JP2002237089A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve overwrite characteristics at the highest linear speed ensured by an optical information recording medium which is adaptive to multi- speed recording of, for example, >=3.6 m/S. SOLUTION: This optical information recording medium in which information can be recorded and erased on its recording surface while the relative speed between the recording surface when the information is recorded and erased and a recording device is within a range of VL<=V<=VH and the reflectance of the recording surface in an unrecorded state is Rb0, satisfies RbH/Rb0>1.03, where RbH denotes the reflectance off the recording surface in the unrecorded state which has been irradiated with light of optimum erasure light irradiation power PEH at the relative speed VH. Consequently, the recording surface is initialized so that the reflectance Rb0 is set to the optimum value a little less than the reflectance RbH of the recording surface having been erased at the relative speed VH, overwrite characteristics at the relative speed VH therefore becomes excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CD-RW, a DV
The present invention relates to an optical information recording medium typified by a phase change optical disk such as a D-RAM, a DVD-RW, a DVD + RW, and a PD, and a method of manufacturing the same.

[0002]

2. Description of the Related Art CD-RW, DVD-RAM, DVD-
In a rewritable optical information recording medium using a phase change represented by RW, DVD + RW, and PD, initialization is generally performed after the optical information recording medium is created. This is because the recording film immediately after film formation is in an amorphous state, and thus it is necessary to crystallize a recording region in such an amorphous state before actually recording information.

In such an initialization step, light emitted from a light source such as a high-power semiconductor laser or a gas laser is collected, irradiated on an optical information recording medium, and scanned. As a result, the recording layer is heated to be in a state of melting or close to melting, whereby the recording layer is in a state of crystallization or close to crystallization.

The initialization of an optical information recording medium is described in, for example, Japanese Patent Application Laid-Open Nos.
An example of the method is disclosed in Japanese Patent Publication No. 0-289647.

[0005]

In an optical information recording medium of the layer change type, the characteristics after overwriting greatly vary depending on the reflectance of the optical information recording medium after initialization.

[0006] In recent years, at the same time as the recording speed on the optical information recording medium has been increased, it is possible to cope with recording at a different recording speed (multi-speed recording) such as CAV recording. There is a demand for an optical information recording medium having good characteristics. In such a multi-speed phase change optical information recording medium, the overwrite characteristic at the highest recording speed is the most important characteristic.

An object of the present invention is to improve the overwrite characteristics at the maximum linear velocity guaranteed by an optical information recording medium, for example, in an optical information recording medium compatible with multi-speed recording of 3.6 m / S or more. It is.

[0008]

According to the first aspect of the present invention,
Recording, erasing, and reading of information can be performed by irradiating a recording surface with light by a recording device, and the relative speed V between the recording surface and the recording device at the time of recording and erasing information is VL ≦ V. Recording and erasing of information can be performed on the recording surface within a range of ≦ VH, and in an optical information recording medium in which the reflectance of the recording surface in an unrecorded state is Rb0, the recording surface in an unrecorded state is When the reflectance of the recording surface after light irradiation with the optimum erasing light irradiation power PEH at the relative speed VH is RbH, RbH / Rb0> 1.03.

According to a second aspect of the present invention, in the optical information recording medium according to the first aspect, RbH / Rb0 <1.10.

According to a third aspect of the present invention, there is provided the optical information recording medium according to the first or second aspect, wherein the recording surface in an unrecorded state is irradiated with light by an optimum erasing power PEL at a relative speed VL. When the reflectance of the recording surface is RbL, R
bL / Rb0 <1.15.

According to a fourth aspect of the present invention, in the optical information recording medium according to any one of the first to third aspects, the recording surface has a recording layer.
It is characterized by containing n, Sb and Te.

[0012] The invention according to claim 5 is the invention according to claims 1 to 4.
The optical information recording medium according to any one of the above, wherein VH / V
It is characterized by L ≧ 2.5.

[0013]

FIG. 1 shows an embodiment of an optical information recording medium to which the present invention is applied.

On a transparent substrate 1, a first dielectric layer 2, a recording layer 3, a second dielectric layer 4, a reflective layer 5, and a protective layer 6 are sequentially laminated. A print layer 7 may be laminated on the protective layer 6, and a hard coat layer 8 may be laminated on the lower surface of the transparent substrate 1.

The transparent substrate 1 needs to be transparent in a wavelength range of light for recording and reproducing an optical information recording medium. Examples of the material of the transparent substrate 1 include glass, ceramics, resin and the like, and it is preferable to use a resin from the viewpoint of transparency and ease of molding. In this case, examples of the resin include a polycarbonate resin, an acrylic resin, an epoxy resin, a polystyrene resin, an acrylonitrile-styrene copolymer resin, a polyethylene resin, a polypropylene resin, a silicone resin, a fluorine resin, an ABS resin, and a urethane resin. However, a polycarbonate resin and an acrylic resin which are excellent in moldability, optical properties and cost are preferable. Further, a guide groove (groove) may be formed on the transparent substrate 1.

A dielectric is used for the first dielectric layer 2, the second dielectric layer 4, and the recording layer 3 in consideration of thermal characteristics and optical characteristics. As the dielectric, SiO ₂ , SiO, ZnO, S
nO ₂ , TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂
Oxides such as Si ₃ N ₄ , AlN, TiN, BN,
Nitride such as ZrN, ZnS, In ₂ S ₃ , TaS ₄
Sulfide, SiC, TaC, B ₄ C, WC, TiC, Z
There are carbides such as rC or diamond-like carbon, and a single substance or a mixture of two or more of these dielectric substances is used.

Each of the dielectric layers is formed by using a vacuum film forming method.
Examples include an ion plating method and a CVD method, but it is preferable to use a sputtering method from the viewpoint of productivity and low cost. First dielectric layer 2 and second dielectric layer
The material and film thickness of the dielectric layer 4 can be set arbitrarily and independently, and an optimum value is set based on their optical characteristics and thermal characteristics. The thickness is about 10 nm to 5000 nm.

For the recording layer 3, a phase change material is used. As a phase change material suitable for an optical information recording medium, an alloy-based material is preferably used, and GeTe, GeTeSe, G
eTeS, GeSeSb, GeSeSb, GeAsS
e, InTe, SeTe, SeAs, Ge-Te- (S
n, Au, Pd), GeTeSeSb, GeTeSb,
AgInSbTe, GeInSbTe, GeAgInS
An alloy system of bTe can be exemplified. The composition ratio of each alloy system is optimized by the recording linear velocity of the non-temporary information recording medium. Further, any element may be mixed as an impurity into the alloy system containing the above element as a main component, and the mixed impurities include B, N, C, O, Si, P, Ge, S, S
e, Al, Ti, Zr, V, Mn, Fe, Co, Ni,
Examples thereof include Cr, Cu, Zn, Sn, Pd, Pt, and Au.

In particular, when AgInSbTe is used for the recording layer 3, the boundary between the stable phase (crystallized phase) formed by recording and the metastable phase (amorphous phase) is not clear. It is suitable for the recording method used. In this case, by adding a small amount of N as an impurity, it is possible to widen the recording linear velocity margin.

The recording layer 3 is laminated by a vacuum film forming method. Examples of the vacuum film forming method include a vacuum deposition method, a sputtering method, an ion plating method, and a CVD method.
Considering low cost and the like, it is desirable to use the sputtering method.

The reflection layer 5 has a function of reflecting recording / reproducing light and radiating heat generated during recording. As a material of the reflection layer 5 as such a reflection heat dissipation layer, metals, alloys, etc., for example, Ag, Au, Al, or T
An alloy in which one or more kinds of i, Si, Cr, Ta, Cu, Pd, C and the like are mixed can be used. However, in consideration of thermal characteristics, optical characteristics, productivity, and the like, it is preferable to use an alloy containing Al as a main component. The composition of the alloy and the film thickness of the reflective layer 5 can be arbitrarily set, and it is desirable to optimize the alloy from the thermal and optical characteristics.

For the protective layer 6, a resin material mainly composed of a photo-curable resin, an electron beam-curable resin or the like is used. As these resins, it is desirable to use a resin material containing a photocurable resin as a main component from the viewpoints of film formability and simplicity of curing. As the photocurable resin, an ultraviolet curable resin is generally used. Examples of the film forming method include a dipping method and a spin coating method.

In practice, one or more printed layers 7 are provided on the protective layer 6 of the optical information recording medium, and a label is formed with the printed layers 7 or a hard coat layer 8 is formed on the lower surface of the substrate 1. May be provided to improve the scratching strength. As a material of the print layer 7, a known photo-curable ink can be used, and a film is generally formed by screen printing. As the material and the film forming method of the hard coat layer 8, the same material as that of the protective layer 6 can be used.

Further, in practice, two optical information recording media may be bonded so that the surfaces of the protective layer 6 are joined to each other.

The recording layer 3 of the optical information recording medium thus prepared is generally in an amorphous or nearly amorphous state and has a low reflectance. In order to realize the optical information recording medium of the present invention, an initialization step for bringing the recording layer 3 of the optical information recording medium into a state of crystallization with high reflectance or a state close to crystallization is required. The initialization is performed by applying heat to the recording layer 3, heating the recording layer 3 to a crystallization temperature near the melting point or a temperature near the crystallization temperature, and then cooling. Such initialization is generally performed by scanning the recording layer 3 while irradiating the recording layer 3 with a laser. As a laser light source used in this case, a gas laser, a high-power semiconductor laser, or the like can be used. However, it is common to use a high-output semiconductor laser because of its simple control.

The recording on the optical information recording medium is performed by irradiating the recording layer 3 with a laser beam whose output has been modulated, and is preferably performed using a multi-pulse method. Examples of the recording method include those described in JP-A-09-138946. Examples of the recording method corresponding to recording at different relative speeds between the recording device and the optical information recording medium include: Examples described in Orange Book Part III vol.1 ver.2.0 or Orange Book Part III vol.2, which is a CD-RW standard, can be exemplified. In such a multi-pulse method, the recording power PW,
Generally, recording is performed at three levels of the erasing power PE and the bias power PB. The recording PW preferably has the same value for each pulse, but an individual value may be set for each pulse. The width of each pulse can be set arbitrarily.

The optimum recording method and recording power on the optical information recording medium can be changed according to the characteristics of the recording apparatus.
Recording power setting is OPC (Optimum Power Control)
Is generally determined by implementing
As a method, the γ method described in Orange Book Part III is generally used.

The erasing power PE can be arbitrarily set in accordance with the characteristics of the recording apparatus and the optical information recording medium as in the case of the recording PW, but is generally determined from the repetitive recording (direct overwrite) property. .

The optical information recording medium of the present embodiment can record, erase, and read information by irradiating the recording surface including the recording layer 3 with light, and can record and erase information on the recording surface. Speed relative to the recording device is VL ≦ V ≦ V
Recording and erasing of information can be performed on the recording surface within the range of H. In such an optical information recording medium according to the present embodiment, the relationship between the reflectance Rb0 of the recording surface after initialization and the reflectance Rb of the recording surface after initialization with the optimum erasing power PE is as follows. It is in the range shown in the following (1) to (3). That is, (1) relative speed VH with respect to the unrecorded recording surface
Assuming that the reflectivity of the recording surface after light irradiation by the optimum erasing light irradiation power PEH at RbH is RbH, RbH / Rb0> 1.
03. (2) RbH / Rb0 <1.10. (3) When the reflectance of the recording surface after irradiation with the optimum erasing power PEL at the relative speed VL to the recording surface in the unrecorded state is RbL, RbL / Rb0 <1.15.

Here, for the optical information recording medium, Rb is changed by changing the scanning speed and the irradiation laser power at the time of initialization.
0 can be changed, and the relationship between Rb0 and Rb when Rb0 is changed is as shown in FIG. That is, as shown in FIG. 2, in the region A of low Rb0, the crystallization state is insufficient, so that erasure by the recording device promotes crystallization and increases the reflectance of the recording surface. In the high region B, the crystallization by initialization is sufficiently performed, so that even if erasure is performed by the recording device, further initialization is impossible, and the reflectance of the recording surface does not increase.

In a phase change type optical information recording medium such as the present invention, the jitter generally increases when the first direct overwrite is performed on the recording after the initialization.
This is because the reflectance level where the recorded mark is erased is different from the reflectance level where the unmarked part is erased, and the reflectance level when the mark is overlaid on the mark and the mark is written on the unmarked part. The main reason is that the reflectance level differs from the recorded reflectance level. In particular, the difference between the former reflectance level from which a recording mark is erased and the reflectance level from which an unmarked portion is erased greatly affects the deterioration of jitter. This tendency generally increases as the recording speed increases. On the other hand, by setting Rb0 shown in FIG. 3 in the region A, it is possible to suppress the occurrence of a difference between these reflectance levels, thereby reducing the jitter after overwriting. .

Hereinafter, the optimum range will be described in detail.

The relative speed between the optical information recording medium and the recording device is V
And When V that can be recorded on the optical information recording medium satisfies VL ≦ V ≦ VH, it is assumed that the optimum erasing powers at the relative speeds VL and VH are PEL and PEH. After performing DC erasing by power PEL once at a relative speed VH using a recording device, the reflectance RbH of the erased portion was measured by the recording device.
Must be in the following range: RbH / Rb0> 1.03 By setting Rb0 in this range, the jitter when overwriting at the relative speed VH can be reduced.

If the reflectivity fluctuates greatly due to overwriting, a problem may occur. Therefore, it is preferable that RbH / Rb0 <1.10.

At a lower relative speed VL, the energy applied to the optical information recording medium at the time of erasing tends to increase.
Therefore, the increase in reflectance when erasing by PEL tends to be even higher. Therefore, it is preferable that RbL / Rb0 <1.15 in order to reduce the problem of the reflectance fluctuation of the overwrite at the relative speed VL.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventors of the present invention made an optical information recording medium similar to that of the above-described embodiment, and tried experiments.
The created embodiment is the following optical information recording medium.
Note that the same parts as those in the embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, a first dielectric layer 2, a recording layer 3, a second dielectric layer 4, and a protective layer 6 are sequentially laminated on a polycarbonate CD-RW transparent substrate 1 on which continuous grooves are transferred. CD-RW disc.

For the dielectric layers 2 and 4, a mixture of ZnS and SiO2 was used. The thickness of the first dielectric layer 2 is 70 to 90 n
m, and the thickness of the second dielectric layer 4 was 25 to 35 nm.

The recording layer 3 was made of an AgInSbTe alloy and had a thickness of 13 to 20 nm.

The reflective layer 5 was made of an AlTi alloy and had a thickness of 150 nm.

By changing the initialization condition, Rb
Samples in which 0, RbH and RbL were changed were prepared.

At this time, a scanning type initialization device using a high-power semiconductor laser was used as the initialization device. The specification of the light irradiation head in this initialization device is as follows: λ = 810
nm, radial beam width = 100 μm, scanning beam width = 1.0 μm, scanning pitch = 60 μm. The laser power of such a light irradiation head was set to 700 to 900 mW, and the scanning speed was set to 3 to 6 m / S.

The prepared sample was an optical information recording medium conforming to the CD-RW recordable by the recording method described in Orange Book Part III vol.

Next, the recording characteristics of the prepared sample were examined. As a recording device, a CD evaluation device DDU-1000 manufactured by Pulstec Industrial Co., Ltd. was used. The specifications of the optical pickup are as follows.・ Λ = 795 nm ・ NA = 0.50 And the recording method is Orange Book Part III vol.
The method described in 2 was used.

Samples range from 4X (4 times the speed of CD) to 1
High-s compatible up to 0X (10x CD speed) recording
speed CD-RW, relative speed VL = 4.8 m
/ S and relative speed VH = 12.0 m / S.

Further, PWH and PWL are set by the γ method.
EH and PEL were set so that the jitter after overwriting and the jitter after overwriting 1000 times were at the same level. The values are PWH = 20 mW, PWL = 19 mW, PEH = 9 mW, PEL = 8 mW.

With such a setting, 3T which is a recording characteristic when direct overwriting is performed once at VH (10X).
The relationship between jitter and RbH / Rb0 was measured. FIG. 3 shows the measurement results. In the Orange Book, which is the standard for CD-RW, the jitter is specified as 35 ns or less.
It can be seen that the lower the RbH / Rb0, the higher the jitter after overwriting and the worse the characteristics. The optical information recording medium having good characteristics needs to satisfy RbH / Rb0> 1.03.

Under the same conditions (relative speed VH), 1000
Reflectance Rtop1000 of the recording surface when recording up to the number of times
And the ratio of the reflectance Rtop0 of the reflective surface after the initial recording to Rtop0.
FIG. 4 shows the relationship with bH / Rb0. From FIG. 4, RbH
It can be seen that the higher / Rb0, the greater the increase in reflectance after 1000 overwrites. Since the change in the reflectance is preferably 10% or less, the appropriate range of RbH / Rb0 is about RbH / Rb0 <1.10.

FIG. 5 shows the result of similarly examining the RbL / Rb0 dependence of the reflectance fluctuation after overwriting 1000 times at the relative speed VL. As in the case of the recording at the relative speed VH, RbL / Rb0 <1.15 is an appropriate range in order to make the fluctuation of the reflectance after recording 10% or less.

[0050]

According to the optical information recording medium of the first aspect, the reflectance R of the recording surface when the recording surface is erased at the relative speed VH.
Since the reflectance Rb0 has been initialized to a lower optimal value with respect to bH, the overwrite characteristics at the relative speed VH can be improved.

According to the optical information recording medium of the present invention, the reflectance RbH of the recording surface when the recording surface is erased at the relative speed VH.
On the other hand, since the reflectance Rb0 is set to a close value, the variation in reflectance can be reduced in overwriting at the relative speed VH.

In the optical information recording medium according to the third aspect, the reflectance RbL of the recording surface when the recording surface is erased at the relative speed VL.
On the other hand, since the reflectance Rb0 is set to a close value, the variation in reflectance can be reduced in overwriting at the relative speed VL.

In the optical information recording medium according to the fourth aspect, since the elements contained in the recording layer are optimized, the overwrite characteristics at VH can be improved.

In the optical information recording medium according to the fifth aspect, since the ratio between the relative speeds VH and VL is 2.5 or more, CAV (constant angular velocity) is applied to a general 12 cm diameter optical disk.
It can correspond to the record.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of an optical information recording medium.

FIG. 2 shows the reflectance Rb0 of the recording surface after initialization and the reflectance Rb of the recording surface after initialization with the optimum erasing power PE.
7 is a graph showing the relationship between Rb0 and Rb when Rb0 is changed for the above.

FIG. 3 shows a relative speed VH (10X) with respect to a recording surface;
3 which is the recording characteristic when direct overwriting
9 is a graph showing a relationship between T jitter and RbH / Rb0.

FIG. 4 is a graph showing a relationship between RbH / Rb0 and the ratio of the reflectance Rtop1000 of the recording surface after recording up to 1000 times at the relative speed VH to the reflectance Rtop0 of the recording surface after the initial recording.

FIG. 5 is a graph showing the relationship between the ratio of the reflectance Rtop1000 of the recording surface when recording is performed up to 1000 times at the relative speed VL to the reflectance Rtop0 of the recording surface after the initial recording, and RbH / Rb0.

[Explanation of symbols]

 3 Recording layer

Claims (5)

[Claims] An information recording, erasing and reading operation can be performed by irradiating a recording surface with light by a recording device, and a relative speed between the recording surface and the recording device at the time of recording and erasing information. Recording and erasing of information can be performed on the recording surface in a range where V is VL ≦ V ≦ VH, and in an optical information recording medium in which the reflectance of the unrecorded recording surface is Rb0, RbH / Rb0> 1.03, where RbH is the reflectance of the recording surface after light irradiation with the optimum erasing light irradiation power PEH at the relative speed VH to the recording surface. A changeable optical information recording medium. 2. The optical information recording medium according to claim 1, wherein RbH / Rb0 <1.10. 3. The optical information recording medium according to claim 1, wherein a relative velocity VL is applied to the recording surface in an unrecorded state.
RbL / Rb0 <1.15, where RbL is the reflectivity of the recording surface after light irradiation by the optimum erasing power PEL in the optical information recording medium. 4. The optical information recording medium according to claim 1, wherein the recording surface has a recording layer, and the recording layer contains at least Ag, In, Sb, and Te. An optical information recording medium, characterized in that: 5. The optical information recording medium according to claim 1, wherein VH / VL ≧ 2.5.