JP3810462B2 - Optical information recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical information recording medium. More specifically, the present invention relates to an optical information recording medium capable of performing recording erasure using a reflectance difference or a reflected light phase difference caused by a phase change caused by laser light irradiation at an extremely high speed.
[0002]
[Prior art]
There are two types of optical disks: read-only, optical recordable, and rewritable, and the read-only is already in practical use as a video disk, audio disk, and disk memory for large-capacity computers.
Typical examples of the optical recordable type include a punching / deformation type, a magneto-optical type and a phase change type. As the drilling / deformation type, a low melting point metal such as Te or a recording layer such as a dye is used, and is locally heated by laser light irradiation to form holes or recesses.
[0003]
The magneto-optical type performs recording and erasing according to the magnetization direction of the recording layer, and performs reproduction by the magneto-optical effect.
As a disk for recording a CD format signal, an optical disk having a recording layer made of a dye or a polymer containing a dye on a substrate and an optical information recording method using the optical disk have been proposed.
[0004]
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, and does not require an external magnetic field and performs reproduction by detecting the difference in the amount of reflected light.
Compared with the magneto-optical type, the phase change type does not require a magnet and the optical system is simple, so that the drive can be easily manufactured, which is advantageous for downsizing and cost reduction.
[0005]
Further, recording / erasing can be performed only by modulating the power of the laser beam, and there is an advantage that one-beam overwriting in which erasing and re-recording are performed simultaneously with a single beam is possible.
As a recording layer material used in the phase change recording system, a chalcogen alloy thin film is often used.
[0006]
For example, the use of Ge—Te, Ge—Te—Sb, In—Sb—Te, Ge—Sn—Te, Ag—In—Sb—Te alloy thin films has been attempted.
In a phase change recording method capable of one-beam overwriting, a recording bit is generally formed by amorphizing a recording film and erasing is performed by crystallization.
[0007]
In this case, since the state immediately after the film formation (so-called as-depo state) is generally amorphous, it is necessary to crystallize the entire disk surface in a short time in order to change the initial state to the crystalline state.
This process is called initial crystallization. Usually, this initial crystallization is performed by irradiating a rotating disk with a laser beam focused to about several tens to one hundred microns.
[0008]
[Problems to be solved by the invention]
However, some phase change media are very difficult to initially crystallize and are not productive.
For example, a recording layer having a composition of Sb ₇₁ Te ₂₉ can perform recording and erasing by an amorphous-crystal phase change at a very high speed. When initial crystallization is attempted by irradiation, many portions of the film remain in an amorphous state without being crystallized.
[0009]
In some cases, the entire surface can be crystallized by repeating this operation several tens of times, but this is not practical because of low productivity.
One of the causes of difficulty in crystallization is considered to be that the amorphous state in the as-depo state is difficult to crystallize unlike the amorphous state in the recording mark formed by laser beam irradiation.
[0010]
In addition, the fact that there are almost no crystal nuclei in the recording layer in the as-depo state may be a cause of difficulty in crystallization.
In fact, when the portion where initial crystallization was attempted by irradiating a laser beam with an optical microscope is observed, the portion where crystallization has proceeded is observed in an island shape.
It can be understood that crystallization proceeds only in the portion where the crystal nucleus is formed.
[0011]
Thus, when trying to use a recording layer in which initial crystallization is difficult, productivity is remarkably deteriorated.
That is, the recording layer mainly composed of an SbTe alloy in the vicinity of the Sb ₇₀ Te ₃₀ eutectic composition solves the problem of initial crystallization, and the subsequent recording / erasing due to the amorphous-crystal phase change should be performed at a very high speed. Thus, the optical information recording medium can be used.
[0012]
In addition, there is also an advantage that the material is less deteriorated than a material in the vicinity of GeTe—Sb ₂ Te ₃ pseudo binary alloy, which is a typical recording layer widely known for repeated overwriting.
[0013]
[Means for Solving the Problems]
The gist of the present invention is a rewritable optical information recording medium in which a phase change recording layer mainly composed of Sb x Te 1-x (0.6 ≦ x ≦ 0.85) is provided on a substrate. And a crystallization promoting layer for promoting crystallization of the recording layer is provided between the substrate and the recording layer, and the crystallization promoting layer is SbzTe 1 -z (0.3 ≦ z ≦ 0.5). And an optical information recording medium characterized in that the recording layer is initially crystallized by light energy irradiation.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention intends to smoothly perform initial crystallization by providing a crystallization promoting layer that promotes crystallization of a recording layer on an optical information recording medium having a recording layer that is difficult to perform initial crystallization. is there.
The crystallization promoting layer serves as a crystal nucleus and triggers the crystallization of the recording layer. Alternatively, any recording layer provided on the crystallization promoting layer may be used as long as the recording layer is considered to have a structure that is easily crystallized at the time of deposition . For example, a metal that is easily crystallized, such as Au, Ag, Cu, Al, etc. SbxTe1-x (0.6 ≦ x ≦ 0.85) is preferable because it has a similar crystal structure and is already crystallized at the time of deposition by sputtering or the like and has a property such as a refractive index close to that of the recording layer. When the recording layer containing the main component is used, the crystallization promoting layer preferably has a composition containing SbzTe1-z (0.2 ≦ z ≦ 0.7) as the main component.
[0015]
The composition of SbzTe1-z (0.2 ≦ z ≦ 0.7) is often a crystal from the as-depo state and tends to be a crystal nucleus during initial crystallization, and the recording layer provided thereon is deposited. It is thought that it serves to make it easy to crystallize.
The composition range of the crystallization promoting layer is preferably 0.2 ≦ z ≦ 0.7, more preferably 0.3 ≦ z ≦ 0.5, when SbzTe1-z.
[0016]
Further, another metal such as Ge is added to the alloy made of SbzTe1-z (0.2 ≦ z ≦ 0.7) at 10 at. You may add to the extent which does not reduce the crystallization promotion effect of SbzTe1-z.
Further, for example, Ag ₁ Sb ₁ Te ₂ can be used as the crystallization promoting layer.
In order to record an amorphous mark by irradiating a recording laser after initialization, it is usually heated to the melting point or higher of the recording layer. Therefore, the crystallization promoting layer melts together with the recording layer during recording, and both are mixed to some extent. Conceivable.
[0017]
Since the composition of the crystallization promoting layer is different from the composition of the recording layer, repeated recording is performed, and when the two 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 a change in composition 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 mainly comprising a difference component between the composition of the recording layer and the composition of the crystallization promoting layer 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 becomes close to the recording layer composition.
[0018]
The film thickness of the composition correction layer is determined by the relationship with the film thickness of the crystallization promoting layer.
Since the problem of crystallization when the alloy composed of SbzTe1-z (0.2 ≦ z ≦ 0.7) is used as the crystallization promotion layer is a problem only at the time of initialization, the composition of the crystallization promotion layer after the initial crystallization There is no problem even if changes.
Also from the viewpoint of the refractive index, the reflectivity after the initial crystallization may be different when recording is performed several times.
[0019]
If the crystallization promoting layer is too thick, the recording signal at the time of several overwrite recordings will not occur.
If it is too thin, the effect of facilitating initial crystallization becomes small.
As the recording layer, a layer mainly composed of SbxTe1-x (0.6 ≦ x ≦ 0.85) is used.
[0020]
As described above, the recording layer containing SbxTe1-x (0.6 ≦ x ≦ 0.85) as a main component can perform recording / erasing by amorphous-crystalline phase change at an extremely high speed.
Ag, Cu, Ge, Si, In, Sn, Pd, Pt, Rh, Pd, Co, Fe, Ni, Mg are used to increase the stability of amorphous marks (recording bits) and adjust the crystallization speed. , Ta, Nb, Ti at least one selected from 20 at. % May be added.
[0021]
In particular, 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, Ge, Si, In, Sn, Pd, Pt, An alloy made of at least one selected from Rh, Pd, Co, Fe, Ni, Mg, Ta, Nb, and Ti) is preferable.
[0022]
The film 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 design.
The dielectric protective layer material is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like.
[0023]
Generally, Mg, Ca, Sr, Y, La, Ce, Ho, Er, Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Si, Ge, which have high transparency and high melting point, Oxides such as Pb, sulfides, nitrides, and fluorides such as Ca, Mg, and Li can be used.
These oxides, sulfides, nitrides, and fluorides do not necessarily have a stoichiometric composition, and it is also effective to use a composition or a mixture for controlling the refractive index and the like.
[0024]
In consideration of repeated 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 high reflectivity, and Au, Ag, Cu, Al, etc. are used, and a small amount of Ta, Ti, Cr, Mo, Mg, V, Nb, Zr, etc. is added to control the thermal conductivity. Also good.
[0025]
The substrate of the recording medium in the present invention may be any of glass, plastic, glass provided with a photocurable resin, and the like, but polycarbonate resin is preferable in terms of productivity including cost.
The recording layer, dielectric layer, and reflective layer are formed by sputtering or the like.
In order to prevent oxidation and contamination between layers, it is desirable to form a film with 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. It is also excellent in terms of productivity.
[0026]
【Example】
The present invention will be further described with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
Example 1
(ZnS) ₈₀ (SiO ₂ ) ₂₀ layer as a dielectric protective layer is 230 nm on a polycarbonate substrate, Sb ₂ Te ₃ layer is 0.25 nm as a crystallization promoting layer, Sb layer is 0.25 nm as a composition correction layer, and recording layer 20nm and Sb ₇₂ Te ₂₈ layer as a, a dielectric protective layer _{(ZnS) 80 (SiO 2)} 20nm to ₂₀ layers, 100 nm of Al alloy layer as a reflective layer, laminated in order magnetron sputtering, a further UV-curable resin A disk having a thickness of 4 μm was prepared.
[0027]
Using this disk, an optical disk initialization apparatus in which the major axis length of the elliptical irradiation beam was about 50 microns, the laser power at a disk rotation speed of 2700 rpm, a beam feed speed of 5 μm / rotation, and a disk radius of 64 mm Was 400 mW, the laser power at a position of a radius of 27 mm was set to 170 mW, and initial crystallization was attempted by proportionally distributing the laser power, and initial crystallization was possible.
[0028]
Using an optical disk evaluation apparatus (laser wavelength 780 nm, NA 0.55), an EFM random signal (clock frequency was quadrupled) was recorded at a linear velocity of 5.6 m / s.
The ratio between the reflectivity after the initial crystallization and the reflectivity of the crystal state after 10 rewrites was 0.96 (after the initial crystallization / after the rewrite), and there was no significant problem.
For example, 3T jitter was all 6 ns or less until 10 recordings.
[0029]
Example 2
(ZnS) ₈₀ (SiO ₂ ) ₂₀ layer as a dielectric protective layer on a polycarbonate substrate is 230 nm, Sb ₂ Te ₃ layer is 0.5 nm as a crystallization promoting layer, Sb layer is 0.5 nm as a composition correction layer, and recording layer The Sb ₇₂ Te ₂₈ layer is 19 nm, the dielectric protective layer (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 20 nm, the Al alloy layer is 100 nm as the reflective layer, and sequentially laminated by magnetron sputtering. A disk having a thickness of 4 μm was prepared.
[0030]
Using this disk, an optical disk initialization apparatus in which the major axis length of the elliptical irradiation beam was about 50 microns, the laser power at a disk rotation speed of 2700 rpm, a beam feed speed of 5 μm / rotation, and a disk radius of 64 mm When initial crystallization was attempted with a laser power of 170 mW at a position of 400 mW and a radius of 27 mm, initial crystallization was possible.
[0031]
Using an optical disk evaluation apparatus (laser wavelength 780 nm, NA 0.55), an EFM random signal (clock frequency was quadrupled) was recorded at a linear velocity of 5.6 m / s.
The ratio between the reflectivity after initial crystallization and the reflectivity after crystallizing 10 times was 0.92, and there was no major problem.
For example, 3T jitter was all 6 ns or less until 10 recordings.
[0032]
Example 3
A (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer as a dielectric protective layer is 230 nm on a polycarbonate substrate, a Sb ₂ Te ₃ layer is 1 nm as a crystallization promoting layer, a Sb layer is 1 nm as a composition correction layer, and a Sb ₇₂ Te as a recording layer. _{The 28} layers are 18 nm, the (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 20 nm as the dielectric protective layer, the Al alloy layer is 100 nm as the reflective layer, and sequentially laminated by magnetron sputtering, and further 4 μm of UV curable resin is provided. Produced.
[0033]
Using this disk, an optical disk initialization apparatus in which the major axis length of the elliptical irradiation beam was about 50 microns, the laser power at a disk rotation speed of 2700 rpm, a beam feed speed of 5 μm / rotation, and a disk radius of 64 mm When initial crystallization was attempted with a laser power of 170 mW at a position of 400 mW and a disk radius of 27 mm, initial crystallization was possible.
[0034]
Using an optical disk evaluation apparatus (laser wavelength 780 nm, NA 0.55), an EFM random signal (clock frequency was quadrupled) was recorded at a linear velocity of 5.6 m / s.
The ratio between the reflectivity after the initial crystallization and the crystal state reflectivity after 10 rewrites was 0.88, and there was no major problem.
For example, 3T jitter was all 7 ns or less until 10 recordings.
[0035]
Example 4
A (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer as a dielectric protective layer is 230 nm on a polycarbonate substrate, a Sb ₂ Te ₃ layer is 1 nm as a crystallization promoting layer, a Sb layer is 1 nm as a composition correction layer, and a Ge ₁₀ Sb as a recording layer ₆₇ Te ₂₃ layer is 18 nm, (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 20 nm as the dielectric protective layer, Al alloy layer is 100 nm as the reflective layer, sequentially laminated by magnetron sputtering method, and UV curable resin is provided 4 μm A disk was made.
[0036]
Using this optical disc initialization apparatus in which the length of the major axis of the elliptical irradiation beam is about 50 microns, the disc rotation speed is 2700 rpm, the beam feed speed is 5 μm / rotation, the laser power is 400 mW at the disc radius of 64 mm, When initial crystallization was attempted with a laser power of 170 mW at a radius of 27 mm, initial crystallization was possible.
[0037]
Using an optical disk evaluation apparatus (laser wavelength 780 nm, NA 0.55), an EFM random signal (clock frequency was doubled) was recorded at a linear velocity of 2.8 m / s.
The ratio between the reflectivity after initial crystallization and the reflectivity after rewriting 10 times was 0.90, and there was no major problem.
[0038]
Example 5
(ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 230 nm on the polycarbonate substrate, Sb ₂ Te ₃ layer is 1 nm as the crystallization promoting layer, Ge ₁₀ Sb ₆₇ Te ₂₃ layer is 19 nm as the recording layer, and (ZnS) ₈₀ (SiO ₂ ). The ₂₀ layers were laminated to 20 nm, the Al alloy layer was laminated to 100 nm in order by the magnetron sputtering method, and 4 μm of ultraviolet curable resin was further provided to produce a disk.
[0039]
Using this disk, an optical disk initialization apparatus in which the length of 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, the laser power is 400 mW at a radius of 64 mm, and the radius is 27 mm. When initial crystallization was attempted with a laser power of 170 mW, initial crystallization was possible.
[0040]
Using an optical disk evaluation apparatus (laser wavelength 780 nm, NA 0.55), an EFM random signal (clock frequency was doubled) was recorded at a linear velocity of 2.8 m / s.
The ratio between the reflectivity after initial crystallization and the reflectivity after rewriting 10 times was 0.90, and there was no major problem.
[0041]
Comparative Example 1
(ZnS) ₈₀ (SiO ₂ ) ₂₀ layer on a polycarbonate substrate is 230 nm, Sb ₇₂ Te ₂₈ layer is 20 nm as a recording layer, (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 20 nm, Al alloy layer is 100 nm, sequentially magnetron sputtering The disc was manufactured by laminating by the method, and further providing 4 μm of UV curable resin.
[0042]
Using this disk, an optical disk initialization apparatus in which the length of 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, the laser power is 400 mW at a radius of 64 mm, and the radius is 27 mm. Initial crystallization was attempted with a laser power of 170 mW, but initial crystallization could not be achieved.
[0043]
This disk can be initialized to a width of about 1 micron by irradiating a laser beam of 6 mW about 100 times at a linear velocity of 2.8 m / s using an optical disk evaluation apparatus (laser wavelength 780 nm, NA 0.55). Although it is possible, it takes much time to initialize the entire disk surface by this method, which is not practical.
Comparative Example 2
(ZnS) ₈₀ (SiO ₂ ) ₂₀ layer on a polycarbonate substrate is 230 nm, Sb layer is 1 nm, Ge ₁₀ Sb ₆₇ Te ₂₃ layer is 19 nm, (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 20 nm, Al alloy layer is 100 nm Then, the layers were sequentially laminated by a magnetron sputtering method, and further 4 μm of an ultraviolet curable resin was provided to produce a disk.
[0044]
Using this disk, an optical disk initialization apparatus in which the length of 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, the laser power is 400 mW at a radius of 64 mm, and the radius is 27 mm. In the meantime, initial crystallization was attempted, but initial crystallization could not be performed.
From this result and Examples 4 and 5, it can be seen that the Sb ₂ Te ₃ layer facilitates initialization.
[0045]
Comparative Example 3
(ZnS) ₈₀ (SiO ₂ ) ₂₀ layer on a polycarbonate substrate is 230 nm, Sb ₇₂ Te ₂₈ layer is 18 nm as a recording layer, Sb layer is 1 nm as a composition correction layer, Sb ₂ Te ₃ layer is 1 nm as a crystallization promoting layer, A (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer and an Al alloy layer of 100 nm were sequentially laminated by a magnetron sputtering method, and 4 μm of an ultraviolet curable resin was further provided to produce a disk.
[0046]
Using this disk, an optical disk initialization apparatus in which the length of 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, the laser power is 400 mW at a radius of 64 mm, and the radius is 27 mm. Initial crystallization was attempted with a laser power of 170 mW, but initial crystallization could not be achieved.
From this result and Example 3, it can be seen that the crystallization promoting layer is preferably provided between the substrate and the recording layer.
[0047]
Example 6
On the polycarbonate substrate, (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 230 nm, Sb ₂ Te ₃ layer is 5.4 nm as crystallization promoting layer, Sb ₇₂ Te ₂₈ layer is 20 nm as recording layer, (ZnS) ₈₀ (SiO ₂ The ₂₀ layers were laminated to 20 nm, the Al alloy layer was laminated to 100 nm in order by the magnetron sputtering method, and 4 μm of ultraviolet curable resin was further provided to produce a disk.
[0048]
Using this disk, an optical disk initialization apparatus in which the length of 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, the laser power is 400 mW at a radius of 64 mm, and the radius is 27 mm. When initial crystallization was attempted with a laser power of 170 mW, initial crystallization was possible.
[0049]
Using an optical disk evaluation apparatus (laser wavelength 780 nm, NA 0.55), an EFM random signal (clock frequency was quadrupled) was recorded at a linear velocity of 5.6 m / s.
The ratio between the reflectivity after the initial crystallization and the reflectivity of the crystal state after 10 rewrites was 0.74, and it was found that the 3T jitter until 2 to 5 times recording was 17 ns or more, which was a problem.
[0050]
【The invention's effect】
By using the optical information recording medium of the present invention, it is possible to obtain a rewritable phase change optical disk that can be easily crystallized easily and can be erased at a very high speed. Also, the disk characteristics are not impaired.

Claims (4)

A rewritable optical information recording medium comprising a phase change recording layer comprising SbxTe1-x (0.6 ≦ x ≦ 0.85) as a main component on a substrate, between the substrate and the recording layer And a crystallization promoting layer for promoting crystallization of the recording layer, wherein the crystallization promoting layer is made of an alloy mainly composed of SbzTe 1 -z (0.3 ≦ z ≦ 0.5), An optical information recording medium, wherein the recording layer is initially crystallized by light energy irradiation. The optical information recording medium according to claim 1, wherein the crystallization promoting layer has a thickness of 0.2 to 5 nm. 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, 3. The optical information recording medium according to claim 1 , wherein the optical information recording medium is an alloy made of at least one selected from Pd, Co, Fe, Ni, Mg, Ta, Nb, and Ti. Any one of claims 1, characterized in that provided between the composition correction layer for a difference component of the composition of the recording layer and the composition of the crystallization promoting layer mainly the crystallization accelerating layer and the recording layer 3 2. An optical information recording medium described in 1.