JP2002025115A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium having a satisfactory transmittance and a heat releasing effect necessary for the formation of a recording mark and useful for a multilayered recording medium. SOLUTION: The optical information recording medium has at least a first dielectric layer, a recording layer, a second dielectric layer, a metal-base translucent heat releasing layer, a third dielectric layer and a translucent reflecting layer in this order, A multilayered optical information recording medium including the optical information recording medium having >=20% transmittance is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 which has a high transmittance and is expected to be used for a multilayer recording medium in which a plurality of optical recording media are stacked.

[0002]

2. Description of the Related Art With the increase in the amount of information, a recording medium capable of recording and reproducing a large amount of data at a high density and at a high speed has been demanded. An optical recording medium is one of recording media which can meet such a purpose. It is expected as. Optical recording media include a write-once type, which allows recording only once, and a rewritable type, which allows recording / erasing to be repeated any number of times. As rewritable optical recording media, magneto-optical recording media utilizing the magneto-optical effect,
A phase-change type recording medium using a change in reflectivity accompanying a change in a reversible crystalline-amorphous state is exemplified. A phase-change recording medium usually has a layer structure in which a dielectric layer, a recording layer, a dielectric layer, and a metal reflection layer are provided in this order. The metal reflection layer is used to promote heat diffusion to enhance the heat dissipation effect and more stably form the amorphous mark, and is also called a metal heat dissipation layer. Therefore, the metal heat dissipation layer is important for obtaining a sufficient heat dissipation effect required for forming an amorphous phase, and is usually formed of a material mainly composed of a metal having high reflectance and high thermal conductivity. Also, the dielectric layer provided between the recording layer and the metal heat dissipation layer promotes heat diffusion from the recording layer during recording and contributes to the formation of amorphous marks, and acts as a heat storage layer during erasure, thus controlling the heat dissipation effect. It is important to.

In recent years, in order to record and reproduce an enormous amount of information at a high speed, a multilayer recording medium has been studied with the aim of further increasing the density. That is, this is an attempt to increase the recording density by stacking and manufacturing two or more optical recording media at a distance greater than the depth of focus 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 units other than the recording medium unit farthest from the incident direction of the laser light need to transmit the laser light. In order to transmit laser light, it is preferable that the metal heat radiation layer is basically not used in a recording medium unit requiring light transmission, and when used, the metal heat radiation layer is thin enough to obtain sufficient light transmission. It is necessary.

However, when the metal heat radiation layer is not provided or is thin, the heat radiation effect becomes insufficient. Therefore, when the recording medium unit requiring light transmittance is a phase-change type recording medium, there is a problem that a portion where an amorphous material is to be formed is recrystallized when cooled after being melted, and the formation of an amorphous mark becomes insufficient. is there. If the crystallization rate is reduced by changing the composition of the recording layer to prevent recrystallization, the crystallization of the amorphous mark in the erasing portion of the erasing laser will be insufficient. That is, the range of the crystallization speed that can be used as a rewritable recording medium is narrowed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a recording medium having a sufficient transmittance required for a recording medium unit which can be used for multilayering a recording medium. An object of the present invention is to achieve both a sufficient heat radiation effect necessary for forming a recording mark. In order to increase the heat radiation effect, the metal heat radiation 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 is reduced. As a result of studying the control of the film thickness and the amount of transmitted light of the metal heat dissipation layer, the present inventors have found that improvement can be achieved by further providing a dielectric layer and a translucent reflection layer on the metal heat dissipation layer, and completed the present invention.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an optical information recording medium which can be used for multi-layering a recording medium, and particularly to an optical information recording medium which is expected to be used as a recording medium unit which requires light transmittance. The present invention provides at least a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat-radiating layer mainly composed of a metal, a third dielectric layer,
And a translucent reflective layer in this order. Another gist of the present invention is that at least a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat radiation layer mainly composed of a metal, a third dielectric layer, and a translucent reflective layer are arranged in this order. An optical information recording medium comprising two or more recording media having a transmittance and a transmittance of 20% or more.

According to a preferred aspect of the present invention, in the above-mentioned optical information recording medium, the translucent heat radiation layer is made of a material containing silver as a main component, and has a thickness of 2 to 50 nm. When the thickness of the dielectric layer is 30 nm or less, the thickness of the third dielectric layer is d, the refractive index is n, and the laser wavelength used is λ, [λ / (8n)] <d <[λ / (2
n)], and the semi-transparent reflective layer is a material mainly composed of a metal, and the recording layer is a phase-change type recording layer. Further, in an optical information recording medium in which two or more recording media are laminated, the optical recording medium having a transmittance of 20% or more is provided close to the incident light side, The transparent reflective layer
As a preferred embodiment, it is made of a metal material containing silver as a main component, and the thickness of the translucent reflective layer is set to be equal to or less than the thickness of the translucent heat radiation layer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the optical information recording medium of the present invention comprises at least a first dielectric layer, a recording layer, a second dielectric layer, a semi-transparent heat radiation layer mainly composed of metal,
It has a third dielectric layer and a translucent reflective layer in this order. In particular, as a recording medium unit constituting a multilayer recording medium, at least a first dielectric layer, a recording layer, a second
An optical recording medium having a dielectric layer, a translucent heat radiation layer mainly composed of a metal, a third dielectric layer, and a translucent reflective layer in this order, and having a transmittance of 20% or more. Generally, a dielectric layer,
The metal heat radiating layer of the phase change recording medium composed of the recording layer, the dielectric layer and the metal heat radiating layer is required to have a high heat radiating effect, and therefore has a certain thickness to sufficiently exhibit the effect. are doing. However, with such a film thickness having an effective heat dissipation effect, the reflectance to laser light is high, and the light transmittance as a recording medium becomes small. It was not applicable as a recording medium unit, and it was generally thought that a metal heat dissipation layer could not be provided in the case of a recording medium unit.

The recording medium of the present invention has the above-mentioned layer structure. By appropriately adjusting the film thickness of the metal heat dissipation layer, and further adding a dielectric layer for phase adjustment and a translucent reflection layer to cause multiple reflection. As a result, it is based on the 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 term “semi-transparent” means that the film usually has a light transmittance of 3% or more. "Translucent heat dissipation layer" of the present invention
And the light transmittance of the “translucent reflective layer” is preferably 3% or more, particularly preferably 5% or more, and more preferably 10% or more.
%, Most preferably 15% or more. The transmittance is
It can be calculated from the complex refractive index and the film thickness for the light of the used wavelength. The light transmittance of the “recording medium” of the present invention is usually 20% or more, preferably 30% or more.

As described above, the present invention utilizes multiple reflection to reduce the amount of reflected light and increase the amount of transmitted light.
In such a case, the translucent heat dissipation layer and the translucent reflection layer tend to absorb light easily. Therefore, it is preferable to select a material that absorbs as little light as possible as a material constituting the translucent heat radiation layer and the translucent reflection layer. Although the translucent heat radiation layer has a certain amount of transmitted light as described above, it 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 radiation effect with a relatively thin film thickness, the material used as the translucent heat radiation layer needs to have a sufficiently large thermal conductivity. As a material having a high thermal conductivity, a metal mainly composed of Ag, Au, Al, Cu, or the like can be given. Among them, the one with the largest thermal conductivity is A
Because of g, Ag is most preferable in terms of thermal conductivity.

On the other hand, in consideration of light absorption, Ag is most preferable among the above metals. Especially at short wavelengths, Au, Cu,
Al is easier to absorb light than Ag,
When a short wavelength laser of 0 nm or less is used, it is particularly preferable to use Ag. Further, Ag is relatively inexpensive as a sputtering target, is stable in discharge, has a high film-forming speed, and is stable in the air, which is preferable in terms of productivity and economy. Therefore, Ag is the most preferable material for the translucent heat radiation layer as a whole. Further, metal Ag, A as a material main component capable of forming a translucent heat radiation layer
1, Au and Cu have the disadvantage that when mixed with impurities, the thermal conductivity is reduced and the light absorption is increased, but the stability and the film surface flatness are sometimes improved, and 5 at. % Or less. As impurity elements, Cr, Mo, Mg, Zr, V, Ag, In, G
a, Zn, Sn, Si, Cu, Au, Al, Pd, P
t, Pb, Cr, Co, O, Se, V, Nb, Ti,
O, N and the like can be mentioned.

The optimum film thickness of the translucent heat radiation layer varies depending on the material used and the laser wavelength used. When the material is Ag and the laser wavelength is around 400 to 650 nm, the film thickness is 2 to 50 nm. The degree is good, more preferably 5 to 30 nm. If the thickness is less than 2 nm, the heat radiation effect is reduced, while if it is greater than 50 nm, the amount of transmitted light is undesirably small. Since the absolute value of the imaginary part of the complex refractive index becomes small at a short wavelength of Ag, even at the same film thickness, the transmittance tends to be larger at a shorter wavelength. Therefore, a balance between a sufficient heat radiation effect and a sufficient transmittance tends to be more easily achieved at a short wavelength, and the effect of the present invention becomes more advantageous at a short wavelength. However, the signal intensity of the recording layer of the phase change optical disk tends to decrease at short wavelengths.

When an interaction such as element diffusion occurs between the translucent heat radiation layer and the second or third dielectric layer due to a material forming these layers, the interface between the heat radiation layer and the dielectric layer is formed. It is preferable to further provide a diffusion prevention layer and the like. Preferred examples of the material for the diffusion preventing layer include silicon oxide, silicon nitride, silicon carbide, tantalum oxide, cerium oxide, lanthanum oxide, yttrium oxide, aluminum oxide, and silver oxide. Note that diamond is a preferable material for the heat dissipation layer because it has higher thermal conductivity and can be transparent, but has a problem in film formation.

The translucent reflective layer is provided on the translucent heat radiating layer with the third dielectric layer interposed therebetween. Since the transflective layer is slightly distant from the recording layer, a large heat radiating effect cannot be expected. It is important that the translucent reflective layer has a certain degree of optical reflectivity and low light absorption. When the translucent reflective layer is formed from a material containing a metal as a main component, since this condition is also a necessary condition for the translucent heat dissipation layer, a preferable material used for the translucent heat dissipation layer is a metal translucent reflection layer. It can be used as Ag, Au, Al, C
Ag is the most preferable metal material mainly containing u or the like.

The optimum thickness of the translucent reflective layer 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 thickness is preferably about 50 nm or less. . If the thickness is larger than 50 nm, the amount of transmitted light is small, and the transmittance of the entire recording medium is reduced. In some cases, it is not suitable for use as a recording medium unit in a multilayer recording medium. The optimum thickness of the translucent reflective layer is related to the thickness of the translucent heat dissipation layer, etc., and varies depending on the mutual material and the wavelength of the laser used. In many cases, the thickness is good. However, if the thickness is too thin, the characteristics of the recording medium and manufacturing difficulties are involved, so that the thickness is usually 1 nm or more. When an interaction such as element diffusion occurs between the translucent reflective layer and the third dielectric layer or between the translucent reflective layer and an ultraviolet curable resin layer or an adhesive layer provided thereon as necessary. It is preferable to further provide a diffusion prevention layer or the like at the interface between the respective layers. As the material of the diffusion prevention layer, the material used for the diffusion prevention layer provided between the translucent heat radiation layer and the dielectric layer can be used.

As the translucent reflection layer, two layers having different refractive indexes are used.
A dielectric mirror manufactured by laminating more than two kinds of transparent dielectric layers 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 reflection layer is obtained and the absorption is small. Examples of the dielectric mirror include a laminated film of ZnS—SiO ₂ and SiO ₂ . It is preferable that the dielectric mirrors are laminated such that the laser wavelength to be 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 the time required for fabrication and the complexity of the fabrication apparatus as compared with the metal translucent reflective layer, and may also have a problem in storage stability.

A dielectric layer (third dielectric layer) provided between the translucent heat radiation layer and the translucent reflection layer has a role of adjusting the phase at the time of 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, metal and semiconductor oxides, sulfides, nitrides and Ca, which are highly transparent and have a high melting point,
A fluoride such as Mg or Li can be used. These oxides, sulfides, nitrides, and fluorides do not always need to have a stoichiometric composition, and it is effective to control the composition for controlling the refractive index and the like, or to use a mixture thereof. More specifically, ZnS or rare earth sulfide and oxide, nitride,
A mixture of a heat-resistant compound such as a carbide may be used, and a dielectric mixture is preferable in consideration of repetitive recording characteristics.

Specifically, sulfides such as zinc sulfide, tantalum sulfide, and rare earth (Y, La, Ce, Nd, etc.) sulfides are used alone or as a mixture in an amount of 20 mol% to 90 mol%.
% Is preferable. The balance of the mixture is preferably a heat-resistant compound having a melting point or decomposition temperature of 1000 ° C. or higher. As a heat-resistant compound having a melting point or a decomposition temperature of 1000 ° C. or more, Mg, Ca, Sr, Y, La, Ce, Ho, Er, Yb, Ti, Zr, H
Examples thereof include oxides such as f, V, Nb, Ta, Zn, Al, Si, Ge, and Pb, nitrides, carbides, and fluorides such as Ca, Mg, and Li. Of these, a mixture of ZnS and SiO ₂ is often used for 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, No. 27).
8 (1996), pp. 74-81).

The preferred thickness of the third dielectric layer is a dielectric,
It varies depending on the material and thickness of the translucent heat radiation layer, the translucent reflection layer, etc., the used laser wavelength, and the like. In the layer structure of the recording medium of the present invention, the phenomenon is complicated because multiple reflection occurs when both the transmittance and the reflectance of the translucent heat radiation layer and the translucent reflection layer are large to some extent. When the layer is made of a material mainly composed of a metal, the 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 including the translucent heat dissipation layer, the third dielectric layer, and the translucent reflection layer, it is considered effective to reduce the reflectance in this portion. For this purpose, the phase of the light reflected by the translucent heat dissipation layer and the phase of the light transmitted through the translucent heat dissipation layer, reflected by the translucent reflection layer, and transmitted again through the translucent heat dissipation layer are shifted by a half wavelength. I think it would be good to cancel each other out. That is, when the thickness of the third dielectric layer is d, the refractive index is n, and the used laser wavelength is λ, it is considered that there is a suitable range around d = λ / (4n). Actually, even if the value slightly deviates from this value due to the effect of multiple reflection or the effect of the film thickness of the translucent heat dissipation layer and the translucent reflection layer, the film thickness (d) of the third dielectric layer is
[Λ / (8n)] <d <[λ / (2n)] is preferable.

The second dielectric layer is provided between the recording layer and the translucent heat radiation layer, and this dielectric layer has a role of controlling heat flowing from the recording layer to the translucent heat radiation layer. The thickness of the second dielectric layer is preferably about 2 to 30 nm, more preferably 5 to 30 nm.
２０20 nm. When the thickness is more than 30 nm, the heat radiation effect becomes insufficient. On the other hand, when the thickness is less than 2 nm, the recording sensitivity deteriorates, and furthermore, element diffusion between the recording layer and the translucent heat radiation layer occurs, which is not preferable. . As the material of the second dielectric layer, the same material as that used for the third dielectric layer provided between the translucent heat radiation layer and the translucent reflection layer can be used.

The first dielectric layer is provided so as to cover the upper and lower portions 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. . First
The dielectric layer needs to suppress deformation of the substrate due to heat, and the thickness thereof is preferably 30 nm or more. If it is less than 30 nm, microscopic substrate deformation is accumulated during repeated overwriting, and the reproduction light is scattered, so that the noise rises significantly. 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 between the dielectric layer and the substrate become significant, and cracks are likely to occur. Although the upper limit is substantially about 200 nm from the relation of the film formation time, it is not preferable that the thickness is larger than 200 nm because the groove shape seen on the recording layer surface changes. More preferably, it is 150 nm or less.
As the material of the first dielectric layer, the same material as that used for the third dielectric layer provided between the translucent heat radiation layer and the translucent reflective layer can be used.

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, GeSb
Te, InSbTe, AgSbTe, AgInSbTe
Are selected as overwritable materials. Among them, ｛(Sb ₂ Te ₃ ) _1-x (GeT
_{e) x} 1-y Sb} y alloy (wherein, 0.2 <x <0.9,
0 ≦ y <0.1) or (Sb _x Te _1-x ) _y M _1-y alloy (where 0.6 <x <0.9, 0.7 <y <1, M is Ge, Ag , In, Ga, Zn, Sn, Si, Cu, A
u, Pd, Pt, Pb, Cr, Co, O, S, Se,
The thin film mainly containing at least one selected from V, Nb, and Ta) is stable in both crystalline and amorphous states, and is capable of high-speed phase transition between the two states. Furthermore, it has the advantage that segregation hardly occurs when repeated overwriting is performed, and is the most practical material. The recording layer is made of (Sb _x Te _1-x ) _y M _1-y alloy (where 0.6 <x <
0.9, 0.7 <y <1, M is Ge, Ag, In, G
a, Zn, Sn, Si, Cu, Au, Pd, Pt, P
b, Cr, Co, O, S, Se, V, Nb, and Ta) as the main components, the difference in heat distribution is easily reflected in the mark shape. This is particularly important in the present invention.

When the recording layer is a phase change type optical recording layer, its thickness is preferably in the range of 3 nm to 15 nm. If the thickness of the recording layer is less than 3 nm, it is difficult to obtain a sufficient contrast, and initial crystallization tends to be difficult. On the other hand 15nm
If it exceeds, it is difficult to obtain a sufficient transmittance, which is not preferable. More preferably, it is 5 to 10 nm.

The above-mentioned recording layer is often obtained by sputtering an alloy target in an inert gas, particularly Ar gas. The thicknesses of the recording layer and the dielectric layer are good for the absorption efficiency of the laser light, taking into account the interference effect associated with the multilayer structure, in addition to the mechanical strength and the limitation in terms of reliability. The amplitude is selected so that the contrast between the recorded state and the unrecorded state is increased.

In the optical recording medium of the present invention, a transparent resin such as polycarbonate, acrylic, or polyolefin, or glass can be used as the substrate. Of these, polycarbonate is preferred because it has a proven track record and is inexpensive and excellent in economic efficiency. The thickness of the substrate is usually 0.
It is from 0.5 to 5 mm, preferably from 0.1 to 2 mm.

The recording layer, the first to third dielectric layers, the translucent heat radiation layer, the translucent reflection layer, the diffusion preventing 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 target for a recording film, a target for a dielectric film, and a target for a reflective layer material, if necessary, are installed in the same vacuum chamber. It is desirable in preventing oxidation and contamination between layers. It is also excellent in terms of productivity.

The layer structure of the optical recording medium of the present invention is, for example,
When a recording / reproducing laser beam is incident from the substrate side and used, basically, a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat radiation layer, and a third dielectric layer are formed on the substrate. A translucent reflective layer is provided in this order, and a protective coat layer is provided thereon if necessary. On the other hand, for an optical system with a larger objective lens NA in order to obtain a higher density medium, incidence from the film surface side may be preferable, and when recording / reproducing laser light is incident from the film surface, , The layer structure is opposite to the above structure. In some cases, even if these layers are formed on both sides of the substrate, an optical recording medium having each layer on both sides with the film surface (protective coating layer) inside may be used. 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 stacked, for example, when incident light is emitted from the substrate side, A substrate, a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat radiation 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 the medium units are stacked can be adopted. As another optical recording medium unit, a phase change type optical recording medium having a known layer structure, for example, 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 read-only type, a write-once type, and a magneto-optical type can be used. The adhesive layer is required to have a sufficient light transmittance and a sufficient thickness (normally, 10 μm or more).

[0028]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof. 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 high signal intensity and a high transmittance, which is a final target.

Calculation of Optimum Film Thickness Optical calculation was performed for five types of film constitutions shown in the following conditions 1 to 5. In the calculation, the crystal reflectance, the amorphous reflectance, the crystal transmittance, and the amorphous transmittance were calculated by changing the thickness of each layer, and (crystal reflectance) − (amorphous reflectance)> 0.1 And a film thickness that maximizes the crystal transmittance was obtained (here, “crystal reflectance” means the reflectance of the medium when the phase-change recording layer is in a crystalline state).

Conditions 1 to 5 are as follows. Condition 1: It is assumed that a substrate, a dielectric layer 1, a recording layer, a dielectric layer 2, and an ultraviolet curable resin layer are sequentially provided. The calculated film 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, and the dielectric 2 is 0 to 160 n.
m in steps of 5 nm. Regarding the dielectric film thickness, the optical properties change periodically, but the film thickness was set to a film thickness range corresponding to approximately one cycle under the calculation conditions. The calculated thickness range of the recording layer was around the above-mentioned preferred thickness range.

Condition 2: It is assumed that a substrate, a dielectric layer 1, a recording layer, a dielectric layer 2, a translucent heat radiation layer, and an ultraviolet curable resin layer are sequentially provided. The calculated film thickness is 0-16 for dielectric 1.
The recording layer was 3 nm in increments of 2 nm, the dielectric 2 was 5 nm in increments of 5 nm, and the translucent heat radiation layer was 20 nm. The translucent heat radiation layer was assumed to be an Ag film, and was fixed at 20 nm where a heat radiation effect was likely to be obtained to some extent, and the transmittance was compared with the case of Condition 4 described later. Dielectric 2
It is necessary to make the film thickness thin to some extent so as to obtain a heat radiation effect, so the calculation range was 5 to 30 nm.

Condition 3: The calculation conditions were the same as those in Condition 2, except that the thickness of the translucent heat radiation layer was 30 nm. The transmittance was compared with the condition 5 described below.

Condition 4: It is assumed that a substrate, a dielectric layer 1, a recording layer, a dielectric layer 2, a translucent heat radiation layer, a dielectric layer 3, a translucent reflective layer, and an ultraviolet curable resin layer are sequentially provided. The calculated film thickness is as follows. The dielectric 1 has a thickness of 0 to 160 nm in increments of 5 nm, the recording layer has a thickness of 3 to 15 nm in increments of 2 nm, and the dielectric 2 has a thickness of 5 to 30 n.
m in 5 nm increments, the translucent heat dissipation layer is 20 nm, and the dielectric layer 3
Is from 0 to 160 nm in increments of 5 nm, and the translucent reflective layer is from 0 to 5
It was set at 0 nm in 5 nm steps.

Condition 5: The same calculation conditions as in Condition 4 were used except that the thickness of the translucent heat radiation layer was 30 nm. In addition,
As the complex refractive index of each layer used in the calculation, a value actually measured at a wavelength of 650 nm using an ellipsometer was used. For the measurement, (ZnS) ₈₀ (SiO ₂ ) ₂₀ was used as the dielectric layer, Ge ₅ Sb ₇₁ Te ₂₄ was used as the recording layer, and Ag was used as the translucent heat dissipation layer and the translucent reflection layer. As a result, the dielectric layer was 2.1-0i, the recording layer was 3.8-2.8i in an amorphous state, 2.6-4.7i in a crystalline state, and the heat radiation layer and the reflection layer were 0.1-4.1i.
Met. The substrate and the ultraviolet curable resin layer were 1.5-0i.

As shown in Table 1, the calculation results are as shown in Tables 4 and 5.
Is smaller than the condition 1 without the heat radiation layer, but is larger than the transmittance under the conditions 2 and 3, indicating that the configuration of the present invention is optically effective.

[0036]

[Table 1]

EXAMPLE The following describes that an optical recording medium (hereinafter, referred to as an optical disk) is actually manufactured and provided with a translucent heat radiation layer is more excellent in heat radiation effect than a structure without a translucent heat radiation layer. And shown. ZnS-SiO ₂ first dielectric layer on a polycarbonate substrate having a thickness of 0.6mm (55nm), Ge ₅ Sb
₇₁ Te ₂₄ recording layer (10 nm), ZnS-SiO ₂ second dielectric layer (5 nm), SiO ₂ diffusion prevention layer (2 nm), Ag
Translucent heat radiation layer (20 nm), SiO ₂ diffusion prevention layer (2n
m), ZnS—SiO ₂ third dielectric layer (90 nm), Si
O ₂ diffusion prevention layer (2 nm), Ag translucent reflection layer (15 n
m), a SiO ₂ diffusion preventing layer (2 nm) was formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied 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 thickness of the recording layer was experimentally set to be 10 nm in order to facilitate initial crystallization.

After initial crystallization of the optical disk, recording characteristics were measured using an optical disk evaluation apparatus having an optical system with a wavelength of 635 nm and an NA of 0.6. The recording conditions were a linear velocity of 4 m / s, a ratio Pe between the erasing power Pe and the recording power Pw.
/Pw=0.5, the clock cycle is 38.2 ns, and 8
A -16 modulated random signal was recorded in the groove using the pulse train method. 10 direct overwrites (DO
FIG. 1 shows a measurement result of the power dependency of the Edge to clock jitter after W). As the jitter value, a value standardized by the clock cycle was used.

The transmittance of this optical disk was 30% when the recording layer was in a crystalline state at the mirror surface and 37% when the recording layer was in an amorphous state. The transmittance was calculated as follows: when the value of the amount of light reflected from the Ag film having a thickness of 120 nm measured through a 0.6 mm polycarbonate substrate was R1, and when the value measured through the optical disk was R2, the transmittance was (= R2 / R1) ^1/2 . The result is
Although the recording layer may be thicker than the calculated value (5 nm), the transmittance of the optical disk is not necessarily large enough.
Clearly, it shows the potential of a two-layer recording medium.

COMPARATIVE EXAMPLE 1 ZnS-S was placed on a polycarbonate substrate having a thickness of 0.6 mm.
iO ₂ dielectric layer (105 nm), Ge ₅ Sb ₇₁ Te ₂₄ recording layer (10 nm), ZnS—SiO ₂ dielectric layer (115 n)
m) was prepared by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon (Comparative Example 1). This optical disc was evaluated for the same recording characteristics as described above. As a result, at a recording power of 8 to 14 mW, a recording mark capable of measuring jitter was not formed. This optical disk is designed so that a sufficient signal intensity is obtained when an amorphous mark is formed. The reason for the inability to record a mark is insufficient heat radiation, so that the portion is recrystallized after melting. It seems to be. From the above, it can be seen that the heat radiation effect in the example is sufficiently large as compared with the comparative example 1. When the recording layer is made thinner in order to further increase the transmittance, the amount of heat to be released is reduced, so that it is considered that a more efficient heat dissipation effect can be obtained.

Comparative Example 2 ZnS-S was placed on a 0.6 mm thick polycarbonate substrate.
iO ₂ dielectric layer (55 nm), Ge ₅ Sb ₇₁ Te ₂₄ recording layer (10 nm), ZnS—SiO ₂ dielectric layer (5 nm), S
iO ₂ diffusion prevention layer (2 nm), Ag translucent heat dissipation layer (20
nm) and a SiO ₂ diffusion preventing layer (2 nm) were formed by a sputtering method, and a protective coat made of an ultraviolet curable resin was further applied thereon (Comparative Example 2). The transmittance of this optical disk is 16 when the recording layer is in a crystalline state at the mirror surface.
%, And 20% when the recording layer was in the amorphous state, which was smaller than the transmittance of the example.

[0042]

According to the optical information recording medium having the layer structure of the present invention, it is possible to sufficiently increase the signal intensity, the heat radiation effect, and the transmittance, and in particular, to increase the density. The application to multilayer recording media is expected.

[Brief description of the drawings]

FIG. 1 shows a measurement result of power dependency of Edge to clock jitter in an embodiment.

Claims (9)

[Claims] At least a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat radiation layer mainly composed of a metal, a third dielectric layer, and a translucent reflective layer are provided in this order. Characteristic optical information recording medium. 2. It has at least a first dielectric layer, a recording layer, a second dielectric layer, a translucent heat radiation layer mainly composed of metal, a third dielectric layer, and a translucent reflective layer in this order. An optical information recording medium in which two or more recording media are stacked, the optical information recording media including an optical recording medium having a transmittance of 20% or more. 3. The optical information recording medium according to claim 1, wherein the translucent heat radiation layer is made of a material containing silver as a main component. 4. The optical information recording medium according to claim 1, wherein the thickness of the translucent heat radiation layer is 2 to 50 nm. 5. The optical information recording medium according to claim 1, wherein the thickness of the second dielectric layer is 30 nm or less. 6. The film thickness of the third dielectric layer is d, the refractive index is n,
When the used laser wavelength is λ, [λ / (8n)] <d
<[Lambda] / (2n)], and the translucent reflective layer is made of a material mainly composed of a metal.
The optical information recording medium according to any one of claims 1 to 5, wherein 7. The optical information recording medium according to claim 1, wherein the recording layer is a phase change type recording layer. 8. The optical information recording medium according to claim 2, wherein the optical recording medium is provided close to the incident light side. . 9. The translucent heat radiation layer and the translucent reflection layer are made of a metal material containing silver as a main component, and the thickness of the translucent reflection layer is equal to or less than the thickness of the translucent heat radiation layer. The optical information recording medium according to claim 1.