JPH11120620A - Phase transition type information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit the reproduction of a phase transition type disk on the premise of a push-pull system, such as DVD-RAM, even by the reproduction-only optical disk which deals with only the DPD(phase difference detection) method. SOLUTION: Recording layers 3 are formed by successively laminating at least an interference film 3d, a recording film 3c and a heat insulating film 3b. The thickness of the interference film 3d is formed to approximately 125 to 165 nm when the thickness of the recording film 3c is approximately 17 nm, that of the heat insulating film 3b approximately 20 nm and that of the heat radiating film 3a is approximately 120 nm. As a result, the variation in the DPD signal sensitivity at defocusing of ±0.5 μm is suppressed to <=±30% and the fluctuation width may be suppressed to <=60%. The reproduction of the phase transition type information recording medium is made possible even by the optical disk device dealing with only the phase difference defection method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type information recording medium in which an information recording medium such as a DVD-RAM capable of recording and reproduction can be reproduced by a reproduction-only optical disk device.

[0002]

2. Description of the Related Art Today, as a next-generation information recording medium having a high information recording density (hereinafter, abbreviated as a disc), a DVD which is a so-called standard has been expected. Such DV
D is a DVD-ROM that can perform only reproduction, a DVD-R that can perform additional recording and reproduction, and a DV that can perform recording, reproduction, and erasure.
D-RAM and the like. There are a read-only optical disk device corresponding to the type of each disk and an optical disk device capable of recording and reproducing.

[0003] A tracking method in a read-only optical disk device is a DPD (Differential) method.
A phase detection (phase difference detection method) is adopted, and a push-pull method is scheduled as a tracking method in an optical disk device capable of recording and reproducing.

[0004] Information recording on a read-only disk such as a DVD-ROM is performed by forming pits (holes) in a recording layer, and the depth of the pits is reflected by a peripheral area and an internal area of the pit. The phase difference of the laser light thus set is set to be approximately 180 degrees.

[0005] A tracking signal is obtained by using a DPD method to receive reflected light from a pit array by a light receiving element divided into four parts, and obtaining a sum signal of photoelectric conversion signals from two light receiving areas located on a diagonal line. , Are detected from the phase difference between the respective sum signals (see Japanese Patent Publication No. 2-56734). That is, detection of a tracking signal by the DPD method is performed by detecting a change in a diffraction pattern from a pit row.

On the other hand, information recording on a phase-change disk such as a DVD-RAM is performed by forming a mark by partially changing the crystal state of a recording layer in a spirally formed groove area. I have.

The tracking signal is detected by dividing the light receiving element into two parts using the push-pull method, and comparing the symmetry of the photoelectric conversion signals output from the two light receiving areas (Japanese Patent Publication No. 63-163). -57859).

[0008]

SUMMARY OF THE INVENTION However, DPD
If a tracking signal is detected on an information recording medium having a groove formed thereon, such as a DVD-RAM, the diffraction pattern may be changed by the groove, and the diffraction pattern may be sharp as in a DVD-ROM. Can not get the change.

That is, since a tracking method is different between a read-only optical disk device and an optical disk device capable of recording and reproduction, a read-only optical disk device uses a DVD-R
There is a problem that it is not possible to reproduce a disk that can record and reproduce information such as AM.

In this case, the read-only optical disc device is
It is possible to provide a tracking circuit so that both the PD method and the push-pull method can be used, but in such a case, there is a problem that the optical disk device becomes expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a phase change type information recording medium capable of reproducing a disk such as a DVD-RAM in a read-only optical disk apparatus which is compatible only with the DPD method. .

[0012]

According to a first aspect of the present invention, a recording layer is sandwiched between a protective film having a spiral groove and a transparent substrate, and a recording layer of the groove is provided. In a phase change type information recording medium in which information is recorded and reproduced by irradiating a laser beam to form marks and non-marks, the recording layer changes the crystalline state at least by the irradiation of the laser beam to change the mark and the mark. A recording film on which a non-mark is formed, a heat retaining film for controlling the amount of heat radiation so that the temperature of the recording film becomes an appropriate temperature when a laser beam is irradiated on the recording film, and a recording film. An interference film that changes the reflectivity of the laser light reflected by the marks and non-marks formed on the recording medium and the phase of the reflected light; a heat insulating film and an interference film are laminated with the recording film interposed therebetween; Interference film Disposed on the laser beam incident side. When information is reproduced by an optical disk apparatus that supports only the phase difference detection method, when the optical disc apparatus has a defocus in the range of ± 5 μm, the sensitivity variation of the phase difference detection signal is in a range of 30% or less. The fluctuation range of the signal is 60
%, Wherein the thicknesses of the interference film, the recording film, and the heat insulating film are set to fall within the range of%.

According to a second aspect of the present invention, the recording film is made of Ag-
It is composed of ln-Sb-Te, and the atomic component ratio is approximately 4% for Ag, 7% for In, 61% for Sb, 28 for Te.
%.

The invention according to claim 3 is characterized in that the thickness of the interference film is set to approximately 125 to 165 nm.

According to a fourth aspect of the present invention, the thickness of the recording film is set to approximately 16 to 33 nm.
4. The phase-change recording medium according to any one of claims 3 to 3.

According to a fifth aspect of the present invention, the thickness of the heat insulating film is 1
5. The phase-change recording medium according to claim 1, wherein the thickness is set to 6 to 28 nm.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a phase-change disk capable of recording, reproducing and erasing according to the present invention. FIG. 1 (a)
FIG. 1B is a cross-sectional view of the phase change type disc, and FIG.
Shows a plan view of the recording layer. Also, FIG.
FIG. 3 is a partial cross-sectional view illustrating a configuration of a recording layer illustrated in FIG.

In the phase change type disk 1 according to the present invention, the recording layer 3 is sandwiched between the protective film 2 and the transparent substrate 4, and the groove 9 having a predetermined depth is formed from the center to the outer periphery of the phase change type disk 1. Are formed spirally. In the following description, the area between the grooves 9 is defined as the land 8.
Called.

The recording layer 3 is composed of a heat radiation film 3 made of Al-Ti.
a, insulation film 3b made of ZnS-SiO ₂ or the like, Ag-I
The recording film 3c made of a quaternary system of n-Sb-Te, ZnS-
An interference film 3d made of SiO ₂ or the like is sequentially laminated.

For recording and erasing of information, the laser beam condensed by the objective lens is incident on the recording layer 3 from the transparent substrate 4 side, and the mark 6 is formed on the recording layer 3 of the groove 9. This is performed by erasing the formed mark 6 to form a non-mark 7. Reproduction of information is performed by detecting a change in light intensity of reflected light from the mark 6 and the non-mark 7.

At this time, the recording film 3 is irradiated with the laser beam.
Although the temperature of c rises, if the temperature rises more than necessary, the recording characteristics of the recording film 3c may fluctuate and proper recording may not be performed. To prevent such a situation,
A heat radiation film 3a and a heat insulation film 3b are provided.
Promotes heat radiation or heat diffusion, and the heat insulating film 3b controls the amount of heat radiated by the heat radiating film 3 to control the recording film 3c.
The temperature at the time of recording is set in an appropriate temperature range.

As described above, information is recorded on the recording layer 3.
Is formed by forming a mark 6 and a non-mark 7 on the recording layer 3 by condensing a laser beam on the recording layer 3. The mark 6 and the non-mark 7 have different crystal states. That is, when the recording film 3c is heated by the laser beam and then rapidly cooled, the recording film 3c becomes amorphous and the mark 6 is formed. At a slower cooling rate, the recording layer 3 is crystallized and the non-mark 7 is formed. Is done. The reflectivity of the mark 6 and the non-mark 7 changes depending on the crystalline state, and the reflectivity is lower in the amorphous state.

Therefore, in the present invention, the reflectance and the phase of the mark and the non-mark are adjusted by optimizing the material and the film thickness of the heat radiation film 3a, the heat insulation film 3b, the recording film 3c and the like which constitute the recording layer 3. Under the control, the phase-change disk 1 on which the group 9 is formed can be reproduced even by a reproduction-only DVD-ROM device which is compatible only with the DPD method.

Incidentally, in a DVD-ROM device, since the defocus usually occurs ± 0.5 μm, the variation of the DPD signal sensitivity in the defocus range is suppressed to ± 30% or less, or the variation width of the DPD signal is 60% or less. Need to be suppressed.

3 to 5 show that the defocus state is ±
Heat radiation film 3a, heat insulation film 3b, recording film 3c at 0.5 μm
FIG. 7 is a diagram illustrating an experimental result of DPD signal sensitivity in a case where the thickness of any one of the interference film 3d and the interference film 3d is changed as illustrated in FIG.

As shown in FIG. 3, when the recording film 3c is approximately 17 nm, the heat retaining film 3b is approximately 20 nm, and the heat radiation film 3a is approximately 120 nm, the variation in DPD signal sensitivity with ± 0.5 μm defocus is less than ± 30% or DPD. 60 signal fluctuations
%, The thickness of the interference film 3d is set to about 125 to 1
It is understood that it is sufficient to set the thickness to 65 nm.

Similarly, from FIG. 4, when the interference film 3d is approximately 165 nm, the heat insulation film 3b is approximately 20 nm, and the heat radiation film 3a is approximately 120 nm, the thickness of the recording film 3c is 16 to 33 nm.
You can see what you should do.

Further, from FIG. 5, the interference film 3d is substantially 16
5 nm, the recording film 3c is approximately 17 nm, and the heat radiation film 3a is approximately 12 nm.
It can be seen that when the thickness is 0 nm, the thickness of the heat insulating film 3b should be 16 to 28 nm.

It is known that the DPD signal sensitivity is independent of the thickness of the heat radiation film 3a made of AI-Ti.

The atomic composition ratio of Ag-In-Sb-Te is approximately 4% for Ag, 7% for In, 61% for Sb,
If e: 28%, very good recording / reproducing characteristics can be obtained.

FIG. 8 shows a conceptual configuration diagram of a general optical disk device. The optical disk device includes a laser source 21 for generating and emitting a laser beam,
Laser beam from the disk and the phase-change disk 1
The mirror light which is reflected by the half mirror 22, condenses the laser light reflected by the half mirror 22 to form a laser spot on the phase-change disk 1, and is converged by the objective lens 23 to form the half mirror 22. Light-receiving element 24 that receives reflected light from phase-change type disk 1 that has passed through the optical disk 1 and performs photoelectric conversion, detects a photoelectric conversion signal output from light-receiving element 24, and detects a tracking signal, a servo signal of a focus signal, and a reproduction signal. A servo circuit 26 for receiving a servo signal from the detection circuit 25 and controlling a servo mechanism 29 such as a tracking motor or a tracking coil and a focus coil;
An information reproducing circuit 27 that receives a reproduction signal from the detection circuit 25 and reproduces information is provided.

The laser light emitted from the laser source 21 is reflected by the half mirror 22 and is reflected by the objective lens 23.
And is condensed by the objective lens 23 and irradiates the recording layer 3 of the phase-change disk 1.

On the other hand, the reflected light from the phase change disk 1 is converged by the objective lens 23, passes through the half mirror 22, and is received by the light receiving element 24.

Thus, the photoelectric conversion signal output from the light receiving element 24 is input to the detection circuit 25, and the detection circuit 25 supplies the servo signal supplied to the servo circuit 26 and the information reproduction signal supplied to the information reproduction circuit 27. A signal is output.

At this time, if the optical disk device is a reproduction-only device, the light receiving element 24 is divided into four parts.
According to the DPD method, the detection circuit 25 is located on a diagonal line.
The sum signal of the photoelectric conversion signals from the two light receiving areas is obtained, the tracking signal is detected from the phase difference between the sum signals, and the tracking signal is output to the servo circuit 26.

When the optical disk apparatus is a recording / reproducing apparatus, the light receiving element 24 is divided into two parts, and the detection circuit 25 operates in accordance with the push-pull method to symmetrically convert the photoelectric conversion signals output from the two light receiving areas. By comparing the characteristics, the tracking signal is detected and output to the servo circuit 26.

The phase change type disk 1 according to the present invention comprises:
As described above, the configuration of the recording layer 3 is optimally set so that the DPD method can be applied, and the groove 9 is provided so that the push-pull method can be applied. In addition, it is possible to reproduce even an optical disk device dedicated to reproduction.

The servo circuit 26 that has received the servo signal from the detection circuit 25 controls the driving of the servo mechanism 29 based on the servo signal. Thereby, tracking control and focus control are performed.

[0039]

As described above, when a recording layer is formed by sequentially laminating at least an interference film, a recording film, and a heat insulating film, and information is reproduced by an optical disk apparatus compatible only with the phase difference detection method, The defocus of the optical disk device is ± 5
The thicknesses of the interference film, the recording film, and the heat insulation film were set so that the sensitivity variation of the phase difference detection signal was in the range of 30% or the variation range of the signal was within the range of 60% in the range of μm. Therefore, it is possible to reproduce the phase-change type information recording medium even in an optical disk device that supports only the phase difference detection method.

The recording film is composed of Ag-In-Sb-Te, and the respective atomic component ratios are approximately Ag: 4%, In: 7%,
Since Sb: 61% and Te: 28%, extremely good recording / reproducing characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a phase change type information recording medium applied to the description of an embodiment of the present invention, wherein FIG.
(B) is a partial plan view.

FIG. 2 is a schematic cross-sectional view showing an enlarged main part of the invention.

FIG. 3 is a diagram illustrating a change in a DPD sensitivity signal when the thickness of an interference film is changed.

FIG. 4 is a diagram illustrating a change in a DPD sensitivity signal when the thickness of a recording film is changed.

FIG. 5 is a diagram illustrating a change in a DPD sensitivity signal when the thickness of a heat insulating film is changed.

FIG. 6 is a diagram showing a configuration of a general optical disk device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Phase change type disk 3 Recording layer 3a Heat dissipation film 3b Heat insulation film 3c Recording film 3d Interference film 8 Land 9 Groove

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[Procedure amendment]

[Submission date] November 28, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

[0012]

According to a first aspect of the present invention, a recording layer is sandwiched between a protective film having a spiral groove and a transparent substrate, and a recording layer of the groove is provided. In a phase change type information recording medium in which information is recorded and reproduced by irradiating a laser beam to form marks and non-marks, the recording layer changes the crystalline state at least by the irradiation of the laser beam to change the mark and the mark. A recording film on which a non-mark is formed, a heat retaining film for controlling the amount of heat radiation so that the temperature of the recording film becomes an appropriate temperature when a laser beam is irradiated on the recording film, and a recording film. An interference film that changes the reflectivity of the laser light reflected by the marks and non-marks formed on the recording medium and the phase of the reflected light; a heat insulating film and an interference film are laminated with the recording film interposed therebetween; Interference film Disposed on the laser beam incident side. When information is reproduced by an optical disk device that supports only the phase difference detection method, when the defocus of the optical disk device is in the range of ± 0.5 μm , the sensitivity variation of the phase difference detection signal is 30%. The thickness of the interference film, the recording film, and the heat insulating film is set so that the range or the fluctuation range of the signal is within 60%.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

The insulation film 3b recording layer 3 is made of a heat radiation film 3a, ZnS-SiO ₂ or the like made of Al-Ti, etc., Ag-
In-Sb-Te quaternary recording film 3c, ZnS
Interference film 3d consisting -SiO _2, etc. is formed are sequentially laminated.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

It should be noted that the DPD signal sensitivity depends on whether it is AI-Ti or the like.
The thickness of the al become heat radiation film 3a is found to be independent.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction contents]

[0039]

As described above, when a recording layer is formed by sequentially laminating at least an interference film, a recording film, and a heat insulating film, and information is reproduced by an optical disk apparatus compatible only with the phase difference detection method, The defocus of the optical disk device is ±
When in the range of 0.5 μm , the sensitivity variation of the phase difference detection signal is in the range of 30% or the variation width of the signal is 60%.
Since the thicknesses of the interference film, the recording film, and the heat insulating film are set so as to fall within the range, the phase change type information recording medium can be reproduced even in an optical disk device that supports only the phase difference detection method.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 7/24 535 G11B 7/24 535C 535D 535G B41M 5/40 B41M 5/26 H

Claims (5)

[Claims] 1. A recording layer is sandwiched between a protective film having a spiral groove and a transparent substrate, and a laser beam is applied to the recording layer of the groove to form a mark and a non-mark, thereby recording information. In a phase-change type information recording medium on which information is reproduced by receiving reflected light from the mark and the non-mark, at least the recording layer changes the crystal state by irradiation with a laser beam to reflect the reflected light. A recording film on which the marks and non-marks having different ratios are formed; and irradiating the recording film with a laser beam to form the marks and non-marks so that the temperature of the recording film becomes an appropriate temperature. A heat insulating film for controlling the amount of heat radiation, and an interference film for changing the reflectance of laser light reflected by the marks and non-marks formed on the recording film and the phase of the reflected light; Sandwich When the thermal insulation film and the interference film are laminated and the interference film is disposed on the laser beam incident side and the information is reproduced by an optical disk device that supports only the phase difference detection method, Defocus ±
The thicknesses of the interference film, the recording film, and the heat insulating film are set so that the sensitivity variation of the phase difference detection signal is in the range of 30% or the variation width of the signal is within the range of 60% in the range of 5 μm. A phase change type information recording medium characterized by the above-mentioned. 2. The recording film according to claim 1, wherein said recording film is made of Ag-ln-Sb-Te.
And the atomic component ratio is approximately Ag: 4%, l
2. The phase change type information recording medium according to claim 1, wherein n: 7%, Sb: 61%, Te: 28%. 3. The thickness of the interference film is approximately 125 to 165 n.
3. The phase change type information recording medium according to claim 1, wherein m is set to m. 4. The phase change type information recording medium according to claim 1, wherein the thickness of the recording film is set to approximately 16 to 33 nm. 5. The phase change type information recording medium according to claim 1, wherein the thickness of the heat insulating film is set to 16 to 28 nm.