JP3094740B2 - Optical information recording medium and recording / reproducing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

As one type of optical disk, there is a so-called phase change recording medium in which the state and optical constant of a recording film material are changed by laser light irradiation, and a change in reflectivity is detected to record and reproduce a signal. Phase change recording media have been actively studied because signals can be rewritten by reversibly changing the state of a recording film material.

As a phase change recording material, a chalcogen alloy is well known, for example, GeSbTe, InSb
There are Te type, GeSnTe type, InSe type, SbTe type, and the like. These materials become amorphous by irradiation with laser light having relatively high power, and the amorphous region becomes crystallized by irradiation with laser light having relatively low power. Since the optical constant is different between the amorphous state and the crystalline state, a recorded signal can be reproduced as a change in the amount of reflected light due to laser irradiation.

[0005] In a recordable optical disk, a guide groove is previously cut into a substrate of the optical disk to form a track. The recording or reproduction of the information signal is performed by focusing the laser beam on the flat portion of the convex portion or the concave portion of the track. In a general optical disk currently on the market, an information signal is usually recorded only on one of a convex portion and a concave portion, and the other is a guard band for separating adjacent tracks. Further, in an optical disk generally used for information processing, information is exchanged with the outside in units of a fixed length in a track direction called a sector including a data area and an address area.

On the other hand, research and development aiming at high-density recording are also proceeding. For example, not only on a guide groove for signal recording on an optical disk but also between a guide groove (hereinafter simply referred to as a groove) (hereinafter simply referred to as a groove). A method of recording a signal on a land (referred to as a land) to increase the recording density has been proposed (for example, Japanese Patent Publication No. 63-57859). Further, in this case, if the groove shape such as the groove depth and groove width is limited, crosstalk from an adjacent track (signal is recorded on both the groove and the land, and both are recorded tracks) can be extremely reduced. Have been reported (eg, 19
Proceedings of the autumn meeting of the Japan Society of Applied Physics 92 948, lecture number 18a-T-3. Furthermore, Japanese Patent Application No. 4-79483).
By recording signals on both lands and grooves,
This method is considered to be a very effective technology because the recording density can be doubled with the conventional technology.

[0007] As a tracking method for a groove provided on an optical disk, there are mainly a push-pull method and a three-beam method.

In the push-pull method, a detector for detecting the reflected light of a laser beam from an optical disk is divided into two parts in parallel with the track direction, and a difference signal between outputs from the two divided detectors is obtained, which is used as 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 that the difference signal is 0. With this control, the spot follows the track.

In the three-beam method, a laser beam is divided into three beams, each of which is focused on a disk in a line.
At this time, the row of spots is slightly inclined with respect to the track.For example, the center main spot is set to the center of the track, the front sub spot is slightly to the right of the main spot, and the rear sub spot is set to the main spot. At the left rear of the car, slightly over the truck. Signals are recorded and 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 that the difference becomes 0, so that the main spot follows the track. Is what makes it possible.

[0010]

However, in the method of recording on both the groove and the land, only the groove is used.
Alternatively, since the distance between recording tracks is reduced to about half compared to the method of recording only on lands, the laser spot covers a range larger than the track width, that is, adjacent tracks.
Hangs on part of the rack. Therefore, the laser spot is affected by the reflected light depending on the signal recording state of the adjacent track. For example, if there is a laser spot on a groove and a signal is recorded only on one of the adjacent lands, an asymmetry in the intensity distribution of the reflected light in a direction perpendicular to the track occurs. In the case of the push-pull method,
This asymmetry causes an offset in the tracking error signal, and the three-beam method also causes an offset in the tracking error signal due to the difference in the reflected light amounts of the front and rear tracking sub-spots. However, there is a problem in that recording or reproduction is performed with a deviation from one adjacent track, and crosstalk increases.

The present invention solves the above-mentioned conventional problems and stabilizes the tracking control of an optical information recording medium in which both a convex portion and a concave portion provided as a guide groove on a substrate are used as recording tracks, and the cross control is achieved. An object of the present invention is to provide a stable recording and reproducing method with small talk.

[0012]

In order to achieve this object, a recording / reproducing method according to the present invention comprises forming a guide groove on a substrate.
Both the convex and concave portions provided as recording tracks
Optically detectable by laser light irradiation on the substrate
Optical information recording medium with a recording thin film layer
A recording and reproducing method, wherein a recording signal for recording information is recorded.
And a specific signal that can be distinguished from the
The information signal which has already been recorded
The information signal by overwriting the signal.
It is characterized by leaving . In addition, the second description of the present invention
The recording / reproducing method uses a convex part provided as a guide groove on the substrate.
The recording track is used for both the
Recording that produces an optically detectable change upon exposure to light
A recording / reproducing method for an optical information recording medium provided with a thin film layer.
Therefore, it can be distinguished from the recording signal for recording information.
Recording the constant signal between sectors of the optical recording medium.
The signal is recorded in the area where no signal is recorded.
You . Further, a third recording / reproducing method according to the present invention further comprises a substrate
Record both convex and concave portions provided as guide grooves above
A track, and illuminate the substrate with laser light
Optics with a recording thin film layer that produces a biologically detectable change
Recording and reproducing information on an information recording medium.
A recording signal for recording on the optical information recording medium.
Before the recording, the specific signal that can be distinguished from the recording signal is
Be recorded on all recording tracks, both
And features. Further, the optical information recording medium according to the present invention
The body consists of convex and concave portions provided as guide grooves on the substrate.
Irradiation of laser light on the substrate with both recording tracks
A recording thin film layer that produces an optically detectable change
An optical information recording medium provided for recording information.
The specific signal that can be distinguished from the recording signal for
Recorded on both recording tracks of both
And features .

[0013]

By this means, what is always on adjacent tracks
Are recorded, and signals from adjacent tracks on the left and right
The reflected light amount becomes symmetric, and the laser spot can follow the center of the track. The information you want to record
When playing back a track on which a recording signal containing information is recorded.
The effect of crosstalk from adjacent tracks
As a result, the quality of the reproduced signal is improved.

[0014]

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

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

The evaluation conditions of the optical disk are as follows: the wavelength of the laser beam is 780 nm, the numerical aperture (NA) of the objective lens of the optical head used for recording and reproduction of the recording device 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 one-beam overwriting with a bias power of 10 mW. Here, one-beam overwriting is to record a new signal while erasing an already recorded old signal by modulating a laser power between a recording level and an erasing level by a recording signal and irradiating the signal track. Is the way. The region irradiated at the recording level becomes amorphous because it is cooled after melting, regardless of whether the original state is an amorphous state or a crystalline state, and the region irradiated at the erasing level rises to a temperature higher than the crystallization temperature. Regardless of the state, it crystallizes and a new signal is overwritten. The tracking control was performed by a push-pull method.

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

That is, according to this recording method, when a specific signal of 4 MHz is previously recorded in advance, the signal is always recorded on a track adjacent to the track to be overwritten, and the specific signal of 4 MHz is first recorded. In the case where the signal is not recorded in advance, the signal is not recorded in the track adjacent to the track to be overwritten, the signal is recorded in both, or the signal is recorded only in one of the various states. Signal recording is realized in both groove recording and land recording. In all the tracks on which the signal was recorded in this manner, the crosstalk from the adjacent track was measured. That is,
3 MHz from adjacent land 8 in groove 7
In the land 8, the crosstalk of the signal of 5 MHz from the adjacent groove 7 was measured.

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

When a specific signal of 4 MHz was not recorded in advance, a variation or a large crosstalk value was obtained as compared with the case where the specific signal was recorded first. If the signal is recorded only in the signal, it is considered that a tracking offset has occurred and the signal has been recorded and reproduced in a state where the laser spot is not located at the center of the track.

Considering the actual use of a rewritable optical disk, it is possible to erase a once-recorded signal over all or a part of a sector or to record a signal only on a part of a sector. When writing,
It is considered that the recording state of the signal on the track adjacent to the track for recording the signal is various. When a signal is recorded on only one of the adjacent tracks, a tracking offset occurs, and the signal is not recorded / reproduced in a state where the laser spot is not located at the center of the track.
As in the present embodiment, not only the specific signal that can be separated from the recording signal is recorded in advance, but also in the case of 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 unrecorded portion of the signal of the sector.

In this embodiment, the substrate 1 is made of polycarbonate. However, glass, quartz, or
Polymethyl methacrylate may be used, or the protective layer 6
The protective layer 6 may be formed by dissolving a resin in a solvent and applying and drying the resin, or by bonding a resin plate with an adhesive, or by using GeSb as the recording layer 3.
The recording layer 3 was made of SbTe, GeSb,
TeSe system, GeSbTePd system, TeGeSnAu
System, AgSbTe system, GeTe system, GaSb system, InS
e system, InSb system, InSbTe system, InSbSe system,
An InSbTeAg-based material may be used.
As 4, it was ZnS-SiO ₂ mixed film but, 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, etc. or a mixture thereof may be used. Al is used as the reflective layer 5.
Needless to say, a material mainly containing a metal material such as u, Cr, Ni, Ti or a mixture thereof, or a dielectric multilayer film having a large reflectance at a predetermined wavelength may be used.

Although the present embodiment has a structure having the reflective layer 5 and the protective layer 6, it goes without saying that the present invention is also effective for a recording medium having a structure without the reflective layer 5 and the protective layer 6.

In this embodiment, a 4 MHz signal is used as a specific signal which can be separated from the recording signal. However, the specific signal may be any signal which can be separated from the recording signal. Alternatively, it is needless to say that a specific signal for uniformly amorphizing half the width of the groove 7 may be used. In the case of recording / reproducing with an EFM signal, if a channel bit pattern not used in the EFM modulation method is used as a specific signal, it can be separated from a recording signal.

[0025]

As described above, according to the present invention, a specific signal which can be separated from a recording signal is erased by overwriting, the specific signal is recorded in an unrecorded portion between sectors, and a signal is recorded. Land 8 and groove 7 before doing
By previously recording the specific signal on all the recording tracks of both, the tracking control can be stabilized and stable recording and reproduction with small crosstalk can be realized.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st dielectric layer 3 Recording layer 4 2nd dielectric layer 5 Reflective layer 6 Protective layer 7 Groove 8 Land

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-98629 (JP, A) JP-A-3-198222 (JP, A) JP-A-7-44872 (JP, A) JP-A-2- 35637 (JP, A) JP-A-61-29423 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 7/30

Claims (4)

(57) [Claims] 1. An optical system comprising: a recording track formed by both a convex portion and a concave portion provided as guide grooves on a substrate; and a recording thin film layer provided on the substrate to generate a change which can be optically detected by irradiation of a laser beam. Signal for recording and reproducing information on a specific information recording medium, wherein the specific signal can be distinguished from a recording signal for recording information
Overwrites the already recorded information signal
Thereby erasing the information signal . 2. An optical system comprising: a recording track formed by both a convex portion and a concave portion provided as a guide groove on a substrate; and a recording thin film layer on the substrate, the recording thin film layer having a change which can be optically detected by irradiation of a laser beam. Signal for recording and reproducing information on a specific information recording medium, wherein the specific signal can be distinguished from a recording signal for recording information
Wherein the recording signal between sectors of the optical recording medium is
A recording / reproducing method for an optical information recording medium, characterized in that recording is performed in a part where no information is recorded. 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 is provided on the substrate, the recording thin film layer having a change which can be detected optically by irradiation of a laser beam. A method for recording / reproducing information on an optical information recording medium, comprising: recording a signal for recording information on the optical information recording medium.
Before recording on the body, identification that can be distinguished from the recording signal
The signal is recorded on all recording tracks, both convex and concave.
Method of recording and reproducing an optical information recording medium characterized that you record. Both wherein projections and recesses provided as a guide groove on the substrate as a recording track, provided with a recording thin film layer resulting in a change that can detect optically by irradiation of the laser beam on the substrate optical Information recording medium, a specific signal that can be distinguished from a recording signal for recording information
Is applied to all the recording tracks of both the convex and concave portions in advance.
An optical information recording medium characterized by being recorded.