JPH1083589A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a land / groove recordable magneto-optical recording medium capable of sufficiently obtaining a reproduction signal intensity and accurately performing tracking control. SOLUTION: A magneto-optical disk 1 is configured by laminating a plurality of magnetic layers 4 made of a rare earth-transition metal alloy on a substrate 5 having lands 2 and grooves 3 formed on the surface. The grooves 3 and the lands 2 are arranged at equal pitches in the radial direction of the disk to form tracks.
Has a phase depth of 0.047λ / n to 0.10λ / n.

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 on which information is recorded on both lands and grooves, and more particularly, to an MSR (Magnetically Induced Super Resolution) capable of reproducing a recording mark smaller than the spot diameter of irradiation light. Regarding the medium.

[0002]

2. Description of the Related Art In recent years, a demand for a large-capacity memory has been increased in accordance with the high performance of a computer, and an optical disk and a magneto-optical disk have been developed and commercialized to satisfy this demand.
There is a demand for a further increase in capacity for the future multimedia era. On the magneto-optical disk, a V-shaped groove is formed concentrically or spirally around the center of the disk. A land is provided between the grooves to form a track, and a magnetic film is formed on the surface of the track.

When recording information on a magneto-optical disk,
The light beam condensed to approximately 1 μm irradiates the land while being guided by the groove. The temperature of the magnetic film is raised to a temperature close to the Curie temperature, the coercive force decreases, and the magnetization direction is reversed to the magnetization direction corresponding to the information. When reproducing the recording mark (bit) of the land thus formed, the light beam is irradiated to the land while being guided by the groove, and the reflected light from the land is collected to detect the direction of the Kerr rotation. I do. Based on this detection, the magnetization direction of the recording mark is read to reproduce information.

In order to record information on such a magneto-optical disk at a high density, a land / groove recording method has been proposed in which a groove is formed in a U-shaped cross section and recording marks are formed in both land and groove areas. (Japanese Patent Publication No. 57-5033)
No. 0). According to this method, the density of information recording is further increased. However, since the formation density of recording marks in the radial direction of the disk is increased, there has been a problem that crosstalk during reproduction increases.

The following proposals have been made to solve the above problems. First, the optical recording medium proposed in JP-A-3-104021 has a phase depth of λ / 8, 3λ /.
8 are alternately provided in the radial direction to increase the amount of reflected light from the disk, thereby increasing the S / N ratio of the reproduced signal.
Is increasing. The phase depth is λ / 8, 2.5λ /
8 are provided alternately in the radial direction to suppress a local characteristic change of reflected light, thereby reducing crosstalk. Here, λ is the wavelength of the irradiation light.

In the optical recording medium proposed in Japanese Patent Application Laid-Open No. 5-62250, the phase of the light reflected from the groove and the light reflected from the land are adjusted by setting the phase depth of the groove to λ / 4. Is shifted by π to reduce crosstalk.

Further, in the optical disk disclosed in Japanese Patent Laid-Open No. 5-282705, the phase depth of the groove is set to (1/7 + n / 2) λ.
By setting to (5/14 + n / 2) λ, crosstalk in the case where pits are formed in both the groove and the land is reduced. Here, n is the refractive index of the substrate provided on the optical disk. Furthermore, an optical recording medium proposed in Japanese Patent Application Laid-Open No. 6-203411 is an optical disk in which pits for guiding reproduction light irradiation are provided at a boundary between a groove and a land (Japanese Patent Application Laid-Open No. 5-282705). Disclosure), by setting the phase depth of the groove to λ / (8n) to 5λ / (14n), crosstalk when signals are recorded on both the groove and the land is reduced.

Furthermore, the optical recording medium proposed in JP-A-7-29186 has a groove phase depth of 0.1λ.
(2n + 1) to 0.2λ (2n + 1), and by specifying the width of the groove, the level of the reproduced signal from the land and the level of the reproduced signal from the groove are made equal.

Furthermore, the magneto-optical recording media proposed in JP-A-7-65423 and JP-A-8-55375 have a groove phase depth of 0.10λ / n to 0.14λ / n, respectively.
By setting n, 0.13λ / n to 0.18λ / n, an object is to reduce crosstalk when a signal is recorded on both the groove and the land.

[0010]

On the other hand, as another method of recording information on a magneto-optical disk at a high density and reproducing the information, an MSR (Magnetically Induced Super Resolution) is used.
) There is regeneration technology. The MSR reproduction technique irradiates a magneto-optical disk having a plurality of magnetic layers magnetically coupled on a substrate with a beam light, and reads a recording mark from a specific temperature region formed in a beam spot, This enables a recording mark smaller in size than the beam spot to be reproduced. Several types of MSR reproducing methods have been proposed depending on the form of the temperature distribution formed in the beam spot.

FIG. 9 is a diagram showing a magnetization state at the time of reproduction of an MSR medium, which is a magneto-optical disk capable of the MSR reproduction method, disclosed by the present applicant in Japanese Patent Application Laid-Open No. 7-244877. A reproducing layer 51, an intermediate layer 52, and a recording layer 53 made of a rare earth-transition metal alloy are stacked on a substrate (not shown). The reproducing layer 51 and the recording layer 53 each have an easy axis of magnetization in a direction perpendicular to the substrate, and the intermediate layer 52 has an easy axis of in-plane direction at room temperature. The reproduction layer 51,
Curie temperatures Tc1 and Tc of the intermediate layer 52 and the recording layer 53
2 and Tc3 satisfy the relationship of Tc1> Tc2, Tc3> Tc2. Further, the reproducing layer 51 and the recording layer 53
The coercive forces Hc1 and Hc3 at room temperature are Hc1 <H
The relationship of c3 is satisfied.

A recording mark 54 having a diameter equal to or smaller than the beam spot 55 is formed on the MSR medium having the above-described film configuration. When reproducing the recording mark 54, a beam of a certain power is irradiated. At this time, in the beam spot 55, a high-temperature region that is equal to or higher than the temperature T and equal to or lower than the Curie temperature Tc2 is formed on the front side in the rotation direction of the magneto-optical disk, and a low-temperature region that is lower than the temperature T is formed on the rear side. Here, the temperature T is a temperature at which the magnetization of the recording layer 53 is transferred to the reproducing layer 51.

In the low temperature region, the magnetization of the reproducing layer 51 is aligned with the direction of the externally applied low reproducing magnetic field to form a magnetic mask. In the high temperature region, the magnetization of the recording layer 53 is
Is transferred to the reproducing layer 51 through the opening to form an opening. Such MSR reproduction technology is known as RAD (Rear Aperture Dete
ction) A reproduction method is called, and it is possible to reproduce the recording mark 54 having a beam spot diameter or less by such an MSR reproduction technique.

In such a medium using the land / groove recording method for the MSR medium, a cross-talk is reduced because a partial area in the beam spot becomes an opening. However, in a medium on which land / groove recording is performed, the intensity of a reproduced signal is low when the groove is deep. This can be seen from the relationship between the groove depth and the reflectance shown in FIG. The signal intensity is S, and the power of the reproduction light is P
r, the reflectance of the reproduction light is R, and the Kerr rotation angle is θ, which indicates that there is a relationship of S∝ (R × θ × Pr). Further, in the MSR reproducing method, since only a signal from a partial area in the beam spot is reproduced, the intensity of the reproduced signal is lower than that of a normal medium for reproducing a recording mark having a large beam spot. For these reasons, the MSR medium using land / groove recording has a problem that the signal intensity during reproduction is low, and it is difficult to obtain a sufficient C / N.

The present invention has been made in view of the above circumstances, and it has been made possible to obtain a phase depth of a groove of a magneto-optical recording medium on which land / groove recording is performed, obtain a sufficient reproduction signal intensity, and accurately perform tracking control. It is an object of the present invention to provide a magneto-optical recording medium capable of obtaining a sufficient C / N by setting the range within the range as described above.

[0016]

In the magneto-optical recording medium according to the first aspect of the invention, recording marks can be formed on each of the grooves and the lands provided between the grooves, and the recording marks can be made larger than the spot diameter of the reproducing irradiation light. In a magneto-optical recording medium capable of reproducing small-diameter recording marks, the groove has a phase depth of 0.047.
λ / n to 0.10λ / n.

FIG. 10 is a graph showing the relationship between the phase depth of the groove and the reflectivity of the magneto-optical disk of FIG. 9 on which land / groove recording is performed. The vertical axis shows the reflectivity of the groove during tracking, and the horizontal axis shows the phase depth of the groove. FIG. 11 is a graph showing the relationship between the phase depth of the groove and the reproduction characteristics of the magneto-optical disk of FIG. 9 on which land / groove recording has been performed. The vertical axis indicates the C / N change of the groove at the time of reproduction. The axis indicates the phase depth of the groove. 10 and 11, the reflectance of the reflected light decreases as the phase depth of the groove increases, and the C
/ N decreases.

FIG. 12 is a graph showing the relationship between the groove phase depth and tracking characteristics of the magneto-optical disk of FIG. 9 on which land / groove recording is performed. The vertical axis indicates the divided push-pull (DPP) signal strength at the time of tracking, and the horizontal axis indicates the phase depth of the groove. FIG.
From this, it can be seen that the DPP signal increases as the phase depth increases up to a phase depth of 0.16λ / n, and decreases as the phase depth increases below 0.16λ / n.

According to the ISO standard, a DPP of 0.5 or more is required for a 90 mm, 640 MB magneto-optical disk. The DPP of the above-mentioned magneto-optical disk is 0.5
This is because the phase depth of the groove is 0.04λ / n or more from FIG. Also, from the viewpoint of reproduction characteristics,
It can be said that the phase depth of the groove is preferably equal to or less than 0.1λ / n, at which the C / N of the reproduced signal decreases gradually. From these facts, when the phase depth of the groove is less than 0.04λ / n, tracking control cannot be sufficiently performed, and
If it exceeds λ / n, it can be seen that the C / N of the reproduced signal cannot be sufficiently obtained. 10 to 12, the phase depth is the product of the value on the horizontal axis and (λ / n), n is the refractive index of the substrate, and λ is the wavelength of the irradiation light.

In the magneto-optical recording medium according to the second aspect of the invention, recording marks can be formed on each of the groove and the land provided between the groove, and information is recorded on a track constituted by each of the groove and the land. In a magneto-optical recording medium that includes an information recording area to be recorded and a preformat recording area to record preformat information and is capable of reproducing a recording mark having a diameter smaller than the spot diameter of reproduction irradiation light, the groove includes the information. 0.047λ / n in recording area
The phase depth of the sector mark recording area of the preformat recording area is zero, and the pit corresponding to the sector mark is a phase depth of the information recording area of the groove. Characterized by having the same depth as.

The depth of a sector mark recording area, which is an area where a sector mark is to be formed in the preformat recording area of the groove, is set to zero, and pits corresponding to the sector mark are formed in this area. By forming the pits at the same depth as the phase depth (0.04λ / n to 0.1λ / n) of the groove in the information recording area, the manufacture of the magneto-optical recording medium is simplified. By setting the depth of the sector mark recording area to zero, a pit having the same depth as the information recording area of the groove can be formed. When only the sector mark of the preformat information is formed by pits and the rest is magneto-optically recorded, the pits are reproduced because the phase depth of the pits is shallow because the sector marks can be detected even if the reproduction signal intensity is small. There is no inconvenience that a signal cannot be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a perspective view showing the configuration of the magneto-optical disk of the present invention. The magneto-optical disk 1 has a dielectric layer (not shown) made of SiN, a plurality of magnetic layers 4 made of a rare earth-transition metal alloy, and a plurality of magnetic layers 4 made of a rare earth-transition metal alloy on a polycarbonate substrate 5 having lands 2 and grooves 3 formed on the surface. A protective layer (not shown) made of SiN is laminated in this order. Grooves 3 and lands 2 forms a track are arranged at equal pitches in the radial direction of the disk, the groove 3 has a depth D _G. In each sector, a preformat recording area 11 for recording preformat information such as an ID information signal (identification information signal) and a clock signal as information for each sector, and a data recording area 12 for recording data are provided. Have.

The preformat recording area 11 is divided into a sector mark recording area 11p for recording a sector mark for detecting the head of a sector and an MO recording area 11m for recording preformat information excluding the sector mark in the circumferential direction. Equipped. The grooves 3 are not formed in the sector mark recording area 11, and the lands 2 and the grooves 3 are formed in the MO recording area 11m and the data recording area 12 at a constant pitch in the radial direction.

[0024] the sector mark recording area 11, sector marks are formed by pits 13, 13, pits have a depth D _P. In the MO recording area 11m,
Recording marks 14 and 15 corresponding to preformat information excluding sector marks are formed by a magneto-optical recording method. In the data recording area 12, recording marks 14, 15 corresponding to data to be recorded are formed by a magneto-optical recording method.

The procedure for manufacturing the magneto-optical disk 1 having the above configuration will be described below. First, a glass master for forming the substrate 5 is prepared. FIG. 2 is a configuration diagram of a beam exposure apparatus used when manufacturing the magneto-optical disk of the present invention. First, a photoresist having a predetermined thickness is applied to the polished glass master G by a spin coating method, and prebaked at 90 ° C. for 30 minutes in a clean oven. This glass master G is used as a spindle motor 3 shown in FIG.
2 is placed on a sample table 20 provided with the same. The thickness of the photoresist is determined in the range of 10 nm to 110 nm.

The configuration of the beam exposure apparatus will be described.
Reference numeral 21 denotes an Ar laser light source, and the beam light emitted from the light source 21 is transmitted and reflected by the half mirror 22a to be separated. First, the first light beam reflected by the half mirror 22a enters the first condenser lens 23a.
The light condensed by the first condenser lens 23a is the first AOM
(Acousto-optic modulator) The light is input to 24a, and the light intensity is modulated. The intensity-modulated light is incident on the first collimating lens 25a, where it is returned to parallel light and
Is input to the beam expander 26a. In the first beam expander 26a, the beam diameter is enlarged, reflected by the half mirror 27a, and incident on the half mirror 28. The first collimating lens 25a and a second collimating lens 25b described later are configured to be movable in a direction orthogonal to the optical axis, and by this movement, the first beam light and a second beam light described later are moved. The relative position is controlled.

On the other hand, the second light beam transmitted by the half mirror 22a is incident on the mirror 22b and forms the same optical path as the first light beam. That is, the light reflected by the mirror 22b and incident on the second condenser lens 23b is condensed here, enters the second AOM 24b, and the light intensity is modulated. The intensity-modulated light is incident on the second collimator lens 25b, where it is converted back to parallel light and enters the second beam expander 26b. In the second beam expander 26b, the beam diameter is enlarged, and the mirror 27
The light is reflected by b, passes through the half mirror 27a, and enters the half mirror 28.

The first and second light transmitted through the half mirror 28
Of the first and second collimating lenses 25
The light enters the optical head 29 while maintaining the relative positions controlled by a and 25b. The optical head 29 includes a dichroic mirror 30 and an objective lens 31, and is configured to be movable in directions perpendicular and parallel to the sample table 20. The first and second light beams are reflected by the dichroic mirror 30 and focused on the glass master G by the objective lens 31. Focusing on the glass master G is controlled by the vertical movement of the optical head 29.
A wavelength at which the photoresist of the glass master G is not exposed
A laser beam of 780 nm is applied to the glass master G, and the focus control is performed by moving the optical head 29 in the vertical direction according to a focusing error signal due to the reflected light.

The position on the glass master G to which the first light beam and the second light beam are irradiated is determined by the optical head 29.
Of the optical head 29
Is moved in the parallel direction according to an instruction from the exposure control unit 33. Further, the exposure control unit 33 includes first and second AOMs.
An exposure power instruction is given to 24a and 24b to control the degree of light intensity modulation. By this control, the depths D _G and D _{P of} the grooves 3 and the pits 13 formed on the glass master G are respectively controlled. Further, a sector mark recording area 11p and an MO recording area 11m are formed.

The first light beam and the second light beam condensed and reflected on the glass master G are reflected by the dichroic mirror 30, reflected by the half mirror 28, and enter the relative beam position detection unit 34. . The relative beam position detector 34 can monitor the relative positions of the first light beam and the second light beam.

Using the beam exposure apparatus as described above, the land 2 and the groove 3 are formed to have the same pitch with the groove pitch of 1.4 μm. By the first light beam in the data recording area 12 to form the groove 3 at a depth D _G. By irradiating the second light beam by stopping irradiation of the sector mark recording area first light beam at 11p, forming pits 13 without forming a groove 3 at a depth D _P. Then, in the MO recording area 11m, the irradiation of the second light beam is stopped again to
A depth D _G by beam forming the grooves 3.

The glass master G on which the pits 13, the lands 2 and the grooves 3 are formed, and the preformat recording area 11 and the information recording area 12 are formed is carried into a vacuum evaporator, and Ni on the surface of the glass master G is 0.2 μm. An electrode for plating is formed by vapor deposition to a thickness. And N by electrolytic plating
i is plated to a thickness of 0.3 mm.
Is removed to obtain a Ni stamper. The inner and outer peripheries of the stamper are processed to predetermined dimensions, and the substrate 5 made of polycarbonate is formed by emission molding using the stamper.
Thus, the substrate 5 on which the pits 13 and the grooves 3 having the same dimensions as the glass master G are formed is manufactured.

Next, a 75 nm thick dielectric layer made of SiN is formed on the substrate 5 by RF magnetron sputtering. Gd _24.5 Fe ₆₆ C as the magnetic layer 4 on the dielectric layer
40 nm of the reproducing layer 41 made of o _9.5 and Gd ₃₂ Fe ₆₈
40 nm of the intermediate layer 42 made of Tb ₂₄ Fe ₅₆ Co ₂₀
The recording layer 43 of 50 nm is sequentially formed. A 65 nm protective layer is formed on the recording layer 43.

Recording marks 14 and 15 are formed in the MO recording area 11m and the information recording area 12 of the magneto-optical disk 1 by a magneto-optical recording method. First, the magneto-optical disk 1 is irradiated with laser light at an erasing power of 9 mW, and an upward erasing magnetic field (see FIG. 3) is applied at 500 eO to erase the entire surface of the disk. Next, the magneto-optical disk 1 is moved at a linear velocity of 6
m / s, and a downward recording magnetic field of 500 eO
And irradiate a laser beam with a recording power of 10 mW.
Recording is performed on each of the land 2 and the groove 3 at a frequency of 7.5 MHz and a duty of 26%. Recording marks 14, 15
Is 0.4 μm in the circumferential direction.

The recording marks formed on the magneto-optical disk 1 manufactured as described above are reproduced by using the MSR reproducing technique, and the C / N and the crosstalk of the reproduced signal are measured. The magneto-optical disk reproducing device used at this time is equipped with a 680 nm semiconductor laser, and has a NA of the objective lens.
Is 0.55. FIG. 3 is a diagram showing a magnetic film configuration of the magneto-optical disk 1 and a magnetization state during reproduction. In the figure, the optical disk 1 is shown with the substrate 5, the dielectric layer and the protective layer omitted.

An upward reproducing magnetic field of 500 eO is applied, and a laser beam having a reproducing power of 2 mW is irradiated from the substrate 5 side. At this time, the low temperature area, the intermediate temperature area,
The high-temperature regions are formed sequentially from the rear side in the disk rotation direction. In the low temperature region, the recording mark of the recording layer is magnetically masked by aligning the intermediate layer with the reproducing magnetic field, and in the high temperature region, the recording mark of the recording layer is magnetically masked by aligning the reproducing layer with the reproducing magnetic field. In the intermediate temperature region formed between these regions, the recording marks formed on the recording layer are transferred to the reproducing layer and read. As described above, the magneto-optical disk 1 of the present embodiment has the double mask RAD
(Rear Aperture Detection) Recording marks can be reproduced by the reproduction method. Regarding a magneto-optical disk for double-mask RAD reproduction, the applicant of the present invention disclosed in Japanese Patent Application
-244877, and a detailed description is omitted.

In this embodiment, the case where the glass master is formed by using the beam exposure apparatus when manufacturing the substrate 5 on which the groove 3 is formed has been described. However, the present invention is not limited to this. For example, a visible short-wavelength laser or an ultraviolet laser may be used, and an EOM (electro-optic
The device may be configured to modulate the intensity of the light beam using a modulator, or any device that can form grooves and pits in the glass master G while controlling the intensity of the light beam.

[0038]

【Example】

Embodiment 1 FIG. The magneto-optical disc 1 described above, prepared by varying the depth D _G of the groove 3, according to the depth D _G, was measured tracking characteristics and reproduction characteristics. The depth of the groove 3 was adjusted by changing the thickness of the photoresist applied to the glass master G. The method of manufacturing the magneto-optical disk 1 and the conditions for recording and reproducing the recording marks are the same as in the above-described embodiment. The depth D _G of the groove 3 is 1
0 nm, 20 nm, 30 nm, 40 nm, 60 nm, 8
0 nm and 110 nm were produced respectively. For each magneto-optical disk 1, a reproduction signal and a DPP signal when reproducing the recording mark 15 formed on the land 2 were measured.

The results are shown in FIG. FIG. 4 is a graph showing the relationship between the groove depth, the reflectance, and the tracking characteristics of the magneto-optical disk of the first embodiment. The vertical axis is DP
P and the reflectance are shown, and the horizontal axis shows the groove depth. Table 1 also shows the result of measuring the crosstalk from the land 2 outside the tracking groove 3 together with the C / N of the reproduced signal. The wavelength λ of the laser beam irradiated during reproduction is 680 nm, and the substrate 5
Has a refractive index n of about 1.59.

[0040]

[Table 1]

As can be seen from FIG. 4, when the depth of the groove 3 is 10 nm, the DPP is 0.25, which does not satisfy the ISO standard. When the depth is 20 nm, the DPP
Is 0.5, and the DPP increases as the depth increases. Also, as shown in Table 1, the depth of the groove 3 is 2
In the range of 0 nm to 40 nm, the C / N of the reproduced signal is 51.
The value of crosstalk is 5 dB or more and the value of crosstalk is -35 dB or less. These values are sufficient for practical use. When the depth of the groove 3 is 60 nm, the C / N of the reproduced signal is 50.
5 dB, which is insufficient for practical use. Thereby, a sufficient C / N is obtained, and the depth of the groove 3 at which accurate tracking control can be performed is 20 nm to 40 n.
m (0.047λ / n to 0.10λ / n). When the depth of the groove 3 is 10 nm,
Tracking control cannot be performed accurately, and C / N
And crosstalk could not be measured.

Embodiments 2 and 3 In the first embodiment, the track pitch is 0.7 μm and the groove pitch is 1.4 μm. In the second embodiment, a magneto-optical disk having the track pitch of 0.6 μm and the groove pitch of 1.2 μm is manufactured. 3 manufactures a magneto-optical disk formed with a track pitch of 0.8 μm and a groove pitch of 1.6 μm.
Then, in the same manner as in Example 1, the depth D _G of the groove 3 is 1
0 nm, 20 nm, 30 nm, 40 nm, 60 nm, 8
0 nm and 110 nm were manufactured, and for each,
A reproduction signal and a DPP signal when the recording mark 15 formed on the land 2 was reproduced were measured. The results are shown in FIG. 5 and Table 2 for Example 2, and FIG. 6 and Table 3 for Example 3. The manufacture of the magneto-optical disk 1 was performed in the same manner as in the above-described embodiment.

FIGS. 5 and 6 are graphs showing the relationship between the groove depth, the reflectivity and the tracking characteristics of the magneto-optical disks according to the second and third embodiments. The vertical axis shows the DPP and the reflectance, and the horizontal axis shows the groove depth. Tables 2 and 3 also show the results of measuring the C / N of the reproduced signal and the crosstalk from the land 2 outside the tracking groove 3. The wavelength λ of the laser beam irradiated during reproduction is 680 nm, and the refractive index n of the substrate 5 is approximately 1.59.

[0044]

[Table 2]

[0045]

[Table 3]

[0046] In Example 2, as can be seen from FIG. 5 and Table 2, a DPP 0.5 when the depth D _G of the groove 3 is 20 nm, the depth D _G is in the range of 20 nm to 40 nm, The C / N of the reproduced signal is 51.1 dB or more, and the value of crosstalk is -32 dB or less. These values were sufficient for practical use, and the same results as in Example 1 were obtained. In addition Example 3, as can be seen from FIG. 6 and Table 3, a DPP 0.55 when the depth D _G of the groove 3 is 20 nm, the depth D _G is in a range of 20 nm to 40 nm, the reproduction signal Has a C / N of 51.7 dB or more and a crosstalk value of -4.
0 dB or less. These values were sufficient for practical use, and the same results as in Example 1 were obtained. When the depth of the groove 3 was 10 nm, the tracking control could not be performed accurately, and the C / N and crosstalk of the reproduced signal could not be measured in any case.

[0047] Further, from the results of Examples 1 to 3, towards the case of 0.8μm track pitch than 0.6μm is higher and C / N and DPP at the same depth D _G is obtained. Thereby, as the track pitch becomes wider, sufficient C /
N is obtained, and, precisely the range of the depth D _G of the tracking control can be performed grooves 3 it can be seen that widens.

Embodiment 4 FIG. Usually, the pits are formed as shallow or shallow as the grooves. As shown in Examples 1-4,
The range of the depth D _G of the groove when the 20 nm to 40 nm, the depth D _P of the pit 13 is equal to or shallower than the 20 nm to 40 nm. The effect of the pit depth on the reproduction characteristics was investigated.

[0049] and a depth D _P of the depth D _G of the groove 3 and the pit 13 as the same depth, was prepared by the same way as the magneto-optical disc 1 as in Example 1. FIG. 7 is an explanatory diagram of a recording state of the preformat recording area 11 of the magneto-optical disk 1 manufactured in the fourth embodiment. FIG. 8 is a configuration diagram showing preformat information recorded in the preformat recording area 11, where SM is a sector mark. The preformat recording area 11 includes the sector mark recording area 11p and M
An O recording area 11m is provided in the circumferential direction. In the sector mark recording area 11p, only sector marks of preformat information are formed by pits 13, 13,. The pit length was 2.4 μm and the length of the space between the pits was 4.8 μm, and 500 pits were continuously formed. A pit having a length of 4.8 μm and a space between the pits having a length of 2.4 μm was similarly formed.

[0050] Such a magneto-optical disk 1, 20 nm depth D _G of the groove 3, 30nm, 40nm, 50n
m, 60 nm, 80 nm, and 110 nm, and the reproduction characteristics of the sector mark recording area 11p were measured using a spectrum analyzer. Table 4 shows the results. Note that the measurement results were the same for the pit lengths of 2.4 μm and 4.8 μm.

[0051]

[Table 4]

From Table 4, when the pit depth is 30 nm or more,
The C / N of the pit reproduction signal is 51 dB or more. When the pit depth is 20 nm, C / N is 48d.
B, but a value sufficient to detect the start of a sector. Thus, by forming the same extent and depth D _G of the depth D _P and groove pits 13 in the range of 20 nm to 40 nm, manufacturing is simple, sufficient C / N can be obtained, and accurate Thus, a magneto-optical disk capable of performing tracking control can be obtained.

In order to form the VFO of the preformat information as pits, the pit length was set to 0.4 μm and the space between the pits was set to 0.4 μm, and the reproduction characteristics of the pits were measured in the same manner as in Example 3. However, noise was large and measurement was impossible.

In the above-described embodiments and examples, a magneto-optical disk capable of reproducing recorded marks by the double-mask RAD reproducing method has been described. However, the present invention is not limited to this. Different magnetic layers may be provided, as long as they can be reproduced by the RAD reproduction method.

[0055]

As described above, in the present invention, the groove of the magneto-optical recording medium capable of land / groove recording and MSR reproduction has a phase depth of 0.047λ / n to 0.10.
By having λ / n, a sufficient reproduction signal strength of magneto-optically recorded information can be obtained, and accurate tracking control can be performed. Further, by making the phase depth of the pits formed as at least a part of the preformat information substantially equal to that of the grooves, a pit reproduction signal can be obtained with a reproducible intensity, and the production of the magneto-optical recording medium is simplified. For example, the present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a magneto-optical disk of the present invention.

FIG. 2 is a configuration diagram of an apparatus for manufacturing a magneto-optical disk according to the present invention.

FIG. 3 is a diagram showing a magnetization state during reproduction in the magneto-optical disk of the present invention.

FIG. 4 is a graph showing a relationship between a groove depth, a reflectance, and a tracking characteristic in Example 1.

FIG. 5 is a graph showing a relationship between a groove depth, a reflectance, and a tracking characteristic in Example 2.

FIG. 6 is a graph showing the relationship between the groove depth, the reflectance, and the tracking characteristics in Example 3.

FIG. 7 is a diagram illustrating a recording state of a preformat recording area according to a fourth embodiment.

FIG. 8 is a configuration diagram illustrating preformat information according to a fourth embodiment.

FIG. 9 is a diagram showing a magnetization state during reproduction of a magneto-optical disk (RAD reproduction method).

10 is a graph showing the relationship between the phase depth of the groove and the reflectivity of the magneto-optical disk of FIG.

11 is a graph showing the relationship between the groove phase depth and the reproduction characteristics of the magneto-optical disk of FIG.

12 is a graph showing the relationship between the phase depth of the groove and the tracking characteristics of the magneto-optical disk shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 2 Land 3 Groove 4 Magnetic layer 5 Substrate 11 Preformat recording area 11m MO recording area 11p Sector mark recording area 12 Data recording area 13 Pit 14, 15 Recording mark 41 Reproduction layer 42 Intermediate layer 43 Recording layer

Claims (2)

[Claims] 1. A magneto-optical recording medium wherein a recording mark can be formed on each of a groove and a land provided between the grooves, and a recording mark smaller in diameter than a spot diameter of irradiation light for reproduction can be reproduced. The phase depth of the groove is 0.047λ / n to 0.10
λ / n. 2. A recording mark can be formed on each of a groove and a land provided between the groove, and an information recording area on which information is to be recorded and a pre-format are formed on a track formed by the groove and the land. A magneto-optical recording medium having a pre-format recording area on which information is to be recorded and capable of reproducing a recording mark having a diameter smaller than the spot diameter of the reproduction irradiation light;
The phase depth of the sector mark recording area in the preformat recording area is zero, and the pit corresponding to the sector mark is a phase depth of the information recording area of the groove. A magneto-optical recording medium having the same depth as the depth.