JPH09161316A - Optical information recording medium - Google Patents

Abstract

(57) An object of the present invention is to provide a rewritable phase change optical disk which is easily crystallized in the initial stage and can be recorded and erased at an extremely high speed. SOLUTION: SbxTe1-x (0.6 ≦ x ≦ is formed on a substrate.
A rewritable optical information recording medium having a phase change recording layer containing 0.85) as a main component, wherein a crystallization promoting layer for promoting crystallization of the recording layer is provided between the substrate and the recording layer. An optical information recording medium having the structure provided, wherein the recording layer is initially crystallized by irradiation with light energy.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical information recording medium. More specifically, the present invention relates to an optical information recording medium capable of extremely high-speed recording / erasing using a reflectance difference or a reflected light phase difference caused by a phase change caused by laser light irradiation.

[0002]

2. Description of the Related Art Optical discs include a read-only type, an optical recordable type, and a rewritable type.
It has already been put to practical use as an audio disk, and even as a large-capacity computer disk memory. Typical optical recording types include a perforation / deformation type, a magneto-optical type, and a phase change type. A recording layer made of a low melting point metal such as Te or a dye is used as the hole forming / deforming type, and is locally heated by laser light irradiation to form holes or concave portions.

The magneto-optical type performs recording and erasing according to the direction of magnetization of the recording layer, and reproduces due to the magneto-optical effect. CD
As a disc for recording format signals,
An optical disc having a recording layer made of a dye or a polymer containing the dye on a substrate, and an optical information recording method using the optical disc have been proposed.

On the other hand, the phase change type utilizes the fact that the reflectance or the phase of the reflected light changes before and after the phase change.
Playback is performed by detecting the difference in the amount of reflected light without the need for an external magnetic field. Compared to the magneto-optical type, the phase-change type is easy to manufacture a drive because it does not require a magnet and has a simple optical system, and is advantageous in downsizing and cost reduction.

Further, there is an advantage that recording / erasing can be performed only by modulating the power of the laser beam, and one-beam overwriting in which erasing and re-recording are simultaneously performed by a single beam is also possible. A chalcogen-based alloy thin film is often used as a recording layer material used in the phase change recording method.

For example, Ge-Te system, Ge-Te-Sb
System, In-Sb-Te system, Ge-Sn-Te system, Ag-
Attempts have been made to use In—Sb—Te alloy thin films and the like. In a phase change recording method capable of one-beam overwriting, it is general that a recording bit is formed by amorphizing a recording film and erasing is performed by crystallization.

In this case, the state immediately after film formation (so-called as-d
Since the epo state) is generally amorphous, it is necessary to crystallize the entire disk surface in a short time in order to make the initial state crystalline. This process is called initial crystallization. Usually, this initial crystallization is performed by irradiating a rotating disk with a laser beam focused to several tens to hundreds of microns.

[0008]

However, some phase change media are extremely difficult to be crystallized in the initial stage and are not good in productivity. For example, although a recording layer having a composition of Sb ₇₁ Te ₂₉ can record and erase by an amorphous-crystalline phase change at an extremely high speed, it is formed as a recording layer on a substrate and a laser beam is used. When irradiating and trying initial crystallization,
Many parts of the film remain in an amorphous state without being crystallized.

In some cases, the entire surface can be crystallized by repeating this operation several tens of times, but this is not practical and is not practical. One of the reasons why it is difficult to crystallize is that the amorphous state in the as-depo state is unlikely to crystallize unlike the amorphous state in the recording mark formed by irradiating the laser beam.

It is also considered that the crystal nuclei are hardly present in the recording layer in the as-depo state, which may be a cause of difficulty in crystallization. In fact, when observing a portion where initial crystallization is attempted by irradiating a laser beam with an optical microscope, the portion where crystallization is advanced is observed in an island shape. It can be understood that this is because crystallization progresses only in the part where the crystal nucleus is formed.

When using a recording layer whose initial crystallization is difficult as described above, the productivity is significantly deteriorated. That is, the recording layer containing SbTe alloy as a main component in the vicinity of the eutectic composition of Sb ₇₀ Te ₃₀ solves the problem of initial crystallization, so that the subsequent recording / erasing due to the amorphous-crystalline phase change can be performed at an extremely high speed. It becomes an optical information recording medium capable of recording.

Also, GeTe-Sb ₂ which is a typical recording layer widely known in repetitive overwrite.
There is also an advantage that the deterioration is less than that of the material near the Te ₃ pseudo binary alloy.

[0013]

[Means for Solving the Problems] SbxTe1-x on a substrate
A rewritable optical information recording medium provided with a phase change recording layer containing (0.6 ≦ x ≦ 0.85) as a main component, wherein a crystallization promoting layer is provided between a substrate and a recording layer. And an optical information recording medium characterized in that the recording layer is initially crystallized by irradiation with light energy.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention smoothes initial crystallization by providing a crystallization promoting layer for promoting crystallization of a recording layer in an optical information recording medium having a recording layer in which initial crystallization is difficult. Is to go to. The crystallization promoting layer serves as crystal nuclei and triggers crystallization of the recording layer. Alternatively, the recording layer provided on the crystallization promoting layer may be one that is considered to have a structure that facilitates crystallization during the deposition, and examples thereof include a metal that easily crystallizes, such as Au,
It may be Ag, Cu, Al, etc., but has a similar crystal structure,
Since it is preferably crystallized at the time of deposition by sputtering or the like and has a property such that the refractive index is close to that of the recording layer, S
When a recording layer containing bxTe1-x (0.6 ≦ x ≦ 0.85) as a main component is used, the crystallization promoting layer is SbzTe1-z.
A composition containing (0.2 ≦ z ≦ 0.7) as a main component is preferable.

The composition of SbzTe1-z (0.2.ltoreq.z.ltoreq.0.7) is often a crystal from the as-depo state, and tends to become crystal nuclei during initial crystallization, and a recording layer provided thereon. Is believed to play a role in making it easier to crystallize during deposition. When the composition range of the crystallization promoting layer is SbzTe1-z, 0.2 ≦ z ≦ 0.7 is preferable, and 0.3 ≦ z ≦ 0.5 is more preferable.

Further, SbzTe1-z (0.2≤z≤0.
7) and other metal such as Ge at 10 at. %, SbzTe1-z may be added in a range not deteriorating the crystallization promoting effect. Furthermore, for example, Ag ₁ Sb ₁ Te
₂ etc. can also be used as the crystallization promoting layer. To record an amorphous mark by irradiating a recording laser after initialization, it is usually heated to a temperature above the melting point of the recording layer. Conceivable.

Since the composition of the crystallization promoting layer is different from the composition of the recording layer, recording is repeatedly performed, and when both are mixed, the composition of the recording layer changes with time. Therefore, it is preferable that the crystallization promoting layer has a relatively thin film thickness of about 0.2 to 5 nm in order to reduce the composition change due to mixing. Further, in order to compensate for the change in composition when the recording layer and the crystallization promoting layer are mixed, a composition containing the difference component between the composition of the recording layer and the composition of the crystallization promoting layer as the main component is in contact with the crystallization promoting layer. It is also effective to provide a correction layer so that when the crystallization promoting layer and the composition correction layer are mixed, the composition is close to the composition of the recording layer.

The film thickness of the composition correction layer is determined in relation to the film thickness of the crystallization promoting layer. SbzTe1-z (0.2≤z≤0.
When the alloy of 7) is used as a recording layer, the problem of crystallization is only at the time of initialization, so there is no problem even if the composition of the crystallization promoting layer changes after the initial crystallization. Also from the viewpoint of the refractive index, the reflectance after initial crystallization may be different after recording several times, and therefore it is not preferable if the crystallization promoting layer is too thick.

If the crystallization accelerating layer is too thick, the recording signal will be useless during several overwrite recordings. If the thickness is too small, the effect of facilitating the initial crystallization becomes small. As the recording layer, a layer containing SbxTe1-x (0.6≤x≤0.85) as a main component is used.

As described above, the recording layer containing SbxTe1-x (0.6≤x≤0.85) as the main component can record and erase by the amorphous-crystalline phase change at an extremely high speed. . In order to increase the stability of the amorphous mark (recording bit) and adjust the crystallization speed, Ag, C
u, Ge, Si, In, Sn, Pd, Pt, Rh, P
d at least one selected from Co, Fe, Ni, Mg, Ta, Nb, and Ti at 20 at. % May be added.

Particularly, Ag, Ge, In, Si and Sn are preferable. That is, the recording layer is (SbxTe1-x) yM1-y (0.6
≦ x ≦ 0.85, 0.8 ≦ y ≦ 1, M is Ag, Cu, G
e, Si, In, Sn, Pd, Pt, Rh, Pd, C
An alloy of at least one selected from o, Fe, Ni, Mg, Ta, Nb, and Ti) is preferable.

The thickness of the recording layer is preferably about 15 to 100 nm. In order to protect the recording layer, the layer structure of the disk is often provided with a dielectric protective layer and a reflective layer in addition to the recording layer for optical design and heat dissipation effect design. The material for the dielectric protective layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion and the like.

Generally, M, which is highly transparent and has a high melting point,
g, Ca, Sr, Y, La, Ce, Ho, Er, Yb,
Ti, Zr, Hf, V, Nb, Ta, Zn, Al, S
oxides, sulfides, nitrides such as i, Ge, Pb, Ca, M
Fluorides such as g and Li can be used. These oxides, sulfides, nitrides, and fluorides do not always need to have a stoichiometric composition, and it is also effective to control the composition for controlling the refractive index and the like, or to use a mixture.

Considering the repetitive recording characteristics, a multiple dielectric mixture based on ZnS is preferable. The film thickness of the dielectric protective layer is usually about 15 to 300 nm. The reflective layer is preferably made of a material having a high reflectance, and Au, Ag, Cu, Al or the like is used. For controlling thermal conductivity, Ta, Ti, Cr,
A small amount of Mo, Mg, V, Nb, Zr or the like may be added.

As the substrate of the recording medium in the present invention,
It may be any of glass, plastic, and one provided with a photocurable resin on glass, but a polycarbonate resin is preferable from the viewpoint of productivity including cost. Recording layer,
The dielectric layer and the reflective layer are formed by a sputtering method or the like. It is desirable to form a film using an in-line apparatus in which a target for a recording film, a target for a protective film, and if necessary, a target for a reflective layer material are installed in the same vacuum chamber, from the viewpoint of preventing oxidation and contamination between layers. It is also excellent in terms of productivity.

[0026]

The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 As a dielectric protective layer on a polycarbonate substrate (Zn
S) ₈₀ (SiO ₂ ) ₂₀ layer is 230 nm, Sb ₂ Te ₃ layer is 0.25 nm as a crystallization promoting layer, and S is a composition correction layer.
The b layer is 0.25 nm, and the Sb ₇₂ Te ₂₈ layer is 2 as the recording layer.
0 nm, (ZnS) ₈₀ (SiO ₂ ) as a dielectric protection layer
₂₀ layers 20 nm, Al alloy layer 100 n as a reflection layer
m, and the layers were sequentially laminated by a magnetron sputtering method, and an ultraviolet curable resin was further provided to 4 μm to prepare a disk.

Using an optical disk initialization device in which the major axis length of the elliptical irradiation beam is about 50 microns, the disk rotation speed is 2700 rpm, the beam feed speed is 5 μm / rotation, and the disk radius is 64 mm. The laser power was 400 mW, the laser power at a position with a radius of 27 mm was 170 mW, and the initial crystallization was attempted by proportionally distributing the laser power between them and initial crystallization was possible.

Optical disk evaluation device (laser wavelength 780
nm, NA 0.55), and an EFM random signal at a linear velocity of 5.6 m / s (clock frequency is 4 times)
Was recorded. The ratio of the reflectance after the initial crystallization to the reflectance in the crystalline state after rewriting 10 times was 0.96 (after initial crystallization / after rewriting), which was not a big problem. For example, the 3T jitter was 6 ns or less for all 10 recordings.

Example 2 As a dielectric protective layer on a polycarbonate substrate (Zn
S) ₈₀ (SiO ₂ ) ₂₀ layer is 230 nm, Sb ₂ Te ₃ layer is 0.5 nm as a crystallization promoting layer, and Sb is a composition correction layer.
Layer is 0.5 nm, Sb ₇₂ Te ₂₈ layer is 19 n as a recording layer
m, a (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer as a dielectric protective layer having a thickness of 20 nm, and an Al alloy layer having a thickness of 100 nm as a reflective layer were sequentially laminated by a magnetron sputtering method, and an ultraviolet curable resin was further provided at 4 μm to prepare a disk.

Using an optical disk initializing device in which the major axis of the elliptical irradiation beam is about 50 microns, the disk rotation speed is 2700 rpm, the beam feed speed is 5 μm / rotation, and the disk radius is 64 mm. When the initial crystallization was attempted by setting the laser power of the above to 400 mW and the laser power at the position of the radius of 27 mm to 170 mW, the initial crystallization was possible.

Optical disk evaluation device (laser wavelength 780
nm, NA 0.55), and an EFM random signal at a linear velocity of 5.6 m / s (clock frequency is 4 times)
Was recorded. The ratio of the reflectance after the initial crystallization and the reflectance in the crystalline state after rewriting 10 times was 0.92, which was not a big problem. For example, the 3T jitter was 6 ns or less for all 10 recordings.

Example 3 As a dielectric protective layer on a polycarbonate substrate (Zn
S) ₈₀ (SiO ₂ ) ₂₀ layer 230 nm, crystallization promoting layer Sb ₂ Te ₃ layer 1 nm, composition correction layer Sb layer 1 nm, recording layer Sb ₇₂ Te ₂₈ layer 18 nm, dielectric protective layer ₂₀ layers of (ZnS) ₈₀ (SiO ₂ ) ₂₀
m, an Al alloy layer as a reflection layer having a thickness of 100 nm was sequentially laminated by a magnetron sputtering method, and an ultraviolet curable resin was further provided at 4 μm to prepare a disk.

Using an optical disk initializing device in which the major axis of the elliptical irradiation beam is about 50 microns, the disk rotation speed is 2700 rpm, the beam feed speed is 5 μm / rotation, and the disk radius is 64 mm. Laser power of 400mW, disk radius 27mm
When initial crystallization was attempted with the laser power at the position of 170 mW, initial crystallization was possible.

Optical disk evaluation device (laser wavelength 780
nm, NA 0.55), and an EFM random signal at a linear velocity of 5.6 m / s (clock frequency is 4 times)
Was recorded. The ratio of the reflectance after the initial crystallization and the reflectance in the crystalline state after rewriting 10 times was 0.88, which was not a big problem. For example, the 3T jitter was 7 ns or less for all 10 recordings.

Example 4 As a dielectric protective layer on a polycarbonate substrate (Zn
S) ₈₀ (SiO ₂ ) ₂₀ layer is 230 nm, Sb ₂ Te ₃ layer is 1 nm as a crystallization promoting layer, Sb layer is 1 nm as a composition correction layer, and Ge ₁₀ Sb ₆₇ Te ₂₃ layer is 18 n as a recording layer.
m, a (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer as a dielectric protective layer having a thickness of 20 nm, and an Al alloy layer having a thickness of 100 nm as a reflective layer were sequentially laminated by a magnetron sputtering method, and an ultraviolet curable resin was further provided at 4 μm to prepare a disk.

Using this disk, an optical disk initialization device in which the major axis length of an elliptical irradiation beam is about 50 microns is used, and the disk rotation speed is 2700 rpm, the beam feed speed is 5 μm / rotation, and the disk radius is 64 mm. When initial crystallization was attempted with a laser power of 170 mW at a power of 400 mW and a radius of 27 mm, initial crystallization was possible.

Optical disk evaluation device (laser wavelength 780
nm, NA 0.55), and an EFM random signal at a linear velocity of 2.8 m / s (the clock frequency is doubled)
Was recorded. The ratio between the reflectance after the initial crystallization and the reflectance in the crystalline state after rewriting 10 times was 0.90, which was not a big problem.

Example 5 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
The layer was 230 nm, and the Sb ₂ Te ₃ layer was 1
Ge ₁₀ Sb ₆₇ Te ₂₃ layer as a recording layer 19 nm,
A (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer having a thickness of 20 nm and an Al alloy layer having a thickness of 100 nm were sequentially laminated by a magnetron sputtering method, and further an ultraviolet curable resin was provided to a thickness of 4 μm to prepare a disk.

Using this disk, an optical disk initialization device in which the major axis length of the elliptical irradiation beam was about 50 microns was used, the disk rotation speed was 2700 rpm, the beam feed speed was 5 μm / rotation, and the laser power was 4 at a radius of 64 mm.
Laser power 170mW at 00mW and radius 27mm
When the initial crystallization was attempted with, the initial crystallization was possible.

Optical disk evaluation device (laser wavelength 780
nm, NA 0.55), and an EFM random signal at a linear velocity of 2.8 m / s (the clock frequency is doubled)
Was recorded. The ratio between the reflectance after the initial crystallization and the reflectance in the crystalline state after rewriting 10 times was 0.90, which was not a big problem.

Comparative Example 1 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
The layer is 230 nm, and the Sb ₇₂ Te ₂₈ layer is 20 n as the recording layer.
m, a (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer of 20 nm and an Al alloy layer of 100 nm were sequentially laminated by a magnetron sputtering method, and an ultraviolet curable resin was further provided to 4 μm to prepare a disk.

Using this disk, an optical disk initialization device in which the major axis length of the elliptical irradiation beam is about 50 microns is used, the disk rotation speed is 2700 rpm, the beam feed speed is 5 μm / rotation, and the laser power is 4 mm at a radius of 64 mm.
Laser power 170mW at 00mW and radius 27mm
The initial crystallization was attempted at, but the initial crystallization was not possible.

This disc was measured using an optical disc evaluation apparatus (laser wavelength 780 nm, NA 0.55) .2.
It is possible to initialize the width of about 1 micron by irradiating the laser beam of 6 mW about 100 times at the linear velocity of 8 m / s, but it takes too much time to initialize the entire surface of the disk by this method. Not at all. Comparative Example 2 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
Layer is 230 nm, Sb layer is 1 nm, Ge ₁₀ Sb ₆₇ Te ₂₃
19 nm layer, (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer 20 n
m, an Al alloy layer of 100 nm are sequentially laminated by a magnetron sputtering method, and further an ultraviolet curable resin is 4 μm.
The provided disk was produced.

Using this disk, an optical disk initialization device in which the major axis length of the elliptical irradiation beam was about 50 microns was used, the disk rotation speed was 2700 rpm, the beam feed speed was 5 μm / rotation, and the laser power was 4 at a radius of 64 mm.
Laser power 170mW at 00mW and radius 27mm
During that period, initial crystallization was attempted, but initial crystallization was not possible. From this result and Examples 4 and 5, it can be seen that the Sb ₂ Te ₃ layer facilitates the initialization.

Comparative Example 3 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
The layer is 230 nm, and the Sb ₇₂ Te ₂₈ layer is 18 n as a recording layer.
m, Sb layer 1 nm as a composition correction layer, Sb ₂ Te ₃ layer 1 nm as a crystallization promoting layer, (ZnS) ₈₀ (SiO ₂ ).
₂₀ layers of 20 nm and an Al alloy layer of 100 nm were sequentially laminated by a magnetron sputtering method, and an ultraviolet curable resin was further provided to 4 μm to prepare a disk.

Using this disk, an optical disk initialization device in which the major axis length of an elliptical irradiation beam is about 50 microns is used, the disk rotation speed is 2700 rpm, the beam feed speed is 5 μm / rotation, and the laser power is 4 at a radius of 64 mm.
Laser power 170mW at 00mW and radius 27mm
The initial crystallization was attempted at, but the initial crystallization was not possible. From this result and Example 3, it is found that the crystallization promoting layer should be provided between the substrate and the recording layer.

Comparative Example 4 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
A layer of 230 nm, a crystallization promoting layer of Sb ₂ Te ₃ layer of 5.4 nm, a recording layer of Sb ₇₂ Te ₂₈ layer of 20 nm,
A (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer having a thickness of 20 nm and an Al alloy layer having a thickness of 100 nm were sequentially laminated by a magnetron sputtering method, and further an ultraviolet curable resin was provided to a thickness of 4 μm to prepare a disk.

Using this disk, an optical disk initialization device in which the major axis length of the elliptical irradiation beam was about 50 microns was used, the disk rotation speed was 2700 rpm, the beam feed speed was 5 μm / rotation, and the laser power was 4 at a radius of 64 mm.
Laser power 170mW at 00mW and radius 27mm
When the initial crystallization was attempted with, the initial crystallization was possible.

Optical disk evaluation device (laser wavelength 780
nm, NA 0.55), and an EFM random signal at a linear velocity of 5.6 m / s (clock frequency is 4 times)
Was recorded. The ratio of the reflectance after the initial crystallization and the reflectance in the crystalline state after rewriting 10 times is 0.74,
It was found that the 3T jitter from 2 to 5 times recording was 17 ns or more, which was a problem.

[0050]

By using the optical information recording medium of the present invention, it is possible to obtain a rewritable phase change optical disk which is easily crystallized in the initial stage and can be erased and recorded at extremely high speed with high productivity. Moreover, the disc characteristics are not impaired.

Claims (5)

[Claims] 1. SbxTe1-x (0.6≤x≤ on a substrate
A rewritable optical information recording medium having a phase change recording layer containing 0.85) as a main component, wherein a crystallization promoting layer for promoting crystallization of the recording layer is provided between the substrate and the recording layer. An optical information recording medium having the structure provided, wherein the recording layer is initially crystallized by irradiation with light energy. 2. The optical information recording medium according to claim 1, wherein the crystallization promoting layer has a thickness of 0.2 to 5 nm. 3. The crystallization promoting layer is SbzTe1-z (0.
3. The optical information recording medium according to claim 1, which is made of an alloy containing 3 ≦ z ≦ 0.5) as a main component. 4. The recording layer is (SbxTe1-x) yM1-y (0.
6 ≦ x ≦ 0.85, 0.8 ≦ y ≦ 1, M is Ag, Cu,
Ge, Si, In, Sn, Pd, Pt, Rh, Pd, C
4. The optical information recording medium according to claim 1, which is an alloy of at least one selected from o, Fe, Ni, Mg, Ta, Nb, and Ti). 5. A composition correction layer containing a difference component between the composition of the recording layer and the composition of the crystallization promoting layer as a main component is provided between the crystallization promoting layer and the recording layer. 5. The optical information recording medium according to any one of 4 to 4.