JPH0836802A - Initialization device for overwritable magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] [Object] To provide an initialization device for performing initialization of a magneto-optical recording medium capable of optical modulation overwriting in a short processing time without using large-scale equipment. A means for rotating a magneto-optical recording medium, a light beam irradiation means for raising the temperature of a recording layer of the magneto-optical recording medium, and a magnetic field generation means H1 at a position different from the light beam irradiation position of the magneto-optical recording medium. The initialization device is provided with.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for initializing an overwritable magneto-optical recording medium utilizing exchange coupling force.

[0002]

2. Description of the Related Art Generally, a magneto-optical recording medium is manufactured by a sputtering method so that the magnetization direction of its recording layer is perpendicular to the substrate. However, the direction is totally random. Even if the magneto-optical recording medium is set and recorded in the recording / reproducing apparatus in this state, the outer side of the recording track, particularly the part of the guide groove part in the random magnetization direction, remains as it is. Then, when the mark recorded in this state is reproduced, a part of the outer peripheral portion of the reproduction beam in a random magnetization direction is also taken in as a reproduction signal, so that there is a problem that the quality of the reproduction signal is deteriorated.

In order to avoid such a problem, after a magnetic layer such as a recording layer is formed, a magnetic field in a constant direction higher than the coercive force of the magnetic layer is applied to the medium to magnetize the entire surface of the magneto-optical recording medium. The initialization process was performed to align the same direction.

[0004]

However, in the case of an optical modulation overwrite magneto-optical recording medium, in order to prevent the recorded signal from being affected by the magnetic field for initializing the recording layer, the memory layer is protected. The magnetic force is set larger than the coercive force of a normal non-overwrite medium,
The switching field required to change the magnetization direction of the memory layer is often larger due to the exchange coupling force acting between the magnetic layers, and thus the magnetic field required to initialize the exchange coupling overwrite magneto-optical recording medium. Had a problem that it became a very large-scale facility with more than 20 KOe.

Therefore, a method has been proposed in which the magneto-optical recording medium is irradiated with a laser beam while the medium is being rotated to apply a magnetic field while the medium temperature is raised to about the Curie temperature for initialization. In this method, the applied magnetic field is smaller than that in the above method. However, since the Curie temperature of the magnetic layer of the overwritable medium is higher than that of the non-overwritable medium, in order to raise the temperature of the magnetic layer to about the Curie temperature, the rotation of the medium is a practical device. Since the number must be set low, the processing time per medium becomes long, and there is a problem that productivity is reduced.

[0006]

In order to solve such a problem, as a result of earnest research by the present inventor, first, after initializing a layer of a small initializing magnetic field, the temperature of the medium is raised to perform magnetic transfer. The inventors have found that a layer having a large initializing magnetic field can be initialized by the above method, and have completed the present invention. Therefore, the first aspect of the present invention is, in an initialization apparatus for an overwritable magneto-optical recording medium having at least two layers of a memory layer and a recording layer, means for rotating the magneto-optical recording medium, Overwritable magneto-optical recording, characterized in that a light beam irradiation means for raising the temperature of the recording layer and a magnetic field generation means H1 are provided at a position different from the light beam irradiation position of the magneto-optical recording medium. And a second magnetic field generating means H1 for generating a magnetic field larger than a magnetic field necessary for reversing the magnetization of the tracking guide groove portion of the recording layer. 1. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is an overwritable magneto-optical recording medium having a memory layer, a recording layer, a switching layer and an initialization layer. An initialization device according to claim 1 or 2 is provided, and fourthly, a second magnetic field generating means H2 is provided at a light beam irradiation position. Two
And the initialization device described in 3 above.

[0007]

According to the initialization device of the present invention, first, only the recording layer having a small reversal magnetic field is initialized by the external magnetic field.
This also includes the guide groove portion of the recording layer. As a result, the recording layer is completely initialized over the entire surface of the medium.
Further, the initialization of the memory layer is carried out by irradiating a laser beam to a temperature (low temperature process temperature) at which magnetic transfer from the recording layer to the memory layer occurs. This allows the memory layer to be initialized without increasing the medium temperature.

The device of the present invention is also effective for a medium in which a reproducing layer showing a large Kerr rotation angle is added on the memory layer in order to improve the quality of the reproduced signal. Also,
For a type of medium that does not require an initialization magnet and instead has an initialization layer for initializing itself, if the magnitude of the magnetic field generated from the magnetic field generating means is equal to or greater than the reversal magnetic field of the initialization layer. Good. In this case, the magnetic field generating means at the laser beam irradiation position functions to assist the initialization of the memory layer.

[0009]

Embodiment 1 FIG. 2 shows the structure of an overwritable magneto-optical recording medium according to the present invention. In FIG. 2, 1 is a PC substrate having a tracking guide groove, 2 is a protective layer made of silicon nitride, 3 is a reproducing layer made of GdFeCo, 4 is a memory layer made of TbFeCo, and 5 is GdFeCo having a composition different from that of the reproducing layer.
6 is an intermediate layer for adjusting the exchange coupling force, and 6 is a recording layer made of DyFeCo. All of these magnetic layers were formed by the sputtering method. Further, 7 is an overcoat layer made of an ultraviolet curable resin. The thickness of each layer is protective film 2
80 nm, playback layer 3 25 nm, memory layer 4 25 nm,
The intermediate layer 5 has a thickness of 15 nm, and the recording layer 6 has a thickness of 50 nm.

FIG. 1 shows a conceptual diagram of the initialization device of the present invention. This apparatus generates a magnetic field at a first magnetic field generator 31 for initializing a recording layer or an initializing layer, a laser beam generator 32 for raising the medium to a low temperature process temperature, and a laser beam irradiation position of the medium. It is composed of the second magnetic field generator 33, and the medium is rotatable. An overwritable medium was set in the initialization device shown in FIG. 1, the medium was rotated at 5 m / sec, and a 2 W laser beam narrowed down to a beam diameter of 50 μm was irradiated with a lens. here,
The magnetic field generated by the magnetic field generator was adjusted to be 5 kOe in the magnetic layer of the medium. A magnetic field of 300 Oe was applied to the beam irradiation position in the initialization direction of the memory layer. The beam was moved from the inner circumference to the outer circumference or vice versa to initialize the entire surface of the medium.

Next, the medium initialized in the above process was set in a recording / reproducing apparatus, and recording and reproducing were performed on a land while tracking was performed. The recording condition is linear velocity 1
A recording laser power of 1.3 m / sec, a high level of 8 mW, and a low level of 4 mW was used to record a signal with a 3 MHz duty ratio of 50% and then overwrite a signal with a 4 MHz duty ratio of 50%. After that, while reproducing with a laser power of 1 mW, C
When the / N value was measured, 57.3 dB was obtained. Further, when tracking the guide groove and observing the signal in this portion, there was no noise, and it was confirmed that the guide groove portion was completely initialized.

[0012]

[Comparative Example 1] The same measurement was carried out under the same conditions and conditions as in Example 1 except that the first magnetic field generating means 31 was not provided.
The C / N value was 45.6 dB, which was significantly lower than that in Example 1. Moreover, a noise signal due to random magnetization was confirmed over the entire surface of the guide groove.

[0013]

[Comparative Example 2] A C / N value was obtained when the same measurement was performed under the same conditions and conditions as in Example 1 except that the magnitude of the magnetic field generated by the first magnetic field generating section 31 was 3 kOe on the medium surface. Is 51.7 dB
Was much higher than that of Example 2, but much lower than that of Example 1. Moreover, a noise signal due to locally random magnetization remained in the guide groove.

[0014]

Second Embodiment FIG. 3 shows the construction of another overwritable magneto-optical recording medium according to the present invention. In Figure 3,
8 is a PC substrate having a guide groove for tracking, 9 is a protective layer made of silicon nitride, 10 is a reproducing layer made of GdFeCo,
11 is a memory layer made of TbFeCo, 12 is an intermediate layer made of GdFeCo for adjusting exchange coupling force, 13 is a recording layer made of DyFeCo, 14 is a switching layer made of TbFe, and 15 is TbCo.
The initializing layer was formed by sputtering method. Reference numeral 16 is an overcoat layer made of an ultraviolet curable resin. The thickness of each layer is 80 nm for the protective film 9, 30 nm for the memory layer 11, 15 nm for the intermediate layer 12, and 50 n for the recording layer 13.
m, switching layer 14 is 15 nm and initialization layer 15 is 50 nm
Is.

By passing the thus obtained overwritable magneto-optical recording medium not requiring an initializing magnetic field through a magnetic field generating means for generating a magnetic field of 11 kOe, the magnetization of the initializing layer, the switching layer and the recording layer is magnetized. The directions were aligned in a fixed direction and further initialized by the same initialization device as in Example 1. Next, this medium was set in a recording / reproducing apparatus, and recorded and reproduced on a land while tracking was performed. As the recording conditions, a recording laser power with a linear velocity of 11.3 m / sec, a high level of 9 mW and a low level of 4.5 mW was used to record a signal with a 3 MHz duty ratio of 50%, and then a signal with a 4 MHz duty ratio of 50% was overwritten. After that, the C / N value was measured while reproducing with a laser power of 1 mW.
dB was obtained. In addition, tracking is performed on the guide groove,
Observation of the signal in this portion confirmed that the guide groove was completely initialized since there was no noise at all.

[0016]

As described above, according to the present invention, it is possible to perform initialization with a small magnetic field generating means, and it is also possible to perform initialization even when the medium temperature is low. Since it is possible to set a high value, the initialization time can be shortened and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an initialization device of the present invention.

FIG. 2 is a configuration diagram of an overwritable magneto-optical recording medium according to the present invention.

FIG. 3 is a block diagram of another overwritable magneto-optical recording medium according to the present invention.

[Explanation of symbols]

 1 ... Substrate 2 ... Protective Layer 3 ... Reproducing Layer 4 ... Memory Layer 5 ... Intermediate Layer 6 ... Recording Layer 7 ... Resin Overcoat Layer 8 ... Substrate 9. ..Protective layer 10 ... Reproducing layer 11 ... Memory layer 12 ... Intermediate layer 13 ... Recording layer 14 ... Switching layer 15 ... Initialization layer 16 ... Resin overcoat layer 31・ ・ ・ First magnetic field generator 32 ・ ・ ・ Laser beam generator 33 ・ ・ ・ Second magnetic field generator

Claims (4)

[Claims] 1. In an initialization apparatus for an overwritable magneto-optical recording medium having at least two layers of a memory layer and a recording layer, a means for rotating the magneto-optical recording medium, a temperature of the recording layer of the magneto-optical recording medium. And a magnetic field generating means H1 provided at a position different from the light beam irradiation position of the magneto-optical recording medium, and initialization of an overwritable magneto-optical recording medium. apparatus. 2. The initialization device according to claim 1, wherein the magnetic field generating means H1 generates a magnetic field larger than the magnetic field required to reverse the magnetization of the tracking guide groove portion of the recording layer. 3. The initialization according to claim 1, wherein the magneto-optical recording medium is an overwritable magneto-optical recording medium having a memory layer, a recording layer, a switching layer and an initialization layer. apparatus. 4. The initialization device according to claim 1, 2 or 3, wherein a second magnetic field generating means H2 is provided at a light beam irradiation position.