JPH1139803A - Optical recording medium, optical recording method and optical recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the optimum recording power by keeping a defective location off use during the period of a test recording. SOLUTION: During the period of a test recording, a control circuit 20 extracts a sector address in a reproduced signal from a data detection means 19 and when the address coincides with a sector address of a defective sector stored in a memory 21, a control signal is outputted to a power setting means 24 for the test recording. When receiving the control signal, a power setting means 24 for the test recording sets a power for the sector involved so as not to record a test pattern. The control circuit 20 outputs sector address information for the defective sector stored in the memory 21 for a buffer memory 26 for recording data. Thus, the buffer memory 26 records fault formation into an optical disc 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, an optical recording method, and an optical recording apparatus, and more particularly, to a method and apparatus for test recording an optical disk.

[0002]

2. Description of the Related Art In recent years, an optical recording / reproducing method which satisfies various requirements including a high density, a large capacity, a high access speed, and a high recording / reproducing speed, a recording apparatus, a reproducing apparatus and a recording medium used therein. Efforts have been made to develop.

[0003] Among a wide range of optical recording / reproducing methods, the magneto-optical recording / reproducing method allows information to be recorded and then erased, and that new information can be recorded again and again. Since it has excellent features, it can be said that it is the most practical reproduction method.

A magneto-optical recording disk (medium) used in this magneto-optical recording / reproducing method has a magnetic film composed of one or more layers as a layer for recording. The magnetic film is a perpendicular magnetization film (perpendicul) with high recording density and high signal strength.
ar magnetic layer or layers) have been developed and used. Such a magnetized film is, for example, an amorphous G
dFe, GdCo, GdFeCo, TbFe, TbC
o, TbFeCo or the like. The perpendicular magnetization film generally has a concentric or spiral track, and information is recorded on the track.

[Principle of Mark Formation] In the formation of marks (information), coherence, which is excellent in space and time, which is a characteristic of laser, is advantageously used and is determined by the wavelength of laser light. The beam is narrowed down to a spot as small as almost the diffraction limit. The focused laser light is applied to the track surface and heats the recording film to form a mark having a diameter of 14 μm or less on the recording film, thereby recording information. In optical recording, a recording density of up to about 10 ⁸ marks / cm ² can be theoretically achieved. This is because the laser beam can concentrate to a spot having a diameter as small as about the wavelength.

[0006] In magneto-optical recording, a laser beam is focused on a perpendicular magnetization film and heated. in the meantime,
A recording magnetic field Hb in a direction opposite to the initialized direction is externally applied to the heated portion. Then, the coercive force Hc (coersivity) of the locally heated portion decreases and becomes smaller than the recording magnetic field Hb. As a result, the magnetization of that portion is aligned in the direction of the recording magnetic field Hb. In this way, a reversed magnetized mark is formed.

[Principle of magneto-optical reproduction] Light is an electromagnetic wave having an electromagnetic field vector that normally diverges in all directions on a plane perpendicular to the optical path. When the light is converted to linearly polarized light and illuminates the perpendicular magnetic film, the light is reflected at the surface or transmitted through the perpendicular magnetic film. At this time, the plane of polarization rotates according to the direction of magnetization. This spinning phenomenon is called the magnetic Kerr effect or the magnetic Faraday effect.

For example, if the plane of polarization of the reflected light is rotated by θK degrees with respect to the magnetization in the initialization direction, it is rotated by −θK degrees with respect to the magnetization in the recording direction. Therefore, if the axis of the optical analyzer (polarizer) is set perpendicular to the plane inclined by θK degrees, light reflected from the mark magnetized in the initialization direction cannot pass through the analyzer. On the other hand, the light reflected from the mark magnetized in the recording direction is multiplied by (sin2θK) ² , passes through the analyzer, and is captured by the detector (photoelectric conversion means). As a result, the mark magnetized in the recording direction looks brighter than the mark magnetized in the initialization direction, and generates a strong electric signal in the detector. Therefore, the electric signal from the detector is modulated according to the recorded information, and the information is reproduced.

[Light Intensity Modulation Overwriting] However, in the conventional magneto-optical recording, since heat by a laser beam is used for the recording, it is necessary to erase once when re-recording the recorded portion. In magnetic recording, so-called overwriting, in which a new signal is recorded without erasing, is possible, whereas in magneto-optical recording, there is a disadvantage that re-recording takes time.

However, if the direction of the recording magnetic field Hb can be freely modulated as required, overwriting becomes possible. However, it is impossible to modulate the direction of the recording magnetic field Hb at a high speed. For example, when the recording magnetic field Hb is a permanent magnet, it is necessary to mechanically invert the direction of the magnet, but it is impossible to invert the magnet at high speed. Even when the recording magnetic field Hb is an electromagnet, it is difficult to modulate the direction of a large current at such a high speed.

However, technological progress has been remarkable, and magneto-optical recording capable of overwriting only by modulating the intensity of a light beam to be irradiated without modulating the intensity of the recording magnetic field Hb according to binary information to be recorded. A method, an overwritable magneto-optical recording medium used for the method, and an overwritable recording device also used for the method have been invented and a patent application has been filed (Japanese Patent Laid-Open No. 62-175948 = DE3,619,618).
A1 = USP5,239,524) (hereinafter referred to as prior invention).

In the above-mentioned prior invention, a memory layer (hereinafter, referred to as an M layer) basically composed of a magnetic thin film capable of perpendicular magnetization.
And a recording layer (hereinafter, referred to as a W layer) composed of a magnetic thin film capable of perpendicular magnetization. Both layers are exchange-coupled, and only the magnetization of the W layer is changed at room temperature without changing the magnetization direction of the M layer. Is used, and an overwritable multi-layer magneto-optical recording medium that can be oriented in a predetermined direction is used. Then, information is represented by the direction of magnetization in the M layer and recorded.

The M layer and the W layer are generally made of an alloy of a rare earth metal and a transition metal. The exchange coupling force acts in a direction to align the sublattice magnetizations of the transition metal and the sublattice magnetization of the rare earth metal. In this medium, the magnetization direction of the W layer can be aligned in one direction by the initialization means. In addition, at that time, the magnetization direction of the M layer does not reverse, and the magnetization direction of the W layer once aligned does not reverse even when it receives the exchange coupling force from the M layer. The direction of magnetization of the layer does not reverse even when subjected to exchange coupling force from the W layer. The W layer has a lower coercive force Hc and a higher Curie point Tc than the M layer.
With.

According to the recording method of the prior invention, in the recording medium, only the magnetization direction of the W layer is aligned in one direction by the initialization means before recording. The initializing means may use an external magnetic field, or the medium itself may have the initializing means. Then, the medium is irradiated with a laser beam pulse-modulated according to the binarized information. The intensity of the laser beam has a high level PH and a low level PL. This low level PL is higher than the reproduction level PR for irradiating the medium during reproduction. At this time, the recording magnetic field Hb is applied to the medium portion irradiated with the laser beam.
When the initialized medium is irradiated with a low level PL laser beam, the temperature of the medium rises and the coercive force of the M layer becomes very small or extremely zero. It becomes zero
This is when the temperature of the medium is equal to or higher than the Curie point of the M layer.
At this time, the coercive force of the W layer is sufficiently large and the recording magnetic field Hb
Will not be inverted. Then, since an exchange coupling force acts on the M layer from the W layer, the sub-lattice magnetization of the M layer follows the initialized sub-lattice magnetization of the W layer. When the irradiation of the laser beam is stopped in this state, the temperature of the medium drops, but the direction of the sublattice magnetization of the M layer does not change.

On the other hand, when the medium is irradiated with the high-level PH laser beam, the temperature of the medium rises more than when the low-level PL laser beam is irradiated, exceeds the Curie point of the M layer, and the coercive force of the M layer becomes zero. The coercive force of the W layer becomes very small or extremely zero. The magnetization of the W layer having a reduced coercive force is reversed by the recording magnetic field Hb. When the laser beam irradiation stops, the temperature of the medium drops, and when the temperature falls below the Curie point of the M layer, the magnetization of the M layer appears following the sublattice magnetization of the inverted W layer. Even if the medium temperature further decreases, the direction of the sublattice magnetization of the M layer does not change. At this time, the direction of the sublattice magnetization of the M layer is in the opposite direction to the case where the low level PL laser beam is irradiated.

As described above, the low level PL and the high level P
The laser beam irradiation of H 2 determines the magnetization direction of the M layer without depending on the original magnetization direction of the M layer.
There is no need to erase the layer before re-recording, and overwriting is possible. The medium used for the light modulation overwrite method has a multilayer structure including an M layer and a W layer. The M layer is a magnetic layer having a large coercive force at room temperature and a low magnetization reversal temperature. The W layer is a magnetic layer having a relatively higher magnetization reversal temperature than the M layer. The M layer and the W layer may themselves be composed of a multilayer film. In some cases, an intermediate layer may be present between the M layer and the W layer. Further, an initialization layer for initializing the W layer may be provided adjacent to the W layer.

[Pulse Train Recording] In optical recording, marks are used as a method of recording and reproducing information. Pit position recording using the position of the mark as information and pit edge recording using the edge position of the mark as information are two types.
There are different types of recording methods. In particular, in pit edge recording, since both the front end and the rear end of a mark are used, the recording density is higher than in pit position recording. When performing pit edge recording, it is necessary to strictly control the mark size. However, optical recording is a simple 2
In the pulse of the value, the rear end of the mark becomes larger than the front end due to the accumulation of heat, and a so-called teardrop-shaped mark is formed.

Accordingly, pulse train recording has been proposed as a recording correction method for correcting a mark shape by modulating a recording laser pulse as shown in FIG. In this pulse train recording, the laser power is Pa, Pw1, Pw2.
The recording is performed based on the ratio of three values determined from the thermal characteristics.

When a pulse train is applied to the above-mentioned light intensity modulation overwriting, Pa is set to a low level P.
Lw corresponds to the laser power of L, and Pw1 and Pw2 correspond to the laser power of the high level PH.

[Test Recording] When actually recording on a magneto-optical disk, it is necessary to finely adjust the laser power in accordance with the recording sensitivity of the disk and the environmental temperature in order to optimize the mark shape. Become. However, some first-generation magneto-optical disk recording apparatuses perform recording without adjusting the laser power. Also, the second
The magneto-optical disk recording device called the generation performs test recording and adjusts sensitivity before recording information. A test area for performing test recording is prepared in advance on the second generation magneto-optical disk.

In the test recording in the pulse train described above, usually, the ratio of the three values of the laser powers Pa, Pw1 and Pw2 is kept constant and the power is changed variously. The method for determining the optimum power is, for example, the number of error corrections (error co
Generally, a method of measuring the rrection cord) and an error rate, a method of recording a dense pattern and a coarse pattern, and determining the recording power so that the center of the signal amplitude coincides with the recorded pattern.

The test area is divided into sections called sectors, like the normal data area. Test recording is usually performed by changing the power for one sector or a plurality of sectors.

An example of a test recording method for measuring an error rate will be described in detail. First, laser power Pa, Pw
A ratio of 1 and Pw2 is set, and recording is performed in a certain sector with low power. When recording is performed at a very low power, a mark is not formed normally due to insufficient power, and the error rate is naturally measured poorly. Next, recording is performed in another sector while slightly increasing the power while keeping the ternary ratio constant, and the error rate is measured. As this operation is repeated, the error rate gradually improves. As you increase your power further,
This time, the recording becomes excessive, and the error rate again deteriorates. That is, there is a range in which the error rate is good (for example, the error rate is 1 × 10 ⁻⁴ or less) between the recording underscore and the recording overspot. This range is called a recording power margin. Usually, the power near the center of the recording power margin is set as the optimum recording power.

[0024]

However, if a scratch or defect exists in the test area of the disk, the error rate naturally deteriorates. An ordinary optical recording apparatus cannot determine whether the deterioration of the error rate is caused by a recording power condition such as insufficient recording or excessive recording, or a defect or a defect of a disk. For this reason, the recording power margin was erroneously measured, and the optimum recording power could not be determined. For example, in the test recording method described above, after finding the lower limit of the margin on the low power side, if a defective sector is measured in the process of gradually increasing the power, the defective sector is determined to be the upper limit of the margin on the high power side. Estimate the power margin narrower than it actually is. In this case, the recording power determined as the margin center is
It will be lower than the true margin center value. If the recording power is not set at the center of the true margin, the recording power may be affected by temperature fluctuations or the like, and normal recording may not be performed.
In particular, when such a test recording method is used for light intensity modulation overwriting, if the power is set low, erasure failure occurs, and there is a problem that overwriting cannot be performed.

Further, in the case of an overwritable magneto-optical disk provided with an initialization layer for initializing the W layer, the magnetization of the initialization layer must always be directed to a predetermined direction. When the laser beam is irradiated with very high power, the direction of magnetization may be reversed. If the magnetization of the initialization layer is reversed, it cannot be returned by the normal operation, and that portion cannot be used.

As described above, not only a defect existing from the beginning but also a portion which becomes unusable as the disk is used arises. This is not limited to overwritable magneto-optical discs, but also occurs in ordinary optical discs due to scratches or dust attached later.

The present inventor has found that the above-mentioned problem can be solved by recording defect information in the test area on a recording medium and not using a defective portion.

The present invention has been made on the basis of the above-described conventional problem understanding and research results. It is an object of the present invention to prevent the use of a defective portion at the time of test recording so that the optimum recording power can be reduced. An object of the present invention is to provide an optical recording medium, an optical recording method, and an optical recording device that can be determined.

[0029]

In order to achieve the above object, an optical recording medium according to the present invention has a mark formed by irradiating a laser beam intensity-modulated according to binary information to be recorded. A disc-shaped optical recording medium on which information is recorded, wherein defect information of an area where test recording is performed is recorded. The optical recording medium according to the present invention is a magneto-optical recording medium capable of overwriting. Further, an optical recording method according to the present invention uses the above optical recording medium in an optical recording method of recording information on an optical recording medium by modulating at least a light intensity to be irradiated into a high level and a low level. When performing test recording in a test area, defect information is read and not used for a portion where a defect exists. Further, the optical recording apparatus according to the present invention comprises: a means for rotating a disk-shaped optical recording medium; a laser light source for generating a laser beam for forming a mark on the optical recording medium and recording information; In an optical recording device comprising a modulation unit that irradiates the optical recording medium with intensity-modulated the laser beam according to power binary information, a unit that detects information recorded in a test area,
Means for determining whether there is a defect in the test area based on a detection signal from the detection means, and means for recording the defect information on a medium when the presence of the defect is confirmed by the determination means. It is characterized by the following.

In the present invention, since the defect information is recorded on the optical recording medium, if this defect information is read and the defective portion is not used, the recording power margin is not erroneously measured and the optimum recording is performed. Power can be determined.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a sectional view showing an example of the configuration of a magneto-optical disk capable of overwriting light intensity modulated according to the present invention, and FIG. 2 is a diagram showing a manufacturer area, a test area, and a user data area of the disk. In these figures, a magneto-optical disk 10 includes a dielectric layer 2, a memory layer 3, an intermediate layer 4, a recording layer 5, and a dielectric layer 6 as a protective layer which are sequentially laminated on a substrate 1. The magneto-optical disk 10 includes a manufacturer area 7, a test area 8, and a user data area 9. The manufacturer area 7 is provided at the outermost circumference and the innermost circumference of the normal disk, and is an area used by the manufacturer for recording a manufacturing date, a manufacturing lot, an inspection date, an inspection result, and the like.
In the test area 8, the user data area 9 is divided into a plurality of bands (also referred to as zones) in the radial direction of the disc, and is an area where a user records data. The test area 8 is used at the time of test recording, and is provided adjacent to the inner or outer peripheral side of the user data area 9 of each band.

As the substrate 1, for example, a thickness of 1.2 mm,
A disk-shaped glass substrate with a tracking groove having a diameter of 130 mm (track pitch 1.2 μm) is used.
The dielectric layer 2 is formed of SiN and has a thickness of 70 nm. The memory layer 3 is made of TbFeCo.
It has a thickness of 0 nm. The intermediate layer 4 is made of GdFeCo and has a thickness of 10 nm. The recording layer 5 is Tb
It is made of DyFeCo and has a thickness of 40 nm.
The dielectric layer 6 is formed of SiN and has a thickness of 70 nm. The memory layer 3 is a TM (Transition Metal:
The transition layer has a rich composition, and the recording layer 5 has a RE (Rare earth) rich composition having a compensation temperature between room temperature and Curie temperature.

FIG. 3 is a block diagram of an optical recording apparatus according to the present invention. Note that, in the present embodiment, an example of a method for performing test recording based on an error rate is shown. The magneto-optical disk 10 is rotated by a disk drive unit 12 including a drive motor and the like. Laser driver 13
A laser beam emitted from a recording / reproducing laser diode (laser light source) 14 driven by the laser beam passes through a polarizer 15 and is converted into linearly polarized light, and is transmitted or reflected by a beam splitter 16 to collect a laser beam focusing unit 17. The light is condensed and irradiated on the magneto-optical disk 10. Also,
After being reflected from the magneto-optical disk 10, the reproduction light is condensed by the laser condensing means 17, reflected or transmitted by the beam splitter 16, transmitted by the analyzer 18, and detected by the data detection means 19, and detected by the data detecting means 19. Is converted to

20 is a control circuit, 21 is a memory, 22 is an error rate determining means, 23 is a determining means, 24 is a test recording power setting means, 25 is a recording power determining means,
Reference numeral 6 denotes a record data buffer memory as a means for recording defect information on a medium. When a reproduction signal (output from the data detection means 19) from the recording area of the defect information on the magneto-optical disk 10 is input, the control circuit 20 stores the defect information (sector address of the defective sector) in the memory 21.
To memorize. When the determination means 23 determines that a defect exists during test recording, the defect information is stored in the memory 21.
The data is sent to the recording data buffer memory 26 and recorded on the magneto-optical disk 10. The defect information stored in the memory 21 is controlled so that recording is not performed on a defective sector of the disk.

Next, a defective sector is identified by test recording,
An example of a method for recording on a disc will be described with reference to FIG. The loaded magneto-optical disk 10 is rotated by the disk drive means 12, and the disk information is read. The test recording power setting means 24 sets the recording power to a low level with the same ratio as the reference power value, and records a test pattern in the test area 8. At this time, the defective sector is not used. The recorded pattern is reproduced, and the error rate measuring means 2
The error rate is measured according to 2. Repeat with another sector while gradually increasing the power. A power range with a good error rate is obtained from the error rate measurement result. The recording power is determined by the recording power determination means 25 near the center of the power range where the error rate is good, and recording is performed in a sector where the error rate is poor with the recording power. The information recorded in this sector is reproduced, and when a good error rate is obtained, it is determined that there is no defective sector due to a defect, a scratch, an inversion of the initialization layer, or the like, which occurs later.

When it is determined in the above procedure that test recording has been performed in a good sector, the recording power is optimized and the recording data buffer memory 26 records information to be recorded in the user data area 9. I do.

If the error rate is still bad after re-recording, the sector is determined to be a bad sector, the recording data buffer memory 26 records defect information, and test recording is performed again without using the sector.

Here, reading and writing of defect information will be described. (1) Reading of defect information At the time of test recording, first, each predetermined volume information recording area is accessed, defect information of the disc is read, and recorded in the memory 21. The defect information recording area is the D
Any of the MA area, the manufacturer area 7 or a part of the test area 8 may be used. In accordance with the defect information stored in the memory 21, the control circuit 20 controls so as not to perform recording on the defective sector. (2) Writing of Defect Information The control circuit 20 detects the sector address from the reproduction signal from the data detection means 19 (detects the sector address of the sector currently irradiated with the beam). Determination means 2
3 outputs a control signal to the control circuit 20 when the sector on which the test recording is performed is determined to be a defective sector. When receiving the control signal, control circuit 20 receives the previously detected sector address (that is, the defective sector address).
Is stored in the memory 21. In the next test record,
Similarly to the above-described "reading of defect information", control is performed so that test recording is not performed in the sector stored in the memory 21. The control circuit 20 includes a print data buffer memory 26.
, The sector address information of the defective sector stored in the memory 21 is sent. When a sector address for test recording is detected, the recording data buffer memory 26
To output a test pattern stored in advance, and record it on the optical disk 10 as defect information.

[0039]

As described above, according to the optical recording medium, the optical recording method, and the optical recording apparatus of the present invention, even if there is a flaw or defect in the test area of the disk, defect information is recorded. Since the defective portion is not used, the optimum recording power can be determined by test recording without estimating the recording power margin narrower than the actual one. Further, even in the case of using for light intensity modulation overwriting, since the power is not set low, overwriting can be performed stably without causing erasing failure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of the configuration of a magneto-optical disk capable of performing light intensity modulation overwriting according to the present invention.

FIG. 2 is a diagram showing a manufacturer area, a test area, and a user data area of the disc.

FIG. 3 is a block diagram showing a configuration of an optical recording device according to the present invention.

FIG. 4 is a diagram showing recording pulses in conventional pulse train recording.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... substrate, 2 ... dielectric layer, 3 ... memory layer, 4 ... intermediate layer,
5 recording layer, 6 dielectric layer, 7 manufacturer area, 8 test area, 9 user data area, 10 magneto-optical disk, 12 disk drive means, 13 laser driver, 14 laser light source, 15 ... polarizer, 16 ... beam splitter, 17 ... laser beam condensing means, 18 ... analyzer, 19 ... data detecting means, 20 ... control circuit, 21 ... memory, 22 ... error rate measuring means, 23 ... discriminating means,
24: test recording power setting means, 25: recording power determining means, 26: recording data buffer memory, 30 ...
Reflected signal detection means.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 20/18 572 G11B 20/18 572C 572F

Claims (4)

[Claims] 1. A disk-shaped optical recording medium on which a mark is formed and information is recorded by irradiating a laser beam intensity-modulated according to binarized information to be recorded, wherein an area for performing test recording is provided. An optical recording medium characterized by recording defect information. 2. The optical recording medium according to claim 1, wherein the optical recording medium is an overwritable magneto-optical recording medium. 3. An optical recording method for recording information on an optical recording medium by modulating at least the intensity of light to be irradiated to a high level and a low level, using the optical recording medium according to claim 1 or 2. An optical recording method, wherein when performing test recording in a test area, defect information is read and a portion where a defect exists is not used. 4. A means for rotating a disk-shaped optical recording medium, a laser light source for generating a laser beam for forming a mark on the optical recording medium and recording information,
Means for modulating the intensity of the laser beam according to the binarized information to be recorded and irradiating the laser beam onto the optical recording medium, wherein the means for detecting information recorded in the test area; Means for determining whether there is a defect in the test area based on a detection signal from the means, and means for recording the defect information on a medium when the presence of the defect is confirmed by the determination means. An optical recording device characterized by the following.