JPH11321094A - Phase change optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To repeatedly record at a high recording density with respect to a phase change optical recording medium of a type excellent in random access, such as a CAV method, which performs recording at a different recording linear velocity depending on a part of the medium. Clarify the composition of the recording layer for improving the characteristics. SOLUTION: Regarding a phase change optical recording medium 1 whose recording linear velocity differs depending on a position in a radial direction of the medium, a recording layer 4 comprises Sb and Te as essential elements, a group Ib element, a group Vb element and a group VIb.
It is based on a phase change recording material having a group III element. The recording layer 4
Contains at least one metastable crystal phase and the space group Fm3m
2 shows a change in optical properties in a phase transition between a crystallized state having one or a plurality of crystalline phases and an amorphous state. Further, the composition in the atomic ratio of the recording layer 4 is
(Ib) _a (Vb) _x (VIb) In the composition formula represented by _1-ax , Vb
X representing the composition of group element is 0.72 ≦ x + 2a ≦ 0.80
And there is a difference in the composition of the recording layer 4 in the medium radial direction in accordance with the change in the recording linear velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable phase-change optical recording medium for recording and reproducing information by irradiating a light beam with an optical change in a recording layer material.

[0002]

2. Description of the Related Art As one of optical recording media capable of recording, reproducing and erasing information by irradiating a laser beam, a so-called phase-change optical recording medium utilizing a transition between a crystal and an amorphous phase or between a crystal and a crystal phase. Is well known. this is,
Since overwriting with a single beam is possible and the optical system on the drive side is simpler, it is applied as a computer-related or recording medium for video / audio.

As one of the recording materials, (Sb _x Te
_1-x) those represented by M _y a composition formula, for example, JP-A-1
-277338. here,
“M” is Ag, Al, As, Au, Bi, Cu, Ga,
It is at least one element selected from Ge, In, Pb, Pt, Se, Si, Sn and Zn, and the composition range is set to 0.4 ≦ x <0.7 and y ≦ 0.2. Have been. However, in the case of the recording layer having such a structure, it is 0.4 ≦ x <0.7 that preferable recording characteristics are obtained.
In the range of x ≧ 0.7, there was a problem in the erasing characteristics in repeated recording.

In a similar material system, (Sb _x Te _1-x ) _a
A phase change recording material represented by _a composition formula of M _1-a (M is at least one element of Au, Ag or Cu) is disclosed in, for example, JP-A-9-71049. This composition range is 0 <x <0.9 and 0 <a <1;
Its structure is Sb ₂ Te ₃ + Sb. This Sb ₂ Te ₃ +
The eutectic composition near the Sb pseudo two elements, in an Sb and Sb ₂ Te ₃ there is a difference in the crystallization rate, the boundary between the amorphous portion and the crystallized portion, the grain boundary between Sb and Sb ₂ Te ₃ Disturbance caused by influence. For this reason, CD-RW (Compactact Disk)
-It can be applied to a medium with a relatively low recording density such as Rewritable, but the recording density is about four times as high as that of a CD-RW, and is at least as high as a DVD (Digital Versatile Disk) -RAM or DVD-ROM. With a recording density medium, it is difficult to obtain good recording characteristics.

[0005]

That is, Sb-Te-M
In the system, based on the structure of Sb ₂ Te ₃ , Sb ₂ Te ₃ + Sb, Ag, Al, As, Au, Bi, Cu, G
a, Ge, In, Pb, Pt, Se, Si, Sn and Z
Only a recording material in which the stability of the amorphous state, the high-speed erasing property, or the repetitive recording characteristic is improved using any one of n as an additive element. Thus, S
Heretofore, there is no knowledge about a b-Te-M recording material having a single or a plurality of metastable crystal phases belonging to the space group Fm3m. Furthermore, there is no prior art in which a metastable crystal phase can exist and a composition region having a durability against thermal shock during repeated recording is defined.

Therefore, the relationship between the composition of the recording layer having a metastable crystal phase and the repetitive recording characteristics, the relationship between the composition and the crystal structure, and the relationship between the crystal structure and the repetitive recording characteristics are not clear. , High recording density, eg DVD-R
There is no phase-change optical recording medium having a recording density equivalent to that of an AM or DVD-ROM and having good recording characteristics. In addition, the relationship between the composition range with good repetitive recording characteristics and the recording linear velocity is not clear.

[0007] In addition, there has been no knowledge about the composition for controlling the crystallization rate while maintaining good repetitive recording, and CAV (Constant Angular Velocity) has not been known.
As in the case of phase change optical recording media where the recording linear velocity changes depending on the location, such as city) recording and MCAV (Modify CAV) recording, there are no recording media with high recording density and good repetitive recording characteristics over the entire surface. is there.

Accordingly, the present invention provides a CAV system or MC
For a phase change optical recording medium of the type excellent in random access that performs recording / reproduction at different recording linear velocities depending on the part of the medium by the AV system, a recording layer having an excellent recording density and a repetitive recording characteristic in a wide recording linear velocity region. An object of the present invention is to provide a phase-change optical recording medium having a clarified composition and the like.

[0009]

According to the first aspect of the present invention,
In a phase change optical recording medium in which a recording linear velocity varies depending on a position in a radial direction of the medium, a phase change recording material having a group Ib element, a group Vb element, and a group VIb element with Sb and Te as essential elements is used as a recording layer. Shows a change in optical properties in a phase transition between a crystallized state and an amorphous state having at least one metastable crystal phase and one or more crystal phases belonging to the space group Fm3m, In the composition formula in which the composition at the ratio is represented by (Ib) _a (Vb) _x (VIb) _1-ax , _x representing the composition of the Vb group element is 0.72 ≦
It is set in the range of x + 2a ≦ 0.80, and there is a difference in the composition of the recording layer in the medium radial direction in accordance with the change in the recording linear velocity.

According to a second aspect of the present invention, in the phase-change optical recording medium according to the first aspect, the crystalline phase in the crystallized recording layer is a metastable solid solution single phase.

According to a third aspect of the present invention, in the phase change optical recording medium according to the first or second aspect, the recording layer has at least one element of Ag and Au, and the element concentration of the recording layer is closer to the inner peripheral side. Is set smaller on the outer peripheral side.

According to a fourth aspect of the present invention, in the phase change optical recording medium of the third aspect, the composition of the recording layer in the atomic ratio is (Ag, Au) _a (Vb) _x (VIb) _1-ax . 0.05 ≦ a ≦
It is set within the range of 0.08.

According to a fifth aspect of the present invention, in the phase change optical recording medium according to the third aspect, the composition of the recording layer in the atomic ratio is (Ag, Au) _a (Vb) _x (VIb) _1-ax . The composition of the recording layer, which is represented by a composition formula and belongs to a portion in the medium radial direction corresponding to a recording linear velocity of 2 to 3 m / s, is 0.03 ≦ a ≦
It is set within the range of 0.07.

According to a sixth aspect of the present invention, in the phase change optical recording medium of the third aspect, the composition of the recording layer in the atomic ratio is (Ag, Au) _a (Vb) _x (VIb) _1-ax . The composition of the recording layer, which is represented by a composition formula and belongs to a portion in the medium radial direction corresponding to a recording linear velocity of 3 to 4 m / s, is 0.02 ≦ a ≦
It is set within the range of 0.06.

According to a seventh aspect of the present invention, in the phase change optical recording medium according to the third aspect, the composition of the recording layer in the atomic ratio is (Ag, Au) _a (Vb) _x (VIb) _1-ax . The composition of the recording layer, which is represented by a composition formula and belongs to a portion in the medium radial direction corresponding to a recording linear velocity of 4 to 6 m / s, is 0.01 ≦ a ≦
It is set within the range of 0.05.

According to an eighth aspect of the present invention, in the phase change optical recording medium according to the third aspect, the composition of the recording layer in the atomic ratio is (Ag, Au) _a (Vb) _x (VIb) _1-ax . The composition of the recording layer, which is represented by a composition formula and belongs to a portion in the medium radial direction corresponding to a recording linear velocity of 6 to 8 m / s, is 0.005 ≦ a ≦
It is set within the range of 0.04.

First, the recording layer in the phase-change optical recording medium according to the first aspect of the present invention comprises S
With b and Te as essential elements, it has a group Ib element, a group Vb element and a group VIb element. In particular, as the group Ib element, A
g, Cu and / or Au, Vb group elements as Sb, A
Te, S and / or Bi and / or Bi and VIb group elements
Or a Se-based recording material, wherein the recording layer has a property that optical properties change in a phase transition between one or more crystalline phases including at least a metastable crystalline phase and a metastable amorphous phase. . The composition is such that Sb and Te are essential elements and the composition in the atomic ratio of the recording layer is (Ib)
_{In the} composition formula represented by _a (Vb) _x (VIb) _1-ax , _x representing the composition of the Vb group element is set in the range of 0.72 ≦ x + 2a ≦ 0.80. At the same time, the crystal phase in such a recording layer belongs to the space group Fm3m. Such a metastable crystal phase contains Sb or Te as an essential element and contains Ib-Vb
At least one of -VIb solid solution, Vb-VIb solid solution, and (Vb) ₃ (VIb) crystal phase. As a specific material of such a metastable crystal phase, for example, Ag-Sb-Te
In a system, Ag-Sb-Te solid solution, Sb-Te solid solution, at least one of Sb ₃ Te. These metastable crystal phases belong to the space group Fm3m, and have a lattice constant of 0.615 ± 0.02 nm or a long-period crystal phase in which the elements in the crystals of the space group Fm3m are ordered. One of According to the above composition formula, the region where these metastable crystal phases exist is a region where the condition of 4a <1 is satisfied.

Here, the one in which the crystallized portion of the recording layer is composed of a single metastable crystal phase is the invention according to claim 2, which is an Ib-Vb-VIb solid solution. This includes, for example, Ag-Se-Te, Au-Sb-Te, Au-A
g-Sb-Bi-Te-Se, (Au, Ag, Cu)-
(Sb, Bi, As)-(Te, Se, S).

In addition, any combination of the above metastable crystal phases may be in a mixed phase state composed of a plurality of crystal phases consisting only of the metastable phase. Further, other stable crystal phases having a lattice matching relationship with these metastable phases, for example, AgSbTe
_It may be in a mixed phase state containing a crystal phase such as ₂ .

Each case has a crystal structure based on a face-centered cubic lattice having a lattice constant of about 0.615 nm. In order to obtain a good mark shape, the crystallized portion of the recording layer is formed of a single-phase metastable Ib-Vb-VI.
b It is preferable that the solid solution is composed of only a solid solution. Even when an excessive thermal shock at the time of initial crystallization is unavoidable and a unavoidable generation of a phase-separated crystal phase occurs, mainly a crystal phase belonging to the space group Fm3m having a lattice matching relationship with each other is generated as described above, and the space group is generated. Other precipitates that do not have a lattice matching relationship with the crystal phase of Fm3m, for example, Sb, Sb ₂ Te ₃ , or an amorphous phase in the crystallized portion do not appear as much as possible, and are in the space group Fm3m including the metastable phase. An initial crystallization process suitable for the formation of the belonging crystal phase is employed. In the present invention, there may be a composition gradient in a film thickness direction or an in-plane direction,
Also included are laminated films of the above phases.

According to the first aspect of the present invention, one of the features is that the phase change recording material of the recording layer is
In order to obtain a crystallization speed corresponding to a predetermined recording linear velocity, an in-plane distribution is generated in the composition of the recording layer. For example, the crystallization speed of the recording layer tends to decrease as the group Ib element and / or group VIb element increases, and increase as the group Vb element increases.

In particular, it contains Ag and / or Au (Ag,
In the (Au)-(Vb)-(VIb) recording material system, the concentration dependency of Ag and / or Au is remarkable, and the concentration of Ag and / or Au in the region where the recording linear velocity is high is lowered. That is, as in the invention according to claim 3, Ag and / or Ag on the outer peripheral side of the recording layer are provided.
Alternatively, if the Au concentration is made smaller than the Ag and / or Au concentration on the inner peripheral side, the recording linear velocity in the inner peripheral part is slow, and the CAV is low.
It can correspond to records and the like. In this case, the composition is
In order to maintain good repetitive recording characteristics over the entire surface,
The range is set so that 0.72 ≦ x + 2a ≦ 0.80 is satisfied.

That is, according to the first aspect of the present invention, S
Group Ib element with b and Te as essential elements -Vb group element-
The phases that can appear in the crystal phase of the recording material composed of Group VIb elements include simple substances, binary and ternary compounds, alloy phases and solid solutions, and among them, Ib-Vb-VIb, Vb-VIb and V
b, for example, AgSbTe _2, metastable Sb ₃ Te, metastable Sb-Te solid solution, Sb ₂ Te _3, Sb is likely to emerge. Among these, general formulas IbVbVIb, such as AgSbTe ₂ , metastable Sb ₃ Te, metastable Sb-Te solid solution, etc.
_2. The structures of the crystals represented by the metastable Vb ₃ VIb, the metastable Vb-VIb solid solution, and the metastable Ib-Vb-VIb solid solution belong to the space group Fm3m, and the lattice constant is near 0.615 nm. Are in lattice matching with each other.
First, the crystallization part of the recording layer is a single-phase metastable Ib-Vb-VI
b When the solid solution alone is used, there is no grain boundary, or even if a crystal grain boundary exists, the crystal grain boundary has a relatively good lattice junction, and no large void exists in the crystal grain boundary. No unevenness in thermal conductivity. In this case, a smooth boundary between the amorphized portion and the crystallized portion faithfully reflecting the intensity distribution and the temporal profile of the light beam is obtained, and a good jitter value is obtained in a high recording density region. The composition region where the metastable crystal phase has high stability against thermal shock during recording is such that the value x of the recording layer represented by the composition formula (Ib) _a (Vb) _x (VIb) _1-ax is 0.72. ≦ x + 2a ≦
0.80 and satisfy 4a <1, which means that even if the metastable Ib-Vb-VIb solid solution undergoes the first phase transition and enters a mixed phase state,
Since it is composed of a plurality of crystal phases including a metastable phase having a lattice matching relationship with each other, it is also a composition region in which relatively good recording characteristics can be maintained.

In addition, between a plurality of crystal phases, for example, Ib-V
Since there is a difference in the crystallization speed between the b-VIb stable crystal phase and the Vb-VIb metastable crystal phase, it is preferable that the main part is occupied by the metastable phase. preferable. In particular, Ag-Sb-Te based recording materials,
4a = 1, in a composition region where a metastable phase is unlikely to exist,
The crystallization speed is slow, and good characteristics cannot be obtained in a normal recording linear velocity region.

In the case where the crystallized portion of the recording layer is composed of a plurality of crystal phases that are not in a lattice matching relationship as in the prior art,
If the conformity of the planes at the crystal grain boundaries is not good, vacancies and segregation occur at the grain boundaries, and the thermal conductivity becomes uneven at the grain boundaries. Furthermore, since the crystallization speed generally differs from grain to grain,
The boundary between the crystal and the amorphous portion tends to reflect the crystal grain boundary, and the boundary between the amorphous portion and the crystallized portion is disturbed, so that good characteristics cannot be obtained in a high recording density region. Further, when the crystal grain size is set to a fine crystal of several nm, smoothness of the crystal grain boundary can be obtained, but there is a problem in realizing high recording density. At grain boundaries that do not have a lattice-matching relationship with each other, undesired phenomena such as a decrease in crystallization speed and corrosion from grain boundaries occur due to an increase in strain and interface energy at the interface portions. Not suitable for recording density. In this regard, in the present invention,
Even when the crystallized portion of the recording layer is composed of a plurality of crystal phases, the generated crystal phases belong to the same space group Fm3m and have close lattice constants, so that the grain boundaries are as good as in the case of a single phase. Has become a joint. For this reason, although there is a difference in the crystallization speed, the non-uniformity of the heat conduction is relatively small, and the recording characteristics are similar to those of the single phase.

In the initial crystallization of the phase-change optical recording medium according to the present invention, an initialization method suitable for the precipitation of a metastable phase, for example,
An initialization method using a laser beam or the like is employed. A particularly preferred structure is (Ib) _a (Vb) _x (VIb) _1-ax metastable solid solution single phase (Claim 2).

The crystallization rate of the Ib-Vb-VIb-based recording layer depends on the composition. As the concentration of the Ib group element or the VIb group element in the recording layer increases, the recording layer becomes more suitable for the low recording linear velocity side, and as the concentration of the Vb group element increases, the recording layer becomes more suitable for the higher recording linear velocity side. There is a certain correspondence between the crystallization rate and the composition. In particular, Ag, Au or Ag + A
The concentration of u has a great influence on the crystallization rate. That is, A
As the g + Au concentration increases, the crystallization speed decreases.

In the inventions according to claims 4 to 8, in particular,
An appropriate combination of a recording linear velocity and a composition of a recording layer when a strategy (light emitting pattern of a laser diode) used for a CD-RW or the like is used is disclosed. That is, the recording layer contains Ag and / or Au, and the composition in the atomic ratio of the recording layer is represented by a composition formula of (Ag, Au) _a (Vb) _x (VIb) _1-ax , where x is 0. Assuming that it is within the range of 72 ≦ x + 2a ≦ 0.80, the recording linear velocity is 1-2 m / s.
The composition of the recording layer belonging to a portion in the radial direction of the medium corresponding to the medium radius is set within the range of 0.05 ≦ a ≦ 0.08 (claim 4), and the medium radius corresponding to the recording linear velocity of 2-3 m / s. The composition of the recording layer belonging to the portion in the direction is 0.03 ≦ a ≦
0.07 (claim 5), the recording linear velocity 3
The composition of the recording layer belonging to the portion in the medium radial direction corresponding to ４4 m / s is set in the range of 0.02 ≦ a ≦ 0.06 (claim 6), and the recording linear velocity is 4 to 6 m / s. The composition of the recording layer belonging to the corresponding part in the radial direction of the medium is 0.1%
01 ≦ a ≦ 0.05 (claim 7),
The composition of the recording layer belonging to a portion in the medium radial direction corresponding to a recording linear velocity of 6 to 8 m / s is 0.005 ≦ a ≦ 0.04
(Claim 8).

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. The layer structure of the phase change optical recording medium of the present invention is not particularly limited, and can be applied to a known arbitrary structure. An example of the structure will be described with reference to FIG. FIG. 1 is a conceptual diagram showing an example of the layer configuration of the phase change optical recording medium 1. In the phase change optical recording medium 1, on a polycarbonate substrate 2 having a guide groove, ZnS · SiO ₂
First protective layer 3 made of AgSbTe recording layer 4, ZnS
A second protective layer 5 made of SiO ₂ , an Al.Ti reflective heat radiation layer 6, and an environmental protective layer 7 made of a UV curable resin are sequentially laminated. Such a phase-change optical recording medium 1 has, for example, an MCAV whose recording linear velocity differs depending on the position in the medium radial direction.
It is a specification that is performed according to the method.

In the present embodiment, with respect to such a phase change optical recording medium 1, the composition and the like of the recording layer 4 are clarified. That is, the recording layer 4 is basically formed of a phase-change recording material having Sb and Te as essential elements and having an Ib group element, a Vb group element, and a VIb group element. In addition, the method utilizes a change in optical properties in a phase transition between a crystallized state having one or more crystal phases including at least one metastable crystal phase and an amorphous state. Here, in the composition formula expressed by (Ib) _a (Vb) _x (VIb) _1-ax , where the composition at the atomic ratio of the recording layer 4 is 0.72≤x + 2a≤
It is set within the range of 0.80, and one or more crystal phases are considered to belong to the space group Fm3m. In addition, there is a difference in the composition of the recording layer 4 in the medium radial direction corresponding to the change in the recording linear velocity of the phase-change optical recording medium 1.

In the present embodiment, the basis for adopting such a composition or the like is clarified based on a specific measurement example. That is, the relationship between the composition of the recording layer 4, the recording linear velocity, and the number of repetitive recordings (recordable times) was specifically measured for the phase-change optical recording medium 1 having the layer structure shown in FIG. Table 1 and Table 2 show the results of fifteen kinds of recording layer samples, namely, recording layer 15. Here, the recording strategy (the emission pattern of the laser diode during recording)
Used the one adopted in the CD-RW. The number of recordable times is determined by the maximum number of repetitive recordings in which the value of jitter σ / Tw normalized by the window width Tw does not exceed 13%.

[0032]

[Table 1]

[0033]

[Table 2]

In Tables 1 and 2, the number of recordable times is 1000
The recording linear velocity which was confirmed to be equal to or more than
= 0.08, 1-2 m / s (recording layer 1), Ag
1-3 m / s (recording layer 2) for density a = 0.07, 1-4 m / s for Ag density a = 0.06
(Recording layer 3), 1 to 6 for Ag concentration a = 0.05
m / s (recording layer 4), Ag concentration a = 0.04 and a =
2 to 8 m / s for 0.03 (recording layers 5, 6, 10
~ 14), 3 to 8 m / for Ag concentration a = 0.02
s (recording layer 7), 4 to 4 for Ag concentration a = 0.01
For 8 m / s (recording layer 8) and Ag concentration a = 0.005, it becomes 6 to 8 m / s (recording layer 9). That is, the recording linear velocity is 1-2 m / s, 2-3 m / s, 3-4 m / s, 4-6 m
/ S, Ag concentration a corresponding to each of 6 to 8 m / s is 0.05 ≦ a ≦ 0.08, 0.03 ≦ a ≦ 0.0, respectively.
7,0.02 ≦ a ≦ 0.06,0.01 ≦ a ≦ 0.0
5, 0.005 ≦ a ≦ 0.04. Similar results can be obtained by replacing some or all of Ag with Au.

The initial crystallization of the recording layers in Tables 1 and 2 was performed by laser beam irradiation except for the sample recording layer 15. Initial crystallization of the sample recording layer 1 was performed by lamp annealing. According to the measurement results of the sample recording layers 5, 10 to 14, (Ib) _a (Vb) _x (VIb) _1-ax
It can be seen that, in the composition formula (here, Ag _a Sb _x Te _1-ax ), when x is in the range of 0.72 ≦ x + 2a ≦ 0.80, the number of repetitive recordings is good. In order to ensure the uniformity of the repetitive recording characteristics over the entire surface, it is preferable that the value of the parameter x + 2a is constant, and it is particularly preferable that this value be ± 0.02.

By the way, even when the recording layer has the same composition as that of the present invention, the sample recording layer 15 does not precipitate Sb, Sb ₂ Te _3, etc., which are precipitates when the metastable phase is decomposed. This is unsuitable for high recording densities. The metastable phase separates into a stable phase by prolonged high-temperature annealing.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A phase change optical recording medium 1 having the layer structure shown in FIG. 1 is used, and the number of repetitive recordings, the composition of the recording layer 4 and the initialization when the composition of the recording layer 4 has a radial distribution. Table 3 shows the relationship with the subsequent crystal structure in Examples 1 to 3, in comparison with Comparative Example 1 in which the composition does not have a concentration distribution in the radial direction.

[0038]

[Table 3]

In Example 1, a composition gradient depending on the radial position r is provided in the Ag concentration as the Ib element, and the Sb as the Vb group element is adjusted so that the number of times of repetitive recording is optimized accordingly.
The concentration of Te which is a group b element and a group VI element has a gradient.
Thus, in MCAV recording at 900 rpm,
High repetitive recording over the entire surface is now possible.

In the second embodiment, the MCA at 1200 rpm is used.
This corresponds to V recording, and there is a gradient in the concentration of Ag and Au. Further, Bi is added as a Vb group element and Se is added as a VI group element. In the case of Example 2, too, the repetitive recording characteristics over the entire surface are good.

The third embodiment corresponds to MCAV recording at 600 rpm, but Au is the only Ib group element.

Incidentally, according to the repetitive recording characteristics of Comparative Example 1 having no concentration distribution in the composition, the repetitive recording characteristics are good at the radial position where the optimum recording linear velocity is ensured,
From this, it can be seen that recording (amorphization) becomes difficult on the inner peripheral side, and erasing (crystallization) becomes difficult on the outer peripheral side, and uniform repetitive recording characteristics over the entire surface cannot be obtained.

As Comparative Example 2, the case where a gradient was applied to the Sb concentration which affects the crystallization rate of the Ag-Sb-Te system, that is, (Ag-Sb-Te) _1-γ (Sb) _γ Table 4 shows the repetitive recording characteristics when the crystallization rate was optimized by changing the value of γ in the composition formula shown below.

[0044]

[Table 4]

It can be seen that as the composition condition deviates from the range of 0.72 ≦ x + 2a ≦ 0.80, the number of repetitive recordings sharply deteriorates. That is, the composition condition 0.72 ≦ x + 2
a ≦ 0.80 can be said to be a parameter specific to the present invention, which indicates the stability condition of the metastable phase. In particular, when the number of repetitive recordings is good when there is no influence of impurities, x + 2a = 0.75
It is. This condition also matches other characteristics, for example, conditions under which the storage characteristics of the overwrite shelf or the like are good.

On the other hand, impurities such as C, B,
When N, Pb, Sn, Zn, a transition metal element, or the like is added, the above-mentioned optimum condition x + 2a = 0.75 is slightly shifted depending on the bonding state of impurities and the state of segregation at the interface of the protective layer. For example, when nitrogen is added to the recording layer, x + 2a
> 0.75. However, the present invention corresponds to the case where the amount of impurities is as small as about 5 at.% Or less. When no impurities are added or when there is no in-plane distribution of the amount of impurities added,
In order to maintain good repetitive recording characteristics over the entire surface, it is particularly preferable to keep the value of the parameter x + 2a constant.
It is preferable to be within 02.

[0047]

According to the phase change optical recording medium of the first aspect of the present invention, a type excellent in random access, such as a CAV system or an MCAV system, which performs recording / reproducing at a different recording linear velocity depending on a part of the medium. With regard to the phase change optical recording medium described above, the repetitive recording characteristics at a high recording density can be improved.

According to the second aspect of the present invention, since the crystal phase in the recording layer in the crystallized state is a metastable solid solution single phase, it is suitable for the precipitation of a metastable phase.

According to the third aspect of the present invention, Ag and / or
Alternatively, since the element concentration is set to be smaller on the outer peripheral side than on the inner peripheral side in the composition containing Au, the slowing of the recording linear velocity and the slowing of the crystallization speed can be corresponded, and the high The repetitive recording characteristics at the recording density can be improved.

According to the fourth to eighth aspects of the present invention, it is possible to provide an appropriate combination of the recording linear velocity and the composition of the recording layer when a strategy used for, for example, a CD-RW is used. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a layer configuration of a phase change optical recording medium according to an embodiment of the present invention.

[Explanation of symbols]

 4 Recording layer

Claims (8)

[Claims] 1. A phase change optical recording medium in which a recording linear velocity varies depending on a position in a radial direction of a medium, wherein a phase change recording material having a group Ib element, a group Vb element and a group VIb element with Sb and Te as essential elements is used as a recording layer. age,
The recording layer includes at least one metastable crystal phase, and has a single or a plurality of crystal phases belonging to a space group Fm3m, and shows a change in an optical property in a phase transition between a crystallized state and an amorphous state; In the composition formula represented by (Ib) _a (Vb) _x (VIb) _1-ax ,
x representing the composition of the group b element is 0.72 ≦ x + 2a ≦ 0.8
A phase change optical recording medium, wherein the phase difference is set in a range of 0, and the composition of the recording layer has a difference in a medium radial direction in accordance with the change in the recording linear velocity. 2. The phase-change optical recording medium according to claim 1, wherein a crystal phase in the recording layer in a crystallized state is a metastable solid solution single phase. 3. The recording layer according to claim 1, wherein the recording layer has at least one element of Ag and Au, and the concentration of the element is set smaller on the outer peripheral side than on the inner peripheral side. Item 3. The phase change optical recording medium according to Item 1 or 2. 4. The composition of an atomic ratio of the recording layer is (A)
g, Au) _a (Vb) _x (VIb) ₁ -ax The composition of the recording layer belonging to a radial direction of the medium corresponding to a recording linear velocity of 1 to 2 m / s is defined as 0.05 ≦ 4. The phase change optical recording medium according to claim 3, wherein a is set within a ≦ 0.08. 5. The composition of the recording layer having an atomic ratio of (A)
g, Au) _a (Vb) _x (VIb) _1-ax The composition of the recording layer belonging to a portion in the radial direction of the medium corresponding to a recording linear velocity of 2 to 3 m / s is 0.03 ≦ 4. The phase change optical recording medium according to claim 3, wherein a is set within a range of a ≦ 0.07. 6. The composition of the recording layer having an atomic ratio of (A)
g, Au) _a (Vb) _x (VIb) _1-ax , wherein the composition of the recording layer belonging to the radial direction of the medium corresponding to the recording linear velocity of 3 to 4 m / s is 0.02 ≦ 4. The phase change optical recording medium according to claim 3, wherein a is set within a range of a ≦ 0.06. 7. The composition of the recording layer at an atomic ratio of (A)
g, Au) _a (Vb) _x (VIb) _1-ax The composition of the recording layer belonging to a radial direction of the medium corresponding to a recording linear velocity of 4 to 6 m / s is defined as 0.01 ≦ 0.01. 4. The phase-change optical recording medium according to claim 3, wherein a is set within a range of a ≦ 0.05. 8. The composition of the recording layer having an atomic ratio of (A)
g, Au) _a (Vb) _x (VIb) _1-ax The composition of the recording layer belonging to a radial direction of the medium corresponding to a recording linear velocity of 6 to 8 m / s is 0.005 ≦ a ≦ 0.04
The phase change optical recording medium according to claim 3, wherein the value is set within the range of: