JPH11167747A - Phase transition type optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obviate the erasing or rewriting of recording marks accompanying the increase of a substantial increase of a reproducing energy density or the decrease of a reproducing power margin in order to obtain reproduction inter change in a wide wavelength region from a current wavelength region to a future short wavelength region. SOLUTION: This phase transition optical recording medium includes a phase transition optical recording layer 3 causing transition to a crystalline state and an amorphous state by photoirradiation and a wavelength dependent light absorption regulation layer 2 arranged in contact with at least one surface of this phase transition optical recording layer 3. The attenuation coefft. in a wavelength region from 400 nm to 800 nm of the wavelength dependent light absorption regulation layer 2 is <=1.0 and the attenuation coeffts. k400 , k600 , k800 at the respective wavelengths 400 nm, 600 nm, 800 nm satisfy k800 +0.01<k400 <k800 +0.8, k800 +0.01<k600 <k800 +0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change optical recording medium for recording and reproducing information by irradiating a laser beam.

[0002]

2. Description of the Related Art Optical disks have supported the rise of personal computers these days as large-capacity recording media having high capacity, high-speed access, and medium portability. Among them, phase-change optical disks have recently begun to be put to practical use, characterized by a simple recording principle.

The principle of recording / reproducing a phase-change optical disc is to irradiate a recording layer on a substrate with a semiconductor laser to reversibly change the recording portion between amorphous and crystalline. It is read as record information. That is, at the time of recording, a phase change optical recording material is irradiated with a laser beam of a relatively high output and a short pulse, and a recording portion is heated to a temperature equal to or higher than a melting point and then rapidly cooled to form an amorphous recording mark. At the time of erasing, the phase-change recording material is irradiated with a laser beam having a lower output and a longer pulse than at the time of recording, and is kept at a temperature higher than the crystallization temperature and lower than the melting point for crystallization.

As described above, since the phase change optical recording is for reading the change in the reflectance between the amorphous and the crystalline state, the optical system has a feature that the structure of the optical system is simple. Furthermore, unlike a magneto-optical recording, it does not require a magnetic field, is easy to overwrite (overwrite) by light intensity modulation, and has a further characteristic that the data transfer speed is high. In addition, it is excellent in compatibility with a read-only disc such as a CD-ROM.

Means for improving the recording density of a phase change optical disk include shortening a recording mark interval,
It has been considered to reduce the size of a recording mark, shorten the wavelength of a light source, and the like. Among these methods, land groove (L / G) recording, mark length recording, and the like have been proposed as methods for reducing the recording mark interval.

In the L / G recording method, the depth of a groove (groove) for guiding a laser beam spot to a predetermined position is set to about 1/6 of the laser wavelength to reduce crosstalk, and the surface of the groove is reduced. This enables recording not only on the top but also on the land surface corresponding to the space between the grooves, and it is expected that the recording density will be about twice as high as that of the conventional method. The mark length recording method detects a change in reflectivity (differential component of the reflectivity) at the edge of a recording mark, and can be expected to have approximately 1.5 times higher density than conventional mark position recording.

In addition to such high-density recording technology, R
If the super-resolution technology proposed for OM media is used, the recording density of about 650Mbpsi (bit / inch ² )
It is expected that it can be improved by about 20 times.

In addition to the above-mentioned method, it is considered that shortening the wavelength of the light source for performing recording / reproduction is also effective for increasing the density. Here, when the laser light source is stopped down using an optical lens, the minimum spot depends on the wavelength of the light source, and the light spot can be made smaller as the wavelength becomes shorter. For example, in the first generation DVD-RAM, the wavelength
Although a 650 nm laser is used, it is a matter of course that the wavelength of laser light will be shortened as the recording capacity increases in the future.

For these reasons, researches aimed at shortening the wavelength of recording / reproducing laser light have also been carried out (for example, Nobukuni et al., Proceedings of the 8th Phase Change Recording Research Group, p. 72). Such). However, this is intended only to optimize the configuration of the disk layer for short wavelengths and to improve the recording / reproducing characteristics. Although optical disks optimized for such short wavelengths can be expected to have characteristics at specific wavelengths, there are still many issues to be solved in order to support all wavelengths that will appear in the future, including the current wavelength. ing.

For example, since the refractive index and the extinction coefficient of each layer constituting the phase change optical disk change with respect to the wavelength, it is difficult to cope with the wavelength change even with an optical disk optimized for a short wavelength. Further, since the energy density of light increases as the wavelength becomes shorter, there arises a problem that a recording mark is erased with a normal reproducing power or a reproducing power margin is narrowed. If long-term data storage functions are emphasized, the disc needs to be compatible with future drives, and a disc that can reproduce light sources of all wavelengths is required.

[0011]

As described above, shortening the wavelength of the recording / reproducing laser beam is effective for increasing the recording density. Therefore, as the recording capacity increases, the light source for recording / reproducing becomes shorter wavelength. There is also a study to reduce the wavelength of optical discs.

However, it is difficult for an optical disc optimized for short wavelength to cope with a change in wavelength, and the recording mark is erased with normal reproducing power due to an increase in the energy density of light due to the short wavelength. Or the reproduction power margin becomes narrow. In order to satisfy the long-term data storage function, there is a demand for an optical disc that can reproduce data from a light source having a wavelength that will appear in the future from the currently used wavelength.

The present invention has been made in order to address such problems. For example, erasing, rewriting, and reproducing power of a recording mark due to an increase in the energy density of light accompanying shortening of the wavelength of a recording / reproducing laser beam. It is an object of the present invention to provide a phase-change optical recording medium that enables reproduction compatibility in a wide wavelength range by eliminating a decrease in margin and the like.

[0014]

According to a first aspect of the present invention, there is provided a phase change optical recording medium having a phase change optical recording layer which transitions between a crystalline state and an amorphous state by light irradiation. In the variable optical recording medium, the extinction coefficient in the wavelength range of 400 nm to 800 nm is 1.0 or less, and the extinction coefficient of the wavelength 400 nm is k ₄₀₀ , the extinction coefficient of the wavelength 600 nm is k ₆₀₀ ,
When 800nm of the extinction coefficient was _{k 800, k 800 + O.01 <} k 400 <k 800 +0.8 ...... (1) k 800 + O.01 <k 600 <k 800 +0.5 ...... (2) It is characterized by having a wavelength-dependent light absorption adjusting layer satisfying k ₈₀₀ <k ₆₀₀ <k ₄₀₀ (3).

According to another aspect of the present invention, there is provided a phase-change optical recording medium including a phase-change optical recording layer that transitions between a crystalline state and an amorphous state by light irradiation. , GaP, GaAs, CdTe and InP
At least one semiconductor selected from the group consisting of Cr, C
o, Cu, Au, Ag, Mo, Ce, Sm, Eu, T
It is characterized by having a wavelength-dependent light absorption adjusting layer made of a transparent dielectric containing at least one selected from b, Dy, Ho and Tm in the range of 1 to 60% by volume.

In the phase-change optical recording medium of the present invention, the wavelength-dependent light absorption adjusting layer has an extinction coefficient of not more than 1.0 in a wavelength range of 400 nm to 800 nm, and has a wavelength of 400 nm, 600 nm,
The extinction coefficients k ₄₀₀ , k ₆₀₀ , and k ₈₀₀ at each wavelength of 800 nm satisfy the above-described equations (1), (2), and (3). That is, the light absorption adjusting layer in the present invention has a wavelength-dependent light absorption characteristic in which the light absorption increases as the wavelength becomes shorter. Therefore, it is possible to prevent an increase in the light absorption amount of the phase change optical recording layer as the wavelength becomes shorter. As described above, by adjusting the amount of light absorption of the phase-change optical recording layer according to the wavelength, reproduction compatibility can be achieved in a wide wavelength range from the currently used wavelength to a short wavelength compatible with high density.

[0017]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view of a main part showing a basic structure of a phase change optical recording medium (optical disk) of the present invention. In FIG. 1, reference numeral 1 denotes a disk substrate. As the disk substrate 1, for example, a resin substrate such as a polycarbonate substrate having a thickness of about 0.6 mm is used. Grooves (not shown) are formed on the main surface side of the disk substrate 1. The recording method is not particularly limited, and may be either groove recording or land / groove (L / G) recording.

On the main surface 1a of the disk substrate 1 having a groove, a phase-change optical recording layer 3 that transitions between a crystalline state and an amorphous state by light irradiation is formed via a wavelength-dependent light absorption adjusting layer 2. Have been. The wavelength-dependent light absorption adjusting layer 2, which will be described in detail later, may be formed on the upper side of the phase change optical recording layer 3, and if it is arranged at least in contact with one surface of the phase change optical recording layer 3, the effect thereof is obtained. It demonstrates.

As a constituent material of the phase-change optical recording layer 3, a crystalline state and an amorphous state are reversibly changed by light irradiation,
Materials having different optical characteristics between the two states are used. For example, Ge-Sb-Te, In-Sb-Te, Sn-Se
-Te, Ge-Te-Sn, In-Se-Tl-Co and the like. In addition, Co, Pt, A
Even if a small amount of g, Ir, Nb, Ta, V, W, Ti, Cr, Zr or the like is added, good characteristics can be obtained as the phase-change optical recording layer 3.

The wavelength-dependent light absorption adjusting layer 2 has a thickness of 400 nm
The extinction coefficient in the 800 nm wavelength range is 1.0 or less,
Extinction coefficient k ₄₀₀ , k for each wavelength of 0 nm, 600 nm, 800 nm
_600, k ₈₀₀ is _{k 800 + O.01 <k 400 <} k 800 +0.8 ...... (1) k 800 + O.01 <k 600 <k 800 +0.5 ...... (2) k 800 <k 600 <k ₄₀₀ satisfies (3). That is, the wavelength-dependent light absorption adjusting layer 2 has an extinction coefficient k that increases as the wavelength becomes shorter.
have.

As a constituent material of such a wavelength-dependent light absorption adjusting layer 2, a material having a shorter wavelength and an increased light absorption is suitable. For example, GaP, GaAs, CdT
e, semiconductor materials such as InP have wavelengths from 800 nm to 400 nm.
The light absorptance gradually increases toward.
In addition, a specific impurity can be added to a semiconductor material such as Ge, PbS, InAs, and InSb to obtain a desired extinction coefficient.

Also, when a transition metal or a rare earth metal is mixed in the transparent dielectric, the light absorption in the short wavelength region can be increased. For example, Cr, Co, Cu, A
u, Ag, Mo, Ce, Sm, Eu, Tb, Dy, H
The transparent dielectric containing o, Tm, etc., has an increased light absorption at 600 nm or less. Further, in such a mixed film, the wavelength dependence of the extinction coefficient changes depending on the particle size and the filling rate of the metal particles.

Here, Cr, Co, Cu, Au, Ag,
Mo, Ce, Sm, Eu, Tb, Dy, Ho and Tm
It is preferable that the amount of addition of at least one metal selected from the following to the transparent dielectric is in the range of 1 to 60% by volume. If the amount of the above-mentioned metal is less than 1% by volume, it is not possible to obtain a sufficient light absorptivity in the short wavelength region.
%, The extinction coefficient k is likely to exceed 1.0.

By appropriately combining the type of metal material to be added to the transparent dielectric as described above, the particle size, the filling factor, and the like, the wavelength-dependent light whose light absorptivity gradually increases with shortening of the wavelength is obtained. A translucent layer can be obtained as the absorption adjusting layer 2. Note that as the transparent dielectric, SiO ₂ , A
l ₂ O ₃ , AlN, Si ₃ N ₄ , Ta ₂ O ₅ , TiO ₂
Various well-known materials such as can be used.

The wavelength-dependent light absorption adjusting layer 2 first has a thickness of 400 nm.
It is necessary that the extinction coefficient k be 1.0 or less in a wavelength range from 1 to 800 nm, and a more preferable range of the extinction coefficient k is 0.5 or less. The extinction coefficient k in the wavelength range from 400 nm to 800 nm
In the wavelength-dependent light absorption adjusting layer 2 exceeding 1.0, the basic recording / reproducing characteristics are lowered due to the attenuation of the recording / reproducing laser beam. Since the extinction coefficient of such a thin film largely depends on the film forming conditions, a film satisfying the above conditions can be obtained by selecting the film forming conditions according to each material.

Further, the wavelength-dependent light absorption adjusting layer 2 is composed of 4
Extinction coefficient k ₄₀₀ , k at each wavelength of 00 nm, 600 nm, 800 nm
Conditions such as the constituent materials and the thicknesses thereof are set so that ₆₀₀ and k ₈₀₀ satisfy the above-described equations (1), (2) and (3). Since the light absorption generally increases as the thickness of the wavelength-dependent light absorption adjustment layer 2 increases, the thickness is appropriately set according to the extinction coefficient of the constituent material described above. The specific thickness of the wavelength-dependent light absorption adjusting layer 2 is preferably in the range of 5 to 300 nm, more preferably in the range of 10 to 100 nm.
Here, if the values of k ₄₀₀ and k ₆₀₀ are (k ₈₀₀ +0.01) or less, the function as the wavelength-dependent light absorption adjusting layer 2 cannot be obtained. On the other hand, (k ₈₀₀ +0.8) and (k ₈₀₀ +0.
Above 5), the light absorption in the short wavelength region becomes too large, and the reproduction characteristics with short wavelength laser light deteriorate.

The wavelength-dependent light absorption adjusting layer 2 as described above
By arranging at least one surface of the phase change optical recording layer 3, the amount of light absorbed by the phase change optical recording layer 3 can be substantially reduced as the wavelength becomes shorter. Also,
A layer such as an optical adjustment layer may be further interposed between the wavelength-dependent light absorption adjustment layer 2 and the phase change optical recording layer 3. In the phase change optical recording medium shown in FIG. 1, a protective layer 4 and a reflection layer 5 are provided on the phase change optical recording layer 3 in order. The layer configuration of these optical recording media is not particularly limited, and various layer configurations can be adopted as long as the basic configuration of the present invention is satisfied.

The phase change optical recording medium of the present invention as described above can be obtained by forming each layer on the disk substrate 1 by a physical vapor deposition method or a chemical vapor deposition method. The wavelength-dependent light absorption adjusting layer 2 can be formed by various sputtering methods using, for example, a target of a target material.

For example, a plurality of targets constituting a target material are simultaneously or alternately placed in various atmospheres such as a mixed gas of an inert gas such as Ar, Xe or Ne and oxygen, nitrogen or carbon. It can be formed by sputtering. When a mixed film of a transparent dielectric and a transition metal or a rare earth metal is used as the light absorption adjusting layer 2,
Simultaneous sputtering or alternate sputtering using targets of both materials may be used, or a mixed target composed of both materials may be used.

In the above-described film forming method, by selecting and controlling process parameters such as input power, ultimate pressure, sputtering pressure, reactive gas type, substrate bias, additives, and material composition ratio, the wavelength dependence can be improved. The wavelength dependency of the light absorption rate in the light absorption adjustment layer 2 can be controlled.

In the phase-change optical recording medium of the present invention, the wavelength-dependent light absorption of the phase-change optical recording layer 3 is adjusted by applying the wavelength-dependent light absorption adjusting layer 2 as described above. Becomes possible.

Here, the light emitted from the laser is condensed on the recording surface by an optical lens and generates heat. At this time, since the size of the focused spot is inversely proportional to the square of the laser wavelength, the energy density per unit area is also inversely proportional to the square of the wavelength. That is, as the wavelength becomes shorter, the heat generated in the recording layer increases and the temperature rises.
For this reason, for example, the current DV optimized at a wavelength of 650 nm
Considering that the D disk will be reproduced by a short-wavelength light source drive in the future, the heat load will be greatly increased. That is, erasing (crystallization) or writing (amorphization) occurs due to a heat load during reproduction, and recorded information may be destroyed. Even if the reproduction power is lowered, the power margin becomes narrow, and stable reproduction becomes difficult.

The wavelength-dependent light absorption adjusting layer 2 according to the present invention exerts a great effect on such a reproduction compatibility problem. For example, assuming a phase change optical recording medium having a layer configuration as shown in FIG. 1 using GaP as the light absorption adjusting layer 2, the wavelength dependence of the absorption coefficient in the phase change optical recording layer 3 (amorphous) is calculated. As a result, the result shown in FIG. 2 was obtained.

As is apparent from FIG. 2, the absorption coefficient of the medium gradually decreases from the current wavelength region to 400 nm, so that erasing and rewriting at the time of reproduction can be avoided and a reproduction power margin can be secured. . For the same reason, the recording / erasing power margin becomes relatively narrow as the wavelength becomes shorter. However, according to the phase-change optical recording medium having the wavelength-dependent light absorption adjusting layer 2 of the present invention, this can be prevented. I can do it.

[0036]

Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1 In Example 1, a phase change optical recording medium having a layer structure shown in FIG. 3 was produced. The phase change optical recording medium shown in FIG. 3 has a ZnS-based substrate on a grooved polycarbonate (PC) substrate 1.
A first protective layer 4A made of SiO ₂ , a light absorption adjusting layer 2 made of GaP, an optical recording layer 3 made of GeSbTe, Zn
A second protective layer 4B made of S-SiO ₂ and a reflective layer 5 made of Al are sequentially formed.

The phase change optical recording medium shown in FIG. 3 was manufactured by the following procedure. First, the grooved PC substrate 1 was mounted on a substrate holder in a multi-source sputtering apparatus, and after evacuating the inside of the apparatus, Ar gas was introduced. Sputtering was performed while the substrate holder was revolving around itself, and each layer was sequentially formed.
First, RF power was applied to the ZnS—SiO ₂ target, and the first protective layer 4A having a thickness of 100 nm was formed on the PC substrate 1.

Next, RF power was applied to the GaP target to form a light absorption adjusting layer 2 having a thickness of 5 to 100 nm on the first protective layer 4A. Further, RF power was applied to the GeSbTe target to form an optical recording layer 3 having a thickness of 10 nm on the light absorption adjusting layer 2. RF power is again applied to the ZnS—SiO ₂ target, and a 30 nm-thick second
Was formed. Finally, D is added to the Al target.
C power was applied to form a 50 nm-thick reflective layer 5 on the second protective layer 4B.

After recording on the phase-change optical disk thus manufactured under the conditions shown in Table 1, the wavelength dependence of the reproduction characteristics was also examined under the conditions shown in Table 1. Since the optimum value of the recording power differs depending on the disc layer configuration, the recording power is appropriately adjusted within the range shown in Table 1.

[0041]

[Table 1] FIG. 4 shows the wavelength dependence of the reproduced signal when the thickness of the GaP light absorption adjusting layer 2 was changed from 5 nm to 100 nm. Note that the intensity of the reproduced signal at a wavelength of 640 nm is standardized as 1.0. As is apparent from FIG. 4, when the light absorption adjusting layer 2 is not formed, a sharp signal drop is observed in a short wavelength region of 500 nm or less, which is considered as erasure of a recording mark.

On the other hand, in the phase-change optical disk of Example 1 in which the GaP light absorption adjusting layer 2 was formed, no sharp signal decrease was recognized, which is considered to be the erasure of the recording mark. In particular, when the thickness of the GaP light absorption adjusting layer 2 is 10 nm or less, the signal intensity tends to increase to the left with respect to the wavelength, whereas the thickness of the GaP light absorption adjusting layer 2 is 20 to 10 nm.
In each optical disc of 0 nm, the signal intensity is constant or gradually decreases with the shortening of the wavelength. This is because the effective spot size was reduced due to the effect of shortening the wavelength, and it can be seen that the energy control by the light absorption adjustment layer 2 is working effectively.

As described above, according to the phase change optical recording medium having the light absorption adjusting layer 2 of the present invention, it is possible to obtain good characteristics without reproduction deterioration in a wide wavelength range. As a result, even if the disc is optimized for the current wavelength, it is possible to ensure reproduction compatibility with respect to a future shortening of the wavelength.

Example 2 In Example 2, a phase change optical recording medium having a layer structure shown in FIG. 5 was produced. The phase change optical recording medium shown in FIG. 5 has a first protective layer 4A made of ZnS—SiO _{2, a} first light absorption adjustment layer 2A made of an Au—SiO ₂ mixed film on a grooved PC substrate 1, and An optical recording layer 3 made of GeSbTe;
Second light absorption adjusting layer 2 made of Au—SiO ₂ mixed film
B, second protective layer 4B made of ZnS—SiO ₂ , Al
The reflective layers 5 made of Mo are sequentially formed.

The phase-change optical recording medium shown in FIG.
It was produced in the same procedure as described above. First, after mounting the grooved PC substrate 1, evacuating and introducing a sputtering gas, RF power is applied to the ZnS—SiO ₂ target, and a first 80 nm-thick first film is formed on the PC substrate 1. Was formed.

Next, RF power is applied to the Au (40 vol%)-SiO ₂ target to form a film having a thickness of 5 to 5 μm on the first protective layer 4A.
A 200 nm first light absorption adjusting layer 2A was formed. further,
RF power was applied to the GeSbTe target to form an optical recording layer 3 having a thickness of 10 nm on the first light absorption adjusting layer 2.
RF power was again applied to the Au (40 vol%)-SiO ₂ target to form a second light absorption adjusting layer 2 B having a thickness of 20 nm on the optical recording layer 3. Further, ZnS-SiO ₂ data - by supplying an RF power to the target, to form a second protective layer 4B having a thickness of 10nm on the second light absorption controlling layer 2B. Finally, AlM
o DC power is applied to the target and the second protective layer 4B
A reflective layer 5 having a thickness of 100 nm was formed thereon. The recording / reproducing characteristics of the phase-change optical disk manufactured as described above were measured in Example 1.
Was evaluated in the same manner as described above. FIG. 6 shows the result. When the thickness of the lower first light absorption adjusting layer 2A is in the range of 10 to 150 nm, the intensity of the reproduced signal is constant or gradually decreases with the shortening of the wavelength. This is because the effective spot size was reduced due to the effect of shortening the wavelength, and it can be seen that the energy control by the light absorption adjustment layer 2 is working effectively.

As described above, according to the phase change optical recording medium having the light absorption adjusting layer 2 of the present invention, it is possible to obtain good characteristics without deterioration in reproduction in a wide wavelength range. As a result, even if the disc is optimized for the current wavelength, it is possible to ensure reproduction compatibility with respect to a future shortening of the wavelength.

Example 3 In Example 3, a phase change optical recording medium having a layer structure shown in FIG. 7 was produced. The phase-change optical recording medium shown in FIG. 7 has a first protective layer 4A made of ZnS—SiO ₂ , an optical recording layer 3 made of GeSbTe, and C on a grooved PC substrate 1.
Light absorption adjusting layer 2 made of u-Al ₂ O ₃ mixed film, ZnS
A _second protective layer 4B made of SiO ₂ and a reflective layer 5 made of Au are sequentially formed.

The phase-change optical recording medium shown in FIG.
It was produced in the same procedure as described above. First, after mounting the grooved PC substrate 1, evacuating and introducing a sputtering gas, RF power is applied to the ZnS—SiO ₂ target, and a first 100 nm-thick film is formed on the PC substrate 1. The protective layer 4A was formed.

Next, RF power was applied to the GeSbTe target to form an optical recording layer 3 having a thickness of 10 nm on the first protective layer 4A. Further, Cu (50 vol%)-Al ₂ O ₃ tar
RF power is applied to the optical recording layer 3 to form a film having a thickness of 5 to
A 100 nm light absorption adjusting layer 2 was formed. Again ZnS-Si
RF power is supplied to the O ₂ target, and the light absorption adjusting layer 2 is applied.
A second protective layer 4B having a thickness of 10 nm was formed thereon. Finally,
The DC power is supplied to the Au target, and the second protective layer 4
A reflective layer 5 having a thickness of 100 nm was formed on B.

The recording / reproducing characteristics of the phase-change optical disk manufactured as described above were evaluated in the same manner as in Example 1.
FIG. 8 shows the result. The thickness of the Cu-Al ₂ O ₃ light absorption controlling layer 2 is reproduced signal intensity in the range of 5~50nm or constant with respect to shorter wavelength, decreasing moderately. This is because the effective spot size was reduced due to the effect of shortening the wavelength, and it can be seen that the energy control by the light absorption adjustment layer 2 is working effectively.

As described above, according to the phase change optical recording medium having the light absorption adjusting layer 2 of the present invention, it is possible to obtain good characteristics without deterioration in reproduction in a wide wavelength range. As a result, even if the disc is optimized for the current wavelength, it is possible to ensure reproduction compatibility with respect to a future shortening of the wavelength.

[0053]

As described above, according to the phase change optical recording medium of the present invention, good characteristics without deterioration in reproduction over a wide wavelength range can be obtained, and a sufficient power margin for recording, erasing, and reproduction can be obtained. Can be obtained. Therefore, according to such a phase change optical recording medium of the present invention, it becomes possible to ensure good reproduction compatibility from the current wavelength range to the future short wavelength range.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a basic structure of a phase change optical recording medium of the present invention.

FIG. 2 is a diagram showing an example of wavelength dependence of an absorption coefficient of an optical recording layer in the layer configuration shown in FIG.

FIG. 3 is a cross-sectional view illustrating a main structure of the phase-change optical recording medium according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the wavelength dependence of a reproduction signal when a GaP film thickness is used as a parameter in the first embodiment of the present invention.

FIG. 5 is a sectional view showing a main structure of a phase change optical recording medium according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the wavelength dependence of a reproduction signal when the Au—SiO ₂ film thickness is used as a parameter in Example 2 of the present invention.

FIG. 7 is a sectional view showing a main structure of a phase-change optical recording medium according to Embodiment 3 of the present invention.

FIG. 8 shows Cu—Al ₂ O ₃ in Example 3 of the present invention.
FIG. 4 is a diagram illustrating the wavelength dependence of a reproduction signal when a film thickness is used as a parameter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Disc substrate 2 ... Wavelength dependent light absorption adjustment layer 3 ... Phase change optical recording layer

Claims (2)

[Claims] 1. A phase change optical recording medium comprising a phase change optical recording layer that transitions between a crystalline state and an amorphous state by light irradiation, wherein an extinction coefficient in a wavelength range of 400 nm to 800 nm is 1.0 or less, and The extinction coefficient at a wavelength of 400 nm is k ₄₀₀ and the wavelength is 600
The extinction coefficient of nm is k ₆₀₀ and the extinction coefficient of wavelength 800 nm is k ₈₀₀
Where k ₈₀₀ +0.01 <k ₄₀₀ <k ₈₀₀ +0.8 k ₈₀₀ +0.01 <k ₆₀₀ <k ₈₀₀ +0.5 k ₈₀₀ <k ₆₀₀ <k _{400 The} wavelength-dependent light absorption adjustment layer that satisfies A phase-change optical recording medium comprising: 2. A phase-change optical recording medium having a phase-change optical recording layer that changes between a crystalline state and an amorphous state by light irradiation, wherein at least one kind of semiconductor selected from GaP, GaAs, CdTe and InP, or Cr, Co, Cu, A
u, Ag, Mo, Ce, Sm, Eu, Tb, Dy, Ho
And at least one selected from Tm by 1 to 60% by volume
A phase-change optical recording medium characterized by having a wavelength-dependent light absorption adjusting layer made of a transparent dielectric included in the range of.