JP2004017342A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GeSbTe optical information recording medium which can endure against a high output regenerated light. <P>SOLUTION: The optical information recording medium 10 is constituted of at least a reflective layer 2, a first protective layer 3, phase change type optical recording layer 4 and a second protective layer 5 sequentially laminated in this order on a substrate 1 so that the phase change type optical recording layer 4 is phase changed by irradiating the second protective layer 5 side with a light to thereby record and erase information. The phase change type optical recording layer is formed of VwGexSbyTez, wherein 0.5≤w≤23, 4≤x≤14.5, 2.1≤y/z≤4, w+x+y+x=100 (atomic ratio) are satisfied. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical information recording medium (optical disk) on which information is recorded and erased by changing the arrangement of atoms constituting a recording layer by light irradiation.
[0002]
[Prior art]
As one of optical memory media capable of recording, reproducing, and erasing information by laser beam irradiation, a so-called phase change type utilizing a transition between crystal and amorphous or between two crystal phases of crystal 1 and crystal 2. Optical recording media are well known.
[0003]
As a recording layer material used in the phase change recording method, a chalcogen-based alloy thin film is often used. Among them, GeSbTe-based and AgInSbTe-based alloy thin films have been put to practical use as rewritable optical disks.
[0004]
The recording principle is as follows. The recording layer immediately after film formation is in an amorphous state and has a low reflectance. First, the recording layer is heated by irradiating a laser beam to bring the entire surface of the disk into a crystalline state having a high reflectance. That is, initialization is performed. Usually, this initialization is performed by irradiating a rotating medium with a laser beam focused to several tens to 100 μm.
[0005]
The initialized optical disk is locally irradiated with a laser beam to melt and quench the recording layer to change its phase to an amorphous state. The optical properties (reflectance, transmittance, complex refractive index, etc.) of the recording layer change with the phase change, and information is recorded.
[0006]
Reproduction is performed by irradiating a laser beam weaker than at the time of recording and detecting a reflectance difference or a phase difference between the crystal and the amorphous. In rewriting, a recording peak power superimposed on a low-energy erasing power that causes crystallization is applied to the recording layer, thereby overwriting the already recorded recording mark without going through the erasing process.
[0007]
It is known that in the GeSbTe-based material other than the material that is put into practical use, the crystalline-non-crystalline state transitions even with the eutectic composition of Sb and Te.
[0008]
By the way, as a known material including a composition range in which a third element, particularly Ge is added to Sb70 and Te30, JP-A-1-111585, JP-A-1-251342, JP-A-1-303644, and the like can be mentioned. be able to.
[0009]
However, according to the contents of such known publications, even if there is a portion that partially overlaps with the present invention as a composition range, as described later, the specific configuration is different. According to the technical content, it is impossible to obtain an optical information recording medium of this kind which has sufficient recording / reproducing characteristics, contrast, and high durability of reproducing light intended by the present invention.
[0010]
On the other hand, an optical disk recording method using a phase change material has been performed by using a red laser beam having a wavelength of about 650 nm used in DVD-ROM or a laser beam having a longer wavelength than that. However, in recent years, semiconductor lasers emitting at a wavelength of about 400 nm have appeared on the market. Further, the objective lens has a higher numerical aperture (NA), and can narrow the beam.
[0011]
This is because if a laser having a shorter wavelength and an objective lens having a higher NA can be used in combination, the beam spot diameter becomes smaller and the recording density of the optical disk can be increased accordingly. Therefore, various companies are studying an optical disk system using a blue laser.
[0012]
[Problems to be solved by the invention]
The present inventors have researched and developed an optical disk using a blue laser system, which has greatly improved performance as compared with a conventional red laser system, and realizes high-density recording. Such an optical disk is required to be compatible with a blue laser having a short wavelength, to be able to record sufficiently with a short pulse width, and to be able to rewrite.
[0013]
Experiments have confirmed that among conventional materials, GeSbTe-based materials near the eutectic composition can be recorded and reproduced to some extent with a blue laser system. Further, in order to improve the recording / reproducing characteristics, it is possible to control the crystallization speed by adjusting the balance between the amounts of Sb and Te among the constituent elements of the GeSbTe-based material, thereby changing the corresponding linear speed during recording. Has been confirmed by experiments.
[0014]
Further, the amount of Ge greatly affects the stability of the recording material. If the amount is in an appropriate range, the reproduction durability with respect to a blue laser having a small beam diameter and a high energy density can be improved.
[0015]
However, in order to perform higher-density recording, it is necessary to further improve the recording / reproducing characteristics, that is, increase the reproducing power and reduce the jitter. However, in an optical disc using a GeSbTe-based material as a recording material, In this regard, there is a limit in characteristics.
[0016]
Therefore, the present inventors have conducted intensive research and development, and as a result, in a GeSbTe-based material as a phase-change optical recording layer, the balance between Sb and Te is set within a predetermined range, and the amount of Ge is specified. Furthermore, by adding an appropriate amount of vanadium (V) to these GeSbTe-based materials, it is possible to obtain a reproduction light exhibiting excellent recording / reproduction characteristics in a system using a blue laser as compared with a recording material using only GeSbTe. An optical disk showing strong durability has been obtained, and an object of the present invention is to provide such an optical disk.
[0017]
[Means for Solving the Problems]
The present invention has been made to achieve the above object, and at least a reflective layer 2, a first protective layer 3, a phase-change optical recording layer 4, and a second protective layer 5 are laminated on a substrate 1 in this order. An optical information recording medium 10 for recording and erasing information by changing the phase of the phase-change optical recording layer 4 by irradiating light from the second protective layer 5 side,
The phase change type optical recording layer is composed of VwGexSbyTez,
0.5 ≦ w ≦ 2
3.4 ≦ x ≦ 14.5
2.1 ≦ y / z ≦ 4
w + x + y + z = 100 (atomic ratio)
It is characterized by being.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that since the following examples are preferred specific examples of the present invention, various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Are not limited to these embodiments unless otherwise described.
[0019]
First, to better understand the optical disk according to the present embodiment, the background will be described. As can be understood from the above-mentioned publicly known publications and the like, a considerably high output laser is required for initialization. In a high-power laser, the beam diameter is narrowed, so even with a small laser power, the density of the beam light increases.However, initialization by scanning a beam diameter of several microns takes a very long time. It was what was needed.
[0020]
Therefore, GeTe and Ge, which are not eutectic systems that can be initialized with lower power, are used. ₂ Sb ₃ A GeSbTe-based material made by combining the above was developed, and the current DVD-RAM-based product was born. AgInSbTe-based material was developed a little later than this material, and CD-RW and DVD-RW were born.
[0021]
This AgInSbTe-based material requires stronger laser power than GeSbTe used in RAM. Around this time, the wavelength of the laser has been shortened and the output has been increased, and an initialization device equipped with a high-power laser has appeared.
[0022]
With the advent of such an initialization device equipped with a high-power laser, eutectic GeSbTe materials, which had been difficult to initialize in the past, have been developed and have been developed to date.
[0023]
Hereinafter, a preferred embodiment of the optical disc according to the present invention will be described with reference to FIG. Note that the present invention is not limited to the structures and materials used in the following examples as described above.
[0024]
FIG. 1 is a cross-sectional view showing an example of a basic configuration of an optical disc according to the present embodiment, FIG. 2 is a diagram showing a strategy pattern at the time of recording, and FIG. FIGS. 4 to 10 are cross-sectional views showing other examples, FIGS. 4 to 10 are diagrams showing read light durability and initial jitter with respect to a recording layer composition in which V is added to the recording layer, and FIG. FIG. 12 is an explanatory diagram showing the amount of Ge in each sample, FIG. 12 is an explanatory diagram showing the same Sb / Te ratio, and FIG. 13 is an explanatory diagram showing the recording power and strategy as the recording conditions according to the present embodiment. FIG. 14 is a comparative explanatory diagram immediately after the start of still and 5 minutes after the reproduction power is changed.
[0025]
As shown in FIG. 1, an optical disk 10 according to the present embodiment has a reflective layer 2 on a substrate 1, a first protective layer 3 on the reflective layer 2, a recording layer 4 on the first protective layer 3, A second protective layer 5 is provided on the recording layer 4, and a cover sheet 7 is provided on the second protective layer 5 via an adhesive layer 6. The optical disc 10 according to the present embodiment has a recording layer 3 on a substrate 1, and the arrangement of atoms constituting the recording layer 3 changes by irradiation of light from a side different from the substrate 1, and information is recorded. An optical disk on which recording and erasing are performed is a premise.
[0026]
Here, the laser beam (light) enters from the cover sheet 7 side, but the laser beam may enter from the substrate 1 side without providing the cover sheet 7. In addition, when sufficient reflectivity can be obtained, a configuration in which the above-described reflective layer 2 is not provided may be adopted.
[0027]
FIG. 3 is a cross-sectional view of another embodiment in which a laser beam is incident from the substrate 1 side. In an optical disc 20 according to another embodiment, a second protective layer 5 is 5, a recording layer 4, a first protective layer 3 on the recording layer 4, a reflective layer 2 on the first protective layer 3, and a protective coat 8 on the reflective layer 2. is there.
[0028]
The substrate 1 used for the optical discs 10 and 20 in this embodiment and the like may be any of glass, plastic, and a photo-curable resin provided on glass. Are preferable, and among them, a polycarbonate resin is preferable.
[0029]
Although the thickness of the recording layer 4 is not particularly limited, it is 3 nm to 100 nm. In particular, it is preferable that the thickness be 3 nm or more and 30 nm or less since the recording and erasing sensitivity is high and the recording and erasing can be performed many times.
[0030]
By arranging the first and second protective layers 3 and 5 serving as dielectric layers in this manner, the substrate 1, the recording layer 4 and the like are deformed by laser beam irradiation heat at the time of recording, and recording is performed. There is an effect of protecting the substrate 1 and the recording layer 4 from heat, such as preventing deterioration of characteristics, and an effect of improving a signal contrast at the time of reproduction by an optical interference effect.
[0031]
Further, there is also an effect of promoting crystallization of the recording layer 4 and improving the erasing rate. As the first and second protective layers 3 and 5, ZnS-SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ And inorganic thin films.
[0032]
In particular, thin films of metals such as Si, Ge, Al, Ti, Zr, and Ta, or oxides of semiconductors, thin films of metals such as Si, Ge, and Al, or nitrides of semiconductors, Ti, Zr, Hf, and Si Metal or semiconductor carbide thin film, ZnS, In ₂ S ₃ , TaS ₄ , GeS ₂ And the like, and a thin film of a sulfide of a metal or a semiconductor, and a film of a mixture of two or more of these compounds are preferable because of high heat resistance and chemical stability.
[0033]
Further, it is preferable that the first and second protective layers 3 and 5 constituting the protective layer to the recording layer 4 have no diffusion of atoms. These oxides, sulfides, nitrides and carbides do not necessarily have to have a stoichiometric composition, and it is effective to control the composition for controlling the refractive index and the like, or to use a mixture thereof.
[0034]
In addition, MgF ₂ The first and second protective layers 3 and 5 formed by mixing a fluoride such as the above are also preferable because the residual stress of the film (layer) is small. Especially ZnS and SiO ₂ Is preferable because the recording sensitivity, C / N, erasure rate, and the like hardly deteriorate even when recording and erasing are repeated. The thickness of the first and second protective layers 3, 5 is about 5 nm to 200 nm.
[0035]
The thickness of the first protective layer 3 is preferably 5 nm to 30 nm because recording characteristics such as C / N and erasing rate and stable rewriting can be performed many times. The thickness of the second protective layer 5 is preferably 30 nm to 200 nm because the second protective layer 5 does not easily peel off from the recording layer 4 or the adhesive layer 6 and hardly causes defects such as cracks. The first and second protective layers 3 and 5 may be made of different compounds instead of the same.
[0036]
Examples of the material of the reflective layer 2 include light-reflective metals such as Al, Au, and Ag, alloys containing these as main components and containing additional elements such as Ti, Cr, Pd, and Cu, and Al, Au, and Ag. And a metal compound such as a metal nitride such as Al or Si, a metal oxide, or a metal chalcogenide mixed with a metal such as Al. Metals such as Al, Au, and Ag, and alloys containing these as main components are preferable because of their high light reflectivity and high thermal conductivity. The thickness of the reflective layer 5 is generally about 5 nm or more and 300 nm or less.
[0037]
It is preferable to use a laser beam (laser beam) as a light source for recording on the optical discs 10 and 20 of the present embodiment, and it is mainly a laser beam having a wavelength in the range of 830 nm in the near infrared region to 300 nm in the ultraviolet region. It is also possible to use a light source in which the primary light is shortened in wavelength using a secondary harmonic generation element (SHG element).
[0038]
An embodiment of the optical disc 10 according to the present invention will be described below. Before that, a strategy at the time of recording will be described with reference to FIG. The recording on the optical disk 10 according to the present invention is performed by irradiating the recording layer 4 in a crystalline state with a laser light pulse or the like, heating the crystal layer 4 and then rapidly cooling the recording layer 4 to form an amorphous recording mark.
[0039]
Practically, the recording peak power (P1) superimposed on the low-energy erasing power (P2) causing crystallization is applied to the recording layer 4 so that the recording marks already recorded without going through the erasing process are obtained. Overwrite on top. The recording laser pulse at this time is divided into a plurality of pulses shorter than the recording mark length.
[0040]
Specific examples are shown below, but as described above, the present invention is not limited to these examples. In the present embodiment, recording (one-beam overwriting) is performed using an optical disk drive tester (LM330A) manufactured by Shibasoku Corporation equipped with a laser diode having a wavelength of 405 nm and an optical lens (objective lens) having a numerical aperture of NA = 0.85. Was. As the initialization device, an initializer (LK201A) manufactured by Shibasoku was used.
[0041]
Examples will be described below. As described above, it has been experimentally confirmed that a GeSbTe-based material near the eutectic composition can be recorded and reproduced to some extent by a system using a blue laser. Has been confirmed. Further, in order to improve the recording / reproducing characteristics, it is possible to control the crystallization speed by adjusting the balance between the amounts of Sb and Te among the constituent elements of the GeSbTe-based material, thereby changing the corresponding linear speed during recording. Have also been confirmed in experiments.
[0042]
Also, the amount of Ge greatly affects the stability of the recording material, and if the amount is in an appropriate range, it is possible to improve the reproduction durability against a blue laser having a small beam diameter and a high energy density. It has been confirmed in.
[0043]
Therefore, in the description of the comparative example of FIG. 15 described below, as a result of performing an experiment on 18 samples of GeSbTe described above, it was found that the composition amount (atomic ratio) of GeSbTe and the Sb / Te ratio were within a predetermined range. Corresponds to a next-generation blue laser, and can be sufficiently recorded even with a short pulse width, and is considered to be in a rewritable range. Reproduction degradation is 0.2 dB or less, and initial jitter is 9% or less. Twelve samples satisfying the range were extracted.
[0044]
However, these 12 samples correspond to the next-generation blue laser as described above, and can be sufficiently recorded even with a short pulse width, and even if they can be rewritten, the next-generation blue laser is used. However, in order to perform higher-density recording by using the method described above, it has been unsatisfactory in terms of increasing the reproduction power and reducing the jitter as described above. That is, an optical disk using a GeSbTe-based material for a phase-change optical recording layer having a conventional configuration has a durable reproduction power output of at most about 0.36 mW, so that contrast cannot be obtained, and therefore, C / N is low. It became worse and did not lead to a reduction in jitter, but required further improvement in recording and reproducing characteristics.
[0045]
The present invention solves this problem by adding a suitable amount of vanadium (V) to a phase-change optical recording layer based on a GeSbTe-based material as described above. As a result, an optical disk exhibiting excellent recording / reproducing characteristics in a system using a blue laser and exhibiting strong durability against reproducing light was able to be obtained, and this point will be specifically described below.
[0046]
In the following description of the present embodiment, twelve samples that correspond to the above-described next-generation blue laser, are sufficiently recordable even with a short pulse width, and are in a rewritable range are used. As a base, seven more are selected from the twelve samples, and V is added to the selected seven samples, so that the conventional configuration cannot achieve any effect, and the configuration of the present embodiment can provide a unique effect for the first time. This point will be described.
[0047]
First, sampleNo. 2 will be described with reference to FIG. In FIG. 4, reference numeral 2 denotes sampleNo. 2-v1 to 2-v6 indicate sampleNo. 2 shows the state of the durable reproduction power and the average initial jitter when the amount of V is changed.
[0048]
(Example 1)
First, on a polycarbonate substrate 1 having a diameter of 120 mm, an Ag alloy is used as the reflective layer 2, and ZnS—SiO is used as the first protective layer 3. ₂ VGeSbTe as the recording layer 4 and ZnS-SiO as the second protective layer 5 ₂ Were sequentially formed by a sputtering method. Thereafter, a UV curing resin was used as the adhesive layer 6, and the cover sheet 7 was bonded thereon. At this time, the thickness of each layer was 50 nm for the reflective layer 2, 10 nm for the first protective layer 3, 18 nm for the recording layer 4, and 50 nm for the second protective layer 5.
[0049]
The composition of the recording layer 4 was V 0.5%, Ge 3.4%, Sb 72.7%, and Te 23.4% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, the initialization conditions were fixed at a linear velocity of 4 m / s and a feed pitch of 40 μm with an initializer having a laser beam spot diameter of 120 μm, and initialization was performed with a laser output of 570 mW.
[0050]
Here, the laser output of the initialization is the same as that of a comparative example using GeSbTe described later, but is a result of optimization to VGeSbTe. Thereafter, the 1-7 modulated information signal is 5.28 m / s, and as shown in FIG. 2, 1T = 15.1 nsec is set as a strategy, and sampleNo. As shown in FIG. 2, P1 = 5.2 mW, P2 = 2.7 mW, P3 = 0.1 mW, P4 = 0.1 mW, and the strategy (T) was T1 = 0.4T, T2 = 0.4T, T3 = 0. Recording was performed on a groove at 6T and T4 = 0.6T, and sliced at the center of the amplitude of the reproduced signal, and clock to data jitter was measured.
[0051]
Note that the sampleNo. 2 to sampleNo. Sample No. 17 of each embodiment including this embodiment and the like. 2 to sampleNo. 17 corresponds to FIG.
[0052]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The initial jitter after the initial recording was 7.2% at the beginning of the recording mark and 7.0% at the rear end of the recording mark, and good recording was performed (see 2-v1 in FIG. 4). The initial jitter value is the jitter of the optical disk itself, and the next-generation blue laser standard specifies that the jitter value including the device (hardware) side is 10% or less. Therefore, it is preferable that the initial jitter value of at least the optical disc alone be suppressed to about 7%.
[0053]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was changed from 0.30 mW to 0.40 mW in steps of 0.01 mW, and the C / N was measured immediately after the start of still reproduction and after 5 minutes had elapsed. Here, the maximum value of the reproduction power in which the C / N difference immediately after the start of the still reproduction and after 5 minutes has fallen within the range of 0.2 dB or less was defined as the durable reproduction power. C / N has a measurement error of about 0.2 dB including a spectrum analyzer.
[0054]
When there is deterioration due to the reproduction light, the change in C / N can be almost confirmed in about one minute of still reproduction. After a lapse of 5 minutes, the C / N deterioration amount certainly exceeds 0.2 dB, and it can be sufficiently confirmed that the deterioration has occurred. Therefore, the criterion for judging the deterioration due to the reproduction light is a C / N difference of 0.2 dB.
[0055]
According to the measurement, the C / N immediately after the start of the optical disc of Example 1 was 50.3 dB, and the C / N after 5 minutes had passed was 50.3 dB. For the measurement of C / N, a spectrum analyzer was used, and 16 data were taken as an average value.
[0056]
As described above, in the optical disk of the first embodiment, the C / N immediately after the start of still reproduction and the C / N after 5 minutes have not changed at all, that is, the optical disk has stable performance without reproduction deterioration. You can see that.
[0057]
Here, the reproduction light will be described. Of the marks to be recorded, the worst jitter is the 2T mark, which is the shortest mark that is difficult to record. This is because the laser irradiation time for recording, that is, the mark formation time is the shortest, and it takes time to form the mark. That is, if the jitter of the 2T mark can be suppressed to, for example, 9% or less, all the marks can be surely suppressed to 9% or less, and thus the total jitter can be greatly reduced. It has been experimentally found that the C / N required for the jitter of 2T alone to be 9% is 51.0 dB.
[0058]
Here, when GeSbTe containing no V is used as the phase change recording layer, the C / N becomes 50.0 dB when reproduced at a power of 0.3 mW that would not deteriorate. Here, it has been experimentally confirmed that even if the reproduction light is raised to the maximum endurance power of 0.36 mW, it remains at most 50.0 dB and does not reach 51.0 dB.
[0059]
On the other hand, in the case of the present embodiment in which GeSbTe containing V is used as the phase change recording layer, the durable reproduction power is 0.38 mW to 0.40 mW. This is because V is a high melting point element and is very stable thermally, does not react with Ge, Sb, and Te constituting the phase change recording layer, and also has It is a stable substance that does not react with the material to be formed, and by adding an appropriate amount, this V acts as an anchor in the recording film, and the mark edge becomes sharper at the time of forming a recording mark, thereby reducing jitter. As described above, it is considered that the material having high melting point has good thermal durability, and thus can withstand even higher power to the reproduction light.
[0060]
When reproduction is performed at a power of 0.30 mW that will not deteriorate, the C / N is 50.5 dB at the maximum, but by increasing the reproduction power to 0.38 mW, the C / N reaches 51.0 dB. It is something that can be done. That is, even when the 2T mark, which is the shortest mark that is difficult to record, is formed, the jitter of 2T alone can be suppressed to 9%.
[0061]
Incidentally, when the reproducing power was increased to 0.38 mW, the C / N immediately after the start of still reproduction was 51.2 dB, and the C / N after 5 minutes had elapsed was 51.2 dB. In other words, the C / N condition necessary for the jitter of 2T alone to become 9% was sufficiently satisfied. (See Fig. 14)
[0062]
Next, the experiment was performed by setting the ratio of Ge and Sb / Te to the same value, slightly changing the amounts of Sb and Te, and setting the amount of V to 1.0 to 2-v2. An experimental result exceeding 0.32-v1 was obtained, with a reproduction power of 0.38 and an average initial jitter of 6.95. In other words, it can be seen that the optical disk in this example is an optical disk that sufficiently satisfies the next-generation standard as the reproduction power output and the initial jitter.
[0063]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 1.5 to 2-v3. As a result, an experimental result of 0.38 similar to the above and 6.93 as the average initial jitter was obtained, which exceeded the above-mentioned 2-v2. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0064]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 2.0 to 2-v4. Sufficient experimental results were obtained with a reproduction power of 0.38 as described above and an average initial jitter of 6.97. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0065]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 2.5 to 2-v5. The reproduction power was 0.38 as above, the average initial jitter was 8.00, and the sample No. The experimental result was worse than 2. That is, it can be seen that the optical disk in this example is an optical disk that does not satisfy the next-generation standard as the reproduction power output and the initial jitter.
[0066]
Next, the experiment was performed by setting the ratio of Ge and Sb / Te to be the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 3.0 to 2-v6. The reproduction power was 0.38, similar to the above, and the average initial jitter was 9.12, which was an even worse experimental result than the 2-v5. That is, it can be seen that the optical disk in this example is also an optical disk that does not satisfy the next-generation standard in the reproduction power output and the initial jitter.
[0067]
Here, since an error of about 0.2 dB occurs as a measurement error, the C / N change immediately after the start of reproduction is considered to be good if the change in C / N is 0.2 dB or less. That is, the C / N immediately after the start of the still reproduction and the C / N after 5 minutes have not substantially changed. Here, when the strength of the reproduction power that can withstand the C / N deterioration of 0.2 dB or less after elapse of 5 minutes was examined, it was possible to withstand up to 0.38 mW. From this, it can be understood that the optical disc 10 according to the first embodiment has high durability against the reproduction light and satisfies the next-generation standard.
[0068]
It can be understood from 2-v1 to 2-v6 that the amount of V in the range of 0.5 to 2.0 is favorable as the initial jitter.
[0069]
Next, sampleNo. 4 will be described with reference to FIG. In FIG. 5, reference numeral 4 denotes sampleNo. 4 and 4-v1 to 4-v6 indicate the sampleNo. 4 shows the state of the durable reproduction power and the average initial jitter when the amount of V is changed.
[0070]
(Example 2)
A reflective layer 2, a first protective layer 3, a recording layer 4, and a second protective layer 5 were sequentially formed on a polycarbonate substrate 1 having a diameter of 120 mm by the same method as in Example 1 described above by a sputtering method. Thereafter, a UV curing resin was used as the adhesive layer 6, and the cover sheet 7 was bonded thereon. At this time, the thickness of each layer was 50 nm for the reflective layer 2, 10 nm for the first protective layer 3, 18 nm for the recording layer 4, and 50 nm for the second protective layer 5.
[0071]
The composition of the recording layer 4 was V0.5%, Ge4.3%, Sb64.5%, and Te30.7% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, initialization was performed with a laser beam spot diameter of 120 μm, an initialization condition of a linear velocity of 4 m / s, a feed pitch of 40 μm, and a laser output of 570 mW.
[0072]
Here, the laser output of the initialization is the same as that of a comparative example using GeSbTe described later, but is a result of optimization to VGeSbTe. Thereafter, the 1-7 modulated information signal is 5.28 m / s, and as shown in FIG. 2, 1T = 15.1 nsec is set as a strategy, and sampleNo. As shown in FIG. 4, P1 = 5.2 mW, P2 = 2.4 mW, P3 = 0.1 mW, P4 = 0.1 mW, and the strategy T was T1 = 0.4T, T2 = 0.4T, T3 = 0.6T. , T4 = 0.6T, and sliced at the center of the amplitude of the reproduced signal to measure clock to data jitter.
[0073]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The jitter after the initial recording was 7.34% at the beginning of the recording mark and 7.30% at the rear end of the recording mark, indicating that good recording was possible. (Refer to 4-v1 in FIG. 5)
[0074]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was changed from 0.30 mW to 0.40 mW, and the C / N was measured immediately after the start of still reproduction and after 5 minutes. The C / N immediately after the start was 50.1 dB, and the C / N after 5 minutes had passed was 50.0 dB. For the measurement of C / N, 16 data were taken in using a spectrum analyzer and the average value was taken.
[0075]
Furthermore, when the reproducing power was increased to 0.38 mW, the C / N immediately after the start of still reproduction was 51.1 dB, and the C / N after 5 minutes had elapsed was 51.1 dB. In other words, the C / N condition necessary for the jitter of 2T alone to become 9% was sufficiently satisfied. (See Fig. 14)
[0076]
As described above, in the optical disk of the second embodiment, the C / N immediately after the start of the still reproduction and the C / N after the elapse of 5 minutes hardly change, that is, the optical disk having stable performance without reproduction deterioration. You can see that.
[0077]
Next, an experiment was performed by setting the ratio of Ge and Sb / Te to be the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 1.0 to 4-v2. An experimental result exceeding 0.34 as the reproducing power and 7.10 as the average initial jitter was obtained. In other words, it can be seen that the optical disk in this example is an optical disk that sufficiently satisfies the next-generation standard as the reproduction power output and the initial jitter.
[0078]
Next, an experiment was performed by setting the ratio of Sb / Te to the same amount of Ge and slightly changing the amounts of Sb and Te, and setting the amount of V to 1.5 to 4-v3. As a result, an experimental result of 0.38 similar to that described above and an average initial jitter of 7.05, which is much higher than that of 4-v2, was obtained. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0079]
Next, an experiment was performed by setting the ratio of Sb / Te to the same amount of Ge and slightly changing the amounts of Sb and Te, and further setting the amount of V to 2.0 to 4-v4. Sufficient experimental results were obtained with a reproduction power of 0.38 as described above and an average initial jitter of 7.13. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0080]
Next, an experiment was performed by setting the ratio of Ge and Sb / Te to be the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 2.5 to 4-v5. The reproduction power was 0.38 as above, the average initial jitter was 8.65, and the sample No. The experimental result was worse than 4. That is, it can be seen that the optical disk in this example is an optical disk that does not satisfy the next-generation standard as the reproduction power output and the initial jitter.
[0081]
Next, the experiment was performed by setting the ratio of Ge and Sb / Te to be the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 3.0 to 4-v6. The reproduction power was 0.38, similar to the above, and the average initial jitter was 9.82, which was an experimental result worse than that of 4-v5. That is, it can be seen that the optical disk in this example is also an optical disk that does not satisfy the next-generation standard in the reproduction power output and the initial jitter.
[0082]
Here, since an error of about 0.2 dB occurs as a measurement error, the C / N change immediately after the start of reproduction is considered to be good if the change in C / N is 0.2 dB or less. Here, when the strength of the reproduction power that can withstand the C / N deterioration of 0.2 dB or less after elapse of 5 minutes was examined, it was possible to withstand up to 0.38 mW. From this, it can be understood that the optical disc 10 according to the second embodiment has a high durability against the reproduction light and satisfies the next-generation standard.
[0083]
Further, it can be understood from these 4-v1 to 4-v6 that the amount of V in the range of 0.5 to 2.0 is good as the initial jitter.
[0084]
Next, sampleNo. 7 will be described with reference to FIG. In FIG. 6, 7 indicates sampleNo7 in FIG. 15 described later, and 7-v1 to 7-v6 indicate the durable reproduction power and the average initial jitter of the sampleNo7 when the amount of V is changed. It shows the status.
[0085]
(Example 3)
A reflective layer 2, a first protective layer 3, a recording layer 4, and a second protective layer 5 were sequentially formed on a polycarbonate substrate 1 having a diameter of 120 mm by the same method as in Example 1 described above by a sputtering method. Thereafter, a UV curing resin was used as the adhesive layer 6, and the cover sheet 7 was bonded thereon. At this time, the thickness of each layer was 50 nm for the reflective layer 2, 10 nm for the first protective layer 3, 18 nm for the recording layer 4, and 50 nm for the second protective layer 5.
[0086]
The composition of the recording layer 4 was V0.5%, Ge4.6%, Sb75.9%, and Te19.0% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, initialization was performed with a laser beam spot diameter of 120 μm, an initialization condition of a linear velocity of 4 m / s, a feed pitch of 40 μm, and a laser output of 570 mW.
[0087]
Here, the laser output of the initialization is the same as that of a comparative example using GeSbTe described later, but is a result of optimization to VGeSbTe. Then, the 1-7 modulated information signal is 5.28 m / s, as shown in FIG. 2, 1T = 15.1 nsec by the strategy, and P1 = 5 as shown in sample No7 of the recording condition list of FIG. .2mW, P2 = 3.1mW, P3 = 0.1mW, P4 = 0.1mW, Strategy T, Groove at T1 = 0.5T, T2 = 0.5T, T3 = 0.8T, T4 = 0.8T , And sliced at the center of the amplitude of the reproduced signal to measure clock to data jitter.
[0088]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The jitter after the initial recording was 7.30% at the beginning of the recording mark and 7.10% at the rear end of the recording mark, indicating that good recording was possible. (Refer to 7-v1 in FIG. 6)
[0089]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was changed from 0.30 mW to 0.40 mW, and the C / N was measured immediately after the start of still reproduction and after 5 minutes. The C / N immediately after the start was 50.2 dB, and the C / N after 5 minutes had passed was 50.2 dB. For the measurement of C / N, 16 data were taken in using a spectrum analyzer and the average value was taken.
[0090]
Further, when the reproducing power was increased to 0.38 mW, the C / N immediately after the start of still reproduction was 51.2 dB, and the C / N after 5 minutes had elapsed was 51.1 dB. In other words, the C / N condition necessary for the jitter of 2T alone to become 9% was sufficiently satisfied. (See Fig. 14)
[0091]
As described above, in the optical disk of the third embodiment, the C / N immediately after the start of still reproduction and the C / N after 5 minutes have hardly changed, that is, an optical disk having stable performance without reproduction deterioration. You can see that.
[0092]
Next, an experiment was performed by setting the ratio of Ge and Sb / Te to be the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 1.0 to 7-v2. , As a result, 0.38 was obtained as the durable reproduction power, and 7.15 as the average initial jitter. In other words, it can be seen that the optical disk in this example is an optical disk that sufficiently satisfies the next-generation standard as the reproduction power output and the initial jitter.
[0093]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 1.5 to 7-v3. As a result, an experimental result of 0.38 similar to that described above and 7.07 as the average initial jitter was obtained, which was higher than that of 7-v2. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0094]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed with 7-v4 when the amount of V was 2.0. Sufficient experimental results were obtained with a reproduction power of 0.38 as described above and an average initial jitter of 7.18. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0095]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 2.5 to 7-v5. The reproduction power was 0.38 as above, the average initial jitter was 8.25, and the sample No. The result was almost equivalent to 7. That is, it can be seen that the optical disk in this example is an optical disk that does not satisfy the next-generation standard as the reproduction power output and the initial jitter.
[0096]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and further, the amount of V was set to 3.0, and the experiment was performed by setting 7-v6. The reproducing power was 0.38, similar to the above, and the average initial jitter was 9.34, which was an experimental result worse than that of 7-v6. That is, it can be seen that the optical disk in this example is also an optical disk that does not satisfy the next-generation standard in the reproduction power output and the initial jitter.
[0097]
Here, since an error of about 0.2 dB occurs as a measurement error, the C / N change immediately after the start of reproduction is considered to be good if the change in C / N is 0.2 dB or less. Here, when the strength of the reproduction power that can withstand the C / N deterioration of 0.2 dB or less after elapse of 5 minutes was examined, it was possible to withstand up to 0.38 mW. From this, it can be understood that the optical disc 10 according to the third embodiment has a high durability against the reproduction light and satisfies the next-generation standard.
[0098]
Also, from 7-v1 to 7-v6, it can be understood that the amount of V in the range of 0.5 to 2.0 is good as the initial jitter.
[0099]
Next, sampleNo. 9 will be described with reference to FIG. In FIG. 7, reference numeral 9 denotes a sample No 9 in FIG. 15, which will be described later. It shows the status.
[0100]
(Example 4)
A reflective layer 2, a first protective layer 3, a recording layer 4, and a second protective layer 5 were sequentially formed on a polycarbonate substrate 1 having a diameter of 120 mm by the same method as in Example 1 described above by a sputtering method. Thereafter, a UV curing resin was used as the adhesive layer 6, and the cover sheet 7 was bonded thereon. At this time, the thickness of each layer was 50 nm for the reflective layer 2, 10 nm for the first protective layer 3, 18 nm for the recording layer 4, and 50 nm for the second protective layer 5.
[0101]
The composition of the recording layer 4 was V0.5%, Ge6.2%, Sb68.7%, and Te24.6% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, initialization was performed with a laser beam spot diameter of 120 μm, an initialization condition of a linear velocity of 4 m / s, a feed pitch of 40 μm, and a laser output of 570 mW.
[0102]
Here, the laser output of the initialization is the same as that of a comparative example using GeSbTe described later, but is a result of optimization to VGeSbTe. Then, the 1-7 modulated information signal is 5.28 m / s, as shown in FIG. 2, the strategy is 1T = 15.1 nsec. .2mW, P2 = 2.7mW, P3 = 0.1mW, P4 = 0.1mW, Strategy T, Groove at T1 = 0.4T, T2 = 0.4T, T3 = 0.6T, T4 = 0.6T , And sliced at the center of the amplitude of the reproduced signal to measure clock to data jitter.
[0103]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The jitter after the initial recording was 7.10% at the beginning of the recording mark and 7.00% at the rear end of the recording mark, and good recording was possible. (Refer to 9-v1 in FIG. 7)
[0104]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was changed from 0.30 mW to 0.40 mW, and the C / N was measured immediately after the start of still reproduction and after 5 minutes. The C / N immediately after the start was 50.2 dB, and the C / N after 5 minutes had passed was 50.1 dB. For the measurement of C / N, 16 data were taken in using a spectrum analyzer and the average value was taken.
[0105]
Further, when the reproduction power was increased to 0.38 mW, the C / N immediately after the start of still reproduction was 51.2 dB, and the C / N after 5 minutes had elapsed was 51.2 dB. In other words, the C / N condition necessary for the jitter of 2T alone to become 9% was sufficiently satisfied. (See Fig. 14)
[0106]
As described above, in the optical disk of the fourth embodiment, the C / N immediately after the start of still reproduction and the C / N after 5 minutes have hardly changed, that is, an optical disk having stable performance without reproduction deterioration. You can see that.
[0107]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was carried out with 9-v2 when the amount of V was 1.0. An experimental result exceeding 0.3-9 as the reproducing power and 6.97 as the average initial jitter was obtained. In other words, it can be seen that the optical disk in this example is an optical disk that sufficiently satisfies the next-generation standard as the reproduction power output and the initial jitter.
[0108]
Next, an experiment was performed by setting the ratio of Sb / Te to the same amount of Ge and slightly changing the amounts of Sb and Te, and setting the amount of V to 1.5 to 9-v3. As a result, an experimental result of 0.39 similar to that described above and an average initial jitter of 6.92, which is higher than that of 9-v2, was obtained. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0109]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed with 9-v4 when the amount of V was 2.0. Sufficient experimental results were obtained with a reproduction power of 0.39 as above and an average initial jitter of 7.02. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0110]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed with 9-v5 when the amount of V was 2.5. The reproduction power was 0.39 as above, the average initial jitter was 8.37, and the sample No. The result was worse than 9. That is, it can be seen that the optical disk in this example is an optical disk that does not satisfy the next-generation standard as the reproduction power output and the initial jitter.
[0111]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 3.0 to 9-v6. The reproducing power was 0.39 as above, and the average initial jitter was 9.43, which was an experimental result worse than that of 9-v6. That is, it can be seen that the optical disk in this example is also an optical disk that does not satisfy the next-generation standard in the reproduction power output and the initial jitter.
[0112]
Here, since an error of about 0.2 dB occurs as a measurement error, the C / N change immediately after the start of reproduction is considered to be good if the change in C / N is 0.2 dB or less. Here, when the intensity of the reproduction power that can withstand the C / N deterioration after 0.2 minutes of 0.2 minutes or less after the elapse of 5 minutes was examined, it was possible to withstand up to 0.39 mW. From this, it can be understood that the optical disc 10 according to the fourth embodiment has a high durability against the reproduction light and satisfies the next-generation standard.
[0113]
From 9-v1 to 9-v6, it can be understood that the amount of V in the range of 0.5 to 2.0 is good as the initial jitter.
[0114]
Next, sampleNo. 15 will be described with reference to FIG. In FIG. 8, reference numeral 15 denotes a sampleNo. 15 and 15-v1 to 15-v6 indicate sampleNo. 15 shows the state of the durable reproduction power and the average initial jitter when the amount of V is changed.
[0115]
(Example 5)
A reflective layer 2, a first protective layer 3, a recording layer 4, and a second protective layer 5 were sequentially formed on a polycarbonate substrate 1 having a diameter of 120 mm by the same method as in Example 1 described above by a sputtering method. Thereafter, a UV curing resin was used as the adhesive layer 6, and the cover sheet 7 was bonded thereon. At this time, the thickness of each layer was 50 nm for the reflective layer 2, 10 nm for the first protective layer 3, 18 nm for the recording layer 4, and 50 nm for the second protective layer 5.
[0116]
The composition of the recording layer 4 was V0.5%, Ge8.7%, Sb69.2%, and Te21.6% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, initialization was performed with a laser beam spot diameter of 120 μm, an initialization condition of a linear velocity of 4 m / s, a feed pitch of 40 μm, and a laser output of 570 mW.
[0117]
Here, the laser output of the initialization is the same as that of a comparative example using GeSbTe described later, but is a result of optimization to VGeSbTe. Thereafter, the 1-7 modulated information signal is 5.28 m / s, and as shown in FIG. 2, 1T = 15.1 nsec is set as a strategy, and sampleNo. As shown in FIG. 15, P1 = 5.2 mW, P2 = 2.7 mW, P3 = 0.1 mW, P4 = 0.1 mW, and the strategy T is T1 = 0.4T, T2 = 0.4T, T3 = 0.6T. , T4 = 0.6T, and sliced at the center of the amplitude of the reproduced signal to measure clock to data jitter.
[0118]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The jitter after the initial recording was 6.90% at the beginning of the recording mark and 6.80% at the rear end of the recording mark, indicating that good recording was possible. (Refer to 15-v1 in FIG. 8)
[0119]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was changed from 0.30 mW to 0.40 mW, and the C / N was measured immediately after the start of still reproduction and after 5 minutes. The C / N immediately after the start is 50.5 dB, and the C / N after 5 minutes has elapsed is
It was 50.5 dB. For the measurement of C / N, 16 data were taken in using a spectrum analyzer and the average value was taken.
[0120]
Further, when the reproducing power was increased to 0.38 mW, the C / N immediately after the start of still reproduction was 51.5 dB, and the C / N after 5 minutes had elapsed was 51.5 dB. In other words, the C / N condition necessary for the jitter of 2T alone to become 9% was sufficiently satisfied. (See Fig. 14)
[0121]
As described above, in the optical disk of the fifth embodiment, the C / N immediately after the start of still reproduction and the C / N after 5 minutes have not changed, that is, the optical disk has stable performance without reproduction deterioration. I understand.
[0122]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 1.0 to 15-v2. The experimental result was 0.39 as the reproducing power and 6.90 as the average initial jitter, which was almost the same as that of 15-v1. In other words, it can be seen that the optical disk in this example is an optical disk that sufficiently satisfies the next-generation standard as the reproduction power output and the initial jitter.
[0123]
Next, the amount of Ge and the ratio of Sb / Te were set to be the same, the amount of Sb and Te was slightly changed, and further, when the amount of V was set to 1.5, an experiment was performed with 15-v3. As a result, an experimental result of 0.39 similar to that described above and an average initial jitter of 6.85, which is higher than that of 15-v2, was obtained. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0124]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 2.0 to 15-v4. Sufficient experimental results were obtained with a reproduction power of 0.39 as above and an average initial jitter of 6.90. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0125]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 2.5 to 15-v5. The reproduction power was 0.39 as above, the average initial jitter was 8.20, and the sample No. The result was worse than 15. That is, it can be seen that the optical disk in this example is an optical disk that does not satisfy the next-generation standard as the reproduction power output and the initial jitter.
[0126]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and further, the amount of V was set to 3.0, and the experiment was performed with 15-v6. The reproducing power was 0.39, similar to the above, and the average initial jitter was 9.10, which was an experimental result worse than that of the 15-v6. That is, it can be seen that the optical disk in this example is also an optical disk that does not satisfy the next-generation standard in the reproduction power output and the initial jitter.
[0127]
Here, since an error of about 0.2 dB occurs as a measurement error, the C / N change immediately after the start of reproduction is considered to be good if the change in C / N is 0.2 dB or less. Here, when the intensity of the reproduction power that can withstand the C / N deterioration after 0.2 minutes of 0.2 minutes or less after the elapse of 5 minutes was examined, it was possible to withstand up to 0.39 mW. From this, it can be understood that the optical disc 10 according to the fifth embodiment has high durability against the reproduction light and satisfies the next-generation standard.
[0128]
Further, from 15-v1 to 15-v6, it can be understood that the amount of V in the range of 0.5 to 2.0 is good as the initial jitter.
[0129]
Next, sampleNo. 16 will be described with reference to FIG. In FIG. 9, reference numeral 16 denotes sampleNo. 16, 16-v1 to 16-v6 indicate the sampleNo. 16 shows the state of the durable reproduction power and the average initial jitter when the amount of V is changed.
[0130]
(Example 6)
A reflective layer 2, a first protective layer 3, a recording layer 4, and a second protective layer 5 were sequentially formed on a polycarbonate substrate 1 having a diameter of 120 mm by the same method as in Example 1 described above by a sputtering method. Thereafter, a UV curing resin was used as the adhesive layer 6, and the cover sheet 7 was bonded thereon. At this time, the thickness of each layer was 50 nm for the reflective layer 2, 10 nm for the first protective layer 3, 18 nm for the recording layer 4, and 50 nm for the second protective layer 5.
[0131]
The composition of the recording layer 4 was V0.5%, Ge11.1%, Sb68.8%, and Te19.6% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, initialization was performed with a laser beam spot diameter of 120 μm, an initialization condition of a linear velocity of 4 m / s, a feed pitch of 40 μm, and a laser output of 570 mW.
[0132]
Here, the laser output of the initialization is the same as that of a comparative example using GeSbTe described later, but is a result of optimization to VGeSbTe. Thereafter, the 1-7 modulated information signal is 5.28 m / s, and as shown in FIG. 2, 1T = 15.1 nsec is set as a strategy, and sampleNo. As shown in FIG. 16, P1 = 5.2 mW, P2 = 3.1 mW, P3 = 0.1 mW, P4 = 0.1 mW, and the strategy T is T1 = 0.5T, T2 = 0.5T, T3 = 0.8T. , T4 = 0.8T, and the slice was sliced at the center of the amplitude of the reproduced signal, and clock to data jitter was measured.
[0133]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The jitter after the initial recording was 7.19% at the beginning of the recording mark and 7.17% at the rear end of the recording mark, and good recording was possible. (Refer to 16-v1 in FIG. 9)
[0134]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was changed from 0.30 mW to 0.39 mW, and the C / N was measured immediately after the start of still reproduction and after 5 minutes had elapsed. The C / N immediately after the start was 50.2 dB, and the C / N after 5 minutes had passed was 50.2 dB. For the measurement of C / N, 16 data were taken in using a spectrum analyzer and the average value was taken.
[0135]
Furthermore, when the reproducing power was increased to 0.38 mW, the C / N immediately after the start of still reproduction was 51.1 dB, and the C / N after 5 minutes had elapsed was 51.1 dB. In other words, the C / N condition necessary for the jitter of 2T alone to become 9% was sufficiently satisfied. (See Fig. 14)
[0136]
As described above, in the optical disk of the sixth embodiment, the C / N immediately after the start of still reproduction and the C / N after 5 minutes have not changed, that is, the optical disk has stable performance without reproduction deterioration. I understand.
[0137]
Next, the experiment was performed by setting the ratio of Ge and Sb / Te to be the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 1.0 to 16-v2. As a result, 0.40 was obtained as the reproduction power, and 7.02 was obtained as the average initial jitter. In other words, it can be seen that the optical disk in this example is an optical disk that sufficiently satisfies the next-generation standard as the reproduction power output and the initial jitter.
[0138]
Next, an experiment was performed by setting the ratio of Sb / Te to the same amount of Ge and slightly changing the amounts of Sb and Te, and further setting the amount of V to 1.5 to 16-v3. As a result, an experimental result of 0.40 similar to that described above and an average initial jitter of 6.98, which is higher than that of 16-v2, was obtained. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0139]
Next, the experiment was performed by setting the ratio of Ge and Sb / Te to the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 2.0 to 16-v4. Sufficient experimental results were obtained with a reproduction power of 0.40 as above and an average initial jitter of 7.14. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0140]
Next, the experiment was performed by setting the ratio of Sb / Te to the same amount of Ge and changing the amounts of Sb and Te slightly, and further setting the amount of V to 2.5 to 16-v5. The reproduction power was 0.40 as above, and the average initial jitter was 8.48, which was worse than that of Sample 16. That is, it can be seen that the optical disk in this example is an optical disk that does not satisfy the next-generation standard as the reproduction power output and the initial jitter.
[0141]
Next, the experiment was performed by setting the ratio of Ge and Sb / Te to be the same, slightly changing the amounts of Sb and Te, and setting the amount of V to 3.0 to 16-v6. The reproduction power was 0.40, similar to the above, and the average initial jitter was 9.72, which was an experimental result worse than that of 16-v6. That is, it can be seen that the optical disk in this example is also an optical disk that does not satisfy the next-generation standard in the reproduction power output and the initial jitter.
[0142]
Here, since an error of about 0.2 dB occurs as a measurement error, the C / N change immediately after the start of reproduction is considered to be good if the change in C / N is 0.2 dB or less. Here, when the intensity of the reproduction power that can withstand the C / N deterioration after 0.2 minutes of 0.2 minutes or less after the elapse of 5 minutes was examined, it was possible to withstand up to 0.39 mW. From this, it can be understood that the optical disc 10 according to the sixth embodiment has high durability against the reproduction light and satisfies the next-generation standard.
[0143]
It can be understood from these 16-v1 to 16-v6 that the amount of V in the range of 0.5 to 2.0 is good as the initial jitter.
[0144]
Next, sampleNo. 17 will be described with reference to FIG. In FIG. 10, reference numeral 17 denotes sampleNo. 17, 17-v1 to 17-v6 indicate the sampleNo. 17 shows the state of the durable reproduction power and the average initial jitter when the amount of V is changed.
[0145]
(Example 7)
A reflective layer 2, a first protective layer 3, a recording layer 4, and a second protective layer 5 were sequentially formed on a polycarbonate substrate 1 having a diameter of 120 mm by the same method as in Example 1 described above by a sputtering method. Thereafter, a UV curing resin was used as the adhesive layer 6, and the cover sheet 7 was bonded thereon. At this time, the thickness of each layer was 50 nm for the reflective layer 2, 10 nm for the first protective layer 3, 18 nm for the recording layer 4, and 50 nm for the second protective layer 5.
[0146]
The composition of the recording layer 4 was V0.5%, Ge 14.5%, Sb 64.8%, and Te 20.2% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, initialization was performed with a laser beam spot diameter of 120 μm, an initialization condition of a linear velocity of 4 m / s, a feed pitch of 40 μm, and a laser output of 570 mW.
[0147]
Here, the laser output of the initialization is the same as that of a comparative example using GeSbTe described later, but is a result of optimization to VGeSbTe. Thereafter, the 1-7 modulated information signal is 5.28 m / s, and as shown in FIG. 2, 1T = 15.1 nsec is set as a strategy, and sampleNo. As shown in FIG. 17, P1 = 5.2 mW, P2 = 2.7 mW, P3 = 0.1 mW, P4 = 0.1 mW, and the strategy T was T1 = 0.4T, T2 = 0.4T, T3 = 0.6T. , T4 = 0.6T, and sliced at the center of the amplitude of the reproduced signal to measure clock to data jitter.
[0148]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The jitter after the initial recording was 7.09% at the beginning of the recording mark and 7.07% at the rear end of the recording mark, indicating that good recording was possible. (Refer to 17-v1 in FIG. 10)
[0149]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was changed from 0.30 mW to 0.40 mW, and the C / N was measured immediately after the start of still reproduction and after 5 minutes. The C / N immediately after the start was 50.3 dB, and the C / N after 5 minutes had passed was 50.2 dB. For the measurement of C / N, 16 data were taken in using a spectrum analyzer and the average value was taken.
[0150]
Further, when the reproducing power was increased to 0.38 mW, the C / N immediately after the start of still reproduction was 51.3 dB, and the C / N after 5 minutes had elapsed was 51.2 dB. In other words, the C / N condition necessary for the jitter of 2T alone to become 9% was sufficiently satisfied. (See Fig. 14)
[0151]
As described above, in the optical disk of the sixth embodiment, the C / N immediately after the start of still reproduction and the C / N after 5 minutes have hardly changed, that is, an optical disk having stable performance without reproduction deterioration. You can see that.
[0152]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 1.0 to 17-v2. As a result, 0.40 was obtained as the reproducing power, and 6.97 as the average initial jitter. In other words, it can be seen that the optical disk in this example is an optical disk that sufficiently satisfies the next-generation standard as the reproduction power output and the initial jitter.
[0153]
Next, the amount of Ge and the ratio of Sb / Te were set to be the same, the amount of Sb and Te was slightly changed, and an experiment was performed by setting the amount of V to 1.5 to 17-v3. As a result, an experimental result of 0.40 similar to that described above and an average initial jitter of 7.03, which exceeded 17-v1, was obtained. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0154]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 2.0 to 17-v4. Sufficient experimental results were obtained with a reproduction power of 0.40 as above and an average initial jitter of 7.07. In other words, it can be seen that the optical disk in this example is also an optical disk that sufficiently satisfies the next-generation standards as the reproduction power output and the initial jitter.
[0155]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the experiment was performed by setting the amount of V to 2.5 to 17-v5. The reproduction power was 0.40 as above, and the average initial jitter was 8.14, which was worse than that of sample 17. That is, it can be seen that the optical disk in this example is an optical disk that does not satisfy the next-generation standard as the reproduction power output and the initial jitter.
[0156]
Next, the amount of Ge and the ratio of Sb / Te were made the same, the amount of Sb and Te was slightly changed, and the amount of V was set to 3.0. The reproduction power was 0.40, similar to the above, and the average initial jitter was 9.49, which was an experimental result worse than that of 17-v5. That is, it can be seen that the optical disk in this example is also an optical disk that does not satisfy the next-generation standard in the reproduction power output and the initial jitter.
[0157]
Here, since an error of about 0.2 dB occurs as a measurement error, the C / N change immediately after the start of reproduction is considered to be good if the change in C / N is 0.2 dB or less. Here, when the strength of the reproduction power that the C / N deterioration after 5 minutes passed was less than 0.2 dB was examined, it was possible to withstand up to 0.40 mW. From this, it can be understood that the optical disc 10 according to the seventh embodiment has a strong durability against the reproduction light and satisfies the next-generation standard.
[0158]
Also, from 17-v1 to 17-v6, it can be understood that the amount of V in the range of 0.5 to 2.0 is good as the initial jitter.
[0159]
FIG. 11 is an explanatory diagram showing the amount of Ge in each sample in the V-added recording layer composition, FIG. 12 is an explanatory diagram showing the same Sb / Te ratio, and FIG. FIG. 3 is an explanatory diagram showing recording power and strategy as conditions.
[0160]
Next, the properties of each component of the recording layer according to the present embodiment will be described. V is a high melting point element exceeding 2,000 K in comparison with the melting point of Ge, Sb, and Te being 700 K to 1200 K, and is very thermally stable. Further, it is a stable substance that does not react with Ge, Sb, and Te contained in the recording layer constituting the optical disc of the present embodiment, and does not react with the material forming the adjacent protective layer.
[0161]
Therefore, if a large amount is added, the phase change between crystal and amorphous in the recording layer at the time of recording is hindered. However, by adding an appropriate amount, V acts as an anchor in the recording film, and the recording mark It is considered that the jitter is reduced by making the mark edge sharper at the time of formation, and it is possible to withstand even higher power with respect to the reproduction light because of its high thermal durability due to the high melting point material.
[0162]
(Comparative example)
First, on a polycarbonate substrate 1 having a diameter of 120 mm, an Ag alloy is used as the reflection layer 2, and ZnS—SiO ₂ GeSbTe as the recording layer 4 and ZnS-SiO as the second protective layer 5 ₂ Were formed in this order by a sputtering method. After that, the cover sheet 7 was attached with the UV curable resin as the adhesive layer 6. At this time, the thickness of each layer was 200 nm for the reflective layer 2, 9.5 nm for the first protective layer 3, 15 nm for the recording layer 4, and 36 nm for the second protective layer 5.
[0163]
The composition of the recording layer 4 was Ge 8.7%, Sb 69.7%, and Te 21.6% in atomic ratio. After bonding, UV irradiation was performed to sufficiently cure the adhesive layer 6. Thereafter, initialization was performed with a laser beam spot diameter of 120 μm, an initialization condition of a linear velocity of 4 m / s, a feed pitch of 40 μm, and a laser output of 570 mW.
[0164]
Thereafter, recording and reproduction of the 1-7 modulated information signal was performed at a linear velocity of 5.28 m / s according to the strategy shown in FIG. 1T = 15.1 nsec, P1 = 5.2 mW, P2 = 2.7 mW, P3 = 0.1 mW, P4 = 0.1 mW, T1 = 0.4T, T2 = 0.4T, T3 = 0.6T, T4 = 0.6T was recorded on a groove, sliced at the center of the amplitude of the reproduced signal, and clock to data jitter was measured.
[0165]
Jitter was measured with a time interval analyzer (model TA520: manufactured by Yokogawa Electric Corporation). The jitter after the initial recording was 7.7% at the beginning of the recording mark and 7.9% at the rear end of the recording mark, and normal recording was possible.
[0166]
Further, a single signal of 2T length was recorded on the same disk by the above-mentioned strategy. The recorded track was reproduced as a still and the C / N was measured. At this time, the reproduction power was set to 0.30 mW, which is a value at which the disk did not deteriorate, and the C / N was measured immediately after the start of still reproduction and after 5 minutes had elapsed. The C / N immediately after the start was 50.0 dB, and the C / N after 5 minutes had not changed was 50.0 dB.
[0167]
Here, even if the reproduction power is raised to the maximum endurance power of 0.36 mW, it stays at 50.0 dB, and reaches the C / N of 51.0 dB necessary for the above-mentioned jitter of 2T alone to become 0.9%. I never did.
[0168]
For the measurement of C / N, a spectrum analyzer was used, data was taken 16 times, and the average was taken. Here, since an error of about 0.2 dB may occur as a measurement error, it is considered that the C / N change before and after the start of the reproduction deterioration test is 0.2 dB or less, which is preferable.
[0169]
Further, compositions other than the composition of the recording layer 4 were examined. The composition studied is shown in FIG.
[0170]
As is apparent from FIG. 15, the optical disk 10 using a GeSbTe-based material for the phase-change optical recording layer 4 and using a blue laser, and exhibiting a high durability against reproduction light, is a Ge. , Sb, and Te are in the composition range of Ge 3.4% or more and 14.5% or less in atomic ratio, Sb / Te is 2.1 or more and 4 or less, and C / N is obtained in still reproduction with a reproduction power of 0.30 mW. Is within 0.2 dB, and the initial jitter is 9% or less.
[0171]
It has been found from various experiments that this preferred composition range is in the initial stage of deterioration. Hereinafter, this point will be described in detail. First, the range of Ge will be described.
[0172]
When the amount of Ge is increased, effects such as an improvement in contrast and an increase in resistance to environmental loads are obtained. Although the minimum value is set to 3.4% (atomic ratio), it may be slightly shifted in consideration of a measurement error. In addition, there is an experimental result that jitter cannot be reduced particularly when the amount of Ge is small. However, the larger the amount of Ge, the better.
[0173]
In other words, when the amount of Ge increases, the amount of Sb relatively decreases, so that the crystallization speed decreases. That is, recording and rewriting at a high linear velocity cannot be performed. Further, even at the same ratio of Sb / Te, there is an experimental result that the smaller the atomic ratio (amount) of Sb, the lower the crystallization speed. Therefore, in this case, there remains unerased data due to rewriting.
[0174]
On the other hand, increasing the amount of Ge increases the crystallization rate. A recording film crystallized at a high temperature shows high durability with very little reproduction degradation even when recorded, but if the crystallization temperature is too high, the initialization itself becomes difficult. 14.5% (atomic ratio) was the upper limit in the range where experiments were possible.
[0175]
Next, the ratio of Sb / Te will be described. As described above, the Sb / Te ratio affects the crystallization rate. When this ratio is large, the crystallization speed increases, and recording and rewriting can be performed at a higher linear velocity. Conversely, if this ratio is small, the crystallization speed will be slow. In the present embodiment, the slow limit is set to 2.1, but this is because crystallization in the initialization step becomes difficult around this limit. Further, when the ratio is less than 2.1, the crystallization state may be unstable, and adverse effects such as deterioration of contrast at the time of recording and inability to perform overwriting may occur.
[0176]
On the other hand, the fast limit is set to 4. However, if this ratio is increased, crystallization is likely to occur, so that amorphous marks are not sufficiently formed during recording. Even if it can be formed, the recorded amorphous mark has a low intensity with respect to the reproduction light, and when the recorded portion is reproduced in the still mode, the recorded mark disappears.
[0177]
In the experiment of the comparative example, the sampleNO. The composition of No. 15 exhibited good characteristics by itself, and could withstand a reproduction power of up to 0.35 mW. However, as described above, the durable reproduction power was limited to 50.0 dB at most. Below 9% is something you can't hope for. That is, it is impossible to obtain an optical information recording medium that can endure a high-output reproduction light satisfying the next-generation standard, which is intended by the present invention, and can perform recording with lower jitter. .
[0178]
As is apparent from the detailed description above, according to the configuration of the present embodiment, it can be understood that an advantageous characteristic result, which cannot be achieved at all, can be obtained with a recording material of GeSbTe alone.
[0179]
【The invention's effect】
According to the present invention, at least a reflective layer, a first protective layer, a phase-change optical recording layer, and a second protective layer are laminated in this order on a substrate, and the phase is irradiated by light from the second protective layer side. An optical information recording medium for recording and erasing information by changing the phase of a changeable optical recording layer, wherein the phase changeable optical recording layer is composed of VwGexSbyTez, and 0.5 ≦ w ≦ 2 3.4 ≦ By setting x ≦ 14.5, 2, 1 ≦ y / z ≦ 4, and w + x + y + z = 100 (atomic ratio), high output reproduction light that cannot be achieved with a GeSbTe-based recording material can be obtained. This makes it possible to obtain an optical information recording medium that can withstand and can perform recording with lower jitter.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of a basic configuration of an optical disc according to the present invention.
FIG. 2 is a diagram showing a strategy pattern at the time of recording.
FIG. 3 is a cross-sectional view showing another embodiment of the basic configuration of the optical disc according to the present invention.
FIGS. 4A and 4B are a diagram showing a reproduction light durability with respect to a recording layer composition in which V is added to a recording layer and an explanatory diagram of a first embodiment showing initial jitter.
FIGS. 5A and 5B are a diagram showing a reproduction light durability with respect to a recording layer composition in which V is added to a recording layer and an explanatory diagram of a second embodiment showing initial jitter.
FIG. 6 is a diagram showing the durability of the reproducing light with respect to the composition of the recording layer in which V is added to the recording layer, and an explanatory diagram of the third embodiment showing the initial jitter.
FIGS. 7A and 7B are a diagram showing a reproduction light durability with respect to a composition of a recording layer in which V is added to the recording layer and an explanatory diagram of a fourth embodiment showing initial jitter.
FIG. 8 is a diagram showing the reproduction light durability with respect to the composition of the recording layer in which V is added to the recording layer, and an explanatory diagram of the fifth embodiment showing the initial jitter.
FIG. 9 is a diagram showing the reproduction light durability with respect to the composition of the recording layer in which V is added to the recording layer, and an explanatory diagram of the sixth embodiment showing the initial jitter.
FIG. 10 is a diagram showing the reproduction light durability with respect to the composition of the recording layer in which V is added to the recording layer, and an explanatory diagram of the seventh embodiment showing the initial jitter.
FIG. 11 is an explanatory diagram showing the amount of Ge in each sample in the composition of a V-added recording layer.
FIG. 12 is an explanatory diagram showing the ratio of Sb / Te in each sample in the composition of a V-added recording layer.
FIG. 13 is an explanatory diagram showing a recording power and a strategy as recording conditions according to the present embodiment.
FIG. 14 is a diagram illustrating a comparison between immediately after the start of still and 5 minutes after the reproduction power is changed.
FIG. 15 is a diagram illustrating the relationship between the composition of a recording layer in a comparative example, reproduction degradation, recording / reproduction characteristics, and the like.
[Explanation of symbols]
1 substrate
2 Reflective layer
3 First protective layer
4 Recording layer
5 Second protective layer
6 adhesive layer
7 Cover sheet
8 Protective coat
10 Optical information recording medium
20 Optical information recording medium

Claims (1)

On a substrate, at least a reflective layer, a first protective layer, a phase change optical recording layer, and a second protective layer are laminated in this order, and the phase change optical recording is performed by irradiating light from the second protective layer side. An optical information recording medium for recording and erasing information by changing a layer phase,
The phase change type optical recording layer is composed of VwGexSbyTez,
0.5 ≦ w ≦ 2
3.4 ≦ x ≦ 14.5
2.1 ≦ y / z ≦ 4
w + x + y + z = 100 (atomic ratio)
An optical information recording medium, characterized in that:

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