JP2636694B2 - Recording / reproducing method and recording / reproducing apparatus for magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing method for a magneto-optical recording medium for recording / reproducing information by laser light utilizing a magneto-optical effect, and a recording / reproducing apparatus therefor.

[0002]

2. Description of the Related Art An optical disk or the like in which information is recorded / reproduced by laser light has an excellent feature as a large-capacity storage device due to its high recording density. In general, as a rewritable optical recording medium such as an optical disk, a magneto-optical type using a magnetic Kerr effect is used.

FIG. 2 shows a schematic sectional view of a typical magneto-optical recording medium as an example of the prior art (for example, Japanese Journal of Applied Physics, Vol. 28, No. 6).
Pp. 7-70, 1989 (Japanese Jou
rnal of Applied Physics V
ol. 28, p. 67-70, 1989).

The magneto-optical recording medium shown in FIG.
01 is provided on the first dielectric layer 102, and TbF
A magneto-optical layer 103 of a ferrimagnetic material of an amorphous alloy of an iron group transition metal such as eCo is provided, a second dielectric layer 104 is provided thereon, and a reflective layer 105 is provided thereon in that order.

The thickness of the magneto-optical layer 103 is 150 to 3
A range of 00 Angstroms is used. This is because if the thickness is more than that, the laser beam hardly passes through the magneto-optical layer 103, so that the signal amplitude cannot be increased by the multiple interference structure using the reflective layer 105.

In some cases, recording and reproduction of information are performed by injecting a laser beam through the transparent substrate 101 while keeping the configuration of the magneto-optical recording medium as shown in FIG.
In some cases, a protective layer of a UV-curable resin is provided on the recording medium to record and reproduce information. Further, by applying a hot melt agent on the protective layer of the UV-curable resin, there are cases where two magneto-optical recording media are adhered such that the transparent substrate is on the outside to record and reproduce information. Furthermore, as a magneto-optical recording medium with further improved reliability, a transparent back coat layer such as SiO2 may be provided on the transparent substrate 101 opposite to the first dielectric layer 102.

As the transparent substrate 101, a polycarbonate resin plate, a glass plate with a photopolymer, or an acrylic resin plate with a photopolymer is used. In general, guide grooves and guide pits are formed on the transparent substrate 101 for tracking servo. The track pitch is approximately 0.8 to 1.6 μm.

First dielectric layer 102 and second dielectric layer 1
As a material of 04, silicon nitride, tantalum oxide, or hydrogenated silicon carbide is used.

The magneto-optical layer 103 is made of TbFeCo
, TbFeCoTi, TbFeCoCr, TbF
eCoTa, TbFeCoNb, TbFeCoNi
, TbFeCoNiCr, TbFeCoPt, G
dTbFeCo, GdTbFeCoTi, GdTb
FeCoCr, GdTbFeCoTa, GdTbF
eCoNb, GdTbFeCoNi, GdTbFe
CoNiCr, GdTbFeCoPt, DyTbF
eCo, DyTbFeCoTi, DyTbFeCo
Cr, DyTbFeCoTa, DyTbFeCoN
b, DyTbFeCoNi, DyTbFeCoNi
Cr, DyTbFeCoPt, NdTbFeCo
, NdTbFeCoTi, NdTbFeCoCr
, NdTbFeCoTa, NdTbFeCoNb
, NdTbFeCoNi, NdTbFeCoNiC
r, NdTbFeCoPt, GdNdTbFeCo
GdNdTbFeCoTi, GdNdTbFeC
oCr, GdNdTbFeCoTa, GdNdTb
FeCoNb, GdNdTbFeCoNi, GdN
dTbFeCoNiCr, GdNdTbFeCoPt
Is used.

As the reflection layer 105, Al or AlTi
Al alloys such as AlCr, AlTa, and AlNi, Au alloys, Cu alloys, and Pt alloys are used.

To record and reproduce information on such a magneto-optical recording medium, a recording and reproducing apparatus as shown in FIG. 3 is used.
FIG. 3 illustrates a case where the magneto-optical recording medium is a magneto-optical disk. The magneto-optical recording medium 110 includes a motor 111
It is attached to and rotated. An optical head 112 is provided at a fixed position with respect to the magneto-optical recording medium 110 as an irradiation means of a laser beam for recording and reproducing information.
A recording electromagnet 113 is provided on the opposite side of the magneto-optical recording medium 110 from the optical head 112.

The laser light for recording and reproduction is applied to the optical head 1.
The light is radiated from 12 to the magneto-optical recording medium 110, enters through the transparent substrate 101, and is focused by the focusing servo so as to be approximately φ1.4 μm near the magneto-optical layer 103. The wavelength λ is 830 as a laser light source.
A semiconductor laser of about 0 Å is used, and a numerical aperture NA of the objective lens is about 0.55.

In recording information, the temperature of the magneto-optical layer 103 is raised near the Curie temperature of the film in accordance with the information, and a recording bias magnetic field is applied to the electromagnet 1 in a region including this portion.
By setting the temperature from 13, the magnetization of a portion heated to a temperature near the Curie temperature is oriented in a direction opposite to that of the other portions.

In reproducing information, a focused laser beam, which has been made substantially linearly polarized, is emitted from the optical head 112 toward the magneto-optical recording medium 110, and is irradiated while being relatively moved to the above-mentioned inverted magnetic domain of the magneto-optical layer 103. By optically detecting the reflected light therefrom via an analyzer. This is because the magneto-optical film has the effect of rotating the plane of polarization of the reflected light by the magnetic Kerr effect, and the rotation angle θk of the plane of polarization of the reflected light differs depending on the direction of the perpendicular magnetization of the magneto-optical film. By passing the light through an analyzer before entering the detector, information corresponding to the direction of magnetization can be read out as a change in the amount of light. When reproducing this information, the power of the electromagnet 113 is turned off, and no external magnetic field is applied. This is to prevent the temperature of the magneto-optical recording medium from rising due to the heat generated by the electromagnet.

A recording / reproducing laser beam enters through a transparent substrate 101, and is focused and adjusted to approximately φ1.0 to φ1.4 μm near the magneto-optical layer 103.
Light is collected by the servo.

The wavelength of the laser light source is 6300 to 830.
A semiconductor laser of about 0 Å is used.

However, with such a recording / reproducing method or recording / reproducing apparatus, a highly reliable information data cannot be obtained.

[0018]

The inventors of the present invention have conducted intensive studies on the above-mentioned phenomenon of low reliability, and as a result, it has been found that the cause is that the noise of the magneto-optical recording medium is high.

An object of the present invention is to provide a recording / reproducing method and a recording / reproducing apparatus for reducing noise of a magneto-optical recording medium.

[0020]

According to a first aspect of the present invention, there is provided a method for recording / reproducing a magneto-optical recording medium, comprising: a first dielectric layer on a transparent substrate; a magneto-optical layer having a thickness of 150 to 300 angstroms; Using a magneto-optical recording medium in which a second dielectric layer and a reflective layer are laminated at least in this order, a focused laser beam is irradiated while moving relatively to the magneto-optical layer through the transparent substrate to form a recording mark. At the time of reproduction, a configuration is adopted in which a reproduction external magnetic field is applied together with the irradiation of the reproduction laser beam.

According to a second aspect of the present invention, there is provided a recording / reproducing apparatus for a magneto-optical recording medium, comprising: a laser beam irradiating means for recording information; and a laser beam irradiating means for reproducing information. Are configured to be connected.

[0022]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of a recording / reproducing apparatus for explaining a recording / reproducing method for a magneto-optical recording medium according to one embodiment of the present invention.

The magneto-optical recording medium 10 is attached to a motor 11 and rotated. An optical head 12 is provided at a specific position on the magneto-optical recording medium 10 as a means for irradiating a laser beam for recording information, and the other position is a means for irradiating a laser beam for reproducing information. An optical head 13 is provided. The recording optical head 12 is provided with a recording electromagnet 14 on the opposite side of the magneto-optical recording medium 10, and the reproducing optical head 13 is provided with a reproducing permanent magnet on the opposite side of the magneto-optical recording medium 10. 15 are provided.

In the magneto-optical recording medium 10, a first dielectric layer is provided on a transparent substrate, and a magneto-optical layer of a ferrimagnetic material of an amorphous alloy of an iron group transition metal such as TbFeCo is provided thereon. A second dielectric layer is provided thereon, and at least a reflective layer is sequentially provided thereon. The thickness of the magneto-optical layer is 15
A range of 0 to 300 angstroms is used. This is because if the thickness is larger than that, the laser beam hardly passes through the magneto-optical layer, and the signal amplitude cannot be increased by the multiple interference structure using the reflective layer.

A recording laser beam and a reproduction laser beam are incident through a transparent substrate, and are approximately φ near the magneto-optical layer.
Focusing is performed by a focusing servo so as to be 1.0 to 1.4 μm.

The laser light source has a wavelength of 6300 to 830.
A semiconductor laser or gas laser of about 0 Å is used.

To record information, a high-power laser beam from the optical head 12 is focused on the magneto-optical layer through the transparent substrate and irradiated, so that the magneto-optical layer absorbs the energy of the laser beam and converts it into thermal energy. Then, the heat is used to raise the temperature of the magneto-optical layer to near the Curie temperature. In this state, the recording bias magnetic field is applied to the region including this portion by the electromagnet 14.
Is turned on and applied. When the temperature after the irradiation of the high-power laser beam is lowered, information in which a reversal magnetic domain is formed in the magneto-optical layer as a recording mark is reproduced by using the low-power laser beam from the optical head 13 through the transparent substrate. Irradiation is performed while relatively moving the recording layer to convert the reversed magnetic domains (recording marks) recorded on the magneto-optical layer into electric signals by changing the light amount change due to the optical rotation or circular dichroic magneto-optical effect. At this time, it is important that an external magnetic field for reproduction is applied from the permanent magnet 15 to the vicinity of the recording mark to be reproduced.

The present inventors have used a magneto-optical recording medium in which a first dielectric layer, a magneto-optical layer, a second dielectric layer, and a reflective layer are laminated at least in this order on a transparent substrate. When information was recorded and reproduced by the conventional recording and reproducing method, it was found that the recording and reproducing characteristics such as large jitter were sometimes defective. When this phenomenon was examined in more detail, it was found that when the thickness of the magneto-optical layer was 150 to 300 angstroms, the jitter was large, and this was due to large unrecorded noise.

The present inventors have found that this unrecorded noise can be reduced by applying an external magnetic field during reproduction, and reached the present invention.

The reason why the permanent magnet is used as the external magnetic field applying means during reproduction in the recording / reproducing apparatus of the present invention is that when the electromagnet is used, a problem occurs in the recording / reproducing characteristics. That is, they found that the temperature of the magneto-optical layer was inappropriately increased due to heat dissipated from the electromagnet, and reached the present invention.

Hereinafter, specific examples will be described.

The diameter of the guide groove is 130 mm,
A disc substrate made of a polycarbonate resin having a thickness of 1.20 mm is placed in a sputtering apparatus and evacuated to 5 × 10 −7 Torr or less. Then, the surface of the polycarbonate resin is reverse sputtered with argon gas for about 10 angstroms, and then silicon is sputtered. A 1100 Å thick first dielectric layer of silicon nitride was provided by sputtering the target with a mixed gas of argon and nitrogen. Next, the first dielectric layer is reversely sputtered with argon gas for about 7 angstroms, and then a TbFeCoTi target is sputtered with argon gas to form a 200
An amorphous magneto-optical layer of TbFeCoTi having a thickness of Å was formed. Next, a silicon target was sputtered with a mixed gas of argon and nitrogen to provide a second dielectric layer of silicon nitride having a thickness of 300 angstroms. An AlTi alloy target is sputtered with argon gas thereon to form a 300 Å thick A
A reflective layer of 1Ti was provided. Thereafter, the film was taken out of the sputtering apparatus into the atmosphere, a UV curable resin was spin-coated on the AlTi reflective layer, and UV irradiation was performed to form an 8 μm-thick overcoat layer of the UV curable resin. Lastly, a magneto-optical recording medium was manufactured by laminating two disks having such a configuration with a hot melt agent so that the substrate was on the outside.

This magneto-optical recording medium was rotated at 3000 rpm, and a semiconductor laser beam having a wavelength of 8300 angstroms was irradiated onto the magneto-optical layer through the substrate while being focused to approximately φ1.4 μm. It was confirmed that the noise was reduced by about 5 dB when the reproduction was performed while applying an external magnetic field of about 300 Oersted at a radius of 30 mm as compared with the case where no external magnetic field was applied.

[0035]

According to the recording / reproducing method and the recording / reproducing apparatus for a magneto-optical recording medium of the present invention, an external magnetic field is applied during the reproduction, whereby the first dielectric layer and the first dielectric layer having a thickness of 150 mm are formed on the transparent substrate.
In the case of using a magneto-optical recording medium in which a magneto-optical layer, a second dielectric layer and a reflective layer of up to 300 angstroms are laminated in this order, the signal amplitude can be increased by the multiple interference structure, but on the other hand magneto-optical recording Since an increase in noise of the medium can be suppressed, there is an effect that information can be recorded and reproduced with a good bit error rate.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic structure of a recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a basic structure of a magneto-optical recording medium.

FIG. 3 is a diagram showing a configuration of a conventional recording / reproducing apparatus for a magneto-optical recording medium.

[Explanation of symbols]

 Reference Signs List 10 magneto-optical recording medium 11 motor 12 recording optical head 13 reproducing optical head 14 electromagnet 15 permanent magnet 101 transparent substrate 102 first dielectric layer 103 magneto-optical layer 104 second dielectric layer 105 reflective layer 110 magneto-optical recording medium 111 Motor 112 Optical head 113 Electromagnet

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-143042 (JP, A) JP-A-63-160030 (JP, A) Japanese Utility Model Showa 61-121523 (JP, U)

Claims (2)

(57) [Claims] 1. A magneto-optical recording device comprising: a first dielectric layer, a magneto-optical layer having a thickness of 150 to 300 angstroms, a second dielectric layer, and a reflective layer at least laminated in this order on a transparent substrate. A recording / reproducing method for a medium, in which a focused laser beam is irradiated while being moved relatively to the magneto-optical layer through the transparent substrate to reproduce a recorded mark, the irradiation is performed together with the laser beam for reproduction. A recording / reproducing method for a magneto-optical recording medium, wherein an external magnetic field for reproduction is applied to a position by a permanent magnet in a direction opposite to that in recording. 2. A recording / reproducing apparatus using the recording / reproducing method according to claim 1, wherein the information recording laser light irradiating means for irradiating the information recording laser light from a transparent substrate side of the magneto-optical medium, and the magneto-optical device. An information reproducing laser beam irradiating unit for irradiating the information reproducing laser beam from the transparent substrate side of the recording medium, wherein the reproducing laser beam irradiating unit includes the information reproducing laser beam of the magneto-optical recording medium. Record at the irradiation position
A recording / reproducing apparatus for a magneto-optical recording medium, wherein a permanent magnet for applying an external magnetic field for reproduction in a direction opposite to the time is connected.