JPH07153127A - Magneto-optical recording medium, reproducing method thereof, and manufacture of master disk and the medium - Google Patents

Abstract

PURPOSE:To enable the super-high resolving operation at a low operating temp. and to read track pitch by providing a magneto-optical film having different coercive force corresponding to the information to be recorded on the substrate. CONSTITUTION:A magneto-optical film 11 is formed on the substrate 21 through the first protective film 22 consisting of a dielectric film. In this case, as the substrate 21, a glass substrate formed with a V-shaped track guide groove having a 1.4mum track pitch is used and as the first protective film 22, a silicon nitride film having 100nm thickness is used. On the magneto-optical film 11, the second protective film 23 consisting of a dielectric film and the third protective film 24 consisting of a resin layer are formed. By using such structure of the medium, a high signal level can be secured even for a shorter mark length and the reproduction only recording medium of high density can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium used for recording information, particularly an external storage device of a computer, a video or audio recording device, a storage device such as a game machine, or a multimedia in which these are integrated. And a reproducing method and a manufacturing method.

[0002]

2. Description of the Related Art Recently, a read-only optical recording medium is a CD.
(Compact disc), LD (Laser disc), CD-
It is widely used for voice, video and data files such as ROM. However, in recent years, with the spread of optical recording media, the data to be handled has become widespread, and the demand for higher density has increased. As one of the solutions, a method of reproducing a recording mark having a diameter smaller than the laser spot diameter by a method described below has been proposed for a rewritable magneto-optical recording medium. This is a configuration in which the recording layer and the reproducing layer are separately provided, and a state in which the information recorded in the recording layer is transferred to the reproducing layer only in a limited narrow area of the reproducing beam irradiation area. This is a method of reproducing while forming, and is a method called super-resolution reproduction.

This is a system disclosed in Japanese Patent Laid-Open No. 3-93058, and is basically composed of two layers of perpendicularly magnetized films, a recording layer having a high coercive force and a reproducing layer having a low coercive force. The exchange coupling force acts between the membranes. Next, the reproducing principle of the magneto-optical recording medium having this structure will be briefly described.
At room temperature, a strong external magnetic field (3 Koe or more) causes only the magnetization of the reproducing layer to align in one direction. However, the coercive force of the reproducing layer sharply decreases in the region where the reproducing beam is irradiated and the temperature rises, and the recording mark of the recording layer is transferred to the reproducing layer by the exchange coupling action. Therefore, a signal is generated only from a portion whose temperature is raised by the reproduction beam irradiation, and no signal is generated from a portion of the reproduction beam irradiation region where the temperature is not raised.

This system, like the conventional magneto-optical recording,
It is an effective method for recording media that users record,
It does not apply to read-only optical recording media. As a method for performing super-resolution reproduction on a reproduction-only optical recording medium, there is a method of utilizing the difference between the reflectance in the solid phase state and the reflectance in the liquid phase state (Yasuda et al. International Symposium Opt.
ical Memory and Optical Data Storage '93 Th
3.2, 1993). In this structure, GeSbTe is provided on a substrate on which information is recorded in the form of pits, and a reflective film is further laminated. Next, the reproduction principle of the optical recording medium having this structure will be briefly described. At the room temperature, GeSbTe is in a solid phase state when light is input from the substrate side for reproduction.
Since bTe has a large light transmittance, a certain amount of reflected light can be obtained. However, when the temperature is raised by the reproduction beam,
GeSbTe is in a liquid state, the light transmittance of GeSbTe is drastically reduced, and the reflected light becomes extremely small. Therefore, the reproduced signal is limited to only the low temperature portion of the reproduction beam irradiation area, and super-resolution reproduction can be performed on the reproduction-only optical recording medium.

[0005]

However, the above structure has the following drawbacks. The first drawback is that in order to constantly reproduce while heating to the liquid phase state of GeSbTe, the temperature must be several hundreds of degrees or more at the time of reproduction, and extremely high power is required although it is dedicated to reproduction. This not only requires a high-power laser, but also poses a problem of causing deterioration of the substrate due to repeated reproduction or deterioration of the GeSbTe film. A second problem is that the high temperature part of the light beam irradiation area is masked and only the low temperature part is reproduced, so that crosstalk between adjacent tracks is easily picked up and it is difficult to reduce the track pitch. Furthermore, as the third issue,
It is difficult to use a part of the recording medium as a read-only memory and another part as a re-recordable recording medium, a so-called partial ROM, or a rewritable data file having read-only address information and management information. Is mentioned. That is, the GeSbTe film itself is a rewritable recording medium that uses a reversible change between a crystalline state and an amorphous state. However, even when the film is always in the liquid phase state, that is, even if information is recorded, The information is reproduced while erasing it, and the information recorded in the phase change cannot be reproduced again. In view of the above problems, the present invention is
It is possible to provide a read-only magneto-optical recording medium capable of performing a super-resolution operation at a low operating temperature, narrowing a track pitch, and arranging on the same plane as a rewritable recording medium. It is intended.

[0006]

In order to achieve the above object, the magneto-optical recording medium of the present invention is provided with a magnetic film having a different coercive force on at least a part of the medium in accordance with information to be recorded. It is equipped with a structure that is.

[0007]

The present invention provides a read-only optical recording medium or a write-once optical recording medium capable of performing a super-resolution operation at a low operating temperature and having a narrower track pitch by the above-mentioned structure. Furthermore, it is possible to arrange the recording medium on the same surface as the rewritable recording medium. Next, the principle will be described in more detail with reference to the drawings. That is, the generation principle of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 11 is a magneto-optical film, which is composed of a low coercive force portion 11a and a high coercive force portion 11b corresponding to recorded information, and has an arrangement as shown in FIG. Reference numeral 12 is a light beam (reproduction beam) irradiated during reproduction, 13 is an initialization magnetic field for initialization, and 14 is a bias magnetic field. Curve 15 is the temperature curve of the magneto-optical film during reproduction,
It corresponds to the irradiation position of (reproduction beam) 12. Also the curve
16 indicates the temperature curve of the coercive force of the high coercive force part (11b),
7 shows the temperature curve of the coercive force of the low coercive force portion (11a).

Next, the reproducing principle will be described. Prior to irradiation with the reproducing beam, the magneto-optical film 11 is uniformly magnetized upward (or downward) by the initialization magnetic field 13. At this time, the magnetic field strength H2 of the initializing magnetic field 13 is required to be equal to or higher than the coercive force H3 of the high coercive force portion 11b at room temperature. When the recording medium moves and is irradiated with the reproducing beam 12, the temperature of the magneto-optical film 11 changes like a temperature curve 15 of the magneto-optical film. At this time, a weak bias magnetic field 14 having a direction opposite to the initializing magnetic field is applied, and its magnetic field strength is H1.

Although the temperature rises with the irradiation of the reproducing beam 12, both the low coercive force portion 11a and the high coercive force portion 11b have a coercive force larger than that of the bias magnetic field 14 until the temperature T1 is reached. Does not change at all. However, in the temperature region higher than T1 and lower than T2, the bias magnetic field strength H1 is superior to the coercive force in the low coercive force portion 11a shown by the temperature curve 17, so that the magnetization is reversed according to the direction of the bias magnetic field 14. On the other hand, in the high coercive force portion 11b, the coercive force indicated by the temperature curve 16 is superior to the bias magnetic field strength H1, so that the magnetization does not reverse but remains in the direction determined by the initializing magnetic field 13. When the temperature further rises and becomes higher than T2, the bias magnetic field strength H1 is superior to the coercive force in the high coercive force portion 11b shown in the temperature curve 16,
The magnetization is inverted according to the direction of the bias magnetic field 14. That is, only in the region X where the temperature is T1 or higher and T2 or lower,
A state in which the magnetization is reversed is created according to the recorded information, which contributes to reproduction.

A recording medium for realizing such super-resolution reproduction can be realized as long as it is a magnetic film having a different coercive force depending on the recorded information. Further, as a reproducing method for realizing super-resolution reproduction using such a recording medium, it is necessary to reproduce while raising the temperature to T2 or more and the bias magnetic field 14, but the initialization magnetic field 13 Is not always necessary. That is, in the principle diagram of FIG. 1, the initialization magnetic field is provided just before the reproduction so as to be aligned with the upward magnetic field. However, since the magnetic field is uniformly downward after the reproduction, the bias magnetic field is set upward during the next reproduction. By
It is also possible to omit the initialization magnetic field. This method
This is convenient for ensuring compatibility with the conventional super-resolution reproduction method.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical recording medium according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the principle of reproduction of a magneto-optical recording medium in the first embodiment of the present invention, and FIG. 2 shows the structure of the recording medium of the first embodiment. In FIG. 1, 11 is a magneto-optical film made of GdTbFeCo, having a coercive force of 900 oe at room temperature, a Curie point of 350 ° C. or higher, and a compensation temperature of 0 ° C. or lower. This magneto-optical film 11 is
As shown in FIG. 2, it is formed on the substrate 21 via the first protective film 22 made of a dielectric film. Here, a glass substrate having a V-shaped track guide groove with a track pitch of 1.4 μm is used as the substrate 21, and the first protective film 22 has a thickness of
A 100 nm silicon nitride film was used. A second protective film 23 made of a dielectric film and a third protective film 24 made of a resin layer are formed on the magneto-optical film 11. Here, a silicon nitride film having a thickness of 100 nm is used as the second protective film 23, and a urethane resin having a thickness of 5 μm is used as the third protective film 24. The structure of these films is exactly the same as the structure conventionally proposed. The characteristic of the first embodiment is that the magneto-optical film 11
As shown in FIGS. 1 and 2, a low coercive force portion 11a and a high coercive force portion 11b corresponding to the information to be recorded are provided. In the first embodiment, as shown in FIG. 2, the portion corresponding to the recording mark portion was a low coercive force portion, and the portion corresponding to the non-recording mark portion was a high coercive force portion.

Next, according to the information to be recorded,
A method of manufacturing a magneto-optical film having different coercive force will be described. The device configuration for generating recording marks with different coercive force is
It is basically the same as the conventionally proposed recording device. Using such a recorder, linear velocity 1.3m / s, pulse width 1
Light pulses were emitted at various pulse intervals with 00 ns and a peak power of 12 mW. Under this condition, the perpendicular magnetic anisotropy is deteriorated at the beam irradiation portion with a power more than twice that of ordinary magneto-optical recording, and as a result, the coercive force is lowered. After the recording medium irradiated with the optical pulse by such means was first uniformly magnetized at 2 Koe or more and then re-magnetized at 500 oe in the opposite direction, no reproduction signal was obtained. However,
When the signal was reproduced after being uniformly magnetized at 2 Koe or more and then re-magnetized at 600oe in the opposite direction, the signal corresponding to the recorded signal could be reproduced. Therefore, under the conditions of the first embodiment, it can be seen that the coercive force in the beam irradiation portion is reduced to about 600 oe or less. In the first embodiment, the low coercive force portion 11a is formed by turning on / off the semiconductor laser based on the information to be recorded, but the argon laser is used to turn on / off the EO modulator.
Off is also effective. In particular, the recording mark forming method as shown in the first embodiment is effective as a write-once disc rather than as a read-only disc because the low coercive force portion 11a can be formed by an ordinary optical disc drive.

With respect to the magneto-optical recording medium having the above-mentioned structure, it was first confirmed using a polarization microscope that the recording magnetic domains could be formed with increasing temperature. At first
After the entire recording medium was magnetized at 1.2 Koe, the formation of magnetic domains was observed with a polarization microscope while heating the recording medium with a sheath heater while applying a magnetic field of 400 oe. As a result, magnetic domains were not observed at room temperature at all, whereas magnetic domains recorded by heating at 110 ° C or higher appeared, and when heated further, 190
The magnetic domains disappeared again above ℃. This is 110 ℃ to 190 ℃
In the temperature range up to, the magnetization reversal occurs in a magnetic field of 400oe only at the portion where the coercive force has decreased due to the irradiation of the recording optical pulse,
The above means that the magnetization is inverted even in the portion not irradiated with the light pulse. From these experiments,
In Example 1, when H1 shown in FIG. 1 is 400 oe, T1 is 110 ° C. and T2 is 190 ° C.

Next, reproduction was performed with the magneto-optical reproducing apparatus shown in FIG. The linear velocity is 5 m / s. In particular, a characteristic of reproducing the magneto-optical recording medium of the present invention is a magnetic field applying means.
32, and the others are no different from the conventional magneto-optical reproducing apparatus proposed in the past. Magnetic field applying means 32
As shown in FIG. 3, the initialization magnetic field 13 from the S pole and the bias magnetic field 14 from the N pole are applied to the magneto-optical film 11, and the bias magnetic field 14 from the N pole is applied to the reproducing beam position. There is. Since each magnetic field may always have a constant direction and a constant strength, the magnetic field applying means 32 is preferably a permanent magnet in the sense of reducing power consumption and downsizing. Also,
By constructing the disk in such a size that the recording area can be covered in the radial direction, it is not necessary to move the magnetic field applying means 32, which is more effective. In the first embodiment,
The initialization magnetic field 13 on the surface of the magneto-optical film 11 was 1.2 Koe, and the bias magnetic field 14 from the N pole was 400 oe.

The reproduction results are shown below. FIG. 6 (a) shows the signal level when the recorded data is reproduced at various pulse intervals. For reference, the signal level during normal recording and reproduction is also shown. Note that the mark length on the horizontal axis means the length of 1/2 of the recorded mark interval, and the signal level on the vertical axis is plotted with the signal level when the mark length is 2 μm as 0 dB. Figure 6
As can be seen from (a), according to this embodiment, a large signal level can be secured even for a smaller mark length, and a high density write-once and recording medium can be realized. The magneto-optical super-resolution reproducing method particularly suitable for the write-once disc has been described above as the first embodiment.

Next, a second embodiment particularly suitable for reproduction only will be described with reference to the drawings. Figure 2 is the second
3 shows a method for manufacturing a magneto-optical recording medium in the example of FIG. In FIG. 4, reference numeral 401 is a master, 402 is a photoresist, 403 is an argon laser beam, 404 is an ion particle (ion shower), 405 is ultraviolet rays, 406 is a stamper, 407 is a substrate, 408 is a magneto-optical film, and 409 is magneto-optical. Scattered particles that make up the film
(Sputtered particles). Also, 410 is the low coercive force part 11a.
And 411 is a Kerr hysteresis loop of the high coercive force portion 11b.

The steps will be described below in order. The manufacturing procedure is in the order of (a) (b) (c) ... That is, (a) with respect to the photoresist 402 applied on the master 401 polished to a mirror surface,
Cutting exposure is performed with an argon laser beam 403 whose intensity is modulated according to the information to be recorded. (b) After development,
By etching, a portion where the photoresist 402 is removed and a portion where the photoresist 402 is not formed are formed according to the information to be recorded. The procedure up to this point is exactly the same as the conventional procedure.

[0018]

[Outer 1]

(D) After the ion etching is completed, the master 4
The exposed portion of 01 and the surface of the photoresist 402 form a rough surface. (e) After that, the photoresist 405 formed on the master is removed by irradiating with ultraviolet rays 405, (f) developing again and then etching. (g) After that, N
After i-sputtering, a stamper 406 is formed by electroforming using the sputter. (h) After that, the stamper 406 is peeled off, and a rough surface portion and a mirror surface portion are formed according to the information to be recorded.
Is completed. (i) Using the stamper 406, a substrate 407 corresponding to the surface roughness of the stamper 406 is formed by injection or a photopolymer method. In the second embodiment, the substrate was manufactured by the photopolymer method, but it is also possible to use polycarbonate or an olefin resin for injection. (j) After that, the substrate is separated from the stamper 406 to complete the substrate 407. (k) Using the completed substrate 407, the same GdTbFeCo as shown in the first embodiment was formed by sputtering.
(l) By the above procedure, the magneto-optical film 408 having the rough surface portion and the mirror surface portion is formed according to the information to be recorded. The magneto-optical film formed on the mirror surface portion has a low coercive force and has the characteristics shown in the Kerr hysteresis loop 410. On the other hand, the magneto-optical film formed on the rough surface has a low coercive force and has the characteristics shown by the Kerr hysteresis loop 411. This is considered to occur because the movement of the domain wall is hindered by the pinning effect in the rough surface portion. The produced magneto-optical disk is magnetized once in a high magnetic field of 5 Koe or more and then re-magnetized in the opposite magnetic field. As a result, it is recorded with a polarization microscope only when it is re-magnetized in the range of 700 to 800 oe. The magnetic domain was observed according to the information that should be obtained. From this, the coercive force H4 of the low coercive force portion 11a of the mirror surface portion is 700
It can be seen that the coercive force H3 of the high coercive force portion 11b of the rough surface portion is about 800 oe.

Using the disk configured as described above,
As a result of reproducing by the reproducing apparatus shown in FIG. 3, the result shown in FIG. 6 (b) was obtained. Similar to FIG. 6A, the signal level at the time of normal recording and reproduction is also shown for reference.
The vertical axis and the horizontal axis are the same as in FIG. 6 (a). Figure 6
As can be seen from (b), according to this embodiment, a large signal level can be secured even for a smaller mark length, and a high-density read-only recording medium can be realized. According to this method, the size of the recording magnetic domain is
Since it can be specified by an argon laser having a wavelength much shorter than that of a semiconductor laser, the density can be made higher than that of the conventional magneto-optical recording.

[0021]

[Outside 2]

In the second embodiment, in order to achieve the conventional recording density which does not require the super-resolution operation, after the film formation, the first magnetic field larger than the coercive force of the high coercive force portion is used. After magnetization, recording is performed by re-magnetizing with a second magnetic field that is smaller than the coercive force of the high coercive force portion, greater than the coercive force of the low coercive force portion, and that is opposite to the first magnetic field. It is possible to form magnetic domains corresponding to the desired information. In this case, it is not necessary to apply a magnetic field during reproduction. In order to realize a magneto-optical disk by this method, the stability of the recording magnetic domain is strictly required, so the coercive force of the low coercive force part is 7 Ko.
It is desirable to be e or more.

Since the second embodiment has been described mainly with respect to the part relating to the present invention, the tracking method has not been described in detail. However, the present invention is applicable to any of the method of using the recorded magnetic domain as the signal source of the tracking servo, the sample servo method, and the track guide groove method. Hereinafter, some explanation will be added to these matters. As a method of using the recorded magnetic domain as the first method as a signal source of the tracking servo, there are three methods.
There is a beam method. This is because the light beam is divided into three by the grating into the 0th order light and the two 1st order lights, and while the signal is reproduced by the 0th order light at the center, the signals from adjacent tracks on the left and right are equalized by the 1st order left and right lights. A method of applying a tracking servo so that it can be detected can be used as it is with only the contents described in the second embodiment.

In the sample servo system, which is the second method, wobble pits, which are generally called, are required to be offset from the track center to the left and right. In the conventional method, in the laser cutting shown in FIG. 4A, two modulators are used to form a wobble pit by irradiating an area corresponding to the wobble pit with an argon laser for laser cutting. Also for the present invention, wobble pits can be formed in exactly the same manner as shown in FIG. However, as shown in FIG. 4, as a result, the magnetic domains are formed based on the difference in the surface roughness between the portion irradiated with the argon laser during cutting and the portion not irradiated with the argon, not the depth. Therefore, the expression wobble domain is more appropriate than the wobble pit. However, the servo method of applying the tracking servo so that the signal from the magnetic domain wobbled to the right of the wobble domain and the signal from the magnetic domain wobbled to the left have the same magnitude is different from the conventional wobble pit method. It can be realized without any change in principle.

The track guide groove method, which is the third method, can also be realized by slightly modifying the manufacturing procedure shown in FIG. It is shown in FIG. Hereinafter, description will be made step by step. (a) A photoresist 402 coated on the master 401 in a thickness corresponding to the groove depth is subjected to cutting exposure with an argon laser beam 403 having a constant intensity. (b) After development, etching is performed to form a portion where the photoresist 402 is removed and a portion where the photoresist 402 is not removed in the form of a groove. The procedure up to this point is exactly the same as the conventional procedure.
(c) Next, the focused master ion beam generated by the ion source, the lens, and the deflector is turned on / off according to the signal to be recorded, and the exposed master 401 is scanned. In this case, the lens may be magnetic or electrostatic, but a combination of an aperture combination lens, a quadrupole electrostatic lens, etc. is preferable for ease of control. The deflector is used for the ion beam to follow the groove portion where the master 401 is exposed. The voltage applied to the deflector is fed back from the detection of the amount of eccentricity by the optical head. (d) As a result,
Corresponding to the signal to be recorded in the groove, a portion (rough surface portion) area a irradiated with the ion beam and a portion (mirror surface portion) area b not irradiated with the ion beam are formed.

(E) Then, after performing Ni sputtering, the stamper 406 is formed by electroforming using the Ni sputtering as an electrode. (f) After that, the stamper 406 is peeled off, and the stamper 406 having the rough surface portion and the mirror surface portion formed according to the information to be recorded is completed. (g) Stamper 406
Using, the substrate 407 corresponding to the surface roughness of the stamper 406 is formed by the injection or photopolymer method. (h) After that, the substrate 407 is completed by peeling the substrate from the stamper 406. (i) Completed board 40
The magneto-optical film is sputtered using 7. (j) By the above procedure, the magneto-optical film 408 having the rough surface portion and the mirror surface portion formed in the track guide groove is formed according to the information to be recorded.
The magneto-optical film 408 formed on the mirror surface portion has a low coercive force and has the characteristics shown by the Kerr hysteresis loop 410. On the other hand, the magneto-optical film formed on the rough surface has a low coercive force and has the characteristics shown by the Kerr hysteresis loop 411.

By using such a method, it is possible to manufacture a magneto-optical recording medium having a different coercive force depending on the information to be recorded, even in a disk provided with a track guide groove. As described above in the first and second embodiments, according to the present invention, it is possible to perform super-resolution reproduction with a single-layer magnetic film for a write-once or read-only magneto-optical disk, and achieve high-density recording. It turns out that the medium can be realized. However, rewritable recording / reproduction cannot be realized with a single magnetic film. However, it is also effective to realize the conventionally proposed super-resolution reproducing film structure by using the substrate manufactured by the method shown in the second embodiment.

For example, as disclosed in Japanese Patent Laid-Open No. 3-93056, a front aperture type super-resolution reproducing system is disclosed in Japanese Patent Laid-Open No. 3-93056.
A rear aperture type super-resolution reproducing method disclosed in Japanese Patent Laid-Open No. 93058, a double-aperture type super-resolution reproducing method disclosed in Japanese Patent Laid-Open No. 4-271039, and Japanese Patent Laid-Open No. 5-81717.
This is a super-resolution reproduction system that utilizes the change from an in-plane magnetized film to a perpendicular magnetized film as disclosed in Japanese Patent Laid-Open Publication No. As common to these various super-resolution reproduction methods, at least a recording layer and a reproduction layer are provided separately, and recording marks are provided on the recording layer by a conventional magneto-optical recording method (optical modulation or magnetic field modulation). It is formed. It means that the super-resolution reproduction is realized while locally transferring the magnetization formed in the recording layer to the reproduction layer by utilizing the temperature rise due to the reproduction beam during reproduction.
The essential idea of super-resolution reproduction is common, and various systems have been proposed depending on the transfer method for transferring the magnetic domain of the recording layer to the reproducing layer.

The present invention relates to the formation of recording magnetic domains, and instead of the conventional magneto-optical recording method (optical modulation or magnetic field modulation), the recording magnetic domains are formed by utilizing the difference in coercive force. The magneto-optical film having the recording magnetic domain formed according to the present invention as a recording layer is provided with a reproducing layer separately, and the conventional super-resolution method listed above can be used as it is. In this case, the recording layer should have at least 10 μm in order to use transfer using exchange coupling force and, in some cases, to prevent the recorded domain in the initializing magnet from being affected.
Must be Koe or better. The formation of the recording magnetic domain at this time is achieved by the following method. After film formation, after being magnetized with a first magnetic field larger than the coercive force of the high coercive force part, smaller than the coercive force of the high coercive force part and greater than the coercive force of the low coercive force part,
Further, by re-magnetizing with the second magnetic field in the direction opposite to the first magnetic field, it is possible to form the magnetic domain corresponding to the information to be recorded.

In particular, the method used in combination with this conventional super-resolution reproducing method is effective in realizing a partial ROM disk in which rewritable information and reproduction-only information are mixed.

In the first embodiment, the glass substrate was used, but this was used for the microscopic observation while raising the temperature, and the original method of use for recording / reproducing was only used. If so, a resin substrate such as a polycarbonate substrate, an olefin substrate, a PMMA substrate, or the like can be used. Although GdTbFeCo was used for the magnetic film, the present invention is not limited to this. Any magneto-optical material can be used as long as it can form a part having a different coercive force corresponding to the information to be recorded. In particular, when the magnetic layer is composed of a single layer as in the first and second embodiments, a material having a small coercive force at room temperature and a relatively high Curie point is desirable. The reason why the coercive force at room temperature is preferably small is that the magnetic field for initialization can be made small. In terms of downsizing the device, the coercive force at room temperature should be 3 Koe or less, preferably 1 Koe or less. Is desirable. Further, in the structure in which the reproducing layer is provided separately from the recording layer, the recording layer needs to have a large coercive force at room temperature, and is preferably 10 Koe or more. This is because the magnetic domains formed in the recording layer need to have long-term stability. Further, regarding the film structure, the present invention is the essential constitutional requirement of the present invention that a magneto-optical film having different coercive force corresponding to the information to be recorded is present, and the dielectric film, the reflection film, the protective film, etc. It is provided as appropriate in order to secure or improve various characteristics such as reliability, signal quality, and heat distribution during recording or reproduction.
Further, the magnetic field applying means can be constituted by a permanent magnet as in the first and second embodiments, or can be constituted by an electromagnet such as a flying head.

[0032]

As is apparent from the above embodiments, according to the present invention, by providing a magneto-optical film having a different coercive force corresponding to information to be recorded on a substrate, super-resolution reproduction and high density can be achieved. It is possible to realize a reproduction-only or write-once or partial ROM disk. In particular, since the super-resolution operation can be performed with a single-layer magnetic film and the configuration without exchange coupling is possible, the initialization magnetic field can be reduced to 1
It can be made much smaller than Koe and conventional, and it is effective for downsizing of equipment.

[Brief description of drawings]

FIG. 1 is a principle diagram illustrating an operation of the present invention.

FIG. 2 is a configuration diagram of a recording medium according to the first embodiment of the present invention.

FIG. 3 is a perspective view of a basic portion of the reproducing apparatus according to the embodiment of the present invention.

FIG. 4 is a diagram showing a procedure for manufacturing a recording medium according to the second embodiment of the present invention.

FIG. 5 is a diagram showing a procedure for manufacturing a recording medium by a method different from that of the second embodiment of the present invention.

FIG. 6 is a characteristic diagram in an example of the present invention.

[Explanation of symbols]

11, 408 ... Magneto-optical film, 11a ... Low coercive force portion, 11b ... High coercive force portion, 12 ... Reproducing beam, 13 ... Initializing magnetic field, 14 ...
Bias magnetic field, 15 ... Temperature curve of magneto-optical film, 16 ... Temperature curve of coercive force of high coercive force portion, 17 ... Temperature curve of coercive force of low coercive force portion, 21, 407 ... Substrate, 22 ... First protective film ,
23 ... Second protective film, 24 ... Third protective film, 32 ... Magnetic field applying means, 33 ... Objective lens, 34 ... Beam splitter, 401 ... Master, 402 ... Photoresist, 403 ... Argon laser beam, 404 ... Ion Particles, 405 ... Ultraviolet rays, 406 ... Stampers, 409 ... Sputtered particles,
410… Kerr hysteresis loop of low coercive force part, 411… Kerr hysteresis loop of high coercive force part.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G11B 11/10 E 8935-5D

Claims (6)

[Claims] 1. A magneto-optical recording medium, wherein a magnetic film having different coercive force corresponding to information to be recorded is provided on at least a part of a substrate. 2. A magneto-optical recording medium, characterized in that at least a part of a substrate has different surface roughness corresponding to information to be recorded. 3. A magneto-optical recording medium characterized in that at least a part thereof has a magnetic domain array whose size is limited by an argon laser. 4. A master is formed by ion-etching at least partly after realizing a state in which a photoresist is applied and a state in which a photoresist is not applied corresponding to information to be recorded on the original disc. , A method of manufacturing a master, which is characterized in that different surface roughnesses corresponding to information to be recorded are realized. 5. A magneto-optical recording medium in which at least a part of a magneto-optical recording medium, the size of which is restricted by an argon laser, is reproduced by a semiconductor laser. How to play media. 6. In manufacturing a magneto-optical recording medium, at least a part of which is provided with a magneto-optical recording film having different coercive forces H _C1 and H _C2 corresponding to information to be recorded, the magneto-optical recording film comprises: after provided, after magnetized with a large first magnetic field than either H _C1 and H _C2, H _C1 and H _C2
A method for manufacturing a magneto-optical recording medium, characterized in that the magnetic field is re-magnetized in the middle of the magnetic field and in a magnetic field opposite to the first magnetic field.