JPH05242541A - Magneto-optical disk - Google Patents

Abstract

(57) [Abstract] [Purpose] To increase the recording density and the C / N ratio. [Structure] The transparent substrate 2 has an upper surface on which a separation groove 4 in the track direction is formed.
And the perpendicular magnetization thin film layer 3 is formed by sputtering and vapor deposition from diagonally above. The separation groove 4 can be formed at the same time as the groove or pre-format. Since the thermal insulation between adjacent recording bits is improved by the separation groove, the density can be increased and the C / N ratio can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk used as an external storage means for a personal computer or the like.

[0002]

2. Description of the Related Art Since a magneto-optical disk is a high density rewritable type recording medium, it is used as an external storage means such as a personal computer. The conventional magneto-optical disk has a recording bit length of about 1 μm, and there is a problem that it cannot have a sufficient recording density. In order to increase the recording density, a recording bit length and a track pitch have recently been reduced. For example, in the latter case, it is necessary to improve the separation between the tracks. For this reason, the magnetic material is removed by etching and the groove is laser-annealed. Further, conventionally, it has also been performed to increase the data writing speed by various overwrite methods.

[0003]

However, in any of the conventional methods, there is a problem that the C / N ratio cannot be made sufficiently large and it is not suitable for practical use.

The present invention has been made in consideration of the above circumstances, and it is possible to obtain a sufficiently large C / N ratio even if the recording bit length and the track pitch are reduced to increase the recording density. An object is to provide a possible magneto-optical disk.

[0005]

The magneto-optical disk of the present invention is characterized by comprising a transparent substrate and a perpendicular magnetization thin film layer, and the perpendicular magnetization thin film layer is separated in the recording bit length direction. In this case, a separation groove in the recording bit length direction can be formed on the substrate, and the perpendicular magnetization thin film layer can be separated by the separation groove. Further, in the present invention, the recording bit position portion in the perpendicular magnetization thin film layer may be formed thicker than its surroundings. In this case, the concave portion is formed in the portion corresponding to the recording bit position in the substrate and the perpendicular magnetization thin film layer is formed. By forming the surface to be almost flat, the recording bit position portion of the perpendicular magnetization thin film layer can be formed thicker than its surroundings. Further, in the present invention, the perpendicularly magnetized thin film layer may be separated between recording tracks or thinned between recording tracks. In this case, lands and grooves are alternately formed through the separation grooves, and the separation grooves are formed. Thus, the perpendicularly magnetized thin film layer can be separated between the recording tracks or can be thinned between the recording tracks.

[0006]

1 and 2 show a first embodiment of the present invention. As shown in FIG. 2, the magneto-optical disk 1 has a disk-shaped outer shape. FIG. 1 shows a cross section of the disc 1 in the track direction, that is, in the recording direction (direction of arrow in FIG. 2). In FIG. 1, 2 is a transparent substrate made of transparent resin, glass, etc., and a perpendicular magnetization thin film layer 3 is formed on the upper surface thereof. A separation groove 4 is formed in the substrate 2 in the recording bit length direction. The separation groove 4 can be formed at the same time as the formation of the groove or preformat in the manufacture of the substrate 2, so that the step for forming the separation groove 4 is not necessary and the mass production of the substrate is not hindered. ..

The perpendicularly magnetized thin film layer 3 is formed by obliquely sputtering or obliquely vapor-depositing a magnetic material on such a substrate 2 (arrow 5 shown in FIG. 1). In such oblique sputtering or vapor deposition, the magnetic substance is deposited on the substrate 2 without reaching the one side wall 4a and the bottom portion 4b of the separation groove 4. Therefore, the perpendicularly magnetized thin film layer 3 is separated in the recording bit length direction through the separation groove 4, and the separation between the recording bits becomes good.

Generally, in a magneto-optical disk having no separation groove, the recording bit has a size corresponding to the wavelength and power of the laser at the time of writing data, and the perpendicular magnetic thin film layer has a poor thermal insulation property. Since heat is conducted up to the bit position, the gap must be set to a certain extent or more in order to form a uniform and stable recording bit, and there is a limit to high density. On the other hand, in the present embodiment, the separation groove 4 can be set to the minimum distance according to the wavelength of the laser, and the separation groove 4 improves the thermal insulation between the perpendicularly magnetized thin film layers 3. When using the laser of the same wavelength, the recording bit length can be about half,
The bit interval can be reduced to less than half. Therefore, it is possible to achieve a density higher than twice that of a magneto-optical disk having no separation groove. Moreover, since the separation between the recording bits is good, even if the recording and erasing of data are repeated, the unerased residue is small and the influence of the adjacent recording bits is small, so that a large C / N ratio can be achieved.

In the present embodiment, the magnetic thin film may be formed at the bottom of the separation groove due to the wraparound of the magnetic grains during the deposition of the magnetic substance, and adjacent perpendicular magnetization thin film layers 3 may be continuous with each other. Since such a thin film is very thin and the effect of heat conduction is proportional to the film thickness, the effect of this embodiment can be directly exerted even in such a case.

FIGS. 3 and 4 show a second embodiment of the present invention. As shown in FIG. 4, lands 6 and grooves 7 are alternately formed. Reference numeral 8 indicates a recording bit position on the land 6. As shown in FIG. 3, a concave portion 9 is formed in the substrate 2 corresponding to the recording bit position, and the perpendicular magnetization thin film layer 3 is formed on the upper surface of the substrate 2 including the concave portion 9. The perpendicularly magnetized thin film layer 3 is formed on the substrate 2 by depositing magnetic particles by sputtering, vapor deposition or the like, and after the formation, the surface is polished or the perpendicularly magnetized thin film layer 3 is obliquely irradiated with ions. Has a substantially flat surface. As a result, the perpendicular magnetization thin film layer of the concave portion 9 which is the recording bit position becomes the magnetic domain 12 thicker than the surrounding perpendicular magnetization thin film layer 3. The recess 9 is formed at the same time as the land and the pre-format, so that the process for forming the recess 9 does not increase.

In the above-described structure, when the light is irradiated, the magnetization is inverted and the initial domain wall 10 is formed in the perpendicularly magnetized thin film layer 3. The initial domain wall 10 contracts due to the movement as shown by the broken line arrow in FIG. The recording bit 11 reaches the periphery of the magnetic domain 12 in the concave portion 9 and becomes a stable recording bit 11. Solid arrows in FIG. 3 indicate the directions of magnetization.

Generally, there is a minimum size in a magnetic domain which is a recording bit, and in a perpendicularly magnetized thin film layer having a uniform thin film, its radius r _min is r _min = σ _w / H _c · M _S. In the above equation, σ _w is the domain wall energy per unit area, H _C is the coercive force, and M _S is the saturation magnetization. In contrast, since the thickness t _d of the thickness t _d and the magnetic domain wall 11 of the magnetic domain 12 is involved in the present _{embodiment, r min = (σ w /} H
_c · M _s ) (t _w / t _d ). Thus, in this embodiment, only the t _w / t _d small magnetic domains are present stably, correspondingly, thereby enabling higher density. Further, since it is stable with a small radius, it is difficult for extra stray magnetic domains to enter, and since the position and size of the magnetic domain are constant due to the concave portion 9, the C / N ratio can be increased.

FIG. 5 shows a third embodiment of the present invention, in which lands 6 and grooves 7 are alternately formed on a transparent substrate 1 and a gap between adjacent lands 6 and grooves 7 is provided. The groove 4 is formed. The separation groove 4 is formed in the track direction, and the land 6 and the groove 7 which are adjacent to each other are separated from each other by the separation groove 4. Such separation groove 4
Similar to the first embodiment, since it can be formed at the same time as the groove and preformat by the stamper, there is no problem in the process.

A perpendicular magnetization thin film layer 3 is formed on such a substrate 2 by spattering or vapor-depositing magnetic material particles in an oblique direction indicated by an arrow 5. The perpendicularly magnetized thin film layer 3 is formed on the upper surfaces of the land 6 and the groove 7, but since the separation groove 4 is provided between them,
The land 6 and the groove 7 which are adjacent to each other are separated from each other.

In such a structure, the isolation groove 4 provides good thermal insulation, so that the minimum track pitch can be set according to the wavelength of the laser, whereby high density can be achieved. In addition, since the influence of adjacent recording bits is small, C /
The N ratio does not decrease. In this embodiment, even if the perpendicularly magnetized thin film layer 3 is continuous at the separation groove 4 portion due to particle wraparound, the effect of heat conduction is proportional to the film thickness. It does not affect the effect. Further, in the present embodiment, even if the perpendicular magnetization thin film layer 3 between the recording tracks is formed thin, the same operation can be performed.

[0016]

As described above, according to the present invention, since the perpendicular magnetization thin film layer is separated in the recording bit length direction, the recording density can be made high and the C / N ratio can be increased. You can

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment.

FIG. 3 is a sectional view of a second embodiment.

FIG. 4 is a plan view of the second embodiment.

FIG. 5 is a sectional view of a third embodiment.

[Explanation of symbols]

 1 Magneto-optical disk 2 Substrate 3 Perpendicular magnetization thin film layer 4 Separation groove

Claims (6)

[Claims] 1. A transparent substrate and a perpendicular magnetization thin film layer are provided,
A magneto-optical disk, wherein the perpendicularly magnetized thin film layers are separated in the recording bit length direction. 2. The magneto-optical disk according to claim 1, wherein a separation groove in the recording bit length direction is formed on the substrate, and the perpendicular magnetization thin film layer is separated by the separation groove. 3. A transparent substrate and a perpendicular magnetization thin film layer are provided,
A magneto-optical disk, wherein a recording bit position portion in the perpendicularly magnetized thin film layer is formed thicker than its surroundings. 4. A recess is formed in a portion of the substrate corresponding to a recording bit position, the surface of the perpendicular magnetization thin film layer is formed to be substantially flat, and the recording bit position portion of the perpendicular magnetization thin film layer is surrounded by the depression. The magneto-optical disk according to claim 3, wherein the magneto-optical disk is formed thicker than the above. 5. A transparent substrate and a perpendicular magnetization thin film layer are provided,
A magneto-optical disk, wherein the perpendicularly magnetized thin film layer is separated between recording tracks or thinned between recording tracks. 6. The substrate has lands and grooves alternately formed via separation grooves, and the separation grooves reduce the thickness of the perpendicular magnetization thin film layer between the recording tracks or between the recording tracks. 6. The method according to claim 5, wherein
The described magneto-optical disk.