JP3784819B2 - Optical recording method - Google Patents

Description

  The present invention relates to an optical recording method in which a phase change is caused in a recording layer material by irradiating a phase change optical recording medium with a light beam, information is recorded / reproduced, and rewriting is performed.

  As an optical memory medium capable of recording, reproducing and erasing information by irradiation with electromagnetic waves, especially laser beams, so-called phase change recording media using the transition between crystal-amorphous phase or crystal-crystal phase are well known. It has been. In recent years, research and development has become active due to the fact that single-beam overwriting, which is difficult with magneto-optical memory, is possible, and the optical system on the drive side is simpler. As typical examples thereof, as disclosed in US Pat. No. 3,530,441 (Patent Document 1), Ge—Te, Ge—Te—Sn, Ge—Te—S, Ge—Se—S, Ge—Se—Sb, Ge Examples include so-called chalcogen alloy materials such as As-Se, In-Te, Se-Te, and Se-As. For the purpose of improving stability and high-speed crystallization, Au (Patent Document 2: JP-A-61-219692), Sn and Au (Patent Document 3: JP-A-61-270190) are used in the Ge-Te system. , Pd (Patent Document 4: Japanese Patent Laid-Open No. 62-19490) and the like, and the composition ratio of Ge-Te-Se-Sb and Ge-Te-Sb for the purpose of improving the recording / erasing repeatability There are also proposals for materials that specify the above (Patent Document 5: Japanese Patent Laid-Open No. 62-73438, Patent Document 6: Japanese Patent Laid-Open No. 63-228433). However, none of them can satisfy all of the characteristics required for a phase change type rewritable optical memory medium. In particular, improvement of recording sensitivity and erasing sensitivity, prevention of erasure ratio reduction due to unerased residue at the time of overwriting, and extension of the life of recorded and unrecorded parts are the most important issues to be solved.

Japanese Patent Application Laid-Open No. 63-251290 (Patent Document 7) proposes a recording medium having a recording layer composed of a multi-component compound single layer having a crystal state substantially equal to or more than three. Here, the ternary or higher multi-component compound monolayer substantially includes 90 atomic% or more of a compound having a ternary or higher stoichiometric composition (for example, In ₃ SbTe ₂ ) in the recording layer. By using such a recording layer, the recording and erasing characteristics can be improved. However, it has disadvantages such as a low erasing ratio and a laser power required for erasing recording has not been sufficiently reduced.

Further, JP-A-1-277338 (Patent Document 8) describes (Sb _a Te _1-a ) _1-Y M _Y (where 0.4 ≦ a <0.7, Y ≦ 0.2, M Is at least one selected from the group consisting of Ag, Al, As, Au, Bi, Cu, Ga, Ge, In, Pb, Pt, Se, Si, Sn, and Zn. An optical recording medium having a recording layer made of is proposed. The basis of this system is Sb ₂ Te _{3. By} making Sb excessive, high-speed erasure and repetitive characteristics are improved, and addition of M promotes high-speed erasure. In addition, the erasure rate by DC light is also high. However, this document does not show the erasure rate at the time of overwriting (the unerased residue was recognized in the results of the study by the present inventors), and the recording sensitivity is insufficient.

Similarly, JP 60-177446 (Patent Document 9), the recording layer _{(In 1-X Sb X)} 1-Y M Y (0.55 ≦ X ≦ 0.80,0 ≦ Y ≦ 0.20 M is an alloy of Au, Ag, Cu, Pd, Pt, Al, Si, Ge, Ga, Sn, Te, Se, Bi), and JP-A-63-228433 (patent) In literature 10), an alloy of GeTe—Sb ₂ Te ₃ —Sb (excess) is used for the recording layer, but none of them satisfies the characteristics such as sensitivity and erasure ratio.

  In addition, JP-A-4-163939 (Patent Document 11) forms a recording thin film by adding N to a Te-Ge-Sb alloy, and JP-A-4-52188 (Patent Document 12) discloses a recording thin film. Is formed by adding a Te-Ge-Se alloy containing at least one of these components as a nitride. In Japanese Patent Laid-Open No. 4-52189, a recording thin film is formed of a Te-Ge-Se alloy. An optical recording medium formed by adsorbing N and provided with each of these recording thin films is described. However, it is impossible to obtain these optical recording media having sufficient characteristics.

  As has been seen so far, in optical recording media, especially improvement of recording sensitivity and erasing sensitivity, prevention of reduction in erasing ratio due to unerased residue during overwriting, and extension of life of recorded and unrecorded parts should be solved. It is the most important issue.

On the other hand, with the rapid spread of CDs (compact discs) in recent years, write-once type compact discs (CD-R) that can be written only once have been developed and have begun to spread in the market. However, in a CD-R, if it fails even once during writing, it cannot be corrected, and the disk becomes unusable and must be discarded. Therefore, there has been a long-awaited practical application of a rewritable compact disc that can compensate for this drawback.
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 difficulty in compatibility with CD-ROM and CD-R. Development of practical application of phase change type optical disks, which are advantageous in principle for ensuring compatibility, has been activated.

  As examples of research presentations on rewritable compact discs using phase change optical discs, Furuya (et al.): Proceedings of the 4th Symposium on Phase Change Recording Society, 70 (1992) (Non-Patent Document 1), Kanno ( Others: Proceedings of the 4th Phase Change Recording Study Group Symposium, 76 (1992) (Non-Patent Document 2), Kawanishi (Others): Proceedings of the 4th Phase Change Recording Study Group Symposium, 82 (1992) ( Non-Patent Document 3), T.W. Handa (et al): Jpn. J. et al. Appl. Phys. 32 (1993) 5226 (Non-Patent Document 4), Yoneda (Other): Symposium Lecture Collection, 5th Phase Change Recording Study Group, 9 (1993) (Non-Patent Document 5), Tominaga (Other): 5th Phase Proceedings of Proceedings of Symposium on Change Recording Study Group, 5 (1993) (Non-Patent Document 6) The total performance such as the number of times, the number of times of reproduction, storage stability, etc. was not fully satisfied. These drawbacks are largely due to the low erase ratio mainly due to the composition and structure of the recording material.

  Under these circumstances, there has been a demand for development of a phase change type recording material having a high erasure ratio and suitable for high sensitivity recording and erasing, and a high performance and rewritable phase change type compact disc. The present inventors have found and proposed an AgInSbTe-based recording material as a new material for solving these drawbacks. Representative examples thereof include JP-A-4-78031 (Patent Document 13), JP-A-4-123551 (Patent Document 14), Iwasaki (et al): Jpn. J. et al. Appl. Phys. 31 (1992) 461 (Non-Patent Document 7), Ide (Other): Proceedings of the 3rd Phase Change Recording Society Symposium, 102 (1991) (Non-Patent Document 8), H. et al. Iwasaki (et al): pn. J. et al. Appl. Phys. 32 (1993) 5241 (Non-patent Document 9) and the like.

USP 3530441 JP 61-219692 A JP 61-270190 A JP 62-19490 A JP-A-62-73438 JP 63-228433 A JP 63-251290 A JP-A-1-277338 JP-A-60-177446 JP 63-228433 A Japanese Patent Laid-Open No. 4-163839 JP-A-4-52188 JP-A-4-78031 JP-A-4-123551 Furuya (Others): Proceedings of the 4th Symposium on Phase Change Recording Workshop, 70 (1992) Kanno (others): Proceedings of the 4th Symposium on Phase Change Recording Society, 76 (1992) Kawanishi (etc.): Proceedings of the 4th Symposium on Phase Change Recording Society, 82 (1992) T.A. Handa (et al): Jpn. J. et al. Appl. Phys. 32 (1993) 5226 Yoneda (others): Proceedings of the 5th Symposium on Symposium on Phase Change Recording, 9 (1993) Tominaga (others): Proceedings of the 5th Symposium on Phase Change Recording Society, 5 (1993) H. Iwasaki (et al): Jpn. J. et al. Appl. Phys. 31 (1992) 461 Ide (others): Proceedings of the 3rd Phase Change Recording Society Symposium, l02 (1991) H. Iwasaki (et al): pn. J. et al. Appl. Phys. 32 (1993) 5241

Although it was already clear that these disclosed technologies can obtain a phase change type optical disk having extremely excellent performance, the above comprehensive performance such as ensuring compatibility with CD-R is completely satisfied, and a new Further efforts have been desired to complete a technology for producing a phase-change optical disc that can form a market.
Accordingly, an object of the present invention is to provide a method for recording on an optical recording medium that eliminates all the problems in the prior art and achieves a dramatic improvement in C / N, erasure ratio, recording sensitivity, and repeatability as compared with the prior art. It is to provide.

As a result of intensive studies on improvement of the optical recording medium, the present inventors have found a recording method on the optical recording medium that meets the above purpose.
That is, according to the present invention, (1) a first dielectric layer, a recording layer, a second dielectric layer, a metal or alloy layer are sequentially laminated on a substrate, and the constituent elements of the recording layer are Ag, In, Te, Sb, and the respective composition ratios α, β, γ, δ (atomic%) are 1 ≦ α <6
7 ≦ β ≦ 20
20 ≦ γ ≦ 35
35 ≦ δ ≦ 70
α + β + γ + δ = 100
An optical recording medium made of a phase change recording material having a width of a guide groove formed on the substrate of 0.25 to 0.65 μm and a depth of the guide groove of 250 to 650 mm is 1.2. An optical recording method characterized in that information recording is performed by irradiating light having a wavelength of 780 nm using a semiconductor laser as an irradiation light source through an objective lens with NA of 0.5 by rotating at a rotational linear velocity of ˜5.6 m / s. ,
(2) The optical recording method according to (1), wherein the recording method is a PWM (Pulse Width Modulation) method,
(3) The optical recording method according to (1), wherein a signal modulation method at the time of information recording is an EFM (Eight to Four Modulation) method or an improved modulation method thereof, and a signal at the time of laser recording is multipulsed,
Is provided.

1) According to the invention of claim 1, the C / N, the erasure ratio, the sensitivity, and the repetition characteristics can be greatly improved, and the composition of the recording layer and the shape (depth and width) of the guide groove of the transparent substrate can be achieved. By specifying, compatibility with CD-ROM and CD-R can be easily ensured, and an optimum recording method can be provided.
2) According to the invention of claim 2, it is possible to provide an optimum recording method to which the optical disk is applied, particularly a method suitable for increasing the capacity.
3) According to the invention of claim 3, it is possible to provide an optimum recording method to which the optical disc is applied, in particular, a recording method and conditions suitable for a rewritable type of a compact disc or its deformation method.

Hereinafter, the present invention will be described in more detail.
The optical recording medium used in the present invention is formed by laminating a first dielectric layer, a recording layer, a second dielectric layer, a metal or alloy layer in this order on a disc-shaped substrate. The film thickness of the layer is 500 to 2500 mm, the film thickness of the recording layer is 100 to 1000 mm (preferably 150 to 700 mm), the film thickness of the second dielectric layer is 100 to 1500 mm, and the film thickness of the metal or alloy layer. Is preferably 300 to 2000 mm. If the thickness of the recording layer is less than 100 mm, the light absorption ability is remarkably lowered, and the role as a recording layer cannot be achieved. On the other hand, if it is thicker than 1000 mm, uniform phase change is difficult to occur at high speed.

In addition, the sputtering target used for producing the optical recording medium in the present invention has Ag, In, Te, and Sb as constituent elements, and the composition ratios α, β, γ, and δ (atomic%) are 0. .5 ≦ α <8
5 ≦ β ≦ 23
17 ≦ γ ≦ 38
32 ≦ δ ≦ 73
α + β + γ + δ = 100, where α ≦ β
It is.
Preferably, there is Sb in the target and a stoichiometric composition having a chalcopyrite structure and / or a zinc blende structure, and / or an AgInTe ₂ composition close thereto, more preferably a chalcopyrite structure and / or Or the grain size d of the crystallite formed by a stoichiometric composition having a zinc blende structure and / or a composition close to that of AgInTe ₂ is
0 <d ≦ 450cm
This is a sputtering target.

In this sputtering target, (i) Ag, In, and Te as a target raw material are mixed, melted at a temperature of 550 ° C. or higher and 850 ° C. or lower, rapidly cooled and pulverized, and Sb is mixed and baked. (Ii) As a target raw material, Ag, In, Te and Sb alone are mixed, melted at a temperature of 550 ° C. or more and 850 ° C. or less, rapidly cooled and pulverized, and (iii) the above-mentioned (I) or (ii) As a process before target sintering, it can manufacture by including the heat processing process below melting | fusing point temperature.
Further, when sputtering the sputtering target, it is preferable to form a film using a gas in which nitrogen gas is mixed in an amount of 0 mol% to 10 mol% in argon gas, and the back pressure p during sputtering is 3 × 10 ⁻⁷ ≦ It is preferable to form a film by setting p ≦ 5 × 10 ⁻⁶ Torr, and it is more preferable to form a film by flowing a gas containing nitrogen at a higher concentration than that during sputtering into the sputtering chamber.

The optical recording medium used in the present invention preferably contains a nitride and / or oxide of at least one of the main constituent elements Ag, In, Te, and Sb of the recording layer. In this case, the recording layer It is preferable that at least one of the bonding states of nitrogen therein is Te-N.
A material containing a quaternary phase change recording material containing Ag, In, Te, Sb as a main component has extremely high recording (amorphization) sensitivity / speed, erasure (crystallization) sensitivity / speed, and erasure ratio. Since it is good, it is suitable as a material for the recording layer.

The recording layer composition with which good disk characteristics can be obtained is as described above. However, in order to obtain the best recording and erasing characteristics, the requirement that an AgSbTe ₂ microcrystalline phase is present at the time of non-recording and erasing is further satisfied. Better to be.

In the present invention, the composition of the recording layer used was a value obtained by measuring the recording film by an emission analysis method, but other analysis such as X-ray microanalysis, Rutherford backscattering, Auger electron spectroscopy, fluorescent X-rays, etc. The law can be considered. In that case, it is necessary to make a comparative study with the value obtained by the emission spectrometry. In general, in the case of emission analysis, about ± 5% of the measured value is considered as an analysis error.
X-ray diffraction or electron beam diffraction is suitable for observing substances contained in the recording layer. In other words, for determining the crystal state, the crystal state is observed when spot-like and Debye-ring patterns are observed in the electron diffraction pattern, and the amorphous state is observed when ring-like patterns and halo patterns are observed. And The crystallite diameter can be determined from the half width of the X-ray diffraction peak using Scherrer's equation.

  Furthermore, analysis techniques such as FT-IR and XPS are effective for analyzing chemical bonding states in the recording layer, such as oxides and nitrides.

After the thin film recording layer is installed, the target is mainly made of Sb and a stoichiometric composition having a chalcopyrite structure and / or a zinc blende structure and / or AgInTe ₂ having a composition close thereto. For example, the 1991 Fall 3rd Phase Change Recording Study Group Symposium Preliminary Proceedings p. 102 and Japan Journal of Applied Physics Vol. 32 (1993) p. As described in 5241-5247, a mixed phase state of the microcrystalline phase AgSbTe ₂ and the amorphous phase In—Sb can be obtained. By providing this mixed phase state as an unrecorded state of the recording layer, an optical recording medium having a high erasure ratio and low power and capable of repeated recording and erasing can be obtained.

The grain size of the crystallite of AgInTe ₂ having a stoichiometric composition having a chalcopyrite structure and / or a zinc blende structure and / or a composition close thereto is, for example, a main peak (X-ray) obtained by pulverizing a target and obtaining X-ray diffraction. In the case of the source Cu, λ≈1.54 mm, it can be calculated from the line width of about 24.1 °. In the calculation, it is necessary to construct the line width with a reference sample having a sufficiently large crystallite grain size.
When the grain size (d) of the crystallites of AgInTe ₂ is 450 mm or more, it is difficult to obtain a mixed phase state in which stable recording and erasure can be performed even after appropriate processing is performed after the thin film recording layer is provided. It becomes.

When the recording layer is formed using the sputtering target, the back pressure p before sputtering is preferably 3 × 10 ⁻⁷ ≦ p ≦ 5 × 10 ⁻⁶ Torr. Within this range, an appropriate discontinuous phase (barrier) can be formed in the film, and by performing an appropriate treatment after film formation, a mixed phase of microcrystalline AgSbTe ₂ and amorphous In—Sb can be obtained from an amorphous phase of AgInTe ₂ and Sb. It becomes easy to get the state. Further, by using a gas in which nitrogen gas is mixed in an amount of 0 mol% or more and 10 mol% or less in argon gas as the sputtering gas, it is most suitable for the disk use conditions such as the disk rotation linear velocity and the layer configuration according to the amount of nitrogen. A recording layer can be obtained. Further, by using a mixed gas of nitrogen gas and argon gas, the durability of repeated recording and erasure is improved. As the mixed gas, a gas mixed in advance at a desired molar ratio may be used, or the flow rate may be adjusted so that the desired molar ratio is obtained when the chamber is introduced.

Good characteristics are obtained especially when the nitrogen content in the film is 5% or less. Specific effects other than the improvement in the number of O / Ws include an improvement in the degree of modulation and an improvement in the storage life of the recording mark (amorphous mark). Details of these mechanisms are not necessarily clear, but structurally changes in a rough direction due to a decrease in the density of the film, an increase in micro defects, and the like due to mixing of an appropriate amount of nitrogen into the film.
As a result, the ordering of the film is relaxed and the transition from amorphous to crystalline is suppressed as compared with the state in which nitrogen is not added. Therefore, the stability of the amorphous mark is increased and the shelf life is improved. Further, as one of the nitrogen addition effects, it is also effective as a method for controlling the transition linear velocity. Specifically, the transition linear velocity, that is, the optimum recording linear velocity can be changed to the low linear velocity side by adding nitrogen. Even if the same target is used, the optimum recording linear velocity of the phase change optical disk can be adjusted only by controlling the N ₂ / Ar gas mixture ratio during the production of the recording film.

The chemical bonding state of nitrogen in the film is preferably bonded to any one or more of Ag, In, Te, and Sb, but particularly Te-bonded state, specifically Te—N, Sb. When a chemical bond such as -Te-N is present, the effect is increased by improving the number of repetitions of O / W. As a means for analyzing such a chemical bond state, electron spectroscopic analysis methods such as FT-IR and XPS are effective.
For example, the FT-IR, absorption bands due to Te-N has its peak around 500~600cm ^-1, Sb-Te-N is the absorption peak around 600～650Cm ^-1 appears.

  Furthermore, 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. As an example, the elements (B, N, C, P, Si) and O, S, Se, Al, Ti, V, Mn, Fe, Co, Ni, Cu described in Japanese Patent Application No. 4-1488 Zn, Ga, Sn, Pd, Pt, Au and the like are preferable examples.

  Next, the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a configuration example of the present invention. A first dielectric layer (heat resistant protective layer) 2, a recording layer 3, a second dielectric layer (heat resistant protective layer) 4, and a reflective heat radiation layer 5 are provided on the substrate 1. The heat-resistant protective layers 2 and 4 are not necessarily provided on both sides of the recording layer 3, but it is desirable to provide the heat-resistant protective layer 2 when the substrate 1 is made of a material having low heat resistance such as polycarbonate resin.

  The material of the substrate 1 is usually glass, ceramics, or resin, and a resin substrate is preferable in terms of moldability and cost. Typical examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Polycarbonate resin and acrylic resin are preferable in terms of processability and optical characteristics. Further, the substrate 1 may have 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-Erasable), it is desirable to give the following specific conditions. The condition is that the width of the guide groove (groove) formed on the substrate to be used (so-called half width) is 0.25 to 0.65 microns (μm), preferably 0.30 to 0.55 μm, The depth is 250 to 650 angstroms (Å), preferably 300 to 550 Å.
By combining this substrate condition with the recording material and the disk layer configuration described above, it is possible to provide a rewritable compact disk with excellent compatibility.
Specifically, in a compact disc, a push-pull signal after recording (PPm) is defined as an important groove signal characteristic (see CD standard). The range is required to have a PPm of 0.04 to 0.15, preferably 0.04 to 0.12, and optimally 0.04 to 0.09.
In a rewritable compact disc using phase change, it was extremely difficult to satisfy all the main recording / reproducing characteristics and to satisfy the groove signal characteristic standards. It is now possible to provide a rewritable compact disc that satisfies the requirements.

Materials for the heat-resistant protective layer include metal oxides such as SiO, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, and ZrO ₂ ; Si ₃ N ₄ , AlN, TiN Nitrides such as Zn, BN and ZrN; sulfides such as ZnS, In ₂ S ₃ and TaS ₄ ; carbides such as SiC, TaC, B ₄ C, WC, TiC and ZrC, diamond-like carbon, and mixtures thereof. . These materials can be used alone to form a protective layer, but they may be mixed with each other. Further, impurities may be included as necessary. However, the melting point of the heat-resistant protective layers 2 and 4 needs to be higher than the melting point of the recording layer 3. Such heat-resistant protective layers 2 and 4 can be formed by various vapor phase growth methods such as vacuum vapor deposition, sputtering, plasma CVD, photo CVD, ion plating, and electron beam vapor deposition.

The film thickness of the first dielectric layer (heat-resistant protective layer) 2 is 500 to 2500 mm, preferably 1200 to 2300 mm. When the thickness is less than 500 mm, the function as a heat-resistant protective layer is not achieved. Conversely, when the thickness is more than 2500 mm, the sensitivity is lowered or interface peeling is likely to occur. Moreover, a protective layer can also be multilayered as needed.
The film thickness of the second dielectric layer (heat resistant protective layer) 4 is 100 to 1500 mm, preferably 150 to 1000 mm. If it is thinner than 100 mm, it will not function as a heat-resistant protective layer. Conversely, if it is thicker than 1,500 mm, it will cause interface peeling when used in the so-called low linear velocity range of 1.2 to 5.6 m / s. It tends to occur, and the repeated greening performance also decreases. Moreover, a protective layer can also be multilayered as needed.

As the reflective heat dissipation layer 5, a metal material such as Al, Au, Ag, or Cu, or an alloy thereof can be used. It is not always necessary to form the reflective heat radiation layer 5, but it is desirable to provide it in order to release excessive heat and reduce the heat burden on the disk. Such a reflective heat dissipation layer 5 can be formed by various vapor phase growth methods such as vacuum vapor deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam vapor deposition and the like.
The thickness of the reflective heat radiation layer 5 is 300 to 2000 mm, preferably 500 to 1500 mm.

Various electromagnetic waves such as laser beam, electron beam, X-ray, ultraviolet ray, visible ray, infrared ray, microwave, etc. are used as the electromagnetic wave used for processing (initialization), recording, reproduction and erasing of the recording layer of the present invention. Is possible. In particular, as an electromagnetic wave used for recording, reproduction, and erasing, a small and compact semiconductor laser is optimal when mounted on a drive.
When recording is performed in the above, the rotational linear velocity of the disk is in the range of 1.2 to 5.6 m / s, the wavelength of the light of the semiconductor laser is 780 nm, and the NA of the objective lens is 0.5. Done.

  Hereinafter, the present invention will be described specifically by way of examples. However, these examples do not limit the present invention.

Examples 1-8, Comparative Examples 1-10
Table 1 shows the composition of a sputtering target having a stoichiometric composition having a chalcopyrite structure and / or a zincblende structure and / or a composition close to that of AgInTe ₂ , and the disk characteristics and overwrite repetition when using them. Indicates the possible number of times (O / W times). A first dielectric layer (thickness: 2000 mm) made of ZnO.SiO ₂ on a polycarbonate disk substrate (thickness: 1.2 mm) having a groove of width 0.5 μm, depth 600 mm and track pitch 1.6 μm, Recording layer (thickness 250 mm), second dielectric layer (thickness 300 mm) made of ZnS · SiO _2, reflective heat dissipation layer (thickness) made of aluminum-based alloy (Al-Si (including 1.0 wt% Si)) And a UV resin coat layer (environmental protection layer, thickness 10 μm) was provided to prepare a disc. The recording layer was sputtered at a back pressure of 9 × 10 ⁻⁷ torr, argon gas, 4 × 10 ⁻³ torr and RF power of 40 watts.

  The rotational linear velocity of the disk is measured (recording / reproducing) within the range of 1.2 to 5.6 m / s at the optimum linear velocity for each disk, the signal modulation method uses the EFM modulation method, and irradiation is performed during laser recording. Laser pulses were recorded as multipulses. The wavelength of the semiconductor laser is 780 nm, and the NA of the objective lens is 0.5. The evaluation value in the column of the disk characteristics is that the level 3 is the target composition exhibiting the best characteristics (C / N ≧ 55 dB, erasure ratio (Ers) ≦ −35 dB) and the recording layer composition produced using the target composition. Level 2 represents a target exhibiting good characteristics (55> C / N ≧ 45 dB, −35 <erase ratio (Ers) ≦ −25 dB) and a recording layer composition produced using the target. Level 1 Indicates that the disk having good characteristics was not obtained (other than the above) and the recording layer composition produced using the target.

As a result, the composition ratios α, β, γ, and δ (atomic%) of Ag, In, Te, and Sb are 0.5 ≦ α <8, 5 ≦ β ≦ 23, and 17 ≦ γ ≦ 38 in the sputtering tartat. , When 32 ≦ δ ≦ 73, and when the recording layer composition is 1 ≦ α <6, 7 ≦ β ≦ 20, 20 ≦ γ ≦ 35, and 35 ≦ δ ≦ 70, good disk properties can be obtained. You can see that
In addition, the target used in Examples 1-8 is produced through a heat treatment step before target sintering after melting and quenching and pulverizing the raw material. FIG. 2 shows the overwrite characteristics of the disk obtained in Example 5 when the linear velocity is 5 m / s.

Comparative Example 11
A disk similar to that of Example 5 was manufactured except that a target having the same composition as that of Example 5 and having no heat treatment step before target sintering was prepared. FIG. 3 shows the overwrite characteristics of this disk when the linear velocity is 5 m / s. In Comparative Example 11, both the disk characteristics and the sensitivity are inferior.

Example 9
Table 2 shows the composition of the recording film and the number of overwriting times when sputtering was performed using argon gas in which the target of Example 3 was mixed with nitrogen gas 0, 3, 6, 10, 15 mol%. When the amount of nitrogen is an appropriate amount, an improvement in the number of O / W repetitions is recognized, and when the amount exceeds 10 mol%, the number of repetitions deteriorates rapidly. Further, in the sample mixed with nitrogen, the presence of In oxide, In nitride, Te nitride or the like was observed in the film. In particular, when Te—N or Sb—Te—N bonds exist in the recording film, it was confirmed that the effect was great by improving the number of O / W repetitions. However, the nitride is not particularly limited. FIG. 5 shows an analysis of a sample obtained by forming a recording layer (N ₂ / Ar + N 2) 3 mol% on a Si wafer substrate to a thickness of 1000 mm by the FT-IR transmission method, and shows similar data to a 0 mol% sample. Difference spectrum.

Details of the measurement method and measurement conditions are as follows.
(Measuring method)
Apparatus: IFS-113V (FT-IR manufactured by Bruker)
Light source: SiC
Detector: MCT (HgCdTe)
Beam splitter: Ge / KBr (4000-600cm ^-1 )
3.5μm Mylar film (700-100cm ^-1 )
12μm Mylar film (250-60cm ^-1 )
(Measurement condition)
Resolution = 4cm ^-1
Integration count = 2048 times (4000-600cm ^-1 )
512 times (700-60cm ^-1 )
Apodization = box car zero filling = double (4000-600cm ^-1 )
4 times (700-60cm ^-1 )
Reference sample = Si
Measurement method = Transmission method Phase correction = Merts method

＊１）ジャッター値が最小となる記録パワー、１５ｍＷ以下が望ましい（以下同じ）。
＊２）ジャッター値が急増する点、１０００回以上が望ましい（以下同じ）。

* 1) The recording power that minimizes the jitter value is preferably 15 mW or less (the same applies hereinafter).
* 2) A point where the jitter value increases rapidly, preferably 1000 times or more (the same shall apply hereinafter).

Comparative Example 12
The grain size of the crystallites of AgInTe ₂ contained in the targets of Examples 1 to 8 is 450 mm or less. A disk having the same composition target as in Example 2 and a crystallite particle size of 500 mm was manufactured, and a disk similar to that in Example 2 was manufactured. FIG. 4 shows the overwrite characteristics of the disk of Comparative Example 18 when the linear velocity is 2 m / s. In Comparative Example 12, the C / N and erasure ratio were inferior to those in Example 2.

Comparative Examples 13 and 14
In the targets of Examples 1 to 8, the material mixing and melting temperature at the time of producing the target of Ag, In, Te, and Sb as raw materials is 550 ° C. or higher and 850 ° C. or lower. Discs having the same composition as in Example 2 and having a raw material melting temperature of 500 ° C. (Comparative Example 13) and 900 ° C. (Comparative Example 14) were produced. With the disc of Comparative Example 13, good recording and erasing could hardly be performed. Further, Comparative Example 14 was slightly inferior in characteristics to Example 2.

Example 10
Except that the width and depth of the guide groove (groove) were changed, a disk having the same configuration as that of Example 2 was produced by the same method, and the groove signal characteristics were evaluated. The result is shown in FIG. As can be seen from FIG. 6, when the width of the guide groove formed on the substrate is 0.25 to 0.65 μm and the depth of the guide groove is 250 to 650 mm, good groove signal characteristics are exhibited.

Example 11
Except for changing the film thickness of each layer, a disk having the same configuration as in Example 2 was produced by the same method, and the recording sensitivity and the number of overwriting repetitions were evaluated. The results are shown in Table 3. From Table 3, the film thickness of the first dielectric layer is 500 to 2500 mm, the film thickness of the recording layer is 100 to 1000 mm, the film thickness of the second dielectric layer is 100 to 1500 mm, and the film thickness of the alloy layer is 300 to 300 mm. It can be seen that when it is 2000 mm, it has high recording sensitivity and an excellent number of rewrites.

（注）実施例１１の１〜６は第１誘電体層の膜厚効果、実施例１１の７〜１３は記録層の膜厚効果、実施例１１の１４〜２１は第２誘電体層の膜厚効果、実施例１１の２２〜２７は反射放熱層の膜厚効果を表わす。
（注）判定で○は良好、×は不良を表わす。

(Note) 1 to 6 of Example 11 is the film thickness effect of the first dielectric layer, 7 to 13 of Example 11 are the film thickness effect of the recording layer, and 14 to 21 of Example 11 are the film thickness effect of the second dielectric layer. The film thickness effect, 22-27 of Example 11, represents the film thickness effect of the reflective heat dissipation layer.
(Note) In the judgment, ○ indicates good and × indicates poor.

  According to the optical recording medium of the present invention, the compatibility between CD and CD-R is easy to take, so that the use is expected to expand.

FIG. 1 is a configuration diagram of an example of the optical recording medium of the present invention. FIG. 2 is a diagram showing the performance of an optical recording medium manufactured using a target that has been heat-treated before sintering when the target material is manufactured. FIG. 3 is a diagram showing the performance of an optical recording medium using a target that has not been heat-treated when the target material is manufactured. FIG. 4 is a diagram showing the performance of an optical recording medium manufactured with a target having the same composition and a crystal pore diameter of 500 mm. FIG. 5 shows an FT-IR spectrum of an Ag—In—Sb—Te—N film. FIG. 6 is a diagram showing the relationship between the groove width and depth and the push-pull signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 First dielectric layer 3 Recording layer 4 Second dielectric layer 5 Metal or alloy layer

Claims (3)

A first dielectric layer, a recording layer, a second dielectric layer, a metal or alloy layer are laminated in this order on a substrate, and the constituent elements of the recording layer are Ag, In, Te, Sb, and the respective composition ratios α, β, γ, δ (atomic%) is 1 ≦ α <6
7 ≦ β ≦ 20
20 ≦ γ ≦ 35
35 ≦ δ ≦ 70
α + β + γ + δ = 100
An optical recording medium made of a phase change recording material having a width of a guide groove formed on the substrate of 0.25 to 0.65 μm and a depth of the guide groove of 250 to 650 mm is 1.2. An optical recording method characterized in that information recording is performed by irradiating light having a wavelength of 780 nm using a semiconductor laser as an irradiation light source through an objective lens with NA of 0.5 by rotating at a rotational linear velocity of ˜5.6 m / s. .   2. The optical recording method according to claim 1, wherein the recording method is a PWM (Pulse Width Modulation) method.   2. The optical recording method according to claim 1, wherein a signal modulation method at the time of information recording is an EFM (Eight to Four Modulation) method or an improved modulation method thereof, and a signal at the time of laser recording is multipulsed.

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