JP2002008240A - Reproducing method of phase change optical disk and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deterioration in the archival overwrite characteristic of a phase change optical disk. SOLUTION: The reproduction is made at least once by a reproducing power higher than the normally reproducing power after the recording operation is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for reproducing a phase change optical disk, and more particularly to a method and an apparatus for reproducing a phase change optical disk in which deterioration of archival overwrite characteristics is suppressed.

[0002]

2. Description of the Related Art At present, phase change optical disks represented by digital video disks (DVDs) have been actively studied and developed as rewritable optical disks, and some of them have already been put into practical use. .

The characteristics required for a rewritable optical disk include:
The optical disc does not deteriorate due to the surrounding environment, that is, it has weather resistance. There are three kinds of characteristics in the weather resistance,
These are often called archival characteristics, shelf characteristics, and archival overwrite characteristics, respectively.

[0004] The archival characteristic relates to the preservation of recorded data, and is a characteristic that determines how long data once recorded is stable. Therefore, if the archival characteristics deteriorate, the recorded data cannot be reproduced.

[0005] The shelf characteristic determines how long an unrecorded portion exists without being deteriorated. If the shelf characteristic is deteriorated, satisfactory recording can be performed even when recording is performed on an unrecorded portion. I can no longer do it.

[0006] The archival overwrite characteristic determines how long overwriting (rewriting) can be performed on a portion which has already been recorded once or more. Write recording becomes impossible.

In order to improve the weather resistance as described above, conventionally, a method of adding an additive to a recording film (for example, Japanese Patent Application Laid-Open No.
No. 124353), a method of sandwiching a recording film with a certain protective film, and the like have been actively studied, and some results have been achieved.

[0008] However, even in the medium using these methods, the recording film is constantly changing, albeit slightly. With the recent increase in density, subtle changes in the recording film are not allowed. In particular, the archival overwrite characteristics may deteriorate in a few years even at room temperature, which is a serious problem.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned disadvantages of the prior art and, in particular, to provide a novel phase-change optical disk reproducing method which suppresses deterioration of the archival overwrite characteristics of the phase-change optical disk. The device is provided.

[0010]

SUMMARY OF THE INVENTION The present invention basically employs the following technical configuration to achieve the above object.

That is, the first aspect of the method for reproducing a phase change optical disk according to the present invention is characterized in that, in the reproduction of the phase change optical disk, after recording, the phase change optical disk is reproduced at least once with a reproduction power Pb higher than a normal reproduction power Pa. In a second aspect, a reproduction power in which the C / N degradation of a recording signal due to reproduction with the reproduction power Pb falls within 0.5 dB is used as the reproduction power Pb. In a third aspect, a reproducing power of 1.5 to 1.8 times the reproducing power Pa is used as the reproducing power Pb. The four aspects are characterized in that, after the recording of the phase change optical disc, the post-recording verification using the reproducing power Pb higher than the normal reproducing power Pa is performed.

A first aspect of the method of the apparatus for reproducing a phase change optical disk according to the present invention comprises a first means for reproducing a phase change optical disk at a normal reproduction power Pa, and a reproduction at or above the normal reproduction power Pa. And second means for reproducing the phase change optical disk using power Pb. The second mode is to reproduce the phase change optical disk with normal reproduction power Pa First
And second means for reproducing the phase-change optical disc in order to perform post-recording verification using a reproduction power Pb equal to or higher than the normal reproduction power Pa at the time of post-record verification of the phase-change optical disc. In a third aspect, the C / N deterioration of a recording signal due to reproduction with the reproduction power Pb is:
A reproducing power falling within 0.5 dB is used as the reproducing power Pb;
The fourth mode is characterized in that a reproduction power 1.5 to 1.8 times the reproduction power Pa is used as the reproduction power Pb.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic flow of an optical disk reproducing method according to the present invention. Characteristically, before the reproduction with the normal reproduction power Pa, the recorded data is reproduced with the reproduction power Pb higher than the normal reproduction power Pa. In the conventional reproducing method, there is no reproducing step using the reproducing power Pb. Since reproduction using the reproduction power Pb may be performed before the next recording, the reproduction power Pb is used.
The reproduction with the reproduction power Pa may be performed before the reproduction with b, or the reproduction power Pa and the reproduction power Pb may be alternately repeated several times.

The reason why the reproduction is performed with the reproduction power Pb is that the archival overwrite characteristics are not deteriorated.

FIG. 2 shows experimental data demonstrating the principle of the present invention. FIG. 2 shows how noise when overwriting a recording mark stored for a long time is changed by irradiating light of the reproduction power Pb. The vertical axis in FIG. 2 records on a phase change optical disk,
Immediately after that, the difference between the noise level when overwrite recording is performed and the noise level when the overwrite recording is performed after leaving it at 80 ° C. for 30 hours is shown. The plus direction means that the noise level after standing has increased, indicating that the archival overwrite characteristics have deteriorated. The meaning of leaving at 80 ° C. for 30 hours is to test the change in overwrite recording noise after long-term storage at an accelerated rate. The horizontal axis represents the irradiation time of the reproduction power Pb of the present invention, and indicates how much light of the reproduction power Pb was applied to the recording mark left at 80 ° C. for 30 hours. In FIG. 2, as the reproduction power Pb,
1.1 mW, and the normal reproduction power Pa is 0.8 mW.

As can be seen from FIG. 2, the reproduction power P
If the reproduction time at b is long, it can be seen that the noise rise amount is reduced and the archival overwrite characteristics are not degraded (see black circles in the figure). Playback time of PB,
“0” means the conventional reproducing method, and it can be seen that the conventional reproducing method cannot suppress the deterioration of the archival overwrite characteristics.

FIG. 2 also shows the experimental results of archival overwrite characteristics when a recording mark left at 80 ° C. for 30 hours is reproduced for 20 minutes at a reproducing power Pb and then left at 80 ° C. for 30 hours. And the black triangles indicate the data. The meaning of this data is that a recording mark that has been reproduced once with the reproduction power Pb and has reached an area where the archival overwrite characteristics do not deteriorate does not subsequently deteriorate the archival overwrite characteristics.
In other words, the reproduction with the reproduction power Pb may be performed before the next overwrite, and once performed, it is not necessary to perform the reproduction until the next overwrite is performed.

In the case of this example, the reproduction power Pb is set to 1.1
Although set to mW, the higher the power, the shorter the required playback time. FIG. 3 shows this. The vertical axis shows the number of times of reproduction necessary to prevent the archival overwrite characteristics from deteriorating, and the horizontal axis shows the value of the reproduction power Pb. At 1.3 mW or more, the effect can be obtained by reproducing once, and the number of times of reproduction is saturated.

On the other hand, the higher the reproduction power Pb is, the better it is not. The higher the reproduction power Pb, the more the characteristics become problematic. That is, when the reproducing power Pb is applied, the recording mark itself is erased, and the data is lost. FIG. 4 shows the relationship between the reproduction power Pb and the deterioration of the C / N of the recording data. It can be seen that the higher the reproduction power, the more the deterioration of the C / N. In this case, the number of reproductions at each reproduction power Pb is as shown in FIG.
(The number of reproductions at which archival overwrite characteristics do not deteriorate). It can be seen that at a power higher than the power at which the effect can be obtained by one reproduction, erasure starts in addition to the improvement of the archival overwrite characteristics.

Therefore, it is desirable to set the value of the reproducing power Pb to about 1.5 to 1.8 times the normal reproducing power Pa, and to adjust the number of times of reproduction in accordance with the setting. In practice, it would be more efficient to set the reproduction power so that the effect is obtained by one reproduction and the erasure is small.

The invention based on the above experimental facts is the phase change optical disk reproducing method of the present invention. If the present invention is used, archival overwrite characteristics can be prevented from deteriorating.

In a phase change optical disk device used as an external storage device of a personal computer, after recording, in order to judge whether or not the recording has been performed normally, the recording data is reproduced and confirmed once. There are many things. This operation is called "verify", but if the reproduction is performed with the reproduction power Pb of the present invention at the time of this verification, it is very efficient. In other words, the process for stopping the deterioration of the archival overwrite characteristic is performed at the same time as the verification, so that the number of birds per stone is two. This is the phase change optical disk device of the present invention.

[0023]

(Embodiment 1) A first embodiment of the present invention will be described below.

As the phase change recording medium, the one shown in FIG. 5 was used. It consists of a recording film 11 sandwiched between a substrate 14 and a dielectric film. In FIG. 5, only the two dielectric films 12, 13 and the recording film 11 are shown on the substrate 14, but on the dielectric film on the recording film 11 (the dielectric film furthest from the substrate). A reflective film or the like may be formed.
GeSbTe, a chalcogenide-based material, is used as the recording film.
System, InSbTe system, InSe system, InTe system, AsTeGe system, TeOx-GeSn
System, TeSeSn system, SbSeBi system, BiSeGe system, AgInSbTe system phase change material is used. In addition, as the reflection film, Al, A
lTi or the like is desirable.

As the material of the substrate, polycarbonate,
A synthetic resin such as acryl, glass, or the like can be used, and those coated with a resin or the like may be used. As the shape of the substrate, a disk shape or a card shape is used.

As the substrate 14, a polycarbonate substrate having a diameter of 120 mm, a track pitch of 0.58 μm, and a substrate thickness of 0.6 mm was used.
The s-SiO ₂ film is 170 nm, and the recording film 11 is Ge ₂
14 nm of Sb ₂ Te ₅ film and Zns−
An SiO ₂ film of 20 nm was sequentially formed. This time, an AlTi film is formed to a thickness of 100 nm on the protective film 13.

0.8 mW as a normal reproducing power Pa,
As the reproduction power Pb, 1.3 mW was used.

First, recording was performed on the above-described phase-change optical disk, and the error rate of the recorded data was measured while performing reproduction with normal reproduction power Pa.
A good error rate of about 0 × 10 ⁻⁶ was obtained. Thereafter, the recorded data is reproduced once with the reproduction power Pb,
Thereafter, when the error rate was measured at a normal reproducing power Pa, an equivalent error rate was obtained. In order to check how much the reproduction with the reproduction power Pb has an effect on the C / N level, a signal of a single cycle was recorded separately from the above-mentioned recording and reproduced with the reproduction power Pb.
The deterioration of N was about 0.2 dB. It was confirmed that although the recorded data was degraded by the reproduction with the reproduction power Pb, the error rate was at a level having no problem.

The recorded phase change optical disk which has been subjected to the above processing is loaded into an environmental tester,
Left for hours. Thereafter, overwriting was performed on the already recorded data of the phase-change optical disc, and the error rate after overwriting was measured with the reproduction power Pa.
An error rate of about × 10 ⁻⁶ was obtained. That is, the archival overwrite characteristics were successfully suppressed from deteriorating.

(Embodiment 2) The same phase change optical disk as in Embodiment 1 was used, and the normal reproducing power Pa was 0.8 m
An experiment was performed when 1.5 mW was used as W and the reproduction power Pb.

First, recording was performed on the above-mentioned phase-change optical disk, and the error rate of the recorded data was measured while performing reproduction with normal reproduction power Pa.
A good error rate of about 0 × 10 ⁻⁶ was obtained. Thereafter, the recorded data is reproduced once with the reproduction power Pb,
Thereafter, when the error rate was measured at a normal reproducing power Pa, the error rate was degraded to about 1.0 × 10 ⁻⁵ . In this state, practical problems arise even if the archival overwrite characteristics are improved. In order to check how much the reproduction with the reproduction power Pb has an effect on the C / N level, a signal of a single cycle was recorded separately from the above-described recording, and reproduction was performed with the reproduction power Pb. Deterioration was about 0.6 dB. It is desirable that the C / N degradation during reproduction by the reproduction power Pb be suppressed to within 0.5 dB.

(Embodiment 3) The same phase change optical disk as in Embodiment 1 was used, and the normal reproducing power Pa was 0.8 mW,
An experiment was performed when 1.2 mW was used as the reproduction power Pb.

First, recording was performed on the above-mentioned phase-change optical disk, and the error rate of the recorded data was measured while performing reproduction with normal reproduction power Pa.
A good error rate of about 0 × 10 ⁻⁶ was obtained. Thereafter, the recorded data is reproduced with the reproduction power Pb (the number of times of reproduction was changed variously), and the recorded data was put into an environmental tester, where the archival overwrite characteristics were deteriorated.
When the reproduction with the reproduction power Pb was performed 100 times or more, the archival overwrite characteristics could be prevented from deteriorating. The reproduction of about 100 times corresponds to the reproduction of the same track for about several seconds, and the processing of the present invention can be performed during the waiting time when the apparatus does not particularly need to operate. Therefore, in consideration of the second embodiment, the range of the reproduction power Pb is 1.5 times the reproduction power Pa.
It is desirably about 1.8 times.

(Embodiment 4) Using the same phase-change optical disk as in Embodiment 1, a phase-change optical disk device for performing verification after recording was manufactured, and the reproducing power for verification was 1.3 m.
An archival overwrite characteristic experiment with W was performed. 0.8 mW is used as the normal reproducing power Pa.

When recording was performed by the above apparatus, it was determined that there was no problem when verifying the recorded data. Thereafter, the phase-change optical disk on which recording was performed by the above-described apparatus was put into an environmental tester, and was left at 80 ° C. for 100 hours.
Then, when overwriting was performed on the recorded data of the phase change optical disk using the above apparatus, it was determined that there was no problem at the time of verification. That is, the archival overwrite characteristics were successfully suppressed from deteriorating.

(Example 5) An archival overwrite characteristic experiment was conducted using the same phase-change optical disk as in Example 1 and the same apparatus as in Example 4 when the reproducing power for verification was 1.5 mW. 0.8 mW is used as the normal reproducing power Pa.

When recording was performed by the above apparatus, a problem was pointed out at the time of verifying the recorded data, and it was found that the reproducing power for verification was too high. In consideration of the second embodiment, it is also desirable that the reproducing power for verification of the phase change optical disk apparatus should be such that the C / N deterioration in reproduction by the reproducing power for verifying is within 0.5 dB.

Comparative Example 1 A conventional reproducing method was carried out using the same phase change optical disk as in the above embodiment.

First, recording was performed on the above-mentioned phase-change optical disk, and the error rate of the recorded data was measured while reproducing with the normal reproducing power Pa.
A good error rate of about 0 × 10 ⁻⁶ was obtained. Thereafter, the recorded phase change optical disk was put into an environmental tester, and left in an environment of 80 ° C. for 100 hours. Thereafter, overwriting is performed on the already recorded data of the phase change optical disk, and the error rate after overwriting is set to the reproduction power Pa.
As a result, the error rate deteriorated to about 1.0 × 10 ⁻⁴ . That is, the conventional reproducing method cannot suppress the deterioration of the archival overwrite characteristics.

(Comparative Example 2) Using the same phase change optical disk as in the above embodiment, the archival overwrite characteristics of an apparatus that performs verification after recording with a normal reproducing power Pa was examined.

When recording was performed by the above apparatus, it was determined that there was no problem when verifying the recorded data. Thereafter, the phase-change optical disk on which recording was performed by the above-described apparatus was put into an environmental tester, and was left at 80 ° C. for 100 hours.
Then, when overwriting was performed on the already recorded data of the phase change optical disk using the above apparatus, a problem occurred during verification. In other words, the apparatus that performs the verification with the normal reproduction power Pa cannot suppress the deterioration of the archival overwrite characteristics.

[0042]

According to the present invention, the archival overwrite characteristics can be prevented from deteriorating, which can greatly contribute to the increase in the density and the reliability of the optical disk.

[0043]

[Brief description of the drawings]

FIG. 1 is a diagram showing a process of a reproducing method of a phase change optical disk of the present invention.

FIG. 2 is a graph showing a verification experiment of a reproducing method of a phase change optical disk according to the present invention.

FIG. 3 is a graph showing a relationship between a reproduction power Pb and a required number of reproductions.

FIG. 4 is a graph showing a relationship between reproduction power Pb and recording data C / N deterioration.

FIG. 5 is a diagram showing a configuration of a phase change recording medium.

[Explanation of symbols]

 Reference Signs List 11 recording film 12 interference film 13 protective film 14 substrate

Claims (8)

[Claims] 1. A reproducing power Pb equal to or higher than a normal reproducing power Pa after recording in reproduction of a phase change optical disk.
A method for reproducing a phase change optical disc, wherein the method is performed at least once. 2. The phase according to claim 1, wherein a reproduction power within which C / N deterioration of a recording signal due to reproduction with said reproduction power Pb falls within 0.5 dB is used as said reproduction power Pb. How to play a changing optical disk. 3. The method according to claim 1, wherein a reproduction power 1.5 to 1.8 times the reproduction power Pa is used as the reproduction power Pb. 4. A reproducing power Pb equal to or higher than a normal reproducing power Pa at the time of verification after recording of the phase change optical disk.
4. The method according to claim 1, wherein verifying is performed after recording using the method. 5. A first means for reproducing a phase change optical disk with a normal reproduction power Pa, and a second means for reproducing the phase change optical disk with a reproduction power Pb equal to or higher than the normal reproduction power Pa. A playback device for a phase change optical disk, comprising at least: 6. A first means for reproducing a phase-change optical disk with a normal reproduction power Pa, and after performing recording after recording on the phase-change optical disk using a reproduction power Pb higher than the normal reproduction power Pa. And a second means for reproducing the phase-change optical disk to perform a verify operation. 7. The reproduction power Pb, wherein a reproduction power in which C / N deterioration of a recording signal due to reproduction with the reproduction power Pb falls within 0.5 dB is used as the reproduction power Pb. Phase change optical disc playback device. 8. The phase change optical disk reproducing apparatus according to claim 5, wherein a reproducing power 1.5 to 1.8 times the reproducing power Pa is used as the reproducing power Pb.