JPH08129784A - Magneto-optical recording medium and its recording and reproducing method as well as recording and reproducing device therefor - Google Patents

Abstract

PURPOSE: To obtain a magneto-optical recording medium with which multi-valued recording of signals is possible and a many valued recording and reproducing system adequate for this medium. CONSTITUTION: A first recording layer 4 in which a recording state exists in one different magnetic field region to an external magnetic field to be impressed and a second recording layer 6 in which two recording states exist in the magnetic field region different from the magnetic field region of the first recording layer are laminated on the surface formed with preformat patterns 2 of a transparent substrate 1. Lamination of dielectric layers 3, 5, 7, a reflection layer 8 and a protective layer 9 is possible as well at need. The quaternary recording of information is made possible by allotting '1' and '0' and '3' and '2' of information signals respectively to H0 and H1 and H2 and H3 . As a result, the matching of the respective recording layers, light beams for recording and external magnetic fields is facilitated and the magneto-optical system having excellent stability and mass productivity is built.

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, a recording / reproducing system therefor, and a recording / reproducing apparatus therefor, and more particularly to a laminated structure of magnetic layers of a magneto-optical recording medium capable of multilevel recording, The present invention relates to a multi-value recording method using a medium and a configuration of a magnetic head suitable for multi-value recording on a magneto-optical recording medium.

[0002]

2. Description of the Related Art In the field of magneto-optical recording media, increasing the recording density has become one of the most important technical problems. Conventionally, as means for increasing the density of the magneto-optical recording medium, for example, page 63 of the 13th Japan Society for Applied Magnetics Academic Lectures (published in 1989) and Japanese Journal o.
f Applied Physics, Vol.28 (1989) Supplement 28-3 pp.3
As described in 43-347, a method of multilevel recording of a signal has been proposed. In the known multi-value recording method, a plurality of magnetic layers having different coercive forces are laminated and the magnetic field strength applied to the magnetic layers is modulated in multiple steps to selectively reverse the magnetization of a specific magnetic layer. It is to let. According to these methods, four-value recording of signals is possible by providing three magnetic layers having different coercive forces.

[0003]

However, according to the multi-valued recording method according to the known example, when the magneto-optical recording medium is irradiated with a laser beam at the time of recording a signal and each magnetic layer is heated to a temperature near the Curie temperature, In addition, since there is almost no difference in coercive force between the magnetic layers, it is practically difficult to selectively reverse the magnetization of each magnetic layer. Suppose that the magnetic characteristics of each magnetic layer are strictly adjusted, and the laser intensity and external magnetic field intensity at the time of recording are strictly controlled, so that the magnetization of each magnetic layer can be selectively reversed at the laboratory level. Even if it becomes, mass production of such a magneto-optical recording medium and a recording / reproducing device is impossible in terms of cost. In addition, since the margin for fluctuations in laser intensity and external magnetic field intensity during recording is extremely small, it is impossible to maintain a stable recording / reproducing state for a long period of time, which is extremely impractical. If the signals are recorded in a state where the difference in coercive force between the magnetic layers is sufficiently large without raising the temperature of each magnetic layer to near the Curie temperature, such inconvenience does not occur.
On the other hand, since a large magnetic field is required for recording and erasing signals,
Since a magnetic field generator such as a magnetic head becomes large in size, a recording / reproducing device becomes large in size, and power consumption also increases, another serious inconvenience occurs, so that practical application is practically impossible.

The disadvantages of the prior art will be described in more detail below with reference to FIG. 142. Here, in order to facilitate the description, an optical film in which two layers of magnetic films (magnetic layers) having temperature characteristics of coercive force indicated by reference characters A and B in FIG. A magnetic recording medium will be described as an example.

Since the irradiation portion of the recording laser beam is heated to the Curie temperature of each magnetic layer or higher, the coercive force of each magnetic layer is largely different at room temperature as shown in FIG. 142 (b). However, the difference becomes extremely small in the temperature rising part. Therefore, it is practically difficult to selectively reverse the magnetization of each magnetic layer.

A recording laser beam irradiation unit is shown in FIG.
As shown in FIG. 2 (a), there is a steep temperature distribution that reaches from the room temperature to the Curie temperature or higher in the minute region.
Therefore, the distribution of the coercive force in each magnetic layer in the region corresponding to that becomes steep as shown in FIG. 142 (c), and the size of the recording domain is slightly small regardless of the applied magnetic field. However, the two magnetic layers cannot be recorded separately by the magnitude of the applied magnetic field.

The carrier-to-noise ratio of the signals read from the magnetic layers A and B is as shown in FIG. 142 (d) with respect to the external magnetic field strength during recording. That is, the carrier-to-noise ratio of the signal read from the magnetic layer A and the carrier-to-noise ratio of the signal read from the magnetic layer B are the transitions between the unrecorded area and the recorded area with respect to the external magnetic field strength during recording. The areas almost overlap with each other, and they are slightly shifted due to the difference in the leakage magnetic field to the recording portion due to the difference in the magnetizations. Therefore, in the magneto-optical recording medium in which these magnetic layers A and B are laminated, the carrier-to-noise ratio of the read signal is stable as shown in FIG. 142 (e).
Therefore, it is impossible to multivalue the recording signal by switching the external magnetic field.

Further, in the conventional technique, there is an inconvenience that direct overwriting of signals cannot be performed. That is, for example, the magnetic layer (A layer) having the coercive force-temperature characteristic of A and the magnetic layer (B layer) having the coercive force-temperature characteristic of B shown in FIG. In the magneto-optical recording medium, when an external magnetic field having a magnitude of H ₁ shown in FIG. 142 (b) is applied, only the B layer undergoes magnetization reversal as shown in FIG. 143 (b). When an external magnetic field having the magnitude of H ₂ shown is applied, both the A layer and the B layer undergo magnetization reversal, as shown in FIG. 143 (c). Therefore, in addition to the state of FIG.
When trying to record the state of
_After the magnetic field of ₂ is applied to return to the initial state (FIG. 143 (a)) and then the magnetic field of H ₁ is applied in the recording direction to perform recording again, the state of FIG. Direct overwrite is impossible.

Further, when a signal is recorded on this magneto-optical recording medium by, for example, a magnetic field modulation method, when a signal is recorded on a magnetic film having a larger coercive force by applying a larger external magnetic field, the external magnetic field has a predetermined value. Since the coercive force always passes through the value of the recording magnetic field for the magnetic film having a smaller coercive force until reaching the value, a recording portion with a smaller external magnetic field is always formed around the recording portion with a larger external magnetic field. For this reason, not only a high S / N reproduced signal cannot be obtained, but if the signal is recorded at a high density, it is a recorded portion by a larger external magnetic field or a recorded portion by an originally smaller external magnetic field. However, there is also a problem that it becomes difficult to discriminate and the recording density cannot be increased. Such inconvenience also occurs when a signal is recorded by the light modulation method.

The present invention has been made in order to solve the deficiency of the prior art, and its object is to allow a recording state corresponding to each value in multilevel recording to exist stably against an external magnetic field. Magneto-optical recording capable of direct overwriting of multilevel recording, capable of recording and erasing signals with a small external magnetic field and a small output laser, and realizing signal recording with high S / N and high recording density. A magnetic head of a recording / reproducing apparatus suitable for providing a medium, for providing a multilevel recording system of signals using the magneto-optical recording medium, and further for multilevel recording of signals on the magneto-optical recording medium. To provide.

[0011]

In order to solve the above-mentioned problems, the present invention provides a magneto-optical recording medium having a plurality of magnetic layers which are laminated directly or via non-magnetic layers.
When the temperatures of the plurality of magnetic layers and the external magnetic field applied to the magnetic layer are changed, the plurality of magnetic layers are formed in at least three or more different magnetic field regions according to the change of the applied external magnetic field in a high temperature state. Has a region where the total magnetization of the magnetic layers becomes a single stable magnetization state, and in the low temperature state, the external magnetic field is zero, and at least in accordance with the magnitude of the external magnetic field applied at high temperature. A structure having a magnetization characteristic in which three or more magnetization states exist stably is adopted.

Specifically, first, at least two or more magnetic layers laminated on each other are laminated on a substrate, and at least one magnetic layer of each of these magnetic layers is exposed to an applied external magnetic field. On the other hand, it is formed of a magneto-optical recording film having a recording state in two or more different magnetic field regions, and the other magnetic layer is the above-mentioned 1
The magnetic layer is formed of a magneto-optical recording film having at least one recording state in a magnetic field region different from that of the magnetic layer.

Secondly, a plurality of magnetic layers each having one recording state in different magnetic field regions with respect to an applied external magnetic field are laminated and carried on a substrate.

Thirdly, at least one magnetic layer in which two or more recording states exist in different magnetic field regions with respect to the applied external magnetic field and the magnetic layer with respect to the applied external magnetic field. At least one magnetic layer having at least one recording state in different magnetic field regions is laminated on the substrate in a total of three layers or more.

Fourth, among the magnetic layers constituting the magneto-optical recording medium, at least one or more magnetic layers are irradiated with the reproducing laser beam on the incident side of the reproducing laser beam, the magnetic layers are concerned. An aperture portion smaller than the spot diameter of the reproducing laser beam is formed thermo-magnetically, and an aperture portion forming layer for realizing so-called super-resolution type recording magnetic domain reading is provided.

Fifth, among the magnetic layers constituting the magneto-optical recording medium, at least one or more magnetic layers are irradiated with the reproducing laser beam on the side of the reproducing laser beam incident side, the magnetic layer concerned. An aperture forming layer and a cutting layer for thermo-magnetically forming an aperture smaller than the spot diameter of the reproducing laser beam to realize so-called super-resolution recording magnetic domain reading are provided. did.

Of at least one of the magnetic layers in the first to fifth magneto-optical recording media, at least one magnetic layer includes a perpendicular magnetic film and an auxiliary magnetic film magnetically coupled to the perpendicular magnetic film. Can consist of: As the perpendicularly magnetized film, all known perpendicularly magnetized films can be used, but an amorphous alloy of a rare earth and a transition metal is particularly preferable because of its large magneto-optical effect. As the auxiliary magnetic film, one having the same Curie temperature as the perpendicular magnetic film or a magnetic material having a higher Curie temperature than the perpendicular magnetic film can be used. In this case, the recording magnetic field region of the magnetic layer including the auxiliary magnetic film and the perpendicular magnetization film can be shifted to the high magnetic field region side or the low magnetic field region side with respect to the other magnetic layers. Further, as the auxiliary magnetic film, a film made of a magnetic material whose magnetization is more likely to rotate in the direction of the external magnetic field when irradiated with a laser beam for recording or erasing than that of the perpendicular magnetic film can be used. In this case, the recording state can be present in two or more different magnetic field regions with respect to the applied external magnetic field in the magnetic layer composed of the auxiliary magnetic film and the perpendicular magnetization film. As the auxiliary magnetic film, a magnetic thin film having a film thickness of about 1 to 30Å,
Alternatively, it is preferable that a metal thin film having a film thickness of about 1 to 30 Å is laminated in multiple layers.

Regarding the pre-formatting of the magneto-optical recording medium, the data recording area is divided into a plurality of data recording units, and the head portion of each data recording unit is included in the multilevel recording signal recorded in the data recording unit. A configuration in which a test area for setting a slice level of each signal and / or a test area for generating a timing signal serving as a reference of timing for detecting an edge of a multi-valued recording signal recorded in the data recording unit are provided I chose Further, at the beginning of the data recording unit, together with the test area or separately from the test area, a tracking pit for performing tracking control of a recording or reproducing laser beam and a recording / reproducing of a multilevel recording signal are provided. The configuration is such that an embedded pit for drawing in the clock signal to be generated is provided. Further, a test area for detecting the optimum recording condition is provided outside the user area.

Regarding the recording / reproducing system of the magneto-optical recording medium, firstly, the optical head and the magnetic head are driven relatively to any one of the first to fifth magneto-optical recording mediums, and the optical While irradiating the laser beam along the recording track of the magneto-optical recording medium from the head, the laser beam irradiating section is supplied with an external magnetic field in which the magnetic field intensity is signal-modulated in multiple steps according to the recording signal from the magnetic head. A multi-valued signal is applied to the magneto-optical recording medium by applying the voltage. This is so-called magnetic field intensity modulation type signal recording. In this case, the laser beam may be emitted at a constant intensity, or may be emitted periodically or in a pulsed form.

Secondly, the optical head and the magnetic head are driven relative to any of the first to fifth magneto-optical recording media, and an external magnetic field is applied from the magnetic head to the magneto-optical recording medium. While being applied, a laser beam whose laser intensity is signal-modulated in multiple steps according to a recording signal is emitted from the optical head along a recording track of the magneto-optical recording medium, and a signal is transmitted to the magneto-optical recording medium. The value is recorded. This is so-called light intensity modulation type signal recording.
In this case, the external magnetic field is applied at a constant intensity,
It can also be varied at a constant frequency.

Third, the optical head and the magnetic head are driven relative to any one of the first to fifth magneto-optical recording media, and the magneto-optical recording medium is driven by the magnetic head to respond to a recording signal. While the external magnetic field whose applied magnetic field intensity is signal-modulated in multiple steps is applied, the laser intensity is signal-modulated in multiple steps along the recording track of the magneto-optical recording medium from the optical head according to the recording signal. A configuration is adopted in which a multi-valued signal is recorded on the magneto-optical recording medium by irradiating a laser beam. This is a so-called light-magnetic field intensity modulation type signal recording.

Fourth, the optical head and the magnetic head are driven relative to any one of the first to fifth magneto-optical recording media, and the magneto-optical information is generated by the laser beam emitted from the optical head. While repeatedly scanning the same track on the recording medium, the intensity, the modulation frequency, the pulse width of the laser beam emitted from the optical head and / or the intensity, the modulation frequency of the magnetic field applied from the magnetic head each time the scanning is repeated. The recording conditions such as the modulation amplitude range are switched in multiple steps to record signals on the same track in multiple levels. That is, this is a method in which a series of multilevel recording signals is divided into a plurality of signal groups having different recording conditions (combination of laser power and external magnetic field strength), and signal recording is repeated on the same track for each recording condition.

Fifth, as a recording / reproducing system of a magneto-optical recording medium in which a test area is provided at the head portion of each data recording unit, the test area is recorded when a multilevel recording signal is recorded in the data recording unit. And a test signal for setting the slice level of each signal included in the multi-valued recording signal, at least 1 for each signal included in the multi-valued recording signal.
When recording a multi-valued recording signal from the data recording unit, the test signal is read from the head portion of the data recording unit and slices corresponding to each signal included in the multi-valued recording signal are recorded. The level is set, and the read signal from the data recording unit is sliced at each of these slice levels to reproduce the multilevel recording signal.

Further, when recording a multi-valued recording signal in the data recording unit, a timing signal serving as a reference of timing for detecting an edge of the multi-valued recording signal is provided at a head portion of the data recording unit or at constant intervals. At least one test signal for generating is recorded for all edges between multilevel signal levels, and when reproducing a multilevel recording signal from the data recording unit, from the beginning of the data recording unit. The test signal is read to generate the reference timing of edge detection of each signal included in the multi-valued recording signal, and the edge of each signal included in the read signal from the data recording unit is detected at each of these reference timings. After detecting independently, synthesize each edge detection signal with reference to the reference timing of the edge detection,
The multi-valued recording signal is reproduced.

Further, when a multilevel recording signal is recorded in the data recording unit, the slice level of each signal included in the multilevel recording signal is set at the head portion of the data recording unit or at a constant interval. Of the test signal and a test signal for generating a timing signal serving as a timing reference for detecting an edge of the multilevel recording signal are recorded, and the multilevel signal is read based on the signals read from these test signals. The recorded signal can also be reproduced.

Sixth, as a recording / reproducing method for a magneto-optical recording medium having a test area provided outside the user area, a test area provided outside the user area after the magneto-optical recording medium is mounted in a recording / reproducing apparatus. The optical head and the magnetic head are positioned in the optical head, and the intensity and pulse width of the laser beam emitted from the optical head are changed stepwise or continuously, and included in the multilevel recording signal to be recorded on the magneto-optical recording medium. Write a fixed test pattern that is a combination of each signal, and then reproduce the test pattern,
The reproduction signal amplitude is compared with the reference signal amplitude, and the optimum recording condition of each signal included in the multilevel recording signal is obtained.

After mounting the magneto-optical recording medium on the recording / reproducing apparatus, the optical head and the magnetic head are positioned in a test area provided outside the user area, and the external magnetic field strength applied from the magnetic head is gradually or While continuously changing, a constant test pattern that is a combination of signals included in the multilevel recording signal to be recorded on the magneto-optical recording medium is written, and thereafter, the test pattern is reproduced to reproduce a reproduced signal amplitude. Is compared with the reference signal amplitude, and the optimum recording condition of each signal included in the multi-valued recording signal is obtained.

Seventh, in a magneto-optical recording medium for multilevel recording,
The optical head for irradiating a laser beam along the recording track and the laser beam irradiating portion of the magnetic layer for recording a recording signal having a value more than the number of magnetic field regions in a stable recording state of the magneto-optical recording medium. A laser beam or an external magnetic field that has been multi-valued modulated by a first signal train out of a plurality of signal trains obtained by dividing a multi-valued recording signal by relatively driving a magnetic head that applies an external magnetic field. After writing the first signal train to one recording track by using the above, a second write signal train having a narrower width than the first write signal train is provided on the first write signal train. The process of overwriting using a laser beam or an external magnetic field that is multi-valued signal modulated in the second signal train is repeated for all the divided signal trains.

Specifically, a 4-level recording signal is divided into two signal trains, and a laser beam having a constant intensity is emitted from the optical head along one recording track while the first signal train is used. An external magnetic field, which is signal-modulated in the form of four-valued pulse, is applied to the laser beam irradiation unit to write the first signal train on one recording track, and then to the center of the first write signal train. While irradiating the second write signal train having a width narrower than that of the first write signal train with a laser beam having a constant intensity from the optical head along the first recording track, It is possible to adopt a method of applying overwriting by applying an external magnetic field that is signal-modulated into a 4-valued pulse and recording 16-valued recording signals on the 1 recording track. In addition to the signal recording by the magnetic field modulation system, the same signal recording can be realized by the optical modulation system or the optical-magnetic modulation system. In reproducing the signal, the spot diameter is equal to or larger than the width of the first write signal sequence formed by writing the first signal sequence, or a reproduction laser beam having a diameter larger than this is recorded on the recording track. Can be carried out by irradiating along

A recording / reproducing apparatus for a magneto-optical recording medium is provided with a drive unit for the magneto-optical recording medium, and an optical head and a magnetic head mounted to the drive unit so as to face the magneto-optical recording medium. In the magnetic recording / reproducing apparatus, as the magnetic head, one magnetic circuit has two or more windings, and each winding is independently driven to apply a multistage external magnetic field to the magneto-optical recording medium. It is configured to include a magnetic head. In this case, it is possible to apply a constant bias magnetic field to the magneto-optical recording medium by using one of the two or more windings.

As another structure, in the same magneto-optical recording / reproducing apparatus as described above, as the magnetic heads, two or more magnetic heads that are driven independently of each other are arranged close to each other. In this case, it is possible to apply a constant bias magnetic field to the magneto-optical recording medium by any one of the two or more magnetic heads.

As still another configuration, in the same magneto-optical recording / reproducing apparatus as described above, a permanent magnet is arranged close to the magnetic head, and a constant bias magnetic field is applied to the magneto-optical recording medium by this permanent magnet. It is configured to be applied.

[0033]

A first magnetic layer having a recording state in two different magnetic field regions with respect to an applied external magnetic field, and a second magnetic layer having a recording state in a magnetic field region different from the first magnetic layer By using a magneto-optical recording medium in which the magnetic layers of (1) and (2) are laminated, four-level signal recording can be performed by applying four different external magnetic fields corresponding to each recording state of each magnetic layer. A first magnetic layer having a recording state in two different magnetic field regions with respect to an applied external magnetic field, and a second magnetic layer having two recording states in a magnetic field region different from the first magnetic layer. Even in the case of using a magneto-optical recording medium in which magnetic layers are stacked, four-value recording of signals becomes possible by applying four different external magnetic fields corresponding to each recording state of each magnetic layer.

That is, as shown in FIG. 144, for example, the first magnetic layer formed by laminating the perpendicular magnetization film and the predetermined auxiliary magnetic film has a carrier-to-noise ratio of an optical modulation recording signal to an external magnetic field of 2 It has two peaks (recording status). On the other hand, in the second magnetic layer having no auxiliary magnetic layer, as shown in FIG. 145, for example, the carrier-to-noise ratio of the optical modulation recording signal with respect to the external magnetic field has one peak. In addition, the inventors of the present application previously filed Japanese Patent Application No. 3-210430 and Japanese Patent Application No. 4-153.
As disclosed in Japanese Patent Laid-Open No. 5-182264, the first magnetic layer formed by stacking a perpendicular magnetization film and a predetermined auxiliary magnetic film is a perpendicular magnetization film by the action of the auxiliary magnetic layer. Since the sublattice magnetic moment of the transition metal therein is easily reversed in the exchange coupling magnetic field direction, the magnetization direction of the entire magnetic layer can be oriented in the external magnetic field direction or the opposite direction. On the other hand, the second magnetic layer, which does not have the auxiliary magnetic layer and has one recording state in the magnetic field region different from that of the first magnetic layer, can easily be oriented in the direction of the external magnetic field in the entire magnetic layer in the temperature rising state. The magnetization direction of is reversed.

Therefore, for example, as shown in FIG. 146 (a), the first magnetic layer made of a ferrimagnetic material in which the sublattice magnetic moment of the rare earth atom is more dominant than the sublattice magnetic moment of the transition metal atom from room temperature to the Curie temperature. A
And a second magnetic layer B made of a ferrimagnetic material in which the sublattice magnetic moment of the transition metal atom is more dominant than the sublattice magnetic moment of the rare earth atom from room temperature to the Curie temperature, and a downward external magnetic field is applied in the recording direction. When a signal is recorded by using the external magnetic field and the upward external magnetic field as the external magnetic field in the erasing direction, (i) the external magnetic field H _{0 of such a} magnitude that the entire magnetization direction of the first magnetic layer A can be oriented in the erasing direction (Fig. (External magnetic field in the region indicated by 144) in the erasing direction, the sublattice magnetic moment of the transition metal atoms of the first magnetic layer A is directed in the recording direction, and the sublattice magnetic moment of the transition metal atoms of the second magnetic layer B is applied. Can be turned to the erasing direction. (ii) By applying an external magnetic field H ₁ (external magnetic field in the region shown in FIG. 144) of a magnitude that can direct the entire magnetization of the first magnetic layer A in the recording direction in the erasing direction, Both the sublattice magnetic moments of the transition metal atoms of A and the second magnetic layer B can be directed in the erasing direction. (iii) By applying an external magnetic field H ₂ (external magnetic field in the region shown in FIG. 144) of a magnitude that can direct the entire magnetization of the first magnetic layer A in the erasing direction,
Both the sublattice magnetic moments of the transition metal atoms in the magnetic layer A and the second magnetic layer B can be directed in the recording direction. (iv) By applying an external magnetic field H ₃ (the external magnetic field in the region shown in FIG. 144) of a magnitude that can direct the entire magnetization of the first magnetic layer A to the recording direction, the first magnetic layer The sublattice magnetic moment of the transition metal atom of A can be directed to the erasing direction, and the sublattice magnetic moment of the transition metal atom of the second magnetic layer B can be directed to the recording direction.

The magnitude of the change in the Kerr rotation angle detected as a signal from the magneto-optical recording medium is proportional to the sum of the sublattice magnetic moments of the transition metal atoms in the first magnetic layer A and the second magnetic layer B. , H ₀ , H ₁ , H ₂ , H ₃ external magnetic fields are sequentially applied to the recording tracks, the relative signal output shown in FIG. 146 (b) is obtained. Therefore, for example, as shown in the figure, the recording state by the external magnetic field H ₁ is “0”, the recording state by the external magnetic field H ₀ is “1”, the recording state by the external magnetic field H ₃ is “2”, the external magnetic field H ₂ The four-valued recording of the signal can be performed by locating the recording state by "3" respectively.

Further, a first magnetic layer having a recording state in two different magnetic field regions with respect to an applied external magnetic field,
When a magneto-optical recording medium in which a second magnetic layer in which two recording states exist in a magnetic field different from that of the first magnetic layer is laminated is used, four-level signal recording is performed by the same principle. It can be carried out. For example, in the case where a first magnetic layer having the characteristic indicated by the alternate long and short dash line in FIG. 147 (b) and a second magnetic layer having the characteristic indicated by the broken line in FIG.
By applying the external magnetic fields of H ₀ , H ₁ , H ₂ and H ₃ shown in FIG.
Two recording states "0", "1", "2", "3" can be revealed. Therefore, for example, as shown in these figures, the recording state by the external magnetic field H ₀ is “0”, the external magnetic field H 0
_By positioning the recording state by 1 as “1”, the recording state by the external magnetic field H ₂ as “2”, and the recording state by the external magnetic field H ₃ as “3”, the signal of an external magnetic field of about ± 100 (Oe) can be obtained. 4-level recording is possible. In this case, as shown in FIG. 148, if a DC bias magnetic field is applied to the external magnetic field to shift the central magnetic field of the external magnetic field to the minus side by about −50 (Oe), it is as small as ± 50 (Oe). It also enables ternary recording of signals in an external magnetic field.

As described above, the magneto-optical recording medium of the present invention has 2
Since four-valued signals can be recorded in one magnetic layer, a higher-density signal recording can be achieved with a simpler structure than the conventional magneto-optical recording medium in which only two signals can be recorded in three values. it can. In addition, as is clear from FIGS. 144, 147, and 148, each recording state is extremely stable against fluctuations in the external magnetic field, and the magnetic characteristics of each magnetic layer, the laser beam intensity during recording and reproduction, and the external magnetic field intensity. Since it is not necessary to make a delicate matching, it is possible to construct a magneto-optical recording / reproducing system with excellent mass productivity and reliability.

The magnetic layer formed by contacting the perpendicularly magnetized film and the auxiliary magnetic film having a Curie temperature higher than or equal to that of the perpendicularly magnetized film is irradiated with a laser beam for recording or erasing, and thus the perpendicularly magnetized film is formed. When the magnetization of (1) is rotated by an external magnetic field, the direction of magnetization of the auxiliary magnetic layer maintains the initial state as shown in FIG. 149 (a), and an exchange coupling force acts on the perpendicular magnetic film. This exchange-coupling force is strong enough to reach several tens of KOe at room temperature when converted into a magnetic field, and this exchange-coupling magnetic field serves as a bias to be added to the external magnetic field at the time of recording or erasing with respect to the perpendicular magnetization film. Due to the bias magnetic field due to this exchange coupling, the transition region from the non-recorded state to the recorded state of the reproduction signal output with respect to the external magnetic field at the time of recording is changed in the magnetic layer including the perpendicular magnetic film and the auxiliary magnetic film as shown in FIG. 149 (b). As shown, the magnetic field shifts from near the zero magnetic field to the high magnetic field direction (recording direction) or the low magnetic field direction (erasing direction).

On the other hand, in the single-layered perpendicular magnetization film having no auxiliary magnetic film, the transition region from the non-recording state to the recording state of the reproduction signal output with respect to the external magnetic field at the time of recording is shown in FIG. 149 (c).
As shown in, near the zero magnetic field. Therefore, the magnetic layer (hereinafter, referred to as the first magnetic layer) including the perpendicular magnetic film having the auxiliary magnetic film is formed.
Magnetic layer) and a magnetic layer (hereinafter referred to as a second magnetic layer) formed of a single layer of perpendicularly magnetized film having no auxiliary magnetic film, a magnetic field region in which the external magnetic field strength in the recorded state does not overlap. Exists.

In a magneto-optical recording medium in which these magnetic layers are laminated in two layers, the change of the recording signal with respect to the external magnetic field is as shown in FIG.
As shown in FIG. 49 (d), there are three distinct stages, and an external recording region capable of stable recording is provided between the transition regions of each magnetic layer. Therefore, as shown in the same figure, the recording state by the external magnetic field strength H ₀ below the transition region of the first magnetic layer is “0”, and the transition region above the transition region of the first magnetic layer is above the transition region of the second magnetic layer. By arranging the recording state by the following external magnetic field strength H ₁ at “1” and the recording state by the external magnetic field H ₂ above the transition region of the second magnetic layer at “2”, three-valued signal recording can be performed.

As is apparent from FIG. 149 (d), in this magneto-optical recording medium, each recording state is extremely stable against fluctuations in the external magnetic field, and the magnetic characteristics of each magnetic layer and the laser beam during recording / reproduction. Since it is not necessary to delicately match the strength and the external magnetic field strength, it is possible to construct a magneto-optical recording / reproducing system having excellent mass productivity and reliability.

If the magnetic layers are laminated in two or more layers, it is possible to perform higher-order multi-value recording according to the number of laminated magnetic layers. Further, as a magneto-optical recording medium, a magneto-optical recording in which three or more magnetic layers are laminated, and at least one of the magnetic layers has a recording state in two or more different magnetic field regions with respect to an applied external magnetic field. If a film made of a film is used, multilevel recording of five or more values becomes possible by making the external magnetic field strength correspond to the recording state of each magnetic layer.

The operation of the recording / reproducing system for recording a multi-valued recording signal on the magneto-optical recording medium for multi-valued recording, which is more than the number of magnetic field regions in the stable recording state of the magneto-optical recording medium, will be described below. .

The multilevel signal recorded on the magneto-optical recording medium is
It can be divided into a plurality of signal sequences by an appropriate method. For example, (003122001203213331
The four-valued recording signal of (130230113203210) is divided into two from the beginning to obtain (00)
(31) (22) (00) (12) (03) (21)
(33) (11) (30) (23) (01) (13)
(20) (32) (10) can be converted into a signal sequence, and by further taking out the first signal and the second signal of each set separately, (032010231320)
1231) and the first signal sequence (01202313
10313020) and the second signal sequence.

The recording of the first signal train on the magneto-optical recording medium for four-value recording can be performed by the method described above. In addition, the overwriting of the second signal train on the first signal train written in the magneto-optical recording medium is performed under the condition that the magnetization of the first write signal train can be reversed and the laser intensity and / or
Alternatively, it is possible by setting the external magnetic field strength. Furthermore, when the second signal train is overwritten on the first write signal train, the width of the second signal train is made smaller than the width of the first write signal train (width of the magnetization domain). It is also possible to rewrite a part of the 1 write signal train to the 2nd signal train by adjusting the size of the laser spot. In addition, it is possible to easily synchronize the head of the first write signal string with the head of the second write signal string by using the conventional technique. Therefore, by operating the recording laser beam a plurality of times on the same track, it is possible to record a plurality of divided signal trains on the same track with different widths.

As described above, when the first signal train and the second signal train having different widths are overwritten on the same track in synchronization in the track direction, the signals of the first and second signal trains become Both are in the region of "3", the region of the first signal sequence is "3" and the signal of the second signal sequence is "2", and the signal of the first signal sequence is "3" and the second A region where the signal of the signal sequence is "1", a region where the signal of the first signal sequence is "3" and a signal of the second signal sequence is "0", and a signal of the first signal sequence is "2" , The signal of the second signal sequence is "3", the signal of the first signal sequence is "2", the signal of the second signal sequence is "2", the signal of the first signal sequence Is "2" and the signal of the second signal sequence is "1", the region of the signal of the first signal sequence is "2" and the signal of the second signal sequence is "0", The signal in the signal train is “1” and the signal in the second signal train is 3 "and the region of signal of the first signal string is""signal of the second signal sequence at the" 1 and region 2 ",
A region where the signal of the first signal sequence is "1" and the signal of the second signal sequence is "1", and the signal of the first signal sequence is "1" and the signal of the second signal sequence is "0" Region, the signal of the first signal sequence is “0” and the signal of the second signal sequence is “3”, and the signal of the first signal sequence is “0” and the signal of the second signal sequence Is "2", the signal of the first signal train is "0", the signal of the second signal train is "1", and the signals of the first and second signal trains are both "0". When the reproducing laser spots having the same width as or larger than the width of the first write signal train are irradiated, the total magnetization state of the regions irradiated with the reproducing laser spots is different from that of A 16-value recording signal can be detected. If the recording signal is divided into three signal trains and these three signal trains are overwritten on the same track, 64-value signal recording can be performed by the same principle.

Therefore, by using the magneto-optical recording medium for multi-valued recording according to the present invention, it is possible to realize more sophisticated multi-valued recording of signals, and to provide a magneto-optical recording medium that is inexpensive and has a large amount of recorded information.

The four-valued recording signal can be converted from the two-valued recording signal by, for example, the following method. That is, a binary recording signal (0000110110100000011000)
1110011111010111001011000
10111100011100100) is divided into two from the beginning, so that (00) (00) (11)
(01) (10) (10) (00) (00) (01)
(10) (00) (11) (10) (01) (11)
(11) (01) (01) (11) (00) (10)
(11) (00) (01) (01) (11) (10)
It is converted into a signal sequence of (00) (11) (10) (01) (00). Then, add the signal "0" to the (00) pair,
The signal “1” is assigned to the group (01), the signal “2” is assigned to the group (10), and the signal “3” is assigned to the group (11).
It is possible to obtain a four-valued recording signal 331130230113203210).

[0050]

EXAMPLES First, a typical example of a magneto-optical recording medium for multilevel recording according to the present invention will be described with reference to FIGS.

As shown in FIGS. 3 to 8, the magneto-optical recording medium for multi-value recording according to the present invention has a plurality of mutually different coercive forces like the known magneto-optical recording medium for multi-value recording. When the temperature acting on the recording layer (magnetic layer) and the external magnetic field are changed instead of laminating the magnetic layers described above, at least three or more magnetic fields are applied in a high temperature state according to the change of the applied external magnetic field. There are areas where the total magnetization is stable in the recording state in different magnetic field areas, and in the low temperature state, the external magnetic field is zero, and at least 3 or more depending on the magnitude of the external magnetic field applied at the high temperature. It is characterized in that the recording layer is formed by a plurality of magnetic layers having a magnetization characteristic that the magnetization state exists stably or a combination of these and a non-magnetic layer. In other words, as is apparent from these figures, in the high temperature state, the recording layer is formed by a plurality of magnetic layers in which the hysteresis loop is divided into three or more regions or a combination of these and the nonmagnetic layer. It can be said that they did.

The magneto-optical recording medium of FIG. 3 has a SiN film and an RE (rare earth) -rich Tb from the transparent substrate side (not shown).
FeCo film, SiN film, RE-rich TbFeCo
The film and the PtCo film are sequentially stacked. Here, the lower TbFeCo film is the first magnetic layer, and the upper TbFeCo film.
The film is the second magnetic layer, and the PtCo film is the auxiliary magnetic layer of the second magnetic layer. The magneto-optical recording medium of this example has a high temperature (170
(.Degree. C.) and the low temperature state (25.degree. C.), the hysteresis loop has the shape shown in the center of the figure, and the magnetization characteristic has the shape shown on the right side of the figure. Therefore, H ₀ , H ₁ , H ₂ ,
Recording states “0”, “1”, “2”, “3” for H _{3 respectively}
By allocating, it becomes possible to record the signal in four levels.

The magneto-optical recording medium of FIG. 4 has a SiN film, a RE-rich TbFeCo film, a PtCo film, and a TM (transition metal) -rich GdFe from the transparent substrate side (not shown).
A Co film and a SiN film are sequentially stacked. here,
The TbFeCo film is a first magnetic layer, the GdFeCo film is a second magnetic layer, and the PtCo film is an auxiliary magnetic layer of the first magnetic layer and the second magnetic layer. The magneto-optical recording medium of this example has a high temperature (15
The hysteresis loop at 0 ° C.) and the low temperature state (25 ° C.) has the shape shown in the center of the figure, and the magnetization characteristic has the shape shown on the right side of the figure. Therefore, H ₀ , H ₁ , H
_2, H ₃ of each of the recording state "0", "1", "2",
By assigning "3", 4-level recording of the signal becomes possible.

The magneto-optical recording medium of FIG. 5 includes a SiN film, a RE-rich TbFeCo film, a TM-rich GdTbFeCo film, and a SiN film from the transparent substrate side (not shown).
An Al film is sequentially laminated. Where TbFeCo
The film is the first magnetic layer, and the GdTbFeCo film is the second magnetic layer. In the magneto-optical recording medium of this example, the hysteresis loop in the high temperature state (180 ° C.) and the low temperature state (25 ° C.) has the shape shown in the center of the figure, and the magnetization characteristic has the shape shown in the right side of the figure. . Therefore, by assigning the recording states “0”, “1”, “2”, and “3” to H ₀ , H ₁ , H ₂ , and H ₃ , respectively, four-value recording of signals becomes possible.

The magneto-optical recording medium of FIG. 6 has a SiN film, a RE-rich TbFeCo film, a Co film, a SiN film, and a RE-rich TbFeCo from the transparent substrate side (not shown).
A film, a PtCo film, and a SiN film are sequentially stacked. Here, the lower TbFeCo film is the first magnetic layer, Co
The film is the auxiliary magnetic layer, the upper TbFeCo film is the second magnetic layer, and the PtCo film is the auxiliary magnetic layer. The magneto-optical recording medium of this example has a high temperature state (170 ° C.) and a low temperature state (25 ° C.).
The hysteresis loop at (.degree. C.) has the shape shown in the center of the figure, and the magnetization characteristic has the shape shown on the right side of the figure. Therefore, H _0, H _1, H _2, H _3, H recording state "0" to each of _4, "1", "2", "3", by assigning a "4", 5 value of the signal recording Will be possible.

The magneto-optical recording medium of FIG. 7 has a SiN film, a TM-rich TbFeCo film, a SiN film, a TM-rich TbFeCo film, and a RE from a transparent substrate side (not shown).
A rich GdFeCo film and a SiN film are sequentially stacked. Here, the lower TbFeCo film is the first magnetic layer,
The upper TbFeCo film is the second magnetic layer and the GdFeCo film is the auxiliary magnetic layer. In the magneto-optical recording medium of this example, the hysteresis loop in the high temperature state (160 ° C.) and the low temperature state (25 ° C.) has the shape shown in the center of the figure, and the magnetization characteristic has the shape shown in the right side of the figure. . Therefore, H ₀ ,
H _1, H ₂ of each to the recording state "0", by assigning "1", "2", allowing 3 value recording of the signal.

The magneto-optical recording medium of FIG. 8 has a SiN film, a RE-rich TbFeCo film, a TbFeCo-O film (oxidized TbFeCo film), and a T film from the transparent substrate side (not shown).
An M-rich TbFeCo film and a SiN film are sequentially stacked. Here, the lower TbFeCo film is the first magnetic layer, the upper TbFeCo film is the second magnetic layer, and oxidized TbFe.
The Co film is an auxiliary magnetic layer of these first and second magnetic layers. In the magneto-optical recording medium of this example, the hysteresis loop in the high temperature state (170 ° C.) and the low temperature state (25 ° C.) has the shape shown in the center of the figure, and the magnetization characteristic has the shape shown in the right side of the figure. . Therefore, by assigning the recording states “0”, “1”, “2”, and “3” to H ₀ , H ₁ , H ₂ , and H ₃ , respectively, four-value recording of signals becomes possible.

As shown in FIGS. 3 to 8, the magnetic layer material is most preferably an amorphous alloy of a rare earth and a transition metal. However, the magnetic layer material applicable to the present invention is not limited to this, and a garnet-based or ferrite-based oxide magnetic material, a noble metal such as Pt or Pd and a transition metal such as Fe or Co, and / or Tb. Alternate laminated bodies of rare earth metals such as Gd and Gd, Heusler alloys such as PtMnSb, and other materials such as MnBi, which have a large magneto-optical effect and can be thinned, can also be used. Further, when the magnetic layer on the side irradiated with laser light is a metal, it is necessary to make the magnetic layer sufficiently thin so that the light ray can be sufficiently transmitted, and it is 500 Å or less, more preferably 250 Å The following is desirable.

Next, the principle of multilevel recording of the magneto-optical recording medium according to the present invention will be described based on the hysteresis loop of FIG. FIG. 1A is a typical hysteresis loop of the magneto-optical recording medium according to the present invention at a low temperature (a temperature range from room temperature to irradiation of a reproducing laser beam), and FIG. It is a typical hysteresis loop in (temperature range at the time of rewriting information).

As shown in FIG. 1 (b), this magneto-optical recording medium is magnetized to four external magnetic field regions H ₀ ′, H ₁ ′, H ₂ ′ and H ₃ ′ at high temperatures. , M ₀ ′, M ₁
', M _2', takes one of the values of M ₃ '. On the other hand, at low temperature, the large hysteresis loop consists of one region. When the external magnetic field is applied from the magnetized state of M ₀ to reach the magnitude of H ₃ , the loop becomes the magnetized state of M ₃ when the external magnetic field is set to 0, and when the magnitude of H ₂ is reached. When the operation of returning the external magnetic field to 0, that is, the operation of drawing a small hysteresis loop, the magnetization state of M ₂ exists stably. Stage addition, after reaching by applying an external magnetic field in the negative direction from the magnetization state of M ₃ to the size of H _0, becomes a magnetization state of M ₀ if an external magnetic field is 0, it reaches the size of an H ₁ When the external magnetic field is returned to 0 at, the magnetization state of M ₁ exists stably. Thus, in the low temperature region, M ₀ , M ₁ and M are formed by the large hysteresis loop and the small hysteresis loop.
Four magnetized states of ₂ and M ₃ exist stably with no external magnetic field. Therefore, as shown in FIG. 2, H ₀ , H ₁ , H ₂ ,
Recording states “0”, “1”, “2”, “3” for H _{3 respectively}
By allocating, it becomes possible to record the signal in four levels.

Further, as is clear from FIG. 1 (b),
Whatever the magnetized state before recording a certain signal, the magneto-optical recording medium is heated to a high temperature state,
And when a predetermined external magnetic field required to obtain a stable magnetization state is applied, the magnetization of the recording layer is
After the temperature is lowered, the magnetized state corresponds to the magnitude of the applied external magnetic field. Therefore, the magneto-optical recording medium of the present invention can directly write new information on the previously recorded information without directly overwriting the information, that is, without erasing the previously recorded information.

Since the temperature at the time of rewriting information may be set to be equal to or higher than the temperature of the irradiating portion of the reproducing laser light, the definition of the hysteresis loop in the above high temperature region is based on the temperature of the irradiating portion of the reproducing laser light. It may be realized at any temperature up to the Curie temperature. Usually, the temperature of the reproducing laser beam irradiation part is 80 ° C. or higher.

Further, not only the magneto-optical recording medium having the film structure illustrated in FIGS. 3 to 8 but also the magneto-optical recording medium having a hysteresis loop at high temperature and low temperature as shown in FIG.
Multi-value recording of all signals is possible.

Each of the examples will be described below with reference to a configuration example of a magneto-optical recording medium for multilevel recording based on the above principle.

<First Structure Example> As shown in FIG. 9A,
The magneto-optical recording medium according to this example includes a transparent substrate 1 having a desired preformat pattern 2 formed on one surface thereof, a first dielectric layer 3 formed on the preformat pattern 2,
A first magnetic layer 4 formed on the first dielectric layer 3, and a second dielectric layer 5 formed on the first magnetic layer 4 as necessary,
The second magnetic layer 6 formed on the second dielectric layer 5 or the first magnetic layer 4, the third dielectric layer 7 formed on the second magnetic layer 6 as necessary, and the second magnetic layer. 6 or the third dielectric layer 7 and a reflective layer 8 formed as necessary, and a protective layer 9 formed on the reflective layer 8.

As the transparent substrate 1, for example, a transparent resin material such as polycarbonate, polymethylmethacrylate, polymethylpentene, or epoxy molded in a desired shape, or a desired shape on one side of a glass plate formed in the desired shape is used. It is possible to use any known transparent substrate such as one in which a transparent resin layer onto which the preformat pattern 2 is transferred is adhered. Note that the configuration, arrangement, forming method, and the like of the preformat pattern 2 are matters that are publicly known and are not the gist of this configuration example, and thus description thereof will be omitted.

The first to third dielectric layers 3, 5 and 7 are provided to cause multiple interference of the reproducing light beam in the film and increase the apparent Kerr rotation angle. It is formed of an inorganic dielectric material having a refractive index larger than that of the transparent substrate 1. Dielectric layer materials include silicon, aluminum,
Zirconium, titanium, tantalum oxides or nitrides are particularly suitable. The first dielectric layer 3 has a thickness of 600Å to 1200.
It is formed to a film thickness of Å. The second and third dielectric layers 5 and 7 are formed as required, and
It may be formed to have an arbitrary film thickness of 0 Å or less, and may be omitted in some cases.

The reflective layer 8 is provided for increasing the effective Kerr rotation angle of the medium by increasing the reflectance and for adjusting the recording sensitivity of the medium by adjusting the thermal conductivity. It is formed of a material having a high reflectance for the light beam. Specifically, [Al, Ag, Au,
[Cr, Ti, Ta, Sn, Si, Rb, P] and one or more metal elements selected from the group of Cu, Be]
e, Nb, Mo, Li, Mg, W, Zr], an alloy composed of one or more metal elements selected from the group of [e, Nb, Mo, Li, Mg, W, Zr] is particularly preferable.
It is formed to a film thickness of 00Å.

The protective layer 9 is for protecting the film bodies 3 to 8 from mechanical impact and chemical adverse effects, and is applied to cover the entire film body. The protective layer material may be a resin material. In particular, an ultraviolet curable resin is suitable because it is easy to form a film.

The first magnetic layer 4 is composed of an amorphous perpendicular magnetization film having a film thickness of 20 to 500 Å which is made of a rare earth-transition metal type amorphous alloy. As the composition, those represented by the following general formula are particularly preferable.

General formula; (Tb _100-A Q _A ) _X Fe _100-XYZ Co _Y M _Z However, 15 atomic% ≦ X ≦ 35 atomic% 5 atomic% ≦ Y ≦ 15 atomic% 0 atomic% ≦ Z ≦ 10 Atomic% 0 atomic% ≦ A ≦ 20 atomic% Tb is a rare earth element terbium, Fe is a transition metal iron, Co is a transition metal cobalt, M is Nb, C
At least one element selected from r, Pt, Ti and Al, and Q is at least one element selected from Gd, Nd and Dy (1).

In the rare earth-transition metal type amorphous alloy having this composition, as shown in FIG. 9B, the transition region between the recording state and the non-recording state in the change of the relative signal output with respect to the external magnetic field is almost the same. It is near zero magnetic field.

The second magnetic layer 6 is made of a rare earth-transition metal type amorphous alloy and has an amorphous perpendicular magnetization film 6a having a film thickness of 50 to 500 Å and a film thickness of 1 to 1 provided in contact therewith. 100
The auxiliary magnetic film 6b of Å.

Amorphous perpendicular magnetization film 6 of rare earth-transition metal system
As a, those represented by the same general formula as the first magnetic layer 4 can be used. In particular, the first magnetic layer 4 and the second magnetic layer
If the amorphous perpendicular magnetization film 6a of the magnetic layer 6 has the same composition, the film formation of these films becomes extremely easy, and the manufacturing cost of the magneto-optical recording medium can be made low.

A specific example of the auxiliary magnetic film 6b is a rare earth-transition metal-based amorphous perpendicular magnetization film or, for example, G.
dFeCo alloy, GdTbFeCo alloy, GdDyFe
Rare earth-transition metal alloys containing Gd and Nd such as Co alloy and NdFeCo alloy, oxygen and nitrogen in a larger amount than usual (for example, 5 atom% or more)
A rare earth-transition metal alloy containing, at least one element selected from the group of noble metal elements such as [Pt, Al, Ag, Au, Cu, Rh];
An alloy thin film with at least one element selected from a group of transition metal elements such as [Fe, Co, Ni], a transition metal simple substance such as [Fe, Co, Ni], or an alloy containing a large amount of these elements is used. Examples include a film having a thickness of -30 Å and several atomic layers.

Depending on the composition, these auxiliary magnetic films 6b are laminated in contact with the amorphous perpendicular magnetization film 6a.
Exchange coupling force on the transition metal magnetic moment of. Therefore, in the second magnetic layer 6 formed by stacking the amorphous perpendicular magnetization film 6a and the auxiliary magnetic film 6b, the change in the relative output of the recording signal with respect to the external magnetic field is recorded as shown in FIG. 9C. The transition region between the state and the non-recorded state shifts from near the zero magnetic field toward the recording magnetic field or the erasing magnetic field.

The perpendicular magnetization film 6a and the auxiliary magnetic film 6b formed by the amorphous perpendicular magnetization film of rare earth and transition metal are ferrimagnetic materials in which the magnetic moment of rare earth and the magnetic moment of transition metal are arranged antiparallel. . Of these, the composition in which the magnetic moment of the rare earth is predominant at room temperature is called the RE-rich composition, and the composition in which the magnetic moment of the transition metal is predominant is called the TM-rich composition, the magnetic moment of the transition metal of the auxiliary magnetic film 6b is Direction of the exchange coupling magnetic field emitted,
As a result, the shift direction of the transition region from the non-recorded state to the recorded state is determined depending on whether the auxiliary magnetic film 6b has the RE-rich composition or the TM-rich composition.

When the auxiliary magnetic film 6b has a RE-rich composition,
If the magnetization is aligned in the erasing direction during initialization, the auxiliary magnetic film 6
The transition metal magnetic moment of b is directed in the recording direction, and exerts an exchange coupling magnetic field that tends to be parallel to the transition metal magnetic moment of the perpendicular magnetization film 6a.

On the other hand, the perpendicular magnetization film 6a has the same R
In the case of the E-rich composition, the transition metal moment is also oriented in the recording direction at the time of erasing (initialization), and therefore the total of the perpendicular magnetization film 6a parallel to the transition metal magnetic moment of the auxiliary magnetic film 6b. In order to perform recording by reversing the magnetization of the magnetic recording medium, it is necessary to reverse the transition metal magnetic moment of the perpendicular magnetization film 6a to the exchange coupling magnetic field from the transition metal magnetic moment of the auxiliary magnetic film 6b. A strong external magnetic field is required. That is, in this case, the transition region with respect to the external magnetic field shifts in the recording magnetic field direction.

On the other hand, when the perpendicularly magnetized film 6a has a TM rich composition, the transition metal moment is also directed in the erasing direction when the magnetization is directed in the erasing direction, and therefore is antiparallel to the transition metal magnetic moment of the auxiliary magnetic film 6b. become. Magnetic moments are arranged between the two at a constant angle, and a region bridging the antiparallel magnetic moments, that is, an interface domain wall is generated, which is a higher energy state than the parallel state. When recording is performed, the magnetization of the perpendicular magnetization film 6a is reversed, and accordingly, the transition metal magnetic moment of the perpendicular magnetization film 6a is also reversed and becomes parallel to the transition metal magnetic moment of the auxiliary magnetic film 6b. Acts to assist this, in which case the transition region for an external magnetic field shifts in the direction of the erase field.

Similarly, when the auxiliary magnetic film 6b has a TM-rich composition and the perpendicular magnetic film 6a has a RE-rich composition,
The transition region shifts in the erase field direction. Further, the auxiliary magnetic film 6b has a TM-rich composition and the perpendicular magnetization film 6a has a TM-rich composition.
When the composition is rich, the transition region shifts in the recording magnetic field direction.

The shift amount of the transition region is determined by the auxiliary magnetic film 6
It can be adjusted by changing the composition and film thickness of b. Therefore, various magneto-optical recording media having different magnetic field regions in the recording state are produced by appropriately combining various auxiliary magnetic films 6b having different shift directions and shift amounts of transition regions and various perpendicular magnetic films 6a having different compositions. it can. 10A to 10H, the perpendicular magnetization film 6a and the auxiliary magnetic film 6 are shown.
Various magneto-optical recording media having different combinations with b and magnetic field regions in a recorded state are shown.

The laminated positions of the first magnetic layer 4 and the second magnetic layer 6 may be interchanged with each other. Each magnetic layer 4, 6
When the stacking positions of are changed, the Kerr rotation angle in each recording state corresponding to the magnitude of the external magnetic field during recording and the magnitude of the laser power applied changes, but multi-level signal recording is possible. The characteristics and effects of the magneto-optical recording medium do not change at all. Further, by stacking the magnetic layers in multiple layers of three or more layers, higher-order multilevel recording can be performed, and the composition of each film can be appropriately changed accordingly.

Hereinafter, more specific examples of the magneto-optical recording medium of this example will be described.

<First Embodiment> As shown in FIG. 11, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 100 nm are formed on the pre-format pattern forming surface 2 of the transparent substrate 1. A 10 nm Tb ₂₂ Fe ₆₆ Co ₁₂ (subscript indicates atomic%; the same applies hereinafter) film and a 10 nm thick SiN film
A film, a Tb ₂₂ Fe ₇₀ Co ₈ film with a film thickness of 10 nm, a Gd ₂₃ Fe ₆₂ Co ₁₅ film with a film thickness of 20 nm, and a film thickness of 10 nm
SiN film and an Al film having a film thickness of 50 nm are sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film having a film thickness of 100 nm constitutes the first dielectric layer 3, and the two SiN films having a film thickness of 10 nm constitute the second and third dielectric layers 5 and 7, respectively. Tb ₂₂ F
The e ₆₆ Co ₁₂ film constitutes the first magnetic layer 4 with a single layer,
There is one recording state in a specific magnetic field area. A Tb ₂₂ Fe ₇₀ Co ₈ film and a Gd ₂₃ Fe ₆₂ Co film, which are directly laminated on each other.
_{The 15} film constitutes the second magnetic layer 6, and is composed of Gd ₂₃ Fe ₆₂ C
The o ₁₅ film is an auxiliary magnetic film of a Tb ₂₂ Fe ₇₀ Co ₈ film which is a perpendicular magnetization film. The Curie temperature of the Tb ₂₂ Fe ₇₀ Co ₈ film is 180 ° C., and the Curie temperature of the Gd ₂₃ Fe ₆₂ Co ₁₅ film is 320 ° C. In this way, the Curie temperature of the auxiliary magnetic film is set to be at least equal to or higher than that of the perpendicular magnetic film so as to exert an exchange coupling force on the perpendicular magnetic film during recording. The second magnetic layer 6 has one recording state in a magnetic field region different from that of the first magnetic layer 4. Further, the Al film constitutes the reflective layer 8 and the ultraviolet curable resin film constitutes the protective layer 9.

In the magneto-optical recording medium of this example, the Tb ₂₂ Fe ₆₆ Co ₁₂ film forming the first magnetic layer 4, the Tb ₂₂ Fe ₇₀ Co ₈ film forming the second magnetic layer 6, and the Gd ₂₃ Fe ₆₂ Co film were formed. Each of the ₁₅ films has a TM-rich composition, as shown in FIG.
The change of the recording signal with respect to the external magnetic field corresponding to (h) is shown. The magneto-optical recording medium of the present example has an advantage that a large signal amplitude can be obtained, as is apparent from FIG.

<Second Embodiment> As shown in FIG.
The magneto-optical recording medium of the example is a pre-formatted substrate of the transparent substrate 1.
A SiN film having a thickness of 100 nm on the printed pattern forming surface 2.
And Tb with a film thickness of 10 nm_{twenty two}Fe₆₆Co₁₂The film and the film thickness
10 nm SiN film and 15 nm thick Gd _{twenty three}Fe₆₂
Co_FifteenFilm and Tb with a film thickness of 15 nm_{twenty two}Fe₇₀Co₈film
And a SiN film with a film thickness of 10 nm and A with a film thickness of 50 nm
1 film is sequentially laminated, and each of these films is formed by an ultraviolet curable resin.
Covered with a membrane.

The SiN film having a thickness of 100 nm constitutes the first dielectric layer 3, and the two SiN films having a thickness of 10 nm constitute the second and third dielectric layers 5 and 7, respectively. Tb ₂₂ F
The e ₆₆ Co ₁₂ film constitutes the first magnetic layer 4 with a single layer,
There is one recording state in a specific magnetic field area. Gd ₂₃ Fe ₆₂ Co ₁₅ film and Tb ₂₂ Fe ₇₀ Co layered directly on each other
_{The eight} films form the second magnetic layer 6, and one recording state exists in a magnetic field region different from that of the first magnetic layer 4. Further, the Al film constitutes the reflective layer 8 and the ultraviolet curable resin film constitutes the protective layer 9.

In the magneto-optical recording medium of this embodiment, the Gd ₂₃ Fe ₆₂ Co ₁₅ film as the auxiliary magnetic film is more laser beam than the Tb ₂₂ Fe ₇₀ Co ₈ film constituting the perpendicular magnetic film of the second magnetic layer 6. It is characterized in that it is arranged on the incident side of. Gd ₂₃ Fe ₆₂
The Co ₁₅ film has a larger Kerr rotation angle than the Tb ₂₂ Fe ₇₀ Co ₈ film. Therefore, in the magneto-optical recording medium including the auxiliary magnetic film and the perpendicularly magnetized film, the signal amplitude can be increased when the auxiliary magnetic film is arranged on the laser beam incident side.

<Third Embodiment> As shown in FIG. 13, the magneto-optical recording medium of this embodiment has a SiN film having a film thickness of 100 nm and a film thickness of 100 nm on the preformat pattern forming surface 2 of the transparent substrate 1. 9 nm Tb ₃₂ Fe ₅₆ Co ₁₂ film with a film thickness of 6
(Tb ₃₂ Fe ₅₆ Co ₁₂ ) ₉₂ —O ₈ film with a thickness of 1
0 nm SiN film and 10 nm thick Tb ₂₂ Fe ₇₀ C
o ₈ film, a Gd ₂₃ Fe ₆₂ Co ₁₅ film having a film thickness of 20 nm,
The structure is such that a SiN film having a film thickness of 10 nm and an Al film having a film thickness of 50 nm are sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film with a film thickness of 100 nm constitutes the first dielectric layer 3, and the two SiN films with a film thickness of 10 nm constitute the second and third dielectric layers 5 and 7, respectively. The Tb ₃₂ Fe ₅₆ Co ₁₂ film and the (Tb ₃₂ Fe ₅₆ C 12
o ₁₂ ) ₉₂ —O ₈ film constitutes the first recording layer 4,
There are two recording states in a particular magnetic field region. In addition, a Tb ₂₂ Fe ₇₀ Co ₈ film and a Gd ₂₃ Fe film, which are directly laminated on each other,
_{The 62} Co ₁₅ film constitutes the second recording layer 6, and one recording state exists in a magnetic field region different from that of the first recording layer 4. Further, the Al film constitutes the reflective layer 8 and the ultraviolet curable resin film constitutes the protective layer 9.

The transition region of the first recording layer 4 shifts to the erase side with respect to the zero magnetic field, and the transition region of the second recording layer 6 shifts to the recording side with respect to the zero magnetic field. Therefore, by stacking these recording layers 4 and 6 in two layers, the amplitude center of the modulation magnetic field during recording can be brought close to zero. In this example, as an auxiliary magnetic film of the first recording layer 4, (Tb ₃₂ Fe ₅₆ Co ₁₂ ) ₉₂ —O ₈ was used for the purpose of not reducing the incident amount of the laser beam on the second recording layer 6. A film was used and its thickness was set to 6 nm.

<Fourth Embodiment> As shown in FIG. 14, the magneto-optical recording medium of this embodiment has a SiN film having a thickness of 100 nm and a thickness of 100 nm on the preformat pattern forming surface 2 of the transparent substrate 1. 10 nm thick Tb ₃₂ Fe ₅₆ Co ₁₂ film, 1 nm thick Co film, 10 nm thick SiN film, 10 nm thick Tb ₂₂ Fe ₇₀ Co ₈ film, and 20 nm thick film
Gd ₂₃ Fe ₆₂ Co ₁₅ film, a SiN film having a film thickness of 10 nm, and an Al film having a film thickness of 50 nm are sequentially laminated, and each of these films is covered with an ultraviolet curable resin film. .

The SiN film having a film thickness of 100 nm constitutes the first dielectric layer 3, and the two SiN films having a film thickness of 10 nm constitute the second and third dielectric layers 5 and 7, respectively. The Tb ₃₂ Fe ₅₆ Co ₁₂ film and the Co film, which are directly laminated on each other, are
The recording layer 4 is formed, and two recording states exist in a specific magnetic field region. In addition, Tb ₂₂ F directly laminated on each other
The e ₇₀ Co ₈ film and the Gd ₂₃ Fe ₆₂ Co ₁₅ film form the second recording layer 6, and one recording state exists in a magnetic field region different from that of the first recording layer 4. Further, the Al film is the reflection layer 8
And the ultraviolet curable resin film constitutes the protective layer 9.

In the magneto-optical recording medium of the present embodiment, as in the magneto-optical recording medium of the third embodiment, the transition region of the first recording layer 4 shifts to the erase side with respect to the zero magnetic field, and the second recording layer 6 Since the transition region shifts to the recording side with respect to the zero magnetic field, the amplitude center of the modulation magnetic field at the time of recording can be brought close to zero.
In this example, an ultrathin film of Co was used as the auxiliary magnetic film of the first recording layer 4 for the purpose of not reducing the incident amount of the laser beam on the second recording layer 6. The film thickness can be adjusted in the range of 0.3 nm to 2 nm.

<Fifth Embodiment> As shown in FIG. 15, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 100 nm are formed on the preformat pattern forming surface 2 of the transparent substrate 1. 8 nm Tb ₃₂ Fe ₅₆ Co ₁₂ film with a film thickness of 7
nm SiN film and 35 nm thick Tb ₃₂ Fe ₅₆ Co
₁₂ films, a Pt ₈₀ Co ₂₀ film with a thickness of 50 nm, and a film thickness of 1
The structure is such that a 50 nm SiN film is sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film having a thickness of 100 nm constitutes the first dielectric layer 3, the SiN film having a thickness of 7 nm constitutes the second dielectric layer 5, and the SiN film having a thickness of 150 nm constitutes the third dielectric layer 7. are doing. The Tb ₃₂ Fe ₅₆ Co ₁₂ film having a film thickness of 8 nm constitutes the first recording layer 4, and one recording state exists in a specific magnetic field region. In addition, Tb ₃₂ Fe directly laminated on each other
_{The 56} Co ₁₂ film and the Pt ₈₀ Co ₂₀ film form the second recording layer 6, and two recording states exist in a magnetic field region different from that of the first recording layer 4. The ultraviolet curable resin film constitutes the protective layer 9.

Like the other auxiliary magnetic film materials listed in this specification, Pt ₈₀ Co ₂₀ is apt to rotate its magnetization in the direction of the external magnetic field when irradiated with a laser beam for recording or erasing. This property is due to the fact that a magnetic material whose Curie temperature is at least the same as or lower than the Curie temperature of the perpendicular magnetization film is selected as the auxiliary magnetic film material, or a magnetic thin film which becomes an in-plane magnetization film at least near room temperature is selected. It is exhibited by using it as an auxiliary magnetic film.

Pt ₈₀ Co ₂₀ of this example is a typical material having both of these properties. The Curie temperature of the perpendicular magnetization film Tb ₃₂ Fe ₅₆ Co ₁₂ is 210 ° C., and the Curie temperature of the auxiliary magnetic film Pt ₈₀ Co ₂₀ is 210 ° C.
At room temperature, it becomes an in-plane magnetized film. Since the Curie temperature of the auxiliary magnetic film may be lower than this, PtCo
As the composition of the alloy, a composition containing less Co than Pt ₈₀ Co ₂₀ can be used. The Curie temperature difference between the perpendicular magnetization film and the auxiliary magnetic film is preferably 0 to 170 ° C. The Curie temperature of the perpendicular magnetization film is 170 to
At 230 ° C, the effective Co content of the PtCo alloy is
It is 30 to 2 atomic%.

As the auxiliary magnetic film material having the same properties as the above PtCo alloy, Co, CoFe alloy, oxide T
bFeCo alloy, nitrided TbFeCo alloy, GdFeCo
Alloy, GdTbFeCo alloy, NdFeCo alloy, Gd
Examples thereof include DyFeCo alloy, CoZrNb alloy, PtCoRe alloy, PtCoRu alloy, HoCo alloy and the like.

An intermediate layer may be provided between the perpendicular magnetic film and the auxiliary magnetic film in order to control the magnetic coupling between them. The intermediate layer is composed of a material having lower perpendicular magnetic anisotropy energy and Curie temperature than the perpendicular magnetic film, and when the perpendicular magnetic film material is TbFeCo, Al, Ti, Cr, Nb, Ta, Gd is added to the material. , O, N and the like are particularly suitable for the material containing 20 atomic% or less.

The magneto-optical recording medium of this embodiment has a second recording layer.
As an auxiliary magnetic film that composes 6
Pt with high reflectance and excellent corrosion resistance₈₀Co₂₀The membrane
Using this, and stacking this into a thick film of 35 nm
Features. By doing this, the anti-reflection of the second recording layer 6 itself
Emissivity is increased, and Tb that constitutes the second recording layer 6₃₂Fe ₅₆
Co₁₂Permeation through the membrane₈₀Co₂₀Ray reaching the membrane
It is possible to contribute the Faraday rotation of the beam to the signal.
Therefore, the separate reflection layer 8 can be omitted, and the film
The laminated structure can be simplified.

<Sixth Embodiment> As shown in FIG. 16, the magneto-optical recording medium of the present embodiment has a SiN film having a film thickness of 100 nm and a film thickness of 100 nm on the preformat pattern forming surface 2 of the transparent substrate 1. 10 nm Tb ₂₂ Fe ₇₀ Co ₈ film, 5 nm thick Gd ₂₃ Fe ₆₂ Co ₁₅ film, and 10 nm thick S
An i film, a Tb ₃₂ Fe ₅₆ Co ₁₂ film having a film thickness of 35 nm, and a Pt ₈₀ Co ₂₀ film having a film thickness of 100 nm are sequentially laminated, and each of these films is covered with an ultraviolet curable resin film. ing.

The SiN film having a film thickness of 100 nm constitutes the first dielectric layer 3 and the Si film having a film thickness of 10 nm constitutes the second dielectric layer 5. The Tb ₂₂ Fe ₇₀ Co ₈ film and the Gd ₂₃ Fe ₆₂ Co ₁₅ film, which are directly laminated on each other, form the first recording layer 4, and one recording state exists in a specific magnetic field region. Further, the Tb ₃₂ Fe ₅₆ Co ₁₂ film and the Pt layered directly on each other
_{The 80} Co ₂₀ film constitutes the second recording layer 6, and two recording states exist in a magnetic field region different from that of the first recording layer 4. The ultraviolet curable resin film constitutes the protective layer 9.

In the magneto-optical recording medium of this example, a Pt ₈₀ Co ₂₀ film having a high reflectance with respect to the irradiation laser beam and an excellent corrosion resistance was used as the auxiliary magnetic film forming the second recording layer 6, and this was 100 nm. It is characterized by being laminated to a very thick film. By doing so, the second recording layer 6
Since the reflectance of the film itself is increased and the protective effect of each film disposed inside thereof is increased, both the third dielectric layer 7 and the reflective layer 8 can be omitted, and the laminated structure of the film can be further improved. Can be simple.

The auxiliary magnetic film of this embodiment is selected so that the perpendicular magnetic anisotropy energy is lower than that of the perpendicular magnetic film. In the case of the present embodiment, GdFeCo is a so-called in-plane magnetized film because the shape magnetic anisotropy is dominant over the perpendicular magnetic anisotropy at room temperature. However, when the laser beam for recording or erasing is irradiated and the temperature is raised, this state is reversed, and the perpendicular magnetic anisotropy becomes dominant to form a so-called perpendicular magnetization film. When a magnetic thin film having such properties is heated in the state where an external magnetic field is applied, the magnetization easily rotates in the direction of the external magnetic field, and at high temperatures, the exchange coupling force is surely applied in the vertical direction. Therefore, the effect of the auxiliary magnetic film of controlling the recording magnetic field region can be effectively exhibited.

<Second Configuration Example> As shown in FIG. 17A, the magneto-optical recording medium according to the present example has a transparent substrate 1 having a desired preformatted pattern 2 formed on one side, and a preformatted pattern 2. First dielectric layer 3 formed thereon
A first recording layer 11 formed on the first dielectric layer 3,
A second dielectric layer 5 formed on the first recording layer 11 as needed, a second recording layer 12 formed on the second dielectric layer 5 or the first recording layer 11, and a second recording layer. A third dielectric layer 7 that is formed on the second recording layer 12 as necessary, a third recording layer 13 that is formed on the second recording layer 12 or on the third dielectric layer 7, and a third recording layer 13.
Fourth dielectric layer 1 formed on recording layer 13 as required
4, a reflective layer 8 formed on the third recording layer 13 or the fourth dielectric layer 14 as needed, and a protective layer 9 formed on the reflective layer 8.

Transparent substrate 1, first to third dielectric layers 3,
The fifth and seventh layers, the reflective layer 8, and the protective layer 9 are the same as those in the first configuration example described above, and thus the description thereof will be omitted to avoid duplication.

The first recording layer 11 is composed of a rare earth-transition metal-based amorphous perpendicular magnetization film similar to the first recording layer 4 of the first configuration example. The film thickness is adjusted to 20 to 500Å. Therefore, this first recording layer 11 is formed as shown in FIG.
As shown in (b), the transition region from the non-recording state to the recording state in the change of the relative signal output with respect to the external magnetic field is near the zero magnetic field.

The second recording layer 12 has a film thickness of 50 to 500Å
The amorphous perpendicular magnetization film 12a and the auxiliary magnetic film 12b having a film thickness of 5 to 100Å provided in contact with the amorphous perpendicular magnetization film 12a. The amorphous perpendicular magnetic film 12a is composed of a rare earth-transition metal-based amorphous perpendicular magnetic film similar to the amorphous perpendicular magnetic film 6a of the first structural example, and the auxiliary magnetic film 12b is formed of the first structural example. The auxiliary magnetic film 6b has the same magnetic film. Therefore, as shown in FIG. 17B, in the second recording layer 12, the transition region from the non-recording state to the recording state in the change of the relative signal output with respect to the external magnetic field is from the vicinity of the zero magnetic field to the recording magnetic field direction or Shift in the erasing magnetic field direction.

The third recording layer 13 is an amorphous rare earth-transition metal system in which the rare earth sublattice magnetization moment is predominant in the temperature range from room temperature to the Curie temperature, or the temperature range from room temperature to the highest reached temperature during recording or erasing. 50-
The amorphous perpendicular magnetization film 13a having a thickness of 500 Å and the auxiliary magnetic film 13b having a film thickness of 5 to 100 Å provided in contact therewith.

Rare Earth-Transition Metal Amorphous Perpendicular Magnetization Film 1
As 3a, those represented by the following general formula are particularly preferable.

General formula; (Tb _100-A Q _A ) _X Fe _100-XYZ Co _Y M _Z However, 20 atomic% ≤ X ≤ 35 atomic% 5 atomic% ≤ Y ≤ 15 atomic% 0 atomic% ≤ Z ≤ 10 Atomic% 0 atomic% ≦ A ≦ 20 atomic% Tb is a rare earth element terbium, Fe is a transition metal iron, Co is a transition metal cobalt, M is Nb, C
At least one element selected from r, Pt, Ti and Al, Q is at least one element selected from Gd, Nd and Dy (2) The auxiliary magnetic film 13b is a transition metal. It is composed of a magnetic material containing an element and having a small perpendicular magnetic anisotropy. As a specific example, at least one element selected from the group of noble metal elements such as [Pt, Al, Ag, Au, Cu, Rh],
Alloy thin film with at least one element selected from the group of transition metal elements such as [Fe, Co, Ni], for example, GdFeCo alloy, GdTbFeCo alloy, G
Gd and N such as dDyFeCo alloy and NdFeCo alloy
Rare earth-transition metal alloys with reduced perpendicular magnetic anisotropy by containing d, oxygen and nitrogen in a larger amount than usual (for example, 5 atom% or more)
5-30 Å and several atomic layers containing rare earth-transition metal alloys having reduced perpendicular magnetic anisotropy, transition metal simple substances such as [Fe, Co, Ni], or alloys containing a large amount thereof. And the like, and the like, and the like.

Depending on the composition, the auxiliary magnetic film 4b has the perpendicular magnetic anisotropy energy equal to or lower than the shape anisotropy, so that the magnetization is in-plane (auxiliary) before an external magnetic field is applied. It can be oriented in a direction parallel to the film surface of the magnetic film 4b). The auxiliary magnetic film 4b thus adjusted is heated to a temperature near the Curie temperature, and when an external magnetic field is applied, the magnetization direction rises from the in-plane direction to generate a magnetic moment component in the external magnetic field direction. An exchange coupling force is exerted on the transition metal magnetic moment of the amorphous perpendicularly magnetized films 4a stacked in contact with each other. Therefore, in the first recording layer formed by stacking the amorphous perpendicular magnetization film 4a and the auxiliary magnetic film 4b, changes in the carrier wave and the noise level of the light modulation recording signal with respect to the external magnetic field are as shown in FIG. It has two peaks.

Like the first to third dielectric layers 3, 5, and 7, the fourth dielectric layer 14 causes multiple interference of the reproducing light beam in the film and increases the apparent Kerr rotation angle. It is provided for this purpose and is formed of an inorganic dielectric material having a refractive index larger than that of the transparent substrate 1. As the dielectric layer material, oxides or nitrides of silicon, aluminum, zirconium, titanium, tantalum are particularly suitable. This fourth dielectric layer is formed as necessary, and has a thickness of 0 to 5
It is formed to a film thickness of 00Å.

The stacking positions of the first recording layer 11, the second recording layer 12, and the third recording layer 13 may be interchanged with each other. When the stacking positions of the recording layers 11, 12, and 13 are changed, the Kerr rotation angle in each recording state corresponding to the magnitude of the external magnetic field at the time of recording and the magnitude of the laser power applied changes, but Multi-valued recording is possible, and there is no change in the characteristics and effects of the magneto-optical recording medium. Further, by stacking four or more recording layers, it is possible to perform higher-order multilevel recording, and the composition of each film can be appropriately changed accordingly.

Hereinafter, more specific examples of the magneto-optical recording medium of this example will be described. <Seventh Embodiment> As shown in FIG. 18, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 10 are formed on the preformat pattern forming surface 2 of the transparent substrate 1.
nm Tb ₂₂ Fe ₇₀ Co ₈ film and Si with a film thickness of 10 nm
N film, Tb ₂₂ Fe ₇₀ Co ₈ film with a film thickness of 10 nm, Gd ₂₃ Fe ₆₂ Co ₁₅ film with a film thickness of 5 nm, and film thickness of 10 nm
SiN film, a Tb ₃₂ Fe ₅₆ Co ₁₂ film with a film thickness of ₂₀ nm, a Pt ₈₀ Co ₂₀ film with a film thickness of 5 nm, and a film thickness of 10 nm
SiN film and an Al film having a film thickness of 50 nm are sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film with a film thickness of 100 nm constitutes the first dielectric layer 3, and the three SiN films with a film thickness of 10 nm constitute the second to fourth dielectric layers 5, 7, and 14, respectively. Tb
_{The 22} Fe ₇₀ Co ₈ film constitutes the first recording layer 11 with a single layer, and one recording state exists in a specific magnetic field region. Tb ₂₂ Fe ₇₀ Co ₈ film and Gd ₂₃ Fe laminated directly on each other
_{The 62} Co ₁₅ film constitutes the second recording layer 12, and one recording state exists in a magnetic field region different from that of the first recording layer 11. Further, the Tb ₃₂ Fe ₅₆ Co ₁₂ film and the Pt ₈₀ Co ₂₀ film, which are directly laminated on each other, form the third recording layer 13,
Two recording states exist in a magnetic field region different from those of the first recording layer 11 and the second recording layer 12. Further, the Al film constitutes the reflective layer 8 and the ultraviolet curable resin film constitutes the protective layer 9.

<Third Configuration Example> As shown in FIG. 19A, the magneto-optical recording medium according to the present example has a transparent substrate 1 having a desired preformatted pattern 2 formed on one surface and a preformatted pattern 2. First dielectric layer 3 formed thereon
A recording layer 21 formed on the first dielectric layer 3, a second dielectric layer 5 formed on the recording layer 21 as necessary,
The reflective layer 8 is formed on the second dielectric layer 5 or the recording layer 21 as needed, and the protective layer 9 is formed on the reflective layer 8.

The recording layer 21 is the third recording layer 1 of the second configuration example.
Similar to 3, the film made of a rare earth-transition metal-based amorphous alloy in which the rare earth sublattice magnetization moment is predominant in the temperature range from room temperature to the Curie temperature or from the room temperature to the maximum reached temperature during recording or erasing. The amorphous perpendicularly magnetized film 21a having a thickness of 100 to 500 Å and the film thickness provided in contact with the film are 5
˜100 Å auxiliary magnetic film 21b.
The preferable composition of the amorphous perpendicular magnetization film 21a and the preferable material of the auxiliary magnetic film 21b are the same as those in the second configuration example. The configuration of the other parts is the same as that of the second configuration example, and thus the description thereof is omitted. In this recording layer 21, changes in the carrier wave and noise level of the optical modulation recording signal with respect to the external magnetic field have two peaks as shown in FIG. 19 (b).

Hereinafter, more specific examples of the magneto-optical recording medium of this example will be described. <Eighth Embodiment> As shown in FIG. 20, the magneto-optical recording medium of the present embodiment has a SiN film having a film thickness of 100 nm and a film thickness of 30 on the preformat pattern forming surface 2 of the transparent substrate 1.
nm Tb ₃₂ Fe ₅₆ Co ₁₂ film and 20 nm thick Pt
₈₀ Co ₂₀ film, SiN film with a thickness of 10 nm, and a film thickness of 5
A 0 nm Al film is sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film having a film thickness of 100 nm constitutes the first dielectric layer 3, and the SiN film having a film thickness of 10 nm constitutes the second dielectric layer 5. The Tb ₃₂ Fe ₅₆ Co ₁₂ film and the Pt ₈₀ Co ₂₀ film, which are directly laminated on each other, form the recording layer 13, and two recording states exist in different magnetic field regions. The Al film constitutes the reflective layer 8 and the ultraviolet curable resin film constitutes the protective layer 9.

<Fourth Configuration Example> As shown in FIG. 21A, the magneto-optical recording medium according to the present example has a transparent substrate 1 having a desired preformat pattern 2 formed on one surface thereof, and a preformat pattern 2. First dielectric layer 3 formed thereon
A first recording layer 31 formed on the first dielectric layer 3,
A second dielectric layer 5 formed as necessary on the first recording layer 31, a second recording layer 32 formed on the second dielectric layer 5 or the first recording layer 31, and a second recording layer. A third dielectric layer 7 that is formed on 32 as necessary, and a reflective layer 8 that is formed on the third dielectric layer 7 or the second recording layer 32 as necessary,
The protective layer 9 is formed on the reflective layer 8.

Like the second recording layer 6 of the first configuration example, the first recording layer 31 is a rare earth-transition metal based perpendicular magnetization film 31a.
21B, the transition region from the non-recording state to the recording state in the change of the relative signal output with respect to the external magnetic field is zero. There is a shift from near the magnetic field toward the recording magnetic field or the erasing magnetic field.

The second recording layer 32 is similar to the third recording layer 13 of the second configuration example in that the rare earth sub-layer is in the temperature range from room temperature to the Curie temperature or from room temperature to the maximum reached temperature at the time of recording or erasing. An amorphous perpendicular magnetization film 21a having a film thickness of 100 to 500Å and made of a rare earth-transition metal amorphous alloy having a dominant lattice magnetization moment, and an auxiliary magnetic film having a film thickness of 5 to 100Å provided in contact therewith. And a film 21b. In this recording layer 32, changes in the carrier wave and the noise level of the light modulation recording signal with respect to the external magnetic field have two peaks as shown in FIG. The preferable composition of the amorphous perpendicular magnetization film 21a and the preferable material of the auxiliary magnetic film 21b are the same as those in the second configuration example. The configuration of the other parts is the same as that of the second configuration example, and thus the description thereof is omitted.

Hereinafter, more specific examples of the magneto-optical recording medium of this example will be illustrated. <Ninth Embodiment> As shown in FIG. 22, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 10 are formed on the preformat pattern forming surface 2 of the transparent substrate 1.
nm Tb ₂₂ Fe ₇₀ Co ₈ film and 5 nm thick Gd ₂₃
Fe ₄₇ Co ₃₀ film, SiN film with a film thickness of 10 nm, Tb ₃₂ Fe ₅₆ Co ₁₂ film with a film thickness of 10 nm, and film thickness of 20 nm
Pt ₈₀ Co ₂₀ film, a SiN film having a film thickness of 10 nm, and an Al film having a film thickness of 50 nm are sequentially laminated, and these films are covered with an ultraviolet curable resin film.

The SiN film having a film thickness of 100 nm is the first dielectric layer 3, and the two SiN films having a film thickness of 10 nm are the second and third dielectric layers 3.
Of the dielectric layers 5, 7. The Tb ₂₂ Fe ₇₀ Co ₈ film and the Gd ₂₃ Fe ₄₇ Co ₃₀ film that are directly laminated on each other are
The first recording layer 31 is configured and has a magnetic field region in a recorded state in a region shifted from the zero magnetic field. On the other hand, the Tb ₃₂ Fe ₅₆ Co ₁₂ film and the Pt ₈₀ Co ₂₀ film, which are directly laminated on each other,
The second recording layer 32 is formed, and two recording states exist in different magnetic field regions. The Al film constitutes the reflective layer 8 and the ultraviolet curable resin film constitutes the protective layer 9.

The magneto-optical recording medium of this example is different from the magneto-optical recording medium of the sixth example in that Co of the auxiliary magnetic film GdFeCo.
The content has been increased. When the auxiliary magnetic film having such a composition is used, the Curie temperature of the auxiliary magnetic film rises and
As a result, the exchange coupling force acting on the perpendicularly magnetized film increases, so that the shift amount of the magnetic field region in the recording state increases.

<Fifth Configuration Example> As shown in FIG. 23A, the magneto-optical recording medium according to the present example has a transparent substrate 1 having a desired preformatted pattern 2 formed on one side, and a preformatted pattern 2. First dielectric layer 3 formed thereon
A first recording layer 4 formed on the first dielectric layer 3 and a second dielectric layer 5 formed on the first recording layer 4 as necessary.
A second recording layer 6 formed on the second dielectric layer 5 or the first recording layer 4, a third dielectric layer 7 formed on the second recording layer 6 if necessary, and a third The reflective layer 8 is formed on the dielectric layer 7, and the protective layer 9 is formed on the reflective layer 8.

The first recording layer 4 is a rare earth-transition metal type amorphous material in which the rare earth sublattice magnetization moment is predominant in the temperature range from room temperature to the Curie temperature, or in the temperature range from room temperature to the maximum reached temperature during recording or erasing. 100-
The amorphous perpendicular magnetization film 4a having a thickness of 500 Å and the auxiliary magnetic film 4b having a film thickness of 5 to 100 Å provided in contact therewith. As the rare earth-transition metal-based amorphous perpendicular magnetization film, the film represented by the above general formula (2) is particularly preferable. The auxiliary magnetic film 4b is made of a magnetic material containing a transition metal element and having a small perpendicular magnetic anisotropy. Specifically, it is shown in the column of the second configuration example.
Can be used.

Depending on the composition, the auxiliary magnetic film 4b has the perpendicular magnetic anisotropy energy equal to or lower than the shape anisotropy, and the magnetization is in-plane (auxiliary) before an external magnetic field is applied. It can be oriented in a direction parallel to the film surface of the magnetic film 4b). The auxiliary magnetic film 4b thus adjusted is heated to a temperature near the Curie temperature, and when an external magnetic field is applied, the magnetization direction rises from the in-plane direction to generate a magnetic moment component in the external magnetic field direction. An exchange coupling force is exerted on the transition metal magnetic moment of the amorphous perpendicularly magnetized films 4a stacked in contact with each other. Therefore, in the first recording layer formed by stacking the amorphous perpendicular magnetization film 4a and the auxiliary magnetic film 4b, changes in the carrier wave and noise level of the optical modulation recording signal with respect to the external magnetic field are as shown in FIG. It has two peaks.

The second recording layer 6 is composed of a magneto-optical recording film having at least one recording state in a magnetic field region different from that of the first recording layer 4. Therefore, it is also possible to use an amorphous perpendicular magnetization film and an auxiliary magnetic film of the same kind as the first recording layer 4 and having two recording states in magnetic field regions different from those of the first recording layer 4. , The first
It is possible to use a recording layer having a different structure from that of the recording layer 4 and having one recording state in a magnetic field region different from that of the first recording layer 4, as shown in FIG. The second recording layer 6 belonging to the latter is composed of a rare earth-transition metal-based amorphous perpendicular magnetization film in which the transition metal sublattice magnetization is dominant in the temperature range from room temperature to the maximum reached temperature during recording and erasing. In the same temperature range as described above, a rare earth sublattice magnetization is predominant in a rare earth-transition metal amorphous perpendicular magnetization film, a rare earth-transition metal system in which a compensation temperature exists between room temperature and the Curie temperature. Examples thereof include an amorphous perpendicular magnetization film. Specifically, those represented by the following general formula are particularly preferable. The thickness of the second recording layer 6 is preferably formed in the range of 100 to 500Å.

General formula; Tb _X Fe _100-XYZ Co _Y M _Z However, 15 atomic% ≦ X ≦ 30 atomic% 5 atomic% ≦ Y ≦ 15 atomic% 0 atomic% ≦ Z ≦ 10 atomic% Tb is a rare earth element Terbium, Fe is a transition metal iron, Co is a transition metal cobalt, M is Nb, C
At least one element selected from r and Pt ...
・ (3).

The other structure is the same as each of the above-described structure examples, and therefore the description thereof is omitted to avoid duplication. The respective film bodies 3 to 8 are sequentially laminated on the preformat pattern forming surface of the transparent substrate 1 by a vacuum film forming method such as sputtering or vacuum evaporation. Each of these film bodies 3 to 8 has a difference in reproduction output level (size of Kerr rotation angle) depending on each recording level as much as possible when signals are read from the optical information recording medium in which multi-value recording is performed. The film thickness and the optical constant are selected so as to be uniform. Depending on the selection at that time, the second and third enhancement films and / or the reflection film may be omitted. Further, the first recording layer 4 and the second recording layer 6 may have their stacking positions interchanged with each other. When the stacking position of each recording layer is changed, the Kerr rotation angle in each recording state corresponding to the magnitude of the external magnetic field at the time of recording and the magnitude of the laser power applied changes, but It is possible, and there is no change in the characteristics and effects of the magneto-optical recording medium. In addition, by stacking the recording layers in a multilayer structure of three or more layers,
It is also possible to carry out higher-order multilevel recording, and to appropriately change the composition of each film accordingly.

Examples of the magneto-optical recording medium of this example will be described below.

<Tenth Embodiment> As shown in FIG. 24, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm is formed on the preformat pattern forming surface 2 of the transparent substrate 1.
Tb ₁₉ Fe ₆₂ Co ₁₀ Cr ₉ film having a thickness of 15 nm, SiN film having a thickness of 10 nm, and Tb ₃₂ Fe having a thickness of 20 nm
_{A 56} Co ₁₂ film, a Pt ₈₀ Co ₂₀ film with a thickness of 5 nm, a SiN film with a thickness of 10 nm, and an Al film with a thickness of 70 nm are sequentially laminated, and each of these films is an ultraviolet curable resin film. Covered with.

The SiN film having a film thickness of 100 nm constitutes the first dielectric layer 3, and the two SiN films having a film thickness of 10 nm constitute the second and third dielectric layers 5 and 7, respectively. Tb ₁₉ F
The e ₆₂ Co ₁₀ film constitutes the first recording layer 4 with a single layer,
There is one recording state in a specific magnetic field area. The Tb ₃₂ Fe ₅₆ Co ₁₂ film and the Pt ₈₀ Co ₂₀ film, which are directly laminated on each other, form the second recording layer 6, and two recording states exist in a magnetic field region different from that of the first recording layer 4. Furthermore, A
The l film constitutes the reflective film 8, and the ultraviolet curable resin film constitutes the protective film 9.

<Eleventh Embodiment> As shown in FIG.
The example magneto-optical recording medium is a pre-format of the transparent substrate 1.
On the pattern forming surface 2, a SiN film having a film thickness of 100 nm,
Tb with a film thickness of 15 nm ₃₂Fe₅₆Co₁₂Film and film thickness is 2n
Gd of m₁₈Fe₆₇Co_FifteenFilm and SiN with a thickness of 10 nm
Film and Tb with a film thickness of 20 nm₁₉Fe₆₂Co_TenCr₉film
And a SiN film with a film thickness of 10 nm and A with a film thickness of 70 nm
1 film is sequentially laminated, and each of these films is formed by an ultraviolet curable resin.
Covered with a membrane.

Tb ₃₂ Fe ₅₆ Co ₁₂ laminated directly on each other
The film and the Gd ₁₈ Fe ₆₇ Co ₁₅ film form the first recording layer 4, and two recording states exist in different magnetic field regions. T
The b ₁₉ Fe ₆₂ Co ₁₀ film constitutes the second recording layer 6 with a single layer, and one recording state exists in a magnetic field region different from that of the first recording layer 4. The magneto-optical recording medium of the present example is different from the magneto-optical recording medium of the first embodiment in that the first recording layer 4 provided on the side closer to the substrate, that is, the incident side of the recording / reproducing laser beam has two magnetic layers. It is characterized by being composed of a laminated body of films. Therefore, for the purpose of not reducing the incident amount of the laser beam on the second recording layer 6, the auxiliary magnetic film forming the first recording layer 4 has a low absorption rate of the laser beam G.
A dFeCo film was used and its thickness was made extremely thin to 2 nm. Since the other parts are the same as those in the first embodiment, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

<Twelfth Embodiment> As shown in FIG. 26, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm is formed on the preformat pattern forming surface 2 of the transparent substrate 1.
A Tb ₃₂ Fe ₅₆ Co ₁₂ film having a film thickness of 15 nm and a film thickness of 7 n
(Tb ₃₂ Fe ₅₆ Co ₁₂ ) ₉₂ O ₈ film with a thickness of 10 n
m SiN film and 20 nm thick Tb ₁₉ Fe ₆₂ Co ₁₀
Cr ₉ film, SiN film with a thickness of 10 nm, and film thickness of 70
nm Al film is sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

Tb ₃₂ Fe ₅₆ Co ₁₂ laminated directly on each other
The film and the (Tb ₃₂ Fe ₅₆ Co ₁₂ ) ₉₂ O ₈ film are the first recording layer 4
And two recording states exist in different magnetic field regions. The Tb ₁₉ Fe ₆₂ Co ₁₀ film is a single layer of the second recording layer 6
In a magnetic field region different from that of the first recording layer 4.
There are two record states. The magneto-optical recording medium of this example has a low absorptance of the laser beam as an auxiliary magnetic film forming the first recording layer 4 (Tb) for the purpose of not reducing the amount of the laser beam incident on the second recording layer 6. ₃₂ Fe ₅₆ Co ₁₂ )
_{A 92} O ₈ film was used and its thickness was adjusted to 7 nm. Since the other parts are the same as those in the first embodiment, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

<Thirteenth Embodiment> As shown in FIG. 27, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm is formed on the preformat pattern forming surface 2 of the transparent substrate 1.
A Tb ₃₂ Fe ₅₆ Co ₁₂ film having a film thickness of 15 nm and a film thickness of 2 n
m Gd ₃₀ Fe ₄₈ Co ₂₂ film and SiN having a film thickness of 10 nm
Film, Tb ₃₄ Fe ₅₂ Co ₁₄ film with a thickness of 20 nm, Pt ₉₄ Co ₆ film with a thickness of 5 nm, and SiN with a thickness of 10 nm
A film and an Al film having a film thickness of 70 nm are sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

Tb ₃₂ Fe ₅₆ Co ₁₂ laminated directly on each other
The film and the Gd ₃₀ Fe ₄₈ Co ₂₂ film form the first recording layer 4, and two recording states exist in different magnetic field regions. In addition, the Tb ₃₄ Fe ₅₂ Co ₁₄ film and the Pt layered directly on each other.
_{The 94} Co ₆ film constitutes the second recording layer 6, and two recording states exist in a magnetic field region different from that of the first recording layer 4.
The magneto-optical recording medium of the present example is a GdFeCo film having a low absorptance of a laser beam as an auxiliary magnetic film forming the first recording layer 4 for the purpose of not reducing the incident amount of the laser beam on the second recording layer 6. And the film thickness is 2 nm
Adjusted to. Since the other parts are the same as those in the first embodiment, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

<Sixth Configuration Example> In the magneto-optical recording medium according to the present example, the magnitude of the magnetization that determines the perpendicular magnetic anisotropy energy and the shape anisotropy energy is made independent by devising the auxiliary magnetic layer. And the response of the magnetization reversal of the perpendicular magnetization film to an external magnetic field can be easily controlled.

As the auxiliary magnetic layer belonging to this example, [C
o, Fe, Ni, Cr, Mn], which is a magnetic thin film containing at least one kind of metal element as a main component, the thickness of which is adjusted in the range of 1 to 30 Å,
Provided in contact with the surface of the perpendicular magnetization film, [Co, Fe, N
i, Cr, Mn] at least any one of
Kinds of metallic elements and [Pt, Al, Au, Rh, Pd, C
u, Ag, Re, Ru], a magnetic thin film containing an alloy with at least one kind of metal element as a main component, the thickness of which is adjusted in the range of 1 to 30 Å Provided in contact with the surface of the magnetic film, [Co, F
e, Ni, Cr, Mn], a metal thin film containing at least one kind of metal element, and [Pt, A
1, Au, Rh, Pd, Cu, Ag, Re, Ru] and a metal thin film containing at least one metal element selected from the following:
Examples of the method include providing the film in contact with the surface of the perpendicularly magnetized film and adjusting the film thickness of each metal thin film in the range of 1 to 30 Å.

When a material whose magnetic moment easily rotates in the direction of the external magnetic field near the recording temperature is used as the auxiliary magnetic layer, the balance between the perpendicular magnetic anisotropy energy and the shape anisotropy energy becomes important. That is, when the perpendicular magnetic anisotropy energy is too large, the magnetization is strongly fixed in the perpendicular direction, so that it becomes difficult for the magnetic moment to rotate in the external magnetic field direction, and when the magnetization is too large, This is because the shape anisotropy energy becomes remarkably dominant, the magnetic moment is fixed in the in-plane direction, and it is also difficult to rotate in the external magnetic field direction.

If the magnitude of the perpendicular magnetic anisotropy energy and the magnitude of the magnetization that determines the shape anisotropy energy can be independently controlled, an auxiliary magnetic layer suitable for a multilevel recording medium can be easily formed. it can. However, conventionally, it has been recognized that the magnitude of the perpendicular magnetic anisotropy energy and the magnitude of the magnetization that determines the shape anisotropy energy are determined by the material, so the range of materials that can be selected as the auxiliary magnetic layer material is narrow. It was difficult to obtain good recording characteristics.

A magnetic thin film whose main component is at least one kind of metal element selected from [Co, Fe, Ni, Cr, Mn], and [Co, Fe, Ni, Cr, M
n] and at least any one kind of metal element and [Pt, Al, Au, Rh, Pd, Cu, Ag, R
e, Ru], a magnetic thin film containing an alloy with at least one kind of metal element as a main component has a two-dimensional effect and surface anisotropy when the film thickness is formed to about 1 to 30 Å. The magnetic characteristics change due to the contribution of the magnetic field. Among them, there is a decrease in Curie temperature and manifestation of perpendicular magnetic anisotropy,
This makes it possible to switch between the recorded state and the erased state with a small external magnetic field. That is, the magnetic moment of a very thin magnetic thin film has good responsiveness to an external magnetic field in the direction perpendicular to the film surface, and particularly near the recording temperature, the relatively small external magnetic field causes the magnetic moment to tilt in the direction of application of the external magnetic field. Since this magnetic moment and the transition metal magnetic moment of the perpendicular magnetization film are exchange-coupled, the exchange coupling force sensitively affects the magnetization reversal of the perpendicular magnetization film during recording. Therefore, it becomes easy to control the response region of the magnetization reversal of the perpendicular magnetization film to the external magnetic field.

On the other hand, [Co, Fe, Ni, Cr, Mn]
A metal thin film containing at least one kind of metal element selected from [Pt, Al, Au, Rh, Pd, C
u, Ag, Re, Ru], a multilayer film formed by alternately laminating two or more metal thin films containing at least one kind of metal element selected from the group also exhibits characteristic magnetic characteristics. There is manifestation of perpendicular magnetic anisotropy. FIG. 28 shows a multilayer film of a Pt film and a Co film, the film thickness of the Pt film is 20Å,
FIG. 6 is a graph showing the change in perpendicular magnetic anisotropy energy when the film thickness of the Co film is changed with the total film thickness of 200 Å.
It can be seen that the perpendicular magnetic anisotropy is exhibited in the range of up to 30Å. Therefore, by selecting the film thickness at which the perpendicular magnetic anisotropy energy and the shape anisotropy energy are almost the same from the data thus obtained, the magnetic moment in the external magnetic field direction near the recording temperature can be obtained. The auxiliary magnetic layer can be easily rotated.

Examples of the magneto-optical recording medium of this example will be described below. <Fourteenth Embodiment> As shown in FIG. 29, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 1 are formed on the preformat pattern forming surface 2 of the transparent substrate 1.
0 nm Tb ₃₂ Fe ₅₆ Co ₁₂ film and 10 Å film thickness Co
Film, SiN film with a thickness of 10 nm, Tb ₃₂ Fe ₅₆ Co ₁₂ film with a thickness of 35 nm, and Pt ₈₀ Co with a thickness of 50 nm
₂₀ films and a SiN film having a film thickness of 150 nm are sequentially laminated,
Each of these films is covered with an ultraviolet curable resin film.

The SiN film having a thickness of 100 nm is the first dielectric layer 3, the SiN film having a thickness of 10 nm is the second dielectric layer 5,
The SiN film having a film thickness of 150 nm constitutes the third dielectric layer 7. Also, Tb ₃₂ Fe ₅₆ C laminated directly on each other
The o ₁₂ film and the Co film form the first magnetic layer 4, and are a Tb ₃₂ Fe ₅₆ Co ₁₂ film and a Pt ₈₀ Co film that are directly stacked on each other.
_{The 20} films form the second magnetic layer 6. Further, the ultraviolet curable resin film constitutes the protective layer 9.

The magneto-optical recording medium of the present example has the reproduction signal output characteristic shown in FIG. 147 described above according to the external magnetic field applied at the time of recording. Therefore, the magneto-optical recording medium of the present embodiment can record a quaternary signal according to the change of the external magnetic field. FIG. 30 shows changes in the reproducing CN ratio (carrier-to-noise ratio) with respect to the recording magnetic field between the recording state “0” and the recording state “3” (plus direction magnetic field) of the magneto-optical recording medium. As is clear from this figure, sufficient regeneration CN
The minimum external magnetic field (indicated by an arrow) required to obtain the ratio is
It was 200 (Oe) in the magneto-optical recording medium without the Co layer, but decreased to 50 (Oe) in the magneto-optical recording medium of the present example provided with the Co film having a thickness of 10 Å.

Further, a Co film, a Co film, which is an auxiliary magnetic film,
For each of the Ni film and the Mn film, the film thickness and sufficient recycled CN
The relationship with the minimum external magnetic field required to obtain the ratio was investigated.
The result is shown in FIG. As is clear from this figure, in the film thickness range of 1 to 30 Å, the transition property between the recorded state and the erased state with respect to the external magnetic field is remarkably improved regardless of which material is used.

Furthermore, in the case of using a FeCo alloy film, a CoNi alloy film, or a FeNi alloy film as the auxiliary magnetic film, the relationship between the film thickness and the minimum external magnetic field required to obtain a sufficient reproduction CN ratio is shown. Examined. The result is shown in FIG. As is clear from this figure, in the range of 1 to 30 Å, the transition property between the recorded state and the erased state with respect to the external magnetic field is significantly improved regardless of which material is used. Others [Co, Fe, Ni, Cr, Mn]
At least one kind of metal element selected from [Pt, Al, Au, Rh, Pd, Cu, Ag, Re,
It was found that the same effect can be obtained in any case by using the magnetic thin film whose main component is an alloy with at least one kind of metal element selected from Ru].

<Fifteenth Embodiment> As shown in FIG. 33, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 100 nm are formed on the preformat pattern forming surface 2 of the transparent substrate 1. 9 nm Tb ₃₂ Fe ₅₆ Co ₁₂ film with a film thickness of 6
(Tb ₃₂ Fe ₅₆ Co ₁₂ ) ₉₂ O ₈ film with a thickness of 7 n
m SiN film and 30 nm thick Tb ₃₂ Fe ₅₆ Co ₁₂
A multilayer film in which a film, a Co film having a film thickness of 8 Å and a Pt film having a film thickness of 12 Å are laminated in multiple layers, and the total film thickness is adjusted to 20 nm, a SiN film having a film thickness of 10 nm, and a film thickness A 50 nm Al film is sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The 100-nm-thick SiN film is the first dielectric layer 3, the 7-nm-thick SiN film is the second dielectric layer 5, and the 10-nm-thick SiN film is the third dielectric layer 7. I am configuring. Also, Tb ₃₂ Fe ₅₆ Co ₁₂ laminated directly on each other
The film and the _{(Tb 32 Fe 56 Co 12)} 92 O 8 film, constitutes the first magnetic layer 4, Tb ₃₂ Fe ₅₆ laminated directly to one another
The Co ₁₂ film and the PtCo multilayer film form the second magnetic layer 32. Further, the Al film constitutes the reflective film 8 and the ultraviolet curable resin film constitutes the protective layer 9.

Tb ₃₂ Fe ₅₆ C constituting the second magnetic layer 32
The o ₁₂ film has a rare earth-rich composition, and the PtCo multilayer film is coupled in parallel to the transition metal magnetic moment by exchange coupling. The magneto-optical recording medium of the present embodiment has the reproduction signal output characteristic shown in FIG. 148 described above according to the external magnetic field applied during recording. Therefore, the magneto-optical recording medium of the present embodiment can record a quaternary signal according to the change of the external magnetic field.

<Sixteenth Embodiment> As shown in FIG. 34, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 100 nm are formed on the preformat pattern forming surface 2 of the transparent substrate 1. 10nm and Tb ₂₂ Fe ₆₆ Co ₁₂ film, and the SiN film having a film thickness of 10nm, the film thickness is 30nm of Tb ₂₂ Fe ₆₆
Co ₁₂ film, Fe film with 10Å film thickness and T film with 15Å film thickness
The b film is laminated in multiple layers and the total film thickness is adjusted to 50 nm, the SiN film is 10 nm thick, and the film thickness is 5 nm.
A 0 nm Al film is sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film having a thickness of 100 nm is the first dielectric layer 3, and the two SiN films having a thickness of 10 nm are the second and third dielectric layers 3.
Of the dielectric layers 5 and 7 of FIG. Also, the film thickness is 1
Tb ₂₂ Fe ₆₆ Co ₁₂ film 0nm alone constitutes the first magnetic layer 4, Tb ₂₂ Fe ₆₆ Co laminated directly to one another
_{The 12} film and the TbFe multilayer film form the second magnetic layer 6. Further, the Al film constitutes the reflective film 8 and the ultraviolet curable resin film constitutes the protective layer 9.

Tb ₂₂ Fe ₆₆ Co forming the second magnetic layer 6
_{The 12} film has a transition metal-rich composition, and the transition metal magnetic moment of the TbFe multilayer film is coupled in parallel to the transition metal magnetic moment by exchange coupling. The magneto-optical recording medium of the present example has the reproduction signal output characteristics shown in FIG. 35 according to the external magnetic field applied during recording. Therefore, the magneto-optical recording medium of the present embodiment can record a quaternary signal according to the change of the external magnetic field.

<Seventeenth Embodiment> As shown in FIG. 36, the magneto-optical recording medium of this embodiment has a SiN film having a thickness of 100 nm and a thickness of 100 nm on the pre-format pattern forming surface 2 of the transparent substrate 1. 15 nm Tb ₃₂ Fe ₅₆ Co ₁₂ film, 10 nm thick SiN film, and 10 nm thick Tb ₂₂ Fe ₇₀
Co ₈ film, Co film with a film thickness of 10Å and C with a film thickness of 10Å
The u film is laminated in multiple layers and the total film thickness is adjusted to 50 nm, the SiN film is 10 nm thick, and the film thickness is 5 nm.
A 0 nm Al film is sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film having a thickness of 100 nm is the first dielectric layer 3, and the two SiN films having a thickness of 10 nm are the second and third dielectric layers.
Of the dielectric layers 5 and 7 of FIG. Also, the film thickness is 1
The 5 nm Tb ₃₂ Fe ₅₆ Co ₁₂ film independently constitutes the first magnetic layer 4 and is formed by directly laminating Tb ₂₂ Fe ₇₀ Co ₁₂ films.
_{The eight} films and the CoCu multilayer film form the second magnetic layer 6. Further, the Al film constitutes the reflective film 8 and the ultraviolet curable resin film constitutes the protective layer 9.

In the multilayer film, the exchange coupling force acts in parallel (ferro coupling) or anti-parallel action (antiferro coupling) depending on the thickness of each thin film. In FIG. 37, C
The thickness of Co in the CoCu multilayer film in which the o film and the Cu film are alternately laminated 20 times is set to 10 Å, and the change of the magnetoresistive effect when the thickness of Cu is changed is shown. In this graph, the bonds between the layers are antiparallel at the points showing peaks and parallel at the bottom. In the magneto-optical recording medium of this example, since the Co film having a film thickness of 10Å and the Cu film having a film thickness of 10Å are laminated in multiple layers, the coupling between the layers is antiparallel.

Tb ₂₂ Fe ₇₀ Co constituting the second magnetic layer 6
_{The 8} film has a transition metal-rich composition, and the transition metal magnetic moment and the Co film immediately above are ferro-coupled to each other and the Co film immediately above and the second Co film laminated thereon via the Cu film. Has an anti-ferro bond. The magneto-optical recording medium of the present embodiment, according to the external magnetic field applied at the time of recording,
It has the reproduction signal output characteristic shown in FIG. Therefore,
The magneto-optical recording medium of this embodiment can record a four-valued signal according to the change of the external magnetic field.

<Eighteenth Embodiment> As shown in FIG. 39, in the magneto-optical recording medium of the present embodiment, a SiN film having a film thickness of 100 nm and a film thickness of 100 nm are formed on the preformat pattern forming surface 2 of the transparent substrate 1. 10 nm Tb ₂₂ Fe ₆₆ Co ₁₂ film, 10 nm thick SiN film, and 20 nm thick Tb ₂₂ Fe ₇₀
Co ₈ film, Co film with a film thickness of 10Å and C with a film thickness of 10Å
The u film and the Co film having a film thickness of 10Å are laminated in three layers, and further, the Cu film having a film thickness of 5Å and the Co film having a film thickness of 10Å are laminated thereon over 20 layers, and the total film thickness is 33 nm. The multi-layered film, the SiN film having a thickness of 10 nm, and the Al film having a thickness of 50 nm are sequentially laminated, and each of these films is covered with an ultraviolet curable resin film.

The SiN film having a thickness of 100 nm is the first dielectric layer 3, and the two SiN films having a thickness of 10 nm are the second and third dielectric layers.
Of the dielectric layers 5 and 7 of FIG. Also, the film thickness is 1
The 0 nm Tb ₂₂ Fe ₆₆ Co ₁₂ film independently constitutes the first magnetic layer 4, and is formed by directly stacking Tb ₂₂ Fe ₇₀ Co ₁₂ films.
_{The eight} films and the CoCu multilayer film form the second magnetic layer 6. Further, the Al film constitutes the reflective film 8 and the ultraviolet curable resin film constitutes the protective layer 9.

Tb ₂₂ Fe ₇₀ Co constituting the second magnetic layer 6
_{The 8} film has a transition metal-rich composition, and the transition metal magnetic moment and the Co film immediately above are ferro-coupled to each other and the Co film immediately above and the second Co film laminated thereon via the Cu film. Has an anti-ferro bond. Also, the 2
The third Co film and the third Co film stacked on the third Co film via the Cu film are ferro-coupled. The magneto-optical recording medium of the present embodiment has the reproduction signal output characteristic shown in FIG. 35 described above according to the external magnetic field applied during recording. Therefore, the magneto-optical recording medium of the present embodiment can record a quaternary signal according to the change of the external magnetic field.

In addition, [Co, Fe, Ni, Cr, M
n], a metal thin film containing at least one kind of metal element, and [Pt, Al, Au, Rh, P
d, Cu, Ag, Re, Ru], a magneto-optical recording medium using a multilayer film formed by alternately laminating two or more metal thin films containing at least one kind of metal element selected from , The same effect was obtained.

The number of laminated layers of the multilayer film is appropriately adjusted in connection with the control of the exchange coupling force with the TbFeCo film which is the perpendicular magnetization film. Further, in the magneto-optical recording medium using the CoCu multilayer film as the auxiliary magnetic film, the first Co film in contact with the TbFeCo film may be omitted.

In the magneto-optical recording medium of the sixth configuration example, the recording state and the erasing state can be switched quickly in a low magnetic field, so that the operation of aligning the magnetization directions of the recording layers in the initial state is not performed. , Signal recording can be performed immediately.

<Seventh Configuration Example> The magneto-optical recording medium according to the present example is for realizing so-called magnetic super-resolution in the magneto-optical recording medium for multilevel recording as exemplified in the first to fifth configuration examples. It is characterized in that a film body of is added.

FIG. 40 is a block diagram showing an example of the above.
The case where the present invention is applied to a magneto-optical recording medium for multilevel recording having two recording layers is shown. As is clear from this figure, the magneto-optical recording medium of the present example is such that the first dielectric layer 101, the first hole forming layer 102, and the first hole forming layer 102 are formed on the transparent substrate 1.
Cutting layer 103, first perpendicular magnetic film layer 104, first auxiliary magnetic layer 105, second dielectric layer 106, second hole forming layer 107, second cutting layer 108, and second perpendicular layer. The magnetic film layer 109, the second auxiliary magnetic layer 110, and the third dielectric layer 11
1 and the reflective layer 112 in principle. The first recording layer 120 is constituted by a combination of the first perpendicular magnetization film layer 104 and the first auxiliary magnetic layer 105, and the second recording layer 12
1 is the second perpendicular magnetization film layer 109 and the second auxiliary magnetic layer 110.
It is composed by the combination with.

First hole forming layer 102 and first cutting layer 10
3 and the first recording layer 120 are composed of magnetic films magnetically exchange-coupled to each other at room temperature, and are laminated in this order in the incident direction of the reproducing laser beam. These magnetic films 102, 103, 120 have a Curie temperature of the first opening forming layer 102 of Tc ₁ , a coercive force of Hc ₁ ,
The Curie temperature of the first cutting layer 103 is Tc ₂ , its coercive force is Hc ₂ , and the Curie temperature of the first recording layer 120 is Tc ₃ .
The coercive force is Hc ₃ , the room temperature is T ₀ , and the first cutting layer 10
3 and the first recording layer 120 has an exchange magnetic field exerted on the first hole forming layer 102 by H _w and an external magnetic field applied at the time of reproduction (hereinafter referred to as a reproduction magnetic field) is H _r , the following conditions (1) to (4) are satisfied. Then, the Curie temperature and coercive force are adjusted. T ₀ <Tc ₂ <Tc ₁ , Tc ₃ Hc ₁ + H _w <H _r (however, the Curie temperature Tc of the first cutting layer 103 during reproduction)
Hc ₃ > H _r (in the region where the temperature rises to ₂ or the vicinity thereof) (however, the Curie temperature Tc of the first cutting layer 103 during regeneration)
Hc ₁ <H _w (at room temperature) in a region where the temperature is raised to ₂ or in the vicinity thereof.

The second hole forming layer 107, the second cutting layer 108, and the second recording layer 121 have the same structure.

The principle of reproducing a signal from the magneto-optical recording medium having the above structure will be described below with reference to FIG. In the magneto-optical recording medium, as shown in FIG.
Recording marks 120a and 121a having a diameter smaller than the spot diameter D of the reproduction light beam 130 are formed along the recording track.
Recording is performed at a pitch smaller than the spot diameter D of the reproduction light beam 130.

When the magneto-optical recording medium is irradiated with the reproducing light beam 130 while the magneto-optical recording medium is driven relatively to the optical head and the magnetic head, the energy thereof causes the first hole forming layer 102, First cutting layer 103, first recording layer 120, second hole forming layer 107, second cutting layer 10
8. The temperature of the second recording layer 121 is raised, but when the reproducing light beam 130 is irradiated along the recording track while driving the magneto-optical recording medium in the direction of arrow A, the reproducing light beam relatively travels. According to the temperature distribution in the irradiation part of 130, FIG.
As shown in (b), the trailing edge portion of the spot 131 has the highest temperature. Therefore, the intensity of the reproduction light beam 130 is
When the temperature of the high temperature region 131a is the first and second cutting layers 1
When adjusted so as to be at or above the Curie temperature Tc _{2 of} 03 and 108, the exchange magnetic field H _w exerted by the cutting layers 103 and 108 and the recording layers 120 and 121 on the aperture forming layers 102 and 107 is zero or very high. Small value,
The magnetic coupling between the hole forming layers 102 and 107 and the recording layers 120 and 121 is cut off.

In this state, when a reproducing magnetic field H _r larger than Hc ₁ + H _w is applied to each magnetic film, as shown in FIG. 41A, the high temperature region 131 of the hole forming layers 102 and 107 is formed.
The magnetization of the portion corresponding to a is aligned in the reproducing magnetic field direction, and the recording marks 120a and 121a of the aperture forming layers 102 and 107 in that area disappear. On the other hand, the high temperature region 13
In the portions other than 1a, the exchange magnetic field H _w maintains a large value, and the hole forming layers 102 and 107 and the recording layer 120,
Since it is magnetically coupled with 121, the recording marks 120a, 12 recorded on the aperture forming layers 102, 107 are formed.
1a is kept as it is. Therefore, when the reproducing light beam 130 is operated along the recording track, the recording marks 120a and 121a in the high temperature region 131a are masked for signal reading, and only the crescent-shaped portion of the spot 131 excluding the high temperature region 131a. Serves as an aperture, and the signals from the recording marks 120a and 121a are read out. Therefore, the magnetic interval pitch is the spot diameter D
It becomes possible to read a signal from the magneto-optical recording medium adjusted to about 1/2 of the above, and the reproduction resolution is improved.

The coercive force Hc of the recording layers 120 and 121
_{Since 3} is set to be larger than the reproducing magnetic field H _r ,
The recording marks 120a and 121a of the recording layers 120 and 121 are not erased by the application of the reproducing magnetic field H _r .
In addition, the reproduction light beam 1 is driven as the magneto-optical recording medium is driven.
The part of the irradiation layer 30 which is outside the irradiation part is sequentially cooled to room temperature, and when the temperature of the cutting layers 103 and 108 is cooled to Tc ₂ or lower, the exchange magnetic field H _w is restored between the magnetic films again. Therefore, due to the exchange coupling force, the recording layers 120, 1
Since the reversed magnetic domain 21 is transferred to the hole forming layers 102 and 107, the initial recording state does not disappear even if the signal reproducing operation is repeated. Therefore, as shown in FIG. 41 (c), the multi-level recorded signal is reproduced with high resolution by slicing the read total reproduced signal with a plurality of slice signals that match each signal level. be able to.

FIG. 42 shows another example of the multilevel recording signal reproducing method by the magnetic super resolution method. The reproduction method of this example is shown in FIG.
Unlike the first method, an initializing magnetic field is applied to the aperture forming layers 102 and 107 on the upstream side of the optical head to form an aperture in the high temperature portion 131a.

For a magneto-optical recording medium having a plurality of hole forming layers, the exchange coupling force acting between each recording layer and the hole forming layer may be different from each other, or each hole forming layer may be formed. By making the Curie temperatures of the layers different from each other, the reproduction signal can be read out for each recording layer.
That is, the opening portion at the time of irradiating the reproducing light becomes larger in the first recording layer closer to the reproducing light incident side. Therefore, the high temperature part 131
In the magneto-optical recording medium in which the aperture is formed in a,
The exchange coupling force acting between the first recording layer 120 and the first hole forming layer 102 is stronger than the exchange coupling force acting between the second recording layer 121 and the second hole forming layer 107. Or set the Curie temperature of the first hole forming layer 102 lower than the Curie temperature of the second hole forming layer 107, and select an appropriate reproducing laser beam of two powers,
As shown in FIG. 43, a signal can be reproduced only from the first recording layer by irradiating the magneto-optical recording medium with a low-power reproducing laser beam that does not have an opening in the second recording layer. it can. Also, as shown in FIG.
A signal can be reproduced only from the second recording layer by irradiating the magneto-optical recording medium with a high-power reproducing laser beam so that the aperture of the recording layer covers almost the entire reproduction spot.

In the magneto-optical recording medium in which the aperture is formed at the low temperature portion of the reproducing spot, the exchange coupling force acting between the first recording layer 120 and the first hole forming layer 102 is applied to the second recording layer 121. It is made weaker than the exchange coupling force acting with the second hole forming layer 107, or the Curie temperature of the first hole forming layer 102 is set to the second hole forming layer 107.
By setting it higher than the Curie temperature of
Alternatively, the signal can be selectively reproduced from the second recording layer.

The magnetic super-resolution type magneto-optical recording medium for multilevel recording does not necessarily have to include all the film bodies shown in FIG. 40, and one or a plurality of film bodies may be omitted as necessary. You can also FIG. 45 shows various film configurations included in the sixth configuration example. The blank in the table indicates that the film body is omitted.

In the first to seventh configuration examples,
Although the SiN film is used as the dielectric layers 3, 5, and 7, other materials can be used. That is, as the dielectric layer material, the temperature distributions during recording of the first and second recording layers 4 and 6 are made as equal as possible so that the sizes of the magnetic domains formed therein are made uniform, so that they are non-magnetic and have a low thermal conductivity. High materials are good. Suitable materials for this include [Si, Al, Ti, Zr,
Au, Cu, Mo, W], a metal element selected from the group: or an alloy containing at least one metal element selected from these as a main component, or an oxide or a nitride thereof. A material whose composition is richer in metal element than in stoichiometric composition is particularly suitable. The film thickness of each dielectric layer is appropriately adjusted so as to satisfy optical conditions.

Further, the Curie temperatures of the perpendicular magnetization films in the first to seventh embodiments need to be close to each other in order to make the sizes of the magnetic domains formed in the respective recording layers uniform. It is preferable to set the temperature within ± 50 ° C. at the maximum.

In addition, it is preferable that the perpendicularly magnetized films in the first to seventh embodiments have the same composition in order to facilitate film formation. As the auxiliary magnetic film, it is preferable to use a magnetic thin film that becomes an in-plane magnetized film at least near room temperature. Further, the auxiliary magnetic film is
It may be provided not only on one surface of the perpendicularly magnetized film but also on the laser beam incident side or the opposite side or both.

The high-density recording method for the magneto-optical recording medium and the recording / reproducing method with few errors from the high-density recording medium in which fine recording magnetic domains are formed will be listed below.

(1) Pulse reproduction a. A magneto-optical reproducing method in which a reproducing laser beam is irradiated periodically or in a pulsed manner.

B. The a. In the signal reproduction method, the reproduction laser light emission timing is synchronized by creating a timing clock from a signal reproduced from a medium such as a prepit or a magneto-optical signal.

(2) Waveform equalization for pulse reproduction c. The a. A method of performing signal processing represented by the following Expression 1 when the reproduced signal waveform according to the method of (1) is D ₀ (t).

[0191]

[Equation 1]

D. The c. Method, n = 0, ± 1, ±
2, a _n = a _−n , −1 <a _n <0.

(3) Magnetic field modulation reproduction e. A method of reproducing by modulating the magnitude and / or direction of the external magnetic field applied to a medium capable of magnetic super-resolution.

F. The a. In the above method, the magnitude and / or direction of the external magnetic field to be applied is modulated in synchronization with the emission timing of the reproducing laser beam. Playback method.

G. There are multiple recording pits in the reproduction light spot in the laser traveling direction or the cross track direction,
A recording / reproducing system in which each level of a reproduced signal developed by each combination of those recording states is determined in multiple stages.

(4) Trial reading h. The a. ~ G. In this method, the waveform of the laser light for reproduction (high power and low power values, the ratio of the time of high power and low power) and the magnetic field applied during reproduction are changed to perform reproduction, and the combination with the fewest errors is selected. Playback method to select.

I. The h. In the reproducing method, a method for recording a test pattern for reproducing trial on a medium in advance.

J. The h. The method is to record the optimum playback conditions obtained by the method on the medium and read it from the next playback to perform playback.

Next, the format structure of the magneto-optical recording medium according to the present invention will be described.

<First Example of Format Configuration> FIG.
An example of a pre-format pattern formed on a sample servo type magneto-optical recording medium is shown. The pre-format pattern 2 defines a recording track and a data recording unit formed by dividing the recording track, and can be recorded on the surface of the transparent substrate 1 in the form of unevenness.
It can also be recorded as a magneto-optical signal on the magnetic layers 4, 6 and the like.

In this example, the recording track 11 is divided into a large number of data recording units 12, and each data recording unit 1
2 is divided into an ID area 13, a servo area 14, and a data area 15. In the ID area 13, a mark indicating the boundary of each data recording unit 12, an address of the data recording unit, an error detection code, and the like are formed. In the servo area 14, as shown in FIG. 47, a tracking pit 16 for scanning a recording or reproducing laser beam along the recording track 11, a test area 17 for optimum recording / reproducing, and a signal Embedded clock pits 18 necessary for pulling in the reference clock required for recording and reproducing are formed. In the test area 17, a test signal (level detection pit) 17a for setting the slice level of each signal included in the multi-valued recording signal recorded in the recording area 14 and / or multi-valued recording, if necessary. A test signal (timing detection pit) 17b for generating a timing signal that serves as a reference for the timing of detecting the edge of the signal is recorded. In the data area 15, a multi-valued recording signal is recorded as a magneto-optical recording signal.

Instead of providing the tracking pit 16 in the servo area 14, a guide groove for guiding the laser beam for recording or reproduction along the recording track 11 is provided.
It can also be formed on the transparent substrate 1.

Further, the pre-pits (phase pits) formed on the surface of the transparent substrate in the form of, for example, irregularities can be multi-valued recording corresponding to the medium. The multi-value of the pre-pit is the modulation of the length, width, and depth of the pre-pit, or the deviation amount of the pre-pit position in the direction perpendicular to the track direction,
Alternatively, it can be realized by a combination thereof.

<Second Example of Format Configuration> The format configuration of this example is a test for detecting an optimum recording condition in an area other than the user area where the user accesses and records, reproduces, or erases a signal. It is characterized in that a region is provided. FIG. 48 is a diagram showing an embodiment when applied to a CAV (constant angular velocity) optical disc, in which the user area 21
A test area 22 is provided on the innermost and outermost circumferences of the disk. The test area 22 is
It is also possible to provide only on either the innermost peripheral portion or the outermost peripheral portion of the disc. In addition, FIG. 49 shows ZCAV (Zone
FIG. 9 is an embodiment diagram when applied to a d-CAV) type optical disc, in which a test area 22 is provided near a zone boundary portion. In the ZCAV type optical disc, as in the CAV type optical disc, the test areas 22 may be provided in the innermost and outermost portions of the disc.

Since the format configuration of each data recording unit in the user area is the same as that described in the first example, the description thereof will be omitted to avoid duplication.

Hereinafter, a multilevel signal recording method using the magneto-optical recording medium according to the present invention will be described.

<First Example of Multi-Valued Recording Method> The multi-valued recording method of this example is characterized in that an external magnetic field is modulated in three steps according to a recording signal and a recording laser beam is modulated in a pulsed manner. And As the magneto-optical recording medium, the magneto-optical recording medium according to the first configuration example (the medium illustrated in FIGS. 9 and 10; more specifically, the medium illustrated in FIGS. 11 to 16) is used.

First, the magneto-optical recording medium is mounted on a medium driving unit such as a turntable, the optical head is arranged on the transparent substrate side, and the magnetic head is arranged on the protective film side. The medium drive unit is activated to drive the magneto-optical recording medium, the optical head and the magnetic head relatively at a predetermined linear velocity, and position the optical head and the magnetic head on a predetermined track.

Then, as shown in FIG. 50 (a),
The magnetic field strength applied from the magnetic head according to the recording signal is from H ₀ to
An external magnetic field is applied to the optical information recording medium, which is signal-modulated into the H ₂ ternary value and synchronized with the recording clock. Then, after the external magnetic field is switched to a predetermined value, the optical pulse is irradiated from the optical head as shown in FIG. 50B to heat each recording layer of the optical pulse irradiation unit to a temperature at which the magnetization can be reversed by the external magnetic field. . As a result, the magnetization domain of FIG. 50C corresponding to the magnitude of the external magnetic field is formed in the irradiation portion of each light pulse.

In FIG. 50 (c), the magnetization states of the magnetization domains recorded in the three values are identified by vertical lines, lattices, and white backgrounds, respectively. The white background represents the case where the combinations of the magnetization directions of the perpendicular magnetization films constituting the magneto-optical recording medium according to the first configuration example are both downward, and the vertical line represents one perpendicular magnetization film constituting the magneto-optical recording medium. Represents the case where the magnetization direction of the perpendicular magnetic film is upward and the magnetization direction of the other perpendicular magnetic film is downward, and the lattice represents the case where the combination of the magnetic directions of the perpendicular magnetic films constituting the magneto-optical recording medium are both upward. ing.

<Second Example of Multi-Valued Recording Method> The multi-valued recording method of this example is characterized in that an external magnetic field is applied at a constant cycle, and a recording laser beam is modulated in three steps according to a recording signal. And The magneto-optical recording medium according to the fourth embodiment (FIG. 14) is used as the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on predetermined tracks in the same manner as in the first example, as shown in FIG. 51A, the central magnetic field is zero magnetic field from the magnetic head. And an external magnetic field whose amplitude is set to be equal to or higher than the magnetic field strength in the recording state is periodically applied. Then, when the external magnetic field is switched to a predetermined value, it is modulated by the optical head according to the recording signal.
The three-stage light pulse shown in FIG. 1 (b) is irradiated to heat each recording layer of the light pulse irradiation portion to a temperature at which the magnetization can be reversed by the external magnetic field. As a result, a magnetization domain corresponding to the magnitude of the external magnetic field is formed at the irradiation portion of each light pulse.

In the magneto-optical recording medium according to the first configuration example, as shown in FIGS. 10A to 10G, the center of the magnetic field strength in the recording state is shifted from the zero magnetic field in the recording direction or the erasing direction. The bias magnetic field is applied to the external magnetic field by an amount corresponding to the shift amount of the magneto-optical recording medium.

<Third example of multi-value recording method> The multi-value recording method of this example is a so-called partial response method (PRM).
The multilevel recording signal of L) is recorded. As the magneto-optical recording medium, the magneto-optical recording medium according to the first configuration example (the medium shown in FIGS. 9 and 10; more specifically, FIG.
The medium etc. which were illustrated in 1-16. ) And the magneto-optical recording medium according to the second configuration example (FIGS. 17 and 18) can be used.

In order to drive the magneto-optical recording medium and position the optical head and the magnetic head on a predetermined track in the same manner as in the first example, in order to perform ternary recording corresponding to PRML recording, FIG. , A precoder is used to give 1-bit (1T) intersymbol interference to the data signal.
Perform RZI conversion. This NRZI converted signal is delayed by 1 bit (1T) using a shift register to generate a signal. Then, the signal obtained by logically adding the signals and the signal obtained by the logical product are combined. further,
The signal and the signal are generated by using the external magnetic field applying circuit c illustrated in the magnetic head driving circuit shown in FIG. 54. Specifically, the signal is output from the circuit of FIG.
A signal obtained by logically inverting the signal is input to pulse1-P in pulse1-P in the circuit of FIG. On the other hand, the signal is pulse2-P in the circuit of FIG. 54, and the signal obtained by logically inverting the signal is shown in FIG.
Input to pulse2-N of the 4th circuit. Then, by applying a voltage to each of V _i1 and V _i2 of the circuit of FIG. 54, an external magnetic field modulated into three values of H _{0 to} H ₂ synchronized with the recording clock is magneto-optically recorded by using the magnetic head d. Apply to the medium.
Then, after the external magnetic field is switched to a predetermined value, the optical pulse is irradiated from the optical head as shown in FIG. 52B to heat each recording layer of the optical pulse irradiation unit to a temperature at which the magnetization can be reversed by the external magnetic field. . As a result, a magnetization domain shown in FIG. 52 (c) corresponding to the magnitude of the external magnetic field is formed at the irradiation portion of each light pulse. Alternatively, the light may be continuously emitted while modulating the external magnetic field.

The recording state of the magnetization domain according to the magnitude of each external magnetic field of the magneto-optical recording medium according to the second configuration example is similar to that shown in FIGS. 10 (a) to 10 (h). Therefore, the reproduction signal read from the magnetization domain sequence is as shown in FIG. 52 (d). When this reproduced signal is sliced at two slice levels set to a predetermined value according to the reproduced signal output from each recording state, as shown in the timing chart of FIG. 52 (e), two binarized signals sig
1 and sig2 are obtained. Binarization can be performed by performing a logical operation on these two signals.

FIG. 53 shows an example of the structure of the recording / reproducing system of this embodiment. In this embodiment, a signal for applying an external magnetic field is generated by the method described above, an external magnetic field is generated in the magnetic head d using the external magnetic field applying circuit c, and a laser light pulse synchronized with the clock g is also generated. It is generated by the laser driving circuit h and recording is performed on the magneto-optical recording medium f. Magneto-optical recording medium f
The magnetic domain recorded in is reproduced by the optical head e and I-
After photoelectric conversion by the V conversion circuit i, optical system intersymbol interference is suppressed by the equalizer j, and A / D conversion is performed by the A / D converter k. This data passes through a digital cosine equalizer l that absorbs a difference in linear velocity (difference between inner and outer circumferences) of the magneto-optical recording medium f, is ternary judged by a ternary judgment device m, and is supplied to a Viterbi decoder n to be binarized. , Obtain the reproduced data signal o. On the other hand, the recovered clock is generated by binarizing the equalizer output using the clock generation circuit p. This clock is supplied to the ternary decision unit m and the Viterbi decoder n.

<Fourth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is also the so-called partial response method (PRM).
The multilevel recording signal of L) is recorded. As the magneto-optical recording medium, the magneto-optical recording medium according to the first configuration example (the medium shown in FIGS. 9 and 10; more specifically, FIG.
The medium etc. which were illustrated in 1-16. ) And the magneto-optical recording medium according to the second configuration example (FIGS. 17 and 18) can be used.

In order to drive the magneto-optical recording medium and position the optical head and the magnetic head on a predetermined track in the same manner as in the first example, to perform ternary recording corresponding to PRML recording, FIG. As shown in, a precoder performs interleaved NRZI conversion to give 2-bit (2T) intersymbol interference to a data signal, and PR (1,0, -1)
In order to obtain a recording signal corresponding to, an external magnetic field is applied from the magnetic head to the optical information recording medium in which the applied magnetic field intensity is signal-modulated into three values of H _{0 to} H ₂ and synchronized with the recording clock. Then, after the external magnetic field is switched to a predetermined value, the optical pulse is irradiated from the optical head as shown in FIG. 55 (b) to heat each recording layer of the optical pulse irradiation unit to a temperature at which the magnetization can be reversed by the external magnetic field. . As a result, the irradiation portion of each light pulse is adjusted according to the magnitude of the external magnetic field shown in FIG.
The magnetization domain of (c) is formed. Alternatively, the light may be continuously emitted while modulating the external magnetic field.

The recorded state of the magnetization domain according to the magnitude of each external magnetic field is as shown in FIG. Therefore, the reproduction signal read from the magnetization domain sequence is
It becomes like FIG.55 (d). When this reproduced signal is sliced at two slice levels set to a predetermined value according to the reproduced signal output from each recording state, as shown in the timing chart of FIG. 55 (e), two binarized signals si
g1 and sig2 are obtained. Binarization can be performed by performing a logical operation on these two signals.

FIG. 56 shows an example of the structure of the recording / reproducing system of this embodiment. In the present embodiment, after the reproduced light is IV converted, it is passed through an analog waveform equalizer to remove optical intersymbol interference to obtain PR characteristics, and the analog signal is converted into an A / D signal.
Converted After that, the digital transversal filter absorbs the difference between the inner and outer peripheral characteristics to determine a ternary value, which is supplied to a Viterbi decoder and binarized. The reproduction clock was generated by the signal after A / D conversion.

<Fifth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is also the so-called partial response method (PRM).
The multilevel recording signal of L) is recorded. As the magneto-optical recording medium, the magneto-optical recording medium according to the first configuration example (the medium shown in FIGS. 9 and 10; more specifically, FIG.
The medium etc. which were illustrated in 1-16. ) And the magneto-optical recording medium according to the second configuration example (FIGS. 17 and 18) can be used.

In order to drive the magneto-optical recording medium and position the optical head and the magnetic head on a predetermined track in the same manner as in the first example, to perform ternary recording corresponding to PRML recording, FIG. As shown in, a precoder performs interleaved NRZI conversion on a data signal to give 2-bit (2T) intersymbol interference, shifts the binary data by 1 bit, and adds it to the original signal to create ternary data. Yes ((1 + T) characteristic is added). Corresponding to the ternary data, an external magnetic field is applied to the optical information recording medium from the magnetic head, the applied magnetic field intensity of which is modulated into three values of H _{0 to} H ₂ and which is synchronized with the recording clock. Then, after the external magnetic field is switched to a predetermined value, the optical pulse is irradiated from the optical head as shown in FIG. 57 (b) to heat each recording layer of the optical pulse irradiation unit to a temperature at which the magnetization can be reversed by the external magnetic field. . As a result, the magnetization domain of FIG. 57C corresponding to the magnitude of the external magnetic field is formed in the irradiation portion of each light pulse. Alternatively, light may be continuously emitted while modulating the external magnetic field.

The recorded state of the magnetization domain according to the magnitude of each external magnetic field is as shown in FIG. Therefore, the reproduction signal read from the magnetization domain sequence is
The original waveform is shown in FIG. 57 (d). 57. When this reproduced signal is sliced at two slice levels set to predetermined values according to the reproduced signal output from each recording state, FIG.
As shown in the timing chart of (e), two binarized signals sig1 and sig2 are obtained. Binarization can be performed by performing a logical operation on these two signals.

FIG. 58 shows a structural example of the recording / reproducing system of this embodiment. In the present embodiment, as shown in FIG. 58, after reproducing light is IV converted, optical intersymbol interference is removed by passing through an analog waveform equalizer to obtain PR characteristics, and an analog signal is converted. A / D converted. After the digital transversal filter absorbs the difference between the inner and outer circumference characteristics, the digital filter differentiates (adds the characteristic of (1-T)) three-values to the signal, and supplies the signal to the Viterbi decoder. Binarized. The reproduction clock was generated by the signal after A / D conversion.

Also, the original waveform of FIG. 57 (d) may be differentiated. When this is sliced, the two binarized signals sig. 3, sig. 4 is obtained and can be binarized by the logical operation thereof. In the case of the present example, as shown in FIG. 59, the analog signal that has been IV converted is differentiated or shifted by 1 bit to make a difference (the characteristic of (1-T) is added), an analog waveform, etc. The optical intersymbol interference was removed by passing it through a converter to obtain PR characteristics, and the analog signal was A / D converted. Then, after deciding the ternary value with respect to the signal in which the difference between the inner and outer peripheral characteristics is absorbed by the digital transversal filter, it is supplied to the Viterbi decoder and binarized. The reproduction clock was generated by the signal after A / D conversion.

<Sixth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is a so-called partial response method (PRM).
When the multilevel recording signal of L) is recorded, the magnetic domain length is set to be half the laser beam spot diameter or less, so that the magneto-optical recording medium according to the second configuration example (FIGS. 17 and 18) is recorded with five or more values. It is characterized by performing.

In order to drive the magneto-optical recording medium and position the optical head and the magnetic head on a predetermined track in the same manner as in the first example, in order to perform five-value recording corresponding to PRML recording, FIG. NRZI conversion that gives 1-bit (1T) intersymbol interference to the data signal,
In order to obtain a recording signal corresponding to (1,2,1) equalization, an external magnetic field that is signal-modulated by the magnetic head into three values of H _{0 to} H ₂ and synchronized with the recording clock is applied. It is applied to the optical information recording medium. Then, after the external magnetic field is switched to a predetermined value, the optical pulse shown in FIG. 60 (b) is emitted from the optical head to heat each recording layer of the optical pulse irradiation unit to a temperature at which the magnetization can be reversed by the external magnetic field. . As a result, the magnetized domain of FIG. 60C corresponding to the magnitude of the external magnetic field is formed in the irradiation portion of each light pulse.

The recorded state of the magnetization domain according to the magnitude of each external magnetic field is as shown in FIG. Therefore, the reproduction signal read from the magnetization domain sequence is
It becomes like FIG.60 (d). When this reproduced signal is sliced at two slice levels set to a predetermined value according to the reproduced signal output from each recording state, as shown in the timing chart of FIG. 60 (e), four binarized signals si
g1 to sig4 are obtained. Binarization can be performed by performing a logical operation on these four signals.

FIG. 61 shows an example of the structure of the recording / reproducing system of this embodiment. In the present embodiment, after the reproduced light is IV converted, it is passed through an analog waveform equalizer to remove optical intersymbol interference to obtain PR characteristics, and the analog signal is converted into an A / D signal.
Converted After that, the digital transversal filter absorbs the difference between the inner and outer circumference characteristics to determine 5 values, and then supplies them to the Viterbi decoder to perform binarization. The reproduction clock was generated from the signal after A / D conversion.

<Seventh Example of Multi-Valued Recording Method> The multi-valued recording method of this example is also the so-called partial response method (PRM).
When the multilevel recording signal of L) is recorded, it is characterized in that the magneto-optical recording medium according to the second configuration example (FIGS. 17 and 18) is used to perform recording with five or more values.

In order to drive the magneto-optical recording medium and position the optical head and the magnetic head on a predetermined track in the same manner as in the first example, to perform five-value recording corresponding to PRML recording, FIG. , The interleaved NRZI that gives 2-bit (2T) intersymbol interference to the data signal.
The magnetic field strength applied from the magnetic head is H so that a recording signal corresponding to PR (1, 2, 1) equalization is obtained by performing conversion.
An external magnetic field, which is signal-modulated into 5 values from _{0 to} H ₄ and is synchronized with a recording clock, is applied to the optical information recording medium. Then, after the external magnetic field is switched to a predetermined value, the optical head irradiates the optical pulse shown in FIG. 62B to heat each recording layer of the optical pulse irradiation unit to a temperature at which the magnetization can be reversed by the external magnetic field. . As a result, the magnetized domain of FIG. 62 (c) corresponding to the magnitude of the external magnetic field is formed in the irradiation portion of each light pulse.

The recorded state of the magnetization domain according to the magnitude of each external magnetic field is as shown in FIG. Therefore, the reproduction signal read from the magnetization domain sequence is
It becomes like FIG.62 (d). When this reproduced signal is sliced at two slice levels set to predetermined values according to the reproduced signal output from each recording state, as shown in the timing chart of FIG. 62 (e), four binarized signals si
g1 to sig4 are obtained. Binarization can be performed by performing a logical operation of these four signals.

FIG. 63 shows an example of the structure of the recording / reproducing system of this embodiment. In the present embodiment, after the reproduced light is IV converted, it is passed through an analog waveform equalizer to remove optical intersymbol interference to obtain PR characteristics, and the analog signal is converted into an A / D signal.
Converted After that, the digital transversal filter absorbs the difference between the inner and outer circumference characteristics to determine 5 values, and then supplies them to the Viterbi decoder to perform binarization. The reproduction clock was generated by the signal after A / D conversion.

<Eighth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is characterized in that a multi-valued recording signal coded by using a so-called trellis coding modulation method is recorded. As the magneto-optical recording medium, magneto-optical recording media according to the first to fifth configuration examples (for example, FIG. 15, FIG. 23 to FIG. 27, FIG.
9, the medium of FIGS. 33, 34, 36, 39, and the like. ) Can be used.

Driving the magneto-optical recording medium in the same manner as in the first example.
Position the optical head and magnetic head on the specified track.
After attaching, four-valued notation corresponding to four-phase orthogonal modulation trellis code
Encoding with the convolutional encoder shown in FIG. 64 to perform recording
I do. FIG. 65 (a) is the same as the convolutional encoder of FIG.
X when inputting data₁ , X₂ Indicates the state of. on the other hand,
As described above, the magneto-optical recording medium of FIG.
With signal characteristics for external magnetic field as shown in (b)
There is. Therefore, X shown in FIG.₁ , X₂In order
X so that the signal amplitude is allocated₁, X₂Applied magnetism using
Field strength is H₀ ~ H ₃ Intensity modulation to 4 values of
Synchronize the intensity-modulated four-valued external magnetic field with the recording clock
And then applied to the optical information recording medium. And the external magnetic field is
After switching to a fixed value, illuminate an optical pulse from the optical head.
The recording layer of the optical pulse irradiation section by an external magnetic field.
And heat to a temperature at which the magnetization can be reversed. This allows each
Depending on the magnitude of the external magnetic field, the magnetized
The main is formed. In this case, the external magnetic field is modulated
While continuously irradiating a laser beam with a constant intensity
Good.

FIG. 66 shows an example of the structure of the recording / reproducing system of this embodiment. In this embodiment, after the reproduced light is IV converted, it is passed through an analog waveform equalizer to remove optical intersymbol interference, and the analog signal is A / D converted. After that, the digital transversal filter absorbs the difference between the inner and outer circumference characteristics to determine a four-value, and supplies it to the Viterbi decoder for binarization. The reproduction clock was generated by the signal after A / D conversion.

<Ninth Example of Multilevel Recording Method> The multilevel recording method of this example is characterized in that signal recording is performed using the magneto-optical recording medium (FIGS. 19 and 20) according to the third configuration example. To do. In the signal recording of this example, a magnetic head having two windings that can be driven independently of each other is used.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on predetermined tracks in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 67, the intensity of the auxiliary magnetic field is changed so as to be synchronized with the main magnetic field according to the recording data while applying the main magnetic field having the amplitude across the two recording states of the recording medium at a constant frequency. Then, a magnetic domain having a domain length corresponding to the auxiliary external magnetic field strength is formed. As a result, so-called pit edge recording can be realized.

<Tenth Example of Multi-Valued Recording Method> In the multi-valued recording method of this example also, the magneto-optical recording medium according to the third configuration example (see FIG. 19,
20) is used to perform signal recording. In the signal recording of this example, an optical head is arranged on the transparent substrate side and a magnetic head is arranged on the protective film side through the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on a predetermined track in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 68, a laser radiated from the optical head so as to be synchronized with the external magnetic field according to the recording data while applying an external magnetic field having an amplitude across the two recording states of the recording medium at a constant frequency. The intensity is changed to Pw ₁ and Pw ₂ , and a magnetic domain having a magnetic domain length corresponding to the time when the laser intensity is changed is formed.
As a result, so-called pit edge recording can be realized.

<Eleventh Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, the magneto-optical recording medium according to the third configuration example (see FIG. 19,
20) is used to perform signal recording. In the signal recording of this example, an optical head is arranged on the transparent substrate side and a magnetic head is arranged on the protective film side through the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on a predetermined track in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 69, the frequency of the external magnetic field is frequency-modulated according to the recording data while applying the external magnetic field having an amplitude across the two recording states of the recording medium at a constant frequency, and the magnetic head is driven. Form a frequency-modulated magnetizing domain with twice the frequency. As a result, so-called pit position recording can be realized. Also, analog recording can be realized by frequency-modulating an analog signal such as a video signal.

<Twelfth Example of Multi-Valued Recording Method> Also in the multi-valued recording method of this example, the magneto-optical recording medium according to the third configuration example (see FIG. 19,
20) is used to perform signal recording. In the signal recording of this example, an optical head is arranged on the transparent substrate side and a magnetic head is arranged on the protective film side through the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on a predetermined track in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 70, the frequency of the external magnetic field is frequency-modulated according to the recording data while applying the external magnetic field having the amplitude across the two recording states and the two erasing states of the recording medium at a constant frequency. ,
A frequency-modulated magnetization domain having a frequency three times the driving frequency of the magnetic head is formed. As a result, so-called pit position recording can be realized. Also, analog recording can be realized by frequency-modulating an analog signal such as a video signal.

<Thirteenth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is the same as that of the magneto-optical recording medium (FIG. 21,
22) is used to perform signal recording. In the signal recording of this example, an optical head is arranged on the transparent substrate side and a magnetic head is arranged on the protective film side through the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on a predetermined track in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 71, the frequency of the external magnetic field is frequency-modulated according to the recording data while applying the external magnetic field having the amplitude across the two recording states and the two erasing states of the recording medium at a constant frequency. ,
A frequency-modulated magnetization domain having a frequency four times the driving frequency of the magnetic head is formed. As a result, so-called pit position recording can be realized. Also, analog recording can be realized by frequency-modulating an analog signal such as a video signal.

<Fourteenth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is the magneto-optical recording medium according to the first configuration example (the medium of FIG. 9. Specifically, the medium of FIGS. 11 to 16). Etc.) is used to perform signal recording. In the signal recording of this example, a magnetic head having two windings that can be driven independently of each other is used.

The magneto-optical recording medium is driven in the same manner as in the first example, the optical head and the magnetic head are positioned on predetermined tracks, and then the laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 72, the intensity of the auxiliary magnetic field is changed so as to be synchronized with the main magnetic field according to the recording data while applying the main magnetic field having the amplitude across the two recording states of the recording medium at a constant frequency. Then, a magnetic domain having a domain length corresponding to the auxiliary external magnetic field strength is formed. As a result, so-called pit edge recording can be realized.

<Fifteenth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is the magneto-optical recording medium according to the first configuration example (the medium of FIG. 9. Specifically, the medium of FIGS. 11 to 16). Etc.) is used to perform signal recording. In the signal recording of this example, an optical head is arranged on the transparent substrate side and a magnetic head is arranged on the protective film side through the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on a predetermined track in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 73, a laser irradiating from the optical head so as to be synchronized with the external magnetic field according to the recording data while applying an external magnetic field having an amplitude across the two recording states of the recording medium at a constant frequency. The intensity is changed to Pw ₁ and Pw ₂ , and a magnetic domain having a magnetic domain length corresponding to the time when the laser intensity is changed is formed.
As a result, so-called pit edge recording can be realized.

<Sixteenth Example of Multi-Valued Recording Method> Also in the multi-valued recording method of this example, the magneto-optical recording medium according to the first configuration example (the medium of FIG. 9; specifically, the medium of FIGS. 11 to 16). Etc.) is used to perform signal recording. In the signal recording of this example, the optical head is arranged on the transparent substrate side and the magnetic head is arranged on the protective film side via the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on a predetermined track in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 74, while applying an external magnetic field having an amplitude across all recording states of the recording medium at a constant frequency, a laser irradiating from the optical head is synchronized with the external magnetic field according to the recording data. By changing the intensity from Pw _1, a magnetization domain having a magnetic domain length corresponding to the laser intensity (Pw ₂ ) is formed. As a result, so-called pit edge recording can be realized.

<17th Example of Multi-Valued Recording Method> In the multi-valued recording method of this example also, the magneto-optical recording medium according to the fourth configuration example (see FIG. 21,
22) is used to perform signal recording. In the signal recording of this example, an optical head is arranged on the transparent substrate side and a magnetic head is arranged on the protective film side through the magneto-optical recording medium.

After driving the magneto-optical recording medium and positioning the optical head and the magnetic head on a predetermined track in the same manner as in the first example, a laser beam is irradiated from the optical head to cover the recording layer of the laser beam irradiation section. Heat to a temperature at which the magnetization can be reversed by an external magnetic field. In this state, as shown in FIG. 75, the frequency of the external magnetic field is frequency-modulated according to the recording data while applying the external magnetic field having the amplitude across the two recording states of the recording medium at a constant frequency. Then, the intensity of the laser applied in synchronization with the external magnetic field is modulated to control the magnetic domain length.

<Eighteenth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is characterized in that an external magnetic field is modulated in four steps according to a recording signal and a recording laser beam is modulated in a pulse shape. And As the magneto-optical recording medium, the magneto-optical recording medium according to the fifth configuration example (the medium of FIG. 23. Specifically, FIGS. 24 to 27, FIG. 29, FIG. 33, FIG. 34, FIG. 36, FIG.
9 media etc. ) Is used.

First, the magneto-optical recording medium is mounted on a medium driving unit such as a turntable, and the optical head is arranged on the transparent substrate side and the magnetic head is arranged on the protective film side. The medium drive unit is activated to drive the magneto-optical recording medium, the optical head and the magnetic head relatively at a predetermined linear velocity, and position the optical head and the magnetic head on a predetermined track.

After that, as shown in FIG. 76 (a),
The magnetic field strength applied from the magnetic head according to the recording signal is from H ₀ to
An external magnetic field, which is signal-modulated into four values of H ₃ and synchronized with a recording clock, is applied to the optical information recording medium. Then, after the external magnetic field is switched to a predetermined value, the optical pulse is irradiated from the optical head as shown in FIG. 76 (b) to heat each recording layer of the optical pulse irradiation unit to a temperature at which the magnetization can be reversed by the external magnetic field. . As a result, the magnetization domain of FIG. 76 (c) corresponding to the magnitude of the external magnetic field is formed at the irradiation portion of each light pulse.

In FIG. 76 (c), the magnetization state of each magnetization domain recorded in four values is identified by a diagonal line to the right, a diagonal line to the left, a vertical line, and a white background.
In the white background, the combination of the magnetization directions of the perpendicular magnetic films forming the magneto-optical recording medium of the fifth configuration example is in the state "0" of FIG. 80 (a).
80A, and the diagonal line descending to the left indicates that the state is “1” in FIG. Also, the diagonal line to the lower right represents the state "2" in FIG. 80 (a), and the vertical line represents the state "3" in FIG. 80 (a).

Signal modulation of the magnetic field intensity can be performed by the system of FIG. 77 and the signal modulation circuit of FIG. 78 or 79. The circuit shown in FIG. 54 can be used as the magnetic head drive circuit in FIGS. 78 and 79. That is, by taking the logical product of the recording clock and the data signal (Sig.1) shown in the timing chart of FIG. 76 (e), the odd data (Sig.2) is obtained.
Generate Also, by taking the logical product of the signal obtained by inverting the recording clock and the data signal, the even data (S
ig. 3) is generated. A signal obtained by doubling the length of the odd data signal is generated by taking the logical sum of the signal obtained by delaying the odd data by 1/2 clock using the shift register and the original odd data. . Similarly, a signal is generated from the even data. These signals,
The amplifiers G ₁ and G ₂ having different gains are respectively amplified and added. Next, this added signal is subjected to voltage-current conversion by the magnetic head drive circuit so that the external magnetic field shown in FIG. 77 (b) is applied from the magnetic head.

Further, in the circuit of FIG. 79, the recording signal is separated into even bits and odd bits, and after waveform processing such as timing adjustment and pulse length adjustment is performed, the gains are respectively amplified by the same amplifier G. . Next, each amplified signal is subjected to voltage-current conversion by a separate magnetic head drive circuit, and the external magnetic field shown in FIG. 77 (b) is applied from the magnetic head having a plurality of windings.

Instead of the magnetic head, it is of course possible to use another magnetic field generator such as an electromagnetic coil. Further, two magnetic heads each having one winding are arranged close to each other, and the magnetic heads shown in FIG.
The external magnetic field shown in (b) can also be applied.

The recording state of the magnetization domain according to the magnitude of each external magnetic field is as shown in FIG. Therefore,
The reproduction signal read from the magnetization domain sequence is shown in FIG.
It becomes like (d). When this reproduced signal is sliced at three slice levels set to predetermined values according to the reproduced signal output from each recording state, the recorded signal can be demodulated as shown in the timing chart of FIG. 76 (e). Specifically, when the analog reproduction signal of FIG. 76 (d) is binarized at slice level 1, sig. 1 is obtained. Similarly, sig. 2 is obtained, and sig. 3 is obtained. The odd data signal of FIG. 76 (e) is sig. 2 is the inverted signal and sig. 3 and the signal of 3 and then sig. 1 signal and the sig. It is obtained by taking the logical product of 3. Then, the data signal can be demodulated by taking the logical sum of the signal obtained by delaying the even data signal by 1/2 clock and the signal. FIG. 81 shows a block diagram of the signal reproducing circuit.

By performing four-value recording by the above method,
The recording linear density can be doubled as compared with the case where mark edge recording is performed using a normal binary recording medium. FIG. 82 shows a comparison between the mark edge recording of binary recording and the state of four-value recording when the same information is recorded with the same minimum recording domain size. As shown in this figure, according to the four-value recording of the present invention, the linear recording density can be doubled as compared with the mark edge recording of the binary recording.

<Nineteenth Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, the magnetic head (electromagnetic coil) is driven at a constant frequency which is the same as the detection window width T or an integral multiple thereof It is characterized in that the timing of laser irradiation is modulated while applying an external magnetic field to the recording medium. FIG. 83 is a block diagram of a laser irradiation timing modulation circuit applied to the multi-valued recording of this example, and FIG. 84 is a timing chart of signals handled by each part of the circuit. As the magneto-optical recording medium, the magneto-optical recording medium according to the fifth configuration example (the medium of FIG. 23.
Specifically, FIGS. 24 to 27, FIG. 29, FIG. 33, and FIG.
4, the medium of FIGS. 36 and 39, and the like. ) Was used.

In the multilevel recording method of this example, a recording laser pulse is irradiated once per cycle in synchronization with a change in the external magnetic field, and each recording layer is heated to a temperature at which the coercive force is sufficiently small. During cooling, either or both of the magnetization of the first recording layer and the magnetization of the second recording layer are selectively reversed. The state in which the magnetization is reversed is distinguished by shifting the timing of irradiation of the recording laser pulse. That is, as shown in FIG. 84, four pulse trains pal with timings shifted
se1, pulse2, pulse3, and pulse4 are generated, and a logical operation is performed with the signals of even-numbered bits and odd-numbered bits separated from the recording signal Data to generate recording laser drive pulses corresponding to each recording state.

FIG. 85 shows a block diagram of a signal reproducing circuit, and FIG. 86 shows a signal reproducing system. Similar to the case of the first example, the reproduction signal read from the magnetization domain train is sliced at three slice levels set to a predetermined value, and the three binarized signals sig1, sig2, and sig3 obtained thereby are used. The recorded signal can be reproduced by the procedure of.

<Twentieth Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, the magnetic head (electromagnetic coil) is driven at a constant frequency which is the same as the detection window width T or an integral multiple of the detection window width T. It is characterized in that the intensity of the applied laser is modulated while applying an external magnetic field to the recording medium. FIG. 87 shows a block diagram of a laser intensity modulation circuit applied to the multi-valued recording of this example, and FIG. 88 shows a timing chart of signals handled by each part of the circuit.

FIG. 89 shows a block diagram of a signal reproducing circuit, and FIG. 90 shows a signal reproducing system. Similar to the case of the second example, the reproduction signal read from the magnetization domain train is sliced at three slice levels set to a predetermined value, and the three binarized signals sig1, sig2, and sig3 obtained by the slice signal are sliced. The recorded signal can be reproduced by the procedure of.

<Twenty-first Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, while applying an external magnetic field whose applied magnetic field intensity is signal-modulated in multiple steps according to a recording signal to the magneto-optical recording medium,
A multi-valued signal is recorded on a magneto-optical recording medium by irradiating a desired recording track of the magneto-optical recording medium with a laser beam whose laser intensity is signal-modulated in multiple stages according to a recording signal. . As the magneto-optical recording medium, any of the magneto-optical recording media according to the first to sixth configuration examples can be applied.

Even when a specific signal is recorded on the magneto-optical recording medium having a specific magnetization characteristic, the applied magnetic field strength H
There are various possible combinations of the irradiation laser intensity P and the irradiation laser intensity P. For example, when recording the magnetic domain array of FIG. 91 (d) on the magneto-optical recording medium having the magnetization characteristic of FIG. 91 (a), the external magnetic field H is switched to four stages as shown in FIG. The external magnetic field intensity is set to H ₀ , H ₁ , H ₂ and H _{3 in} order from the lowest level, and the irradiation laser intensity P is switched to four levels as shown in FIG. from the _{P 2, P 3, P 0} , P 1 sequentially assigned to (H _0, P ₀₎ assigned to the combination of the signal "0", (H _1, P ₁₎ combining a signal of "1", ( The combination of H ₂ , P ₂ ) is assigned to the signal “2”, the combination of (H ₃ , P ₃ ) is assigned to the signal “3”,
Further, the applied magnetic field intensity H and the irradiation laser intensity P are shown in FIG.
When driven in the patterns of (b) and (c), FIG.
The magnetic domain sequence of can be recorded.

[0272] Also, by switching the four steps of an external magnetic field H as shown in FIG. 92 (b), -H ₁ from the external magnetic field strength of the lowest levels in the order, with a -H _0, H _0, H _1, As shown in FIG. 92 (c), the irradiation laser intensity P is switched in two steps, the low level irradiation laser intensity is P ₁ , the high level irradiation laser intensity is P _0, and (−H ₁ , P ₁ ) assign the combination to the signal _{"0", (- H 0} , P 0) assigned to the combination of the signal "1", assigned to the signal "2" combinations _{(H 0, P 0),} (H 1, P 1 ) Is assigned to the signal “3”,
Further, the applied magnetic field intensity H and the irradiation laser intensity P are shown in FIG.
Even if the pattern is driven by the patterns of (b) and (c), FIG.
As shown in, the same magnetic domain array as in FIG. 91 (d) can be recorded.

Further, as shown in FIG. 93 (b), the external magnetic field H is switched in two steps to reduce the low level external magnetic field strength to-.
H _0, while the external magnetic field strength of the high level H _0, switched to two stages irradiation laser intensity P as shown in FIG. 93 (c), irradiating the irradiation laser intensity of low level P _1, a high level the laser intensity and _{P 0, (- H 0,} P 1) assigns a combination of the signal _{"0", (- H 0} , P 0) assigned to the combination of the signal _{"1", (H 0,} P 0) To the signal “2”, and the combination of (H ₀ , P ₁ ) to the signal “3”,
Further, the applied magnetic field intensity H and the irradiation laser intensity P are shown in FIG.
Even if the pattern is driven by the patterns of (b) and (c), FIG.
As shown in, the same magnetic domain array as in FIG. 91D can be recorded.

<Twenty-second example of multi-value recording method> In the multi-value recording method of this example, the multi-value recording signal is not recorded in the magneto-optical recording medium in the signal order, but the multi-value recording signal is recorded in the magneto-optical recording medium. It is characterized in that it is divided into a plurality of combinations of magnetic fields and / or irradiation lasers for recording a specific magnetization state, and a signal is sequentially recorded for each combination. The variable of the magnetic field can be the magnitude of the magnetic field, the modulation amplitude range, the modulation frequency, or a combination thereof, and the variable of the irradiation laser can be the laser intensity, the modulation frequency, the pulse width, or a combination thereof. Can be used. The first magneto-optical recording medium
~ Any magneto-optical recording medium according to the sixth configuration example can be applied.

The multi-valued recording method of this example will be described taking the magneto-optical recording medium having the magnetization characteristics shown in FIG. 94 as an example.

FIG. 95 shows the first example,
First, in the first recording, the optical head is positioned on a desired track, and laser light having a constant intensity is irradiated under a magnetic field of H ₀ to bring the entire track into the state “0”. Then, the optical head is repositioned on the track on which the first recording is performed, and the laser beam is pulsed at the position corresponding to the data “1” under the magnetic field of H ₁ , and the state “0” is set. A recording magnetic domain in the state "1" is formed. In the third recording, the optical head is repositioned on the tracks where the first and second recordings have been performed, and the laser beam is pulsed at the position corresponding to the data “2” under the magnetic field of H _2. , Status "0",
A recording magnetic domain of state "2" is formed in "1". At this time, the signal is modulated in advance so that the recording magnetic domain in the state "2" is not formed on the recording magnetic domain in the state "1". Similarly, in the fourth recording, the optical head is repositioned on the track where the first to third recording is performed,
Under the magnetic field of H ₃ , the laser beam is pulsed at the position corresponding to the data “3” to form the recording magnetic domain of the state “3” in the states “0”, “1” and “2”. According to this method, it is not necessary to switch the external magnetic field at four values at high speed, and thus the load on the recording / reproducing apparatus can be reduced.

FIG. 96 shows a second example of signal recording of this system. The first recording is performed by positioning the optical head on a desired track and applying external magnetic fields H ₀ and H 2. _This is performed by pulse-irradiating the laser light at the positions corresponding to the data "0" and "1" while switching to the binary value of 1. Next, the optical head is repositioned on the track on which the first recording is performed, and the external magnetic field to be applied is switched to the binary value of H ₂ and H ₃ while the laser is moved to the position corresponding to the data “2” and “3”. It is performed by irradiating light with a pulse. This completes the four-value recording. According to this method,
It is not necessary to switch the external magnetic field at a high amplitude from H ₀ to H ₃ at a high speed, and it is sufficient to switch at a small amplitude of H _{0 to} H ₁ and H _{2 to} H ₃ , so that the load on the recording / reproducing apparatus is also light. Can be

In the previous example, recording was repeated for each track, but the same recording method can be applied for each zone or for the entire disc.

When H ₂ and H ₃ are equal to −H ₁ and −H ₀ , respectively, for example, a double coil head causes
A magnetic field corresponding to the modulation amplitude between _{0 and} H ₁ or between H _{2 and} H ₃ is generated, and on the other hand, a constant magnetic field of (H ₀ −H ₁ ) / 2 is generated as a bias, and the + and − are generated. By switching and superimposing, a modulating magnetic field corresponding to H _{0 to} H ₁ or H _{2 to} H ₃ can be applied.

<Twenty-third example of multi-value recording method> In the multi-value recording method of this example, a test signal for setting a slice level for discriminating signals is optically detected in order to accurately determine a multi-value signal level. It is characterized by recording on a magnetic recording medium. As the magneto-optical recording medium, one having the format shown in FIGS. 46 and 47 described above is used.

That is, the magneto-optical recording medium was driven in the same manner as in the first example of the multilevel recording method, and the optical head was positioned at the track having the desired address, and the magnetic head was positioned in the vicinity of the desired track. After that, while applying an external magnetic field from the magnetic head according to the recording data, a laser beam is emitted from the optical head to record a multilevel signal corresponding to the external magnetic field. At this time, a test signal for setting a slice level for discriminating the recorded multilevel signal is recorded in the test area 17 of FIG. 47, and the signal is reproduced,
Enabled to set slice level.

The data pattern of the test signal is shown in FIG.
As shown in 7, all of the multilevel signal levels are provided at least at one place. The signal length can be arbitrarily set as necessary, but in order to accurately determine a multilevel signal level, it is particularly preferable to make it longer than the spot diameter of the reproducing laser beam.

The "multilevel signal level" referred to here is a signal level defined by the magnetization state of each magnetic domain, for example, the states "0", "1" in FIG. 130 or 131,
The signal level defined by the relative signal output indicated by "2" and the total magnetization state of the magnetic domain pattern in which a plurality of minute magnetic domains are continuous, for example, the state ("0", "2" in FIG. 130 or 131). ), (“1”, “2”), (“0”,
Both of the relative signal outputs indicated by "1") are included. Also,
In the example of FIG. 130 or 131, the “signal length” refers to the length of the magnetic domain that reveals the magnetization states of “0”, “1”, and “2”. In the example,
("0", "2"), ("1", "2"), ("0",
"1") indicates the continuous length of the magnetic domain pattern that reveals the magnetization state. By making this longer than the spot diameter of the reproducing laser beam, the signal level before and after the level of the test signal for setting the slice level of each signal is set to a region where level shift due to optical interference does not occur. can do. Further, in consideration of the magnetic super-resolution type magneto-optical recording medium, it is more preferable that the signal of each level of the test signal has a region that does not cause a level shift due to optical interference with the preceding and following signal levels.

In reproducing the multi-valued recording signal, as shown in FIG. 98, when the test signal is reproduced, the multi-valued signal levels 1 to n are sampled and held respectively to sample the signal levels k and k + 1. Slice level for discriminating signal levels k and k + 1 from hold levels V _k and V _{k + 1}
(V _k + V _{k + 1} ) / 2 is generated.

The test signal can be recorded at the beginning of the data recording unit, or can be provided at regular intervals in the data recording unit. Further, the data recording unit may be the entire sector in the case of a medium having a sector structure, or an area sandwiched between signals for synchronizing clocks. Furthermore, it may be a block for data modulation / demodulation, or may be inserted for each arbitrary number of bytes.

<Twenty-fourth Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, a test signal for accurately determining the timing of detecting the edge of the multi-valued recording signal is recorded on the magneto-optical recording medium. It is characterized by Similarly, as the magneto-optical recording medium, one having the format shown in FIGS. 46 and 47 described above is used.

That is, after the magneto-optical recording medium is driven in the same manner as in the first example of the multilevel recording method, the optical head is positioned at the track having the desired address, and the magnetic head is positioned in the vicinity of the desired track. While applying an external magnetic field from the magnetic head according to the recording data, a laser beam is emitted from the optical head to record a multilevel signal corresponding to the external magnetic field. At this time, a test signal for generating the reference signal at the timing of reproducing the edge of the recorded multilevel signal is recorded in the test area 17 of FIG. 47, and the signal is reproduced to generate the reference timing of edge detection. I was able to do.

The data pattern of the test signal is shown in FIG.
As shown in FIG. 9, all edges between multilevel signal levels are provided at least at one place. The signal length is
Although it can be arbitrarily set as necessary, it is particularly preferable to make it longer than 1/2 of the spot diameter of the reproducing laser beam in order to prevent the optical phase shift of the length of each multilevel level. Further, when considering a magnetic super-resolution type magneto-optical recording medium, each edge signal of the test signal should have an edge interval longer than a length that does not cause level shift due to optical interference with the front and rear edge signals. It is more preferable to set.

Also in the case of this example, the "multilevel signal level" means a signal level defined by the magnetization state of each magnetic domain, for example, the states "0", "1" in FIG.
The signal level defined by the relative signal output indicated by "2" and the total magnetization state of the magnetic domain pattern in which a plurality of minute magnetic domains are continuous, for example, the state ("0", "2" in FIG. 130 or 131). ), (“1”, “2”), (“0”,
Both of the relative signal outputs indicated by "1") are included. Also,
In the example of FIG. 130 or 131, the “signal length” refers to the length of the magnetic domain that reveals the magnetization states of “0”, “1”, and “2”. In the example,
("0", "2"), ("1", "2"), ("0",
"1") indicates the continuous length of the magnetic domain pattern that reveals the magnetization state. By making this longer than ½ of the spot diameter of the reproducing laser beam, the signal at each edge of the test signal for generating the timing signal which is the reference of the timing for detecting the edge of the multi-valued recording signal is No edge shift occurs due to optical interference with the signal levels of the front and rear edges.

In reproducing the multilevel recording signal, each section edge is independently detected at the time of reproducing the test signal, and the reference timing of the edge detection signal is generated. At the time of reproducing the data signal, each section edge is independently detected, and as shown in FIG. 100, the edge detection timing of the test signal is used as a reference,
Each edge detection signal is combined.

Also in the case of this example, the test signal can be recorded at the head portion of the data recording unit, or can be provided at regular intervals in the data recording unit. Further, the data recording unit may be the entire sector in the case of a medium having a sector structure, or an area sandwiched between signals for synchronizing clocks. Furthermore, it may be a block for data modulation / demodulation, or may be inserted for each arbitrary number of bytes.

<Twenty-fifth Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, a test signal for setting a slice level for discriminating a signal is magneto-optically detected in order to accurately determine a multi-valued signal level. A recording signal is recorded on the recording medium, and a test signal for accurately determining the timing of detecting the edge of the multilevel recording signal is recorded on the magneto-optical recording medium. As the magneto-optical recording medium, the above-mentioned FIGS. 46 and 47 are used.
The one having the format shown in is used.

That is, the magneto-optical recording medium was driven in the same manner as in the first example of the multilevel recording method, and the optical head was positioned at the track having the desired address and the magnetic head was positioned in the vicinity of the desired track. After that, while applying an external magnetic field from the magnetic head according to the recording data, a laser beam is emitted from the optical head to record a multilevel signal corresponding to the external magnetic field. At this time, a test signal for setting a slice level for discriminating the recorded multilevel signal and a test signal for generating a reference signal of a timing for reproducing an edge of the recorded multilevel signal are provided in the test area 17 of FIG. By recording and reproducing the signal, the slice level can be set and the reference timing for edge detection can be generated.

The data pattern of each test signal and the reproducing method of the multi-valued recording signal are the same as those of the 23rd and 24th examples of the above-mentioned multi-valued recording method, and therefore the description thereof is omitted to avoid duplication. To do.

Also in the case of this example, the test signal can be recorded at the head portion of the data recording unit, or can be provided at regular intervals in the data recording unit. Further, the data recording unit may be the entire sector in the case of a medium having a sector structure, or an area sandwiched between signals for synchronizing clocks. Furthermore, it may be a block for data modulation / demodulation, or may be inserted for each arbitrary number of bytes.

<Twenty-sixth Example of Multi-Valued Recording Method> As one means for performing mark edge recording on a magneto-optical recording medium, as shown in FIG. 101, recording magnetic domains are formed at a constant cycle and recording is performed according to an information signal. The edge position of the magnetic domain was stepwise modulated in two or more steps within a range sufficiently smaller than the recording magnetic domain period. By combining this method with the magneto-optical recording medium for multilevel recording of the present invention, two-dimensional multilevel recording in the time direction (track direction) and the amplitude direction can be realized. It is more preferable that the recording magnetic domain formation period is set to a magnetic domain length and a magnetic domain interval that are equal to or longer than a length that does not cause edge shift due to optical interference between a signal at an arbitrary edge and signals at edges before and after it.

As a recording method, in the method of simultaneously modulating the recording laser beam and the external magnetic field for recording, the irradiation intensity of the recording laser beam, the irradiation time, the irradiation timing, the intensity of the external magnetic field applied to it, or switching of A method of modulating the timing or the like according to the recorded information is used.

FIG. 102 shows an example in which the irradiation pulse width of the recording laser beam is modulated stepwise according to the recording information signal. In magneto-optical modulation recording, the range heated to the recordable temperature of the magneto-optical recording medium is the magnetic domain according to the external magnetic field when the medium is cooled, so the edge position is set at the irradiation start timing of the recording laser beam. Heavily dependent. Therefore, as shown in FIG. 103, it is possible to modulate the irradiation timing stepwise according to the recording information signal with a constant pulse width. Furthermore, in order to prevent edge shift due to residual thermal history, as shown in FIG. 104, the leading edge of the light irradiation pulse is responded to by the recording information signal and the trailing edge is responded to by the next recording information signal. It may be modulated stepwise.

FIG. 105 shows an example in which the irradiation intensity of the recording laser beam is modulated stepwise according to the recording information signal. When the irradiation intensity of the recording laser beam is modulated,
Since the size of the recording magnetic domain, that is, the magnetization state and the length of the recording magnetic domain are modulated according to the light intensity, the edge position can be controlled as in the case of modulating the light irradiation timing. Further, it is not limited to the light intensity alone, and the light irradiation timing control and the light irradiation pulse width control can be used together.

FIG. 106 shows an example in which the edge position is controlled by modulating the strength of the external magnetic field. When the strength of the external magnetic field applied to the magneto-optical recording medium is changed,
Since the size of the recording magnetic domain changes, the edge position can be controlled as in the case of modulating the irradiation intensity of the recording laser beam and the like. Of course, it is also possible to use this together with light intensity control, light irradiation timing control, and light irradiation pulse width control.

FIG. 107 shows an example in which the edge position is controlled by modulating the application timing of the external magnetic field. In this case, since the edge position of the recording magnetic domain corresponds to the switching position of the applied magnetic field, the recording laser beam is
Not only pulses but also DC light may be used.

<Twenty-seventh Example of Multilevel Recording Method> In optical-magnetic field modulation recording, the basic magnetic domain shape is determined by the light intensity and the optical pulse width. As shown in FIG. 108, by simultaneously controlling the intensity of the recording laser beam and the recording pulse width, it is possible to change the recording magnetic domain width while keeping the recording magnetic domain length constant. That is, since each recording level can be minutely changed by this, multi-value recording can be realized by minutely modulating the level corresponding to the information signal. If the two-dimensional multi-value recording shown in the 25th example of the above-mentioned multi-value recording method is decoded, three parameters of the edge position of the recording magnetic domain, the level position corresponding to the magnetization state, and the level position corresponding to the width of the magnetic domain are obtained. It is possible to realize three-dimensional multi-valued recording by.

<Twenty-eighth Example of Multi-Valued Recording Method> The multi-valued recording method of this example is as follows:
It is characterized by using a sample servo system. As the magneto-optical recording medium, one having the format shown in FIG. 47 and FIG. 109 (a) described above is used.

As shown in FIGS. 47 and 109 (a),
In the magneto-optical recording medium of this example, the recording track 11 is divided into a large number of data recording units (segments) 12, and each data recording unit (segment) 12 has a servo area 1
4 and a data recording area 15 are provided. Further, a tracking pit 16 and an embedded pit 18 are provided in advance in the servo area 14.

FIG. 110 is a block diagram of a recording / reproducing apparatus suitable for such a magneto-optical recording medium of the sample servo system. A laser beam emitted from a laser forms a spot on a recording layer by a focusing lens. On the other hand, a magnetic coil (magnetic head) is arranged in the vicinity of the laser spot, and is configured so that a magnetic field whose intensity is modulated by a multilevel signal can be applied to the recording layer. The laser beam emitted from the laser is irradiated along the recording track 11, and tracking of the laser beam is performed by detecting the tracking pit 16 provided in the servo area 14. On the other hand, signal recording / reproduction is performed in the servo area 1
The PLL circuit generates a channel clock from the signal detected from the embedded pit 18 provided in No. 4, and this channel clock controls the laser drive circuit, the multilevel encoder, and the multilevel decoder.

Incidentally, in the magneto-optical disk, the DC level of the reproduced signal fluctuates generally due to the minute fluctuation of the birefringence of the substrate. On the other hand, the sample servo type magneto-optical disk has 1000 or more segments per track, and within this range, the DC level of the reproduction signal can be regarded as constant. Therefore, by providing an unrecorded area in which a signal is not recorded in a part of each segment, for example, in the test area 17, it is possible to correct the fluctuation of the DC level with reference to the reflectance of the unrecorded area. It is possible to easily identify the value recording signal. FIG. 111 shows an example of a DC level correction circuit applied to the recording / reproducing apparatus of FIG. The level clamp gate controls to hold the sample servo circuit (S / H circuit) at the time when the reproduction signal from the unrecorded area is detected.

<Twenty-Ninth Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, regardless of the temperature of the driving device, the environmental temperature, the variation in the performance of the driving device, the variation in the characteristics of the magneto-optical recording medium, etc. A test signal for controlling the multilevel recording signal amplitude (multilevel recording magnetic domain width) to be constant is recorded in a test area provided outside the user area of the magneto-optical recording medium, and the reproduced signal is compared with a reference signal. Then, the recording laser power and / or the recording laser pulse width is controlled. As the magneto-optical recording medium, one having the format shown in FIG. 48 and FIG. 49 described above is used.

First, the magneto-optical recording medium is mounted on the recording / reproducing apparatus, and the optical head is positioned at a desired address in the test area 22. Further, the magnetic head is positioned near the desired track. Then, the optical head and the magnetic head are driven to record a constant test pattern in the test area, which is a combination of multi-valued recording signals to be recorded on the magneto-optical recording medium. Then, the test signal is reproduced to compare the signal amplitude with the reference signal amplitude, and the recording temperature on the magneto-optical recording medium is controlled to be constant.

Recording of the test signal can be performed at an appropriate timing as needed after the magneto-optical recording medium is mounted in the recording / reproducing apparatus. For example, it can be performed when the magneto-optical recording medium is mounted in the recording / reproducing apparatus, or can be performed at the start of the operation of the recording / reproducing apparatus.
It can also be performed immediately before the signal recording operation on the magneto-optical recording medium. Furthermore, after mounting the magneto-optical recording medium on the recording / reproducing apparatus, it is possible to perform the recording at regular time intervals.

Recording of the test pattern is shown in FIG. 112 (a).
As shown in FIG. 5, the laser power is continuously or stepwise applied while applying an external magnetic field of a constant level in pulses so that a reproduction signal approximated between two adjacent signal levels of the multilevel recording signal can be obtained. Change to a single frequency.
In this example, for each multilevel recording level, the laser power was switched in eight steps of 0.1 mW each to record a test pattern. FIG. 112 (b) shows the reproduced signal waveform. Then, the minimum value and the maximum value of the signals are peak-held with respect to the reproduced signals of the respective recording powers, the signal amplitudes are obtained, and the difference between those signal amplitudes and the reference signal amplitude is the smallest, and the difference is The optimum recording condition is a condition that is less than a certain value. If the optimum recording condition cannot be found, the laser power is increased and the test recording is repeated. If the optimum recording condition is not found even if the maximum power of the recording / reproducing apparatus is exceeded, an error occurs and the operation ends.

FIG. 113 shows a block diagram of the optimum condition detecting circuit. The reference signal amplitude can be obtained from a signal previously recorded outside the user area and outside the test area on the medium. Further, it is also possible to read the data relating to the amplitude of the reference signal prerecorded on the medium and generate it by the recording / reproducing apparatus. Further, it is also possible to previously store the data regarding the reference signal amplitude in the memory provided in the recording / reproducing apparatus.

In the previous example, the test pattern was recorded by changing the laser power, but the test pattern can be recorded by changing the recording pulse width, and further, both the laser power and the recording pulse width can be recorded. It is also possible to change and record the test pattern.

<Thirtieth Example of Multi-Valued Recording Method> The multi-valued recording method according to the present example, regardless of the temperature of the driving device, the environmental temperature, the variation in the performance of the driving device, the variation in the characteristics of the magneto-optical recording medium, etc. A test signal for controlling the amplitude of the multilevel recording signal (width of the multilevel recording domain) to be constant is recorded in a test area provided outside the user area of the magneto-optical recording medium, and each multilevel recording level is read from the reproduced signal. It is characterized in that the external magnetic field for recording is controlled so that the amplitude between them becomes equal. As the magneto-optical recording medium, one having the format shown in FIG. 48 and FIG. 49 described above is used.

Similar to the 29th example, first, the magneto-optical recording medium was mounted in the recording / reproducing apparatus, and the optical head was set in the test area 22.
Position it at the desired address inside. Further, the magnetic head is positioned near the desired track. After that,
By driving the optical head and the magnetic head, a constant test pattern, which is a combination of the multilevel recording signals to be recorded on the magneto-optical recording medium, is recorded in the test area, and the signal amplitude between the levels of the multilevel recording signals is recorded. The external magnetic field is controlled so that is constant.

The recording of the test pattern is shown in FIG. 114 (a).
As shown in, the test pattern includes all of the multi-valued recording levels, and two multi-valued recording levels are used as a reference, and a test pattern for changing the external magnetic field of each of the other multi-valued recording levels is used. In this example, the test pattern was recorded by switching the external magnetic field in four steps for each multilevel recording signal level. FIG. 114 (b) shows the reproduced signal waveform. Then, the signal level is sampled and held for each reproduction signal of the recording magnetic field to obtain the signal amplitude. Also,
The obtained multi-level signal levels are compared with each other, and a combination of external magnetic fields that equalizes the signal level intervals is set as the optimum recording condition. FIG. 115 shows a block diagram of an optimum condition detection circuit suitable for the recording / reproducing method of this example.

The other points are the same as those of the recording / reproducing method of the 29th example, and therefore the description thereof will be omitted to avoid duplication.

<Thirty-First Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, in a magneto-optical recording / reproducing apparatus for performing magneto-optical field modulation recording, the temperature of the driving device, the environmental temperature, the variation of the driving device, the magneto-optical recording. In order to control the recording signal amplitude (multi-value recording magnetic domain width) of the multi-value recording signal to be constant regardless of the medium variation, at least one of the laser light power and the laser light pulse width is changed, and two or more kinds of light are changed. The test signal is recorded in a pulse cycle, and at least one of the recording laser power and the laser light pulse width is controlled so that the difference between the average values of the respective signal levels becomes a constant value. As an example of the magneto-optical recording medium, one having a format shown in FIGS. 48 and 49 is used.

Similar to the 29th and 30th examples of the multilevel recording method, first, the magneto-optical recording medium is mounted on the recording / reproducing apparatus, and the optical head is positioned at a desired address in the test area 22Note. Further, the magnetic head is positioned near the desired track. After that, the optical head and the magnetic head are driven, and the multi-valued recording signal to be recorded on the magneto-optical recording medium is recorded in the test area at two or more kinds of optical pulse periods with a laser light power and a laser light pulse width. Record while changing at least one of the above. Then, the test signal is reproduced to make the difference in the average value of the signal levels of the reproduced signals of the two or more types of cycles constant, thereby controlling the recording magnetic domain width of the magneto-optical recording medium to be constant. .

The test record is shown in FIG. 116 or 117.
As shown in FIG. 5, the recording laser light pulse period is two or more between the two levels having the largest amplitude of the multilevel recording signal.
At least one of the two recording laser light pulse periods
The seed period is set to a period in which the recording magnetic domains of the period do not overlap, and the at least one type of period is set to a period in which the recording magnetic domains of the period overlap. Recording is performed by gradually changing the recording laser power while applying a recording external magnetic field of constant strength while switching the polarity at the timing shown in FIG. 116 or FIG. 117. FIG. 118 shows the reproduced signal waveform of FIG. Further, FIG. 119 shows the reproduced signal waveform of FIG. 117. In both cases of FIG. 118 and FIG. 119, when the recording laser power is changed, a signal recorded in a period in which the recording magnetic domains do not overlap with an average value of signal levels of signals recorded in the period in which the recording magnetic domains overlap. The average value of the signal level changes greatly. The difference (Δ1) between the average values of the two cycles is detected for all the recording conditions changed stepwise, and the condition where the value of Δ1 is closest to the reference value is set as the optimum recording condition. At this time, when the preset reference value is 0, the variation in the magneto-optical recording medium and the DC of the circuit
Since it is unlikely to be affected by offset and drift, it is desirable that the period in which the recording magnetic domains do not overlap is set to be substantially equal to the effective light spot diameter so that the reference value becomes zero.

FIG. 120 shows an example of a block diagram of the optimum condition detecting circuit. The reproduced test signal is passed through a low-pass filter having a cutoff frequency sufficiently lower than the recording laser pulse period, and becomes an average value of the reproduced signal level in each recording laser pulse period. Moreover,
Δ1 can be detected by peak-holding the maximum value and the minimum value of the signal and taking the difference.

Since the other points are the same as those of the recording / reproducing method of the 29th example, description thereof will be omitted to avoid duplication.

<Thirty-Second Example of Multi-Valued Recording Method> In the multi-valued recording method of this example, the magneto-optical recording medium for multi-valued recording is determined from the number of magnetic field regions in a stable recording state possessed by the magneto-optical recording medium. Is also characterized by recording multilevel recording signals. As the magneto-optical recording medium, all the magneto-optical recording media according to the above-mentioned first configuration example to the seventh configuration example can be used, but here, the magneto-optical recording medium for four-value recording (fifth configuration example). The magneto-optical recording medium according to the present invention (specifically, the medium shown in FIGS. 23 to 27) will be used to describe 16-value recording.

First, the magneto-optical recording medium is mounted on a medium driving unit such as a turntable, the optical head is arranged on the transparent substrate side, and the magnetic head is arranged on the protective layer side. The medium drive unit is activated to drive the magneto-optical recording medium, the optical head and the magnetic head relatively at a predetermined linear velocity, and position the optical head and the magnetic head on a predetermined track. Then, while irradiating a laser beam of a constant intensity from the optical head along the predetermined recording track, a magnetic field applied with a pulse-like signal modulation with a desired recording signal is applied from the magnetic head to record a signal. .

In this case, as shown in FIG. 121, a four-valued recording signal (003122001203213311302)
30113203210) is divided into two from the beginning, so that (00) (31) (22) (00) (1
2) (03) (21) (33) (11) (30) (2
3) (01) (13) (20) (32) (10) signal sequence is converted into the first signal and the second signal of each set.
By taking out the th signal separately, (032
A first signal sequence (0102313201231),
It is divided into a second signal sequence (0120231310313020).

Then, when the laser beam reaches the head position of the desired recording track, the intensity of the laser beam emitted from the optical head is switched to the recording level P ₁ and the first signal sequence is sent from the magnetic head. A magnetic field H ₁ pulse-modulated is applied. As a result, FIG.
As shown in FIG. 1A, a wide first write signal sequence 201 is formed on the magneto-optical recording medium.

Then, the laser beam is repositioned to the head position of the recording track on which the first write signal train 201 is formed, and the intensity of the laser beam emitted from the optical head is set to the first write signal train 201. The level is changed to a rewritable level P ₂ (P ₁ > P ₂ ), and a magnetic field H ₂ pulse-modulated by the second signal train is applied from the magnetic head. As a result, as shown in FIG. 121A, in the central portion of the first write signal sequence 201,
A second write signal sequence 202 that is narrower than the width of the first write signal sequence 201 is formed. Note that the width of the second write signal sequence 202 is made smaller than the width of the first write signal sequence 201, and a part of the first write signal sequence 201 is divided into the second write signal sequence 201.
The writing signal sequence 202 can be rewritten by changing the spot size by using a plurality of laser beams having different wavelengths.

The recording signal can be reproduced by irradiating the reproducing laser beam 210 having a spot diameter D larger than the width of the first write signal train 201 along the recording track. That is, when the reproducing laser beam 210 having a spot diameter D larger than the width of the first write signal train 201 is irradiated along the recording track, as shown in FIG. 121B, the first and second signal trains are formed. Both signals are “3”
Area, the signal of the first signal string is “3”, the signal of the second signal string is “2”, and the signal of the first signal string is “3”
In the region where the signal of the second signal sequence is “1”, the region where the signal of the first signal sequence is “3” and the signal of the second signal sequence is “0”, and the signal of the first signal sequence Is “2” and the signal of the second signal sequence is “3”, and the signal of the first signal sequence is “2” and the second
Of the signal sequence of the signal sequence of "2", the region of the signal of the first signal sequence of "2" and the signal of the second signal sequence of "1",
The signal of the signal sequence of “2” and the signal of the second signal sequence is “0”
Area, the signal of the first signal string is "1", the signal of the second signal string is "3", and the signal of the first signal string is "1"
In the region where the signal of the second signal sequence is “2”, the region in which the signal of the first signal sequence is “1” and the signal of the second signal sequence is “1”, and the signal of the first signal sequence Is "1" and the signal of the second signal sequence is "0", the region of the signal of the first signal sequence is "0" and the signal of the second signal sequence is "3", A region where the signal of the signal train is “0” and the signal of the second signal train is “2”,
In the region where the signal of the first signal train is “0” and the signal of the second signal train is “1”, and in the region where both the signals of the first and second signal trains are “0”, the reproducing laser is used. Since the total magnetization state of the area irradiated with the spot 210 is different, a 16-value recording signal can be detected by assigning "0" to "15" to the total magnetization state of each area.

Thus, according to the recording / reproducing system of this example,
Since 16-value recording of a signal can be realized by using a 4-value recording medium, it is possible to provide a magneto-optical recording medium that is inexpensive and has a large amount of recorded information.

It is needless to say that similar 16-value recording can be executed by an optical modulation method instead of the magnetic field modulation method.

<Third Example of Multi-Valued Recording Method> The multi-valued recording method of this example is characterized in that 16-valued signals are recorded on a magneto-optical recording medium for 4-level recording by an optical-magnetic field modulation method. .

As in the case of the 32nd example, the magneto-optical recording medium is mounted on a medium driving unit such as a turntable, the optical head is arranged on the transparent substrate side, and the magnetic head is arranged on the protective layer side. The medium drive unit is activated to drive the magneto-optical recording medium, the optical head and the magnetic head relatively at a predetermined linear velocity, and position the optical head and the magnetic head on a predetermined track. Thereafter, as shown in FIG. 122, the optical head irradiates the laser beam whose intensity is modulated in a pulse shape along the predetermined recording track, while the magnetic head is pulse-modulated with a desired recording signal. A magnetic field is applied to record a signal.

The recording signal is divided into a first signal sequence and a second signal sequence by the same method as in the 31st example. Then, when the laser beam reaches the head position of the desired recording track, the laser beam emitted from the optical head is switched in pulse form and its intensity is switched to the recording level P ₁ . In addition, a magnetic field H ₁ pulse-modulated with the first signal train is applied from the magnetic head. As a result, as shown in FIG. 122A, a wide first write signal sequence 201 is formed on the magneto-optical recording medium. The pulsed recording laser beam is emitted at the timing when the external magnetic field applied from the magnetic head reaches the target value.

Then, the laser beam is repositioned to the head position of the recording track on which the first write signal sequence 201 is formed, the laser beam emitted from the optical head is switched in a pulse shape, and its intensity is set to the above-mentioned value. 1 write signal sequence 201 can be rewritten to a level P ₂ (P
Switch to ₁ > P ₂ ). Further, a magnetic field H ₂ pulse-modulated by the second signal train is applied from the magnetic head. As a result, as shown in FIG. 122 (a), the first
The second write signal sequence 202, which is narrower than the width of the first write signal sequence 201, in the center of the write signal sequence 201 of
To form. Also in this case, the pulsed recording laser beam is emitted at the timing when the external magnetic field applied from the magnetic head reaches the target value. In the recording / reproducing system of this example, the emission timing of the recording laser beam is shifted by the time t between the first recording and the second recording. By doing so, as shown in FIG. 123, the waveform of the reproduction signal detected in each region becomes sharper than in the case where the emission timings of the first and second recording laser beams are aligned. . Time t
Is adjusted so that the waveform of the reproduction signal becomes the sharpest.

The reproduction of the recording signal is performed by irradiating the reproducing laser beam 210 having a spot diameter D larger than the width of the first write signal sequence 201 along the recording track, as in the case of the 32nd example. You can do it. That is, when the reproducing laser beam 210 having a spot diameter D larger than the width of the first write signal train 201 is irradiated along the recording track, as shown in FIG. 122B, the first and second signal trains are formed. Area where both signals are “3”, the signal of the first signal row is “3” and the signal of the second signal row is “2”, and the signal of the first signal row is “3” A region where the signal of the second signal train is “1”, a region where the signal of the first signal train is “3” and a signal of the second signal train is “0”, and a signal of the first signal train is A region in which the signal of the second signal sequence is "3" in "2", a region in which the signal of the first signal sequence is "2" and the signal in the second signal sequence is "2", and the first signal A region where the signal of the column is “2” and the signal of the second signal sequence is “1”, and a region where the signal of the first signal sequence is “2” and the signal of the second signal sequence is “0” Signal of first signal sequence Is "1" and the signal of the second signal sequence is "3", the region of the signal of the first signal sequence is "1" and the signal of the second signal sequence is "2", A region where the signal of the signal sequence is “1” and the signal of the second signal sequence is “1”, and a region where the signal of the first signal sequence is “1” and the signal of the second signal sequence is “0” , A region where the signal of the first signal sequence is “0” and the signal of the second signal sequence is “3”, and a region where the signal of the first signal sequence is “0” is the second
Of the signal sequence of the signal sequence of “2”, the signal of the first signal sequence of “0” and the region of the signal of the second signal sequence of “1”, and the first
Since the total magnetization state of the region irradiated with the reproducing laser spot 210 is different between the region where the signals of the second signal train are both “0”, the total magnetization state of each region is “0”. By assigning "-" 15 ", a 16-value recording signal can be detected.

According to this embodiment, the same effect as the 32nd example is obtained, and the pulsed recording laser beam is irradiated at the timing when the external magnetic field applied by the magnetic head reaches the target value. As a result, the edges of each magnetization domain are sharpened, and the margin for jitter can be increased. Also, during the first recording and the second
Since the emission timing of the recording laser beam is shifted during the second recording, a reproduction signal sharper than each region can be obtained as compared with the case where the emission timings of the first and second recording laser beams are aligned. it can. Therefore, these effects enable pit edge recording.

The recording signal is divided into three signal trains,
If these three signal trains are overwritten on the same track, 64-value signal recording can be performed according to the same principle.

<Thirty-fourth Example of Multi-Valued Recording Method> According to the multi-valued recording method of this example, a signal is recorded / reproduced on / from a magneto-optical recording medium having minute prepits formed at minute intervals along a recording track. It is characterized by doing. The following may be considered as the configuration and usage of this magneto-optical recording medium.

A. A magneto-optical recording layer is formed on a substrate having a pre-pit group divided into data units in an information recording area, and a magneto-optical signal is recorded in the pre-pits or between the pre-pits.

B. The a. A recording film capable of multilevel recording is laminated on the medium.

C. The a. The pre-pit group of is regularly arranged for each track. They are arranged in a straight line in the radial direction or are shifted by 1/2 cycle. This allows the quantization of crosstalk.

D. The a. In the medium, the composition and thickness of the film can be changed inside and outside the prepit.

E. The a. The pre-pit of the medium is formed to be smaller than the reproduction light spot diameter, and a magnetic super-resolution recording film is laminated thereon.

F. In addition, the a. ~ E. The above-mentioned various multilevel recording methods are applied to the medium.

In the magneto-optical recording medium, improvement of recording density is one of the most important technical problems. The recording density can be improved by reducing the recording magnetic domain and packing the signal in the track direction for recording. However, if the recording magnetic domains are miniaturized, signals reproduced from adjacent magnetic domains are likely to interfere with each other and cannot be separated.

When minute prepits are formed along the recording track at minute intervals, when the reproducing laser beam is irradiated along the recording track, the reflected light signal and the prepit from the portion where the prepit is present due to light diffraction or interference. Since there is a change in the reflected light signal from the portion where there is no mark, the presence or absence of the prepit can be detected by detecting the reflected light signal (so-called sum signal). On the other hand, the magneto-optical signal (so-called difference signal) recorded on the magnetic film can be detected by detecting the magnetization direction of the recording magnetic domain regardless of the presence or absence of prepits. Therefore, if the recording magnetic domain is formed in a positional relationship with the pre-pits, the position of the recording magnetic domain can be clarified even if the recording magnetic domain is miniaturized, the signal can be easily separated, and the recording density can be improved. .

FIG. 124 shows the case where the recording magnetic domain 302 is formed on the pre-pit 301. In the case of this example, since the sum signal and the difference signal have a one-to-one correspondence, the recording magnetic domain 302 can be detected by detecting the peak of the sum signal.

FIG. 125A shows the recording magnetic domain 30 such that the leading edge of the recording magnetic domain 302 overlaps the pre-pit 301.
FIG. 125B shows a case where a plurality of (three in this example) recording magnetic domains 302 are formed between adjacent prepits 301. In addition, FIG.
(C) shows the array center of the pre-pits 301 and the recording magnetic domain 30.
FIG. 125 (d) shows a case where the array center of 2 is shifted.
Shows the case where the array center of the pre-pits 301 and the array center of the recording magnetic domains 302 are displaced, and a plurality of (three in this example) recording magnetic domains 302 are formed between adjacent pre-pits 301.

FIG. 126 (a) shows a case where the pre-pits 301 are formed in a convex shape, and FIG. 126 (b) shows a case where the pre-pits 301 are formed in an elliptical shape. In addition, FIG.
6 (c) shows two convex pre-pits 301a and 301
FIG. 126 (d) shows a case where one recording magnetic domain 302 is formed on b, and two concave pre-pits 301a, 3a are shown in FIG.
The case where one recording magnetic domain 302 is formed on 01b is shown.

FIG. 127 shows a case where the pre-pits 301 are formed not only in the track direction but also in the inter-track direction with regularity. In this way, if the positional relationship between the pre-pits on the adjacent tracks is made regular and the recording magnetic domains are formed by using this as a guide, the leakage of the recording signal from the adjacent tracks, that is, the so-called crosstalk level, is quantized by the recording pattern. It can be an embodied level.

FIG. 128 shows a state in which the reproducing laser spot 210 is scanned so that the center of the reproducing laser spot 210 passes through the center track. This way,
The reproduction signal level is output as a multilevel signal separated into six levels depending on the combination with the recording patterns of the tracks on both sides. The original signal is reproduced by canceling the leaked signal due to the mutual relationship of the reproduced signals so that the center of the reproducing laser spot 210 passes through the center of each track. In this case, it is reproduced as a multi-valued record once,
The separation into stages facilitates crosstalk cancellation.

According to the recording / reproducing method of this example, a plurality of recording pits are present in the reproducing light spot in the laser traveling direction or the cross track direction, and the respective levels of the reproducing signal produced by the respective combinations of the recording states are different. It is a defined multi-stage recording / reproducing system, and is used not only for a magneto-optical recording medium for multi-level recording, but also for a normal magneto-optical recording medium for binary recording or a magnetic super-resolution type magneto-optical recording medium. It can also be applied to the recording and reproduction of previously used signals.

The other multi-value recording methods of the present invention will be listed below.

By adjusting the refractive index and film thickness of each film laminated on the transparent substrate, and the Kerr rotation angle of the perpendicular magnetization film, the relative signal output intervals corresponding to each recording state are made equal. For example, in the case of a ternary recording medium, as shown in FIG. 129, the level intervals of the recording signals corresponding to the states “0”, “1” and “2” are made equal. By doing so, the S / N ratio of the reproduction signal with respect to the transition of each level interval of the recording signal becomes uniform, and the signal efficiency is improved overall.
This method is used when the size of the minimum recording magnetic domain is relatively larger than the spot diameter of the reproducing light, for example, 1 / the spot diameter.
It is particularly effective when it is 2 or more.

When the size of the minimum recording magnetic domain is smaller than the spot diameter of the reproducing light, particularly when recording is performed with a size of 1/2 or less of the spot diameter, the signal level generated by the inter-waveform interference of the minute magnetic domains. And the signal level generated from the large magnetic domain in each recording state is made different.

When the size of the minimum recording magnetic domain is relatively small with respect to the spot diameter of the reproducing light, for example, 1/2 or less of the spot diameter, if this continues, the waveform interference of the reproduced signal causes interference. The signal output takes an intermediate value between the two states. For example, when the minute recording magnetic domains of the same size in the state "0" and the state "2" are repeatedly recorded on the multi-valued recording medium of the present invention, as shown in FIG. It becomes the same level as the reproduction signal of the magnetic domain which is relatively large with respect to the diameter, and it becomes impossible to distinguish between the two.

Therefore, if the signal level generated by the interference between the waveforms of the minute magnetic domains is made different from the signal level generated by the large magnetic domain in each recording state, the state "0", the state "1", the state "2", In addition, the inter-waveform interference level between the states "0" and "1", the inter-waveform interference level between the states "0" and "2", and the inter-waveform interference level between the states "1" and "2" By assigning signals to the inter-waveform interference levels, higher-order multilevel recording becomes possible.

The signal levels are set so as not to coincide with each other, and preferably at equal intervals. As the method, there are a method using a medium and a method using a recording method. As a method of using the medium, as shown in FIG. 131, each film is arranged so that the signal level generated from the large magnetic domain in each recording state is located at a signal level different from the signal level generated due to the inter-waveform interference of the minute magnetic domains. There is a method of setting the multiple interference condition of. In addition, as a method of performing the recording method, as shown in FIG. 132, the signal level generated by the inter-waveform interference of the minute magnetic domain is located at a position different from the signal level generated by the large magnetic domain in each recording state. There is a method of controlling the area ratio of recording magnetic domains. Specifically, when the medium is inserted into the recording / reproducing apparatus, the apparatus changes the area ratio of the minute recording magnetic domain and tries recording, and the signal levels generated from the large magnetic domains in each recording state are mutually matched. Instead, it is possible to adopt a method of selecting the area ratios that are preferably equally spaced. Further, the method performed using these media and the method performed using the recording method can be used in combination. According to this combined system, the adjustment of each signal level becomes easier and the signal level intervals can be made equal. Also, the signal level can be adjusted to an arbitrary position by controlling the area ratio of the recording magnetic domains.

A mark edge recording method for a multi-value recording medium and a signal reproducing method from a medium on which mark edge recording is performed by the method. FIG. 133 shows a mark edge recording method in which ternary information is carried on the end (mark edge) of the recording magnetic domain, and a signal reproducing method from a multi-valued recording medium on which mark edge recording is performed by the method. As the magneto-optical recording medium, for example, the magneto-optical recording medium of the first configuration example (see FIGS.
As in 6), a magneto-optical recording medium capable of recording ternary information in the magnetic layer is used.

First, a mark edge recording method for the magneto-optical recording medium will be described. 3 for magneto-optical recording media
To record the value information “0”, “1”, “2”,
It is necessary to switch the magnetization state of the magnetic layer (in the case where there are a plurality of magnetic layers, the total magnetization state of the magnetization states of each magnetic layer) in three steps. The three-stage magnetization states are A, B, and C (however, the magnitude of magnetization increases in the order of A <B <C), and as shown in FIG. Information of “0” is assigned to a portion where A is continuous, a portion where the magnetization state B of the oblique line is switched to the magnetization state A of the white background, and a portion where the magnetization state C of the lattice is switched to the magnetization state A of the white background, and the magnetization state A of the white background is changed. Information of “1” is assigned to a portion where the magnetization state B of the diagonal line is switched, a portion where the magnetization state B of the diagonal line is continuous, and a portion where the magnetization state C of the lattice is switched to the magnetization state B of the diagonal line, and the magnetization state A of the white background is changed to the lattice state. A portion that switches to the magnetization state C, a portion that switches from the hatched magnetization state B to the lattice magnetization state C,
When information is recorded by assigning “2” information to the portion where the magnetization state C of the lattice is continuous, for example, ternary information (1020
2201210) can be recorded by the mark train shown in FIG. 133 (a).

Next, a method of reproducing a signal from a medium in which ternary information is mark edge recorded by the above method will be described. When reproducing light is radiated along the mark row in FIG. 133A, the size of the magnetization in each recording magnetic domain is corresponding to that in FIG.
The reproduced signal waveform of 3 (b) is obtained. When the reproduction signal output detected from the A recording magnetic domain is α, the reproduction signal output detected from the B recording magnetic domain is β, and the reproduction signal output detected from the C recording magnetic domain is γ, α <s ₂ < Two different slice levels s ₁ and s satisfying the condition β <s ₁ <γ
_{At 2} , slice the reproduced signal waveform of FIG. 133 (b),
The cross points between the slice levels s ₁ and s ₂ and the reproduced signal output are detected. In the middle column of FIG. 133 (b), the presence / absence of a signal detected at each slice level s ₁ , s ₂ is indicated by a symbol “◯”.
It is also shown by "-". The upper column of this column shows the detection pattern of the signal detected at the slice level s ₁ , and the lower row shows the detection pattern of the signal detected at the slice level s ₂ . In these descriptions, the symbol "○" represents the case where the cross point was detected, and the symbol "-" represents the case where the cross point was not detected.

As is clear from this figure, in the case of this example, the detection signal of the slice level s ₁ and the slice level s
_In the combination with the detection signal of _2, the detection signal of the slice level s ₁ is “−” and the detection signal of the slice level s ₂ is “◯”.
(Hereinafter, this combination will be referred to as “−, ◯”. Similarly, the detection signal of the slice level s ₁ will be described earlier in “” and the cross point of the slice level s ₂ will be described later.)
, "○,-", "○, ○", "-,
There are four types of "-".

Therefore, as shown in FIG. 133 (d), the previous data of each signal detection unit is stored and the
When the previous data is "○, ○" and the detection signal is "-,-", the previous data is "-, ○" and the detection signal is "○,
In the case of "-", if the previous data is "-,-" and the detection signal is "○, ○", "2" of the reproduction data is assigned and the previous data is "○, ○". When the detection signal is "○,-", the previous data is "-, ○" and the detection signal is "-,-", the previous data is "-,-" Is “-, ◯”, the reproduction data “1” is assigned. Further, when the previous data is “○, ◯” and the detection signal is “○, ◯”, the previous data is Is "-, ○" and the detection signal is "-, ○", the previous data is "-,-" and the detection signal is "-,-".
In this case, by assigning “0” of the reproduction data, the original ternary information (10202201210) can be reproduced as shown in the bottom column of FIG. 133 (b).

In FIG. 133, the mark edge recording / reproducing method in the case of using the magneto-optical recording medium for ternary recording has been described as an example, but the magneto-optical recording medium for binary recording or quaternary recording or more is used. When the magneto-optical recording medium for multilevel recording is used, the mark edge recording / reproducing of information can be performed in the same manner as described above.

In the example of FIG. 133, the portion where the magnetization state A of the white background is continuous, the portion where the magnetization state B of the oblique line is switched to the magnetization state A of the white background, and the magnetization state C of the lattice is switched to the magnetization state A of the white background. Information of “0” is assigned to a part, and a part where the magnetization state A of the white background is switched to the magnetization state B of the oblique line, a part where the magnetization state B of the oblique line is continuous, and a part where the magnetization state C of the lattice is switched to the magnetization state B of the oblique line. Information "1" is assigned, and "2" is assigned to a portion where the magnetization state A of the white background is switched to the magnetization state C of the lattice, a portion where the magnetization state B of the oblique line is switched to the magnetization state C of the lattice, and a portion where the magnetization state C of the lattice is continuous. Although the information is recorded by allocating the information of "", what information is allocated to which change of the magnetization state can be appropriately changed as necessary regardless of the present embodiment.

An example of the structure of a magnetic head device applicable to multilevel recording on a magneto-optical recording medium is shown below.

<First Structural Example of Magnetic Head Device> As shown in FIG. 134, the magnetic head device of this example is formed by winding two windings around one magnetic circuit, and these windings are independent of each other. It is characterized in that it can be driven to. This magnetic head device is arranged on the protective film side of the magneto-optical recording medium.

The magnetic head device of this example can be applied to the first, third to eighth examples, the eighteenth example, the twenty-first example and the twenty-second example of the multilevel recording method. That is, when these multi-value recording methods are executed, the magnetic head drive circuit 1 and the magnetic head drive circuit 2 that apply current to the two windings are independently driven in synchronization with the recording clock, thereby performing magneto-optical recording. Since a multi-valued external magnetic field can be applied to the medium, at the same time, by irradiating an optical pulse synchronized with the recording clock,
The signal can be multi-valued recorded in the irradiation portion of the light pulse.

Further, the magnetic head device of this example is the tenth example, the eleventh example, the thirteenth example, the fifteenth example to the first example of the multilevel recording method.
It can be applied to the 7th example, the 19th example, and the 20th example. That is, one winding and the magnetic head drive circuit form a resonance circuit,
By generating a constant frequency magnetic field in synchronization with the recording clock and applying a constant current to the other winding to generate a constant bias magnetic field, a magnetic field of a constant cycle offset from the magnetic field zero is generated. Can be applied to.

Furthermore, the magnetic head device of this example can be applied to the ninth example and the fourteenth example of the multilevel recording method. That is,
By forming a resonance circuit with one winding and the magnetic head drive circuit to generate a magnetic field having a constant frequency in synchronization with the recording clock, and driving the other winding in synchronization with the recording clock, The changed magnetic field having a constant period can be applied to the magneto-optical recording medium.

In the above configuration example, the number of windings is 2
Although the case has been described as an example, the same configuration can be made when the number of windings is three or more.

<Second Configuration Example of Magnetic Head Device> The magnetic head device of this example is characterized in that, as shown in FIG. 135, two magnetic heads that can be driven independently of each other are arranged close to each other. And This magnetic head device is also arranged on the protective film side of the magneto-optical recording medium.

The magnetic head device of this example can be applied to the first example, the third to eighth examples, the eighteenth example, the twenty-first example, and the twenty-second example of the multilevel recording method. That is, when these multilevel recording methods are executed, the multilevel external magnetic field can be applied to the magneto-optical recording medium by independently driving the magnetic head 1 and the magnetic head 2 in synchronization with the recording clock. Therefore, at the same time, by irradiating the light pulse synchronized with the recording clock, the signal can be multivalued recorded in the irradiation portion of the light pulse.

Further, the magnetic head device of this example is the tenth example, the eleventh example, the thirteenth example, the fifteenth example to the first example of the multilevel recording method.
It can be applied to the 7th example, the 19th example, and the 20th example. That is, one magnetic head and a magnetic head drive circuit form a resonance circuit to generate a magnetic field having a constant frequency in synchronization with the recording clock, while applying a constant current to the other magnetic head to generate a constant bias magnetic field. By generating the magnetic field, a magnetic field having a constant cycle offset from the zero magnetic field can be applied to the magneto-optical recording medium.

Furthermore, the magnetic head device of this example can be applied to the ninth and fourteenth examples of the multilevel recording method. That is,
One magnetic head and a magnetic head drive circuit form a resonance circuit to generate a magnetic field having a constant frequency in synchronization with the recording clock, and the other magnetic head is driven in synchronization with the recording clock to reduce the magnetic field strength. The changed magnetic field having a constant period can be applied to the magneto-optical recording medium.

<Third Configuration Example of Magnetic Head Device> In the magnetic head device of this example, as shown in FIG. 136, two magnetic heads are arranged close to each other and close to these two magnetic heads. It is characterized in that a permanent magnet for applying a bias magnetic field is arranged. The two magnetic heads are configured so that they can be driven independently of each other. The magnetic head device of this example is also arranged on the protective film side of the magneto-optical recording medium.

The magnetic head device of this example can be applied to the first, third to eighth examples, the eighteenth example, the twenty-first example, and the twenty-second example of the multilevel recording method. That is, when these multilevel recording methods are executed, the multilevel external magnetic field can be applied to the magneto-optical recording medium by independently driving the magnetic head 1 and the magnetic head 2 in synchronization with the recording clock. it can. Moreover, a constant bias magnetic field can be applied to the magneto-optical recording medium by the permanent magnet. Therefore, by irradiating the optical pulse synchronized with the recording clock at the same time as the application of the magnetic field, it is possible to perform multi-level signal recording on the irradiation portion of the optical pulse.

Further, the magnetic head device of this example is the tenth example, the eleventh example, the thirteenth example, the fifteenth example to the first example of the multilevel recording method.
It can be applied to the 7th example, the 19th example, and the 20th example. That is, the magnetic head and the magnetic head drive circuit form a resonance circuit,
By generating a magnetic field having a constant frequency in synchronization with the recording clock and applying a constant bias magnetic field with a permanent magnet, it is possible to apply a magnetic field having a constant cycle offset from the magnetic field zero to the magneto-optical recording medium.

Furthermore, the magnetic head device of this example can be applied to the ninth and fourteenth examples of the multilevel recording method. That is,
One magnetic head and a magnetic head drive circuit form a resonance circuit to generate a magnetic field having a constant frequency in synchronization with the recording clock, and the other magnetic head is driven in synchronization with the recording clock to reduce the magnetic field strength. The changed magnetic field having a constant period can be applied to the magneto-optical recording medium. In this case, since a constant bias magnetic field is applied by the permanent magnet, it is possible to apply a magnetic field of a constant cycle offset from the magnetic field zero to the magneto-optical recording medium.

Since the magnetic head device of this embodiment is provided with the permanent magnet for applying the bias magnetic field, it is not necessary to apply a direct current to the magnetic head. Therefore, it is possible to reduce power consumption and increase the signal transmission rate.

<Fourth Configuration Example of Magnetic Head Device> In the magnetic head device of this example, as shown in FIG. 137, two magnetic heads are arranged close to each other on the protective film side of the magneto-optical recording medium, and It is characterized in that a leakage magnetic field from the focusing lens actuator is used as the bias magnetic field. The other points are the same as those of the magnetic head device according to the third configuration example, and thus the description thereof is omitted.

<Fifth Configuration Example of Magnetic Head Device> In the magnetic head device of this example, as shown in FIG. 138, one magnetic head and a permanent magnet for applying a bias magnetic field are placed close to each other to form a magneto-optical recording medium. It is characterized in that it is arranged on the protective film side.

<Sixth Configuration Example of Magnetic Head Device> In the magnetic head device of this example, as shown in FIG. 139, one magnetic head is arranged on the protective film side of the magneto-optical recording medium, and a bias magnetic field is applied. It is characterized in that the leakage magnetic field from the narrowing lens actuator is used.

<Seventh Configuration Example of Magnetic Head Device> In the magnetic head device of this example, as shown in FIG. 140, two magnetic heads are arranged close to each other and close to these two magnetic heads. It is characterized in that an electromagnetic coil for applying a bias magnetic field is arranged. The magnetic head device of this example also
It is arranged on the protective film side of the magneto-optical recording medium.

<Eighth Configuration Example of Magnetic Head Device> In the magnetic head device of this example, as shown in FIG. 141, two magnetic heads are arranged close to each other on the protective film side of the magneto-optical recording medium, and It is characterized in that an electromagnetic coil for applying a bias magnetic field is arranged around the narrowed lens actuator. The magnetic head device of this example is also arranged on the protective film side of the magneto-optical recording medium.

The above embodiments are merely examples of the present invention, and in addition, by combining an arbitrary medium, an arbitrary recording / reproducing system and a recording / reproducing apparatus according to the present invention, Various signal recordings can be performed.
In particular, the magnetic head device is not limited to the description of the above configuration example, but the number of windings of the magnetic head, the number and arrangement of the magnetic heads, and the number of permanent magnets or electromagnetic coils that are means for applying a bias magnetic field. The arrangement and the like can be appropriately changed and used.

In the above embodiment, for ease of explanation, the film structure of the magneto-optical recording medium, its format, the multilevel recording / reproducing method, and the magnetic head device will be described separately. Only the typical combinations are selectively described. Therefore, the gist of the present invention is:
It is not limited to the combinations listed in the above embodiment,
Multi-valued recording of information can be performed by combining any of the magneto-optical recording media, the multi-valued recording / reproducing method and the magnetic head device described in the above embodiment.

In addition, the magneto-optical recording medium, the recording / reproducing system, and the magnetic head device described in the above embodiments can be changed as needed without departing from the features of the present invention. For example, a recording / reproducing method such as recording / reproducing information using a recording / reproducing apparatus including a magneto-optical head having a plurality of recording / reproducing laser light irradiation units can be adopted.

[0388]

As described above, according to the present invention,
Higher density signal recording can be realized with a simpler film laminated structure. Further, in the magneto-optical recording medium of the present invention, each recording state is extremely stable against the fluctuation of the external magnetic field, and the magnetic characteristics of each recording layer, the laser beam intensity at the time of recording / reproducing, and the external magnetic field intensity are subtly matched. Since it is not necessary, a magneto-optical recording / reproducing system excellent in stability, mass productivity and practicality can be constructed.

[Brief description of drawings]

FIG. 1 is a graph illustrating the characteristics of a magneto-optical recording medium according to the present invention.

FIG. 2 is an explanatory diagram showing the principle of a multilevel recording method according to the present invention.

FIG. 3 is an explanatory diagram illustrating the relationship between the film configuration and the magnetization characteristics of the magneto-optical recording medium according to the present invention.

FIG. 4 is an explanatory diagram illustrating the relationship between the film configuration and the magnetization characteristics of the magneto-optical recording medium according to the present invention.

FIG. 5 is an explanatory diagram illustrating the relationship between the film configuration and the magnetization characteristics of the magneto-optical recording medium according to the present invention.

FIG. 6 is an explanatory diagram illustrating the relationship between the film configuration and the magnetization characteristics of the magneto-optical recording medium according to the present invention.

FIG. 7 is an explanatory diagram illustrating the relationship between the film configuration and the magnetization characteristics of the magneto-optical recording medium according to the present invention.

FIG. 8 is an explanatory diagram illustrating the relationship between the film configuration and the magnetization characteristics of the magneto-optical recording medium according to the present invention.

FIG. 9 is an explanatory diagram of a magneto-optical recording medium according to a first configuration example.

FIG. 10 is a diagram showing film configurations and external magnetic field-relative signal output characteristics of various magneto-optical recording media belonging to the first configuration example.

FIG. 11 is a main-portion cross-sectional view schematically showing the magneto-optical recording medium according to the first example.

FIG. 12 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to a second example.

FIG. 13 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to the third embodiment.

FIG. 14 is a cross-sectional view of a main part schematically showing a magneto-optical recording medium according to a fourth example.

FIG. 15 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to a fifth example.

FIG. 16 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to a sixth embodiment.

FIG. 17 is an explanatory diagram of a magneto-optical recording medium according to a second configuration example.

FIG. 18 is a cross-sectional view of a main part schematically showing a magneto-optical recording medium according to a seventh example.

FIG. 19 is an explanatory diagram of a magneto-optical recording medium according to a third configuration example.

FIG. 20 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to an eighth example.

FIG. 21 is an explanatory diagram of a magneto-optical recording medium according to a fourth configuration example.

FIG. 22 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to Example 9.

FIG. 23 is an explanatory diagram of a magneto-optical recording medium according to a fifth configuration example.

FIG. 24 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to a tenth embodiment.

FIG. 25 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to an eleventh embodiment.

FIG. 26 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to the twelfth embodiment.

FIG. 27 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to the thirteenth embodiment.

FIG. 28 is a graph showing the relationship between the film thickness of the Co film and the perpendicular magnetic anisotropy energy of the magneto-optical recording medium according to the sixth configuration example.

FIG. 29 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to a fourteenth embodiment.

FIG. 30 is a graph showing the effect of the magneto-optical recording medium according to the fourteenth example.

FIG. 31 is a graph showing the relationship between the type and thickness of the auxiliary magnetic film of the magneto-optical recording medium of the fourteenth example, and the magnitude of the minimum required recording magnetic field.

FIG. 32 is a graph showing the relationship between the type and thickness of the auxiliary magnetic film of the magneto-optical recording medium of the fourteenth example, and the required minimum recording magnetic field.

FIG. 33 is a sectional view of a key portion, schematically showing a magneto-optical recording medium according to a fifteenth embodiment.

FIG. 34 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to the sixteenth embodiment.

FIG. 35 is a graph showing reproduction signal output characteristics of the magneto-optical recording medium according to the sixteenth example.

FIG. 36 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to the seventeenth embodiment.

FIG. 37 is a CoC of the magneto-optical recording medium according to Example 17.
It is a graph which shows the film thickness of the Cu film | membrane which comprises u multilayer film, and the relationship of a magnetoresistive effect.

FIG. 38 is a graph showing reproduction signal output characteristics of the magneto-optical recording medium according to the seventeenth example.

FIG. 39 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to the eighteenth embodiment.

FIG. 40 is a main-portion cross-sectional view schematically showing a magneto-optical recording medium according to the seventh configuration example.

FIG. 41 is an explanatory diagram showing a first example of a magnetic super resolution reproducing system using the magneto-optical recording medium according to the seventh configuration example.

FIG. 42 is an explanatory diagram showing a second example of the magnetic super-resolution reproduction system using the magneto-optical recording medium according to the seventh configuration example.

FIG. 43 is an explanatory diagram showing a third example of the magnetic super-resolution reproduction system using the magneto-optical recording medium according to the seventh configuration example.

FIG. 44 is an explanatory diagram showing a fourth example of the magnetic super-resolution reproducing system using the magneto-optical recording medium according to the seventh configuration example.

45 is a table showing a film structure of each magneto-optical recording medium included in the seventh configuration example. FIG.

FIG. 46 is an explanatory diagram of a preformat pattern formed on a magneto-optical recording medium of sample servo system.

FIG. 47 is an explanatory diagram of a servo area in FIG. 46.

FIG. 48 is a diagram showing an embodiment of a test area provided on a CAV type optical disc.

FIG. 49 is an example diagram of a test area provided on a ZCAV type optical disc.

FIG. 50 is an explanatory diagram showing a first example of a multilevel recording / reproducing system according to the present invention.

FIG. 51 is an explanatory diagram showing a second example of the multilevel recording / reproducing system according to the present invention.

52 is an explanatory diagram showing a third example of the multilevel recording / reproducing system according to the present invention. FIG.

[Fig. 53] Fig. 53 is a configuration diagram of a multilevel recording / reproducing apparatus which executes a multilevel recording / reproducing system according to a third example.

FIG. 54 is a circuit diagram showing an example of an external magnetic field application circuit.

FIG. 55 is an explanatory diagram showing a fourth example of the multilevel recording / reproducing system according to the present invention.

[Fig. 56] Fig. 56 is a configuration diagram of a multilevel recording / reproducing apparatus which executes a multilevel recording / reproducing system according to a fourth example.

FIG. 57 is an explanatory diagram showing a fifth example of the multilevel recording / reproducing system according to the present invention.

[Fig. 58] Fig. 58 is a configuration diagram of a multilevel recording / reproducing apparatus which executes a multilevel recording / reproducing system according to a fifth example.

[Fig. 59] Fig. 59 is a configuration diagram showing another example of a multi-valued recording / reproducing apparatus that executes the multi-valued recording / reproducing system according to the fifth example.

FIG. 60 is an explanatory diagram showing a sixth example of the multilevel recording / reproducing system according to the present invention.

[Fig. 61] Fig. 61 is a configuration diagram of a multilevel recording / reproducing apparatus which executes a multilevel recording / reproducing system according to a sixth example.

FIG. 62 is an explanatory diagram showing a seventh example of the multilevel recording / reproducing system according to the present invention.

[Fig. 63] Fig. 63 is a configuration diagram of a multilevel recording / reproducing apparatus which executes a multilevel recording / reproducing system according to a seventh example.

[Fig. 64] Fig. 64 is a configuration diagram of a convolutional encoder used for execution of a multilevel recording method according to an eighth example.

65 is an explanatory diagram showing state transitions of the output of the convolutional encoder in FIG. 64.

[Fig. 66] Fig. 66 is a configuration diagram of a multilevel recording / reproducing apparatus which executes a multilevel recording / reproducing system according to an eighth example.

FIG. 67 is an explanatory diagram showing a ninth example of the multilevel recording / reproducing system according to the present invention.

FIG. 68 is an explanatory diagram showing a tenth example of the multilevel recording / reproducing system according to the present invention.

FIG. 69 is an explanatory diagram showing an eleventh example of a multilevel recording / reproducing system according to the present invention.

FIG. 70 is an explanatory diagram showing a twelfth example of the multilevel recording / reproducing system according to the present invention.

FIG. 71 is an explanatory diagram showing a thirteenth example of the multilevel recording / reproducing system according to the present invention.

72 is an explanatory diagram showing a fourteenth example of the multilevel recording / reproducing system according to the present invention. FIG.

FIG. 73 is an explanatory diagram showing a fifteenth example of the multilevel recording / reproducing system according to the present invention.

FIG. 74 is an explanatory diagram showing a sixteenth example of the multilevel recording / reproducing system according to the present invention.

FIG. 75 is an explanatory diagram showing a seventeenth example of the multilevel recording / reproducing system according to the present invention.

FIG. 76 is an explanatory diagram showing an eighteenth example of the multilevel recording / reproducing system according to the present invention.

[Fig. 77] Fig. 77 is an explanatory diagram showing a signal modulation system of an external magnetic field strength according to an eighteenth example of the multilevel recording / reproducing system.

[Fig. 78] Fig. 78 is a configuration diagram showing a first example of an external magnetic field intensity modulation circuit according to an eighteenth example of the multilevel recording / reproducing system.

[Fig. 79] Fig. 79 is a configuration diagram showing a second example of the external magnetic field intensity modulation circuit according to the eighteenth example of the multilevel recording / reproducing system.

[Fig. 80] Fig. 80 is an explanatory diagram showing a recording state of magnetization domains recorded by a multilevel recording / reproducing system of an eighteenth example.

81 is a block diagram of a signal reproducing circuit for reading a signal from the magneto-optical recording medium of FIG. 80.

FIG. 82 is an explanatory diagram showing the effect of the multilevel recording / reproducing system according to the eighteenth example.

FIG. 83 is a configuration diagram of a laser irradiation timing modulation circuit applied to a multilevel recording / reproducing system according to a nineteenth example.

84 is a timing chart showing the operation of the circuit of FIG. 83.

[Fig. 85] Fig. 85 is a configuration diagram of a signal reproducing circuit applied to a multilevel recording / reproducing system according to a nineteenth example.

86 is an explanatory diagram of the operation of the circuit of FIG. 85.

[Fig. 87] Fig. 87 is a configuration diagram of a laser intensity modulation circuit applied to a multilevel recording / reproducing system according to a twentieth example.

88 is a timing chart showing the operation of the circuit of FIG. 87. FIG.

[Fig. 89] Fig. 89 is a configuration diagram of a signal reproducing circuit applied to a multilevel recording / reproducing system according to a twentieth example.

90 is an explanatory diagram of the operation of the circuit of FIG. 89. FIG.

[Fig. 91] Fig. 91 is an explanatory diagram showing a first example of a combination of an applied magnetic field and an irradiation laser intensity, which is applied to a twenty-first example of a multilevel recording / reproducing system.

FIG. 92 is an explanatory diagram showing a second example of the combination of the applied magnetic field and the irradiation laser intensity applied to the twenty-first example of the multilevel recording / reproducing system.

[Fig. 93] Fig. 93 is an explanatory diagram showing a third example of a combination of an applied magnetic field and an irradiation laser intensity, which is applied to a twenty-first example of the multilevel recording / reproducing system.

[Fig. 94] Fig. 94 is a graph diagram showing reproduction signal output characteristics of a magneto-optical recording medium applied to a twenty-second example of the multilevel recording / reproducing system.

[Fig. 95] Fig. 95 is an explanatory diagram of a multilevel recording / reproducing system belonging to a twenty-second example.

FIG. 96 is an explanatory diagram of another multilevel recording / reproducing system belonging to the 22nd example.

[Fig. 97] Fig. 97 is an explanatory diagram of test signals according to a twenty-third example of the multilevel recording / reproducing system.

[Fig. 98] Fig. 98 is a configuration diagram of a test signal reproducing circuit according to a twenty-third example of the multilevel recording / reproducing system.

[Fig. 99] Fig. 99 is an explanatory diagram of test signals according to a twenty-fourth example of the multilevel recording / reproducing system.

[Fig. 100] Fig. 100 is a configuration diagram of a test signal reproducing circuit according to a twenty-fourth example of the multilevel recording / reproducing system.

FIG. 101 is an explanatory diagram showing a twenty-sixth example of the multilevel recording / reproducing system.

FIG. 102 is an explanatory diagram showing a first example of the mark edge recording method belonging to the 26th example of the multi-value recording / reproducing system.

FIG. 103 is an explanatory diagram showing a second example of the mark edge recording method belonging to the 26th example of the multi-valued recording / reproducing system.

FIG. 104 is an explanatory diagram showing a third example of the mark edge recording method belonging to the 26th example of the multi-value recording / reproducing system.

FIG. 105 is an explanatory diagram showing a fourth example of the mark edge recording method belonging to the 26th example of the multi-valued recording / reproducing system.

FIG. 106 is an explanatory diagram showing a fifth example of the mark edge recording method belonging to the 26th example of the multi-value recording / reproducing system.

FIG. 107 is an explanatory diagram showing a sixth example of the mark edge recording method belonging to the 26th example of the multi-valued recording / reproducing system.

FIG. 108 is an explanatory diagram showing a 27th example of the multilevel recording / reproducing system.

FIG. 109 is an explanatory diagram showing a twenty-eighth example of the multilevel recording / reproducing system.

FIG. 110 is a configuration diagram of a recording / reproducing apparatus suitable for a sample servo type magneto-optical recording medium.

111 is a DC applied to the recording / reproducing apparatus of FIG. 110.
It is a circuit diagram of a level correction circuit.

FIG. 112 is an explanatory diagram showing a 29th example of the multi-valued recording / reproducing system.

FIG. 113 is a configuration diagram showing a first example of an optimum condition detection circuit applied to the multilevel recording / reproducing system in the 29th example.

FIG. 114 is an explanatory diagram showing the 30th example of the multilevel recording / reproducing system.

FIG. 115 is a configuration diagram showing a second example of the optimum condition detection circuit applied to the multilevel recording / reproducing system in the thirtieth example.

FIG. 116 is an explanatory diagram showing a first example of the test signal recording method belonging to the 31st example of the multi-value recording / reproducing system.

FIG. 117 is an explanatory diagram showing a second example of the test signal recording method belonging to the 31st example of the multi-value recording / reproducing system.

118 is a waveform chart showing a reproduced signal waveform of a test signal recorded by the method of FIG. 116.

119 is a waveform diagram showing a reproduced signal waveform of a test signal recorded by the method of FIG. 117.

FIG. 120 is a configuration diagram showing an optimum condition detection circuit applied to the multilevel recording / reproducing system in the 31st example.

FIG. 121 is an explanatory diagram showing a 32nd example of the multilevel recording / reproducing system.

FIG. 122 is an explanatory diagram showing the 33rd example of the multi-valued recording / reproducing system.

FIG. 123 is an explanatory diagram showing effects of the multilevel recording / reproducing system according to the 33rd example.

FIG. 124 is an explanatory diagram showing a first example of the on-pit recording method belonging to the 34th example of the multi-valued recording / reproducing system.

FIG. 125 is an explanatory diagram showing a second example of the on-pit recording method belonging to the 34th example of the multi-valued recording / reproducing system.

FIG. 126 is an explanatory diagram showing a third example of the on-pit recording method belonging to the 34th example of the multilevel recording / reproducing system.

FIG. 127 is an explanatory diagram showing a fourth example of the on-pit recording method belonging to the thirty-fourth example of the multilevel recording / reproducing system.

FIG. 128 is an explanatory diagram showing a fifth example of the on-pit recording method belonging to the thirty-fourth example of the multi-valued recording / reproducing system.

FIG. 129 is an explanatory diagram showing another example of the multilevel recording / reproducing system according to the present invention.

FIG. 130 is an explanatory diagram showing another example of the multilevel recording / reproducing system according to the present invention.

FIG. 131 is an explanatory diagram showing another example of the multilevel recording / reproducing system according to the present invention.

FIG. 132 is an explanatory diagram showing another example of the multi-valued recording / reproducing system according to the present invention.

FIG. 133 is an explanatory diagram showing another example of the multilevel recording / reproducing system according to the present invention.

FIG. 134 is a configuration diagram showing a first example of a magnetic head device.

FIG. 135 is a configuration diagram showing a second example of the magnetic head device.

FIG. 136 is a configuration diagram showing a third example of a magnetic head device.

FIG. 137 is a configuration diagram showing a fourth example of the magnetic head device.

FIG. 138 is a configuration diagram showing a fifth example of the magnetic head device.

FIG. 139 is a configuration diagram showing a sixth example of the magnetic head device.

FIG. 140 is a configuration diagram showing a seventh example of a magnetic head device.

FIG. 141 is a configuration diagram showing an eighth example of a magnetic head device.

FIG. 142 is an explanatory diagram of a conventional technique.

FIG. 143 is an explanatory diagram of a conventional technique.

FIG. 144 is a graph illustrating the external magnetic field characteristic of the recording layer having two recording states with respect to the external magnetic field.

FIG. 145 is a graph illustrating the external magnetic field characteristic of the recording layer having one recording state with respect to the external magnetic field.

FIG. 146 is an explanatory diagram showing a first example of the multi-value recording principle of the magneto-optical recording medium according to the present invention.

FIG. 147 is an explanatory diagram showing a second example of the multilevel recording principle of the magneto-optical recording medium according to the present invention.

FIG. 148 is an explanatory diagram showing a third example of the multi-valued recording principle of the magneto-optical recording medium according to the present invention.

FIG. 149 is a diagram illustrating the operation (principle) of the present invention.

[Explanation of symbols]

 1 Transparent Substrate 2 Preformat Pattern 3 First Dielectric Layer 4 First Recording Layer 4a Amorphous Perpendicular Magnetization Film 4b Auxiliary Magnetic Film 5 Second Dielectric Layer 6 Second Recording Layer 7 Third Dielectric Layer 8 Reflective Film 9 Protective film 11 Recording track 12 Data recording unit 13 ID area 14 Servo area 15 Data area 16 Tracking pit 17 Test area 18 Clock pit 21 User area 22 Test area 201 First write signal sequence 202 Second write signal sequence 210 For reproduction Laser beam 301 Pre-pit 302 Recording magnetic domain

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number for FI Technical display location G11B 11/10 511 D 9075-5D 586 C 9296-5D (31) Priority claim number Japanese Patent Application No. 6 −213002 (32) Priority Day Hei 6 (1994) September 6 (33) Priority claiming country Japan (JP) (72) Inventor Akihito Sakamoto 1-88, Torora, Ibaraki City, Osaka Prefecture Hitachi Maxell Incorporated (72) Inventor Osamu Ishizaki 1-88, Torora, Ibaraki-shi, Osaka Hitachi Maxel Co., Ltd. (72) Inventor Satoru Onuki 1-88, Torora, Ibaraki-shi, Osaka Hitachi Maxell Co., Ltd. (72) Inventor Toshinori Sugiyama, 1-88, Torora, Ibaraki, Ibaraki, Osaka Hitachi Maxell Co., Ltd. (72) Inventor, Kazuko Ishizuka, 1-88, Tora, Ibaraki, Osaka (1) Hitachi Maxell, Ltd. ( 72) Inventor Masatoshi Hashimoto Ibaraki, Osaka Ushitora chome No. 1 No. 88 Hitachi Maxell, Ltd. in

Claims (84)

[Claims] 1. A hysteresis curve having a plurality of magnetic layers stacked directly or with a non-magnetic layer interposed therebetween, and a temperature change of a hysteresis curve obtained by changing an external magnetic field applied to the plurality of magnetic layers is in a high temperature state. In accordance with the change of the applied external magnetic field, in the above, at least three different magnetic field regions have a region where the total magnetization of the plurality of magnetic layers becomes a single stable magnetization state, and Is a magneto-optical recording medium having a magnetization characteristic that at least three or more magnetization states exist stably according to the magnitude of the external magnetic field applied at a high temperature when the external magnetic field is zero. 2. A plurality of magnetic layers laminated directly or via a non-magnetic layer, and at least one magnetic layer among the plurality of magnetic layers has a magnetic field of 2 with respect to an applied external magnetic field.
The magneto-optical recording film having a recording state in the above different magnetic field regions, and the other magnetic layer is a magneto-optical recording film having at least one recording state in the magnetic field region different from the one magnetic layer. A magneto-optical recording medium characterized by being provided. 3. The magneto-optical recording medium according to claim 2, wherein the first magnetic layer has a recording state in two different magnetic field regions with respect to an applied external magnetic field, and the first magnetic layer. Has a second magnetic layer in which one recording state exists in different magnetic field regions, and four-valued signal recording is possible by switching the magnitude of the external magnetic field in four steps. recoding media. 4. The magneto-optical recording medium according to claim 2, wherein the first magnetic layer has a recording state in two different magnetic field regions with respect to an applied external magnetic field, and the first magnetic layer. Has a second magnetic layer in which two recording states exist in different magnetic field regions, and 4-level recording of a signal is possible by switching the magnitude of the external magnetic field in four steps. recoding media. 5. A recording state having at least two or more magnetic layers laminated directly or via a non-magnetic layer, and each of these magnetic layers has one recording state in a different magnetic field region with respect to an applied external magnetic field. A magneto-optical recording medium characterized by comprising a magneto-optical recording film in which the present invention exists. 6. A recording state exists in a first magnetic layer in which a recording state exists in a first magnetic field region with respect to an applied external magnetic field, and in a second magnetic field region different from the first magnetic field region. A magneto-optical recording medium comprising a second magnetic layer and a second magnetic layer. 7. A magnetic layer having at least one recording state in different magnetic field regions with respect to an applied external magnetic field is laminated at least two or more, and a signal of three or more values is recorded between each magnetic layer. A magneto-optical recording medium characterized by the following. 8. A magnetic layer in which one recording state exists in different magnetic field regions with respect to an applied external magnetic field is laminated at least two or more, and a signal of five values or more is recorded between each magnetic layer. A magneto-optical recording medium characterized by the following. 9. It has at least three or more magnetic layers laminated directly or via a non-magnetic layer, and at least one of these magnetic layers has a magnetic field of 2 with respect to an applied external magnetic field. The other magnetic layer is a magneto-optical recording film in which at least one recording state exists in a magnetic field region different from the one magnetic layer. A magneto-optical recording medium having a structure. 10. A first magnetic layer having a recording state in the first and second magnetic field regions with respect to an applied external magnetic field,
The recording state exists in the second magnetic layer in which the recording state exists in the third magnetic field region different from the first magnetic field region and in the fourth magnetic field region different from the first to third magnetic field regions. Third
A magneto-optical recording medium, which is formed by laminating three magnetic layers of 11. A magnetic layer having a recording state in two or more different magnetic field regions with respect to an applied external magnetic field, and another magnetic layer having at least one recording state in a magnetic field region different from the magnetic layer. A magneto-optical recording medium, characterized in that at least three or more layers are laminated, and signals of five or more values are recorded between the magnetic layers. 12. The magneto-optical recording medium according to claim 1, wherein at least one or more magnetic layers of the magnetic layers are irradiated with a reproducing laser beam on a reproducing laser beam incident side. Then, the magnetic layer is thermally-magnetically formed with an opening smaller than the spot diameter of the reproducing laser beam, so that an opening for realizing so-called magnetic super-resolution recording magnetic domain reading is formed. A magneto-optical recording medium, wherein a part forming layer and a cutting layer are selectively provided. 13. The magneto-optical recording medium according to claim 1, wherein at least one or more magnetic layers of the magnetic layers are irradiated with a reproducing laser beam on a reproducing laser beam incident side. Then, the magnetic layer is thermally-magnetically formed with an opening smaller than the spot diameter of the reproducing laser beam, so that an opening for realizing so-called magnetic super-resolution recording magnetic domain reading is formed. A magneto-optical recording medium having a part forming layer selectively provided. 14. The magneto-optical recording medium according to claim 1, wherein at least one of the magnetic layers has a perpendicular magnetization film, and the perpendicular magnetization film is magnetically connected to the perpendicular magnetization film. A magneto-optical recording medium comprising a combined auxiliary magnetic film. 15. The magneto-optical recording medium according to claim 14, wherein the perpendicular magnetization film is an amorphous alloy containing a rare earth and a transition metal as main components. 16. The magneto-optical recording medium according to claim 14, wherein the perpendicular magnetization film is an amorphous alloy containing a rare earth element and a transition metal as main components, and a sublattice magnetic moment of a rare earth atom makes a transition. A magneto-optical recording medium characterized by comprising a ferrimagnetic material which is more predominant from room temperature to the Curie temperature than the sublattice magnetic moment of metal atoms. 17. The magneto-optical recording medium according to claim 15, wherein the transition metal that is a component of the perpendicular magnetization film is at least one selected from [Co, Fe, Ni, Cr]. One kind of transition metal element,
A magneto-optical recording medium, wherein the rare earth element is at least one kind of rare earth element selected from [Tb, Gd, Dy, Nd, Ho]. 18. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film is made of a magnetic material having the same Curie temperature as the perpendicular magnetic film or a Curie temperature higher than that of the perpendicular magnetic film. Magneto-optical recording characterized in that the magnetic field region in the recording state of the magnetic layer composed of the auxiliary magnetic film and the perpendicular magnetization film is shifted to the high magnetic field region side or the low magnetic field region side with respect to the other magnetic layer. Medium. 19. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film has a magnetization that is more likely to rotate in the direction of an external magnetic field when irradiated with a laser beam for recording or erasing than the perpendicular magnetic film. A magneto-optical recording medium comprising a magnetic layer composed of the auxiliary magnetic film and the perpendicularly magnetized film and having a recording state in two or more different magnetic field regions with respect to an external magnetic field applied. . 20. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film is one of a transition metal, an amorphous alloy of a rare earth and a transition metal, an alloy of a transition metal and a noble metal, oxygen and nitrogen. A magneto-optical recording medium, which is a magnetic material selected from alloys of rare earths and transition metals containing at least one of the above. 21. The magneto-optical recording medium according to claim 14, wherein a magnetic thin film that becomes an in-plane magnetized film at least near room temperature is used as the auxiliary magnetic film. 22. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film is provided on the laser beam incident side of the perpendicularly magnetized film or on the opposite side or both. Medium. 23. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film is made of [Co, Fe, Ni,
Cr, Mn], a magneto-optical recording medium comprising a magnetic thin film containing at least one kind of metal element as a main component. 24. The magneto-optical recording medium according to claim 23, wherein the film thickness of the auxiliary magnetic film is adjusted in the range of 1 to 30 Å. 25. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film comprises [Co, Fe, Ni,
Cr, Mn] and at least one kind of metal element and [Pt, Al, Au, Rh, Pd, Cu,
A magneto-optical recording medium comprising a magnetic thin film made of an alloy with at least one kind of metal element selected from Ag, Re, Ru]. 26. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film is a Co film, a CoFe alloy film, a PtCo alloy film, or an oxidized T film.
bFeCo alloy film, nitrided TbFeCo alloy film, GdFe
A magneto-optical recording medium comprising a magnetic film selected from a Co alloy film, a GdTbFeCo alloy film, an NdFeCo alloy film, and a GdDyFeCo alloy film. 27. The magneto-optical recording medium according to claim 14, wherein the auxiliary magnetic film is made of [Co, Fe, Ni,
Cr, Mn], a metal thin film containing at least one kind of metal element, and [Pt, Al, Au, R
h, Pd, Cu, Ag, Re, Ru] and a metal thin film containing at least one metal element selected from the group consisting of two or more layers alternately stacked. Magneto-optical recording medium. 28. The magneto-optical recording medium according to claim 27, wherein each metal thin film forming the multilayer film has a film thickness of 1
A magneto-optical recording medium characterized by being adjusted to a range of up to 30Å. 29. The magneto-optical recording medium according to claim 1, wherein the data recording area is divided into a plurality of data recording units, and the data recording unit is recorded at the head portion of each data recording unit. Magneto-optical recording medium having a test area for setting a slice level of each signal included in the multi-valued recording signal. 30. The magneto-optical recording medium according to claim 1, wherein the data recording area is divided into a plurality of data recording units, and the data recording unit is recorded at the head portion of each data recording unit. A magneto-optical recording medium having a test area for generating a timing signal which serves as a reference for detecting an edge of a multi-valued recording signal. 31. The magneto-optical recording medium according to claim 1, wherein the data recording area is divided into a plurality of data recording units, and the data recording units are recorded at the head portion of each data recording unit. And a test area for setting a slice level of each signal included in the multi-valued recording signal and for generating a timing signal serving as a reference of timing for detecting an edge of the multi-valued recording signal. Magneto-optical recording medium. 32. The magneto-optical recording medium according to claim 29, wherein a test signal for setting a slice level of a multilevel recording signal recorded in the data recording unit is set in the test area. A magneto-optical recording medium in which at least one signal of each level included in the multilevel recording signal is recorded. 33. The magneto-optical recording medium according to claim 29, wherein the test area is in an unrecorded state even after a multilevel recording signal is recorded in the magnetic layer. Magneto-optical recording medium. 34. The magneto-optical recording medium according to claim 30 or 31, wherein a reference timing for detecting an edge of a multi-valued recording signal recorded in the data recording unit in the test area. A magneto-optical recording medium characterized in that at least one test signal for generating a signal is recorded for all edges between multilevel signal levels. 35. The magneto-optical recording medium according to claim 32, wherein a signal of each level of a test signal for setting a slice level of each signal included in the multi-valued recording signal has a signal level before and after it and an optical signal. A magneto-optical recording medium having an area that does not cause level shift due to optical interference. 36. The magneto-optical recording medium according to claim 34, wherein a signal at each edge of a test signal for generating a timing signal serving as a reference of timing for detecting an edge of the multilevel recording signal A magneto-optical recording medium, characterized in that an edge interval is set to a length not less than an edge shift due to optical interference with an edge signal. 37. The magneto-optical recording medium according to claim 1, further comprising a tracking pit for performing tracking control of a recording or reproducing laser beam and a clock signal used for recording and reproducing a signal. A magneto-optical recording medium in which an embedded pit to be drawn in is recorded in advance. 38. The magneto-optical recording medium according to claim 37, wherein the data recording area is divided into a plurality of data recording units, and the tracking pits and the embedded pits are previously recorded at the head portion of each data recording unit. A magneto-optical recording medium characterized by: 39. The magneto-optical recording medium according to claim 38, each of which is included in the multi-valued recording signal between the formation region of the tracking pit and the formation region of the embedded pit, or after both of these formation regions. A magneto-optical recording medium provided with a test area for setting a slice level of a signal and / or a test area for generating a timing signal serving as a reference of timing for detecting an edge of the multilevel recording signal. . 40. The magneto-optical recording medium according to claim 29, wherein the data recording unit is a sector in a medium having a sector structure. 41. The magneto-optical recording medium according to claim 29, wherein the data recording unit has a structure in which signals for synchronizing clocks are recorded at regular intervals. A magneto-optical recording medium, which is an area from one signal to the next signal. 42. The magneto-optical recording medium according to claim 29, wherein the data recording unit is an area divided for each arbitrary number of bytes. 43. The magneto-optical recording medium according to claim 1, wherein an information signal is two-dimensionally multi-valued recorded by two parameters of an edge position of a recording magnetic domain and a level position corresponding to a magnetization state. A magneto-optical recording medium characterized by the following. 44. The magneto-optical recording medium according to claim 1, wherein the information signal includes an edge position of a recording magnetic domain, a level position corresponding to a magnetization state, and a level position corresponding to a width of the magnetic domain. A magneto-optical recording medium in which three-dimensional multi-value recording is performed with three parameters. 45. The magneto-optical recording medium according to claim 1, wherein a test area for detecting the optimum recording condition is provided outside the user area. . 46. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 1, and the optical head moves along a recording track of the magneto-optical recording medium. While irradiating a laser beam,
An external magnetic field in which the applied magnetic field intensity is signal-modulated in multiple stages is applied to the laser beam irradiating section from the magnetic head in accordance with a recording signal, and a signal is multi-value recorded on the magneto-optical recording medium. Recording method for magneto-optical recording media. 47. The recording method for the magneto-optical recording medium according to claim 46, wherein the laser beam is irradiated periodically or in a pulsed form. 48. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 1, and an external magnetic field is applied from the magnetic head to the magneto-optical recording medium. Meanwhile, along the recording track of the magneto-optical recording medium, the optical head irradiates a laser beam whose laser intensity is signal-modulated in multiple steps according to a recording signal, and multi-level records the signal on the magneto-optical recording medium. A recording method for a magneto-optical recording medium characterized by: 49. A recording method for a magneto-optical recording medium according to claim 48, wherein the external magnetic field strength is varied at a constant frequency. 50. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 1, and the magneto-optical recording medium is transferred from the magnetic head to a magneto-optical recording medium according to a recording signal. While the external magnetic field in which the applied magnetic field intensity is modulated in multiple steps is applied, the laser intensity is signal-modulated in multiple steps along the recording track of the magneto-optical recording medium from the optical head according to the recording signal. A recording / reproducing system for a magneto-optical recording medium, characterized in that a multi-valued signal is recorded on the magneto-optical recording medium by irradiating a laser beam. 51. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 1, and the magneto-optical recording medium is irradiated with a laser beam emitted from the optical head. While repeatedly scanning the same track on the recording medium, the intensity, the modulation frequency, the pulse width of the laser beam emitted from the optical head and / or the intensity, the modulation frequency of the magnetic field applied from the magnetic head each time the scanning is repeated. A recording / reproducing system for a magneto-optical recording medium, characterized in that a recording condition such as a modulation amplitude range is switched in multiple stages to record a signal on the same track in multiple levels. 52. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 5,
While applying an external magnetic field whose applied magnetic field strength is signal-modulated in multiple steps according to a recording signal from the magnetic head, a laser beam is continuously or periodically applied from the optical head along a recording track of the magneto-optical recording medium. Alternatively, a recording / reproducing method for a magneto-optical recording medium is characterized in that a signal of three or more values is recorded between the magnetic layers by irradiating in a pulse shape. 53. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 5,
While applying an external magnetic field whose applied magnetic field strength is signal-modulated in multiple steps according to a recording signal from the magnetic head, a laser beam is continuously or periodically applied from the optical head along a recording track of the magneto-optical recording medium. Alternatively, by irradiating in a pulse shape and forming a mixture of magnetic domains whose magnetic domain length is half or less of the spot diameter of the laser beam and magnetic domains of half or more of the spot diameter, it is possible to obtain five or more values between the magnetic layers. A recording / reproducing method for a magneto-optical recording medium characterized by recording a signal. 54. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 9,
While applying an external magnetic field whose applied magnetic field strength is signal-modulated in multiple steps according to a recording signal from the magnetic head, a laser beam is continuously or periodically applied from the optical head along a recording track of the magneto-optical recording medium. Alternatively, a recording / reproducing system for a magneto-optical recording medium is characterized in that a signal of five values or more is recorded between the magnetic layers by irradiating in a pulse shape. 55. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 5,
While the external magnetic field is applied from the magnetic head to the magneto-optical recording medium at a constant cycle, the laser intensity is signal-modulated in three or more steps along the recording track of the magneto-optical recording medium by the optical head according to the recording signal. A recording / reproducing system for a magneto-optical recording medium, characterized in that a signal having three or more values is recorded on the magneto-optical recording medium by irradiating the laser beam. 56. An optical head and a magnetic head are driven relative to the magneto-optical recording medium according to claim 9,
While the external magnetic field is applied from the magnetic head to the magneto-optical recording medium at a constant period, the laser intensity is signal-modulated by the optical head along the recording track of the magneto-optical recording medium in five steps or more according to the recording signal. A recording / reproducing system for a magneto-optical recording medium, characterized in that a signal having five or more values is recorded on the magneto-optical recording medium by irradiating the laser beam. 57. A magneto-optical recording medium recording / reproducing system according to claim 46, wherein a recording signal is recorded on the magneto-optical recording medium at a mark position. Play method. 58. A recording / reproducing system for a magneto-optical recording medium according to claim 46, wherein a recording signal is recorded on the magneto-optical recording medium by mark edge recording. Play method. 59. A magneto-optical recording method according to any one of claims 46 to 58, wherein a multi-level recording signal of a partial response method is recorded between the magnetic layers. Recording / playback method of media. 60. A recording / reproducing system for a magneto-optical recording medium according to claim 59, wherein the partial response system is PR (1,1), PR (1, -1), PR.
A recording / reproducing system for a magneto-optical recording medium, characterized in that a signal is ternarily recorded between each of the magnetic layers by using one of the systems selected from (1, 0, -1). 61. A recording / reproducing system for a magneto-optical recording medium according to claim 59, wherein the partial response system is PR (1,2,1), PR (1,1, -1,-).
1), PR (1, 2, 0, -2, -1), PR (1,
A recording method of a magneto-optical recording medium, characterized in that a signal is quintetically recorded between each of the magnetic layers by using one of the methods selected from 3, 3, 1). 62. A recording / reproducing system for a magneto-optical recording medium according to claim 46, wherein a multilevel recording signal of a trellis coded modulation system is recorded between the magnetic layers. Recording / reproducing method for magnetic recording media. 63. A recording / reproducing system for a magneto-optical recording medium according to claim 59, wherein a maximum likelihood decoding method is used for binarizing a recorded multilevel recording signal. Recording / reproducing method for magnetic recording media. 64. The recording / reproducing system for a magneto-optical recording medium according to claim 46, wherein a data recording area of the magneto-optical recording medium is divided into a plurality of data recording units, and each data recording unit is divided. A recording / reproducing method for a magneto-optical recording medium, characterized in that recording / reproducing of a multilevel recording signal is performed. 65. The recording / reproducing system for a magneto-optical recording medium according to claim 64, wherein when recording a multi-valued recording signal in the data recording unit, the multi-valued recording signal is recorded at the head portion of the data recording unit or at regular intervals. At least one test signal for setting the slice level of each signal included in the multilevel recording signal is recorded for each signal included in the multilevel recording signal, and the multilevel recording signal from the data recording unit is recorded. When reproducing, the test signal is read from the head portion of the data recording unit, the slice level corresponding to each signal included in the multilevel recording signal is set, and the data recording is performed at each of these slice levels. A recording / reproducing system for a magneto-optical recording medium, wherein a read signal from a unit is sliced to reproduce the multilevel recording signal. 66. In the recording / reproducing system for a magneto-optical recording medium according to claim 64, when recording a multi-valued recording signal in the data recording unit, the multi-valued recording signal is recorded at the head portion of the data recording unit or at regular intervals. At least one test signal for generating a timing signal serving as a timing reference for detecting an edge of a multi-valued recording signal is recorded for all edges between multi-valued signal levels, and a test signal from the data recording unit is recorded. When reproducing the value recording signal, the test signal is read from the head portion of the data recording unit, the reference timing of edge detection of each signal included in the multi-value recording signal is generated, and the reference timing is set to each of these reference timings. After independently detecting the edge of each signal included in the read signal from the data recording unit, the reference timing of the edge detection A recording / reproducing system for a magneto-optical recording medium, characterized in that the multi-valued recording signal is reproduced by synthesizing each edge detection signal with reference to the above. 67. A recording / reproducing system for a magneto-optical recording medium according to claim 64, wherein when recording a multi-valued recording signal in said data recording unit, said multi-valued recording signal is recorded at a head portion of said data recording unit or at regular intervals. Timing for recording at least one test signal for setting the slice level of each signal included in the multi-valued recording signal for each signal included in the multi-valued recording signal and detecting an edge of the multi-valued recording signal When recording at least one test signal for generating a timing signal serving as a reference for all edges between multilevel signal levels, and reproducing the multilevel recording signal from the data recording unit,
The test signal is read from the head portion of the data recording unit, the slice level corresponding to each signal included in the multilevel recording signal is set, and the read signal from the data recording unit is set at each slice level. And the test signal is read from the head portion of the data recording unit to generate the reference timing of edge detection of each signal included in the multi-valued recording signal, and the data recording is performed at each of these reference timings. After independently detecting the edge of each signal included in the read signal from the unit,
A recording / reproducing system for a magneto-optical recording medium, characterized in that the multi-valued recording signal is reproduced by synthesizing each edge detection signal with reference to the reference timing of the edge detection. 68. A recording / reproducing system for a magneto-optical recording medium according to claim 64, wherein a reproduction signal of an unrecorded test area provided at a head portion of a data recording unit is used as a reference.
A recording / reproducing system for a magneto-optical recording medium, characterized in that the fluctuation of the DC level of a reproduced multilevel recording signal is corrected. 69. In the recording / reproducing system for a magneto-optical recording medium according to claim 64, a tracking control signal of a recording or reproducing laser beam is converted from a reproduction signal of a tracking pit provided at the head portion of a data recording unit A recording / reproducing system for a magneto-optical recording medium which is generated and controls an optical head by this tracking control signal. 70. A recording / reproducing system for a magneto-optical recording medium according to claim 64, wherein a channel clock is generated by a PLL circuit from a reproduction signal of an embedded pit provided at a head portion of a data recording unit, and this channel clock is used. A recording / reproducing system for a magneto-optical recording medium characterized by controlling a laser driving circuit, a multilevel encoder, and a multilevel decoder. 71. A magneto-optical recording medium recording / reproducing system according to claim 58, wherein a signal of an arbitrary edge and a signal of an edge before and after the magnetic field have a length equal to or more than a length that does not cause edge shift due to optical interference. The recording magnetic domain is formed at a constant cycle in the domain length and the magnetic domain interval, and the edge position of the recording magnetic domain is stepwise modulated in a range sufficiently smaller than the recording magnetic domain cycle in two or more steps according to the information signal. Recording and reproducing of a magneto-optical recording medium characterized by performing mark edge recording of a multi-valued recording signal on a magnetic recording medium and performing two-dimensional multi-valued recording by two parameters of an edge position of a recording magnetic domain and a level position corresponding to a magnetization state. method. 72. A recording / reproducing method for a magneto-optical recording medium according to claim 46, wherein the recording magnetic domain length is kept constant by simultaneously controlling the intensity of the recording laser beam and the recording pulse width. At the same time, the magneto-optical recording is characterized in that the three-dimensional multi-value recording is performed by changing the recording magnetic domain width, and by the three parameters of the edge position of the recording magnetic domain, the level position corresponding to the magnetization state, and the level position corresponding to the width of the magnetic domain. Recording / playback method of media. 73. An external magnetic field is applied to an optical head for irradiating a laser beam along a recording track and a laser beam irradiating portion of the magnetic layer for the magneto-optical recording medium according to claim 1. Of the plurality of signal trains obtained by relatively driving the magnetic head for dividing the multi-valued recording signal and using the laser beam or the external magnetic field which is multi-valued signal modulated by the first signal train. After writing the first signal sequence to the recording track of the second recording track, a second signal having a width narrower than that of the first write signal sequence is formed on the first write signal sequence.
Repeating the process of overwriting the write signal sequence of (1) with a laser beam or an external magnetic field that is multi-valued signal modulated in the second signal sequence for all divided signal sequences,
A recording / reproducing system for a magneto-optical recording medium, characterized in that a multi-valued signal is recorded on the one recording track rather than the multi-valued signal. 74. A recording / reproducing system for a magneto-optical recording medium according to claim 73, wherein a four-valued recording signal is divided into two signal trains, and a laser beam having a constant intensity is applied to one recording track by the optical head. While irradiating along, while applying an external magnetic field signal-modulated into four values by the first signal train to the laser beam irradiation unit to write the first signal train on one recording track, A central portion of the first write signal train is irradiated with a second write signal train having a width narrower than that of the first write signal train, and a laser beam having a constant intensity is irradiated from the optical head along the first recording track. At the same time, by applying an external magnetic field that is signal-modulated into four values in the second signal train, the data is overwritten and 16-value recording signals are recorded on the 1 recording track. Re-recording of recording medium Raw method. 75. A recording / reproducing system for a magneto-optical recording medium according to claim 73, wherein a 4-level recording signal is divided into two signal trains, and an external magnetic field of a constant intensity is applied from said magnetic head, A laser beam, which is signal-modulated into a four-valued pulse with a signal train of 1, is irradiated along one recording track to write the first signal train on the one recording track, and thereafter, the first signal train is written. A second write signal train having a width narrower than that of the first write signal train is applied to the central portion of the write signal train while applying an external magnetic field having a constant intensity from the magnetic head, A magneto-optical device characterized in that a laser beam signal-modulated in the form of a pulse of a value is irradiated along the one recording track so as to be overwritten, and a 16-level recording signal is recorded on the one recording track. How to record / reproduce recording media formula. 76. A recording / reproducing system for a magneto-optical recording medium according to claim 73, wherein a four-valued recording signal is divided into two signal trains, and a laser beam whose intensity is modulated in a pulse shape from the optical head is divided into one. While irradiating along the recording track, the external magnetic field that is signal-modulated into four values by the first signal train is applied to the laser beam irradiation unit to write the first signal train on one recording track. After that, a second write signal train having a width narrower than that of the first write signal train is provided at the center of the first write signal train, and a laser beam whose intensity is pulse-modulated by the optical head is provided. 1
While irradiating along the recording track of No. 1, while writing is performed by applying an external magnetic field that is signal-modulated into four values by the second signal train, 16 recording signals are recorded on the one recording track.
A recording / reproducing system for a magneto-optical recording medium, which is characterized by recording values. 77. The first signal train having a spot diameter is written along a recording track of a magneto-optical recording medium on which a signal is recorded by the recording / reproducing system according to any one of claims 73 to 76. And reproducing a multi-valued recording signal recorded on the magneto-optical recording medium by irradiating a reproducing laser beam having a diameter equal to or larger than the width of the first write signal train formed by Recording / reproducing method for magneto-optical recording medium. 78. A laser irradiated from the optical head after mounting the magneto-optical recording medium according to claim 45 on a recording / reproducing apparatus, positioning an optical head and a magnetic head in a test area provided outside the user area. While changing the intensity and pulse width of the beam in a stepwise or continuous manner, a constant test pattern that is a combination of signals included in a multilevel recording signal to be recorded on the magneto-optical recording medium is written, and thereafter, the test pattern is changed. A recording / reproducing system for a magneto-optical recording medium, which reproduces a test pattern and compares a reproduced signal amplitude with a reference signal amplitude to obtain an optimum recording condition of each signal included in the multilevel recording signal. 79. An optical head and a magnetic head are positioned in a test area provided outside the user area after the magneto-optical recording medium according to claim 45 is mounted in a recording / reproducing apparatus, and an external voltage applied from the magnetic head is applied. While changing the magnetic field strength stepwise or continuously, write a constant test pattern that combines each signal included in the multilevel recording signal to be recorded on the magneto-optical recording medium, and then reproduce the test pattern. Then, the reproduction signal amplitude is compared with the reference signal amplitude to obtain the optimum recording condition of each signal included in the multi-valued recording signal. 80. A magneto-optical recording / reproducing apparatus comprising: a drive unit for a magneto-optical recording medium; and an optical head and a magnetic head mounted on the drive unit so as to face the magneto-optical recording medium. As a result, by having two or more windings in one magnetic circuit and driving each winding independently,
A magneto-optical recording / reproducing apparatus comprising a magnetic head for applying a multi-step external magnetic field to the magneto-optical recording medium. 81. The magneto-optical recording / reproducing apparatus according to claim 80, wherein a constant bias magnetic field is applied to the magneto-optical recording medium by any one of the two or more windings. Magneto-optical recording / reproducing device. 82. A magneto-optical recording / reproducing apparatus comprising: a drive unit for a magneto-optical recording medium; and an optical head and a magnetic head mounted on the drive unit so as to face the magneto-optical recording medium. Drive independently of each other
A magneto-optical recording / reproducing apparatus in which one or more magnetic heads are arranged close to each other. 83. The magneto-optical recording / reproducing apparatus according to claim 82, wherein a constant bias magnetic field is applied to the magneto-optical recording medium by any one of the two or more magnetic heads. Magneto-optical recording / reproducing device. 84. The magneto-optical recording / reproducing apparatus according to claim 80, wherein a permanent magnet is arranged close to the magnetic head, and a constant bias is applied to the magneto-optical recording medium by the permanent magnet. A magneto-optical recording / reproducing apparatus characterized by applying a magnetic field.