JPH07334890A - Method and device for magneto-optical recording - Google Patents

Abstract

PURPOSE:To maintain excellent reproducibillty of mark length and to perform a stable high-density recording by changing recording correction in response to the change in the heat characteristics of recording medium. CONSTITUTION:A magneto-optic disk D is rotated with a specified number of rotation by a motor 1. On the other hand, the binarized information inputted into a binarized information inputting section 5 is modulated by a modulation circuit 4 and a laser beam source 2 emits an intensity-modulated laser beam in accordance with the signal. The outgoing beam is converged by an irradiation optics system 3 and applied to the magneto-optic disk D to be recorded. In this case, the modulation circuit 4 controls the intensity of the recording laser beam at different values depending on the cases of recording a mark longer and shorter than the delay time tR on the same track. It is possible to maintain an excellent reproducibility and to perform a stable high-density recording even for the medium whose thermal characteristics at the time of recording greatly vary in the area related to mark formation.

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 for recording, erasing and reproducing with a laser beam.

[0002]

2. Description of the Related Art Recently, an optical recording / reproducing method satisfying various requirements including high density, large capacity, high access speed, and high recording / reproducing speed, and a recording apparatus, reproducing apparatus and recording medium used therefor. Efforts are being made to develop. Among a wide range of optical recording / reproducing methods, the magneto-optical recording / reproducing method has a unique advantage that information can be recorded and then erased, and new information can be recorded again and again. For being full of the greatest attraction.

A recording medium used in this magneto-optical recording / reproducing method has a perpendicular magnetic anisotropy composed of one layer or multiple layers as a layer for storing a recording.
r orlayers: hereinafter referred to as perpendicular magnetic anisotropic film). This perpendicular magnetic anisotropic film is, for example, amorphous GdF.
e, GdCo, GdFeCo, TbFe, TbCo, TbFeCo, etc. The perpendicular magnetic anisotropic film generally has concentric or spiral tracks, and information is recorded on the tracks. There are two types of tracks, explicit and implicit. [Explicit Track] The magneto-optical recording medium has a disk shape. In a disc having explicit tracks, tracks for recording information are formed in a spiral shape or a concentric circle shape when viewed in a direction perpendicular to the disk plane. There is a groove for tracking and separation between two adjacent tracks. The space between the grooves is called a land. In reality, the relationship between the land and the groove is reversed on the front and back of the disc. Then, looking at the disc from the same direction as the beam is incident, the front is a groove,
The back is called land. Since the perpendicular magnetic anisotropy film is formed on the entire surface of the groove and the land, the groove portion may be a track or the land portion may be a track. There is no particular relationship between the width of the groove and the width of the land.

As described above, generally, the substrate has a land formed in a spiral or concentric shape on the surface and a groove sandwiched between two adjacent lands. A thin perpendicular magnetic anisotropic film is formed on such a substrate. As a result, the perpendicular magnetic anisotropic film has lands and grooves. [Mark] In the present specification, “upward (upwar
d) "or" downward "
Orientation "and the other is defined as" reverse A orientation ".

The information to be recorded is binarized in advance, and this information has a mark (B ₁ ) having a magnetization in "A direction".
Then, two signals of the mark (B ₀ ) having the magnetization in the “reverse A direction” are recorded. These marks B ₁ and B ₀ correspond to either one or the other of the digital signals 1 and 0, respectively. However, generally, the magnetization of the track to be recorded is aligned in the "reverse A direction" by applying a strong external magnetic field before recording. Act to align the magnetization direction is referred to as the "initialization ^* (initialize ^*)" in the old sense. Then, the mark (B
₁ ) to form. Information is represented by the presence or absence of the mark (B ₁ ), the position, the front end position, the rear end position of the mark, the mark length, and the like. Particularly, a method in which the edge position of the mark represents information is called mark length recording. The mark has been called a pit or a bit in the past, but recently it is called a mark.

In addition to the basic recording principle described above, efforts have been recently made to develop the technology in order to further enhance the functions. For example, in the conventional magneto-optical recording, when it is desired to re-record information that has already been recorded in another information, first erase the recorded information (align the magnetization of the recording portion in the initialization direction). Without it, new information could not be recorded. On the other hand, by adding a magnetic layer (which is referred to as a recording layer or a W layer in this specification) that plays a recording aid and an initializing magnetic field, the magnetization of this layer is changed by the action of exchange coupling force. Recording is performed by transferring to a magnetic layer that plays a role of recording / reproducing (this layer is referred to as a memory layer or an M layer in this specification), and thereafter, the recording layer returns to its original magnetization by an initializing magnetic field. By performing the operation of returning to the direction, new information can be overwritten without erasing the already recorded information. A medium having such a function is called an overwrite medium. As an additional technique for improving the perfection of this technique, a magnetic layer for adjusting the exchange coupling force between the recording layer and the memory layer (in this specification, this layer is referred to as an intermediate layer or an I layer). Was proposed.

In order to obtain a larger reproduced signal by transferring the magnetization of the memory layer,
Techniques such as adding a magnetic layer having a larger magneto-optical effect (this layer is referred to as a reading layer or an R layer in the present specification) have also been proposed. By the way, since increasing the recording density further enhances the attractiveness of the magneto-optical recording medium, recently efforts have been made especially for this purpose. In order to increase the recording density, the recording marks may be packed and formed small. However, if the marks are packed too much, the signal from the adjacent mark will enter and the reproduction quality of the mark will deteriorate. Therefore, there is a limit in reducing the distance between marks. So, within a certain limit,
A mark length recording method has been proposed for the purpose of recording information with the highest possible density. In this recording method, the length of information is represented by the distance between two marks, but the length of one mark represents the length of information. That is, it is a method that enables higher density recording by the principle that one mark shorter than the limit value between two marks can be recorded. However, in this method, the higher the density, the more the mark shape tends to depend on the mark length. Therefore, it is necessary to accurately record the mark length, and thus the recording correction is necessary.

[0008]

However, the recording correction methods proposed so far cannot suppress the dependence of the mark shape on the mark length, which is not a sufficient level for high density recording.

[0009]

As a result of earnest research for solving the above problem, the present inventor has found that the thermal characteristics of the recording medium greatly change in the region related to the formation of the mark.
It was found that the reproducibility of the mark length can be kept good if the recording correction is changed according to the change, and the present invention has been completed.

Therefore, in the first aspect of the present invention, the following relational expression T = A exp (-t / τ ₁ ) + B exp {(-t + t _R ) /
For a magneto-optical recording medium satisfying τ ₂ }, t in the same track
_A magneto-optical recording method, wherein the recording laser beam intensity is set to a different value when a mark longer than _R is recorded and when a mark shorter than t _R is recorded.

However, T: rise temperature of the medium when a laser beam is irradiated for recording or reproducing on the magneto-optical recording medium t: longest recording mark length elapsed time τ ₁ : first thermal time constant τ ₂ : second thermal time constant t _R : delay time L: longest recording mark length V: linear velocity, and secondly, “recording laser beam intensity is a magneto-optical recording medium rotated at a predetermined rotational speed. 2. The magneto-optical recording according to claim 1, wherein when a binarized signal having a predetermined frequency with a duty ratio of 50% is recorded and then reproduced, the duty ratio of the reproduced signal is set to 50%. 3. A magneto-optical recording according to claim 2, characterized in that, thirdly, the "recording laser beam intensity is the recording pulse length or the recording laser beam intensity and the recording pulse length." Method, and fourth, Magneto-optical recording apparatus comprising rotating means for magneto-optical recording medium, laser beam light source, irradiation optical system for guiding and converging the beam emitted from the laser beam light source onto the medium, laser beam modulating means, information input section and recording magnetic field. in the laser beam modulation means, for the case of recording the longer mark than t _R in the same track, in the case of recording a mark shorter than t _R, and controls the recording laser beam intensity to a value different from the light Magnetic recording device.

However, t _R is the temperature rise T of the medium when a laser beam is irradiated for recording or reproduction on the magneto-optical recording medium, as expressed by the following equation T = A exp (-t / τ ₁ ). + B exp {(-t + t _R ) /
It is the delay time when expressed by τ ₂ }. Here, t: longest recording mark length elapsed time τ ₁ : first thermal time constant τ ₂ : second thermal time constant L: longest recording mark length V: linear velocity, and fifthly, “laser beam modulation” The means records when a binarized signal having a predetermined frequency with a duty ratio of 50% is recorded and reproduced on a magneto-optical recording medium rotated at a predetermined rotation speed so that the reproduction signal has a duty ratio of 50%. 5. A magneto-optical recording device according to claim 4, wherein the laser beam intensity is set, and sixth, "the recording laser beam intensity is the recording pulse length or the recording laser beam. 6. The magneto-optical recording device according to claim 5, wherein the intensity and the recording pulse length are provided.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0014]

[Embodiment 1] This embodiment is that of the magneto-optical recording apparatus according to claim 4, and this apparatus, as shown in FIG. 1, includes a motor 1, a laser beam light source 2, and a beam emitted from the laser beam light source. Irradiation optical system 3 that guides and focuses light on the medium,
The laser beam modulator 4 comprises a binarized information input section 5 and a recording magnetic field 6, and functions as follows.

That is, the magneto-optical disk D set in this recording apparatus is rotated by the rotating means 1 at a predetermined rotation speed. On the other hand, the binarized information input to the binarized information input unit 5 is modulated by the modulation circuit 4, and the laser beam light source 2 emits an intensity-modulated laser beam according to the signal. The emitted beam is condensed by the irradiation optical system 3 and is irradiated onto the magneto-optical disk D for recording.

At this time, the modulation circuit 4 sets t on the same track.
_The recording laser beam intensity is controlled to a different value when recording a mark longer than _R and when recording a mark shorter than t _R.

[0017]

[Embodiment 2] This embodiment is one of the magneto-optical recording method according to claim 1. The temperature drop during recording on the medium at a linear velocity of 11.3 m / s is given by the following equation: T = A exp (−t / τ ₁ ) + B exp {(−t + t _R ) /
A medium satisfying τ ₂ } and having t _R = 170 ns was prepared.

After the magnetization direction of this medium was oriented (initialized) in one direction, it was set in the magneto-optical recording apparatus described in Example 1 and then rotated at a linear velocity of 11.3 m / s. Recording magnetic field of 300
After adjusting to Oe, a laser beam having a wavelength of 830 nm was condensed and irradiated to a diameter of about 1 μm by an irradiation optical system, and recording was performed by 1-7 modulation. At this time, the laser beam intensity, as shown in FIG. 2, the recording laser beam intensity for recording a mark having a length shorter than t _R 2~4T, longer than t _R 5 to 8 t
The length of the mark was changed by the recording laser beam intensity.

Incidentally, the value of L / V is shown below: 8T: L / V = 11.3 × 300 × 10 ⁻⁹ /11.3=3×10 ⁻⁷ s
= 300 ns 7T: 262.5ns 6T: 225 ns 5T: 187.5ns 4T: 150 ns 3T: 112.5ns 2T: 75 ns.

The recorded mark was reproduced and the jitter of the reproduced signal was measured. The results are shown in Table 1 together with the results of the comparative examples described below. From Table 1, it can be seen that the present invention clearly reduces the jitter as compared with the comparative example.

[0021]

[Table 1]

[0022]

[Comparative Example] Recording and reproduction were performed under the same conditions as in Example, except that the recording laser beam intensity for marks having a length of 2T to 8T was the same as that of 2T (see FIG. 3).
The jitter of the reproduced signal was measured. The results are shown in Table 1.

[0023]

Embodiment 3 This embodiment is that of the magneto-optical recording method according to claim 3. The same media used in Example 2 was prepared. After the magnetization direction of this medium was oriented (initialized) in one direction, the medium was set in the magneto-optical recording apparatus described in Example 1 and then rotated at a linear velocity of 11.3 m / s. The recording magnetic field was adjusted to 300 Oe, a laser beam having a wavelength of 830 nm was condensed and irradiated to a diameter of about 1 μm by an irradiation optical system, and recording was performed by 1-7 modulation. At this time, the recording pulse is t _R as shown in FIG.
The recording pulse length for recording a shorter mark of 2 to 4T and the recording pulse length for recording a mark of 5 to 8T longer than t _R were changed.

The recorded mark was reproduced and the jitter of the reproduced signal was measured. The results are shown in Table 1 together with the results of the comparative examples described above. From Table 1, it can be seen that the present invention clearly reduces the jitter as compared with the comparative example.

[0025]

[Embodiment 4] This embodiment is that of the magneto-optical recording method according to claim 3. The same media used in Example 2 was prepared. After the magnetization direction of this medium was oriented (initialized) in one direction, the medium was set in the magneto-optical recording apparatus described in Example 1 and then rotated at a linear velocity of 11.3 m / s. The recording magnetic field was adjusted to 300 Oe, a laser beam having a wavelength of 830 nm was condensed and irradiated to a diameter of about 1 μm by an irradiation optical system, and recording was performed by 1-7 modulation. At this time, the recording pulse is t _R as shown in FIG.
Recording laser beam intensity and recording pulse length for recording a shorter mark of 2 to 4T and 5 to 8 longer than t _R
The recording laser beam intensity and the recording pulse length for recording the T length mark were changed.

The recorded mark was reproduced and the jitter of the reproduced signal was measured. The results are shown in Table 1 together with the results of the comparative examples described above. It can be seen from Table 1 that the present invention clearly reduces the jitter as compared with the comparative example, and also reduces the jitter as compared with the examples 2 and 3.

[0027]

As described above, according to the present invention, the reproducibility of the mark length can be excellently maintained even in the medium in which the thermal characteristics at the time of recording greatly change in the region related to the mark formation. , Stable high density recording is now possible.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a magneto-optical recording device manufactured in Example 1 of the present invention.

FIG. 2 is an explanatory diagram of a recording laser beam intensity pattern according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional recording laser beam intensity pattern used in a comparative example.

FIG. 4 is an explanatory diagram of a recording laser beam intensity pattern of Example 3 of the present invention.

FIG. 5 is an explanatory diagram of a recording laser beam intensity pattern according to the fourth embodiment of the present invention.

FIG. 6 is a conceptual diagram showing thermal characteristics of a magneto-optical recording medium. However, the vertical axis is logarithmic.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Laser beam light source 3 ... Irradiation optical system 4 ... Laser beam modulation circuit 5 ... Input part of binary information 6 ... Recording magnetic field D ... Magneto-optical Recording medium or above

Claims (6)

[Claims] 1. The following relational expression T = A exp (−t / τ ₁ ) + B exp {(−t + t _R ) /
For a magneto-optical recording medium satisfying τ ₂ }, t in the same track
_A magneto-optical recording method, wherein the recording laser beam intensity is set to a different value when a mark longer than _R is recorded and when a mark shorter than t _R is recorded. However,
T: Temperature rise of the medium when a laser beam is irradiated for recording or reproduction on the magneto-optical recording medium t: Longest recording mark length elapsed time τ ₁ : First thermal time constant τ ₂ : Second heat Time constant t _R : Delay time L: Longest recording mark length V: Linear velocity 2. The recording laser beam intensity is such that when a magneto-optical recording medium rotated at a predetermined rotation number is reproduced after recording a binarized signal having a predetermined frequency with a duty ratio of 50%, the reproduction signal has a duty ratio of the reproduction signal. 2. The magneto-optical recording method according to claim 1, wherein is set to 50%. 3. The magneto-optical recording method according to claim 2, wherein the recording laser beam intensity is the recording pulse length, or the recording laser beam intensity and the recording pulse length. 4. A rotating means for a magneto-optical recording medium, a laser beam light source, an irradiation optical system for guiding and converging a beam emitted from the laser beam light source onto the medium, a laser beam modulating means, an information input section and a recording magnetic field. in magneto-optical recording apparatus comprising the laser beam modulation means, and when recording longer marks than t _R in the same track, in the case of recording a mark shorter than t _R, by controlling the recording laser beam intensity at different values A magneto-optical recording device. However, t _R is a temperature rise T of the medium when a laser beam is irradiated for recording or reproducing on a magneto-optical recording medium, which is expressed by the following formula T = A exp (−t / τ ₁ ) + B exp { (-T + t _R ) /
It is the delay time when expressed by τ ₂ }. Here, t: elapsed time of the longest recording mark length τ ₁ : first thermal time constant τ ₂ : second thermal time constant L: longest recording mark length V: linear velocity 5. A laser beam modulating means, when a binarized signal of a predetermined frequency having a duty ratio of 50% is recorded and reproduced on a magneto-optical recording medium rotated at a predetermined rotation number, the duty ratio of the reproduced signal is reproduced. 5. The magneto-optical recording apparatus according to claim 4, wherein the recording laser beam intensity is set so as to be 50%. 6. The magneto-optical recording apparatus according to claim 5, wherein the recording laser beam intensity is the recording pulse length or the recording laser beam intensity and the recording pulse length.