JPH0744865A - Optical information recording medium and recording and reproducing method - Google Patents

Abstract

PURPOSE:To solve the problem of the generation of an offset of a tracking error signal due to the asymmetry of the intensity distribution of a reflected light caused by the signal recording state of an adjacent track, to stabilize the tracking control and to perform stable recording/reproducing with small cross talk. CONSTITUTION:A specified signal separable from a recording signal is erased by over-writing it in a groove 7 or a land 8. This is a method for recording the specified signal in a non-recorded part between the sectors. By using optical information recording medium recording in advance the specified information on all recording tracks of both the land 8 and the groove 7 before recording the signal, stable tracking control is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing method for an optical information recording medium for recording / reproducing information at high speed and high density by using light, heat or the like.

[0002]

2. Description of the Related Art In recent years, optical discs capable of recording and reproducing information signals such as data, video and audio have been actively developed.

One of the optical discs is a so-called phase change recording medium in which the state and optical constants of the recording film material are changed by laser light irradiation, and a change in reflectance due to the change is detected to record / reproduce a signal. The phase change recording medium has been actively researched because the signal can be rewritten by reversibly changing the state of the recording film material.

As a phase change recording material, a chalcogen alloy is well known, for example, GeSbTe system, InSb.
There are Te type, GeSnTe type, InSe type, SbTe type and the like. Irradiation of these materials with a relatively high power laser beam brings them into an amorphous state, and irradiation of a laser beam with a relatively weak power brings them into a crystallized state. Since the amorphous state and the crystalline state have different optical constants, the recording signal can be reproduced as a change in the amount of reflected light due to laser irradiation.

In a recordable optical disc, a guide groove is previously formed on a substrate of the optical disc to form a track. Information signals are recorded or reproduced by focusing the laser light on the convex portions or the flat portions of the concave portions of the tracks. In a general optical disk currently on the market, an information signal is usually recorded on only one of a convex portion and a concave portion, and the other is a guard band for separating adjacent tracks. Further, generally, in an optical disc used for information processing, information is exchanged with the outside in units of a fixed length in the track direction called a sector composed of a data area and an address area.

On the other hand, research and development aiming at high-density recording is also under way, for example, not only on a guide groove for signal recording of an optical disk, but also between a guide groove (hereinafter simply referred to as a groove) and a guide groove (hereinafter simply referred to as “groove”). A method has also been proposed in which a signal is also recorded on a land (referred to as a land) to increase the recording density (for example, Japanese Patent Publication No. 63-57859). Further, in this case, if the groove shape such as the groove depth and the groove width is limited, the crosstalk from the adjacent tracks (since the signal is recorded on both the groove and the land, both are recording tracks) can be made extremely small. Have been reported (eg 19
92 Autumn Proceedings of the Applied Physics Conference Proceedings P. 948, Lecture No. 18a-T-3. Furthermore, Japanese Patent Application No. 4-79483).
By recording the signal on both the land and the groove,
It is considered that this method is a very effective technique because the conventional technique can achieve double the recording density improvement.

Further, as a tracking method for a groove provided on an optical disk, there are mainly a push-pull method and a 3-beam method.

In the push-pull method, a detector for detecting the reflected light of the laser light from the optical disc is divided into two parallel to the track direction, and a difference signal of the outputs from the two divided detectors is taken to obtain a control signal. And When the spot is at the center of the track, the amount of reflected light is symmetrical with respect to the track, so the difference signal is 0, but when the spot is off the center of the track, the difference signal is 0 because it is no longer symmetrical, so the difference signal is always 0. If it is controlled in this way, the spot will follow the track.

In the three-beam method, the laser beam is divided into three beams, and the laser beams are focused in a line on the disk.
At this time, the spot row is slightly inclined with respect to the track, for example, the main spot in the center is the center of the track, the front sub-spot is slightly to the right of the main spot, and the sub-spot further behind is the main spot. Place it so that it will slightly hit the track at the left rear of. Then, the signal is recorded / reproduced at the main spot, and the tracking detects the amount of reflected light from the front and rear sub-spots and controls the difference so as to be 0, so that the main spot follows the track. It makes it possible.

[0010]

However, in the method of recording on both the groove and the land, only the groove is
Alternatively, as compared with the method of recording only on the land, the distance between the recording tracks is about half, so that the reflected light of the laser spot is affected by the signal recording state of the adjacent track. For example, when a signal is recorded only on one of the adjacent lands when there is a laser spot on the groove, asymmetry occurs in the intensity distribution of the reflected light in the direction perpendicular to the track. In the push-pull method, this asymmetry causes an offset in the tracking error signal,
Even in the three-beam method, the tracking error signal is offset due to the difference in the amount of reflected light from the front and rear tracking sub-spots, and tracking control becomes unstable in either method, or recording is offset to one adjacent track. There is a problem that crosstalk becomes large due to reproduction.

The present invention solves the above-mentioned problems of the prior art by stabilizing tracking control of an optical information recording medium in which both convex and concave portions provided as guide grooves on a substrate are used as recording tracks, and crossing is performed. It is an object to provide a stable recording / reproducing method with a small talk.

[0012]

In order to achieve this object, a recording / reproducing method for an optical information recording medium according to the present invention comprises overwriting a specific signal which can separate a recorded signal from a recorded signal. By erasing by, a specific signal separable from the recording signal is recorded in the unwritten portion between the sectors, and a specific signal separable from the recording signal is recorded on all recording tracks of both the land and the groove before the signal is recorded. It has a means of recording the signal in advance.

[0013]

By this means, the signal recording states of the adjacent tracks become symmetrical, so that the amounts of reflected light from the adjacent tracks on the left and right become symmetrical, and the laser spot can follow the center of the track.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a sectional view of a recording area of an example of an optical disc used in the embodiment. On board 1,
The first dielectric layer 2, the recording layer 3, the second dielectric layer 4, and the reflective layer 5 are sequentially provided. Further, a transparent protective layer 6 is provided thereon. Laser light for recording, reproducing and erasing is incident from the substrate 1 side. Further, when viewed from the laser beam incident direction, the convex side of the track is the groove 7 and the concave side is the land 8.

First, a method of making a disc will be described. As a substrate 1, a 130 mm polycarbonate substrate having an uneven guide groove is used, and a ZnS-SiO ₂ mixed film having a thickness of 1300 Å is formed thereon as a first dielectric layer 2.
As the recording layer 3, a Ge ₂₂ Sb ₂₂ Te ₅₆ film having a thickness of 250 Å,
A ZnS-SiO ₂ mixed film having a thickness of 200 Å was formed as the second dielectric layer 4, and an Al film was formed as the reflective layer 5 by 1500 Å sputtering. Then, a polycarbonate protective layer 6 was provided thereon. Immediately after manufacturing this optical disk, the recording layer 3 is in an amorphous state.

The evaluation conditions of the optical disk are that the wavelength of the laser beam is 780 nm, the numerical aperture (NA) of the objective lens of the optical head used for recording / reproducing of the recording apparatus is 0.55, the linear velocity of the optical disk is 10 m / sec, and the recording power is 20 mW. Recording and reproduction were performed by a 1-beam overwrite with a bias power of 10 mW. Here, the one-beam overwrite is to record a new signal while erasing an already recorded old signal by irradiating a signal track by modulating a laser power between a recording level and an erasing level by a recording signal. Is the way. The area irradiated at the recording level becomes amorphous because it is cooled after melting regardless of whether the original state is amorphous or crystalline, and the area irradiated at the erase level rises above the crystallization temperature. It is crystallized regardless of the state and a new signal is overwritten. The tracking control was performed by the push-pull method.

The signal recording experiment was conducted as follows. First, 100 continuous tracks (that is, 50 grooves 7 and 50 lands 8) on which nothing is recorded in advance,
100 continuous tracks (that is, the groove 7
50 and land 8). 4M
Regarding the recording method of the Hz specific signal, the 4 MHz specific signal was first recorded on 50 of the grooves 7 of the selected 100 tracks, and then the 4 MHz specific signal was recorded on 50 of the lands 8. For each of them, select one groove 7 from the 100 tracks selected, and select 5MHz.
Overwrite recording of the signal. Then, the polarity of tracking is reversed and tracking is performed on the land 8, one of the lands 8 is selected, and a signal of 3 MHz is overwritten for recording. Further, the polarity of tracking is reversed and tracking is performed on the groove 7, and the unrecorded groove 7
One of the arbitrary grooves 7 is selected from among them and a signal of 5 MHz is overwritten for recording. By repeating this, signals are sequentially recorded on the groove 7 and the land 8, and 5 MHz on the groove 7 and 3 MHz on the land 8 on all 100 tracks.
The z signal was recorded.

That is, according to this recording method, when the 4 MHz specific signal is first recorded in advance, the signal is always recorded on the adjacent track to the track for overwrite recording, and the 4 MHz specific signal is first recorded. When the signal is not recorded in advance, when the signal is not recorded on the track adjacent to the track for overwrite recording, when it is recorded on both, or when it is recorded on only one, it can be used in various states. Signal recording is realized in both groove recording and land recording. The crosstalk from the adjacent track was measured on all the tracks in which the signals were recorded in this way. That is,
3 MHz from adjacent land 8 in groove 7
The crosstalk of the signal of No. 2 and the crosstalk of the signal of 5 MHz from the adjacent groove 7 in the land 8 were measured.

As a result, the crosstalk was -30 dB when the 4 MHz specific signal was recorded first, but the crosstalk was recorded when the 4 MHz signal was not recorded first. -25dB to -32d
A value that was different from B was obtained.

When the specific signal of 4 MHz is not recorded in advance, the value of the crosstalk that is different or larger than that when the specific signal is first recorded is obtained in one of the adjacent tracks. When the signal is recorded only on the track, it is considered that the offset of tracking occurred and the signal was recorded / reproduced in the state where the laser spot was not located at the center of the track.

Considering how the rewritable optical disc is actually used, a signal once recorded may be erased over all or a part of the sectors, or recording may be performed only on a part between the sectors. Write,
It is considered that the recording state of the signal on the track adjacent to the track on which the signal is recorded varies. When a signal is recorded on only one of the adjacent tracks, a tracking offset occurs and the signal is not recorded / reproduced without the laser spot located at the center of the track.
In addition to previously recording a specific signal that can be separated from the recording signal as in the present embodiment, when overwriting and erasing, the recording signal is erased by overwriting the specific signal. It is also considered effective to record the specific signal in the unwritten portion of the sector signal.

In this embodiment, polycarbonate is used as the substrate 1, but glass, quartz, or
Polymethylmethacrylate or the like may be used, or the protective layer 6
Although polycarbonate is used as the protective layer 6, the protective layer 6 may be formed by dissolving and coating a resin in a solvent and drying, or by adhering a resin plate with an adhesive.
Although a Te-based material is used, the recording layer 3 is SbTe-based, GeSb
TeSe system, GeSbTePd system, TeGeSnAu
System, AgSbTe system, GeTe system, GaSb system, InS
e-based, InSb-based, InSbTe-based, InSbSe-based,
InSbTeAg-based material may be used, the dielectric layer 2,
Although a ZnS-SiO ₂ mixed film was used as 4, SiO ₂ ,
SiO, TiO ₂ , MgO, Ta ₂ O ₅ , Al ₂ O ₃ , Ge
O ₂ , Si ₃ N ₄ , BN, AlN, SiC, ZnS, Zn
Se, ZnTe, PbS or the like or a mixture thereof may be used, and Al is used as the reflective layer 5, but Au, C
It goes without saying that a material containing a metal material such as u, Cr, Ni, or Ti as a main component, or a mixture thereof, or a dielectric multilayer film having a large reflectance at a predetermined wavelength may be used.

Although the structure having the reflective layer 5 and the protective layer 6 is used in this embodiment, it is needless to say that the present invention is also effective for a recording medium having a structure in which the reflective layer 5 and the protective layer 6 are not provided.

In the present embodiment, the 4 MHz signal is used as the specific signal separable from the recording signal. However, the specific signal may be any signal separable from the recording signal. Alternatively, it goes without saying that a specific signal for uniformly amorphizing the half width of the groove 7 may be used. Further, when recording / reproducing with an EFM signal, it is possible to separate from the recording signal by using a channel bit pattern having a channel bit pattern not used in the EFM modulation method as the specific signal.

[0025]

As described above, according to the present invention, a specific signal separable from a recording signal is erased by overwriting, the specific signal is recorded in an unrecorded portion between sectors, and a signal is recorded. Before landing 8 and groove 7
By recording the specific signal in advance on all recording tracks of both of the above, stable tracking control and stable recording / reproduction with small crosstalk can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining an optical information recording medium according to a first embodiment of the present invention.

[Explanation of symbols]

 1 Substrate 2 First Dielectric Layer 3 Recording Layer 4 Second Dielectric Layer 5 Reflective Layer 6 Protective Layer 7 Groove 8 Land

Claims (4)

[Claims] 1. An optical system in which both a convex portion and a concave portion provided as guide grooves on a substrate are used as recording tracks, and a recording thin film layer which causes a change which can be optically detected by irradiation of laser light is provided on the substrate. Recording / reproducing method for an optical information recording medium, wherein a signal already recorded is erased by overwriting a specific signal separable from a recording signal. . 2. An optical system in which both a convex portion and a concave portion provided as guide grooves on a substrate are used as recording tracks, and a recording thin film layer which causes a change which can be optically detected by irradiation of laser light is provided on the substrate. A recording / reproducing method for an optical information recording medium, wherein a specific signal separable from a recording signal is recorded in an unwritten portion between sectors. 3. An optical system in which both a convex portion and a concave portion provided as guide grooves on a substrate are used as recording tracks, and a recording thin film layer which produces a change which can be optically detected by irradiation of laser light is provided on the substrate. A recording / reproducing method for a specific information recording medium, characterized in that before recording a signal, a specific signal separable from the recording signal is recorded in advance on all recording tracks of both the convex portion and the concave portion. Recording and reproducing method for optical information recording medium. 4. An optical system in which both a convex portion and a concave portion provided as guide grooves on a substrate are used as recording tracks, and a recording thin film layer which causes a change which can be optically detected by irradiation of laser light is provided on the substrate. A recording / reproducing method for a specific information recording medium, characterized in that before recording a signal, a specific signal separable from the recording signal is recorded in advance on all recording tracks of both the convex portion and the concave portion. And an optical information recording medium.