JP2698852B2 - Magneto-optical recording method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magneto-optical recording method, and more particularly to a magneto-optical recording method for performing recording on a magneto-optical recording medium by a magnetic field modulation method.

[Prior Art] Magneto-optical recording generally uses an optical modulation method, but this method has a drawback that overwriting cannot be performed.

According to the magnetic field modulation method, overwriting is easy, but if a sandwich structure or a thick protective film is attached to improve reliability, the magnetic head must be separated from the medium surface, and as a result, it is generated by the magnetic head This increases the magnetic flux to be applied and increases the power consumption of the magnetic head, which is not practical.

The above problem can be solved by bringing the magnetic head close by means such as air levitation, but the sandwich structure or the thick protective film cannot be used, and the recording medium (magnetic recording layer, guide track, dielectric layer, reflection layer, etc.) In addition, since the magnetic head is almost in contact with the magnetic head at the time of recording, there is a danger that the already recorded information and the recording medium itself may be destroyed, and the reliability is lacking. In particular, in the case of a Tb-Fe-based amorphous film, there is a property that magnetization is reversed by strain stress, and there is a risk that recorded information is destroyed even by a slight contact.

〔Purpose〕

The present invention relates to a magneto-optical recording method in which a magnetic head is brought close to a recording medium by a magnetic field modulation method on a magneto-optical recording medium whose recording surface is bare or almost bare, Damage to already recorded information due to collision with the medium surface or contact during other handling, and destruction of the recording medium itself such as the magnetic recording layer, guide groove (guide track), dielectric layer and reflective layer. An object of the present invention is to improve the reliability of magneto-optical recording by preventing such a phenomenon.

〔Constitution〕

The present inventors have conducted intensive studies to achieve the above object, and as a result, in a magneto-optical recording method for performing recording on a magneto-optical recording medium having a guide groove by a magnetic field modulation method using a magnetic field applying means, The guide groove is λ / 4n (λ =
It has a structure that is deeper than the wavelength of the laser beam used for reading or recording (n = refractive index of the portion forming the guide groove). When recording, the magnetic field applying means is brought close to the groove of the guide groove. It has been found that the above-mentioned object can be achieved by providing a magneto-optical recording method characterized by performing recording.

In an optical disc with a guide groove (guide track), the relationship between the groove depth and the track error signal is almost as shown in FIG. 1 (actually, as the groove becomes deeper, the track error slightly increases as shown in FIG. Usually the signal is reduced). The track error signal is maximum at λ / 8n, but it is customary to design it slightly off λ / 8n in relation to the RF signal strength, but the depth varies depending on the recording method etc. It is. However, in any case, the depth of the groove was conventionally designed to be shallower than λ / 4n. The reason for this is that there was no advantage in making the track depth deeper than λ / 4n in any case of the track error signal, the RF signal, the problem of noise, and the ease of processing.

Conventionally, the recording layer of an optical disk was completely protected, and no external contact or damage was considered.However, in a magneto-optical disk in which a magnetic head is brought close to and recording is performed by a magnetic field modulation method, a thick protective layer is not used. They are not attached and the danger of contact and damage is inevitable. In particular, in the case of a Tb-Fe-based amorphous film, there is a characteristic that magnetization is reversed by strain,
There is a danger that the recorded bits may be inverted even by a slight contact that does not damage the recording layer.

Such danger is caused not only by recording on the land 4 (recording on non-groove portions) as shown in FIG. 2 but also by narrowing the width of the groove 3 as shown in FIG. 3 and land 4
The risk is great when recording both.

As shown in FIG. 4, even when the width of the groove 3 is widened and the bit is completely recorded in the groove, if the depth of the groove 3 is set to λ / 4n or less, the groove width is 0.8 to 1 μm. To the extent, the groove depth is 0.13 μm or less (when λ = 780 nm and n = 1.5), resulting in a very shallow groove. Therefore, there is a great risk of contact from outside even at the bottom of the groove.

Generally preferred groove width is about 0.4 to 1.2 μm,
Particularly, when recording is performed only in the groove, the thickness is about 0.8 to 1.2 μm.

In the case of an amorphous magneto-optical film or the like, the domain wall in the film moves. As shown in FIG. 5, when the groove and the land are continuous films, even if an object does not contact the groove. ,
The magnetic domain reversed at the land portion due to contact or the like spreads to the groove, and the information bit recorded in the groove may be destroyed.

In the present invention, as shown in FIG.
By making the groove deeper, the danger of damage due to external contact of the groove 3 with the recording layer 2 is reduced. Also, by making the groove deeper,
The magnetic recording film between the groove 3 and the land 4 becomes discontinuous, and the danger of damage to the recording of the groove 3 due to domain wall movement when the land 4 reverses magnetization is reduced.

As the type of the structure of the magneto-optical recording medium of the present invention,
(A) a magnetic recording layer / substrate, (b) a magnetic recording layer / dielectric layer / substrate, (c) one having a protective layer in addition to the structure of (a) or (b), (d) (A) or (b) having an additional reflective layer,
(E) The structure of the above (a) or (b) has a reflective layer /
There are those having an additional dielectric layer, and those (f) having a protective layer in addition to those having the structure (d) or (e).

The material of the substrate used is glass (Corning
0313, 0317, 7059, etc.), PMMA, polycarbonate, epoxy resin and the like.

As the material of the magnetic recording layer, RE-TM amorphous alloy (Tb-Fe, Ga-Tb-Fe, Tb-Fe-Co, Gd-Tb-Fe-Co, Gd-
Co, Dy-Fe, etc.), β-substituted garnet, Co spinel ferrite, magnetoplumbite ferrite, and the like.

Hereinafter, an example of an embodiment of the present invention will be described with reference to FIG.

Example A PMMA substrate 1 having a thickness of 1.2 mm was 1 μm wide, 2 μm pitch,
A guide groove 3 having a depth of 0.3 μm is formed, a TbFeCo amorphous alloy film 5 is formed thereon as a magnetic recording layer to a thickness of 0.1 μm by RF sputtering, and a 0.2 μm Si ₃ N _{4 is} further formed thereon.
The magneto-optical recording medium was manufactured by forming the film 6 as a protective layer.

Recording was performed on the magneto-optical recording medium manufactured in this manner by a magnetic field modulation method using a magnetic field applying means, and information was recorded in the groove 3. There was little risk of damage to the recorded information or the recording layer itself.

〔effect〕

As described above, when recording is performed by bringing the magnetic head close to the magneto-optical disk in which the recording layer is exposed or nearly exposed, the depth of the guide groove is
When the recording layer is provided deeper than a specific depth, damage to the recording layer or destruction of already recorded information due to contact from the outside can be prevented, and reliability is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the relationship between the depth of a guide groove of an optical disc and a track error signal. 2 to 5 are explanatory views of a conventional optical disk. 6 and 7 are explanatory views of the optical disk of the present invention. 1 ...... substrate, 2 ...... magnetic recording layer 3 ...... guide groove, 4 ...... land portion 5 ...... TbFeCo amorphous alloy film 6 ...... Si ₃ N ₄ film

Claims (1)

(57) [Claims] 1. A magneto-optical recording method for performing recording on a magneto-optical recording medium having a guide groove by a magnetic field modulation method using a magnetic field applying means, wherein the guide groove of the magneto-optical recording medium is λ / 4n.
(Λ = wavelength of laser beam used for reading or recording) (n
A magneto-optical recording method having a structure deeper than (= refractive index of a portion forming a guide groove), and performing recording by bringing a magnetic field applying means close to the groove portion of the guide groove during recording.