JP2002264506A - Optical information recording medium and its record deleting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium having a high crystallization speed which can deal with recording by a reference clock cycle at 15 ns or lower, an excellent recording signal jitter property, and an excellent preservation stability. SOLUTION: For this optical information recording medium, at least a phase changing type recording layer is provided on a substrate. The phase changing type recording layer comprises an alloy of which the major component is a composition represented by (Sbx Te1-x )1-y Gey )1-z Auz ). (In this case, 0.70<=x<=0.95, 0.01<=y<=0.10, and 0.01<=z<=0.12 are satisfied).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium having a rewritable phase-change recording layer, and more particularly, to a high data transfer rate with a reference clock cycle of 15 ns or less during recording. The present invention relates to an optical information recording medium and a recording / erasing method having a high crystallization speed, excellent recording signal jitter characteristics, and excellent storage stability of recording marks.

[0002]

2. Description of the Related Art In an optical information recording medium having a phase change type recording layer, recording / reproducing / erasing is performed by utilizing a reflectance change accompanying a reversible change in a crystal state. Such optical information recording media, especially phase change optical disks, are being developed and put into practical use as inexpensive large-capacity recording media having excellent portability, weather resistance, impact resistance, and the like. For example, rewritable CDs such as CD-RWs have already spread,
Rewritable DVDs such as RW, DVD + RW, and DVD-RAM are being sold.

As a method of phase change recording, a reversible change between a crystalline phase and an amorphous phase is used to change the crystalline state to an unrecorded / erased state, and to change the crystalline state during recording to an amorphous state. Techniques for forming marks are currently in practical use. Normal,
The recording layer is heated to a temperature higher than the melting point and rapidly cooled to form an amorphous mark. On the other hand, the recording layer is heated and kept near the crystallization temperature for a certain period of time to be in a crystalline state. That is, generally, a reversible change between a stable crystalline phase and an amorphous phase is used.

As a material of such a phase change type recording layer, a chalcogen alloy thin film is often used. For example, GeSbTe system, InSbTe system, GeSnTe
And AgInSbTe-based alloys. These compounds are known as overwritable materials.
Overwriting is a method of overwriting without erasing before recording when recording is once again performed on a recorded medium, that is, a method of recording while erasing.

In particular, ｛(Sb ₂ Te ₃ ) _1-a (GeT
_{e) a} 1-b Sb} b (0.2 <a <0.9,0 ≦ b <0.
1) A thin film mainly composed of an alloy, or (Sb _c Te _1-c )
_d M _1-d (where 0.6 <c <0.9, 0.8 <d <
1, M is one or more elements selected from Ge, Ag, In, etc.) A thin film mainly composed of an alloy is stable in both crystalline and amorphous states, and a comparison between the two states is made. It is known that the recording material is capable of phase transition at extremely high speed. In addition, in the latter recording material, it is known that the addition of Ge is particularly effective for stabilizing the recorded amorphous mark (EP834,874). These systems also have the advantage that segregation is unlikely to occur when repeated overwriting is performed, and both alloy thin films have been put to practical use as a recording layer of a phase change optical disk.

Incidentally, the above two alloys have greatly different properties. For example, in the former, the generation frequency of crystal nuclei is high,
Crystal nuclei play an important role in crystallization of amorphous marks, whereas crystal nuclei hardly relate to crystallization of amorphous marks in the latter. In addition, both have different allowable ranges of a laser pulse irradiation method during recording, a so-called pulse division method (pulse strategy).

The latter alloy has better reproduction signal characteristics when recording is performed with the gaps between marks shortened, and is suitable for high-density recording.

[0008]

At present, recording materials have been developed with the aim of providing an optical information recording medium capable of achieving a higher recording density, enabling high-speed recording / erasing, and achieving a high transfer rate. I have. To achieve a high transfer rate, both recording and erasing must be performed at high speed,
The crystallization speed of the recording layer must be fast, and the erasing (crystallization) of the amorphous mark must be sufficiently fast.

[0009] _{(Sb c Te 1-c)} d M 1-d ( However, 0.6
<C <0.9, 0.8 <d <1, M is Ge, Ag, In
The crystallization rate of a thin film mainly containing an alloy of one or more elements selected from the above) can be controlled by the ratio of the amount of Sb to the amount of Te. That is, the crystallization rate is increased by increasing the Sb content and decreasing the Te content. However, conventionally, if the amount of Sb is greatly increased in order to increase the crystallization speed, there has been a tendency that jitter (jitter of a reproduced signal when a recorded mark portion or a portion between marks is reproduced) deteriorates. Therefore, it is difficult to obtain good jitter with a recording material having a crystallization rate higher than a certain level.

Although the cause is not always clear, when the reproduced signal waveform is observed with an oscilloscope, the reflectivity level of the crystal state is not constant but looks wide and wide, so that when Sb increases, the original reflectivity level increases. Another crystal phase having a different reflectance may appear in addition to the crystal phase. That is, in a crystal area (an area in an unrecorded / erased state), two or more phases having different reflectivities may be mixed in a state that is not sufficiently uniform with respect to the beam size.

For this reason, there has been a demand for obtaining an optical information recording medium capable of satisfying both a high crystallization speed and good reproduction signal jitter. This requirement is particularly large in a medium that can perform recording and erasing at a very high linear velocity, for example, recording and erasing with a reference clock cycle of 15 ns or less. The present invention has been made to solve the above problems, and has as its object to obtain an optical information recording medium having a high crystallization rate and excellent jitter characteristics, and a recording / erasing method suitable for the medium. .

[0012]

The gist of the present invention is to provide an optical information recording medium comprising at least a phase change type recording layer provided on a substrate, wherein the phase change type optical recording layer is composed of ((Sb _x T
e _1-x ) _1-y Ge _y ) _1-z Au _z (0.70 ≦ x ≦
0.95, 0.01 ≦ y ≦ 0.10, 0.01 ≦ z ≦
0.12) An optical information recording medium characterized by being made of an alloy having a composition represented by 0.12) as a main component.

According to the present invention, (Sb _x Te _1-x ) _1-y G
e _y (0.70 ≦ x ≦ 0.95, 0.01 ≦ y
<0.10) By adding an appropriate amount of Au to the alloy recording layer, the jitter (jitter of the reproduced signal when reproducing the recorded mark portion and the inter-mark portion) is improved in the medium having a high crystallization speed. Therefore, an optical information recording medium having a high crystallization rate and excellent jitter characteristics can be obtained.

Although it is not clear why the jitter characteristics are improved, it is observed that the addition of Au reduces the above-mentioned phenomenon that the crystal reflectivity level is not constant but looks wide and wide. From this, it is conceivable that Au may suppress the appearance of the crystal phase that appears when the amount of Sb increases. By the way, Japanese Patent Application Laid-Open No. H1-251342
Discloses a chalcogen element (S
e, Te, S), and an information recording medium having a recording layer to which Pd or Au is added for further increasing the crystallization rate, improving sensitivity, and the like.

In the composition range disclosed in the publication, the possible value of the Ge content is 5 to 80 at. % (Atomic%), and partially overlaps the composition range of the present invention. However, in the present invention, the amount of Ge that can be added is at most 10a.
t. % Will not be exceeded. This is because the addition of more than this deteriorates the jitter characteristic and cancels the jitter improvement effect by the addition of Au. On the other hand, if the amount of Ge is too large, the crystallization speed tends to decrease, so that recording at a high linear velocity becomes difficult.

Japanese Patent Application Laid-Open No. 11-240252 (US Pat. No. 6,096,399) discloses that Ge-Sb-T
Ag or Au is added at 0.2 to 2.5 at. It describes an information recording medium having a recording layer to which% is added.
But used in experimental example among Ge-Sb-Te-based alloy, the present application is different from Ge ₂ Sb ₂ Te _5. As described in the related art section, Ge-Sb-
Te-based alloys have two types of alloy thin films with greatly different properties, G
Let e ₂ Sb ₂ Te ₅ be a representative composition {(Sb ₂ Te ₃ ) _{1-a
(GeTe) a} 1-b} Sb b (0.2 <a <0.9,0 ≦
b <0.1) a thin film containing an alloy as a main component, and (Sb _c Te _1-c ) _d M _1-d (where 0.6 <c <)
0.9, 0.8 <d <1, and M is at least one element selected from Ge, Ag, In, and the like) and a thin film mainly composed of an alloy.

The publication relates to the case where the former is used as the recording layer, whereas the present invention relates to the case where the latter is used as the recording layer, and the purpose and effect of adding Au are completely different. . The present invention is intended to solve a problem peculiar to the case where the latter is a recording layer, especially when the Sb content is high and the Te content is low. Another gist of the present invention resides in a recording and erasing method characterized in that recording and / or erasing is performed on the optical information recording medium with a reference clock cycle of 15 ns or less.

That is, the optical information recording medium is:
Since the phase change speed is high and the jitter characteristics of the reproduction signal are excellent, it is possible to perform recording and erasing with excellent jitter of the reproduction signal at a high linear velocity of a reference clock cycle of 15 ns (nanosecond) or less.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, an optical information recording medium comprising at least a phase change type recording layer provided on a substrate, wherein the phase change type recording layer is ((Sb _x Te _1-x ) _1-y Ge _y )
_1-z Au _z (0.70 ≦ x ≦ 0.95, 0.01 ≦
(y ≦ 0.10, 0.01 ≦ z ≦ 0.12).

In the composition of the recording layer, a predetermined amount of Au must be contained in order to obtain a sufficient jitter improving effect, so that 0.01 ≦ z. More preferably, 0.
03 ≦ z. On the other hand, if the amount of Au is too large, the storage stability of the amorphous mark deteriorates, so z ≦ 0.12. More preferably, z ≦ 0.10. Well, Sb
And the content ratio of Te are related to the crystallization speed.
As e decreases, the crystallization speed increases. In general, a recording layer is irradiated with a light beam (laser) spot emitted from a light irradiation unit while rotating the medium at a high speed, and recording and erasing are performed while the light irradiation unit and the medium are relatively moved at a high speed. A case where the relative moving speed is high is referred to as a high recording linear speed, and a case where the relative moving speed is low is referred to as a low recording linear speed.

In a state where the recording linear velocity is high, the recording layer is once heated by the light beam spot and then rapidly cooled. That is, the temperature history of the recording layer becomes quenched, and in the recording layer having the same composition, the higher the recording linear velocity, the more the amorphous phase is likely to be formed, and the more difficult it is to form the crystalline phase. For this reason, in a medium having a high target recording linear velocity, the amount of Sb is increased to increase the crystallization speed, and in a medium having a low target recording linear velocity, the Sb amount is reduced to lower the crystallization speed. It is desirable to adjust the addition amount according to the recording linear velocity. 0.70 ≦ x so that the crystallization speed is not too slow and recording can be performed at a practical recording linear velocity. Preferably 0.
It is assumed that 80 ≦ x. On the other hand, in order that the crystallization speed is not too high and recording can be performed at a practical recording linear velocity, x ≦ 0.95. Preferably, x ≦ 0.90.

The Ge amount is related to the storage stability of the amorphous mark. As the Ge amount increases, the storage stability of the amorphous mark tends to increase. If the Ge amount is too small, this effect becomes insufficient.
y. Preferably, 0.03 ≦ y. If the Ge amount is too large, the jitter of the reproduced signal deteriorates, so that y ≦ 0.10
And Preferably, y ≦ 0.08.

From the above, the recording layer set of the medium of the present invention
((Sb_xTe_1-x)_1-yGe_y) _1-zAu_zPlace
In this case, the values of x, y, and z are set to 0.70 ≦ x ≦ 0.95, 0.
It is assumed that 01 ≦ y ≦ 0.10 and 0.01 ≦ z ≦ 0.12.
In order to improve various characteristics, this recording layer
In, Ag, Ga, Zn, Sn, Si, Cu, Pd, P
t, Pb, Cr, Co, O, N, S, Se, V, Nb,
Ta or the like may be added. To get the effect of characteristic improvement
In addition, the addition amount is 0.1 at. %(atom
%) Or more is preferable. However, preferred characteristics of the composition of the present invention
10 at. %
Good.

The thickness of the recording layer is preferably in the range of 5 nm to 100 nm. If the thickness of the recording layer is less than 5 nm, it is difficult to obtain a sufficient contrast, and the crystallization speed tends to be slow. Further, it is more preferable to set the reflectivity to 10
nm or more. On the other hand, if the thickness of the recording layer exceeds 100 nm, it is still difficult to obtain optical contrast, and cracks are likely to occur.

In order to reduce the heat capacity and increase the recording sensitivity, the thickness is more preferably 50 nm or less. Furthermore, by setting the recording layer thickness to 50 nm or less, the volume change due to the phase change is reduced, and the recording layer itself and the upper and lower protective layers are
The effect of repeated volume changes due to repeated overwriting can be reduced. As a result, accumulation of microscopic and irreversible deformation is suppressed, noise is reduced, and repeated overwrite durability is improved.

In a medium for high-density recording such as a rewritable DVD, the requirement for noise is more severe, so that the thickness of the recording layer is more preferably 30 nm or less. Next, another part of the structure of the phase change optical disk will be described. A phase change optical disk often has a protective layer, a recording layer, a protective layer, and a reflective layer on a substrate in this order or in the reverse order.

As the substrate, a resin such as polycarbonate, polyacrylate, polyolefin, or glass can be used. When recording / reproducing light is incident from the substrate side, the substrate needs to be transparent to the recording / reproducing light. In many cases, the recording layer is covered with a protective layer on the upper and lower sides. As a material of the protective layer, a dielectric is often used, and is determined in consideration of a refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. Generally, oxides, sulfides, nitrides, and fluorides such as Ca, Mg, and Li of metals and semiconductors having high transparency and high melting point are used.

These oxides, sulfides, nitrides, and fluorides do not necessarily have to have a stoichiometric composition, and it is effective to control the composition for controlling the refractive index and the like, or to use a mixture thereof. It is. More specifically, a mixture of ZnS or a rare-earth sulfide and a heat-resistant compound such as an oxide, a nitride, and a carbide may be used. For example, a mixture of ZnS and SiO ₂ is often used for a protective layer of a phase change optical disk. The film density of these protective layers is preferably 80% or more of the bulk state from the viewpoint of mechanical strength.

The protective layer is usually provided with a thickness of 5 nm to 500 nm. When the thickness of the protective layer is less than 5 nm,
The effect of preventing the deformation of the recording layer is insufficient, and the recording layer tends not to function as a protective layer. If the thickness exceeds 500 nm, the internal stress of the dielectric itself constituting the protective layer and the difference in elastic properties between the dielectric layer and the contacting film become remarkable, and cracks are easily generated.

Generally, the material forming the protective layer has a low film forming rate and requires a long film forming time. In order to shorten the film formation time, shorten the manufacturing time, and reduce the cost, it is preferable to suppress the thickness of the protective layer to 200 nm or less. More preferably, it is 150 nm or less. The thickness of the protective layer provided between the recording layer and the reflective layer is preferably 5 nm or more to prevent deformation of the recording layer. In general, microscopic plastic deformation is accumulated inside the protective layer due to repeated overwriting, which eventually scatters reproduction light and increases noise. In order to suppress this, the thickness of the protective layer is preferably set to 60 nm or less.

On the other hand, the thickness of the protective layer provided between the recording layer and the substrate is preferably at least 20 nm in order to protect the substrate. The reflection layer is preferably made of a material having high reflectance and thermal conductivity. Examples of the material of the reflective layer having high reflectivity and thermal conductivity include metals mainly composed of Ag, Au, Al, Cu, and the like. Among them, Ag has the largest reflectance and thermal conductivity as compared with Au, Al, Cu and the like.

At shorter wavelengths, Au, Cu, A
l becomes easier to absorb light. For this reason, 65
When a short-wavelength laser of 0 nm or less is used, it is particularly preferable to use a metal containing Ag as a main component for the reflective layer. Further, Ag is preferable because it is relatively inexpensive as a sputtering target, has stable discharge, has a high film-forming speed, and is stable in air.

Ag, Al, Au, Cu and the like may contain other elements. When these impurities are mixed with the metal, the thermal conductivity and the reflectivity are reduced, but on the other hand, the stability and the film surface flatness may be improved. % Or less. The contained elements include Cr,
Mo, Mg, Zr, V, Ag, In, Ga, Zn, S
n, Si, Cu, Au, Al, Pd, Pt, Pb, T
One or more elements selected from the group consisting of a, Ni, Co, O, Se, V, Nb, Ti, O, and N are preferable.

The thickness of the reflective layer is preferably 50 nm or more and 200 nm or less. In order to obtain a sufficient reflectance and heat radiation effect, the thickness is preferably 50 nm or more. On the other hand, to reduce the film stress, the thickness is preferably 200 nm or less. Further, in order to shorten the film forming time, shorten the manufacturing time, and reduce the cost,
00 nm or less is preferable. In addition, the thickness of the recording layer and the protective layer, the above mechanical strength, in addition to the restrictions in terms of reliability,
In consideration of the interference effect associated with the multilayer structure, the laser beam is selected so that the absorption efficiency of the laser beam is good and the amplitude of the recording signal, that is, the contrast between the recorded state and the unrecorded state is large.

The recording layer, the protective layer, the reflective layer and the like are formed by a sputtering method or the like. It is desirable to form a film using an inline apparatus in which each sputtering target is installed in the same vacuum chamber, from the viewpoint of preventing oxidation and contamination between layers. It is also excellent in productivity. A protective coat layer made of an ultraviolet curable resin or the like may be provided on these layers for protection. Further, in order to increase the recording capacity, two or more recording layers may be provided on the substrate,
Alternatively, after each of the above layers is formed on the substrate, the layers may be bonded with an adhesive.

Next, a preferred recording method of the optical information recording medium of the present invention will be described. This recording method performs recording and / or erasing on the optical information recording medium described above with a reference clock cycle of 15 ns or less. According to this, the optical information recording medium has a high phase change speed and is excellent in the jitter characteristics of the reproduction signal. Therefore, the optical information recording medium is excellent in the reproduction signal jitter at a high linear velocity of 15 ns (nanosecond) or less in the reference clock cycle. The recorded data can be erased.

Usually, spiral or concentric recording tracks are formed on a disk-shaped medium, along which information is recorded. The recording layer is irradiated with a light beam (laser) spot emitted from the light irradiation unit while rotating the medium at high speed, and recording, reproduction, and erasing are performed while the light irradiation unit and the medium are relatively moved at high speed. Light emitted from the light source is usually applied to the medium through various optical systems, through an objective lens, and the like. To move the light irradiator relatively to the medium means, for example, irradiate a recording track of the medium from the lens while rotating the disk-shaped medium with the objective lens substantially fixed. When the recording track is formed in a spiral shape on the medium, the objective lens is shifted little by little in the radial direction of the disk while rotating the medium.

First, when forming the amorphous phase, it is preferable to alternately irradiate a high-power laser pulse and a low-power laser pulse. Hereinafter, a high-power laser pulse is referred to as a recording pulse, and the power applied at this time is referred to as a recording power Pw. A low-power laser pulse is referred to as an off pulse, and the power applied at this time is referred to as bias power Pb.

According to this, the region heated by the recording pulse can be relatively rapidly cooled during the off-pulse, and an amorphous phase is easily formed. In order to speed up the rise / fall of the pulse and to reduce the cost of the laser light source used for recording, it is preferable that recording can be performed with a small recording power Pw. Leads to deterioration. For this reason, the medium is preferably designed so that the recording power Pw is 8 to 25 mW. More preferably 8 to
20 mW.

The bias power Pb is equal to the recording power P
0.5 or less of w (Pb / Pw ≦ 0.5) is preferable,
It is more preferably 0.3 times or less (Pb / Pw ≦ 0.3). Here, in consideration of the tracking performance and the like, the bias power Pb is equal to the power P of the reproduction light irradiated at the time of reproduction.
A value close to the value of r is preferred. The reproduction power Pr is usually 0.
5 to 1.0 mW.

To increase the cooling rate, the bias power Pb is preferably reduced, and may be set to zero. That is, it is not necessary to irradiate light. During the formation of the crystal phase, it is preferable to continuously irradiate the recording layer with a laser beam having an erasing power Pe. The erasing power Pe is not particularly limited as long as the recording layer can be heated so that the crystal phase can be erased during overwriting, but is generally higher than the bias power Pb and lower than the recording power Pw. For example, 0.2 ≦ Pe / Pw <
1.0. The magnitude of the erasing power Pe is also related to the recrystallized region of the portion melted by the irradiation of the recording power Pw.

When the erasing power Pe is continuously applied, the recording layer is heated to a temperature near the crystallization temperature, and the heated region can be relatively gradually cooled to form a crystal phase. By combining the above, an amorphous phase and a crystalline phase can be formed and separated, and overwrite recording can be performed.

A specific example of alternately irradiating a recording pulse and an off pulse when forming an amorphous phase will be described below. When forming a mark (amorphous phase) having a length nT (T is a reference clock cycle and n is a natural number), the time nT is divided as in the following equation (1).

[0044]

Α ₁ T, β ₁ T, α ₂ T, β ₂ T,..., Α _m-1 T, β _m-1 T, α _m T, β _m T (1) ( Where α ₁ + β ₁ + α ₂ + β ₂ + ... α _m-1 + β _m-1 + α
_{m + β m = n-j} , j is 0 or a real number, m is an integer of 1 or more, j, m is a value determined by the combination of the medium and recording conditions. In the above formula, recording is performed by irradiating a recording pulse at a time of α _i T (1 ≦ i ≦ m) and irradiating an off-pulse at a time of β _i T (1 ≦ i ≦ m). Then, in a region (crystal phase) between the marks, light having an erasing power Pe is irradiated. Thus, overwrite recording can be performed.

[0045]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is limited to the examples unless it exceeds the scope of the gist.
It is not something to be done. Groove width 0.5 μm, groove depth 40 nm,
120 mm in diameter having a guide groove with a groove pitch of 1.6 μm,
On a 1.2 mm thick disk-shaped polycarbonate substrate,
(ZnS) ₈₀(SiO_Two)₂₀Layer (100 nm), Au-
Ge-Sb-Te recording layer (18 nm), (ZnS)
₈₀(SiO_Two)₂₀Layer (40 nm), Al_99.5Ta_0.5alloy
Reflective layer (200nm) formed by sputtering method
Then, a phase change optical disk was manufactured.

The composition of the recording layer was six kinds shown in Table 1.
did. Further, these compositions are represented by ((Sb _xTe_1-x)_1-yG
e_y)_1-zAu_zThe values of x, y, and z when expressed as
The results are shown in Table 1.

[0047]

[Table 1] First, initial crystallization was performed on each of the disks of Examples 1 and 2 and Comparative Examples 1 to 4. Next, Examples 1 and 2 and Comparative Example 1
Laser wavelength 780 nm,
Using a disk evaluation device having a pickup of NA 0.5, recording and erasing were performed in the guide grooves according to the following procedure, and then reproduction was performed to evaluate the disk characteristics.

First, a linear velocity of 24 m / s, a reference clock cycle T = 11.6 ns, Pw = 17 mW, Pe = 8.5 m
With W and Pb = 0.8 mW, an EFM random signal was overwritten 10 times using the laser waveform shown in FIG. In FIG. 1, the horizontal axis represents time, and the vertical axis represents laser power, and three types of power, ie, recording power Pw, erasing power Pe, and bias power Pb, are used. Figure 1
(A) shows a laser waveform when a mark having a length of 3T is recorded, and FIGS. 1 (b), (c), (d), (e),
(F), (g), (h), and (i) each have a length of 4T,
It shows the laser waveform when recording 5T, 6T, 7T, 8T, 9T, 10T, and 11T marks.

That is, when forming a mark (amorphous phase) having a length nT (T is a reference clock cycle and n is a natural number of 3 to 11), the period of time nT is calculated by the above equation (1).
Then, a recording pulse having the recording power Pw and an off-pulse having the bias power Pb are alternately irradiated, and the partial erasing power Pe is irradiated. An erasing light having an erasing power Pe was applied during the period for forming the inter-mark portion.

More specifically, when forming each mark, a pulse train of Pw and Pb was irradiated as follows (T is a reference clock cycle). 3T mark: 1.5T Pw, 1.2T Pb 4T mark: 1T Pw, 1T Pb, 1T Pw,
0.6T Pb 5T mark: 1T Pw, 1.35T Pb, 1.5T
Pw, 0.6T Pb 6T mark: 1T Pw, 1T Pb, 1T Pw, 1T
T Pb, 1T Pw, 0.6T Pb 7T mark: 1T Pw, 1T Pb, 1T Pw,
1.35T Pb, 1.5T Pw, 0.6T Pb 8T mark: 1T Pw, 1T Pb, 1T Pw, 1T Pw
T Pb, 1T Pw, 1T Pb, 1T Pw, 0.
6T Pb 9T mark: 1T Pw, 1T Pb, 1T Pw, 1T
T Pb, 1T Pw, 1.35T Pb, 1.5T Pw, 0.6T Pb 10T mark: 1T Pw, 1T Pb, 1T Pw,
1T Pb, 1T Pw, 1T Pb, 1T Pw, 1T
T Pb, 1T Pw, 0.6T Pb 11T mark: 1T Pw, 1T Pb, 1T Pw,
1T Pb, 1T Pw, 1T Pb, 1T Pw,
1.35T Pb, 1.5T Pw, 0.6T Pb The EFM random signal recorded as described above is reproduced at a linear velocity of 2.4 m / s, and 3T space jitter (jitter between 3T marks) is obtained. It was measured. The space between marks (space) corresponds to an unrecorded portion / erased portion, and the mark portion corresponds to a recorded portion. The 3T space refers to an inter-mark portion having a length of 3T, and the 3T space jitter is a jitter of a 3T-length inter-mark portion when a recorded EFM random signal is reproduced.

Next, under the same conditions except that Pe / Pw = 0.5 and Pw was changed between 18 and 24 mW,
Overwrite recording and measurement of 3T space jitter were repeated. FIG. 2 shows the results as a graph. FIG.
In the graph, the horizontal axis represents the recording power Pw (mW), and the vertical axis represents 3T space jitter (ns).

The discs of Comparative Examples 1 to 3 did not contain Au, but the disc showing the lowest jitter was the disc of Comparative Example 2, and the jitter bottom value (the lowest jitter when the recording power was changed) Value) was 20.8 ns.
Among the three types, Comparative Example 1 has the least amount of Sb and a large amount of Te, and Comparative Example 3 has the largest amount of Sb and a small amount of Te.
Comparative Example 2 is intermediate. Since the crystallization speed increases as the Sb content increases and the Te content decreases, the crystallization speed of the disk of Comparative Example 2 is between that of Comparative Example 1 and that of Comparative Example 3.

The disk of Comparative Example 1 having a relatively low crystallization speed had a jitter bottom value of 25.7 ns. The disc of Comparative Example 2 having a higher crystallization speed had a jitter bottom value of 2
Although it was improved to 0.8 ns, the disk of Comparative Example 3 having the highest crystallization speed had a jitter bottom value of 22.7 ns, which was rather worse. This indicates that it is difficult to obtain a better jitter by merely changing the crystallization speed by changing the content of Sb and Te.

In the discs of Comparative Examples 1 to 3, as the Sb content increased and the Te content decreased, the phenomenon that the line indicating the crystal reflectance level as observed with an oscilloscope became wider and wider became remarkable. . That is, the line indicating the reflectance level in Comparative Example 3 was thick. Probably, in Comparative Example 1, the crystallization speed was too slow, resulting in poor jitter. In Comparative Example 3, although the crystallization speed was increased, the influence of a new crystal phase, which adversely affected the jitter, became stronger, and jitter was deteriorated. .

On the other hand, in the discs of the first and second embodiments, Au
The better jitter was obtained as compared with the disks of Comparative Examples 1 to 3 which did not contain the same. The jitter bottom values of Examples 1 and 2 were 16.5 ns and 14.2 ns, respectively. That is, in the first and second embodiments, 17.5 ns or less (linear velocity of 2.4 m / s) defined by the CD-RW standard (Orange Book Part 3)
s) was obtained. Also, the phenomenon that the line indicating the crystal reflectivity level becomes thicker was reduced.

Next, EFM random signals were recorded once on the disks of Examples 1 and 2 and Comparative Examples 1 and 4 under the same conditions as described above. Thereafter, the recorded EFM random signal was reproduced at a linear velocity of 2.4 m / s, and 3T space jitter (jitter between 3T marks) was measured. In addition, 8
Keep in an environment of 0 ° C. and 85% RH for 500 hours (acceleration test,
Environment resistance test), the recorded EFM random signal is reproduced at a linear velocity of 2.4 m / s, and 3T space jitter (3T
The jitter between marks) was measured.

As a result, in the discs of Examples 1 and 2 and Comparative Example 1, there was no disappearance of the recording signal after the acceleration test, and the jitter bottom value change was 0 ns in Example 1 and 6 ns in Example 2.
In Comparative Example 1, it was 0 ns. On the other hand, in Comparative Example 4, the recording mark almost completely crystallized and disappeared, and measurement was impossible. Further, an InSbTe-based recording layer conventionally used as a recording material for an optical disk was evaluated. The S of the recording layer is adjusted so that the composition has a high crystallization rate suitable for high linear velocity recording of the linear velocity of 24 m / s.
By adjusting the b / Te content ratio, In ₆ Sb ₇₈ Te ₁₇ , In ₈
Optical discs having three types of recording layers, Sb ₇₆ Te ₁₆ and In ₁₀ Sb ₇₄ Te ₁₆ , were produced. An EFM random signal was recorded once on these disks under the same conditions as described above. Subsequently, when the temperature was maintained at 80 ° C. and 85% RH for 500 hours, the amorphous mark was crystallized and the mark disappeared.
This phenomenon was not related to the amount of In. When the amount of In was increased, the phenomenon that the line indicating the crystal reflectance level became thick became remarkable, and the jitter was deteriorated.

[0058]

By using the optical information recording medium of the present invention, a high crystallization speed, an excellent recording signal jitter characteristic, and an excellent storage stability can be achieved so as to be able to cope with recording at a reference clock cycle of 15 ns or less. An optical information recording medium having a property can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a pulse division method in the present embodiment.

FIG. 2 is a graph showing a relationship between recording power and 3T space jitter in the present embodiment.

Claims (4)

[Claims] 1. An optical information recording medium having at least a phase change type recording layer provided on a substrate, wherein the phase change type recording layer is ((Sb _x Te _1-x ) _1-y Ge _y ) _{1 -z} Au _z (where 0.
70 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.10, 0.0
An optical information recording medium comprising an alloy having a composition represented by 1 ≦ z ≦ 0.12) as a main component. 2. The optical information recording medium according to claim 1, wherein 0.03 ≦ z. 3. The optical information recording medium according to claim 1, wherein z ≦ 0.10. 4. A recording and erasing method, characterized in that recording is performed on an optical information recording medium according to claim 1, wherein a reference clock cycle at the time of recording is 15 ns or less.