JP2003317244A - Phase change type recording medium and method for information recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase change type recording medium and a method for information recording by which expansion of a phase change mark in a disk radial direction in the phase change type recording medium is suppressed, the smoothness of the recording medium is improved, and in-plane variation of a mark length is reduced. <P>SOLUTION: The phase change type recording medium 100 for recording information by irradiation with laser beams 108 comprises at least a support substrate 101, a metallic layer 102, a first dielectric layer 103 having one or more layers, a phase change type recording layer 104, and a second dielectric layer 105 having one or more layers. On the support substrate 101, spiral or concentric circular corrugation where the width of a recess part 107 is larger than that of a projecting part 106 exists. By using the recording medium 100 where a recording mark exists on the recess part 107, the information recording method records marks where a relation among a beam diameter Φ, a track pitch P and the width M of the recording mark ranges (1.8×P-Φ)≤M≤(2.2×P-Φ). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change recording medium for recording information by a phase change between a crystalline phase and an amorphous phase by irradiating an energy beam, and an information recording method for the phase change recording medium. Regarding In particular, the present invention relates to a phase-change recording medium for suppressing cross-write and cross-talk generated when the track pitch is reduced and realizing a high recording density, and an information recording method for the phase-change recording medium.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing the structure of a conventional phase change recording medium. The phase-change recording medium 700 is shown in FIG.
As shown in FIG. 7, it comprises a support substrate 701, a metal layer 702, a first dielectric layer 703, a phase change recording layer 704, and a second dielectric layer 705. In FIG. 7, reference numeral 708 indicates the irradiation direction of the laser beam. The unevenness of the substrate shows lands and grooves. Since the definition of the land and the groove of the surface type recording medium are divided, the convex portion 7 is used here.
06 and the concave portion 707. This phase change recording medium 7
In 00, recording and reproduction are performed directly on the film surface by an optical pickup device using an optical system in which the numerical aperture (NA) of the objective lens is 1 or less or a near-field recording optical pickup device using a solid immersion lens (SIL).

For example, Japanese Unexamined Patent Publication No. 2001-084642 discloses an optical recording medium for land / groove recording in which the width of a convex portion and the width of a concave portion are set to about 1: 1 and both concave and convex portions are recorded, and a manufacturing method thereof. It is disclosed. Japanese Patent Laid-Open No. 2001-084
Japanese Patent No. 591 discloses a multilevel recording method as a method for increasing the linear density. This is a method of modulating the area of a phase change mark according to multi-valued information with a constant mark recording period. In such a recording method, it is necessary to finely mark the length of the mark. Since there is a limit to the fine adjustment of the mark length in the multi-pulse, a method of changing the pulse width using a single pulse is used. However, in the case of recording with a single pulse, the length of the recording mark in the radial direction of the disc along with the mark length which is the length of the recording medium in the track direction of the disc-shaped recording medium (hereinafter simply referred to as “mark length”). The mark width (hereinafter, simply referred to as “mark width”), which is the size, also changes. In the case of a long recording mark, the mark width also widens, and depending on the recording conditions, the beam diameter Φ is, for example, a coefficient of 0.82, a wavelength λ of 405 nm, and an objective lens numerical aperture (NA) of 0.85. Is the beam diameter Φ
May extend to about 391 nm. Therefore, cross-write occurs between adjacent tracks, and there is a limit to the reduction of track pitch.

[0004]

Therefore, the present invention has been made in view of the above circumstances, and suppresses the spread of the phase change mark in the phase change recording medium in the disk radial direction, and further An object of the present invention is to provide a phase-change recording medium that can improve smoothness and reduce in-plane variation in mark length. Furthermore, it is an object of the present invention to provide an information recording method for controlling the mark length of a recording mark that has undergone a phase change using this phase change recording medium, reducing the in-plane variation of the mark length, and finely controlling it according to the recorded information. And

[0005]

In order to achieve the above-mentioned object, the invention according to claim 1 is a phase change recording medium for recording information by irradiating a laser beam, wherein the recording medium is at least supported. It has a substrate, a metal layer, a first dielectric layer composed of one or more layers, a phase change recording layer, and a second dielectric layer composed of one or more layers. A recording medium provided with concentric concavo-convex portions, wherein the concave portion has a width wider than that of the convex portion, and
It is a phase change recording medium in which information is recorded on the concave portion. The invention according to claim 2 is the phase-change recording medium according to claim 1, wherein the phase-change recording layer has an atomic ratio of Sb to Te (Sb / Te) in the range of 1 to 4 Sb. , Te
And a phase change recording medium containing at least one element selected from the group consisting of Ag, In, Ge, Ga, Al, Sn, B and Si. The invention according to claim 3 is the phase-change recording medium according to claim 1 or 2, wherein the metal layer is Ag alone or Ag and In, Ge, Ga, Al,
The phase change recording medium is a layer containing at least one element selected from the group consisting of Sn, B and Si. The invention according to claim 4 is the phase change recording medium according to any one of claims 1 to 3, wherein the second dielectric layer is a single layer of silicon nitride or a laminate of silicon nitride and a dielectric material. A certain phase change recording medium.

A fifth aspect of the present invention is a recording method on the phase-change recording medium according to any one of the first to fourth aspects, wherein the wavelength of the laser beam is λ, the numerical aperture NA of the objective lens is When the track pitch of the phase-change recording medium is P, the mark width of the recording mark is M, and the beam diameter Φ defined by 1 / e ² is 0.82 × λ / NA, the mark width M of the recording mark is ( 1.8 × P−Φ) ≦ M ≦ (2.2 × P−Φ)
It is an information recording method in the range of. The invention described in claim 6 is the method for recording information on the phase-change recording medium according to any one of claims 1 to 4, wherein the laser power is P
Modulate between power levels having a relation of 1>P2> P3,
The time for holding the power level P1 for recording information is T
1. Let T3 be the time for holding the P3 level of the information recording power level, and maintain the relationship of T1 ≦ T3,
This is an information recording method in which the mark length is changed by changing the lengths of T1 and T3. The invention described in claim 7 is claim 1
5. The method for recording information on the phase-change recording medium according to any one of 1 to 4, wherein the laser power is P1>P2> P3.
A power level P1 for recording information and a power level P2 for erasing information by modulating between power levels having a relationship of
Is a method of recording information in which the mark length is changed by changing the length of the holding time T1 by modulating the laser power between and. The invention described in claim 8 is the recording method on the phase-change recording medium according to claim 7, wherein the laser power is modulated between the power levels P1 and P2 according to the mark length and held. Information recording method for changing the length of time T1
The information recording method uses the information recording method in which the length of T1 and T3 is changed and the mark length is changed by changing the lengths of T1 and T3 while maintaining the relationship of 3.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the structure of a phase change recording medium according to the present invention. As shown in FIG. 1, the structure of the phase-change recording medium 100 is similar to that of the conventional phase-change recording medium shown in FIG.
1, a metal layer 102, a first dielectric layer 103 including at least one layer, a phase change recording layer 104, and a second dielectric layer 105 including at least one layer. As the material of the supporting substrate 101, polycarbonate resin, acrylic resin, acrylic resin, polyolefin resin, epoxy resin, vinyl ester resin, ultraviolet curing resin, glass, quartz, or the like can be used. As the metal layer 102, an Al alloy material such as Al, AlTi, or AlTiCu can be used. Also, Ag alone or A
It is also possible to use an Ag alloy containing g as a main component and adding other elements. As Ag alloy, AgPdCu, A
gAuCu, AgCu, AgZn, AgCuAl, Ag
RuZr, AgNiAlTi, etc. can be used. By using such a metal material, the surface flatness of the medium is improved and the disk noise can be reduced. Further, since Ag and Ag alloy are metallic materials having high thermal conductivity, the medium structure can be made into a rapidly cooled structure, and the extension of the mark length with respect to the recording pulse width can be suppressed. As a result, in-plane variations in mark length can be reduced.

As the first dielectric layer 103, ZnS-
SiO_Two, Al_TwoO_Three, AlN, SiO _TwoUse
You can Use these materials as a single layer or laminated
It AgInSbT is used as the phase-change recording layer 104.
e, GeSbTe, SbTe, GeTe, InSbT
Materials such as e and SbSe can be used. Also,
SbTe having an Sb / Te ratio in the range of 1 to 4 and SbTe
In addition to Te, Ag, In, Ge, Ga, Al, Sn, B,
Contain at least one element selected from the group of Si
It is also possible to use a phase change recording material having a composition. example
For example, AgInSbTe, GeSbTe, GeInSbT
e, GeGaSbTe, GaSbTe, GeAlSbT
e, GeSnSbTe, SbSbTe, GeBSbT
e, BSbTe, GeSiSbTe, SiSbTe
How is it? To use such a phase change recording material
Therefore, the in-plane variation of the mark length can be reduced. Second
As the dielectric layer 105, ZnS-SiO_Two, Al
_TwoO_Three, AlN, SiO _TwoEtc. can be used. This
These materials are used as a single layer or laminated layers. Also the second
The dielectric layer 105 is a single layer of silicon nitride (SiN), or
SiN and ZnS-SiO_Two, Al_TwoO_Three, AlN, SiO_Two
It may be a laminated structure of dielectric materials such as. SiN
By providing it on the surface, the strength of the medium can be increased.
This prevents scratches due to contact with the objective lens.
Can be controlled.

An uneven portion is provided on the surface of the phase change recording medium 100. The cross-sectional shape of the recess 107 may be rectangular, V-shaped, or semicircular. If the width of the concave portion 107 is W1 and the width of the convex portion 106 is W2, then W1> W2
To make a relationship. The groove depth of the phase change recording medium 100 is
The range is set to 10 to 50 nm. Groove depth is 10 nm
At the depths below, the effect of heat accumulation does not appear, and
The signal intensity decreases at a depth of 0 nm or more. On the support substrate 101 formed in such a shape, each layer is formed by vapor deposition by a surface treatment method such as a sputtering method or a vacuum vapor deposition method in an inert atmosphere such as Ar or N ₂ to form the phase change recording medium 100. To manufacture.

Next, an information recording method of the phase change recording medium of the present invention will be described. FIG. 2 is a schematic diagram showing a recording state in the phase change recording medium of the present invention, and shows the relationship between the beam diameter and the shape of the recording mark. 2A is a sectional shape of the phase-change recording medium 200, and FIG. 2B is a plan view corresponding to the sectional shape. In FIG. 2, 2022 is the beam diameter, 202
Reference numeral 1 indicates the shape of the recording mark that has changed in phase. Also,
The wavelength of the laser beam of the optical system is λ, and the numerical aperture of the objective lens is NA. P indicates the track pitch of the phase change recording medium 200. M indicates the mark width of the recording mark 2021 that has changed in phase. The diameter Φ of the laser beam spreads in Gaussian distribution and is defined as 1 / e ² , but here, it is a value obtained by 0.82 × λ / NA with a coefficient of 0.82.

In the information recording method of the present invention, the mark width M
Is recorded in the range of (1.8 × P−Φ) ≦ M ≦ (2.2 × P−Φ). By recording with the mark width M in this range, it is possible to prevent cross writing, which is an overlap of the recording marks 2021 between tracks for recording information with adjacent laser beams. Further, by setting the upper limit of the mark width M in the range of (2.2 × P−Φ), the beam diameter 20
It is possible to reduce the amount of the recording marks 2021 of the adjacent tracks in 22 and reduce crosstalk. The thinner the mark width M is, the more the crosstalk can be suppressed, but the signal strength decreases, so the lower limit is (1.8 × P−Φ).
In order to perform such recording, the phase change recording medium 200
Recess 20 for recording and recording information in recess 207 of
It is preferable to set the width W1 of No. 7 to be the same as the mark width M of the recording mark 2021. Further, the phase-change recording medium 200 of the present invention has a numerical aperture NA of the objective lens of 0.85 to 0.85.
It can be applied to an optical system having a numerical aperture of 0.9 or less, and can also be applied to an optical system having a numerical aperture NA exceeding 1 such as a solid immersion lens (SIL) and a solid immersion mirror (SIM). Further, the present invention can be applied to a near-field optical system in which an aperture or a structure is provided in the optical path to form a minute beam spot.

Next, a recording strategy for modulating the power of the laser power and the time for which the laser power is held when recording a phase change mark for multilevel recording will be described. FIG. 3 is a schematic diagram illustrating a recording strategy in the information recording method of the present invention. Laser power is P1
Modulation is performed at three levels that are in the relationship of>P2> P3. here,
P1 is a high output laser power, and after the phase-change recording material is melted at a high temperature, it has a high temperature and has a large temperature gradient. Therefore, heat is transferred to the dielectric layer, etc. Therefore, the phase change recording material is changed from the crystalline state to the amorphous state and information is recorded. P2 is a medium laser power, which brings the phase-change recording material into a molten state or a state close to that, but since the temperature gradient is small because it is not at a high temperature, it is difficult to transfer heat to the dielectric layer, etc. Therefore, the phase change recording material is changed from a crystalline state or an amorphous state to a crystalline state to erase information. P
3 is a low output laser power, and in order to bring about a large quenching effect by further applying a laser power to the phase-change recording material in a state of being melted at P1 to make the temperature higher so as to increase the temperature gradient. To use.

When recording one phase change recording mark M, the power level is modulated in the order of P1, P3 and P2. It is assumed that the time T1 for holding the P1 level and the time T3 for holding the P3 level are T3. When changing the mark length for multi-value recording, the lengths of T1 and T3 are changed. On this occasion,
It is set so as to satisfy the relationship of T1 ≦ T3 when recording a recording mark of any length for multilevel recording. Therefore, by satisfying the relationship of T1 ≦ T3 with respect to the time for which the laser powers of P1 and P3 are held, the mark length can be changed with a fine step size without expanding the mark width M of the recording mark.

Next, for multi-valued recording, another recording for modulating the laser power emitted by the laser and the time for holding the power when recording information according to the length of the phase change mark is recorded. An information recording method by the strategy will be described. FIG. 4 is a schematic diagram illustrating a recording strategy in the information recording method of the present invention. Laser power is P
Modulation is performed at three levels in the relationship of 1>P2> P3. When recording one phase change recording mark, the power level is modulated in the order of P1, P3, and P2. It is assumed that the time T1 for holding the P1 level and the time T3 for holding the P3 level are T3. When changing the mark length, when the mark length of the record mark is short, for example, when the mark length of the record mark is short as M1 and M2, recording is performed by power modulation between P1 and P2. That is, the power is also modulated between the P1 and P2 levels, and the P3 level is not provided.

The mark length of the recording mark is longer than M2,
When creating a recording mark of about M3, recording is performed by power modulation with a pulse of P1 and P3 that is longer than the power modulation between P1 and P2, and is approximately the same as the case of power modulation between P1 and P2 without P3. Minute marks can be formed. This means that when the pulse width of the laser light emission becomes shorter, the laser beam light emission does not follow up and recording is performed with a triangular waveform. In such a state, variations in the mark shape within the disk surface increase, but by performing power modulation in accordance with the mark length of the recording mark as described above, the mark length can be changed with a fine step size and the phase change type It is possible to suppress the variation in the mark length within the surface of the recording medium and record the minute marks with high uniformity.

[0016]

EXAMPLES Example 1 A phase change medium structure and an information recording method will be described. As shown in FIG. 1 and FIG. 7, the phase-change recording medium of the present invention is different from the conventional phase-change recording medium in the shape of the supporting substrate, but the other layer structure and layer material are the same. . The material of the support substrate 101 shown in FIG. 1 is polycarbonate, and the plate thickness is 1.2 mm. The material of the metal layer 102 is Ag, and the film thickness is 140 n.
m. The material of the first dielectric layer 103 is ZnS-Si.
It is O ₂ , and the film thickness is 20 nm. Phase change recording layer 10
The material of No. 4 is AgInSbTe, and the film thickness is 17 nm. Ratio of Sb and Te in AgInSbTe Sb
/ Te is 2.5. The material of the second dielectric layer 105 is ZnS—SiO ₂ , and the film thickness is 20 nm. Polycarbonate support substrate 10 having a predetermined concavo-convex shape
Each layer was formed on 1 by a high frequency sputtering method in an Ar atmosphere. Reference numeral 108 in FIG. 1 indicates the irradiation direction of the laser beam. The wavelength of the laser beam is 405 nm
And the NA of the objective lens is 0.85. Here, recording is performed on the concave portion 207.

Here, a recording strategy for irradiating a laser beam is shown in FIG. This is a recording strategy when recording marks M1 to M7. Mark length is M1 <M7
The recording strategy when recording marks having the relationship of is shown. P1, P2, and P3 indicate power levels. P1 =
3mW, P2 = 1.5mW, P3 = 0.1mW,
There is a relationship of P1>P2> P3. T1 indicates the time for holding the power level at the P1 level, and T3 indicates the time for holding the power level at the P3 level. When recording the M1 mark, T1 = 4n
Sec, T3 = 5nsec. When recording the M7 mark, T1 = 15 nsec and T3 = 40 nsec were set. When recording any mark from M1 to M7, T1 ≦ T
T1 and T3 were changed as long as the relationship of 3 was satisfied. Figure 5
The recording results of the phase-change recording medium 500 according to Example 1 are shown in FIG. FIG. 5A is a sectional view of the supporting substrate 501, and FIG.
(B) shows a plan view corresponding to the cross section and the shape of the phase change recording mark 5021. Track pitch P is 300n
The width (W1) of the concave portion 507 is 200 nm, and the width (W2) of the convex portion 506 is 100 nm. Groove depth is 3
It is 0 nm. Recording is performed in the concave portion 507, and M1 to M7 and the mark length are set to 7 by using the recording strategy shown in FIG.
Changed in stages.

In the layer structure shown in FIG. 1, since the recess 507 functions as a heat reservoir, the width of the recording mark 5021 matches the width of the recess 507. The relationship between the mark width M, the beam diameter Φ, and the track pitch P is M = 1.97 × P−Φ
It has become. As shown in FIG. 5, the shortest mark length M1
To the longest mark length M7, the recording marks 5021 have a width of 200 nm. Cross write does not occur even in the portion where the longest mark M7 is adjacent. Further, the beam was not applied to the recording mark 5021 on the adjacent track, and the crosstalk could be suppressed.

(Comparative Example 1) In Comparative Example 1, recording was performed using the phase change recording medium 100 shown in FIG. 7 with the same recording strategy as in Example 1. The recording result is shown in FIG.
FIG. 6A is a cross-sectional shape of the supporting substrate 600, and FIG.
Shows a plan view corresponding to the cross-sectional shape and the shape of the phase change mark 6021 formed on the recording layer. The track pitch P is 300 nm, the width W1 of the recess 607 is 150 nm,
The width W2 of the convex portion 606 is 150 nm. Groove depth is 3
It is 0 nm. Recording is performed on the convex portion 606, and M1 to M7 and the mark length are set to 7 by using the recording strategy shown in FIG.
Changed in stages. The shortest mark length M1 is 100.
and the longest mark length M7 is 370n.
It was m. In the conventional recording medium shown in FIG. 7, the width of the mark increases with the length of the mark. Track pitch 300n
In the case of m, cross write occurred in the portion where the M7 mark was adjacent.

Example 2 In Example 2, recording was performed using the phase-change recording medium 100 shown in Example 1. The recording strategy at this time is shown in FIG. P1, P2, P3
Indicates the power level. P1 = 3mW, P2 = 1.5m
W and P3 = 0.1 mW, and P1>P2> P3. T1 indicates the time for holding the power level at the P1 level, and T3 indicates the time for holding the power level at the P3 level. When recording the M1 mark, set T1 = 10 nsec, P1,
Modulate the power level between P2. When recording the M2 mark, T1 = 18 nsec is set and the power level between P1 and P2 is modulated. The marks M3 to M7 modulate the power level between P1, P3, and P2 as in the first embodiment. As a result, the mark length is M3 or less and about 10
When recording a recording mark of 0 nm or less, as a recording strategy, a minute mark is recorded by power level modulation between P1 and P2. With this strategy, long pulses can be used to record marks of the same length. As a result, a light emission waveform close to a rectangular wave is generated, and the in-plane variation of the mark length is
It can be further reduced. The mark length is M3 or more and about 1
When the thickness is 00 nm or more, as shown in FIG.
The laser power is modulated between 2 and P3 for recording. As a result, it is possible to form a recording mark having a constant mark width M while suppressing variations in the mark length regardless of the mark length.

Table 1 shows the results of comparing Example 1, Example 2, and Comparative Example 1 with respect to the mark shape of M1. The dimensions of M1 were measured using an electron microscope. The standard deviation indicates the in-plane variation of the mark width and the mark length.
In the case of Examples 1 and 2, the phase change mark is recorded following the groove. As a result, the in-plane variation (standard deviation) of the mark width can be reduced as compared with Comparative Example 1. The recording strategy of the second embodiment records the M1 mark by power level modulation between P1 and P2. With this recording strategy, in-plane variation (standard deviation) of the mark length can be reduced as shown in Table 1.

[Table 1]

[0022]

As described above, in the phase-change recording medium of the present invention, the spread of the phase-change recording mark in the radial direction of the disk can be suppressed, and the cross write when the track pitch is reduced can be prevented. Further, the smoothness of the disk surface can be improved to reduce disk noise, and the strength of the recording medium can be improved to prolong the service life. In the information recording method of the present invention, the mark length can be controlled according to the recorded information. Further, in particular, it is possible to reduce the variation in the disc surface of the minute marks.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure of a phase change recording medium of the present invention.

FIG. 2 is a schematic diagram showing a recording state in the phase change recording medium of the present invention. (A) is a cross-sectional view of a phase change recording medium,
(B) is a plan view corresponding to (a).

FIG. 3 is a schematic diagram illustrating a recording strategy in the information recording method of the present invention.

FIG. 4 is a schematic diagram illustrating a recording strategy in the information recording method of the present invention.

FIG. 5 is a schematic diagram showing a recording state in a conventional phase change recording medium. (A) is a cross-sectional view of a phase change recording medium,
(B) is a plan view corresponding to (a).

FIG. 6 is a schematic diagram showing a recording state in the phase change recording medium of the present invention. (A) is a cross-sectional view of a phase change recording medium,
(B) is a plan view corresponding to (a).

FIG. 7 is a cross-sectional view showing a layer structure of a conventional phase change recording medium.

[Explanation of symbols]

100, 200, 500, 600, 700 Phase change recording medium 101, 701 Support substrate 102, 702 Metal layer 103, 703 First dielectric layer 104, 704 Phase change recording layer 105, 705 Second dielectric layer 106 , 206, 506, 706 Convex portion 107, 207, 507, 707 Recessed portion 108, 708 Beam irradiation direction and irradiation position 2021, 5021, 6021 Phase change recording marks 2022, 5022, 6022 Beam diameter M Mark width M1 to M7 Mark length P Track pitches P1, P2, P3 Laser power level T1 Time to hold laser power level P1 T3 Time to hold laser power level P3 W1 Recess width W2 Recess width

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 534 G11B 7/24 535H 535 538 538E 538 561N 561 B41M 5/26 XF term (reference) 2H111 EA04 EA12 EA23 EA32 EA48 FA21 FA23 FA28 FB04 FB05 FB06 FB09 FB12 FB17 FB21 FB28 FB30 5D029 JA04 JB11 JB18 JB45 JB46 JB47 LA16 MA13 WA29 WB11 WD03 WD11 WD16 5D090 AA01 BB05 CC01 DD01 DD05 EE02 GG07

Claims (8)

[Claims] 1. A phase change recording medium for recording information by irradiating a laser beam, wherein the recording medium includes at least a supporting substrate, a metal layer, a first dielectric layer composed of one or more layers, and a phase change type recording medium. Recording layer, a recording medium having a layer of a second dielectric layer consisting of one or more layers, provided a spiral or concentric concavo-convex portion on the surface of the recording medium, wherein the concave portion has a convex width. A phase-change recording medium, characterized in that information is recorded on the recesses wider than the width of the section. 2. The phase-change recording medium according to claim 1, wherein the phase-change recording layer comprises Sb and Te having an atomic ratio (Sb / Te) of Sb and Te in a range of 1 to 4, A phase-change recording medium containing at least one element selected from the group consisting of Ag, In, Ge, Ga, Al, Sn, B and Si. 3. The phase change recording medium according to claim 1, wherein the metal layer is Ag alone or Ag and In, Ge, Ga, Al, Sn,
A phase-change recording medium comprising a layer containing at least one element selected from the group consisting of B and Si. 4. The phase change recording medium according to claim 1, wherein the second dielectric layer is a single layer of silicon nitride or a stack of silicon nitride and a dielectric material. Phase change recording medium. 5. A recording method on a phase-change recording medium according to claim 1, wherein the wavelength of the laser beam is λ, the numerical aperture NA of the objective lens is
The track pitch of the phase-change recording medium is P, the mark width of the recording mark is M, and the beam diameter Φ defined by 1 / e ² is 0.
Assuming that 82 × λ / NA, the mark width M of the recording mark is (1.8 × P−Φ) ≦ M ≦
An information recording method characterized by being in the range of (2.2 × P−Φ). 6. A method for recording information on a phase-change recording medium according to claim 1, wherein the laser power is modulated between power levels having a relationship of P1>P2> P3. Power level P1 to record
Let T1 be the time for holding at T3 and T3 be the time for holding at P3 level of the power level for recording information, and change the mark length by changing the length of T1 and T3 while maintaining the relationship of T1 ≦ T3. Information recording method characterized by. 7. A method for recording information on a phase-change recording medium according to claim 1, wherein the laser power is modulated between power levels having a relationship of P1>P2> P3. The information recording method is characterized in that the laser power is modulated between the power level P1 for recording and the power level P2 for erasing information, and the length of the holding time T1 is changed to change the mark length. 8. The recording method on the phase-change recording medium according to claim 7, wherein the laser power is modulated between the power levels P1 and P2 according to the mark length, and the time T1 is maintained. Information recording method for changing length and T
An information recording method, characterized in that the mark length is changed by changing the lengths of T1 and T3 while maintaining the relationship of 1 ≦ T3, and changing the length of T1 and T3.