. In addition, sufficient adhesiveness and sufficient thickness (usually 10 μm or more) are required for the adhesive layer.
[0028]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not restrict | limited by these Examples, unless the summary is exceeded.
Prior to performing the example (production of an optical recording medium), the following simulation was performed in order to obtain a recording medium having a large final signal strength and high transmittance.
[0029]
Calculation of optimum film thickness
Optical calculation was performed for five types of film configurations shown in Conditions 1 to 5 described later.
In the calculation, the crystal reflectance, the amorphous reflectance, the crystal transmittance, and the amorphous transmittance are calculated by changing the film thickness of each layer, and (crystal reflectance) − (amorphous reflectance)> 0.1 And a film thickness that maximizes the crystal transmittance (herein, “crystal reflectivity” means the reflectivity of the medium when the phase change recording layer is in the crystalline state).
[0030]
Conditions 1 to 5 are as follows.
Condition 1:
It was assumed that the substrate, the dielectric layer 1, the recording layer, the dielectric layer 2, and the ultraviolet curable resin layer were provided in this order. The calculated thicknesses of the dielectric 1 were 0 to 160 nm in increments of 5 nm, the recording layer was 3 to 15 nm in increments of 2 nm, and the dielectric 2 was 0 to 160 nm in increments of 5 nm. Regarding the dielectric film thickness, the optical properties change periodically, but the film thickness range corresponding to approximately one period is set in the calculation conditions. The calculated film thickness range of the recording layer was set in the vicinity of the aforementioned preferable film thickness range.
[0031]
Condition 2:
The case where the board | substrate, the dielectric material layer 1, the recording layer, the dielectric material layer 2, the translucent heat dissipation layer, and the ultraviolet curable resin layer was provided in order was assumed. The calculated thicknesses of dielectric 1 were 0 to 160 nm in increments of 5 nm, the recording layer was 3 to 15 nm in increments of 2 nm, dielectric 2 was 5 to 20 nm in increments of 5 nm, and the translucent heat dissipation layer was 20 nm. The translucent heat radiation layer was assumed to be an Ag film, fixed to 20 nm where a heat radiation effect could be obtained to some extent, and the transmittance was compared with the case of Condition 4 described later. Since the dielectric 2 needs to be thin to some extent so as to obtain a heat dissipation effect, the calculation range is set to 5 to 30 nm.
[0032]
Condition 3:
The calculation conditions were the same as those in Condition 2 except that the thickness of the semitransparent heat radiation layer was 30 nm. The transmittance was compared with the condition 5 described later.
[0033]
Condition 4:
A case was assumed in which a substrate, a dielectric layer 1, a recording layer, a dielectric layer 2, a translucent heat dissipation layer, a dielectric layer 3, a translucent reflective layer, and an ultraviolet curable resin layer were provided in this order. The calculated thicknesses of the dielectric 1 are 0 to 160 nm in increments of 5 nm, the recording layer is 3 to 15 nm in increments of 2 nm, the dielectric 2 is in increments of 5 to 30 nm and 5 nm, the translucent heat dissipation layer is 20 nm, and the dielectric layer 3 is The semi-transparent reflective layer was set at 0 to 50 nm in increments of 5 nm at 0 to 160 nm.
[0034]
Condition 5:
The calculation conditions were the same as those in Condition 4 except that the thickness of the translucent heat radiation layer was 30 nm.
The complex refractive index of each layer used for the calculation was a value measured at a wavelength of 650 nm using an ellipsometer. (ZnS) as dielectric layer for measurement₈₀(SiO₂)₂₀, Ge as the recording layer_FiveSb₇₁Te_{twenty four}Ag was used as the semitransparent heat dissipation layer and the semitransparent reflective layer. As a result, the dielectric layer was 2.1-0i, the recording layer was 3.8-2.8i in the amorphous state, 2.6-4.7i in the crystalline state, and the heat dissipation layer and the reflective layer were 0.1-4.1i. Met. The substrate and the ultraviolet curable resin layer were 1.5-0i.
[0035]
As shown in Table 1, the transmittance under conditions 4 and 5 is smaller than that under condition 1 where no heat-dissipating layer is provided, but is larger than the transmittance under conditions 2 and 3, and the configuration of the present invention is optically effective. I know that there is.
[0036]
[Table 1]

[0037]
Example
It was shown as follows that an optical recording medium (hereinafter referred to as an optical disk) was actually produced, and the configuration provided with the semitransparent heat dissipation layer was superior in heat dissipation effect to the configuration provided with no translucent heat dissipation layer.
ZnS-SiO on a polycarbonate substrate with a thickness of 0.6 mm₂First dielectric layer (55 nm), Ge_FiveSb₇₁Te_{twenty four}Recording layer (10 nm), ZnS-SiO₂Second dielectric layer (5 nm), SiO₂Diffusion prevention layer (2 nm), Ag translucent heat dissipation layer (20 nm), SiO₂Diffusion prevention layer (2nm), ZnS-SiO₂Third dielectric layer (90 nm), SiO₂Diffusion prevention layer (2 nm), Ag translucent reflection layer (15 nm), SiO₂An anti-diffusion layer (2 nm) was produced by a sputtering method, and a protective coat made of an ultraviolet curable resin was further formed thereon (Example). The substrate groove width is 0.35 μm, the groove depth is 33 nm, and the groove pitch is 0.74 μm. The film thickness of the recording layer was experimentally set to a film thickness (10 nm) to facilitate initial crystallization.
[0038]
After the initial crystallization of this optical disk, the recording characteristics were measured using an optical disk evaluation apparatus having an optical system with a wavelength of 635 nm and NA of 0.6. The recording conditions were a linear velocity of 4 m / s, a ratio Pe / Pw = 0.5 of erase power Pe and recording power Pw, a clock period of 38.2 ns, and an 8-16 modulated random signal in the groove using the pulse train method. Recorded. FIG. 1 shows the measurement result of the power dependency of edge to clock jitter after 10 direct overwrites (DOW). As the jitter value, a value normalized by the clock cycle was used.
[0039]
The transmittance of this optical disk was 30% when the recording layer was in the mirror state and the recording layer was 37% when the recording layer was in the amorphous state. The transmittance is calculated when R1 is a value when the amount of reflected light from a 120 nm thick Ag film is measured through a 0.6 mm polycarbonate substrate, and R2 is a value when measured through the optical disk. R2 / R1)^1/2It was obtained from the formula of This result shows that the recording layer may be thicker than the calculated value (5 nm), and the transmittance of the optical disc is not necessarily sufficiently high, but it clearly shows the possibility of a two-layer recording medium.
[0040]
Comparative Example 1
ZnS-SiO on a polycarbonate substrate with a thickness of 0.6 mm₂Dielectric layer (105 nm), Ge_FiveSb₇₁Te_{twenty four}Recording layer (10 nm), ZnS-SiO₂A dielectric layer (115 nm) was produced by a sputtering method, and a protective coat made of an ultraviolet curable resin was further formed thereon (Comparative Example 1). This optical disk was evaluated for the same recording characteristics as described above. As a result, a recording mark capable of measuring jitter was not formed with a recording power of 8 to 14 mW. This optical disk is designed so that sufficient signal strength is obtained when an amorphous mark is formed. The reason why a recording mark cannot be made is that heat radiation is insufficient, and that part is recrystallized after melting. It seems to be because.
From the above, it can be seen that the heat dissipation effect in the example is sufficiently larger than that in Comparative Example 1. If the recording layer is made thinner in order to further increase the transmittance, it is considered that a more efficient heat dissipation effect can be obtained because the amount of heat to be released becomes smaller.
[0041]
Comparative Example 2
ZnS-SiO on a polycarbonate substrate with a thickness of 0.6 mm₂Dielectric layer (55 nm), Ge_FiveSb₇₁Te_{twenty four}Recording layer (10 nm), ZnS-SiO₂Dielectric layer (5 nm), SiO₂Diffusion prevention layer (2 nm), Ag translucent heat dissipation layer (20 nm), SiO₂A diffusion prevention layer (2 nm) was produced by a sputtering method, and a protective coating made of an ultraviolet curable resin was further formed thereon (Comparative Example 2). The transmittance of this optical disk was 16% when the recording layer was in the mirror state and the recording layer was 20% when the recording layer was in an amorphous state.
[0042]
【The invention's effect】
In the optical information recording medium having the layer structure of the present invention, it is possible to sufficiently increase all of the signal intensity, the heat dissipation effect, and the transmittance, and in particular, to a multilayered recording medium for higher density. Is expected to be applied.
[Brief description of the drawings]
FIG. 1 shows a measurement result of power dependency of edge to clock jitter in an embodiment.

Claims (9)

At least a first dielectric layer, recording layer, second dielectric layer, a semi-transparent heat radiating layer composed mainly of metal and third dielectric layer, and a semi-transparent reflective layer possess in this order and transmittance 20 % Or more of an optical information recording medium. An optical information recording medium in which two or more recording media are laminated , wherein at least one recording medium is at least a first dielectric layer, a recording layer, a second dielectric layer, and a half mainly composed of metal. An optical recording medium having a transparent heat dissipation layer, a third dielectric layer, and a translucent reflective layer in this order and having a transmittance of 20% or more, and another optical recording medium is laminated on the optical recording medium An optical information recording medium characterized by the above . 3. The optical information recording medium according to claim 1, wherein the translucent heat radiation layer is made of a material mainly composed of silver. The optical information recording medium according to any one of claims 1 to 3, wherein the thickness of the translucent heat radiation layer is 2 to 50 nm. The optical information recording medium according to claim 1, wherein the second dielectric layer has a thickness of 30 nm or less. [Λ / (8n)] <d <[λ / (2n)] where d is the thickness of the third dielectric layer, n is the refractive index, and λ is the laser wavelength used, and the translucent reflective layer The optical information recording medium according to claim 1, wherein the optical recording medium is made of a metal-based material. 7. The optical information recording medium according to claim 1, wherein the recording layer is a phase change recording layer. An optical information recording medium in which two or more recording media are laminated, and includes at least a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat dissipation layer mainly composed of metal, and a third dielectric. 3. An optical recording medium according to claim 2 , wherein an optical recording medium having a body layer and a translucent reflective layer in this order and having a transmittance of 20% or more is provided close to the incident light side. Information recording medium. The translucent heat dissipation layer and the translucent reflection layer are made of a metal material mainly composed of silver, and the thickness of the translucent reflection layer is equal to or less than the thickness of the translucent heat dissipation layer. The optical information recording medium according to claim 8.

Images