JPH076433A - Recording method for magneto-optical recording - Google Patents

Abstract

PURPOSE:To form recording magnetic domains of always the same shape and size with high accuracy by forming a preheating region of a specified period. CONSTITUTION:A recording film is required to be irradiated with a laser beam for a specified period of time in order to maintain the temp. of the recording film at a specified value without depending on the environmental temp. of use by controlling a preheating power. The irradiation time is more governed by the timing for recording than the time when the specified temp. is attained. The recording film temp. is conversely required to be kept constant within the specified time when a preheating mode is started. The edge shift and jitter at the time of information recording are suppressed by preheating the recording film to a specified temp. by the preheating power and the interference between pits is kept constant by combining this preheating with multipulses at the time of recording on the magnet-optical disk. The preheating period of the specified period is provided in such a manner, by which the recording magnetic domains of always the same shape and size are formed with high accuracy without depending in environmental temp., etc. High-density magnet-optical recording is thus attained by the technique of making the magnetic domains definite by recording waveforms.

Description

Detailed Description of the Invention

[0001]

The present invention relates to recording using laser light,
The present invention relates to a magneto-optical recording for reproducing or erasing, and more particularly to a recording method suitable for highly accurate control of a recording magnetic domain shape in ultra-high density magneto-optical recording.

[0002]

2. Description of the Related Art With the progress of the advanced information society in recent years, there is a growing need for a high-density and large-capacity file memory. Optical recording is attracting attention as a memory that can meet this demand. Recently, rewritable magneto-optical recording has been put into practical use. In recent years, research and development have been advanced with the aim of further improving the performance of magneto-optical recording. At the center of this is the improvement of recording capacity. In order to improve the recording density, methods such as narrowing the track pitch and narrowing the bit pitch have been considered. by the way,
In magneto-optical recording, especially when the bit pitch is narrowed, thermal interference between bits may occur. In this case, in particular, when the mark length recording or the bit pitch is reduced to perform high density recording, it may cause edge shift or jitter, which may be fatal when performing high density recording using this method. . On the other hand, as a publicly known example in which the edge shift is suppressed during recording, there is JP-A-3-22223. In this example, the recording code string of the recording mark is pulsed to form a series of pulse trains corresponding to the length of the recording code train, and the pulse train is controlled according to the length of the pulse train, and the pulse train is divided into three parts. The recording was performed by changing the pulse width of.

[0003]

In the above-mentioned prior art, when the recording sensitivity of the recording medium fluctuates due to the fluctuation of the thickness of the recording medium or the temperature of the operating environment, the bit pitch is reduced to realize the high density recording. In some cases, thermal interference between recorded bits that occurs in some cases has not been sufficiently taken into consideration, and high-precision magnetic domain shape control may not be performed.
As a result, there was a natural limit to the increase in density.

An object of the present invention is to provide a method for suppressing fluctuations in recording sensitivity with respect to a recording medium and thermal interference between recording bits, and to provide a high density optical recording / reproducing apparatus.

A second object of the present invention is to improve the matching between the optical recording device and the optical disc.

A third object of the present invention is to improve the recording capacity of the recording / reproducing apparatus.

[0007]

In order to realize the above-mentioned conventional technique, at least a plurality of power levels are required for recording information on a disk in magneto-optical recording in which recording, reproduction, or erasing is performed by using a laser beam. When recording using a recording waveform consisting of, after a recording command is issued,
This is achieved by performing recording through a preheating mode of the recording film for a certain period of time. In the magneto-optical recording, a recording waveform composed of a plurality of power levels used when recording information on a disc is composed of at least four power levels, a first level is a reproduction level and a second level is preheating. Levels, the third level and the fourth level are recording levels, and each level needs to be a power level set in consideration of the heat flow in the recording medium.

At the above preheating level, it is necessary to control the laser power so that the temperature of the recording film will always be a constant temperature without depending on the ambient temperature. At this preheat level, the recording pulse is emitted after the temperature of the recording film becomes constant after a certain period of time. If this is not done, the environmental temperature and the laser power seem to have changed apparently, and the recording magnetic domains having the same shape were not always obtained under any conditions.

By controlling the preheating power, the temperature of the recording film can be controlled to be a constant value without depending on the operating environment temperature. For that purpose, it is necessary to irradiate the recording film with laser light for a certain period of time. Even when the recording film is irradiated with the preheating power, the irradiation time is controlled by the recording timing rather than the time when the temperature is constant. Therefore, when a recording command is issued and the preheat mode is entered, it is necessary to make the temperature of the recording film constant within a fixed time. Therefore, at the preheat level, in order to keep the temperature of the recording film constant, the preset preheat level is set after the temperature has been high for a certain period of time in the preheat mode, and the higher level is 1.1 times higher than the preheat level. The above should be set to 1.3 times or less. The pulse width is preferably synchronized with the write clock, and the level and pulse width are preferably changed according to the structure of the disk and the material used. this is,
It was about how to make the device.

When the preset preheat level is entered after the preheat mode has been at the high level for a certain period of time, it is preferable to change the level in the high level portion of the constant period depending on the environmental temperature and the disc. This is because the temperature of the recording film differs depending on the environment in which the recording / reproducing apparatus is used, the fluctuation of the laser power, and the difference between the disks. Here, at the preheat level, the power which is not recorded on the disc must be set.

[0011]

When recording on a magneto-optical disk, by preheating the recording film to a constant temperature with preheating power, edge shift and jitter during information recording can be suppressed and combined with multi-pulse. Thus, the interference between bits can be made constant regardless of the recording pattern.

[0012]

EXAMPLE FIG. 1 is a schematic sectional view of a magneto-optical disk used in an example of the present invention. A silicon nitride film 2 was formed on a glass or plastic substrate 1 having an uneven guide groove by a sputtering method. The film thickness is 85 nm. Next, the TbFeCoNb film 3 was formed by the sputtering method. The film thickness is 25 nm. Then, the silicon nitride film 4
Was formed by a sputtering method. The film thickness is 15 nm.
Finally, the Al ₉₅ Ti ₅ film 5 was formed by the sputtering method. The film thickness is 50 nm. This structure is an example,
Considering optical interference, there is a structure that can obtain a large Kerr rotation angle magneto-optically. Finally, the entire recording medium was covered with the ultraviolet curable resin 6.

FIG. 2 is a block diagram showing the structure of the magneto-optical disk drive used. The feature of this drive is that it has a trial writing function. Test recording was performed at regular time intervals when the disk drive was started, when the disk was loaded, or while the disk drive was operating.

First, the wavelength of the laser beam used for recording is 78
It is 0 nm. The recording / reproducing apparatus includes a recording medium 101 for storing information and an optical head 1 for realizing recording / reproducing.
02 and a processing system for converting a reproduction signal obtained from the optical head 102 into information. The optical head 102 narrows the light emitted from the laser 108 onto the recording medium 101. When recording information, an input data bit string (information) is input to the encoder 104, and the recording code string input to the encoder 104 and output from the encoder 104 is the recording waveform generator 1.
The recording waveform obtained by the recording waveform generator 105 is input to the APC 106, and the light intensity corresponding to the recording code string is output from the laser 108. At the time of reproducing information, the light reflected from the recording medium 101 is guided to the light receiver 109,
It is converted into an electric signal. The signal is the reproduction amplifier 110.
Is input to the waveform equalizer 111 and the input switch 112. The input switch 112 is converted into a pulse signal indicating the presence or absence of a reproduction signal of either the reproduction amplifier 110 or the waveform equalizer 111 according to the trial writing command signal. The pulse signal is guided to the discriminator 115 and the PLL 114. P
The synchronization signal output from the LL 114 (a signal synchronized with the basic cycle of the pulse signal) is input to the discriminator 115.

The discriminator 115 generates a detection code string from the pulse signal and the synchronizing signal, and outputs a data pit string (information) by the decoder 117. Further, the detection code string of the discriminator 115 is output to the comparison discriminator 116. Comparison discriminator 1
Reference numeral 16 is a trial writing device 1 which operates by a trial writing command signal.
The trial write data from the encoder 03 is output to the encoder 104, and the input switch 112 that operates according to the trial write command signal switches to output the output of the reproduction amplifier 110 to the shaper 113. The symbol code string and the reproduced code string from the discriminator 115 are compared, the difference between the reproduced code string from the symbol code string is reduced to some extent, and the trial writing end signal is output within an allowable range.

After the trial writing end signal is output, the input switch 112 outputs the output of the waveform equalizer 111 to the shaper 11.
The output is switched to 3 and the normal recording / reproducing operation is started. Even after the normal recording operation is started, the comparative discriminator 1
In step 16, it is confirmed that the difference between the recorded code string and the reproduced code string is within the allowable range. If the difference is not allowable, the above-mentioned test writing operation is started, and when the test writing end signal is output, Continue normal recording operation. When the comparison discriminator 116 confirms the difference in the reproduction code string from the recording code string, the output of the input switch 112 is
It is possible to detect the reproduction amplifier 110 more accurately by operating it so as to output the signal.

In these operations, the input switch 1
A similar operation can be realized without using 12. In order for the comparison discriminator 116 to accurately detect the difference in the reproduced code string from the recorded code string, it is better not to use the waveform equalizer 111.

First, FIG. 3 shows the temperature change of the recording film when preheating power is applied to the recording film. From this figure, it can be seen that the time required for the temperature of the recording film to become constant is the disk position: r = 30 mm, the rotation speed of the disk is 3000 rpm,
It can be seen that the wavelength of the laser is 780 nm and that at least 100 ns or more time is required.

On the other hand, the temperature change of the recording film when the laser waveform having the shape shown in FIG. 4 is applied is shown in the lower part of FIG. The temperature change was obtained by computer simulation.
From this figure, it was possible to shorten the time to 70 ns while keeping the temperature of the recording film constant. When the temperature of the disk and its drive is changed, the temperature of the recording film also changes accordingly. Therefore, the temperature of the recording film is controlled to be always constant by changing the power according to the environmental temperature.

Recording / reproduction was performed on a disk by using the recording / reproducing apparatus and the recording medium described above. The device used had a disk rotation speed of 3000 rpm and a laser wavelength of 78
0 nm, and (1,7) RLL was used for the modulation method. Here, recording was performed so that the recording density was the same at any position on the disc. The recording waveform used for recording on this disc was the same waveform as that shown in FIG. The laser power used was read level: Pr = 1.5 mW, preheat level: Pa.
s = 3.5 mW, first recording level: Pw1 = 5.8 mW,
Then, the second recording level: Pw2 = 6.1 mW was set. Here, the value of each power varies depending on the laminated structure of the disk and the material used.

However, the most effective effect for suppressing the jitter, edge shift and the like caused by the thermal interference between the recording domains to a certain value or less is the layered structure of the disks except for the materials used. When this is evaluated by the parameters of the recording / reproducing apparatus, Pw1 / Pas and Pw2 / Pa
It is necessary that the ratio of s and Pw1 / Pw2 be within a certain range. When this value is measured for many discs, 1.5 <Pw1 / Pas <1.7, 1.6 <Pw2
When the mark length recording was performed on the discs within the range of /Pas<1.8, 0.9 <Pw1 / Pw2 <1.1, the length and width of the recording domain formed could be precisely controlled. The control accuracy at that time was ± 0.02 μm or less in the domain length (disk track direction) and ± 0.05 μm or less in the domain length direction (disk radial direction). This accuracy is a value obtained from both the measurement of the jitter and the edge shift at the time of reproduction and the measurement by the MFM (scanning magnetic force microscope).

Then, an attempt was made to record / reproduce in the innermost zone of the 5.25 "disc. First, at room temperature (20 ° C)
In (1), a random pattern was recorded using the (1,7) RLL method with the previously set power. The jitter distribution at that time is shown in FIG. This is the result of measurement without applying PLL. According to this, the window width ratio was 39%. Further, when the amount of edge shift was measured, it could be suppressed to ± 2 ns or less.

[0023]

According to the present invention, by providing the preheating region for a certain period, it is possible to always form the recording magnetic domain having the same shape and size with high accuracy without depending on the environmental temperature and the like. Further, it is important for controlling the shape of the recording magnetic domain to keep the temperature of the recording film constant by the preheating power which plays an important role in recording. Moreover, the temperature of the recording film must be kept constant from the recording timing in a short time. In that case,
The method of stabilizing the recording waveform according to the present invention is effective, and high density magneto-optical recording can be realized.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a magneto-optical disk used in an example of the present invention.

FIG. 2 is a block diagram showing the configuration of a magneto-optical disk drive that uses an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a temperature change of a recording film when preheating power is applied to the recording film.

FIG. 4 is an explanatory diagram showing a temperature change of the recording film when the recording film is irradiated with a waveform-controlled preheating power.

FIG. 5 is a waveform diagram used for recording in the example of the present invention.

FIG. 6 is an explanatory diagram showing a jitter distribution when a random pattern is recorded.

[Explanation of symbols]

1 ... Disk substrate, 2 ... Silicon nitride film, 3 ... TbFe
CoNb film, 4 ... Silicon nitride film, 5 ... Al ₉₅ Ti ₅ ,
6 ... UV curable resin layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Ide 1-280 Higashi Koigokubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Takeshi Maeda 1-280 Higashi Koigokubo, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory (72) Inventor Fumio Kugiya 1-280 Higashi Koigokubo, Kokubunji City, Tokyo Inside Hitachi Central Research Laboratory

Claims (7)

[Claims] 1. In magneto-optical recording for recording, reproducing, or erasing with a laser beam, when recording information on a disk, when recording is performed using a recording waveform having a plurality of power levels, recording is performed. A recording method for magneto-optical recording, characterized in that after a command is issued, recording is performed through a preheating mode of the recording film for a certain period of time. 2. A magneto-optical recording for recording, reproducing, or erasing by using a laser beam, wherein a recording waveform composed of a plurality of power levels, which is used when recording information on a disk, comprises four power levels, The first level is the regeneration level, the second level is the preheat level,
A recording method for magneto-optical recording, wherein the third level and the fourth level are recording levels, and each level is a power level set in consideration of heat flow in a recording medium. 3. The recording method of magneto-optical recording according to claim 1, wherein the laser power is controlled so that the temperature of the recording film does not depend on the operating environment temperature and always becomes a constant temperature. 4. The recording method for magneto-optical recording according to claim 1, wherein a recording pulse is emitted after the temperature of the recording film becomes constant after a certain period of time. 5. The method according to claim 1, 2, 3 or 4, in which the temperature of the recording film is kept constant, a preset preheat level is set after a high level has been maintained for a certain period of time in the residual heat mode, and more advantageously Higher level is more than 1.1 times preheat level 1.
A recording method of magneto-optical recording which is 3 times or less, the pulse width of which is synchronized with the write clock, and the level and pulse width are changed depending on the structure of the disk and the material used. 6. The method according to claim 1, 2, 3, 4 or 5.
A recording method for magneto-optical recording in which, when the preset preheat level is reached after entering the preheat mode for a certain period of time and then the set preheat level is changed, the level is changed depending on the environmental temperature or the disc difference at the high level part for a certain period of time. . 7. A recording method for magneto-optical recording according to claim 1, 2, 3, 4, 5 or 6, wherein the power is set so that the disk is not recorded.