JP2003317338A - Magneto-optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium of a magnetic domain expandable reproducing system improved in tracking performance and reproduc ing characteristics. <P>SOLUTION: In the magneto-optical recording medium of the magnetic domain expandable reproducing system, a sample servo system is used for the tracking servo of laser light to be used for recording/reproducing information, and a data area is provided behind a servo area in a tracking direction. This, substrate forms of respective areas are separately designed such that a servo signal to be generated from the servo area and a recording mark to be formed in the data area can be optimal, respectively. As a result, the magneto-optical recording medium of the magnetic domain expandable reproducing system improved in the tracking performance and the reproducing characteristics is obtained. <P>COPYRIGHT: (C)2004,JPO

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 using a sample servo system for tracking servo, and more specifically, a magneto-optical recording system of the type in which the magnetic domain is expanded and reproduced by using the sample servo system. Regarding the medium.

[0002]

2. Description of the Related Art In optical discs, when recording / reproducing information, in order to scan a laser beam used for recording / reproducing information to an appropriate position on a track, grooves or pits are preliminarily formed on the circumference of a substrate. There is. By utilizing the amount of light reflected from these grooves or pits, the laser light can be constantly scanned at a predetermined position on the circumference. For example, when a two-divided detector is used to monitor the amount of reflected light, the difference signal of the two-divided detector becomes 0 when the laser light is scanning between two pits or the center of the groove. However, if the laser light deviates from those positions, the difference signal of the two-divided detector becomes non-zero. The difference signal increases in proportion to the amount of laser light deviation. Therefore, by driving and scanning the laser light so that the difference signal of the two-divided detector is always zero, the laser light can be made to follow a predetermined track position on the circumference.

There are two types of tracking servo systems for scanning an optical beam on the optical disk by utilizing the above-mentioned amount of reflected light, a continuous servo system and a sample servo system. The former is a method of scanning laser light while constantly monitoring the amount of reflected light. In the latter method, the amount of reflected light is monitored only for a limited period of time, and in other time zones, for example, when information is being recorded / reproduced, it is based on the amount of reflected light previously monitored. Scanning is performed.

In a magneto-optical disk, additional write information such as user data is recorded with two types of magnetic marks having different magnetization directions by changing the magnetization direction of a magnetic domain recorded in a recording layer using laser light and an external magnetic field. To create. In the case of a magneto-optical disk, in order to increase the recording density, it is necessary to narrow the track interval (hereinafter referred to as the track pitch) and the recording mark interval (hereinafter referred to as the bit pitch). However, if the track pitch or bit pitch becomes narrower than the spot diameter of the laser light (λ / 2NA λ: laser wavelength, NA: numerical aperture of the focusing lens), multiple recording marks will be inserted in the light spot and the recording marks will be separated. There is a problem that can not be done.

As one means for solving this problem, a magneto-optical super-resolution (MSR: Magnetic Super)
Resolution) reproduction method. By utilizing the temperature distribution in the spot of the laser light and the magnetization characteristic with respect to the temperature of the recording film, the signal reproduction area can be effectively narrowed without reducing the spot diameter of the laser light. Therefore, using the magneto-optical super-resolution reproduction method,
It becomes possible to independently detect minute magnetic domains having a size exceeding the resolution of laser light. However, in the magneto-optical super-resolution reproduction method, the amplitude of the reproduction signal is reduced because the light spot area that contributes to the reproduction signal is reduced, and minute recording marks are reproduced with a sufficient signal-to-noise ratio (S / N). Will be difficult to do.

As a method for solving the problem in the magneto-optical super-resolution reproducing system, a magnetic domain expansion reproducing system (MAMMOS: Magnetic Am) disclosed in Japanese Patent Laid-Open No. 8-7350.
proofing Magneto Optical
System). The magnetic domain expansion reproducing method is a method of irradiating the magnetic domain transferred from the recording layer to the reproducing layer with a laser beam to expand the reproduced magnetic domain to the reproducing layer and reproduce. By using this method, an amplified reproduction signal can be obtained even with a minute recording mark, and information can be reproduced with a sufficient S / N. Therefore, by using the magnetic domain expansion reproducing method, it is possible to realize ultra-high density recording on the magneto-optical recording medium.

[0007]

As described above, the magnetic domain expansion reproducing method enables ultra-high density recording of a magneto-optical recording medium, and therefore it is expected to commercialize a magneto-optical recording medium suitable for this method. . In order to optimize the magneto-optical recording medium for this method, it is necessary to consider the magnetization characteristics of the magnetic layer, the physical format for tracking, and the tracking servo method. It is an object of the present invention to provide a magneto-optical recording medium having a physical format optimized for tracking in a magnetic domain expansion reproducing system.

[0008]

According to the present invention, a recording layer in which information is recorded as magnetic domains, and a reproducing layer in which the magnetic domains recorded in the recording layer are transferred and enlarged by irradiation of laser light during reproduction, A magneto-optical recording medium having a substrate in which an area for generating a tracking signal and a recording / reproducing area are defined, and the tracking signal generating area and the recording / reproducing area are formed at different positions in the track direction. A magneto-optical recording medium is provided.

In a magneto-optical recording medium using the magnetic domain expansion reproducing method, a change in magnetic characteristic with respect to a temperature distribution in a spot of a laser beam is utilized at the time of reproducing information. According to the research by the present inventor, the reproducing performance of the magneto-optical recording medium using the magnetic domain expansion reproducing method is greatly influenced by the shape of the substrate. The cause is that the flow of heat changes depending on the shape of the substrate such as the groove, which causes a unique temperature distribution, and the shape of the wall of the groove changes the leakage magnetic field from the recording layer to the reproducing layer. Can be considered.

The reproducing performance of the magnetic domain expansion reproducing system is influenced by the shape of the recording mark. Since the temperature distribution in the spot of laser light shows a circular or elliptical isotherm, in order to smoothly transfer and expand the magnetic domain of the recording layer from the center of the spot with high temperature, the shape of the recording mark on the recording layer should be It has been found that it is appropriate that the shape of the laser beam spot is as close as possible.

When the continuous servo system is used for the tracking servo of the laser light, a groove for the laser light to follow the recording track is formed. This groove is formed with an appropriate width, depth, and inclination in order to generate a servo signal. On the other hand, as an example for forming an address, it is formed in a wobble shape as shown in FIG. 6A. Can be considered. However, such wobbled grooves limit the shape of recording marks formed in or between the grooves.

In the magneto-optical recording medium of the present invention, the sample servo system is used for the tracking servo of the laser light used for recording / reproducing information, and the tracking signal generating area and the recording / reproducing area are provided in different areas in the track direction.
By doing so, the substrate shape of each area can be designed separately so that the servo signal generated from the tracking signal generation area and the recording mark shape formed in the recording / reproducing area are optimized. As a result, it is possible to obtain a magneto-optical recording medium of the magnetic domain expansion reproducing system having excellent tracking performance and excellent reproducing characteristics. Here, the tracking signal generation area is composed of pits or grooves,
In order to obtain a sufficient servo signal even if the track pitch or the bit pitch becomes narrow, it is preferable that the pits are used.

In the magneto-optical recording medium of the present invention, it is desirable that at least one of the following three types of pits is formed in the tracking signal generating area in addition to the pits for obtaining the servo signal. A mirror surface portion for focus adjustment of the laser light, an address pit portion for coarsely scanning the laser light near the target address position in the optical recording medium, and a clock pit portion for generating a reference clock signal. It is possible to form wobbles that change the groove shape in the circumferential direction in the pits of the address pits and the clock pits, but in order to obtain a sufficient signal even if the track pitch or bit pitch becomes narrow, the pits can be formed. It is desirable to form by.

Further, in the magneto-optical recording medium of the present invention, the shape of the recording / reproducing area may be a flat recording surface, but a plurality of grooves are formed in the track direction and recording tracks formed on or between the grooves. It is desirable to record the information in the. By forming the groove in the track direction, not only crosstalk and crosswrite can be prevented, but also when the magnetic domain expands, the wall of the groove serves as a guide for the domain wall movement, and stable reproduction characteristics can be obtained. Can be fully functional.

[0015]

DETAILED DESCRIPTION OF THE INVENTION

Example 1 The magneto-optical recording medium of the present invention is a magnetic domain expansion reproducing type magneto-optical recording medium. As shown in FIG. 1, a dielectric layer 2, a magnetic domain expansion reproducing layer 3 and an expansion trigger are formed on a substrate 1 as shown in FIG. Layer 4, recording layer 5, recording auxiliary layer 6, protective film 7, and heat dissipation layer 8
Has a structure in which

The substrate 1 is a polycarbonate substrate and is molded by an injection molding machine so that a predetermined uneven pattern is formed. The concavo-convex pattern of the substrate 1 will be described later in detail. The dielectric layer 2 is a layer that causes multiple interference of the reproduction light beam within the layer and increases the detected Kerr rotation angle.
It is composed of SiN. The magnetic domain expansion reproducing layer 3 is a layer in which the magnetic domain transferred from the recording layer 6 is expanded, and is composed of a GdFe perpendicular magnetization film exhibiting ferrimagnetism. The expansion trigger layer 4 is a layer for magnetically exchange-coupling the reproducing layer 3 and the recording layer 5, is made of TbGdFe, and has a Curie temperature of 140 ° C. The recording layer 5 is a layer in which information is recorded as magnetization information, and is TbF having perpendicular magnetization.
It is composed of an eCo amorphous film. The recording auxiliary layer 6 is a layer that is magnetically exchange-coupled with the recording layer 5, and is a layer that enables recording with a smaller modulation magnetic field. The recording auxiliary layer 6 is composed of GdFeCo. The protective film 7 is a layer for protecting the layers 2 to 6 sequentially stacked on the substrate 1, and is made of SiN.
Composed of. The heat dissipation layer 8 is a layer for releasing heat generated during recording and is made of AlTi.

The above layers 2 to 8 were sequentially laminated using a sputtering apparatus under the conditions shown below. The dielectric layer 2 uses Si as a target material, and S is used in an Ar + N ₂ atmosphere.
A film was formed on the substrate 1 by sputtering i. The film thickness of the dielectric layer 2 was 60 nm.

The magnetic domain expansion reproducing layer 3 was formed on the dielectric layer 2 by simultaneously sputtering a single target of Gd and Fe. At this time, the composition of the GdFe film was adjusted by controlling the ratio of the input power of each target. Gd
The Fe composition exhibits perpendicular magnetization from room temperature to the Curie temperature,
The Curie temperature was adjusted to about 240 ° C. and the compensation temperature was adjusted to the Curie temperature or higher. The thickness of the magnetic domain expansion reproducing layer 3 is 2
It was set to 0 nm.

The expansion trigger layer 4 is made of Tb, Gd and Fe.
Was deposited on the magnetic domain expansion reproducing layer 3 by simultaneous sputtering. At this time, the obtained TbGdF
The TbGdFe composition was adjusted so that the e film showed perpendicular magnetization from room temperature to the Curie temperature, the Curie temperature was 140 ° C., and the compensation temperature was room temperature or lower. The film thickness of the expansion trigger layer 4 was 10 nm.

The recording layer 5 was formed on the expansion trigger layer 4 by co-sputtering single targets of Tb, Fe and Co. At this time, the obtained TbFeCo film exhibits perpendicular magnetization from room temperature to the Curie temperature, the Curie temperature is 250 ° C., and the compensation temperature is about 25 ° C.
The composition of the eCo film was adjusted. The thickness of the recording layer 5 is 75 nm
And

The recording auxiliary layer 6 was formed on the recording layer 5 by co-sputtering a single target of Gd, Fe and Co. At this time, the Curie temperature of the obtained GdFeCo film is 270 ° C. and the compensation temperature is room temperature or lower,
The composition of the GdFeCo film was adjusted. The film thickness of the recording auxiliary layer 6 was 10 nm.

The protective layer 7 was formed on the recording auxiliary layer 6 by using Si as a target material and sputtering in an Ar + N ₂ atmosphere. The protective layer 7 had a thickness of 20 nm.

The heat dissipation layer 8 is made of AlT as a target material.
A film was formed on the protective layer 7 by sputtering using i. The film thickness of the heat dissipation layer 8 was 30 nm. Next, an acrylic ultraviolet curable resin is applied on the heat dissipation layer 8 and then irradiated with ultraviolet rays to be cured to thereby protect the protective coat layer 9
Was formed with a film thickness of 10 μm.

Next, the physical format of the tracks formed on the substrate 1 will be described. The track layout of the magneto-optical recording medium of Example 1 is composed of N sectors as shown in the uppermost row of FIG. Each sector is divided into M blocks to which addresses are assigned. A pit indicating only the sector address of itself is formed in the block of address 0 of each sector.
A servo area for scanning a laser beam by the sample servo method is arranged at the head of the block at the address 1 and subsequent blocks, and a recording / reproducing data area is arranged behind the servo area.

The servo area in the sample servo system is, as shown at the bottom of FIG. 3, in the access pit portion for coarsely scanning the laser light near the target address position and on the track for recording / reproducing information. A tracking pit part for following the laser beam, a focusing mirror part for focusing the laser beam to an appropriate position in the magneto-optical recording medium, and a clock signal for generating a data signal. It is composed of a reference clock pit portion.

As shown at the bottom of FIG. 3, the tracking pit portion is composed of two pits 31 and 32, and the pits 31 and 32 are formed at positions displaced in the front-back direction in the track direction. Two pits 31 and 3
2 are formed so as to sandwich the track center, and are separated from the track center by 1/4 of the track width. The focusing mirror surface portion is formed behind the tracking pit portion in the track direction and is a flat mirror surface. The reference clock pit portion is formed behind the focusing mirror surface portion in the track direction, and the pit 33 is formed at the track center.

On the substrate 1 of the magneto-optical recording medium of the magnetic domain expansion / reproduction system manufactured in Example 1, grooves are formed between tracks in the area for recording / reproducing information. Not only does this groove prevent cross-write and crosstalk of the recording / reproducing signal, but by arranging the groove, the wall portion of the groove serves as a guide for domain wall movement when the magnetic domain expands, and stable reproduction characteristics can be obtained. it can. The shape of the substrate cross section is shown in FIG. As shown in FIG. 2, a groove GG and a region (land) LL sandwiched between the grooves are formed on the surface of the substrate by injection molding. As shown in FIG. 2, the inclination angle of the groove wall is θ, and the land L at a depth position half the groove depth D (0.5D).
Let the width of L be the land half-value width L. In addition, the width of the groove GG at a depth position half the groove depth D is defined as the groove half width G
And The track pitch TP is represented by TP = G + L. In the magneto-optical recording medium of Example 1, information is recorded on the land.

[0028]

Example 2 In Example 2, a magneto-optical recording medium of a magnetic domain expansion reproducing system using a sample servo system in which a groove was not provided in a data area on a substrate was manufactured. A magneto-optical recording medium was manufactured in the same manner as in Example 1 except that no groove was provided in the data area. As shown in FIG. 6B, the physical format of the substrate of the magneto-optical recording medium manufactured in Example 2 has the same servo area configuration as that of the physical format of Example 1 (FIG. 6C). The area was formed by a flat mirror surface portion without grooves.

[0029]

COMPARATIVE EXAMPLE 1 In Comparative Example 1, a continuous servo type magneto-optical recording medium was manufactured. The physical format of the track of the magneto-optical recording medium manufactured in Comparative Example 1 is shown in FIG.
As shown in (a), a groove is also formed in the servo area, and the groove has a wobble that meanders periodically toward the center of the groove, and the address signal can be detected from the wobble. A magneto-optical recording medium was manufactured in the same manner as in Examples 1 and 2 except for the shape of the substrate.

FIG. 4 shows a recording / reproducing apparatus 400 used for recording / reproducing the three types of magneto-optical recording media produced in the above example.
Is. The recording / reproducing device 400 includes a magneto-optical system 401 and a control system 402. Among the lines connecting the processing blocks in FIG. 4, the broken line indicates the laser beam and the solid line indicates the flow of the electric signal.

The magneto-optical system 401 of the recording / reproducing apparatus 400 is
A spindle 20 for rotating the magneto-optical disk 10, a magnetic head 30, a laser 100, a collimator lens 101, and two beam shaping prisms 102 and 103.
And three beam splitters 104, 105, 106
, A half-wave plate 107, a rising mirror 108,
Objective lens 109 and three detectors 110 and 11
1 and 112. Laser 100 here
Has a wavelength of 640 nm, and the objective lens 109 has an aperture ratio NA of 0.6.

On the other hand, the control system 402 of the recording / reproducing apparatus 400.
Is a laser drive circuit 200 and a pit signal amplification circuit 2
01, the reference signal generation circuit 202, and the servo circuit 203
2, an MO signal amplifier circuit 204, an actuator drive circuit 205, a magnetic head drive circuit 206, and a controller 207 that controls these circuits.

The reference signal generation circuit 202 is a circuit for generating a reference clock signal for the data area by using the signal detected from the reference clock pit 33 in the servo area shown in FIG. As shown in a)
It is composed of a peak hold circuit, a clock pit detection circuit, a comparator, a low pass filter, a VCO, a frequency dividing circuit, and a reference clock generating circuit. When the signal detected from the reference clock pit 33 in the servo area shown in FIG. 3 is input to the reference signal generation circuit 202,
First, the peak hold circuit and the clock pit detection circuit determine the accurate position of the reference clock pit. Then, the PLL operation by the comparator, the low-pass filter, the VCO, and the frequency dividing circuit removes the jitter generated from the shape of the pit itself, the jitter generated from the electric circuit, the jitter generated from the rotation operation of the spindle, and the like, and an accurate reference clock signal is obtained. Occur.

The servo circuit 203 is a circuit for scanning a laser beam on a predetermined track using the signals detected from the tracking pits 31 and 32 in the servo area shown in FIG. 3, and FIG. As shown in, it is composed of a signal detection circuit, a sample hold circuit, a phase compensation circuit, an amplifier, and an actuator drive circuit,
This is a servo circuit generally used in digital signal processing. In this circuit, the sample hold circuit is adjusted so that the servo signal is detected only in the servo area shown in FIG. 3, and the phase compensation circuit is provided so as to have a sufficient low-frequency gain and high-frequency phase margin. It is set.

The three types of magneto-optical recording media produced in Examples 1 and 2 and Comparative Example 1 were subjected to an information recording / reproducing test using the recording / reproducing apparatus. Test data was recorded using an optical pulse magnetic field modulation method in which a laser beam was applied in a pulsed manner and an external magnetic field was applied while being modulated according to the recorded information. The linear velocity of the magneto-optical recording medium is 3.5 m /
sec, the recording magnetic field was 200 Oe. The duty of the pulsed light during recording was set to 30% and the recording power of the laser light was optimized. Recording was done in the land area. A random pattern having a shortest mark length of 0.12 μm was recorded as a recording pattern. When reproducing information, the magneto-optical recording medium was irradiated with reproducing light having an optimized reproducing power without applying an external magnetic field to detect a magnetic domain expansion reproducing signal.

[Characteristic Evaluation of Servo Signal Amount] A recording / reproducing test was conducted on the three types of magneto-optical recording media prepared in the above examples by changing the track pitch, and the servo signal amount detected from each magneto-optical recording medium was measured. And compared. The results are shown in Fig. 7. The continuous servo A in the figure shows the results of the magneto-optical recording medium of Comparative Example 1, and the sample servo methods B and C in the figure are the magneto-optical recording medium of Example 2 and the magneto-optical recording of Example 1, respectively. The experimental results of the medium are shown. Figure 7
As shown in, in the continuous servo system, when the track pitch is 0.6 μm or less, the servo signal amount necessary for the tracking servo cannot be obtained, but in the sample servo system, even if the track pitch is 0.6 μm or less, A sufficient amount of servo signals for tracking servo is obtained. Therefore, by using the sample servo method to configure the servo area with pits, a sufficient amount of servo signals can be obtained even if the track pitch is narrowed.
Higher density recording is possible.

[Evaluation of Track Pitch] Next, a recording / reproducing test was conducted on the three types of magneto-optical recording media prepared in the above-mentioned examples by changing the track pitch, and the bit error rate (hereinafter, BER) of each magneto-optical recording medium was tested. It was measured and compared. The result is shown in FIG. Figure 8 (a)
As shown in, when the threshold value (upper limit) of BER is 1 × 10 ⁻⁴ , it is about 0.68 μm or more in the continuous servo system (curve A in the figure) and about 0 in the sample servo system (curve B in the figure). A good BE with a track pitch of 0.66 μm or more, and a track pitch of about 0.62 μm or more when a groove is arranged between tracks in the sample servo system (curve C in the figure)
R was obtained.

As shown in FIG. 8 (a), in the continuous servo system, when the track pitch becomes smaller than 0.7 μm, the track servo is not driven and the B servo becomes sharp.
ER deteriorated. Further, comparing the sample servo system and the case where the grooves are arranged between the tracks in the sample servo system, a good BER was obtained in the case where the grooves were arranged (Example 1) even in a region where the track pitch was small. It is considered that this is because crosstalk and crosswrite were reduced by arranging the grooves between the tracks. Therefore, it is considered that by forming the groove between the tracks, the function of magnetic domain expansion reproduction is sufficiently exerted, and a better BER can be obtained. Further, by using the sample servo method, a good BER was obtained even if the bit pitch was narrowed, so that higher density recording is possible.

[Evaluation of Shortest Recording Mark Length] In the above comparative example, comparison was made with respect to the magneto-optical recording medium having the shortest recording mark length of 0.12 μm, but here, the three types of magneto-optical recording media produced in the above-mentioned example are compared. The recording and reproducing test was performed by changing the shortest recording mark length for
Was measured and compared. The result is shown in FIG. As shown in FIG. 8B, when the threshold value (upper limit) of the BER is set to 1 × 10 ⁻⁴ , the change in the BER with respect to the shortest recording mark length is about 0 in the continuous servo system (curve A in the figure). Minimum recording mark length of 13 μm or more, about 0.11 μm or more in the sample servo system (curve B in the figure), and about 0.10 μm or more in the case of the sample servo system and a groove is arranged between tracks (curve C in the diagram) And good B
It turns out that ER is obtained. Compared with the continuous servo system, the sample servo system obtained a good BER even when the shortest recording mark length was smaller. Therefore, by using the sample servo method, a good BER can be obtained even if the shortest recording mark length is narrowed.
Higher density recording is possible.

[Evaluation of Recording Mark Shape] Next, in the magneto-optical recording medium of the sample servo system and having grooves formed between tracks, manufactured in Example 1, the shape of the recording mark was changed and the BER of the reproduction signal was measured. did. The length of the recording mark in the track direction (hereinafter referred to as the vertical width) is 0.1 μm, 0.
The reproduction experiment was performed by changing the width to 12 μm and 0.14 μm, and further changing the width of the recording mark in the direction traversing the track (hereinafter referred to as the horizontal width) with respect to each vertical width. The vertical width of the recording mark can be changed by adjusting the modulation period of the magnetic field pulse applied during information recording. On the other hand, the lateral width can be changed by adjusting the output of the laser beam applied during information recording. This result is shown in FIGS.
I set it to 1. FIG. 9 shows the BER characteristics when the recording mark height is 0.1 μm and the recording mark aspect ratio is changed, and FIG. 10 is the BER characteristic when the recording mark height is 0.12 μm and the recording mark aspect ratio is changed. FIG. 11 shows the BER characteristics when the recording marks are made to have a vertical width of 0.14 μm.
Is the BER characteristic when the recording mark aspect ratio is changed. When the vertical width of the recording mark is 0.1 μm, FIG.
As shown in (1), by adjusting the lateral width to about 0.56 μm or less, a good BER of 1 × 10 ⁻⁴ or less could be obtained. However, when the width becomes 0.15 μm or less, BER
Has deteriorated. It is considered that this is because when the width of the recording mark becomes 0.15 μm or less, the influence of crosstalk becomes large.

As shown in FIGS. 9 to 11, the threshold value of BER
(Upper limit) is 1 × 10^-4Then the vertical width of the recording mark is
When 0.1 μm, the aspect ratio (width / height) is 1.5
It can be seen that a good BER can be obtained at ˜5.6. Record
When the mark width is 0.12 μm, the BER threshold
1 x 10^-4If so, the aspect ratio of 1.3 to 5.4 is good.
A good BER was obtained, and the aspect ratio was increased to 2.9-4.3.
Then 1 × 10^-5The following optimum BER can be obtained
I understand. If the recording mark has a vertical width of 0.14 μm,
The threshold of BER is 1 × 10^-4Then the aspect ratio
Is 1.1 to 6.2, a good BER is obtained, and
When the ratio is set to 1.8 to 5.0, 1 × 10 ^-5Best for
It can be seen that a good BER is obtained. The results of FIGS.
Taken together, the aspect ratio of the recording marks is in the range of 1.5 to 5.4.
If enclosed, 1 x 10^-4The following good BER is obtained
I understand that The light of the magnetic domain expansion reproducing system as in the present invention
When the sample servo method is used for the magnetic recording medium,
Servo for tracking the substrate shape in the recording / playback area
Since it can be designed regardless of the area, the shape of the recording mark can be improved.
A magneto-optical recording medium with the optimum aspect ratio shown in
Can be made.

The following shows the results of the recording / reproducing characteristics when the groove shape was changed in the magneto-optical recording medium of the magnetic domain expansion reproducing method using the sample servo method manufactured in Example 1.

[Evaluation of ratio L / G of groove half width G and land half width L] Regarding the magneto-optical recording medium of the magnetic domain expansion reproducing system of Example 1 described above, the groove width was changed to the groove half width G. When the ratio L / G of the land half width L is changed,
As shown in FIG. 12, the BER threshold (upper limit) is set to 1 × 10.
^-4 , good BER was obtained when L / G was 1.3 ≦ L / G ≦ 4.0. Especially L / G is 2.0 ≦ L / G
In the range of ≦ 3.0, the BER was 1 × 10 ⁻⁵ or less, and the optimum BER was obtained.

[Evaluation of Groove Depth D] When the groove depth D is changed, the BER threshold value (upper limit) is set to 1 as shown in FIG.
When set to × 10 ⁻⁴ , good BER was obtained when the value of D was 30 nm to 80 nm. Especially when the value of D is 40 nm to 6
When it was in the range of 5 nm, the BER was 1 × 10 ⁻⁵ or less, and the optimum BER was obtained. However, in this experiment, a laser beam having a wavelength of 640 nm is used, but when a laser beam having a shorter wavelength is used, the optimum range of the groove depth D shown above becomes smaller. On the contrary, when a laser beam having a long wavelength is used, the optimum range of the groove depth D shown above becomes large.

[Evaluation of Groove Inclination Angle θ] When the groove inclination angle θ is changed and the BER threshold (upper limit) is set to 1 × 10 ⁻⁴ as shown in FIG. 14, the value of θ is 40. ° ~ 75 °
At that time, a good BER was obtained. Especially when the value of θ is 45 °
When it was in the range of 60 °, the BER was 1 × 10 ⁻⁵ or less, and the optimum BER was obtained.

In the above-mentioned embodiment, the magnetic domain expansion reproducing type magneto-optical recording medium having eight layers (excluding the protective coating layer 9) is exemplified, but the present invention is not limited to this. As a basic layer structure, it suffices that the substrate has a recording layer for recording information as magnetic domains and a reproducing layer for transferring and expanding the recorded magnetic domains during reproduction.

In the above embodiment, the information is recorded in the land portion defined between the grooves, but in the case of the magnetic domain expansion reproducing system medium, the groove is provided because the groove is provided. Since the domain wall movement is smoothed by the side wall (side wall of the land), it is possible to record information not only in the land but also in the groove (groove) or in both the land and the groove.

[0048]

According to the present invention, there is provided a magneto-optical recording medium capable of sufficiently exhibiting the function of magnetic domain expansion / reproduction and capable of higher density recording.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a layer structure of a magneto-optical recording medium of a magnetic domain expansion reproducing system manufactured in Example 1.

2 is a schematic cross-sectional view of a groove shape of the substrate manufactured in Example 1. FIG.

FIG. 3 is a schematic view of a physical format of a sample servo type substrate manufactured in Example 1.

FIG. 4 is a schematic circuit diagram of a recording / reproducing apparatus used for recording / reproducing of a magneto-optical recording medium according to the present invention.

5 is a schematic configuration diagram of a reference signal generation circuit and a servo circuit in FIG. 4, (a) is a configuration diagram of a reference signal generation circuit, and (b) is a configuration diagram of a servo circuit.

6A and 6B are schematic diagrams of a physical format of a substrate used in a recording / reproducing test, FIG. 6A is a schematic diagram of a physical format of a continuous servo system, and FIG. 6B is a schematic diagram of a physical format of a sample servo system. Yes,
(C) is a schematic diagram of a physical format of a substrate in which grooves are arranged between recording tracks in the sample servo system.

FIG. 7 is a diagram comparing servo signal amounts of magneto-optical recording media of sample servo system and continuous servo system manufactured in Examples 1 and 2 and Comparative Example 1.

FIG. 8 is a diagram comparing bit error rate characteristics when a continuous servo system, a sample servo system, and a substrate in which a groove is arranged between recording tracks is used, and FIG. It is a bit error rate characteristic with respect to a track pitch, and (b) is a bit error rate characteristic with respect to a bit pitch.

FIG. 9 is a diagram showing the bit error rate characteristics when the recording mark height is 0.1 μm and the recording mark aspect ratio is changed.

FIG. 10 shows a recording mark having a vertical width of 0.12 μm.
FIG. 9 is a diagram showing bit error rate characteristics when the recording mark aspect ratio is changed.

FIG. 11 shows a recording mark having a vertical width of 0.14 μm.
FIG. 9 is a diagram showing bit error rate characteristics when the recording mark aspect ratio is changed.

FIG. 12 is a diagram showing the bit error rate characteristics when the land width and the groove width are changed in the magneto-optical recording medium of the magnetic domain expansion reproducing system of Example 1.

13 is a diagram showing bit error rate characteristics when the groove depth is changed in the magneto-optical recording medium of the magnetic domain expansion reproducing system of Example 1. FIG.

FIG. 14 is a diagram showing the bit error rate characteristics when the groove inclination is changed in the magneto-optical recording medium of the magnetic domain expansion and reproduction system of Example 1.

[Explanation of symbols]

1 substrate 2 Dielectric layer 3 Magnetic domain expansion reproduction layer 4 Expanded trigger layer 5 recording layers 6 Recording auxiliary layer 7 protective layer 8 Heat dissipation layer 9 Protective coating layer 31,32 Tracking pit 33 clock pits 10 magneto-optical disk 20 spindles 30 magnetic head 100 laser 101 collimator lens 102,103 Beam shaping prism 104,105,106 Beam splitter 107 1/2 wave plate 108 Launch mirror 109 Objective lens 110,111,112 detector 200 laser drive circuit 201 pit signal amplification circuit 202 Reference signal generation circuit 203 Servo circuit 204 MO signal amplification circuit 205 actuator drive circuit 206 Magnetic head drive circuit 207 controller 400 recording / reproducing device 401 Magneto-optical system 402 control system

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shosuke Shimazaki             Hitachima, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. F-term (reference) 5D075 EE03 FF13 FG18

Claims (5)

[Claims] 1. A recording layer in which information is recorded as magnetic domains,
A magneto-optical recording medium comprising a reproducing layer in which magnetic domains recorded in a recording layer are transferred and enlarged by irradiation of laser light during reproduction, and a substrate in which a region for generating a tracking signal and a recording / reproducing region are defined. A magneto-optical recording medium, wherein the tracking signal generating area and the recording / reproducing area are formed at different positions in the track direction. 2. The magneto-optical recording medium according to claim 1, wherein pits detected by a sample servo method are formed in the tracking signal generating area. 3. The tracking signal generating area, a mirror surface portion for adjusting the focus of the laser light, an address pit for coarsely scanning the laser light near a target address position in the magneto-optical recording medium, and a reference. The magneto-optical recording medium according to claim 1, wherein at least one of clock pits for generating a clock signal is formed. 4. The recording / reproducing area is provided with a plurality of grooves formed in a track direction, and recording tracks defined on or between the grooves. Magneto-optical recording medium. 5. The magneto-optical recording medium according to claim 4, wherein information is recorded on the recording track.