JP2002321458A - Photorecording medium and method for regenerating record - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase-changing photorecording medium which is useful for a rewritable compact disc(CD-RW) capable of realizing reproduction compatibility with a DVD disc. SOLUTION: In the photorecording medium consisting of a first dielectric layer, a recording layer, a second dielectric layer, a metallic or alloy layer and a UV-setting resin layer laminated, in that order, on a disc-like substrate, the constituent elements of the recording layer are mainly Ag, In, Sb, Te, N and/or O. The composition ratio of these elements is α, β, γ, δ and ε (ε is the sum of N and O). In addition, (atomic %) is 0<α<=6, 3<=β<=15, 50<=γ<=65, 20<=δ<=35, 0<=ε<=5, and α+β+γ+δ+ε=100. This photorecording medium is characterized in that the upper limit linear speed of its recrystallization of the recording layer is 2.5 to 5.0 m/s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, in particular, to a phase change type light which irradiates a light beam to cause a phase change in a material of a recording layer to record / reproduce information and rewrite information. An information recording medium and a method for reproducing the same are applied to optical memory-related equipment, particularly, a rewritable compact disc (CD-RW).

[0002]

2. Description of the Related Art As one of optical memory media capable of recording, reproducing and erasing by irradiation of electromagnetic waves, particularly laser beams, so-called phase-change optical recording utilizing a transition between a crystal and an amorphous phase or between a crystal and a crystal phase. The medium is well known. In particular, overwriting with a single beam, which is difficult with a magneto-optical memory, is possible, and the drive-side optical system is simpler.

As a typical example, US Pat.
41, Ge-Te, Ge-Te
-Sn, Ge-Te-S, Ge-Se-S, Ge-Se
-Sb, Ge-As-Se, In-Te, Se-Te,
A so-called chalcogen-based alloy material such as Se-As can be used. For the purpose of improving stability, high-speed crystallization, etc., Au (Japanese Patent Application Laid-Open No.
No.), Sn and Au (Japanese Patent Laid-Open No. 61-270190)
No.), Pd (Japanese Patent Application Laid-Open No. 62-19490), and the composition ratio of Ge-Te-Se-Sb and Ge-Te-Sb for the purpose of improving the recording / erasing repetition performance. (Japanese Patent Application Laid-Open Nos. 62-73438 and 63-228433) have also been proposed. However, none of them can be said to satisfy all of the characteristics required as a phase-change rewritable optical memory medium. In particular, improvements in recording sensitivity and erasing sensitivity,
Prevention of reduction of erase ratio due to unerased residue at overwriting,
In addition, extending the life of a recorded portion and an unrecorded portion is the most important issue to be solved.

Japanese Patent Application Laid-Open No. 63-251290 proposes an optical recording medium having a recording layer composed of a single layer of a multi-component compound having a crystalline state of substantially three or more. Here, the ternary or more multi-component compound monolayer is defined as a material containing 90 atomic% or more of a compound having a stoichiometric composition of three or more (for example, In ₃ SbTe ₂ ) in the recording layer. I have. It is stated that by using such a recording layer, recording and erasing characteristics can be improved. However, it has disadvantages such as a small erasing ratio and a laser power required for recording / erasing has not yet been sufficiently reduced.

Further, Japanese Patent Application Laid-Open No. 1-277338 discloses (SbaTe ₁ -a) ₁ -yMy (where 0.4 ≦ a ≦
0.7, y ≦ 0.2, and M is Ag, Al, As, A
u, Bi, Cu, Ga, Ge, In, Pb, Pt, S
It is at least one selected from the group consisting of e, Si, Sn and Zn. An optical recording medium having a recording layer made of an alloy having a composition represented by (1) has been proposed. The basis of this system is Sb ₂ Te ₃ , and when Sb is excessive, high-speed erasing and repetition characteristics are improved, and addition of M promotes high-speed erasing. In addition, the erasing ratio by DC light is also large. However, this document does not show the erasing ratio at the time of overwriting (the result of the study by the present inventors shows that the erasing remains), and the recording sensitivity is insufficient.

Similarly, in JP _-A- 60-177446, (In _1-x Sbx) _1-y My (0.55 ≦ x ≦
0.80, 0 ≦ y ≦ 0.20, and M is Au, Ag,
Cu, Pd, Pt, Al, Si, Ge, Ga, Sn, T
e, Se and Bi. ), And in Japanese Patent Application Laid-Open No. 63-228433, GeTe-Sb ₂
Although an alloy of Te ₃ —Sb (excess) was used, none of the alloys satisfied characteristics such as sensitivity and erasure. In addition, Japanese Patent Application Laid-Open No. Hei 4-163839 discloses a recording thin film Te-G.
forming e-Sb by including N in the alloy;
JP-A-4-52188 discloses that a recording thin film is made of Te-Ge-S
e-alloy containing at least one of these components in the form of a nitride.
No. 89 describes an optical recording medium in which a recording thin film is formed by adsorbing N to a Te-Ge-Se alloy, and each of the recording thin films is provided. However, it has not been possible to obtain those optical recording media having sufficient characteristics.

As has been seen so far, in the optical recording medium, in particular, the recording sensitivity and the erasing sensitivity have been improved, the erasing ratio has been prevented from lowering due to the unerased portion at the time of overwriting, and the life of the recorded and unrecorded portions has been extended. This is the most important issue to be solved.

On the other hand, with the rapid spread of CDs (compact discs) in recent years, write-once write-once compact discs (CD-Rs) that can be written only once have been developed and have begun to spread on the market. However, in the case of a CD-R, if the write operation fails even once, it cannot be corrected, and the disk becomes unusable and must be discarded. Therefore, there has been a long-awaited demand for a rewritable compact disc that can compensate for the disadvantage. One example of research and development is a rewritable compact disk using a magneto-optical disk, but it has drawbacks such as difficulty in overwriting and compatibility with CD-ROM and CD-R. Practical development of a phase-change optical disc that is advantageous in principle for ensuring compatibility has been activated.

Examples of research presentations on rewritable compact discs using phase-change optical discs include Furuya (etc.): Proceedings of the 4th Symposium on Phase Change Recording, 70 (1992), Kamino (etc.): Proceedings of the 4th Symposium on Phase Change Records, 76 (1992), Kawanishi (etc.): Proceedings of the 4th Symposium on Phase Change Records, 82 (1992), T. Handa (et a
l): Jpn. J. Appl. Phys. , 32 (19
93), Yoneda (etc.): Proceedings of the 5th Symposium on Phase Change Records, 9 (1993), Tominaga (etc.): Proceedings of the 5th Symposium on Phase Change Records, 5 (199)
3), but all of them are CD-ROM,
Compatibility with CD-R, recording / erasing performance, recording sensitivity, number of times of rewriting, number of reproductions, storage stability
It did not fully satisfy the overall performance. These drawbacks were largely due to the low erasing ratio mainly due to the composition and structure of the recording material.

Under these circumstances, development of a phase-change recording material having a large erasure ratio and high sensitivity for recording and erasing, and a high-performance and rewritable phase-change compact disc have been desired. The present inventors have found and proposed an AgInSbTe-based recording material as a new material that solves these disadvantages. A typical example is disclosed in JP-A-4-780.
No. 31, JP-A-4-123551, H.I. Iwasak
i (et al): Jpn. J. Appl. Phys
s. , 31 (1992) 461, Ide (and others): Proceedings of the 3rd Symposium on Phase Change Records, 102 (19)
91); Iwasaki (et al): Jpn.
J. Appl. Phys. , 32 (1993) 5241.
And the like. In October 1996, the Orange Book Part _III (ver 1.0) was issued as a rewritable compact disc (CD-RW) standard.

On the other hand, in recent years, digital video discs (DV
D) and DVD-RAMs are also being actively developed, and are attracting attention as major optical recording media in the early 21st century. Under such an environment, rewritable compact discs are required to have reproduction compatibility with DVDs. The recording signal of the CD-RW developed so far has a small reflectance and modulation degree around 650 nm, which is the DVD reproduction wavelength, and does not have sufficient signal characteristics. Orange Book Part _III (ver1.0) is 2
X This is a standard for CD-RW of linear velocity recording (2.4 to 2.8 m / s), but in such low linear velocity recording,
Since the recording time is long, a rewritable compact disc with higher recording speed is desired.

Recently, along with the development of CD-RW discs, the development of CD-RW drives has also been progressing, and their matching tests have been conducted. As a result of these tests, some of the drives contained a CD 6 x speed (7.2 m /
s) It was found that the error increased rapidly in the reproduction at the linear velocity described above, and it was found that there was an object in which reproduction at a high linear velocity was difficult. It was also found that some drives could not determine the optimum recording power for CD-RW discs by the γ method described in Orange Book Part _III . A phase-change optical recording medium such as a CD-RW disc has an initialization step of crystallization of a recording layer. The initialized state sensitively affects the overwrite characteristics of the optical recording medium and is largely dependent on the initialization device. However, the management of the initialization state and the traceability management of the initialization device and the disk at the time of manufacturing have not been sufficiently developed.

[0013] These CD-RW discs are CD-RO discs.
As in the case of the M disk, since the disk-shaped disk is directly handled by hand, oil and dust adhere to the front and rear surfaces of the disk. At this time, it is supposed that these are wiped off with a cloth or the like. At that time, polycarbonate, which is a standard substrate of a CD-RW disc, is damaged, and recording and reproduction cannot be performed depending on its size. As a countermeasure, it is known to provide a UV-curable resin layer (hard coat layer) on a non-groove surface (mirror surface) of an optical recording medium, which has already been used in magneto-optical disks and the like. At this time, the coating of the hard coat layer must be started between the mark on the substrate and the end of the group. When the technology is applied to a phase-change disk such as a CD-RW disk, slight coating unevenness of the hard coat layer causes initialization failure and has not been used in actual products. In particular, in the case of a CD optical disk such as a CD-RW disk, the group end is 22 mm in radius and 3 mm inside the 25 mm of the magneto-optical recording medium, and the mold end of the group and the substrate are only 2 mm close to each other. Thus, the hard coat layer could not be stably provided with good reproducibility.

[0014]

According to these disclosed technologies, it was already clear that a phase-change optical disk having extremely excellent performance can be obtained by using AgInSbTe as a recording layer, but the compatibility with CD-Rs has already been obtained. Further improvements have been desired in order to completely satisfy the above-mentioned overall performance, such as ensuring performance, and to complete a technique for manufacturing a phase-change optical disk that can form a new market.

Therefore, a first object of the present invention is to provide an easy-to-handle optical recording medium which can solve all of the problems in the above-mentioned prior art and can ensure reproduction compatibility with a DVD disk. A second object of the present invention is to provide an optimum optical recording medium for performing recording and erasing in a region where the disk rotation speed is from 1.2 m / s to 5.6 m / s. A third object of the present invention is to provide a CD-RW disc with improved matching with the drive of the CD-RW disc. A fourth object of the present invention is to provide a CD-R
An object of the present invention is to provide an optical recording medium capable of improving the stability and the yield in the manufacturing process of a W disk.

[0016]

Means for Solving the Problems The inventors of the present invention have made intensive studies on improving the optical recording medium, and as a result, have found an optical recording medium that meets the above-mentioned object. That is, according to the present invention, there is provided (1) an optical recording medium in which a first dielectric layer, a recording layer, a second dielectric layer, a metal or alloy layer, and a UV curable resin layer are laminated in this order on a disk-shaped substrate. The constituent elements of the recording layer are mainly Ag, In, Sb, Te and N and / or O, and their respective composition ratios α, β, γ, δ, ε (ε is the sum of N and O) (atom %) Is 0 <α ≦ 63 3 ≦ β ≦ 15 50 ≦ γ ≦ 65 20 ≦ δ ≦ 350 0 ≦ ε ≦ 5 α + β + γ + δ + ε = 100, and the recrystallization upper limit linear velocity of the recording layer is 2.5 to
An optical recording medium characterized by having a speed of 5.0 m / s is provided.

According to the present invention, (2) 780 ± 15
and (3) a rewritable compact disc (CD-D), wherein the reflectance at each of the reproduction wavelengths of nm and 640 ± 15 nm is 18% or more.
(1) The optical recording medium according to (1), wherein a predetermined recording power to be selected when the optimum recording power cannot be found by the γ method, which is a recording method of (RW), is provided in advance in the ATIP information of the substrate. 4) The optical recording medium according to (1), wherein the reflectance after initialization is 95% or more of the highest attainable reflectance of the optical recording medium. (5) A radius of 22 mm.
The optical recording medium according to the above (1), characterized in that the information recorded in the initialization step in the manufacturing of the optical recording medium is within the following range: (6) the information recorded in the initialization step is reflected by the modulation of the initialization power. (5) The optical recording medium according to the above (5), wherein the UV-curable resin layer having a thickness of 2 to 6 μm and a pencil hardness of H or more has a non-groove surface (mirror surface). In the rewritable compact disc (CD-RW), the innermost circumference is 22.0 mm or less, and the room temperature viscosity of the UV curable resin before forming the UV curable resin layer is 40 cps or more. The optical recording medium of the above (1), (8) 2.4 to 5.6 m
In / s CD-RW disc can be recorded at a linear velocity of, erase power / write power _{2.4~2.8m / s (P 2 e /} P 2 w) of 4.8～5.6M / s the method of recording an optical recording medium of the erase power / write power _{(P 4 e / P 4 w} ) above, wherein the greater than (1) to (7), (9) for recording the reproduction of the reproduction linear velocity increases or decreases (1) characterized in that the reproduction light power is increased / decreased accordingly.
To (7) a method for reproducing an optical recording medium.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The recrystallization upper limit linear velocity of the present invention is a novel characteristic value of the phase change optical recording medium found by the present inventors. This characteristic value is the upper limit linear velocity at which the recording layer of the phase change optical recording medium that is scanning at a predetermined linear velocity can be recrystallized after being melted by irradiation with a light beam. As a light beam, a light beam of a semiconductor laser similar to that mounted on a writer is used. The recrystallization upper limit linear velocity is obtained from the linear velocity dependence of the reflectivity of the groove or land after irradiating the groove or land of the phase-change optical recording medium scanning at a predetermined linear velocity with a light beam. The measurement result is generally as shown in FIG. At this time,
The linear velocity (3.5 m / s in FIG. 9) at which the reflectance starts to decrease sharply with the increase in the linear velocity of the light beam irradiation is defined as the upper limit linear velocity for recrystallization. The recrystallization upper limit linear velocity defined in the present invention slightly varies depending on the power of the light beam and the size of the beam, and a difference of about ± 0.5 m / s at the maximum with a pickup having a wavelength of 780 nm and an NA of about 0.5. There is.
The recrystallization linear velocity affects the performance of a phase change optical recording medium. If the recrystallization linear velocity is less than 2.5 m / s, recrystallization cannot be performed at high speed, so that the initialization process takes a long time and is not practical. In addition, in the case of recording at a CD4 × speed, it becomes amorphous when erasing. On the other hand, if the recrystallization linear velocity exceeds 5.0 m / s,
Amorphization becomes insufficient and good signal characteristics cannot be obtained.

In order to control the phase change optical recording medium to the recrystallization upper limit linear velocity of the present invention, the first dielectric layer, the recording layer,
It is desirable that the substrate temperature of the disc-shaped substrate to be laminated in the order of the second dielectric layer, the metal or alloy layer, and the UV curable resin layer be 80 ° C. or less. When the substrate temperature exceeds 80 ° C., the dielectric layer and / or the recording layer is partially crystallized and deviates from the desired upper limit of recrystallization, or the linear velocity at which the reflectance decreases as shown in FIG. 9 cannot be found. Would. Although the mechanism is not known in detail, it has been found that the film formation speed of the recording layer also determines the upper limit of the recrystallization speed. It was found that when the film forming speed was low, the recrystallization linear speed was low.
In order to obtain a desired recrystallization upper limit linear velocity, it is desirable that the film formation rate of the recording layer be 2 nm / s to 30 nm / s. At a film formation speed of 2 nm / s or less, the recrystallization linear velocity is 2 m / s or less, and at 30 nm / s or more, the recrystallization linear velocity is 5 m / s or more. Even in the composition range of the recording layer of the present invention, there is a case where a linear velocity at which the reflectance decreases as shown in FIG. 9 cannot be found. It is the irradiation of a light beam,
In some cases, the recording layer cannot be heated to a temperature higher than the melting point, or the recording layer melts, but recrystallization is too fast, so that a decrease in reflectance cannot be found in the evaluation linear velocity region.

FIG. 1 shows a typical example of the optical recording medium of the present invention. The basic configuration is such that a first dielectric layer (first protective layer) 2, a recording layer 3, a second dielectric layer (second protective layer) 4, or an alloy layer (reflection) is formed on a substrate 1 having a guide groove. (A heat radiation layer) 5 and a UV curable resin layer (overcoat layer) 6. Further, preferably, a print layer 7 is provided on the overcoat layer 6 and a hard coat layer 8 is provided on the back surface of the substrate 1.

The material of the substrate 1 is usually glass, ceramics or resin, and a resin substrate is suitable in terms of moldability and cost. Examples of resins include polycarbonate resin,
Acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polystyrene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, etc.
Polycarbonate resins and acrylic resins, which are excellent in moldability, optical properties and cost, are preferred. Further, the shape of the substrate may be a disk shape, a card shape or a sheet shape.

However, when the optical recording medium of the present invention is applied to a rewritable compact disc (CD-RW), it is desirable that the following specific conditions are given. The condition is that the width of the guide groove (groove) formed in the substrate to be used is 0.25 to 0.65 μm, preferably 0.30 to 0.55 μm, and the depth of the guide groove is 250 to
650 °, preferably 300 to 550 °. The thickness of the substrate is not particularly limited, but is preferably 1.2 mm or 0.6 mm.

The recording layer 3 is made of Ag, In, Sb, T
A material containing a quaternary phase-change recording material containing e as a main component is suitable because the recording (amorphization) sensitivity / speed, the erasing (crystallization) sensitivity / speed, and the erasing ratio are extremely good. . However, AgInSbTe has an optimum recording linear velocity depending on its composition ratio. Therefore, depending on the target recording linear velocity and linear velocity area,
It is necessary to adjust the composition ratio of AgInSbTe. As a result of the investigation so far, it has been found that the composition ratio of Te in the AgInSbTe recording layer has a high correlation with the recording linear velocity.

FIG. 2 shows that AgInS having various composition ratios is used.
4 shows the Te composition ratio dependence of the optimum recording linear velocity of a phase change optical disk manufactured using bTe as a recording layer. The layer configuration is as follows: hard coat layer 3-5 μm / substrate 1.2 mm / first dielectric layer 100 nm / recording layer AgInSbTe 25 nm / second
Dielectric layer 30 nm / metal or alloy layer (reflective heat dissipation layer) 14
0 nm / UV curable resin layer (overcoat layer) 8-10
μm. The record is NAO. = 50, λ = 780 nm
And recording was performed by EFM modulation.
Recording Pulse Strategies, Orange Book Part _III
(FIG. 3). The recording power, erase power, and bias power were 12 mW, 6 mW, and 1 mW. The optimum recording linear velocity is a linear velocity at which the number of overwriting is the largest. As shown in FIG. 2, it was found that there was a high correlation between the optimum recording linear velocity and the Te composition ratio of the recording layer, R ₂ = 0.9133. Considering this result and the experimental accuracy ± 1 at%, no matter how slow the recording linear velocity is (0 m /
s), the Te composition ratio is estimated to be 35 at% or less. CD
In order to obtain an optical recording medium corresponding to a linear velocity of 1 ×, 2 ×, 4 ×, and 8 ×, the linear velocity is required to be 1.2 to 1.4 m / s and 2.4 to 2.4 m / s.
2.8 m / s, 4.8-5.6 m / s, 9.6-11.
The Te composition ratio corresponding to 2 m / s is 33, 30, 27,
It is estimated to be about 20 at%.

On the other hand, the phase-change recording media having AgInSbTe as the recording layer affect the storage reliability depending on their composition. When Ag exceeds 6 at%, deterioration of the overwrite shelf becomes remarkable. In other words, several years after the manufacture, it becomes impossible to record a sufficient signal when recording. When In exceeds 15 at%, archival degradation is remarkable, and when less than 3 at%, recording sensitivity is lowered. As for Sb, the larger the composition ratio is, the more excellent the overwriting repetition property is.
Exceeding t% results in archival degradation. Further, addition of N and / or O is effective for reducing archival deterioration. Thereby, the amorphous mark is stabilized. Although the details of these mechanisms are not always clear, the structure changes in a rough direction due to a decrease in film density, an increase in minute defects, etc. due to the incorporation of an appropriate amount of N and O into the film. As a result, compared to the state in which N and O are not added, the order of the film is relaxed, and the storage life is improved. It is clear from the IR spectrum that N and / or O bind to Te and / or Sb.

A preferable composition ratio of N and / or O is 5 at% or less in total. If it exceeds 5 at%, the nitriding of the recording layer proceeds excessively, making crystallization difficult. As a result, insufficient initialization and a reduction in the erase ratio occur. The introduction of N and O into the recording layer is performed by adding a nitrogen gas or an oxygen gas to the argon gas during sputtering at 0 mol% or more.
It can be obtained by using a mixed gas of mol% or less. Further, by using a mixed gas of nitrogen gas and argon gas, N and O can be introduced into the recording layer. Even if the mixed gas uses a gas which is previously mixed at a desired molar ratio,
The flow rates may be adjusted so as to have a desired molar ratio when the chamber is introduced.

Further, as one of the effects of adding N and / or O, it is effective as a method for controlling the recrystallization speed of the recording layer. Specifically, the recrystallization rate can be reduced by adding N and / or O. As a result, the optimum recording speed can be controlled. This means that even if the same target is used, the optimum recording linear velocity of the phase-change optical disc can be adjusted only by controlling the (N ₂ and / or O ₂ ) / Ar gas mixture ratio during the production of the recording film.

Chemical bonding of N and / or O in the recording film
The state is one of Ag, In, Sb, and Te
It is desirable to combine with the above, but in particular,
The combined state, specifically, Te-N, Te-O, Sb-
When a chemical bond such as Te-N exists, the O / W
It is more effective in improving the number of repetitions. like that
FT-IR or XPS can be used to analyze the chemical bonding state.
Is effective. For example, in FT-IR
Means that the absorption band by Te-N is 500 to 600 cm ^-1near
Sb-Te-N has a peak at 600-65.
0cm^-1The peak appears near.

Further, other elements and impurities can be added to the recording layer material of the present invention for the purpose of further improving performance and reliability. For example, Japanese Patent Application No. Hei 4-14
Element No. 88 (B, N, C, P, Si)
And O, S, Se, Al, Ti, V, Mn, Fe, Co,
Ni, Cr, Cu, Zn, Ga, Sn, Pd, Pt, A
u is a preferred example.

In the present invention, the composition of the recording layer used was a value obtained by measuring the recording film by an emission spectrometry. In addition, X-ray microanalysis, Rutherford backscattering, Auger electron spectroscopy, X-ray fluorescence And the like. In that case, it is necessary to carry out a comparison with values obtained by emission spectroscopy. Generally, in the case of the emission spectrometry, about ± 5% of the measured value is considered to be an analysis error. Mass spectrometry such as secondary ion mass spectrometry is also effective. X-ray diffraction or electron beam diffraction is suitable for observation of a substance contained in the recording layer. That is, as a judgment of the crystal state, a crystalline state is observed when a spot-like or Debye-ring pattern is observed in the electron beam diffraction image, and an amorphous state is observed when a ring-like pattern or a halo pattern is observed. State. The crystallite diameter can be determined from the half width of the X-ray diffraction peak using Scherrer's formula. Furthermore, for the analysis of the state of chemical bonds in the recording layer, for example, oxides, nitrides, etc., analysis methods such as FT-IR and XPS are effective.

The thickness of the recording layer is 10 to 100 nm,
Preferably, the thickness is 15 to 50 nm. Further, in consideration of initial characteristics such as jitter, overwrite characteristics, and mass production efficiency, the thickness is preferably 15 to 35 nm. 1
When the thickness is less than 0 nm, the light absorption ability is remarkably reduced, and does not serve as a recording layer. On the other hand, if it is thicker than 100 nm, uniform phase change at high speed is unlikely to occur. Such a recording layer can be formed by various vapor phase epitaxy methods, for example, a vacuum evaporation method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam evaporation method, or the like. Among them, the sputtering method is excellent in mass productivity, film quality, and the like.

The material of the first protective layer 2 and the second protective layer 4 is SiO, SiO ₂ , ZnO, SnO ₂ , Al
Metal oxides such as ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂ , nitrides such as Si ₃ N ₄ , AlN, TiN, BN, ZrN, ZnS, In ₂ S ₃ , TaS _{4 and the} like Sulfide, S
Examples include carbides such as iC, TaC, B ₄ C, WC, TiC, and ZrC, and diamond-like carbon. These materials can be used alone as a protective layer, or as a mixture of each other. Further, impurities may be included as necessary. If necessary, the dielectric layer can be multi-layered. However, the first protective layer and the second protective layer need to have higher melting points than the recording layer. Such a material for the first protective layer and the second protective layer may be formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam deposition method, or the like. Can be formed. Among them, the sputtering method is excellent in mass productivity, film quality, and the like.

The thickness of the first protective layer greatly affects the reflectance at 650 nm, which is the reproduction wavelength of a DVD (digital video disk). FIG. 4 shows the dependency of the groove reflectance on the thickness of the first protective layer (refractive index 2.0) when the recording layer is 25 nm, the second protective layer (refractive index 2.0) is 30 nm, and the reflective heat dissipation layer is 140 nm. CD at playback wavelengths of 780 nm and 650 nm
-Reflectivity of 0.15 to 0.25, which is a standard for RW disks
Is required to make the first protective layer 65 to 130 nm. In order to obtain a sufficient reflectance (about 18%) even at a reproduction wavelength of 650 nm, it is desirable that the first protective layer has a thickness of 110 nm or less. Therefore, in order to obtain sufficient signal characteristics by recording / reproducing at a wavelength of 780 nm and reproducing at 650 nm, the first protective layer must be 80 nm.
It is determined that it is preferable to set the thickness to 110 nm.

The thickness of the second protective layer is 15 to 45 n
m, preferably 20 to 40 nm. 15 nm
If the thickness is smaller, the performance as a heat-resistant protective layer will not be achieved. Also, the sensitivity is reduced. On the other hand, if it is thicker than 45 nm, when used at a low linear velocity of 1.2 to 5.6 m / s, interface peeling is likely to occur, and the repetitive recording performance also deteriorates.

As the reflective heat radiation layer 5, Al, Au, A
A metal material such as g, Cu, Ta, or an alloy thereof can be used. In addition, Cr,
Ti, Si, Cu, Ag, Pd, Ta and the like are used. Such a reflective heat dissipation layer can be formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam deposition method, or the like. As the thickness of the reflective heat dissipation layer,
70 to 180 nm, preferably 100 to 160 nm.

It is desirable to have an overcoat layer 6 on the reflective heat radiation layer to prevent its oxidation. As the overcoat layer, an ultraviolet curable resin produced by spin coating is generally used. An appropriate thickness is 7 to 15 μm. When the thickness is 7 μm or less, an increase in error may be observed when a printing layer is provided on the overcoat layer.
On the other hand, if the thickness is 15 μm or more, the internal stress becomes large, which greatly affects the mechanical properties of the disk.

As the hard coat layer, an ultraviolet curable resin produced by spin coating is generally used. Its thickness is
2 to 6 μm is appropriate. If it is 2 μm or less, sufficient scratch resistance cannot be obtained. If the thickness is 6 μm or more, the internal stress becomes large, which greatly affects the mechanical properties of the disk. The hardness must be equal to or higher than H, which is a pencil hardness that does not cause significant damage even when rubbed with a cloth. It is also effective to mix a conductive material as necessary to prevent static electricity and prevent the attachment of greetings and the like. The UV-curable resin of the hard coat layer preferably has a viscosity of 40 cps or more in order to control the application position with good reproducibility and accuracy. Thereby, the radius 20 to 22 can be precisely obtained.
The edge of the hard coat is formed accurately in a narrow area of mm (FIG. 5). Further, when the marking by the initialization device is formed in the area, the accuracy is 20 to 21 m.
m, which is a stricter requirement. If the viscosity of the ultraviolet curable resin is set to 40 cps or less, the resin flows, and the positional accuracy at the beginning of coating on the inner periphery becomes insufficient. As a result, the ultraviolet curable resin is applied behind the mold of the substrate, resulting in uneven coating.

The electromagnetic waves used for initializing, recording, reproducing, and erasing the information recording medium of the present invention include a laser beam, an electron beam,
Various types such as X-rays, ultraviolet rays, visible rays, infrared rays, and microwaves can be employed. Among them, a small and compact semiconductor laser is most suitable. Recently, CD-RW drives have been developed, and a matching test with a CD-RW disc has been performed. As a result, depending on the combination of the drive and the disc, 1) When writing the lead-in and lead-out after writing the data, that is, when the pickup of the drive seeks on the recording medium, the pickup position cannot be determined. 2) The accuracy in determining the optimum recording power is poor, and in some cases, the optimum recording power cannot be determined. 3) The error increases at the high linear velocity reproduction of CD6 × speed (7.2 m / s) or more. It turns out that there is a problem such as.

As a result of studying these problems, it was found that the above 1) was caused by insufficient initialization or initialization failure. If initialization is insufficient, overwriting causes an increase in Rtop. As a result, it has been found that push-pull and radial contrast decrease, tracking becomes unstable, and accurate seek cannot be performed. Further, it has been found that if the initialization is poor, the push-pull signal and the Rf signal are disturbed, the tracking becomes unstable, and accurate seek cannot be performed.

In the above 2), the optimum recording power is set to γ
This is because when the recording power was increased when the recording power was increased, the modulation power did not saturate, so that the optimum power could not be determined. This was due to insufficient initialization or poor initialization. As a result of various studies, in order to determine the optimum recording power with high accuracy, the saturation groove reflectivity (R
It has been found necessary to achieve an initial state of 95% or more of g). In order to achieve an initialization of 95% or more of the saturation Rg, it is possible to adjust initialization conditions such as power, linear speed, and feed speed. For example, as shown in FIG.
By increasing the recording power, decreasing the feed speed, and decreasing the initializing linear velocity, 95% or more of the saturated Groove reflectance can be achieved. However, in order to manage the initialization state, it is necessary to clarify the traceability of the plurality of initialization devices and the initialized phase change recording medium. As the method, a method of marking at the time of initialization is effective. As a marking method, it is preferable to record by modulating the initialization power on the inner periphery than the groove end (FIG. 7). For example, the inner circumference (20 mm) of a phase change type recording medium corresponding to the initialization apparatus No. 1, 2, 3, 4, 5, 6
Then, marking of 1, 2, 3, 4, 5, and 6 dots is performed. It is also effective to change the inner circumference initialization start position by the initialization device. On the other hand, it is also effective to use the optimum recording power to be used in the ATIP information in case that it cannot be determined by the γ method.

The problem 3) is that the reflectivity of the disk is 1
Occurred when less than 8%. Therefore, in order to make the reflectivity of the disk 18% or more, the first protective layer must be 80 n
m or more. Or Sb of the recording layer
It is also achieved by increasing the composition ratio, decreasing the thickness of the second protective layer, and the like. Alternatively, this can be achieved by making the groove of the substrate wide and shallow. The same effect as the increase in the disc reflectivity is achieved by increasing the power of the reproduction light to 1.2 mW.
It is also achieved by increasing to 4 mW and 1.6 mW.
In consideration of variations in the drive and variations in the media reflectivity, a reproduction light of 1.2 mW or more was suitable for reproducing at CD8 × (9.6 to 11.2 m / s). Furthermore, at the time of reproduction at a high linear velocity of CD12 × or more, 1.4 mW
The above was suitable. However, with a reproduction light of 1.8 mW or more, an increase in error was observed after reproduction of 1,000,000 times or more.

From now on, it is required to improve the margin of the recording linear velocity. At least, a CD-RW disc that can record at a speed of 2 × to 4 × is required. 2
Since the cooling rate at the time of crystallization and amorphization of the phase change recording medium is different between x recording / erasing and 4x recording / erasing, control thereof is important. At 2 × speed, crystallization is easy but amorphousization becomes difficult. On the other hand, at 4.times. Speed, amorphousization is easy, but crystallization is difficult. In particular, there is a problem that Rtop becomes small due to an increase in erasing power at 4 × speed recording. Therefore,
In 4 × speed recording, a strategy with a smaller erasing power is effective. Specifically, as shown in FIG.
0.50, 0.54, 4 × at an erase power / write power (P ₂ e / P ₂ w) of 2 × (2.4 to 2.8 m / s)
It is effective to (4.8~5.6m / s) of the erase power / write power _{(P 4 e / P 4 w} ) , respectively 0.46,0.50.

[0043]

The present invention will be specifically described below with reference to examples.

Examples 1 to 11 and Comparative Examples 1 and 2 1.2 having a groove having a width of 0.5 μm and a depth of 35 nm
A first protective layer, a recording layer, a second protective layer, and a heat radiation reflecting layer shown in Table 1 were continuously formed on a polycarbonate substrate cooled to 80 ° C. or less with a thickness of 10 mm for 10 seconds by a single-wafer sputtering apparatus. Then, a hard coat and an overcoat were formed by spin coating of an ultraviolet curable resin to produce a phase change optical disk. ZnSSiO ₂ was used for the first protective layer and the second protective layer. An aluminum alloy was used for the heat radiation reflection layer. The innermost position of the hard coat is 20.5m
m. Then, the recording layer of the disk was crystallized by an initialization device having a large-diameter LD.
The initialization was performed under the condition that 95% or more of the saturated reflectance could be secured. At this time, a dot indicating the number of the initialization device was recorded at a position at an inner radius of the disk of 21 mm by power modulation of the initialization device. Next, a printing layer was formed on the overcoat layer.

The evaluation of the phase-change optical disk thus obtained was performed using an evaluator equipped with a pickup having a wavelength of 780 nm and an NA of 0.5. The recording strategy is
The erase power / write power (P ₂ e / P ₂ w) of 2 × is set to 0.50 and the erase power / write power (P ₄ e) of 4 ×
/ P ₄ w) was set to 0.46. The recording power and bias power were 13 m for both 2 × recording and 4 × recording.
W and 1 mW. The reproduction power was 1.0 mW.

Table 1 shows that C after overwriting 1000 times.
Indicates one error. In 2 × recording × 2 × reproduction, each of the examples had an error of 100 or less, and there was no practical problem.
In 4 × recording × 2 × reproduction, C1 errors tended to increase in a disk having a large composition ratio of 1n. On the other hand, in Comparative Example 1 where the overcoat thickness was small, an increase in defects due to the print layer was observed, and the C1 error increased. Also, the first
In Comparative Example 2 in which the protective layer was as thick as 150 nm, reproduction with a DVD pickup (wavelength 650 nm) could not be performed. Further, in Example 11 in which the first protective layer was as thin as 70 nm, the reflectance at a wavelength of 780 nm was 18% or less, and the C1 error in 6 × reproduction increased, making measurement impossible. However, if the reproducing power of the sample of Example 11 is 1.2 mW,
The C1 error at 6 × playback was reduced to 250 cps.

[0047]

[Table 1]

[0048]

According to the first aspect of the present invention, by specifying the thickness of each layer of the optical recording medium and the composition of the recording layer, the low linear velocity region (1.2 to 5.6 m / s) can be obtained. A phase change optical recording medium having excellent overall performance in (1) and having reproduction compatibility with a digital video disc can be obtained. 2) According to the invention of claim 2, both the CD reproduction wavelength and the DVD reproduction wavelength have a reflectance of 18% or more,
A phase-change optical recording medium capable of high-speed reproduction and having reproduction compatibility with a digital video disc is obtained. 3) According to the third aspect of the present invention, since the optimum recording power is previously stored in the ATIP information of the substrate, an optical recording medium which does not generate an error even if the optimum recording power cannot be found is obtained. 4) According to the fourth aspect of the present invention, since the initialization is sufficiently performed, the accuracy of the optimum recording power is improved, the variation in the reflectance due to overwriting is small, and even if the pickup seeks on the recording medium. , Tracking is stable,
A phase-change optical recording medium having excellent overall performance in a low linear velocity region (1.2 to 5.6 m / s) and having reproduction compatibility with a digital video disk can be obtained. 5) According to the fifth aspect of the present invention, since different marks are provided on the inner circumference of the optical disc for each initialization device, it is clear which initialization device the optical disc has been initialized, and the management of the initialization is extremely easy. As a result, a phase-change optical recording medium having excellent overall performance in a low linear velocity region (1.2 to 5.6 m / s) under controlled initialization and having reproduction compatibility with a digital video disk can be obtained. 6) According to the invention of claim 6, since a mark different for each initialization device can be formed by modulating the initialization power on the inner circumference of the optical disk, it is not necessary to largely modify the initialization device. . Therefore, the low linear velocity region (1.2 to 5.6 m /
A phase-change optical recording medium having excellent overall performance in s) and having reproduction compatibility with a digital video disk can be obtained. 7) In order to enable the formation of a hard coat layer on a CD-RW disc with a good yield, the scratch resistance is high, the overall performance in the low linear velocity region (1.2 to 5.6 m / s) is excellent, and A phase-change optical recording medium having reproduction compatibility with a digital video disk can be obtained. 8) According to the second aspect of the present invention, the recording strategy is adjusted so that the erasing power / writing power at 2 × CD linear velocity is larger than the erasing power / writing power at 4 × CD linear velocity, so that 2X to 4XCD An optical recording medium corresponding to the linear velocity can be obtained. 9) According to the ninth aspect of the present invention, an optical recording medium capable of higher-speed reproduction is obtained by controlling the reproduction light power in accordance with the reproduction linear velocity.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of an optical recording medium of the present invention.

FIG. 2 is a diagram showing a relationship between a Te composition ratio of a recording layer and an optimum recording linear velocity.

FIG. 3 is a diagram showing a recording pulse strategy based on the Orange Book Part _III .

FIG. 4 is a diagram showing a relationship between the thickness of a first protective layer and the reflectivity of the groove.

FIG. 5 is a diagram illustrating a state in which an end of a hard coat is formed in a region having a radius of 20 to 22 mm.

FIG. 6A is a diagram illustrating a relationship between initialization power and a saturation gutter reflectance (Rg), FIG. 6B is a diagram illustrating a relationship between a feed speed and Rg, and FIG. c) is the linear velocity and R
The figure showing the relationship with g.

FIG. 7 is a view for explaining recording by modulating the initialization power on the inner circumference from the end of the groove;

FIG. 8A is a diagram showing a 2 × CD recording strategy, and FIG. 8B is a diagram showing a 4 × CD recording strategy.

FIG. 9 is a diagram showing a recrystallization upper limit linear velocity.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 substrate 2 first dielectric layer (first protective layer) 3 recording layer 4 second dielectric layer (second protective layer) 5 metal or alloy layer (reflective heat dissipation layer) 6 overcoat layer 7 printing layer 8 hard coat layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Eiji Noda, Inventor 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Kyoji Hattori 1-3-6, Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kenichi Aihara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Omiya 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Yujiro Kaneko 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H111 EA03 EA04 EA12 EA23 EA41 FA11 FA21 FA23 FA30 FB09 FB12 FB17 FB21 FB25 FB29 FB30 5D029 JA01 JC11 JC20

Claims (1)

[Claims] 1. An optical recording medium comprising: a first dielectric layer, a recording layer, a second dielectric layer, a metal or alloy layer, and a UV curable resin layer laminated in this order on a disk-shaped substrate. The constituent elements are mainly Ag, In, Sb, Te and N and / or O, and their composition ratios α, β, γ, δ, ε (ε
Is the sum of N and O) (atomic%) 0 <α ≦ 63 3 ≦ β ≦ 15 50 ≦ γ ≦ 65 20 ≦ δ ≦ 350 0 ≦ ε ≦ 5 α + β + γ + δ + ε = 100, and the recrystallization of this recording layer Upper limit linear velocity is 2.5 ~
An optical recording medium having a velocity of 5.0 m / s.