JPH0721612A - Recording method for magneto-optical recording - Google Patents

Abstract

PURPOSE:To execute high-density magneto-optical recording by suppressing the degradation in the output of reproduced signals due to fluctuation in the recording sensitivity of a disk and deterioration of a recording film by repetition of recording/erasing at the time of test recording. CONSTITUTION:An Si3N4 film 2 is sputtered on a substrate 1 having guide grooves and a TbFeCoNb film 3, an Si3N4 film 4 and an Al95Ti5 film 5 are successively superposed thereon by sputtering. There are some other structures with which magneto-optically large Kerr rotating angles are obtainable in addition to the structure described above if optical interference is taken into consideration. Finally, the recording medium laminate is coated with a UV curing type resin 6. These films are used and further, the way of applying heat from the magneto-optical disk device to a disk is devised. Since meximum temp. of the recording film at the time of irradiation with a laser beam is lowered, the deterioration in the magnetic characteristics by the relaxation of the structure, etc., of the recording film is suppressed and the accuracy in the control of the shape of the recording magnetic domains is improved. High-density magneto- optical recording is thus possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording method effective for improving the repetitive recording / erasing characteristics in magneto-optical recording for recording / reproducing / erasing by using a laser beam.

[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 response to this. Recently, magneto-optical disks have been commercialized as image files and document files as rewritable optical disks. At present, many research institutions are conducting research and development with the aim of improving their performance. One of them is the improvement of recording density. As methods for increasing the density, there are methods such as recording on the entire surface of the disk at the same recording density, narrowing the bit pitch and track pitch, using light with a short wavelength, and using the mark length recording method. These methods should be used together. Thus, high density optical recording can be realized.
In this case, it is important to precisely control the width and length of the recording magnetic domain to be formed. The control accuracy of this recording magnetic domain shape governs the recording density in high density recording.
As a known example in which the shape of the recording magnetic domain is controlled, Japanese Patent Laid-Open No. 3-222
No. 23 can be cited. 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 length and amplitude of the pulse train are set in the opposite phase of the recording code train immediately before the recording code train. According to the method of controlling according to the length, the pulse train is divided into three parts, and the pulse width of each pulse is changed to perform recording. Also,
Regarding the recording density in the radial direction, a track on a disk is divided into zones composed of a plurality of tracks, and the optical disk device in which the zones are recorded so that the recording density is the same is already disclosed in Japanese Patent Application No. -133819. However, here, the linear density in each zone on the disk cannot be made constant due to the recording / reproducing characteristics of the write-once optical disk, and the recording density in the zone on the inner circumference of the disk is different from that on the outer circumference. It is higher than the recording linear density.
Further, as shown in Japanese Patent Application No. 4-26511, test recording is performed to detect environmental temperature fluctuations, and magnetic domains of the same shape and size can always be formed without depending on the apparatus state or environmental temperature fluctuations. . In particular, by using a multi-pulse as a recording pulse and introducing a test recording method, the accuracy of recording control could be ± 0.02 μm in the track direction and ± 0.05 μm in the radial direction.

[0003]

In the above-mentioned prior art, since a laser light source having a short wavelength is used for high density recording, the energy density increases as the wavelength of light becomes shorter, and the spot The temperature near the center becomes high. Therefore, when test recording is performed on the disc, in order to search for the optimum power, recording is performed at a power higher than the standard condition.
Since that location must be completely erased, it must be erased at a higher power than standard conditions. As a result, the recording sensitivity of the disk fluctuates or the reproduction signal output decreases due to repeated recording / erasing in test recording, which may deviate from the desired optimum power, resulting in jitter or edge shift. As a result, it has been an obstacle to improving the recording density.

An object of the present invention is to suppress the reduction of the reproduction signal output due to the fluctuation of the recording sensitivity of the disc and the deterioration of the recording film by repeating the recording / erasing on the disc in the test recording, and to control the recording magnetic domain shape using the test recording. It is to improve the accuracy of the method and provide high-density magneto-optical recording.

[0005]

In order to achieve the above object, in recording in magneto-optical recording in which recording, reproduction and erasing are performed using at least a laser beam, a predetermined area is formed before user data is recorded. To perform the test recording, the test recording may be performed by a method in which the structural relaxation of the recording film due to the irradiation laser beam is unlikely to occur. Especially in test recording, since the optimum recording condition is searched by changing the laser power, there is a case where the disc becomes overpowered in the process. Considering the maximum temperature reached by the recording film during recording / erasing, the highest temperature is during erasing. For example, in the case where a magnetic domain having a width of 0.75 μm is formed, in order to completely erase the data, the erase width must be determined in consideration of the track offset of the device in consideration of the disc compatibility. In the test recording, since the recording is performed with a power higher than the standard in order to search for the optimum recording power, the magnetic domain width becomes wide. Therefore, in order to completely erase a wide magnetic domain, it is necessary to erase with a power higher than the standard condition, and the temperature of the recording film becomes high. As a result, the recording film undergoes structural relaxation, and the recording sensitivity changes. Therefore, when the user data is recorded, it is not recorded at the optimum power, which causes jitter and edge shift. Therefore, as a measure for the disk device side, it is necessary to suppress the temperature rise of the recording film so as to be as low as possible. Specifically, as a method in which the structural relaxation of the recording film is less likely to occur due to the irradiation laser light, test recording may be performed first in the test area provided in the outermost peripheral area of the disc. This is because the outer peripheral region has a higher linear velocity than the inner peripheral portion, and therefore the maximum attainable temperature during recording or erasing is low.
Therefore, the structural relaxation of the recording film is unlikely to occur. for that reason,
If the environmental temperature and the operating state of the device are unknown, first test recording is performed on the outer peripheral portion of the disk, the optimum conditions are found, and the result is used to perform test recording on the inner peripheral portion. . As the second method that is less likely to cause structural relaxation of the recording film due to the irradiation laser light, the power of the laser light used for performing test recording is first set between the power under the standard condition and the power lower than that. After making a test recording with the test result, if it is judged that the power is insufficient, a test recording is performed with a power higher than the standard condition, and more advantageously, with a power higher than the standard condition. It is preferable to perform test recording from a low set power. That is, it is necessary to prevent the temperature of the recording film from rising due to overpower. As a third method in which the structural relaxation of the recording film is less likely to occur due to the irradiation laser light, when the test recording is performed by changing the laser power or the pulse width, the influence of the heat applied to the recording film becomes uniform over the entire surface of the disk. To
Controlling at least one parameter selected from the pattern, pulse width, and laser power. This is because, for example, instead of changing the recording condition (for example, laser power or pulse width) for each sector, the scanning parameter is changed at random to perform the test recording, so that the usage condition of the disk is statistically uniform. It is a method to do. As a fourth method in which the structural relaxation of the recording film is less likely to occur due to the irradiation laser light, there is a method of conducting test recording after first confirming the presence or absence of information in the test area prior to the test recording. Although this is an abnormal end, there is a case where it cannot be erased due to an abnormality on the device even if it is always erased after recording as a test recording method. Assuming this case, an algorithm for erasing can be considered before performing test recording, but in that case, the state when the remaining data was recorded cannot be known, so erasing is performed assuming the worst case. Determine the conditions. In this case as well, it is overpowered. Therefore, this point is prevented by confirming the presence or absence of information and then determining the necessity of erasing. That is, this case is considered to be an extremely rare case. As the fifth method in which the structural relaxation of the recording film is less likely to occur due to the irradiation laser beam, the recorded magnetic domain to be erased is divided into a plurality of times to erase the information recorded in the test recording or the data recording. this is,
Since the maximum temperature reached by the recording film during erasing is proportional to the erase magnetic domain width, this is a method of preventing the maximum temperature reached by the recording film from increasing by performing erasing a plurality of times with a narrow width. Even if one of these methods is used, the effect can be seen, but in order to obtain a further effect, a synergistic effect is produced by combining a plurality of methods, and the effect can be increased.

[0006]

The maximum temperature of the recording film when the laser beam is irradiated can be lowered by devising the method of applying heat from the magneto-optical disk device to the disk. It is possible to suppress deterioration of characteristics. In particular, since the temperature of the recording film becomes highest during erasing by continuously irradiating the laser beam, the sequence of the disk device was determined so that the laser beam irradiation takes into consideration the temperature control of the recording film at this time.

[0007]

EXAMPLES Details of the present invention will be described with reference to examples.

First, FIG. 1 is a schematic view showing the sectional structure of the magneto-optical disk used in this embodiment. 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
Is. 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 the 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.

Next, FIG. 2 is a block diagram showing the configuration 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 780 nm. The recording / reproducing apparatus is a recording medium 1 for storing information.
01, an optical head 102 for realizing recording and reproduction, 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, the input data bit string (information) is the encoder 104
To the recording waveform generator 105, and the recording code string output from the encoder 104 is guided to the recording waveform generator 105.
The recording waveform obtained by the above 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 and converted into an electric signal. The signal is
It is input to the reproduction amplifier 110 and output to the waveform equalizer 111 and the input switch 112. The input switch 112 is a reproduction amplifier 110 or a waveform equalizer 1 according to a trial writing command signal.
11 is converted into a pulse signal indicating the presence or absence of the reproduction signal. The pulse signal is guided to the discriminator 115 and the PLL 114. The synchronization signal output from the PLL 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 synchronization 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 switches the output of the waveform equalizer 111 to the shaper 113, and starts a normal recording / reproducing operation. Even after the normal recording operation is started, the comparison discriminator 116 confirms that the difference of the reproduction code string from the recording code string is within the allowable range, and if it is not allowable, the trial write operation described above is started. Then, when the trial writing end signal is output, the regular recording operation is continued again. Further, the comparison discriminator 116
If you want to check the difference of the reproduced code string from the recorded code string,
The output of the input switch 112 can be detected more accurately when operated so as to output the signal of the reproduction amplifier 110. In these operations, similar operations can be realized without using the input switch 112. Comparison discriminator 116
Therefore, in order 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.

Therefore, data recording / reproduction was performed using this apparatus. An example of the waveform used for recording is shown in FIG. The pattern used was a repeating pattern of a shortest pattern (2Tw) and a longest pattern (8Tw) that was taken over by a (1,7) RLL modulation code. Then, the recorded data was reproduced, the difference between the signal amplitude of the shortest pattern and the signal amplitude of the longest pattern was detected, and the power at which the difference was zero was searched for. The method is shown in FIG. Alternatively, a method may be used in which the reference value of the signal amplitude is recorded in the RAM or the like in advance and the value is compared with the value obtained by the test recording. The test recording was performed from the outermost peripheral portion (r = 60 mm) of the disc. The disk is 5.25 inches in size and has a format compatible with the ZCAV system. The power of the pattern shown in FIG. 3 on the test track set in the outermost zone is ± 3% ± 7 from the standard power recorded by the device.
It was recorded while changing to ± 10%. Among these, the maximum temperature when the recording domain (width: 0.87 μm) formed with 10% higher power is completely erased by continuous light is 290 ° C. On the other hand, at the innermost circumference position (r = 30 mm), 35
It was 0 ° C. Here, the rotation speed of the disk is 3000 rp
m, the wavelength of the laser light is 780 nm. The operation of completely erasing the domain recorded with this 10% higher power is
Recording was performed on the data area with optimized power in the test track repeated ⁶ times. As a result, power was insufficient at the innermost peripheral position, and the jitter increased by about 20% to 59%. On the other hand, no increase in jitter was observed at the outermost position. Therefore, a test recording method is used in which the recording condition is set on the track at the outermost peripheral position, and the optimum power is confirmed on the test track at the innermost peripheral position based on the obtained condition. At the innermost circumference, the power obtained at the outermost circumference was converted to the inner circumference, and the power was varied within a range of ± 5% centering on the power and examined. After performing this test recording 10 ⁶ times, user data was recorded at the innermost circumferential position under the conditions obtained from the test recording. The jitter could be suppressed to 5% more than when recorded under the conditions obtained from the initial test recording. However, it can be said that good recording could be performed without causing a big problem on the margin of the apparatus. In addition, the test recording for confirmation at the innermost circumference was performed starting from -5%, which is lower than the optimum power when changing the power based on the results obtained at the outermost circumference. The method of finding the power at which the difference of zero is zero was used. as a result,
When recording was performed using the recording conditions obtained after repeating 10 ⁶ test recordings, there was no increase in jitter compared to when recording was performed under the conditions obtained from the initial test recording.

Next, another embodiment will be described. The disk and device used are the same as in the previous embodiment. Here, as the test recording method, it was first confirmed whether the test track was first erased before the test recording and then the test recording was performed, and whether or not the test pattern was recorded on the test track before the test recording. Comparison will be made when a test recording is made later. Here, the first erasure is based on the assumption that the test recording ends abnormally due to a malfunction of the disk device. Since this is probabilistically equal to nothing, the abnormal termination of the device was confirmed by confirming the presence or absence of the pattern instead of erasing it suddenly. The power used for erasing is the magnetic domain recorded at 10% increase of the standard condition at the use environment temperature of 50 ° C.
It was set in consideration of the case of complete erasing at the operating environment temperature of 0 ° C. The data zone is the innermost position. As a result, the test recording was repeated before erasing and then the test recording was repeated 10 ⁶ times. When the data area was recorded based on the result, the jitter increased by 45% from the initial value to 84%. On the other hand, reproduction was performed in advance to confirm the presence or absence of the test pattern, and then test recording was performed. In this case, when recording was performed in the data area under the recording conditions obtained after the test was repeated 10 ⁶ times, the increase in jitter could be suppressed to 20%. Further, by combining with a method of performing test recording from the outer peripheral portion, estimating the optimum condition in the inner peripheral portion, and then performing test recording in the inner peripheral portion, this increase in jitter can be suppressed to zero.

Still another embodiment will be described. The disk and device used are the same as in the previous embodiment. Here, as a test recording method, in order to erase the recorded test pattern, a method of applying an offset and erasing each half is used. As a result, in the case of erasing by the usual method, when recording was performed under the recording conditions obtained after 10 ⁶ times of test recording, the jitter increased by 20%. On the other hand, in the test recording method using the method of erasing by dividing by the offset of 0.1 μm, no increase in jitter was observed after recording under the recording conditions obtained after 10 ⁶ test recordings. . This is because not only the maximum temperature of the recording film is decreased but also the light spot position during erasing is different.

Still another embodiment will be described. The disk and device used are the same as in the previous embodiment. Here, as a test recording method, a method of using a test track is devised. The test track is divided into a plurality of sectors, and the case of 32 sectors is considered here. When recording is performed by changing the recording condition, for example, the laser power, a test recording method is used under one power condition for each sector. In that case, test recording was carried out by a method in which the same power condition was randomized so as not to concentrate in a specific sector, or a recording pattern of various power conditions was randomly recorded in one sector. Here, the power condition that the condition of recording in a certain sector is always the same,
In particular, when test recording was performed by a method in which the sector was fixed so that the condition of 10% increase, the jitter increased by 20% when recorded under the recording conditions obtained after 10 ⁶ test recordings. In contrast, when the test recording without fixing the conditions to be recorded in a sector, was recorded with the resulting recording condition after the test recording of ¹⁰⁶ times, an increase in jitter 15
It could be suppressed to%. Furthermore, in the test recording method in which patterns with different power conditions are randomly recorded in one sector, when recording was performed under the recording conditions obtained after 10 ⁶ test recordings, the increase in jitter could be suppressed to 10%.

[0014]

According to the present invention, fluctuations in recording sensitivity can be suppressed in a test area where the number of recording / erasing repetitions is the largest, and therefore the accuracy of test recording can be greatly improved, so that the control of the high-precision recording magnetic domain shape can be performed. As a result, super high density magneto-optical recording can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of a manufactured magneto-optical disk.

FIG. 2 is a block diagram showing the configuration of a magneto-optical disk drive.

FIG. 3 is a waveform diagram of a recording pulse.

FIG. 4 is an explanatory diagram showing the principle of a recording condition determination method in test recording.

[Explanation of symbols]

101 ... Recording medium, 102 ... Optical head, 103 ... Trial writer, 104 ... Encoder, 105 ... Recording waveform generator, 10
6 ... APC, 107 ... Laser driver, 108 ... Laser,
109 ... Light receiver, 110 ... Reproducing amplifier, 111 ... Waveform equalizer, 112 ... Input switcher, 113 ... Shaper, 114 ...
PLL, 115 ... Discriminator, 116 ... Comparison discriminator, 117
… Decoder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Doninaga, 1-280 Higashi Koikeku, Kokubunji City, Tokyo Metropolitan Research Center, Hitachi, Ltd. (72) Takeshi Maeda 1-280 Higashi Koikeku, Tokyo Kokubunji City Hitachi, Ltd. (72) Inventor Fumio Kugiya 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Inside Hitachi Central Research Laboratory

Claims (7)

[Claims] 1. Recording / reproducing using at least a laser beam,
In recording in the magneto-optical recording for erasing, the test recording was performed by a method in which the structure of the recording film is not easily relaxed by the irradiation laser beam in order to perform the test recording in a certain area before recording the user data. A recording method of magneto-optical recording characterized by the above. 2. A magneto-optical recording according to claim 1, wherein a test recording is first performed in a test area provided in an outermost peripheral area of the disk as a method in which structural relaxation of a recording film is less likely to occur due to irradiation of laser light. Method. 3. The method according to claim 1, wherein the structure of the recording film is less likely to be relaxed by the irradiation laser light, the power of the laser light used for the test recording is first a power under a standard condition and a power lower than that. After making a test recording with the power set during, and seeing the result,
When it is judged that the power is insufficient, test recording is performed with a power higher than the standard condition, and more advantageously, the test recording is performed from a low set power to perform a test recording with a power higher than the standard condition. Method. 4. The method according to claim 1, wherein the structure of the recording film is less likely to be relaxed by the irradiation laser light, the influence of heat on the recording film when test recording is performed by changing the laser power or the pulse width. A recording method of magneto-optical recording in which at least one parameter selected from a pattern, a pulse width, and a laser power is controlled so as to be uniform on the entire surface of the disk. 5. The magneto-optical recording method according to claim 1, wherein the structure of the recording film is less likely to be relaxed by the irradiation laser beam, and the test recording is performed after first confirming the presence or absence of information in the test area prior to the test recording. Recording method. 6. The method according to claim 1, wherein the recording magnetic domain to be erased is divided into a plurality of times in order to erase the information recorded in the test recording or the data recording, as a method in which the structural relaxation of the recording film is less likely to occur by the irradiation laser beam. Recording method of magneto-optical recording performed by. 7. A method in which the structural relaxation of the recording film is less likely to occur by the laser light irradiated in claim 2, 3, 4, 5 or 6 is a combination of a plurality of types among the methods in which the structural relaxation of the recording film is less likely to occur. Recording method of magneto-optical recording used.