JPH07105086B2 - Information recording method on magneto-optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a magneto-optical disk, the present invention superimposes a recording laser beam or an erasing laser beam on a laser beam higher than a reproducing laser beam in order to reduce the laser power for recording and erasing. By doing so, the peak value of the recording laser beam or the peak value of the erasing laser beam is lowered.

[Industrial application field]

The present invention relates to a method for recording information on a magneto-optical disk, and more particularly to a method for recording information on a magneto-optical disk, which enables recording at a high information transfer rate using a low recording laser light power.

[Conventional technology]

2. Description of the Related Art In recent years, with the development of optical technology, an optical disc is known in which information is recorded on a substrate surface by using a light beam such as a laser diode, and the recorded information is detected by the light beam to read the information. Such optical discs are broadly classified into non-rewritable read-only discs by function, write-once discs in which information can be written only once, and rewritable erasable discs. In particular, rewritable optical discs have recently attracted attention. ing.

Under such circumstances, a magneto-optical disk is a memory that uses a magnetic material as a recording medium and uses light, particularly laser light, as a recording, reproducing, and erasing means, and is expected as a rewritable large-capacity file memory. There is. In order to process a large amount of data at high speed, it is necessary to increase the rotational speed of the disk to increase the information transfer speed. However, when the disk rotation speed is increased, the irradiation time of the medium with the laser light is shortened, and therefore, when recording or erasing the same pit length, it is necessary to use a laser power larger than that in the case of low speed rotation. Is. By the way, in order to perform recording and erasing with low laser power, in the case of a conventional magneto-optical disk, an optical interference layer is provided on the magneto-optical disk medium so that the recording layer can effectively absorb light, or the recording layer However, from the viewpoint of the signal quality and durability of the magneto-optical disk, it is very difficult to achieve low power only by the disk configuration.

[Problems to be solved by the invention]

Therefore, the present invention solves the above-mentioned problems of the prior art, that is, a problem that a very large laser power is required to process a large amount of data at a high speed in a magneto-optical disk, and a low power recording laser is obtained. An object of the present invention is to provide a method of recording information on a magneto-optical disk which can record information at a high information transfer rate using light.

[Means for solving problems]

According to the present invention, when rewriting the recorded information on the magneto-optical disk, the bias laser light irradiated in DC and the recording laser light turned on / off by the recording signal are used, and the bias laser light is the recording laser light. The irradiation area and the surrounding bit area are irradiated to heat the surrounding bit area to the vicinity of the compensation temperature, the recording laser light heats the magneto-optical medium to the vicinity of the Curie point, and the recording laser light power ( P _W ), bias laser light power (P _B ), and reproduction laser light power (P _R ) use three types of laser light levels having a relationship of P _W > P _B > P _R. A method of recording information in the is provided.

[Action]

Hereinafter, details of the present invention will be described below with reference to the accompanying drawings.

In the magneto-optical disk, a recording method for reducing the recording power has not been proposed so far. Coercive force (H _C ) of TbFeCo, which is a typical material for magneto-optical disk media
The temperature dependence of is as shown in FIG. Information is recorded on the magneto-optical disk by referring to the medium surface with a laser beam to heat the medium to near the Curie point (T _C ) in FIG. 6 to lower the coercive force (H _C ) of the medium and This is done by changing the direction of magnetization of the medium by a magnetic field generated by a magnet provided. That is, "1" and "0" are recorded by reversing the method of applying the magnetic field in this way.

Information is recorded on the magneto-optical disk as described above. However, when recording information on the magneto-optical disk, the influence of the area other than the pits on the information recording area and the pit forming area is affected. Explain whether to receive.

FIG. 1 shows the temperature dependence of the saturation magnetization of TbFeCo, where T _R is the read temperature (room temperature), T _comp is the compensation temperature, and T _C is the Curie point. FIG. 2 shows an image diagram of the magneto-optical disk. When a pit having a downward magnetization is formed in an area having an upward magnetization at room temperature, the area A in FIG. 2 is heated by the laser to a temperature near T _c and becomes downward due to an external magnetic field. The magnetization around the pits, that is, around the pits, is upward because the magnetization is upward, and when the downward magnetization is formed in the region A, the magnetization direction around the pits is magnetically energetically disturbed. Therefore, the area A is overcome by overcoming the influence of the magnetization around the pit.
To invert the magnetization is sufficiently lowering the H _C sufficiently heat the area A, or it is necessary or to increase the external magnetic field.

As shown in FIG. 3, the bias light level heats the magneto-optical medium to a temperature close to the compensation temperature T _comp , and in principle causes the magnetization of the medium to become zero as shown in FIG. The recording light level heats the magneto-optical medium to the vicinity of the Curie point T _C.
FIG. 3 is a block diagram showing an example of the optical level of the information recording method according to the present invention. The recording light level is turned on / off by a recording signal to form an information pit on the medium.
The bias light level is higher than the reproduction light level, and DC irradiation is performed. Therefore, in the present invention, the recording laser light power (P _W ), the bias laser light power (P _B ), and the reproduction laser light power (P _R ) must be in the relationship of P _W > P _B > P _R. .

FIG. 4 shows a schematic diagram of the power distribution and magnetization of light on the medium surface. In FIG. 4, a region A is a region heated to the vicinity of the Curie point T _C by the recording light, and a region B is a region heated to the vicinity of the compensation temperature T _comp by the bias light.

〔Example〕

Examples of the present invention will be described below, but it goes without saying that the technical scope of the present invention is not limited to these examples.

Glass (1.2 mm) / UV curable acrylic ester resin (specifically SA1002 made by Mitsubishi Yuka) (30 μ) / ZnS (900
Å) / TbFeCo (1000 Å) / ZnS (900 Å) configuration disk was rotated at 900 rpm, 1MHz signal was written. We investigated how the recording power changes by fixing the external magnetic field at 300 Oe and changing the bias light level. Here, the "recording power" means the power at which the second harmonic becomes minimum when a signal is written.

The obtained results are as shown in FIG. As shown in FIG. 5, according to the present invention, the bias light power is 1.
By recording the information from 1mW to 1.7mW,
It was possible to reduce the recording laser light power from 3.5 mW to 2.6 mW. This indicates that according to the present invention, information can be recorded under high speed rotation even with low power laser light.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reduce the recording laser light power by eliminating the influence of the magnetization around the pits that hinders the magnetization reversal at the time of recording information on the magneto-optical disk. Since the disk can be rotated at a higher speed, it is possible to obtain a practically excellent effect that the transfer rate of information can be increased.

[Brief description of drawings]

FIG. 1 is a graph showing the temperature dependence of the saturation magnetization of a rare earth-transition metal alloy (TbFeCo) (in FIG. 1, T _R is the read temperature, T _comp is the compensation temperature, and T _C is the Curie point. ). FIG. 2 shows an image diagram of a magneto-optical disk. FIG. 3 is a block diagram showing an example of the optical level of the information recording method of the present invention. FIG. 4 is a drawing schematically showing the relationship between the power distribution of light on the medium surface and the magnetization state. Area A shows the area heated to the vicinity of the Curie point T _C by the recording light. B indicates a region heated to the vicinity of the compensation temperature T _comp by the bias light. FIG. 5 is a graph showing the relationship between bias light level and recording power in the embodiment of the present invention. FIG. 6 shows a typical material as a magneto-optical disk medium.
It is a diagram showing the temperature dependency of the coercive force (H _C) of TbFeCo.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasunobu Hashimoto 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Masahiro Miyazaki 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited ( 56) References JP-A-61-220154 (JP, A)

Claims (1)

[Claims] 1. When rewriting recorded information on a magneto-optical disk, a bias laser light irradiated in a DC manner and a recording laser light turned on / off by a recording signal are used, and the bias laser light is the same as the recording laser light. The irradiation area and the bit area around it are irradiated to heat the surrounding bit area to near the compensation temperature, the recording laser light heats the magneto-optical medium to near the Curie point, and the recording laser light power ( P _W ), bias laser light power (P _B ), and reproduction laser light power (P _R ) use three types of laser light levels having a relationship of P _W > P _B > P _R. To record information on the.