JP2808640B2 - Magneto-optical recording method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording method, and is suitably applied, for example, when recording information on a magneto-optical disk by a light intensity modulation recording method.

B. Summary of the Invention In the magneto-optical recording method of the light intensity modulation recording method, after irradiating a laser beam having a laser power having a high level, the laser beam is controlled to be turned off for a predetermined period thereafter. This can prevent excessive heating of the multilayer magneto-optical recording medium.

C Conventional Technique Conventionally, a first film and a second film having perpendicular magnetic anisotropy are formed by:
The multi-layered magneto-optical disk serving as the recording / reproducing layer and the recording auxiliary layer is irradiated with laser light at different light intensities according to the recording information, whereby a single laser beam is applied to the magneto-optical disk. There has been proposed a magneto-optical recording method of a so-called light intensity modulation recording system capable of overwriting (overwriting) data (JP-A-62-175948).
JP-A-63-52355).

That is, as shown in FIG. 6, the multilayer magneto-optical disc 1 is composed of a first substrate and a second substrate having perpendicular magnetic anisotropy on one surface of a transparent substrate 2 such as a glass plate via a dielectric film 3.
The recording / reproducing layer 4 and the recording auxiliary layer 5 made of a magnetic thin film are sequentially laminated by continuous spattering or the like, and a protective film 6 made of a non-magnetic metal film or a dielectric film is formed on the surface thereof. I have.

As shown in FIG. 7, the recording / reproducing layer 4 and the recording auxiliary layer 5 of the magneto-optical disc 1 are, for example, at room temperature.
It is made of a rare-earth dominant film (RE-rich) material such as TbFeCo which has a large resistance H _{C1 at} T _R (about -20 to 60 ° C.) and a low Curie temperature T _C1 , and the recording auxiliary layer 5 is at room temperature T _R. It is formed of a transition metal dominant film (TM-rich) material such as GdTbFeCo, which has a small coercive force H _C2 and a high Curie temperature T _C2 .

Recording information in the magneto-optical disc 1, the magnetization directions of the respective recording layers 4 and the auxiliary recording layer 5 as shown in FIG. 8 showing with arrows, recording magnetized upward at room temperature T _R A first and a second combination of the auxiliary layer 5 and the recording / reproducing layer 4 magnetized upward or downward.
According to the states ST _A and ST _B , for example, a value “0” and a value “1” are recorded, respectively.

Here, as a magneto-optical recording method for recording desired recording information on the magneto-optical disk 1, first, a first or second state is described.
When recording information having a value of “0” on the magneto-optical disc 1 of ST _A or ST _B, the temperature T is higher than the query temperature T _C1 of the recording / reproducing layer 4 and lower than the query temperature T _C2 of the recording auxiliary layer 5.
The laser light comprising a sufficient first laser power P _LOW to control the _ER by irradiating a predetermined time, controls the direction of magnetization of the recording layer 4 to the unstable third state ST _C.

Thereafter, the magneto-optical disk 1 is naturally cooled, and the magnetization direction of the recording / reproducing layer 4 is changed by the exchange coupling force acting on the interface between the recording / reproducing layer 4 and the recording auxiliary layer 5.
Is oriented in the same upward direction as the magnetization direction of the magneto-optical disc 1, and thus the magneto-optical disc 1 is placed in the first position where the value "0" or the value "1" is recorded.
Alternatively, control is performed from the second state ST _A or ST _B to the first state ST _A in which the recording state is a value “0”.

On the other hand, when recording information having a value of “1” on the magneto-optical disc 1 in the first or second state ST _A or ST _B , first, a high temperature near the query temperature T _C2 of the recording auxiliary layer 5 is used. A laser beam having a second laser power P _HIGH higher than the first laser power P _LOW sufficient to control to T _REC is irradiated for a predetermined time, and the coercive force H _{C2 of} the recording auxiliary layer 5 at the temperature T _REC is larger than that. A downward recording magnetic field H _REC (for example, 3
(Approximately 00 to 500 [Oe]).

Thus, the magneto-optical disc 1 is in the fourth state in which the recording / reproducing layer 4 is unstable and the recording auxiliary layer 5 is oriented downward.
Is controlled to ST _D, by being naturally cooled after this, Yotsute the exchange coupling force exerted on the interface of the recording layer 4 and the auxiliary recording layer 5, the magnetization method of the recording and reproducing layer 4 is the magnetization direction of the auxiliary recording layer 5 It is controlled to a fifth state ST _E made in the same downward direction and.

Further to this magneto-optical disc 1 After this, smaller than the coercive force H _C1 at room temperature T _R of the recording layer 4, the auxiliary recording coercivity H _C2 is greater than the upward at room temperature T _R of the auxiliary layer 5 field H _SUB (e.g. 3 to 5 [KOe]), only the magnetization direction of the recording auxiliary layer 5 was oriented upward, and thus the magneto-optical disk 1 was recorded with the value “0” or “1”. from the first or second state ST _a or ST _B, controls the second state ST _B consisting of a recording state of the value "1".

In this way, in this magneto-optical recording method, the magnetization direction can be controlled upward or downward depending on the intensity of the laser power, thereby making it possible to perform recording using a single laser beam. Without erasing information,
New recording information can be overwritten on the magneto-optical disc 1.

D Problems to be Solved by the Invention In the magneto-optical recording method, the magneto-optical disk 1 is constantly irradiated with a laser beam having the first laser power P _LOW or the second laser power P _HIGH. Disk 1 when pulsed with laser light
Has a problem that the temperature distribution tends to be broader than the conventional magneto-optical recording method in which only the laser beam having the second laser power P _HIGH is turned on / off.

That is, for example, the magneto-optical disk 1 is irradiated with a laser beam of the second laser power P _HIGH to record a value “1”, and then irradiated with a laser beam of the first laser power P _LOW. To record the value “0”, the magneto-optical disk 1 heated by the laser light of the second laser power P _HIGH is used.
By irradiating the laser light of the first laser power P _{LOW in} a state where the area around the pit is not sufficiently cooled,
There is a possibility that the temperature of the magneto-optical disc 1 exceeds the Curie temperature T _{C1 at} which the magnetization direction of the recording / reproducing layer 4 becomes unstable, and reaches the vicinity of the Curie temperature T _C2 of the recording auxiliary layer 5.

Therefore, in the overwriting by the above-described magneto-optical recording method, the shapes of the pits formed in the recording / reproducing layer 4 are likely to be irregular, noise is generated due to the deterioration of C / N, and two adjacent When the interval between the pits is small, it is difficult to separate the two pits, and the error rate increases.

Further, the degree of the thermal effect of the portion irradiated with the laser light of the first laser power P _LOW varies depending on the length of the irradiation interval of the laser light of the second laser power P _HIGH. optimal range of the first laser power P _LOW varies Te, the first range of the laser power P _LOW such that optimal summer to cause problems been made narrower than a result various pulse interval.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a magneto-optical recording method of a light intensity modulation recording system capable of forming pits with correct shapes and intervals.

E. Means for Solving the Problem In order to solve the problem, in the present invention, at least the first film 4 and the second film 5 of the multilayer magneto-optical recording medium 1 are used.
The first film 4 and the second film 5 are irradiated with a laser beam L having a first laser power P _LOW at a low level according to the record information DT _REC to irradiate the first film 4 and the second film 5 The recording information DT _REC is recorded by increasing the temperature to about the first query temperature T _C1 so as to be magnetized, and the laser beam L having the second laser power P _HIGH which is at a high level according to the recording information DT _REC is _generated. Irradiate the first film 4 and the second film 5 to the second
A magneto-optical recording method of a light intensity modulation recording method in which the recording information DT _REC is recorded by heating the film 5 to a second temperature T _C2 higher than the first temperature T _C1 and magnetizing the film 5. And the first and second laser powers P _LOW and P
_HIGH is individually controlled in accordance with the ambient temperature and the linear velocity of the multilayer magneto-optical recording medium 1,
The second laser power P, which is at a high level,
After irradiation with the laser beam L having a _HIGH, when irradiating the laser beam L having a first laser power P _LOW made at a low level, the laser beam L having a second laser power P _HIGH
And the irradiation of the laser beam L having the first laser power P _LOW with a cooling period of the recording layer.

F action The recording information DT _{REC is} recorded on the recording layer of the multilayer magneto-optical recording medium 1.
The first film 4 and the second film 5 are irradiated with a laser beam L having a first laser power P _LOW in accordance with the temperature of the first film 4 so that the first film 4 and the second film 5 are heated to about the first Curie temperature T _C1 and magnetized. thereby to record the record information DT _REC in, first a first layer 4 and the second layer 5 is irradiated with a laser beam L having a second laser power P _HIGH in response to the recording information DT _REC of the second film 5 to about 2 Kiyuri temperature T _C2 warmed so as to magnetized recorded information D
A magneto-optical recording method of a light intensity modulation recording method for recording T _REC , wherein first and second laser powers P _LOW and P _HIGH are individually controlled according to an environmental temperature and a linear velocity, and a multilayer film light is recorded. The second laser power is applied to the recording layer of the magnetic recording medium 1.
After irradiating the laser light L having P _HIGH and then irradiating the laser light L having first laser power P _LOW , the laser light L having second laser power P _HIGH and the first laser power P By providing a cooling period for the recording layer between the laser light L having _LOW and the irradiation, the first film 4 and the second film 5 can always be magnetized at an optimum temperature.

G Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In FIG. 1 in which the same reference numerals are given to the parts corresponding to those in FIG. 6, reference numeral 10 denotes a magneto-optical disc apparatus of a light intensity modulation recording system to which the magneto-optical recording method according to the present invention is applied. A permanent magnet 12 for generating a recording magnetic field H _REC (FIG. 7) for applying a recording magnetic field H _REC (FIG. 7) is provided on the front side corresponding to the position irradiated with the laser beam L by the optical pickup 11 from the back side of the magnetic disk 1. Are located.

In addition to this, approximately 18 on the same surface side of the magneto-optical disc 1
The auxiliary magnetic field H _SUB (7th
(See FIG.).

In the case of this magneto-optical disk device 10, an optical pickup 11
Is driven to emit light by a laser drive signal _DRV input from a laser emission control circuit 15 through a drive amplification circuit 14.

The laser light emission control circuit 15 receives the input recording data.
When DT _REC (FIG. 2 (A)) is a value “0”, a laser drive signal D _RV (FIG. 2 (B)) capable of irradiating the laser beam L having the first laser power P _LOW for a predetermined time is used. It occurs, controlling the magneto-optical disc 1 to Kiyuri temperature T lower than the _C2 temperature T _ER of the recording and reproducing layer 4 of Kiyuri temperature T _C1 than high and the auxiliary recording layer 5.

On the other hand, the laser emission control circuit 15
_{When REC} has a value of “1”, a laser drive signal _DRV capable of irradiating the laser beam L having the second laser power P _HIGH for a predetermined time is generated, and the magneto-optical disc 1 is moved to the cure temperature T _{C2 of the} recording auxiliary layer 5. Control to higher temperature T _REC .

Further in the laser emission control circuit 15 of this embodiment, depending on the value "1" of the recording data DT _REC, after irradiation with the laser beam L consisting of the second laser power P _HIGH, recording data DT _REC value " when the transition to 0 "is prior to applying a laser beam L consisting of the first laser power P _lOW, during a predetermined time period tau _1, lower than the first laser power P _lOW third laser power generating a laser drive signal D _RV consisting of P _OFF, this way, during the practice laser light L of a predetermined time tau _1, it is adapted to turn off control.

Thus, the magneto-optical disk 1 is irradiated with the laser beam L of the second laser beam P _HIGH to record the value “1”, and subsequently irradiated with the laser beam L of the first laser power P _LOW. When recording the value “0” by using the second laser power
After cooling the periphery of the pits of the magneto-optical disk 1 heated by the P _HIGH laser beam L to the vicinity of the query temperature T _C1 at which the magnetization direction of the recording / reproducing layer 4 becomes unstable, the first laser power P _{LOW is obtained.} Of the laser beam L can be applied.

Thus the magneto-optical disc 1, exceeds the Kiyuri temperature T _C1 of the magnetization direction in an unstable state of the recording and reproducing layer 4, and by that can be controlled to a low temperature T _ER by Kiyuri temperature T _C2 of the auxiliary recording layer 5, the recording and reproducing The pits can be formed on the layer 4 with the correct shape and spacing.

In addition, depending on the length of the irradiation interval of the laser light L of the second laser power P _HIGH , the thermal effect of the portion irradiated with the laser light L of the first laser power P _LOW can be controlled almost uniformly, so that various effects can be obtained. The range of the first laser power P _LOW that is optimal for the pulse interval can be widened.

In the above configuration, according to the experiment, for example, after irradiating the laser beam L with the second laser power P _HIGH as described above, the laser beam L is controlled to be turned off using the third laser power P _OFF. Irradiating the laser light L with the first laser power P _LOW immediately after irradiating the laser light L with the second laser power P _HIGH ,
_As shown in FIG. 3, the maximum value P _LMAX and the minimum value P _LMIN that can be taken by _LOW vary according to duty, which is the ratio of the pulse width to the laser light irradiation interval of the second laser power P _HIGH. Having.

The maximum value P that the first laser power P _LOW can take
_LMAX represents the laser power for _{raising the} temperature of the magneto-optical disc 1 until immediately before the recording auxiliary layer 5 is inverted, and the minimum value P _LMIN is the temperature at which the magneto-optical disc 1 is heated to the minimum required for inverting the recording / reproducing layer 4. Indicates the laser power for raising the temperature.

In this experiment, the linear velocity of the magneto-optical disk 1, the second laser power P _HIGH and the irradiation interval were set to constant values of 8 [m / s], 17 [mW], and 68 [nsec], respectively. ing.

Incidentally, according to this experiment, the second laser power P _HIGH
Immediately after irradiating the laser light L, the first laser power
For magneto-optical recording method of a conventional optical intensity modulation recording method for irradiating a laser beam L P _LOW, the maximum value P _LMAX1 and minimum value P _LMIN1 of possible first laser power P _LOW is a solid line in FIG. 3 As shown by, as the duty increases to 10, 20, 30, and 40%, the duty gradually decreases.

On the other hand, after irradiating the laser beam L with the second laser power P _HIGH and then turning off the laser beam L using the third laser power P _OFF , the magneto-optical recording of the light intensity modulation recording method according to the present invention. In the case of the method, the maximum value P _LMAX2 and the minimum value P _LMIN2 that the first laser power P _LOW can take are, as shown by broken _lines in FIG. 3, a substantially constant value in a range where the duty is in the range of 10 to around 30%. Hold, the duty exceeds 30%, 40,
As it increases to 50%, it has the characteristic of slowly falling.

As a result, when modulating the recording data DT _REC to obtain the laser drive signal D _RV , for example, the duty range is 10 to 33.
%, The maximum value P _LMAX and the minimum value P _LMIN of the first laser power P _LOW can be in the range of the conventional magneto-optical recording method shown in FIG. 1 in
As shown by the dotted line, the laser power is 6.6 to 7.6 m
W], whereas in the case of the magneto-optical recording method according to the present invention, as shown by a two-dot chain line in FIG. 3, the laser power has a range ΔB of about 6.6 to 8.4 [mW].
It can be seen that it has a much wider range than the conventional laser power range ΔA.

As a result, the range of the first laser power P _LOW that is optimal for various pulse intervals is expanded,
The power margin of the first laser power P _LOW can be significantly increased.

In practice, necessary to increase the temperature of the recording layer 4 and the auxiliary recording layer 5 of the magneto-optical disc 1 to the disc temperature T _ER or T _REC controlling the third state ST _C or fourth state ST _D respectively The first or second laser power P _LOW or P _HIGH is, as shown by the solid or broken line in FIGS. 4 and 5, respectively.
The magneto-optical disc 1 has a characteristic that changes in accordance with an environmental temperature as a temperature factor and a linear velocity of the magneto-optical disc 1 as an irradiation time of the laser beam L.

Therefore, in the case of this embodiment, the laser emission control circuit 15
In the above, the first and second laser powers P _LOW and P _LOW are set according to the ambient temperature and the linear velocity of the magneto-optical disc 1 described above.
_HIGH and then individually controlled, always optimal recording layer 4 and the auxiliary recording layer 5 of the magneto-optical disc 1 to the disc temperature T _ER or T _REC controlling the third state ST _C or fourth state ST _D respectively The temperature can be raised.

According to the above method, after irradiating the laser light L with the second laser power P _HIGH , the third laser power P _OFF is supplied for the subsequent predetermined period τ ₁ to control the laser light L to be turned off. By doing so, excessive heating of the magneto-optical disc 1 can be prevented beforehand, and pits can be formed at correct shapes and intervals according to the recording data DT _REC .

In the above-described embodiment, the case where the present invention is applied to a magneto-optical recording method of recording information on a multilayer magneto-optical disk has been described. However, the shape of the recording medium is not limited to a disk, and may be, for example, a card or a tape. It can be widely applied to multilayered magneto-optical recording media and the like.

H Effects of the Invention As described above, according to the present invention, the recording layer of the multilayered magneto-optical recording medium is irradiated with laser light having a first laser power according to the recorded information, and the first and second films are formed. The recording information DT _REC is recorded by increasing the temperature of the first film to about the first Curie temperature of the second film so as to be magnetized, and irradiating the first film with a laser beam having a second laser power according to the recorded information. And a light intensity modulation recording type magneto-optical recording method for recording information by raising the temperature of the second film to about the second Curie temperature of the second film and magnetizing the second film. After individually controlling the laser power according to the ambient temperature and the linear velocity, and irradiating the recording layer of the multilayer magneto-optical recording medium with the laser light having the second laser power, the laser having the first laser power is irradiated. When irradiating light, the second laser power The cooling period of the recording layer is provided between the irradiation of the laser beam having the first laser power and the laser beam having the first laser power, so that the first film and the second film are always magnetized at the optimum temperature. Thus, the first film and the second film, each of which is magnetized with a correct shape and an interval in accordance with the recorded information, respectively.
A magneto-optical recording method capable of forming a pit made of a film can be realized.

In addition, the first and second laser powers are individually controlled in accordance with the environmental temperature and the linear velocity, so that the first and second laser powers are controlled.
The temperature of the film and the second film can be raised to an optimum temperature.

Further, after irradiating the recording layer of the multilayer magneto-optical recording medium with a laser beam having the second laser power, when irradiating the laser beam having the first laser power with the laser beam having the second laser power, And the laser beam having the first laser power is irradiated with the laser beam having the second laser power. Magnetization can be accurately performed at an optimum temperature without affecting the temperature when the laser beam having the laser power of 1 is irradiated and heated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a magneto-optical disc apparatus to which a magneto-optical recording method according to one embodiment of the present invention is applied, FIG. 2 is a signal waveform diagram for explaining the operation thereof, and FIG. 3 is laser power and duty. FIG. 4 is a characteristic curve diagram showing the relationship between the temperature change of the magneto-optical disk and the laser power, FIG. 5 is a characteristic curve diagram showing the relationship between the linear velocity of the magneto-optical disk and the laser power, 6 is a schematic sectional view showing a multilayer magneto-optical disk, FIG. 7 is a characteristic curve diagram for explaining the multilayer magneto-optical disk, and FIG. 8 is a state transition of the multilayer magneto-optical disk by overwriting operation. FIG. 1 ... multilayer magneto-optical disc, 4 ... recording / reproducing layer, 5 ...
... Recording auxiliary layer, 10 ... Magneto-optical disc device, 11 ... Optical pickup, 12 ... Permanent magnet for generating recording magnetic field, 13 ... Permanent magnet for generating auxiliary magnetic field, 14 ... Drive amplifier circuit, 15 ... Laser Light emission control circuit.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-43816 (JP, A) JP-A-63-175230 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 11/10

Claims (1)

(57) [Claims] A recording layer comprising at least a first film and a second film of a multi-layer magneto-optical recording medium, which is irradiated with a laser beam having a first laser power at a low level in accordance with recording information; The recording information is recorded by increasing the temperature of the first film and the second film to about the first Curie temperature of the first film so as to be magnetized, and the second laser which is at a high level in accordance with the recording information The first film and the second film are irradiated with a laser beam having power so as to be heated to a second Curie temperature higher than the first Curie temperature of the second film and magnetized. A magneto-optical recording method of a light intensity modulation recording system for recording recording information, wherein the first and second laser powers are individually controlled according to an ambient temperature and a linear velocity of the multilayer magneto-optical recording medium. The above multilayer magneto-optical After irradiating the recording layer of the recording medium with the laser light having the second laser power at the high level, and then irradiating the laser light having the first laser power at the low level, A magneto-optical recording method, wherein a cooling period of the recording layer is provided between irradiation of the laser light having the second laser power and the laser light having the first laser power.