JP2002269809A - Information recording medium, initializing method for information recording medium and recording method for information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct-read-after-write type disk capable of being easily initialized and stably forming an unalterable amorphous mark for a long period, the initializing method and the recording method. SOLUTION: A recording layer and a recording mark stabilizing layer in contact with the recording layer are provided on a substrate, a recording mark is formed by supplying energy and a part or all of the recording mark stabilizing layer in a recording mark area is diffused in the recording layer. Before forming the recording mark, the initializing process of crystallizing the recording layer by supplying the energy is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium on which digital information such as video, audio and computer data can be recorded by a recording beam such as a laser beam or an electron beam, a method of manufacturing the medium, and an information recording medium. The present invention relates to a recording / reproducing method and an information recording / reproducing device.

[0002]

2. Description of the Related Art Hitherto, various information recording media have been proposed in which a thin film (recording layer) made of a heat mode recording material is carried on a substrate and information can be recorded by the photothermal action of the recording layer. Among these, a write-once recording medium on which information can be recorded only once cannot be tampered with, and is therefore attracting attention as a long-term storage file.

A large number of inventions relating to this type of recording have been filed, and Japanese Patent Publication No. Sho.
No. 996 has a technology to record information by forming holes.
Japanese Patent Application Laid-Open Nos. 57-22095 and 60-28045 disclose techniques for recording information by solid phase diffusion and alloying, and Japanese Patent Nos. 2138564 and 2135363 describe so-called write-once media using dyes. A technique relating to CD-R is disclosed.

[0004] Further, among those which perform recording by changing the atomic arrangement (so-called phase change), there are those which require the initial crystallization of the front surface of the disk. Techniques for forming a crystal nucleus forming layer in order to omit this initialization step or to speed up the initialization step are disclosed in JP-A-10-226173 and JP-A-11-96594.

[0005]

Among the above-mentioned techniques, the method of performing recording by forming a hole involves physical deformation due to physical movement of the recording film, and thus the recording film is protected from oxidation by protecting the recording film from oxidation. There is a problem that the protective film cannot be formed in close contact. Further, there is a problem that it is difficult to control the surface tension of the melted recording film, and it is difficult to control a minute mark shape.

In the technique based on solid-phase diffusion and alloying, the protective film can be formed in close contact with the recording film because the recording film atoms move only without physical deformation. There is a problem that the diffusion progresses gradually in a severe environment and the storage life is insufficient. CD-
R has a problem that characteristics such as reflectance and recording sensitivity greatly depend on the recording laser wavelength.

On the other hand, a method in which an amorphous mark is formed after the entire surface of a recording film is first crystallized is considered to be able to avoid the above problem. In fact, the rewritable medium is a method used for products such as CD-RW and DVD-RAM. However, when this method is applied to a write-once medium in which it is difficult to tamper with recorded information, it is possible to easily crystallize in the initialization process, and the amorphous mark once recorded is not easily crystallized. The problem was that it was very difficult to satisfy the characteristics. As described above, Japanese Patent Application Laid-Open No. 11-96594 discloses a technology relating to a write-once medium having a crystallization promoting layer formed thereon. According to this method, the recording layer is crystallized by the crystallization accelerating layer. Therefore, even if a recording layer having a low crystallization speed is used, initialization is not required or can be easily performed, and the amorphous mark is crystallized. It is thought that a difficult medium can be provided. However, the storage stability of the amorphous mark under a severe storage environment, particularly the influence of the crystallization promoting layer on the crystallization of the amorphous mark has not been sufficiently considered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a large-capacity and highly reliable write-once disc capable of easily performing initialization and forming a non-tamperable amorphous mark, and its initialization. It is to provide a method and a recording method.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted various studies in order to achieve the above object. As a result, a recording layer is provided on a substrate, and a recording mark stabilizing layer is provided in contact with the recording layer. It has been found that the above problem can be solved quickly by forming a recording mark by applying energy and diffusing a part or all of the recording mark stabilizing layer in the recording mark area into the recording layer.

At this time, before forming a recording mark, an initialization process for crystallizing the recording layer by applying energy is performed.

The recording layer contains Ge, Sb and Te,
In addition, a material whose content ratio [Sb / Te] in atomic% of Sb and Te satisfies 0.01 ≦ [Sb / Te] ≦ 1 can be used.
It preferably contains b, Te or Ag. The recording mark stabilizing layer is made of Sc, Ti, V, Cr, Mn, F
e, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo,
Tc, Ru, Rh, Pd, Cd, Hf, Ta, W, R
e, Os, Ir, Pt, Au, B, C, N, O, Al,
Si, P, Ar, Ga, As, Se, In, Sn, T
1, Pb and Bi may be included.

Further, the recording layer contains Sb and Te,
And the content ratio [Sb / Te] of Sb and Te in atomic% is 1
<A material satisfying [[Sb / Te] ≦ 10] can be used. At this time, the recording mark stabilizing layer preferably contains at least Te. Sc, Ti, V, Cr, M
n, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb,
Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, T
a, W, Re, Os, Ir, Pt, Au, B, C, N,
O, Al, Si, P, Ar, Ga, As, Se, In,
Ge, Sn, Tl, Pb, and Bi may be included.

In the initialization process, it is preferable that part or all of the recording mark stabilizing layer is diffused into the recording film.

After the initialization, a part or all of the recording mark stabilizing layer may be diffused into the recording film by annealing the medium, or after the initialization,
By irradiating the medium with light, part or all of the recording mark stabilizing layer may be diffused into the recording film.

It is preferable that the energy intensity per unit time and unit area applied during initialization is smaller than the energy intensity per unit time and unit area applied during recording.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A recording layer containing Ge, Sb and Te has a high crystallization speed on a line connecting GeTe and Sb ₂ Te ₃ and can be easily crystallized. However, at the same time, crystallization of the amorphous recording mark, that is, erasing, is also easily performed. Although this feature is advantageous in a rewritable medium, it is disadvantageous in a rewritable write-once medium.

On the other hand, a film having a composition containing at least one of Ge, Sb, and Te in excess of the composition on the line connecting GeTe and Sb ₂ Te ₃ has a low crystallization rate. In addition, the composition on the line connecting GeTe and Sb ₂ Te ₃ is represented by Sc, Ti, V, Cr, Mn, Fe, C
o, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc,
Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R
e, Os, Ir, Pt, Au, B, C, N, O, Al,
Si, P, Ar, Ga, As, Se, In, Sn, S
Addition of at least one of e, Tl, Pb, and Bi also reduces the crystallization speed.

Similarly, the recording layer containing Sb and Te is:
Even in a region where the content ratio [Sb / Te] of Sb and Te in atomic% is larger than 1, the crystallization speed is high and [Sb / Te]
Although the crystallization rate tends to increase as Te increases, other elements such as Sc, Ti, V, Cr, and M
n, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb,
Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, T
a, W, Re, Os, Ir, Pt, Au, B, C, N,
O, Al, Si, P, Ar, Ga, As, Se, In,
The addition of Ge, Sn, Tl, Pb, and Bi slows down the crystallization speed.

Therefore, GeTe and Sb are used as recording layers.
_When a material having a composition on the line connecting 2Te ₃ or a material having a high crystallization rate such that [Sb / Te] is 1 or more is used, it should be added to the recording layer as a recording mark stabilizing layer. If a material that slows down the crystallization of the recording layer is used and part or all of the recording mark stabilizing layer is diffused into the recording layer in the recording mark area, initialization can be performed easily, and data It is possible to obtain a medium that is difficult to falsify. The reason that data falsification becomes difficult is that the composition of the recording layer changes from a high crystallization rate to a low crystallization rate due to diffusion of the recording mark stabilizing layer, and crystallization is not easily performed.

The preferred composition for the Ge—Sb—Te recording layer is near the line connecting GeTe and Sb ₂ Te ₃ . Specifically, Ge, Sb, when expressed by the general formula content ratio of the respective elements of _{Te (Ge 1-x Te x} ) 1-z (Sb 1-y Te y) z, 0.40 ≦ x ≦ 0.60, 0.50 ≦
The range where y ≦ 0.70 and 0 ≦ z ≦ 1 is preferable.
42 ≦ x ≦ 0.58, 0.52 ≦ y ≦ 0.68, 0 ≦ z
≦ 0.95 is more preferable, and 0.45 ≦ x ≦
The most preferable ranges are 0.55, 0.55 ≦ y ≦ 0.65, and 0 ≦ z ≦ 0.9.

Further, the recording layer is Ge, Sb, may contain an element other than Te, formula when other elements expressed in _{M {(Ge 1-x Te} x) 1-z (Sb 1-y Te _y ) _z } _{1-a In} MA _a , 0.42 ≦ x ≦ 0.58, 0.52 ≦ y ≦
0.68, 0 ≦ z ≦ 1, and 0 <a ≦ 0.15 are preferable, and 0.45 ≦ x ≦ 0.55, 0.55 ≦ y ≦
The ranges where 0.65, 0 ≦ z ≦ 0.95, and 0 <a ≦ 0.1 are more preferable. MA is Sc, Ti, V, Cr, M
n, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb,
Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, T
a, W, Re, Os, Ir, Pt, Au, B, C, N,
O, Al, Si, P, Ar, Ga, As, Se, In,
Sn, Tl, Pb and Bi are preferred. Of these, T
i, Cr, Co, Nb, Mo, Pd, Ta, W, Pt,
Au is preferable in that it has excellent corrosion resistance. O, N, A
r is preferable because it has an effect of preventing the amorphous mark shape from being distorted due to crystal growth from the interface with the crystal part.
Ag is preferable in that the refractive index difference between the crystal and the amorphous becomes large. Sn is preferable in that the crystallization rate can be easily controlled. Sn may be added as MA, but may be added not as MA but in the form of substituting for Ge. In this case, there is an effect that the crystallization speed is increased. In, Zn, Cu, and Se are preferable because they have an effect of preventing oxidation of the recording layer itself by oxidizing itself. Further, when a plurality of elements are added, the effects of the respective elements can be obtained.

The preferred composition for the Sb-Te based recording layer is that the content ratio [Sb / Te] of Sb and Te in atomic% is 1%.
It is in the larger area. Specifically, 1 <
Those satisfying [Sb / Te] ≦ 10 are preferable. Further, the recording layer may contain an element other than Sb and Te. Other elements include Sc, Ti, V, Cr, Mn, Fe, C
o, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc,
Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, R
e, Os, Ir, Pt, Au, B, C, N, O, Al,
Si, P, Ar, Ga, As, Se, In, Ge, S
n, Tl, Pb and Bi are preferred. Of these, Ge
Is preferred from the viewpoint of increasing the crystallization temperature. In is preferable in that the difference in the refractive index between the crystal and the amorphous becomes large. Au and Ag have the effect of increasing the reflectance.
Ti, Cr, Co, Nb, Mo, Pd, Ta, W, Pt
Is preferred in that it has excellent corrosion resistance. O, N, Ar
Is preferable because it has an effect of preventing the amorphous mark shape from being distorted due to crystal growth from the interface with the crystal part.

Of course, the recording layer is not limited to Ge-Sb-Te-based materials or Sb-Te-based materials. Other materials include, for example, Ge—Te, In—Sb, and In—
Se system, In-Se-Tl system, Sb-Se-Bi system, S
An n-Sb-Te system, a Ge-Sn-Sb-Te system, or the like can be used.

Since the recording mark is formed by melting the recording layer and then quenching it, if the temperature of the recording mark stabilizing layer is heated to near or above the melting point during recording, diffusion easily occurs. Therefore, the melting point of the recording mark stabilizing layer is preferably lower than or higher than the melting point of the recording layer. When the melting point of the recording mark stabilizing layer is higher than the melting point of the recording layer, the difference is preferably 150 ° C. or less, more preferably 100 ° C. or less.

As described above, the recording mark stabilizing layer is
Diffusion into the recording film reduces the crystallization speed of the recording film, and has a role of stably retaining the recording marks. At the same time, when the recording film is initialized, it can have a role of promoting crystallization of the recording film. Specifically, if the recording film has a role of generating a crystal nucleus required for crystal growth, the recording film can be easily crystallized. In order to become a crystal nucleus, the recording mark stabilizing layer itself is required to be stable. It may itself be crystalline or amorphous. If the recording film has a lattice constant close to the lattice constant of the crystal, the nucleus is likely to be a crystal nucleus, but may be amorphous. As amorphous, at least one of the elements constituting the recording film, nitride, oxide,
It preferably contains sulfide, fluoride, carbide and the like.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. 1, 2 and 3 are sectional views of the present embodiment, and FIGS. 4 and 5 are waveforms used for recording.

(Example 1) Diameter 120 mm, thickness 0.6
0.6μm width on the surface of polycarbonate resin plate
The substrate 1 in which grooves of m and a depth of 60 nm were formed at a pitch of 1.23 μm was produced by injection molding. Pre-pits for recording disc recognition information, address information and the like in advance are formed on this substrate. Also, both grooves and between the grooves are used as tracks for recording information. The substrate 1 was placed in a first sputtering chamber in a sputtering apparatus having a plurality of sputtering chambers and having excellent film thickness uniformity and reproducibility. Using a mixture of ZnS and SiO ₂ as a target, a (ZnS) ₈₀ (S
iO ₂ ) ₂₀ (mol%) First dielectric layer 2 was formed. Next, after moving this substrate to the second sputtering chamber, a Sb ₇₀ Te ₃₀ (atomic%) sintered body was used as a target to form a 5 nm thick Sb ₇₀ Te ₃₀ recording mark stabilizing layer 3 in argon gas. did. Subsequently, in the third sputtering chamber, Ge ₂₂ S
b ₂₅ using Te ₅₃ (atomic%) sintered target, the recording layer 4 was 25nm formed in argon gas. Then the fourth
The substrate was moved to the sputtering chamber, and a (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) second dielectric layer 5 having a thickness of 16 nm was formed in the same manner as in the formation of the first dielectric layer. Finally, an AlTi reflective layer 6 having a thickness of 70 nm was formed in the fifth sputtering chamber using Al _95.5 Ti _0.5 (atomic%) as a target. The laminated substrate was taken out of the sputtering apparatus, and an ultraviolet curable resin protective layer 7 was formed on the uppermost layer by spin coating.

Similarly, on another similar substrate 1 ′, (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) first dielectric layer 2 ′, recording mark stabilizing layer 3 ′, recording layer 4 ′ , (ZnS)
₈₀ (SiO ₂ ) ₂₀ (mol%) Second dielectric pair layer 5 ′, AlTi
A reflective layer 6 'and an ultraviolet-curable resin protective layer 7' were formed, and the two substrates were bonded together with an adhesive layer 8 with the ultraviolet-curable resin protective layers 7, 7 'inside. At this time, if the diameter of the adhesive layer was set to 118 mm or more, peeling of the adhesive layer due to impact such as dropping became difficult to occur. FIG. 1 shows the cross-sectional structure.

The disk manufactured as described above was set to a wavelength of 8
Initialization was performed by irradiating a laser beam having an elliptical beam having a diameter of 10 nm, a major axis of 50 μm, and a minor axis of 1 μm. The initialized disk was rotated so as to have a linear velocity of 17 m / s, and a semiconductor laser beam having a wavelength of 660 nm was condensed by an objective lens having a numerical aperture of 0.6, and reproduction was performed to examine the reflectance variation ΔR. . The reflectance variation ΔR is defined as ΔR = (Rmax−Rmin) / {(Rmax + Rmi), where Rmax is the maximum value of reflectance and Rmin is the minimum value in one round of the disk.
n) / 2}.

When the linear velocity and the power of the disk were changed in the initialization process, ΔR was as shown in Table 1 below. In the table, ○ indicates ΔR ≦ 5%, and X indicates ΔR> 5%.

[0031]

[Table 1]

After initializing the disk at a linear velocity of 8 m / s and a power of 700 mW, the disk was rotated to a linear velocity of about 17 m / s, and a semiconductor laser beam having a wavelength of
And focused on the recording layer through the substrate to perform recording and reproduction. At this time, tracking was performed on the groove. The recording frequency was set to 4.8 MHz, recording was performed while changing the recording power, and the C / N was measured. A good C / N of 50 dB or more was obtained at a recording power of 12 mW or more. In addition, the carrier level (C
Level), that is, the erasure ratio was 10 dB or less, indicating that a recording mark that was difficult to alter data was formed.

After recording, the disc was heated to 90 ° C. and 80%
The sample was allowed to stand for 250 hours in the above environment, and the decrease in C level was measured. The decrease was 1 dB or less.

In the above, a disk having no recording mark stabilizing layer was manufactured, and a similar experiment was performed. At this time, the combination of good initialization conditions was the same as in Table 1. However, it was found that the C level was reduced by 25 dB or more by continuous light irradiation, and that the disc was highly likely to be falsified relatively easily. Was. Further, when a disk was prepared in which Sb was added to the recording layer at 10% without providing the recording mark stabilizing layer, the decrease in C level was 10 dB or less, but almost no combination of good initialization conditions was obtained.

In this embodiment, the recording mark stabilizing layer is provided on the side of the recording layer closer to the substrate, but similar results can be obtained by providing the layer further from the substrate.

Although the above results were performed on the grooves, similar results were obtained when recording was performed with tracking between the grooves.

The composition of the vicinity line connecting GeTe and Sb ₂ Te ₃ as a recording film, i.e. Ge, Sb, formula content ratio of the respective elements of _{Te (Ge 1-x Te x} ) 1-z (Sb 1 _−y Te _y ) When expressed as _z , 0.40 ≦ x ≦ 0.60, 0.50 ≦
Similar results were obtained when using those in the range of y ≦ 0.70 and 0 ≦ z ≦ 1. 0.42 ≦ x ≦ 0.5
8, 0.52 ≦ y ≦ 0.68, 0 ≦ z ≦ 0.95, the combination of good initialization conditions in which ΔR shows a small value is slightly increased, and 0.45 ≦ x ≦ 0 .5
5, 0.55 ≦ y ≦ 0.65, 0 ≦ z ≦ 0.9, the number of combinations of good initialization conditions increased. Further, Ge as a recording film, Sb, those containing an element M other than Te, i.e. _{{(Ge 1-x Te x} ) 1-z (Sb 1-y Te y) z} in _1-a M a, 0 .42 ≦ x ≦ 0.58, 0.52 ≦ y ≦
Similar results were obtained when using those in the range of 0.68, 0 ≦ z ≦ 1, and 0 <a ≦ 0.15. 0.45 ≦ x ≦
0.55, 0.55 ≦ y ≦ 0.65, 0 ≦ z ≦ 0.9
When the range where 5, 0 <a ≦ 0.1 is used, the combination of favorable initialization conditions is slightly increased. Note that M is Sc, Ti, V, Cr, Mn, Fe, Co, Ni, C
u, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh,
Pd, Ag, Cd, Hf, Ta, W, Re, Os, I
r, Pt, Au, B, C, N, O, Al, Si, P, A
r, Ga, As, Se, In, Sn, Tl, Pb, Bi
Can be used.

As a recording mark stabilizing layer, Sb ₇₀ Te ₃₀
Instead, Sb _α Te _{1- α (except} 0 ≦ α ≦ 1) very similar characteristics were obtained with. At this time, α ≧ 0.75
In this area, the diffusion was liable to occur, the overwrite jitter deteriorated, and the data was more difficult to be falsified. In addition, as a recording mark stabilizing layer, Sb ₇₀ Te
Ge can also be added to ₃₀ . However, in this case, when the content of Ge was 50% or more, the melting point of the stabilizing layer was increased and diffusion to the recording layer became difficult. Therefore, the content of Ge is preferably 50% or less, and 30% or less.
% Is more preferable. Sc, T instead of Ge
i, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,
Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, A
g, Cd, Hf, Ta, W, Re, Os, Ir, Pt,
Au, B, C, N, O, Al, Si, P, Ar, Ga,
Similar characteristics were obtained by adding at least one element of As, Se, In, Sn, Tl, Pb, and Bi. Further, as a recording mark stabilizing layer, Te, Sb, Zn, C
d, Al, In, Sn, Se, Tl, Pb, Bi, Ag
Or an alloy comprising two or more of these elements,
Further, Sc, Ti, V, Cr, Mn, Fe, Co, N
i, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh,
Pd, Hf, Ta, W, Re, Os, Ir, Pt, A
u, B, C, N, O, Si, P, Ar, Ga, As, G
Similar characteristics were obtained by using a material to which e was added in an amount of 30% or less.

Example 2 120 mm in diameter and 0.6 in thickness
0.3μm width on the surface of polycarbonate resin plate
The substrate 10 in which grooves of m and a depth of 30 nm were formed at a pitch of 0.74 μm was produced by injection molding. Pre-pits for recording disc recognition information, address information and the like in advance are formed on this substrate. Either a groove or a space between grooves is used as a track for recording information. This substrate 10 was disposed in a first sputtering chamber in a sputtering apparatus having a plurality of sputtering chambers and having excellent film thickness uniformity and reproducibility, as in Example 1. Using Ag as a target, an Ag recording mark stabilizing layer 12 having a thickness of 2 nm was formed in an argon gas. Next, this substrate is
After moving to the sputtering chamber, Ag ₅ I
n ₁₀ Sb ₅₀ Te ₃₅ (atomic%) as a sintered body, nitrogen 0.2
A 15 nm recording layer 13 was formed in an argon-nitrogen mixed gas containing mol%. The time from the completion of the formation of Ag to the formation of the recording layer was 60 seconds, during which the substrate was
It was kept under a vacuum of × 10 ⁻³ Pa. Next, the substrate was moved to a third sputtering chamber, and ZnS and SiO _{2 were used} as targets.
Using a mixture of (Z) having a thickness of 30 nm in argon gas.
(nS) ₈₀ (SiO ₂ ) ₂₀ (mol%) The dielectric layer 14 was formed. Finally, in the fourth sputtering chamber, Al _95.5 Ti
_{Using 0.5} (atomic%) as a target, an AlTi reflective layer 15 was formed to a thickness of 150 nm. The laminated substrate is taken out of the sputtering apparatus, and the surface of the AlTi reflection layer and the substrate 1 are removed.
The dummy substrate 16 having the same diameter and thickness as that of the above was bonded with an adhesive layer made of an ultraviolet curable resin 17. FIG. 2 shows the cross-sectional structure.

The disk manufactured as described above was used with a wavelength of 8
Initialization was performed by irradiating a laser beam having an elliptical beam having a diameter of 10 nm, a major axis of 50 μm, and a minor axis of 1 μm. The reflectance variation ΔR was examined in the same manner as in Example 1. When the disk linear velocity and power were changed during the initialization process, ΔR
Was as shown in Table 2 below. In the table, ○ indicates ΔR ≦ 5.
% And X indicate ΔR> 5%.

[0041]

[Table 2]

After initializing the disk at a linear velocity of 7 m / s and a power of 700 mW, the disk was rotated to a linear velocity of about 14 m / s, and a semiconductor laser beam having a wavelength of
And focused on the recording layer through the substrate to perform recording and reproduction. At this time, tracking was performed on the groove. The window width Tw is 10 ns, and 8
A -16 modulated random signal was recorded with a waveform as shown in FIG. 4, and the jitter was measured.
A good jitter of 8% or less was obtained at mW or more. Subsequently, overwriting of a random signal was performed at the same location using an overwriting waveform as shown in FIG. At this time, the erasing power was １ ／ of the recording power. At any power, the overwrite jitter was 20% or more, indicating that overwriting, that is, data falsification, was difficult.

After recording, the disk was heated at 90 ° C. and 80%
The sample was left for 250 hours in the above environment, and the amount of increase in jitter was measured. As a result, the amount of increase was 0.5% or less.

In the above, a disk having no recording mark stabilizing layer was manufactured, and a similar experiment was performed. At this time, the combination of good initialization conditions was the same as in Table 2, but the overwrite jitter was as good as 8% or less.
It turned out that the disc has a high possibility that data falsification can be performed relatively easily. In addition, when a disk was prepared in which Te was added to the recording layer without providing the recording mark stabilizing layer, the overwrite jitter was 20% or more, but almost no combination of good initialization conditions was obtained.

In this embodiment, the recording mark stabilizing layer is provided on the side of the recording layer closer to the substrate, but similar results can be obtained by providing the layer further from the substrate.

Although the above results were performed on the grooves, similar results were obtained when recording was performed with tracking between the grooves.

Similar characteristics were obtained even when the content ratio [Sb / Te] of the recording film in atomic% [Sb / Te] was set to more than 1 and 10 or less. When [Sb / Te] is 1.8 or more, initialization is easier, and when it is 1.8 or less, the amount of increase in jitter under an accelerated environment is small. Further, a part or all of Ag and In is Sc, Ti, V, Cr,
Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, N
b, Mo, Tc, Ru, Rh, Pd, Cd, Hf, T
a, W, Re, Os, Ir, Pt, Au, B, C, N,
O, Al, Si, P, Ar, Ga, As, Se, Sn,
Similar characteristics were obtained even when at least one of Tl, Pb, Bi, and Ge was substituted.

When Ag is used as the recording mark stabilizing layer, it has the effect of promoting crystal growth. Therefore [S
Even if [b / Te] was reduced to 1.8 or less, the initialization could be easily performed.

Similar characteristics were obtained by using Sb _α Te _{1- α} (0.5 ≦ α ≦ 1) instead of Ag as the recording mark stabilizing layer. At this time, in the region of α ≧ 0.75, diffusion is likely to occur, and the overwrite jitter is deteriorated, so that data falsification becomes more difficult. Further, as a recording mark stabilizing layer, Sb _α Te _{1- α}
, Ag, In, and Ge may be added. In the case where these are added, if their content is 50% or more, the melting point of the stabilizing layer becomes high and diffusion to the recording layer becomes difficult to occur. Therefore, the content of Ag, In, and Ge is preferably 50% or less, and more preferably 30% or less. Sc, Ti, V, instead of Ag, In, Ge
Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Z
r, Nb, Mo, Tc, Ru, Rh, Pd, Cd, H
f, Ta, W, Re, Os, Ir, Pt, Au, B,
C, N, O, Al, Si, P, Ar, Ga, As, S
Similar characteristics were obtained by adding at least one element of e, Sn, Tl, Pb, and Bi. Further, as a recording mark stabilizing layer, Te, Sb, Zn, Cd, Al, I
n, Sn, Se, Tl, Pb, Bi, Ag or an alloy composed of two or more of these elements;
c, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, H
f, Ta, W, Re, Os, Ir, Pt, Au, B,
30 for C, N, O, Si, P, Ar, Ga, As, Ge
%, Similar characteristics were obtained.

(Embodiment 3) Diameter 120 mm, thickness 1.1
0.15μ width on the surface of polycarbonate resin plate
A substrate 18 having grooves m and a depth of 35 nm formed at a pitch of 0.3 μm was produced by injection molding. Pre-pits for recording disc recognition information, address information and the like in advance are formed on this substrate. Either a groove or a space between grooves is used as a track for recording information. This substrate 18 was disposed in a first sputtering chamber in a sputtering apparatus having a plurality of sputtering chambers and having excellent film thickness uniformity and reproducibility. Al _95.5 Ti _0.5 as target
(Atomic%) in argon gas with a thickness of 70 nm
An lTi reflection layer 19 was formed. Next, after moving this substrate to the second sputtering chamber, ZnS and S
Using a mixture of TiO ₂ and a thickness of 20 nm in argon gas
(ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) of the first dielectric layer 20 was formed. Subsequently, in the third sputtering chamber, Ge ₃₃ S
The recording layer 21 was formed to a thickness of 20 nm in an argon gas using a b ₁₃ Te ₅₄ (atomic%) sintered body target. Next, the substrate was moved to the fourth sputtering chamber, and Sb ₇₀ Te ₃₀ (atomic%) was used.
Sb ₇₀ Te in argon gas using a sintered target
_{30 A} recording mark stabilizing layer 22 is formed to a thickness of 2 nm.
40 nm thick (ZnS) in the same manner as the formation of the dielectric layer
_{An 80} (SiO ₂ ) ₂₀ (mol%) second dielectric layer 23 was formed. The laminated substrate was taken out of the sputtering apparatus, and the uppermost layer was coated with a UV-curable resin adhesive 24 to a thickness of 0.1 mm.
mm of the cover layer 25 was bonded together.

The disk manufactured as described above was initialized by using the same initialization apparatus as in the first embodiment. However, at this time, the laser light was applied from the 0.1 mm cover layer side. In addition, the initialized disk is rotated so as to have a linear velocity of 15 m / s, and a semiconductor laser beam having a wavelength of 405 nm is condensed by an objective lens having a numerical aperture of 0.85 to perform reproduction. Examined. When the disk linear velocity and the power were changed in the initialization process, ΔR was as shown in Table 3 below. In the table, ○ indicates ΔR ≦ 5%, and X indicates ΔR> 5.
% Is shown.

[0052]

[Table 3]

After initializing the disk at a linear velocity of 7 m / s and a power of 700 mW, the disk was rotated so as to have a linear velocity of about 10 m / s, and a semiconductor laser beam having a wavelength of 405 nm was irradiated with an NA of 0.8.
The light was condensed by the objective lens No. 5 and irradiated onto the recording layer through the substrate to perform recording and reproduction. At this time, tracking was performed on the groove. The recording frequency was set to 25 MHz, recording was performed while changing the recording power, and the C / N was measured. A good C / N of 45 dB or more was obtained at a recording power of 4 mW or more. Further, the decrease in the carrier level (C level) due to continuous light irradiation, that is, the erasing ratio is 10 dB or less,
It was found that a recording mark that was difficult to falsify was formed.

After recording, the disk was heated at 90 ° C. and 80%
The sample was allowed to stand for 250 hours in the above environment, and the decrease in C level was measured. The decrease was 1 dB or less.

In the above, a disk having no recording mark stabilizing layer was manufactured, and a similar experiment was performed. At this time, the combination of good initialization conditions was the same as in Table 3, but it was found that the C level was reduced by 25 dB or more by continuous light irradiation, and that the disc was highly likely to be falsified relatively easily. Was. In addition, when a disk was prepared in which 10% of Sb was added to the recording layer without providing the recording mark stabilizing layer, the decrease in the C level was 10 dB or less, but almost no combination of good initialization conditions was found.

In this embodiment, the recording mark stabilizing layer is provided on the side of the recording layer far from the substrate of 1.1 mm. However, similar results can be obtained by providing the layer near the substrate.

Although the above results were performed on the grooves, similar results were obtained when recording was performed with tracking between the grooves.

In this embodiment, Al _95.5 Ti is used as the reflection layer.
_{Although 0.5} (atomic%) was used, Al-Ti alloys of other compositions and other Al alloys such as Al-Cr, Al-Ta, and Al
-Nb, Al-Mg, Al-Si, Al-Ge, or the like can also be used. Further, Ag or Ag alloy, Au
Alternatively, an Au alloy, Cu, or a Cu alloy can be used. Further, those containing Si, Ge, and Sb as main components can also be used. These reflective layers may be used in a multilayered form.

In this embodiment, a substrate using either a groove or a space between grooves is used as a recording track. However, the same applies to a so-called land / groove recording substrate which performs recording in both grooves. The result was obtained. At this time, the substrate has a groove pitch of 0.6 μm or less and a groove width of 0.3 μm.
The following can be used:

[0060]

According to the present invention, a large-capacity and high-reliability write-once disc capable of easily initializing and forming a non-tamperable amorphous mark, and the same. An initialization method could be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a cross-sectional structure of an information recording medium according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a cross-sectional structure of an information recording medium according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a cross-sectional structure of an information recording medium according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a recording waveform used for recording on an information recording medium according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a recording waveform used for overwrite recording on an information recording medium according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 1 ', 10, 18 Substrate 2, 2', 20 First dielectric layer 3, 3 ', 12, 22 Recording mark stabilizing layer 4, 4', 13, 21 Recording layer 5, 5 ', 14, 23 Second dielectric layer 6, 6 ', 15, 19 Reflective layer 7, 7' UV curable resin protective layer 8, 17, 24 Adhesive layer 9 Laser beam 16 Dummy substrate 25 Cover layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/30 B41M 5/26 X (72) Inventor Kazuyo Umezawa 1-88 Ushitora 1-chome, Ushitora, Ibaraki-shi, Osaka No. Hitachi Maxell Co., Ltd. (72) Inventor Makoto Iimura 1-88 Ushitora, Ibaraki-shi, Osaka F-term (reference) 2H111 EA03 EA12 EA23 EA31 FA11 FA12 FA14 FA21 FA23 FA37 FB05 FB09 FB12 FB30 GA11 5D029 HA06 HA07 JA01 JB03 JB05 JC17 5D090 AA01 BB05 BB12 CC11 DD01 KK03 5D121 AA01 EE03 EE27

Claims (13)

[Claims] 1. An information recording medium in which a recording layer is provided on a substrate and a recording mark is formed by applying energy, a recording mark stabilizing layer is provided in contact with the recording layer to stabilize the recording mark in the recording mark portion. An information recording medium, wherein part or all of a layer is diffused in a recording layer. 2. The information recording medium according to claim 1, wherein recording is performed after performing an initialization step of crystallizing the recording layer by applying energy. 3. The information recording medium according to claim 1, wherein the recording layer contains Ge, Sb, Te, and Sb.
And the content ratio [Sb / Te] in atomic% of Te is 0.01 ≦
An information recording medium satisfying [Sb / Te] ≦ 1, wherein the recording mark stabilizing layer contains at least Sb. 4. The information recording medium according to claim 1, wherein the recording layer contains Ge, Sb, Te, and Sb.
And the content ratio [Sb / Te] in atomic% of Te is 0.01 ≦
An information recording medium satisfying [Sb / Te] ≦ 1, wherein the recording mark stabilizing layer contains at least Te. 5. The information recording medium according to claim 1, wherein the recording layer contains Ge, Sb, Te, and Sb.
And the content ratio [Sb / Te] in atomic% of Te is 0.01 ≦
An information recording medium which satisfies [Sb / Te] ≦ 1, and wherein the recording mark stabilizing layer contains at least Ag. 6. The information recording medium according to claim 1, wherein the recording layer contains Ge, Sb, Te, and Sb.
And the content ratio [Sb / Te] in atomic% of Te is 0.01 ≦
[Sb / Te] ≦ 1, and the recording mark stabilizing layer has at least Sc, Ti, V, Cr, Mn, Fe, Co, N
i, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru,
Rh, Pd, Cd, Hf, Ta, W, Re, Os, I
r, Pt, Au, B, C, N, O, Al, Si, P, A
r, Ga, As, Se, In, Sn, Tl, Pb, Bi
An information recording medium comprising: 7. The information recording medium according to claim 1, wherein the recording layer contains Sb and Te, and the recording layer contains Sb and Te.
Content ratio in atomic% of [Sb / Te] is 1 <[Sb / Te]
≦ 10 and the recording mark stabilizing layer is at least Te
An information recording medium comprising: 8. The information recording medium according to claim 1, wherein the recording layer contains Sb and Te, and the recording layer contains Sb and Te.
Content ratio in atomic% of [Sb / Te] is 1 <[Sb / Te]
≤ 10 and the recording mark stabilizing layer has at least S
c, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, P
d, Ag, Cd, Hf, Ta, W, Re, Os, Ir,
Pt, Au, B, C, N, O, Al, Si, P, Ar,
Ga, As, Se, In, Ge, Sn, Tl, Pb, B
An information recording medium comprising i. 9. The information recording medium according to claim 2, wherein a part or all of the recording mark stabilizing layer is diffused into the recording film in the initialization process. 10. The information recording medium according to claim 2, wherein after the initialization, a part or all of the recording mark stabilizing layer is diffused into the recording film by annealing the medium. Information recording medium. 11. The information recording medium according to claim 2, wherein after the initialization, a part or all of the recording mark stabilizing layer is diffused into the recording film by irradiating the medium with light. An information recording medium characterized by the above-mentioned. 12. Initialization in which initial crystallization is performed by applying energy in order to crystallize a recording layer of an information recording medium provided with at least a recording layer and a recording mark stabilizing layer in contact with the recording layer on a substrate. A method for initializing an information recording medium, wherein a part or all of a recording mark stabilizing layer is diffused into a recording film in an initialization process. 13. Initialization in which initial crystallization is performed by applying energy to crystallize a recording layer of an information recording medium having at least a recording layer on a substrate and a recording mark stabilizing layer in contact with the recording layer. In the method and the information recording method of forming an amorphous mark by applying energy after initialization, the unit time applied at initialization, the energy intensity per unit area, the unit time applied at recording, the energy per unit area A method for initializing an information recording medium and a method for recording information, wherein the method is less than the intensity.