JPH01124132A - Recording method - Google Patents

Abstract

PURPOSE:To perform the rewrite of information in a short time by performing overwrite by forming two kinds of magnetic fields whose magnetizing directions are set oppositely to each other in the advancing direction of a recording medium, projecting two kinds of laser beams whose strength are different, and enabling a point less a Curie temperature or a compensation temperature to appear on respective magnetic field as advancing the recording medium. CONSTITUTION:The recording of information is performed by forming the two kinds of magnetic fields whose magnetizing directions are set oppositely to each other in the advancing direction of the recording medium 10, and projecting the two kinds of laser beams 5 whose strength are different on the recording medium 10, and enabling the point less than the Curie temperature or the compensation temperature to appear on respective magnetic field as advancing the recording medium 10. The method is performed by utilizing the fact that a time difference based on the strength of a laser power exists until the recording medium 10 is cooled. In such a way, it is possible to perform the overwrite of new information on old information without erasing the old information, and to shorten a time required for the rewrite of the information remarkably.

Description

[Detailed Description of the Invention] [Summary] Regarding a method of recording information on a magneto-optical disk by overwriting, the present invention aims to provide a method that allows information to be easily and quickly rewritten by overwriting. , two types of magnetic fields with opposite magnetization directions are formed in the traveling direction of the recording medium, and the recording medium is irradiated with two types of laser beams with different intensities, so that the recording medium advances. As time goes on,
Information is recorded so that a point below the Curie temperature or compensation temperature appears in each of the magnetic fields.

C. Industrial Application Field] The present invention relates to a recording method, and more specifically, to a method for recording information on a magneto-optical disk by overwriting.

[Conventional technology]

On conventional magneto-optical disks, information is normally recorded, reproduced, and erased in the following manner: Recording...High output is applied to the recording medium of a magneto-optical disk in which the direction of magnetization is aligned in one direction. is irradiated with a laser beam (for example, φ1 square) to heat it above the Curie temperature or compensation temperature, and an external magnetic field is used to make the magnetization direction of only the laser irradiated part the same as the direction of the external magnetic field.

Note that this information recording is performed by modulating the laser intensity.

Reproduction: A low-power laser beam is irradiated onto the recording medium, and the polarization plane of the reflected light is rotated by the magnetic Kerr effect.
Record code “O”.

Read “1”.

Erasing: A high-power laser beam is irradiated onto the recording medium, and an external magnetic field in the opposite direction to the recording direction is used to return the magnetization direction to the original direction.

To explain this conventional recording method more specifically, it is carried out, for example, by a method as shown in FIG. The magneto-optical disk 10 consists of a substrate 1 and a recording medium layer 2 on the substrate.

The traveling direction of the recording medium is indicated by arrow A. The optical head consists of an optical system 4 and a laser beam 5 that is focused thereby. A magnet 8 for forming an external magnetic field is arranged on the side of the recording medium facing the optical node. The magnet 8 can reverse the direction of external magnetization each time information is recorded or erased.

The recording method shown in FIG. 5 is implemented, for example, using a rewriting pulse as shown in FIG.

Information is erased during the first revolution of the optical disc.

This is possible by irradiating the recording medium with a high power laser beam in the presence of an external magnetic field opposite to the writing described below. Enter the second round and start writing information. This is done by setting the external magnetic field in the opposite direction to the erasing process and then irradiating the laser beam with two different power levels to convert the information into two recording codes "0" and "1".
This can be done by converting and writing.

In the illustrated case, the codes "0" and "1" are alternately combined to form continuous pulses.

As is clear from the above explanation, in this conventional information recording method, the direction of magnetization of the recording medium changes only in the area irradiated with a high-power laser beam, so information recorded at -degrees can be converted into new information. To rewrite, the old information must be erased and then the new information must be written. Therefore, it is necessary to rotate the disk at least twice in order to rewrite the information, and the information writing speed becomes slower accordingly.

[Problem that the invention seeks to solve]

An object of the present invention is to eliminate the drawbacks as clarified in the section of the prior art, in other words, to provide a method for rewriting information on a magneto-optical disk easily and in a short time by overwriting. There is a particular thing.

[Means for solving problems]

As a result of intensive research to achieve the above object, the present inventors have discovered that when a recording medium is heated by irradiating it with a laser beam, the recording medium begins to cool down and falls below its Curie temperature or compensation temperature (i.e., its Curie temperature or compensation temperature). By using the fact that the time (below the temperature) changes in various ways depending on the laser power, the code “0” can be obtained without erasing information each time.
”.

It has been found that it is possible to perform separate recording of "1".

The method of the present invention is a method of recording information on a magneto-optical disk by overwriting, and in which two types of magnetic fields with opposite magnetization directions are formed in the traveling direction of the recording medium. Information is recorded by irradiating the medium with two types of laser beams with different intensities so that as the recording medium advances, a point below its Curie temperature or compensation temperature appears in each of the magnetic fields. It is characterized by

The method of the present invention utilizes the fact that, as described above, there is a difference in the time required for the recording medium to cool down depending on the magnitude of the laser power. Therefore, in carrying out the method of the present invention, the recording medium is preferably irradiated with a laser beam having an intensity capable of heating the medium to a temperature slightly higher than the Curie temperature or compensation temperature of the medium. , a laser that writes the first information at a certain position in the medium traveling direction at or near the laser beam irradiation part, and has an intensity that can heat the recording medium to a higher temperature than when writing the first information. Irradiate the beam,
The second information is written at a position further away in the medium traveling direction than the writing position of the first information. In addition, regarding writing of these first and second information,
This is preferably done in a conventional manner, for example by converting the recording codes to two different power levels, eg "O", ``1''. For example, information can be written in such a manner that the first information corresponds to the code "1" and the second information corresponds to the code "0". In the method of the present invention, these pieces of information can be written continuously within one revolution of the disk using a combination of symbols "O" and "l" without erasing the information that has already been written.

According to a preferred embodiment, the method of the present invention includes a position (first position) in the medium traveling direction at or near a position on the side of the recording medium facing the optical head; Two magnets whose magnetic field directions are opposite to each other are arranged at a certain position (second position) far away in the medium traveling direction, and the first information is written at the first position and the second information is written at the second position. This can be implemented by writing the information in step 2.

According to another preferred embodiment, the method of the present invention includes arranging one permanent magnet at a certain position in the medium traveling direction at or near a certain position on the side of the recording medium facing the optical head; , on the recording medium, the Curie temperature is higher than that of the recording medium, and the coercive force at the highest temperature during recording is larger than the external magnetic field caused by the permanent magnet,
In addition, a magnetic field forming layer made of a perpendicularly magnetized film whose magnetic field at the Curie temperature of the recording medium is smaller than the external magnetic field is provided, and the magnetic field forming layer is magnetized in advance in the opposite direction to the external magnetic field during recording. This can be carried out by writing the first information along with the magnetic field of the magnetic field forming layer and writing the second information along with the magnetic field of the magnetic field forming layer.

The magnetic field forming layer used in the method of the present invention is not particularly limited as long as it satisfies the above conditions. For example, when TbFeCo is used as the recording medium, the magnetic field forming layer can also be made of TbFeCo. In this case, it is only necessary to increase the amount of Co11 to increase the Curie temperature, and Therefore, lamination is easy.Other useful magnetic field forming layer materials include, for example, GdCo, Gd
Examples include FeCo, TbCo, and SmCo. Although it is usually preferable to provide the magnetic field forming layer on the side of the recording medium layer opposite to the substrate, it may be provided on the same side of the recording medium layer as the substrate, if necessary. however,
In this case, the magnetic field forming layer is heated by a laser,
Since this is transmitted to the recording medium layer, it is necessary to take care not to be disadvantageous in terms of recording sensitivity and material selection for the magnetic field forming layer.

[For production]

The operation of the present invention can be fully understood by referring to the recording method shown in the accompanying drawings.

FIG. 1 shows an example of a recording method in which two magnets 6 and 7 are arranged on the side facing an optical head of a magneto-optical disk having a recording medium layer 2 on a substrate 1.

The magnetic field directions of the magnets 6 and 7 are opposite to each other, so that the recording medium layer 2 of the disk 10 is exposed to two external magnetic fields as it moves in the direction of arrow A. The magnet 6 is in the first position (here, a position slightly shifted in the medium traveling direction near the laser beam irradiation part)
Further, the magnet 7 is arranged at a second position (a position further shifted in the medium traveling direction from the first position).

The spacing between the magnets 6 and 7 can be arbitrarily changed depending on the desired result. Laser beam 5 used for recording
is focused by the optical system 4 and then irradiated onto the recording medium layer 2.

When the recording medium layer 2 is irradiated with a laser beam 5 and the recording medium is heated to a temperature slightly higher than the Curie temperature or the compensation temperature (the laser power at this time is M; see Figure 2).
, the recording medium quickly cools down to its Curie or compensation temperature, so that the direction of magnetization follows the external magnetic field by the magnet 6. Next, if the recording medium is heated to a temperature much higher than the Curie temperature or the compensation temperature by irradiation with a laser beam having a higher laser power (denoted as H) than the previously used M, it will take a long time for the recording medium to cool down. , the recording medium has already reached the external magnetic field generated by the magnet 7 when the Curie temperature or compensation temperature is reached. The direction of magnetization of the recording medium at this time therefore follows the external magnetic field generated by the magnet 7.

Therefore, for example, the external magnetic field caused by the magnet 6 becomes information "1".
If the magnetic field is set to 1 and the external magnetic field by the magnet 7 is set to the magnetic field of information "0", as shown in FIG. ), write 11 with a laser beam of power M, and write “0” with a laser beam of power H.
” can be written.

FIG. 3 is an example showing a recording method using a magnetic field forming layer on the recording medium layer of a magneto-optical disk. magneto-optical disk 1
0 has a recording medium layer 2 and a magnetic field forming layer 3 on a substrate l, and can move in the direction of arrow A.

In this recording method, instead of using two magnets as in the method shown in Fig. 1, this magnetic field forming layer 3 is added and an external magnetic field forming layer is provided at a position facing the optical head with the disk as the boundary. A permanent magnet 8 is arranged for this purpose. The magnetic field forming layer 3 has a Curie temperature higher than that of the recording medium (and the coercive force at the highest temperature during recording is thicker than the external magnetic field of the permanent magnet (therefore, the direction of the magnetic field is not reversed by the external magnetic field). The magnetic field at the Curie temperature of the recording medium is smaller than the external magnetic field (therefore, when recording under an external magnetic field, the magnetic field of this medium does not interfere). is previously magnetized in the direction opposite to the external magnetic field.

When the recording medium layer 2 is irradiated with the laser beam 5 focused by the optical system 4 and the recording medium is heated to a temperature slightly higher than the Curie temperature or the compensation temperature (the laser power at this time is M; the fourth Since the recording medium cools down quickly, it is also under the influence of the external magnetic field from the permanent magnet 8 when it reaches the Curie temperature or the compensation temperature, and therefore the direction of magnetization of the recording medium follows the external magnetic field. Next, use a laser power higher than the previously used M (referred to as H; however, this power should not cause the magnetic field forming layer to exceed the Curie temperature).
When the recording medium is heated to a temperature much higher than the Curie temperature or the compensation temperature by irradiation with a laser beam having
Since it takes time for the recording medium to cool down, when the Curie temperature or compensation temperature is reached, the recording medium is outside the external magnetic field, and therefore the direction of magnetization of the recording medium follows the magnetic field forming layer.

Therefore, for example, if the direction of the external magnetic field is set as information "1" and the direction of the magnetic field forming layer is set as information "0", as shown in FIG. "1" can be written with a laser beam of power M, and "0" can be written with a laser beam of power H (therefore, without the need to erase old information).

〔Example〕

Use of two external magnetic fields (Fig. 1) Photopolymer (Mitsubishi Yuka ■) on a glass disk as a substrate
A pre-group pattern was formed using the photopolymer method (2P method).Next, a magneto-optical recording medium containing Tb and Fe as main components was formed by sputtering on the substrate on which the pre-group was formed. It was filmed. The thickness of the recording medium layer of the obtained magneto-optical disk was 1100n, and Tb1. It consisted of Fe, Co11.

To form an external magnetic field, two magnets with a strength of 3000e were bonded together so that the directions of the magnetic fields were opposite. The distance between magnets is 30
It was pm. Set the bonded magnets on the opposite side of the optical head with respect to the magneto-optical disk, making sure that one magnet faces the laser beam and the other magnet faces in the direction of disk travel. did.

First, the magneto-optical disk was rotated at a rotational speed of 90 rpm, and a signal with a frequency of IMIIz was recorded. The power of the irradiated laser beam was 81 on the high side (H) and 2a+W on the low side (M).

A signal with a frequency of 0.5 MHz was recorded on the same track as previously recorded while rotating the disk at the same rotation speed. The power of the irradiated laser beam is 8 mW for high crawl (H) and 211 IW for low crawl (M).
Met. Signal rewriting was confirmed.

According to the findings of the present inventors, the distance between the two magnets bonded together and the placement position of the magnets can be arbitrarily changed depending on the heat capacity of the recording medium, etc. One of the magnetic fields does not necessarily have to face the laser beam, as long as the recording medium passes through the two magnetic fields after being heated.

Use of magnetic field forming layer (FIG. 3) A photopolymer (5A1002 manufactured by Mitsubishi Yukaryo) was spin-coded on a glass disk as a substrate, and a pregroup pattern was formed by the 2P method. Next, Tb was deposited on the substrate on which this pregroup was formed.

A magneto-optical recording medium containing Fe and Co as main components was formed by sputtering. Tbt4Feth*CO with a film thickness of 100 ns
A recording medium layer consisting of s was formed. Subsequently, in the same manner as in the formation of the recording medium layer, Tb1.
Fe5yCoz4 (G to increase the Curie temperature.

A magnetic field forming layer was formed by sputtering.

The obtained magneto-optical disk was rotated at a rotation speed of 600 rpm, with a laser power of 15 mW and an external magnetic field of 3000 e.
Both the recording medium layer and the magnetic field forming layer were magnetized in one direction (O" direction). This operation was performed to align the magnetization direction of the magnetic field forming layer to the "0" direction. It doesn't have to be this way.

That is, for example, when the magnetization of the external magnetic field is in the "0" direction, the magnetization direction of this magnetic field forming layer can be aligned in the "1" direction.

First, the magneto-optical disk was rotated at a rotational speed of 90 rpm, and a signal with a frequency of IMHz was recorded. The power of the irradiated laser beam was 8 mW for high crawl (H) and 2 mW for low crawl (M).

A signal with a frequency of 0.5 Mllz was recorded on the same track as previously recorded while rotating the disk at the same rotation speed. The power of the irradiated laser beam was 8 mW for high crawl (H) and 2 mW for low crawl (M). Signal rewriting was confirmed.

〔Effect of the invention〕

According to the present invention, when rewriting information, it is possible to overwrite new information on top of the old information without erasing it while the disk rotates once, thereby significantly reducing the time required for rewriting. can be shortened to Further, according to the present invention, this overwriting can be easily performed without using a complicated device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a preferred example of the recording method of the present invention, FIG. 2 is a waveform diagram of a rewriting pulse for carrying out the recording method of FIG. 2, and FIG. 3 is a diagram showing a preferred example of the recording method of the present invention. A schematic diagram showing another preferred example of the recording method, FIG. 4 is a waveform diagram of a rewriting pulse for carrying out the recording method of FIG. 3, and FIG. 5 shows an example of a conventional recording method. FIG. 6 is a waveform diagram of a rewriting pulse for carrying out the recording method of FIG. 5. In the figure, 1 is a substrate, 2 is a recording medium layer, 3 is a magnetic field forming layer, 4
5 is an optical system, 5 is a laser beam, 6 and 7 are magnets, and 10 is a magneto-optical disk.

Claims (1)

[Claims] 1. A method for recording information on a magneto-optical disk by overwriting, in which two types of magnetic fields with opposite magnetization directions are formed in the traveling direction of the recording medium, and Information is recorded by irradiating a recording medium with two types of laser beams with different intensities so that as the recording medium advances, a point below its Curie temperature or compensation temperature appears in each of the magnetic fields. A recording method characterized by: 2. Irradiate the recording medium with a laser beam that has an intensity that can heat the medium to a temperature slightly higher than the Curie temperature or compensation temperature of the medium, and then Write first information at a certain position, and irradiate the recording medium with a laser beam having an intensity that can heat the recording medium to a higher temperature than when writing the first information, and write the first information at the writing position. 2. The recording method according to claim 1, wherein the second information is written at a certain position further away in the direction of travel of the medium. 3. The recording method according to claim 2, wherein the first and second information are written by converting into codes having two different power levels. 4. At or near a certain position on the side of the recording medium facing the optical head in the medium traveling direction, and at a position further away from that position in the medium traveling direction,
The recording method according to claim 2, wherein two magnets are arranged with magnetic field directions opposite to each other, and first information is written at the former position and second information is written at the latter position. . 5. A patent in which the information is to be converted into codes "0" and "1" and written, and in this case, the first and second information correspond to the codes "1" and "0", respectively. A recording method according to claim 4. 6. The recording method according to claim 5, wherein the information is written continuously during one rotation of the disk by a combination of codes "0" and "1". 7. A permanent magnet is disposed at or near a certain position on the side of the recording medium facing the optical head in the medium traveling direction, and a permanent magnet is placed on the recording medium at a Curie temperature lower than that of the recording medium. a magnetic field forming layer made of a perpendicularly magnetized film, which has a high coercive force at the highest temperature during recording than the external magnetic field by the permanent magnet, and whose magnetic field at the Curie temperature of the recording medium is smaller than the external magnetic field,
The magnetic field forming layer is magnetized in advance in a direction opposite to the external magnetic field during recording, and first information is written in accordance with the external magnetic field, and second information is written in accordance with the magnetic field of the magnetic field forming layer. 3. The recording method according to claim 2, wherein the recording method is written. 8. A patent in which the information is to be converted into codes "0" and "1" and written, and in this case, the first and second information correspond to the codes "1" and "0", respectively. A recording method according to claim 7. 9. The recording method according to claim 8, wherein the information is written continuously in one revolution of the disk by a combination of codes "0" and "1".