JP2006142673A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which is excellent in storage reliability and enables four-or-higher-speed recording with a recording density corresponding to DVD. <P>SOLUTION: The optical recording medium has a constitution wherein at least a lower protective layer, a recording layer formed of a phase change material, an upper protective layer and a reflection layer, and rewriting recording is performed therein by that the recording layer brings about a phase change between a crystalline phase and an amorphous phase under the irradiation of laser light. The phase change material of the recording layer is expressed by the composition formula: Ga<SB>α</SB>Sb<SB>β</SB>Sn<SB>γ</SB>Ge<SB>δ</SB>Cu<SB>ε</SB>(wherein α, β, γ, δ, ε are atomic ratios). Herein 0.03≤α≤0.10, 0.56≤β≤0.79, 0.10≤γ≤0.24, 0.04≤δ≤0.12, and 0.01≤ε≤0.05 are satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical recording medium using a phase change material.

In recent years, development of optical recording media using a phase change material as a recording layer, particularly phase change optical discs, has been actively conducted.
In general, in a phase change optical disk, a specific groove is formed on a transparent plastic substrate, and a thin film is formed thereon. The plastic material used for the substrate is mainly polycarbonate, and injection molding is often used to form the grooves. The thin film formed on the substrate is a multilayer film, and basically has a lower protective layer, a recording layer, an upper protective layer, and a reflective layer in order from the substrate side. Oxide in the lower and upper protective layer, a nitride, although such sulfides are used, often used ZnS-SiO ₂ mixed inter alia ZnS and SiO _2. A phase change material containing SbTe as a main component is often used for the recording layer. Specific examples include Ge—Sb—Te, In—Sb—Te, Ag—In—Sb—Te, Ge—In—Sb—Te, and Ge—Sn—Sb—Te. -Te, In-Sb, Ga-Sb, Ge-Sb, or the like is used. Although a metal material is used for the reflective layer, metal materials such as Al, Ag, Au, and Cu and alloy materials thereof are often used from the viewpoint of optical characteristics and thermal conductivity.

As a method for forming these multilayer films, various film forming methods such as resistance wire heating method, electron beam evaporation method, sputtering method, and CVD method can be used. Is often used. After forming these multilayer films, the resin layer is coated by spin coating in order to protect the thin film.
In the phase change optical disc manufactured in this way, the phase change material used for the recording layer is in an amorphous state, and it is general to perform a so-called initialization process in which the phase change material is crystallized. The phase change optical disk is initialized by irradiating a laser beam from a semiconductor laser having a width of several μm and a length of several tens to several hundreds of μm while rotating the disk, and moving the laser beam in the radial direction. In many cases, laser beam irradiation is performed more efficiently by providing a focusing function.

The phase change optical disk thus manufactured can form an arbitrary amorphous mark by irradiating an arbitrarily determined laser emission pattern (hereinafter referred to as strategy). Furthermore, direct overwrite (hereinafter referred to as DOW) recording in which erasing and recording are performed simultaneously is possible with a phase change optical disk. Incidentally, erasing is to crystallize an amorphous mark, and recording is to form an amorphous mark from a crystalline state.
As a frequently used strategy, there is a three-value control (Pw>Pe> Pb) of recording power (Pw), erasing power (Pe), and bias power (Pb). This is combined with various pulse widths to record a specific mark length. As the data recording / reproducing modulation system, the EFM modulation used in the CD and the EFM + modulation used in the DVD are mark edge recording systems, and therefore, the control of the mark length is very important. Jitter characteristics are generally used for evaluating the mark length control.

The phase change optical disc as described above is currently widely used as a rewritable medium for DVD. There are three types of DVD rewritable media: DVD-RAM, DVD-RW, and DVD + RW. All of these recording capacities are 4.7 GB, but the recording linear velocities are different. In particular, DVD + RW achieves a maximum recording linear velocity of 14 m / s, which is four times the standard linear velocity of DVD of 3.5 m / s, and is the fastest recording among rewritable DVDs. However, for the purpose of further reducing the data recording time, a medium capable of higher linear velocity recording has been actively developed in each method.
As a method for realizing high linear velocity recording, it is necessary that the phase change material used for the recording layer has a sufficiently high crystallization speed and that a crystalline state can be obtained even at a high linear velocity. The most effective way to increase the crystallization rate of the phase change material is to adjust the phase change material itself.
For example, as a recording layer material used in a rewritable phase change optical disk that has been commercialized so far, Sb-Te series typified by Ag-In-Sb-Te and Ge-Sb-Te are mainly used. However, in this system, a method of increasing the amount of Sb or a method of adding In, Ga, Sn or the like for improving the crystallization speed can be used. However, in these methods, problems such as difficulty in crystallization by initialization and deterioration in storage reliability occur, and a trade-off between these problems and high-speed recording becomes a problem. In particular, this tendency becomes more prominent when the recording density becomes high, and it is very difficult to realize a recording linear velocity of 4 times or more at a recording density equivalent to DVD.

  Under such circumstances, recently, GaSb, GeSb (for example, Patent Documents 1 and 2), InSb (for example, Non-Patent Document 1), SnSb (for example, Patent Document 3), BiGeTe (for example, Patent Document 4) There have been proposals of optical recording media using phase change materials based on materials such as ˜5). However, although both can realize high-speed recording, there are problems that the recording density is low and disk characteristics such as storage reliability and repetitive characteristics have not reached a practical level.

JP 2004-224040 A JP 2004-224041 A JP 2004-203011 A JP 2004-259443 A JP 2004-255889 A Technical Digest ISOM'04 p. 266: “In-Sb Phase-Change Material for 16X DVD-Rewritable Media”

  An object of the present invention is to provide an optical recording medium that solves the above-described problems, has good storage reliability, and can perform high-speed recording at a quadruple speed or higher with a recording density equivalent to a DVD.

The above problems are solved by the following inventions 1) to 5) (hereinafter referred to as the present inventions 1 to 5).
1) A structure in which at least a lower protective layer, a recording layer made of a phase change material, an upper protective layer, and a reflective layer are provided on a light-transmitting substrate, and the recording layer becomes crystalline and amorphous by irradiation with laser light. In an optical recording medium in which rewritable recording is performed by causing a phase change with a phase, the phase change material of the recording layer has the following composition formula (where α, β, γ, δ, and ε are atomic ratios) An optical recording medium characterized by comprising:
GaαSbβSnγGeδCuε
0.03 ≦ α ≦ 0.10
0.56 ≦ β ≦ 0.79
0.10 ≦ γ ≦ 0.24
0.04 ≦ δ ≦ 0.12
0.01 ≦ ε ≦ 0.05
2) The lower protective layer has a thickness of 50 to 100 nm, the recording layer has a thickness of 10 to 20 nm, the upper protective layer has a thickness of 3 to 10 nm, and the reflective layer has a thickness of 100 to 300 nm. 1) The optical recording medium according to 1).
3) The material of the lower protective layer and the upper protective layer in contact with the recording layer is composed of a mixture of ZnS and SiO ₂ , and the mixing ratio of SiO ₂ is in the range of 15 to 35 mol% with the total being 100 mol%. The optical recording medium described in 1) or 2).
4) The optical recording medium according to any one of 1) to 3), wherein an SiO ₂ film is inserted between the lower protective layer and the recording layer, and the thickness thereof is in the range of 1 to 3 nm.
5) The substrate has meandering grooves with a groove pitch of 0.74 ± 0.03 μm, a groove depth of 22 to 50 nm, and a groove width of 0.2 to 0.4 μm. The optical recording medium described.

Hereinafter, the present invention will be described in detail.
The present inventors have so far developed a phase change material obtained by adding Ag, In, Zn, Cu, and Te to GaSbSnGe (Japanese Patent Application No. 2004-29923), and has a recording signal storage characteristic, so-called archival characteristic. It has been confirmed that it will improve. In the present invention, as a content of the storage reliability, the jitter characteristic in the case of recording after storage in an unrecorded state, that is, the so-called shelf characteristic is examined, and as a result, a remarkable improvement effect is obtained with the configuration shown in the present invention 1. I was able to.
Details of the reason why shelf characteristics are improved by adding Cu to GaSbSnGe are unknown, but are considered as follows.
As shelf characteristics, storage stability in an unrecorded state becomes a problem, and thus stability of a crystallized state is important. Cu itself has an atomic radius (metal bond radius) of 1.28Å, and is smaller than Ag (1.44Å), In (1.62Å), Zn (1.33Å), and Te (1.43Å). It is considered that there is an effect of stopping the change of the crystal structure by entering between the lattices of GaSbSnGe. However, this alone makes the crystal state too stable and makes it difficult to form an amorphous mark. In that respect, Cu is 1 having the smallest number of bond coordinations, and this is considered to function to inhibit crystallization and make the crystal state more unstable than necessary. It is important to have these two properties, and this property is considered to be the reason why the shelf properties are not improved even when Ag, which is a similar element, or an element having a small atomic radius is added.

Next, the optimum composition of each constituent element is preferably within the range shown in the present invention 1.
When the Ga compositional amount (atomic ratio) is less than 0.03, the distribution of the reflected signal in the periphery after the initialization deteriorates, and when it exceeds 0.10, the crystallization speed decreases. Deteriorate characteristics. Preferably it is 0.03-0.08, More preferably, it is the range of 0.03-0.05.
When the Sb composition amount (atomic ratio) is less than 0.56, a sufficient crystallization speed cannot be obtained and high-speed recording is impossible, and when it exceeds 0.79, amorphization becomes difficult and good recording characteristics are obtained. I can't. Preferably it is 0.60-0.75, More preferably, it is the range of 0.65-0.70.
If the Sn composition amount (atomic ratio) is less than 0.10, a sufficient crystallization speed cannot be obtained and high-speed recording is impossible, and if it exceeds 0.24, amorphization becomes difficult and good recording characteristics are obtained. In some cases, the reflectance is lowered and shelf characteristics are deteriorated, which is one of the storage reliability. The range is desirably 0.10 to 0.20, and more desirably 0.10 to 0.18.

When the Ge compositional amount (atomic ratio) is less than 0.04, a decrease in reflectance and shelf characteristics, which are one of the storage reliability, are observed, and when it exceeds 0.12, the crystallization rate is slowed down. High-speed recording is not possible. The range is desirably 0.05 to 0.12, and more desirably 0.08 to 0.10.
When the Cu composition amount (atomic ratio) is less than 0.01, the shelf characteristic, which is one of storage reliability, is deteriorated. When the Cu content is more than 0.05, the crystallization speed is reduced and high-speed recording is impossible. . Desirably, it is in the range of 0.01 to 0.03.
Furthermore, considering that the elements that increase the crystallization speed are Sb and Sn, and the elements that decrease the speed are Ga, Ge, and Cu, adjustments are made within the respective composition ranges to optimize the crystallization speed. It is necessary to do.

Next, the film thickness of each layer is preferably within the range specified in the present invention 2.
The film thickness of the lower protective layer serves to adjust the reflectance of the optical recording medium, and the desirable film thickness range is 50 to 100 nm. If the thickness is less than 50 nm, it is difficult to produce stably because the reflectance fluctuation with respect to the film thickness is large. If the thickness is more than 100 nm, the film formation time becomes long and the productivity of the optical recording medium decreases.
The film thickness of the recording layer is preferably in the range of 10 to 20 nm. If the thickness is less than 10 nm, problems such as repeated recording characteristics are deteriorated. If the thickness is more than 20 nm, the jitter characteristics of the initial recording are deteriorated. More desirably, the thickness is 12 to 18 nm. In the present invention, it has also been found that when the thickness of the lower protective layer is 70 nm or more, good recording characteristics can be obtained even if the thickness of the recording layer is reduced to a minimum of 10 nm. This is presumably because the deterioration of the repetitive recording characteristics caused by the thin recording layer can be prevented by increasing the thickness of the lower protective layer.
The thickness of the upper protective layer is preferably in the range of 3 to 10 nm. If it is thinner than 3 nm, the recording sensitivity is deteriorated or the modulation degree is lowered. On the other hand, if it is thicker than 10 nm, the heat dissipation effect is lost, and the jitter characteristics and the repeated recording characteristics deteriorate. More desirably, it is 5 to 10 nm.
The thickness of the reflective layer is preferably in the range of 100 to 300 nm. More desirably, it is in the range of 120 to 150 nm. If it is thinner than 100 nm, the heat dissipation effect may not be obtained. Further, even if it is thicker than 300 nm, the heat dissipation effect does not change, and a film thickness that is not necessary is simply formed.

As the material of the reflective layer, metals such as Al, Ag, Au, and Cu and alloys thereof can be used from the viewpoint of optical characteristics and thermal conductivity. In particular, in the present invention, since a rapid cooling structure is desirable to enable high-speed recording, Ag having the highest thermal conductivity or an alloy thereof is suitable. In the case where a material containing sulfide is used for the upper protective layer using Ag or an alloy thereof, it is necessary to provide a sulfidation preventive layer between the upper protective layer and the reflective layer, because sulfur sulfiding of Ag due to a sulfur component becomes a problem. is there. For the sulfidation prevention layer, it is necessary to use a material resistant to sulfidation. For example, a metal such as Si or Al, an oxide such as SiO ₂ or TiO ₂ , a nitride such as SiN or AlN, a carbide such as SiC or TiC, Alternatively, a mixture of these is used.
The film thickness of the sulfidation prevention layer is preferably about 2 to 5 nm. More desirably, it is in the range of 3 to 5 nm. This is because if it is thinner than 2 nm, the effect of preventing sulfidation may be lost, and if it is thicker than 5 nm, the heat dissipation effect and optical influence may be increased.

Next, as the material of the lower protective layer and the upper protective layer, the material specified in the present invention 3 is desirable. In the prior art, both protective layers use dielectric materials such as oxides, nitrides, sulfides and carbides, or mixtures thereof, and are composed of a single layer or a plurality of layers. The present inventors have found that recording characteristics can be improved by forming at least a protective layer in contact with the recording layer with a dielectric material made of a mixture of ZnS and SiO ₂ . Although the reason for this is unknown, it is considered as follows.
Since the phase change material used in the present invention has a high crystallization rate, it is considered that the phase change material is instantly crystallized by providing an effect of promoting crystallization. Some protective layer materials have a crystallization promoting effect, and when such a protective layer is in contact with the phase change material, it is considered that the formation of an amorphous state is hindered and the recording characteristics are deteriorated. In particular, during repetitive recording, heat tends to be generated and it tends to be difficult to make amorphous. Therefore, it is considered that a mixture of ZnS and SiO ₂ having a relatively small crystallization promoting effect is suitable.
Further, it has been found that the mixing ratio of SiO ₂ in the protective layer material composed of a mixture of ZnS and SiO ₂ is preferably within the range specified in the present invention 3. More preferably, it is 20-30 mol%. If it is less than 15 mol%, ZnS crystallization will occur due to repeated recording and initialization, thereby inhibiting the recording layer from becoming amorphous. On the other hand, if it exceeds 35 mol%, the refractive index becomes small, and sufficient optical properties cannot be obtained.

Furthermore, with the configuration of the present invention 4, it is possible to improve the repetition characteristics, particularly the jitter characteristics on the high power side. The details of this reason are unknown, but in the case of repeated recording at high power, it is expected that a very large amount of heat is generated in the recording layer, and heat is radiated to the reflective layer side, whereas the substrate side is It is thought that heat is concentrated locally on the lower protective layer side because it is made of a material having a low thermal conductivity. Therefore, it is considered that the characteristics are improved by the effect of mechanical reinforcement. In addition, for this reason, if the film thickness is large, heat damage increases. Therefore, it is desirable that the film be as thin as possible. However, a film having a thickness of less than 1 nm is actually difficult to form. Furthermore, as described above, a material having an effect of promoting crystallization cannot be used.
Considering the above, it is considered that SiO ₂ is most suitable as a material which is amorphous after sputtering film formation and has a sufficient strength even in a film thickness range of 1 to 3 nm.

  DVD + RW capable of high-speed recording at 4 × speed or higher in accordance with the current standard of DVD + RW media if the substrate having meandering grooves defined in the present invention 5 is used after satisfying the above requirements of the present invention 1-4. Media can be provided. Examples of the purpose of meandering the groove include accessing a specific unrecorded track and rotating the substrate at a constant linear velocity.

According to the first to fifth aspects of the present invention, it is possible to provide an optical recording medium that exhibits excellent recording characteristics and shelf characteristics for high linear velocity recording.
Furthermore, according to the present invention 3 to 4, it is possible to provide an optical recording medium excellent in repetitive recording characteristics at a high linear velocity.
Furthermore, according to the fifth aspect of the present invention, it is possible to provide a DVD + RW medium capable of high-speed recording at a quadruple speed or higher.

  Examples of the present invention and comparative examples are shown below, but these examples do not limit the present invention. For example, the effects of the present invention are not limited to the case where the specific protective layer material, reflective layer material, layer configuration, manufacturing apparatus, manufacturing method, evaluation apparatus, and the like used in the examples are employed. In addition, the outline of the layer structure of the optical recording medium (optical disk) produced by the Example and the comparative example is as showing in FIG.

<Examples 1-10> and <Comparative Examples 1-10>
The substrate is made of polycarbonate having a diameter of 120 mmφ and a thickness of 0.6 mm, and has a groove shape with a track pitch of 0.74 μm, a groove (recess) width of 0.3 μm, and a groove depth of about 30 nm. Each layer of was laminated in order.
ZnS (80 mol%) SiO ₂ (20 mol%) was used for the lower protective layer, and a film having a thickness of 60 nm was formed at a film formation rate of 9 nm / sec.
For the recording layer, each phase change material shown in Table 1 was used, and a film having a thickness of 15 nm was formed at a film formation rate of 5 nm / sec.
As the upper protective layer, ZnS (80 mol%) SiO ₂ (20 mol%) was used, and a film was formed to a thickness of 7 nm at a film formation rate of 4 nm / sec.
SiC was used for the sulfidation prevention layer, and a film having a thickness of 4 nm was formed at a film formation rate of 1 nm / sec.
Ag was used for the reflective layer, and a film having a thickness of 140 nm was formed at a film formation rate of 35 nm / sec.
The reason why SiC is used as the sulfidation prevention layer is to prevent reaction between Ag as the reflection layer and sulfur contained in the upper protection layer. In addition, an RF magnetron sputtering method was used for the film formation of ZnS (80 mol%) SiO ₂ (20 mol%), and a DC magnetron sputtering method was used for the film formation of the recording layer, the sulfidation prevention layer, and the reflection layer.
Subsequently, a UV curable resin was applied as an environmental protection layer and cured.
Finally, a substrate similar to the above substrate was bonded onto the environmental protection layer to obtain an optical disk having a thickness of about 1.2 mm, but this bonded substrate was not shown.
Next, an initialization device (POP120-7AH manufactured by Hitachi CP Co., Ltd.) having a laser head in which each of these optical discs has a focusing function added to laser light having an output wavelength of 830 nm, a width of about 1 μm, a length of about 75 μm, and a maximum output of about 2 W. ). The initialization conditions were an initialization power of 1400 mW, a linear speed of 11 m / s, and a constant head feed speed of 37 μm.

Each optical disk produced as described above was evaluated for repetitive recording characteristics (direct overwrite characteristics) at a recording linear velocity of 28 m / s (equivalent to 8 × speed on DVD).
For the evaluation, an optical disk evaluation apparatus (DDU-1000 manufactured by Pulstec Corp.) having a pickup with a wavelength of 650 nm and NA of 0.65 was used. As tracks to be evaluated, five adjacent tracks were recorded, and the middle track was reproduced. The recording method was a pulse modulation method, and the modulation method was an EFM + [8/16 (2,10) RLL] modulation method. The recording linear density was 0.267 μm / bit, and recording was performed in the groove. Optimal conditions were used for the recording power Pw and the erasing power Pe. The bottom power Pb was constant at Pb = 0.1 mW.
Data to clock (data to clock) jitter of the recorded signal was measured, and jitter σ / Tw (Tw: window width) was used as an evaluation item.
In the same manner, the change in jitter in the one-time recording, two-time recording, ten-time recording, and 100-time recording was evaluated for each optical disc.
The results are shown in FIG. 2. From the figure, it can be seen that <Comparative Example>, except for Comparative Examples 1 and 9, has poor initial characteristics and repeated characteristics compared to <Example>.
Next, the discs of <Examples 1 to 10> and <Comparative Examples 1 and 9> were recorded once by the same recording method, then placed in an environment of 80 ° C. and 85%, and the change in reflectance Itop after 300 hours was observed. Compared.
The results are shown in FIG. From the figure, it can be seen that when the configuration of the present invention is employed, the variation in reflectivity tends to be small, and the range defined in the present invention 1 is desirable for the Ge composition amount. However, although Comparative Example 1 is not different from the present invention, the storage characteristics are not good as described later (FIG. 5).

<Comparative Examples 11-15>
An optical disc was prepared and initialized in the same manner as in Example 1 except that the phase change material was changed to the material shown in Table 2.
With respect to these optical discs, jitter was evaluated in the same manner as in <Example 1> in one-time recording, two-time recording, ten-time recording, and 100-time recording.
The results are shown in FIG. For comparison, the results of the optical disc of <Example 1> are also shown, and it can be seen that all the optical discs have substantially the same characteristics. When the storage characteristics of <Comparative Examples 11 to 15> were evaluated using the same method as in FIG. 3, the variation in reflectance was small as in <Examples 1 to 10> and <Comparative Example 1>. Things were confirmed.
Next, after the optical disks of <Examples 1-10> and <Comparative Examples 1 and 11-15> were stored in an unrecorded state in an environment of 80 ° C. and 85% for 100 hours, <Examples 1-10> and <Comparison In the same recording method as in Examples 1 to 10>, the jitter of one-time recording and two-time recording was evaluated, and each optical disk was compared with respect to the difference in jitter before and after storage.
The results are shown in FIG. Although any optical disk shows deterioration due to storage, it is apparent that the optical disk adopting the configuration of the present invention is less deteriorated.

以上の結果から、本発明の構成を採用する事で、高線速記録特性と保存信頼性に優れた光ディスクを提供できることが分かる。

From the above results, it can be seen that by adopting the configuration of the present invention, an optical disk excellent in high linear velocity recording characteristics and storage reliability can be provided.

<Examples 11 to 19>
Each optical disk was manufactured in the same manner as in Example 1 except that the upper protective layer material was changed to the material shown in Table 3. For comparison, the upper protective layer material of <Example 1> is also shown.
The above optical disks were compared by the same evaluation method as in <Example 1>.
The results are shown in FIG. From the figure, it can be seen that <Example 1> and <Examples 13 to 15> have better repeatability than the other examples. In this example, when the reference example 1 is replaced with another example such as the example 2 and the upper protective layer material is changed to the material shown in Table 3, almost similar results can be obtained. .

<Examples 20 to 27>
Each optical disc was manufactured in the same manner as in Example 1 except that a material as shown in Table 4 (hereinafter referred to as an interface layer material) was inserted between the lower protective layer and the recording layer. The film thickness of the interface layer material was 2 nm.
Recording was performed on each of the above optical disks at a power 4 mW higher than the recording power used in the evaluation method in <Example 1>, and the jitter of 500 times recording was compared.
The results are shown in FIG. Although the result of <Example 1> in which no interface layer is inserted is also shown for comparison, it can be seen from the figure that the repetition characteristics in high power recording can be improved by adopting the configuration of the present invention.

<Examples 28 to 30>
An optical disc was produced and evaluated in the same manner as in Example 20 except that the interface layer thickness was changed as shown in Table 5. The results are shown in FIG. The results of <Example 1> and <Example 20> are also shown for comparison.
From the result of FIG. 8, it can be seen that the range of the interface layer thickness of the present invention 4 is optimal.

The figure which shows the outline of the layer structure of the optical recording medium (optical disk) produced by the Example and the comparative example. The figure which shows the evaluation result of the optical disk of Examples 1-10 and Comparative Examples 1-10. The figure which shows the result of having evaluated DC irradiation using the optical disk evaluation apparatus, after initializing the optical disk of Examples 1-10 and Comparative Examples 1 and 9. FIG. The figure which shows the evaluation result of the optical disk of Example 1 and Comparative Examples 11-15. The figure which shows the evaluation result of Examples 1-10 and the optical disk of the comparative example 1 and the comparative examples 11-15. The figure which shows the evaluation result of the storage characteristic of the optical disk of Example 1 and Examples 11-19. The figure which shows the evaluation result of the optical disk of Example 1 and Examples 20-27. The figure which shows the evaluation result of the optical disk of Examples 1, 20, and 28-30.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Lower protective layer 3 Recording layer 4 Upper protective layer 5 Antisulfuration layer 6 Reflective layer 7 Environmental protective layer

Claims (5)

It comprises a structure in which at least a lower protective layer, a recording layer made of a phase change material, an upper protective layer, and a reflective layer are provided on a light-transmitting substrate, and the recording layer is separated into a crystalline phase and an amorphous phase by laser light irradiation. In an optical recording medium on which rewrite recording is performed by causing a phase change of the above, the phase change material of the recording layer has the following composition formula (where α, β, γ, δ, and ε are atomic ratios): An optical recording medium characterized by things.
GaαSbβSnγGeδCuε
0.03 ≦ α ≦ 0.10
0.56 ≦ β ≦ 0.79
0.10 ≦ γ ≦ 0.24
0.04 ≦ δ ≦ 0.12
0.01 ≦ ε ≦ 0.05   The lower protective layer has a thickness of 50 to 100 nm, the recording layer has a thickness of 10 to 20 nm, the upper protective layer has a thickness of 3 to 10 nm, and the reflective layer has a thickness of 100 to 300 nm. The optical recording medium according to claim 1. The material of the lower protective layer and the upper protective layer in contact with the recording layer is composed of a mixture of ZnS and SiO ₂ , and the mixing ratio of SiO ₂ is in the range of 15 to 35 mol% with 100 mol% as a whole. The optical recording medium according to claim 1 or 2. SiO ₂ film is inserted between the lower protective layer and the recording layer, an optical recording medium according to any one of claims 1 to 3 the film thickness thereof, characterized in that in the range of 1 to 3 nm. 5. The substrate according to claim 1, wherein the substrate has meandering grooves having a groove pitch of 0.74 ± 0.03 μm, a groove depth of 22 to 50 nm, and a groove width of 0.2 to 0.4 μm. Optical recording medium.

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