JPH10188378A - Magneto-optical recording medium and its recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for recording and reproducing the magneto- optical recording medium of high density having a guide groove for tracking and also to be reproduced with magnetic super-high resolution. SOLUTION: A land part 16 inserted in between two adjacent guide grooves 13a and 13b of the magneto-optical disk is divided into two tracks A and B along the guide grooves, and magnetic domains 23 and 24 are recorded for the tracks respectively, and then the magnetic domains recorded by using the magnetic super-high resolution are reproduced track by track. Tracking is performed by an optical head with a light spot offset from a center line between the two adjacent guide grooves to the side of either of the guide grooves by a prescribed amt. at the time of recording and reproducing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium having a guide groove for tracking and a recording / reproducing method thereof, and more particularly, to a high-density light in which a plurality of tracks are defined between the guide grooves. The present invention relates to a magnetic recording medium and a method for recording and reproducing the same.

[0002]

2. Description of the Related Art In recent years, development of optical recording media on which data can be written, such as write-once optical disks and magneto-optical disks, has been actively conducted. The information of these optical recording media is recorded and
During reproduction, various tracking techniques are used for the purpose of positioning the optical head at a desired recording or reproducing position on an optical recording medium. For example, a method in which a guide groove for tracking is formed on a substrate and the optical head follows the track center by comparing and detecting the intensity of reflected light with a photodetector that detects reflected light from the left and right sides of the track center, There is a method in which a pair of wobbled servo pits is formed on both sides of a track center and the optical head follows the track center by comparing the reflected light intensity from the servo pits. The intervals between the guide grooves and the servo pits are set based on the spot size of the laser beam so that the servo signal intensity required for the optical head to follow can be obtained and the noise is not affected by the adjacent information signal.

[0003]

By the way, with the advancement of multimedia in information equipment, an optical recording medium having a larger capacity is desired to handle a large amount of data such as image information.
To increase the storage capacity of the optical recording medium, it is conceivable to improve the recording density. As a method of improving the recording density, for example, the wavelength of the recording laser beam is shortened to increase the NA of the optical head, Accordingly, miniaturization of the recording mark has been studied.

Further, a technique for reproducing minute recording marks recorded by using such a high-density recording technique has been developed. In particular, in the magneto-optical recording method, a magnetic super-resolution method capable of reproducing only the magnetization information of the information recording layer in a specific temperature region using a temperature distribution in a reproduction light spot has been proposed. In the magnetic super-resolution method, a magneto-optical recording medium having a reproduction layer to which the magnetization information of the information recording layer in a specific temperature region is transferred separately from the information recording layer is used. By using this method, it is possible to identify and reproduce a plurality of magnetic domains included in the reproduction light spot.

As described above, techniques for recording / reproducing by miniaturizing recording marks for higher density have been studied. However, the arrangement of the guide grooves for tracking and the servo signal accompanying the miniaturization of recording marks have been studied. Not considered enough. That is, if the interval between adjacent guide grooves is reduced in accordance with miniaturization of a recording mark without reducing the reproduction light spot size, a plurality of guide grooves are included in the reproduction light spot. When a plurality of guide grooves are present in the reproduction light spot, there is a problem that it is difficult to obtain a tracking signal for causing the reproduction light spot to follow a specific track. On the other hand, since the NA of the above-mentioned optical head is determined by the wavelength of light or the like, there is a limit to the size of the reproduction light spot.

An object of the present invention is to provide a high-density magneto-optical recording medium having a guide groove for tracking, particularly a magneto-optical recording medium reproduced by magnetic super-resolution, and a recording and reproducing method thereof.

[0007]

According to a first aspect of the present invention, a guide groove for tracking is formed, and information is recorded in an area sandwiched between two adjacent guide grooves. In the recording medium, a region sandwiched between the two adjacent guide grooves is divided into at least two tracks along the guide groove direction, a magnetic domain is recorded for each track, and the recording is performed using magnetic super-resolution. A magneto-optical recording medium is provided, wherein the magnetic domain is reproduced for each track.

According to the magneto-optical recording medium of the present invention, a region sandwiched between two adjacent guide grooves, for example, a land portion is divided into at least two tracks along the direction of the guide grooves. Information is recorded and reproduced every time. Since such a track configuration is employed, a minute magnetic domain can be recorded on each track to improve the recording density. Since magnetic super-resolution is used at the time of reproduction, recording magnetic domains recorded on one track can be reliably distinguished from recording magnetic domains recorded on another adjacent track. Further, since the spacing between the guide grooves for tracking signal detection is appropriate for the spot size of the reproduction light, a stable track signal can be detected, and the optical head can reliably follow each track.

In the magneto-optical recording medium of the present invention, it is preferable that reproduction is performed by irradiating the center of each of the tracks with reproduction light having a spot diameter capable of irradiating at least the above-mentioned region. This enables high-density recording without changing the medium configuration and the optical head.

According to a third aspect of the present invention, a recording / reproducing method for a magneto-optical recording medium in which a guide groove for tracking is formed and information is recorded in an area sandwiched between two adjacent guide grooves. And irradiating the recording light spot with a predetermined amount offset from the center between two adjacent guide grooves toward any one of the guide grooves, thereby irradiating at least two information recording tracks between the two adjacent guide grooves. And a method for recording / reproducing a magneto-optical recording medium, characterized by forming

According to the recording / reproducing method for a magneto-optical recording medium of the present invention, when recording information on a magneto-optical recording medium having a guide groove for tracking, two adjacent guide grooves are used for recording light spots. By irradiating so as to be offset by a predetermined amount from the center between them, at least two information recording tracks can be defined between two adjacent guide grooves, and information is recorded and reproduced on those tracks respectively. Can be. Thus, high-density recording can be performed while detecting a stable track signal. Note that the offset amount of the guide groove or the beam center position from the center of the guide groove is determined in advance so that noise due to crosstalk between adjacent tracks when reading out the information track to be formed is reduced.

In the recording / reproducing method for a magneto-optical recording medium of the present invention, it is preferable to reproduce information recorded on each track by using magnetic super-resolution. This makes it possible to independently reproduce a recording magnetic domain sufficiently smaller than the reproduction light spot size.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments and examples of a magneto-optical recording medium and a recording / reproducing method of the present invention will be described with reference to the drawings.

Example First, using a master exposure apparatus and an injection molding machine, guide grooves having a substantially triangular cross section of 300 nm in width and 60 nm in depth were formed at intervals of 1.6 μm on a surface of 130 mm in diameter. A polycarbonate substrate having a thickness of 1.2 mm was produced. Then, the first dielectric layer, the GdFeCo magnetic layer, and the GdFe
A magneto-optical disk was manufactured by sequentially laminating a magnetic layer, a TbFeCo magnetic layer, and a second dielectric layer. Gd as recording layer
The FeCo magnetic layer, the GdFe magnetic layer, and the TbFeCo magnetic layer function as a rear aperture detection (RAD) magnetic super-resolution recording film.

The obtained magneto-optical disk was set to a wavelength of 670 nm.
m, N. A. After mounting on a magneto-optical recording / reproducing apparatus equipped with an optical head of 0.55, information was recorded and reproduced at a linear velocity of 6 m / sec using the tracking method described below. At the time of recording information, a magnetic head is used.
An external magnetic field of 0 Oe and 400 Oe was applied during reproduction.

In this embodiment, two tracks along the guide groove are defined between two guide grooves, that is, land portions having a width of 1.6 μm, and information is recorded and reproduced for each track. As the tracking servo method, a method is used in which the optical head follows a predetermined position by using a difference in the intensity of the diffracted light due to the guide groove. Usually, when using this method,
The optical head is positioned at the center between the guide grooves by performing servo control so that the absolute value of the signal intensity difference between the two photodetectors used for tracking is minimized. However, in the case of the present embodiment, the optical head is located at a position where the absolute value of the signal intensity difference from the two photodetectors 18a and 18b arranged as shown in FIG. Adjust to follow. FIG. 1B shows two photodetectors 18a and 18 at a position d in the track width direction of the optical head.
6 shows a change in the absolute value | AB |
There are two positions where the absolute value | AB | is maximized on the land portion 16 between the guide groove 13a and the guide groove 13b. By causing the optical head to follow these two locations, the land 16 between the guide groove 13a and the guide groove 13b is divided into two tracks, and information can be recorded on each track. By performing servo control so that the absolute value | AB | of the signal intensity difference is maximized as shown in FIG.
As shown in the figure, the center of the spot of the reproduction light 19 is a predetermined distance from the center of the grooves 13a and 13b, that is, the center of the land portion, in this case, a position shifted to each guide groove side by 400 nm becomes the spot center.

FIG. 3 is an enlarged plan view of a magneto-optical disk in which magnetic domains are recorded on the land 16 under the condition that the absolute value | AB | of the signal intensity difference between the two photodetectors 18a and 18b is maximized. It is shown in FIG. As shown in FIG. 2, after forming recording magnetic domains 23 of various sizes including a recording magnetic domain 23b having a magnetic domain length of 2 μm and a laser beam intensity of 7 mW on one track B partitioned by the land portion 16, the same land is formed. The other track A of the portion 16 has a magnetic domain length of 1.3 μm at a laser beam intensity of 7 mW.
Various recording magnetic domains including m recording magnetic domains 24a were formed.

Next, a magneto-optical disk having magnetic domains formed on each track as shown in FIG.
Each track was reproduced by magnetic super-resolution using the reproduction light spot No. 1. The spot diameter of the reproduction light spot 30 was 0.8 μm. The minute recording magnetic domains recorded on each track were reproduced independently of the magnetic domains recorded on the adjacent tracks, and the C / N of the reproduced signal was as high as 38 dB. In the figure, the opening due to magnetic super-resolution is indicated by a wavy line.

[Comparative Example] Except that the distance between the guide grooves 13a and 13b (the width of the land portion 16) was 0.8 μm.
A magneto-optical disk was manufactured in the same manner as in the above example. At the time of recording information, the optical head was made to follow such that the difference in signal intensity from the photodetector for detecting the tracking signal was minimized. By performing tracking in this manner, only one track is defined in the land portion 16. Thus, information was recorded on each track and reproduced using magnetic super-resolution. The gap 0.8 μm between the guide groove 13a and the guide groove 13b corresponds to a magnetic domain size (magnetic domain width) reproduced by magnetic super-resolution. In this magneto-optical disk, the noise was high with respect to the reproduced signal, and the C / N was a low value of 27 dB.

In the embodiment of the present invention, the guide groove width is optimized for the recording or reproducing light spot size.
Tracking is ensured, resulting in good C / N
It is considered that the reproduction signal was obtained by the above. In the case of the magnetic super-resolution method, since the magnetic information recorded on the information recording layer can be read only from the rear part (the central part in the case of CAD) of the reproduction light spot, crosstalk between tracks can be reduced. It can be seen that although the recording magnetic domains can be independently reproduced, the tracking operation cannot be optimized even if the guide groove interval is simply reduced because the recording and reproduction light spot diameters themselves are involved. When the recording / reproducing method of the present invention is used, it is possible to cope with a reproducing method based on magnetic super-resolution without changing the groove width of the tracking guide groove, which is optimal for high-density recording and reproducing of a magneto-optical disk. .

In the above embodiments and examples, the tracking system using the guide groove has been described as an example. However, the present invention is not limited to this system, but may be applied to a magneto-optical recording medium such as a land / groove system or a sample servo system. Can also be applied. In the case of the land / groove method, the same effect can be obtained by performing tracking such that the tracking difference signal is maximized for each of the land portion and the groove portion. In the case of the sample servo method, similar tracking can be performed based on a signal from a pit for detecting servo information.

The recording layer, the substrate and the like constituting the magneto-optical recording medium of the present invention are not limited to those described in the above embodiments, but may be made of various materials. Also, the magnetic super-resolution method used during reproduction is not limited to RAD,
CAD, FAD or a combination thereof can also be used.

In the above embodiment, the land between the guide grooves is divided into two tracks along the guide grooves. However, the land is divided into three or more tracks, and minute magnetic domains are recorded on each track. Reproduction using super-resolution is also possible.

[0024]

According to the present invention, when recording / reproducing a magneto-optical recording medium having a guide groove, a land portion between the guide grooves is divided into a plurality of tracks, and information is recorded on each track. Since the information is reproduced from, the high-density recording becomes possible while securing a sufficient tracking signal.

[Brief description of the drawings]

1A and 1B are diagrams illustrating a tracking method used when recording information on a magneto-optical disk, and FIG. 1A is a diagram illustrating a light beam irradiation position for detecting a tracking signal;
(B) is a graph showing a signal intensity difference from two photodetectors with respect to a light beam irradiation position in a track width direction.

FIG. 2 is an enlarged plan view showing an arrangement of tracks on a magneto-optical disk manufactured in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 13a, 13b Guide groove 16 Land part 17 Condensing lens 18a, 18b Photodetector 19 Light beam

Claims (4)

[Claims] 1. A magneto-optical recording medium in which a guide groove for tracking is formed and information is recorded in a region sandwiched between two adjacent guide grooves, wherein the information is recorded between the two adjacent guide grooves. Is divided into at least two tracks along the guide groove direction, magnetic domains are recorded for each track, and the recorded magnetic domains are reproduced for each track using magnetic super-resolution. Magneto-optical recording medium. 2. The reproduction is performed by irradiating the center of each track with reproduction light having a spot diameter capable of irradiating at least a region sandwiched between the two guide grooves in a track width direction. 2. The magneto-optical recording medium according to 1. 3. A recording / reproducing method for a magneto-optical recording medium in which a guide groove for tracking is formed and information is recorded in an area sandwiched between two adjacent guide grooves. Light is characterized in that at least two information recording tracks are formed between two adjacent guide grooves by irradiating a predetermined amount of offset from a center between the guide grooves toward one of the guide grooves. A method for recording / reproducing a magnetic recording medium. 4. The recording / reproducing method for a magneto-optical recording medium according to claim 3, wherein information recorded on each track is reproduced using magnetic super-resolution.