JPH09128825A - Magneto-optical recording medium and optical information detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a land and groove recording type magneto-optical information recording medium with which the high-density recording with the decreased crosstalks between adjacent lands and grooves is possible and an optical information detector. SOLUTION: This device consists of the constitution in which the phase differences of polarization components vary with the land parts and groove parts of the optical recording medium with which the land and groove recording is possible. The means thereof consists of the constitution to form the land parts or the land parts and the groove parts of a material having the refractive index different from the refractive index of a transparent substrate on this substrate, the constitution to use the material particularly having double refraction as the material described above and the constitution varying in the thickness or refractive index of the dielectric substance in the land parts and the groove parts. This optical information detector is constituted to have one or two of such magnetic Kerr effect detecting systems which are arranged with electro-optical elements, wavelength plates and particularly half-wave plates as the phase compensation elements of the polarization components.

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 capable of land and groove recording and an optical information detecting device.

[0002]

2. Description of the Related Art At present, optical disks are used as recording media capable of reproducing audio signals and image signals. In particular, magneto-optical disks and phase-change disks are being actively developed as rewritable high density recording media. In order to increase the recording density of an optical disk recording medium that records information in a spiral or concentric form, there are two methods: shortening the track pitch and improving the linear recording density. In any case, it is realized by shortening the wavelength of the semiconductor laser used for recording and reproduction. However, it seems that it will take some time before semiconductor lasers with short wavelengths such as blue and green steadily oscillate continuously at room temperature, and they come to the market at low cost for consumer use. In such a situation, an optical super-resolution method that uses the temperature distribution of the refractive index,
A method is being sought for maximizing the recording density while using a laser having a current wavelength, such as MSR in a magneto-optical disk.

A RAM disk such as a phase-change disk or a magneto-optical disk uses light of the same wavelength when writing and reproducing information, whereas a ROM disk in which information is recorded in advance is short. Pits are formed by using a gas laser having a wavelength. From the side of the RAM disk, the ROM disk is like writing information with light that can be used in the future, although the reproduction conditions are the same.
The M disc is a disadvantage. Therefore, even in the DVD standard, which is drawing attention as a next-generation home video recording medium, the recording capacity of a full-ROM disc is the same as that of the R-type.
It is in a situation where there is no plan to support it with an AM disc.

The land and groove recording is an attractive technique for developing a high density optical recording medium because the recording density can be doubled at the same linear recording density and the same track pitch. In particular, most of the RAM disks currently in use record on either a land or a groove on a substrate in which a groove is formed in advance, and it is desired that recording can be performed on both. For example, in land-and-groove recording on a phase-change disk, Japanese Patent Laid-Open No. 7-130
As disclosed in Japanese Patent Laid-Open No. 006, there has been proposed a method of improving the recording density by adjusting the recording sensitivity in the land portion and the groove portion.

[0005]

By narrowing the track pitch, there arises a problem of crosstalk in which data signals of adjacent areas are mixed in the output signal during reproduction. In land recording or groove recording, since there are grooves or lands between lands or between lands, and there is a gap between areas where information is written, crosstalk is suppressed. However, in the land & groove recording, since the information recording areas are adjacent to each other, the crosstalk reproduction characteristics are greatly affected.
In JP-A-5-62250, the groove depth is set to 1
It is defined as an integral multiple of / 4 wavelength to provide a means for optically suppressing crosstalk. When this method is used, since the 0th-order and 1st-order diffracted lights cancel each other out, the push-pull method cannot be used as a tracking means, and the amount of light reflected from the recording medium and reaching the photodetector is reduced. The problem is that it will end up. An object of the present invention is to provide a magneto-optical recording medium and an optical information detection device capable of high density recording with reduced crosstalk in land & groove recording.

[0006]

The first constitution of the present invention is as follows.
In a magneto-optical recording medium having concentric circles or spiral recording tracks composed of substantially flat land and groove having substantially the same width, and having at least a dielectric film layer, a recording film layer and a reflective film layer thereon, glass or Light fluxes passing through each of the land portion and the groove portion formed on the substrate made of resin are reflected by the recording film made of the magnetic material through the dielectric film layer, and after the multiple interference, the land portion and the groove portion respectively. A magneto-optical recording medium having different reflectances.

In the above-mentioned magneto-optical recording medium, the condition of multiple reflection by the dielectric is different between the land portion and the groove portion, so that the land portion and the groove portion can obtain different reflectances.

Further, different reflectance can be obtained also by a structure in which a land portion or a land portion and a groove portion are formed on a substrate which is optically transparent by a material having a refractive index different from that of the substrate. You can

Also, the land portion, or the land portion and the groove portion, which are different from the substrate and are formed of an optically almost transparent material having birefringence,
It is possible to obtain different reflectances from the land portion and the groove portion.

Also, different reflectivities can be obtained by making the thicknesses of the dielectric layers constituting the magneto-optical recording medium different between the land portion and the groove portion.

Further, different reflectivities can be obtained by making the land portion and the groove portion have different refractive indexes of the dielectric layers constituting the magneto-optical recording medium.

A second structure of the present invention is an optical information detecting device for detecting a signal recorded on the above-mentioned magneto-optical recording medium, and has means for giving an optical phase difference to the magnetic Kerr effect detecting optical system. The present invention relates to an optical information detection device characterized by the above.

In the above-mentioned optical information detecting device used for reading the magneto-optical recording medium, an optical element for giving an optical phase difference is arranged in the optical system for detecting the magnetic Kerr effect. More specifically, the optical information detection device has a configuration in which two magnetic Kerr effect detection systems are arranged and means for providing different phase differences in the respective detection systems.

An electro-optical element can be arranged as a means for giving a phase difference in the above-mentioned optical information detecting device. Furthermore, in the optical information detection device, a half-wave plate is provided as an optical element that gives an optical phase difference, and
The two-wave plate can be arranged to be inclined with respect to the optical axis.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Polycarbonate resin is injection-molded by a conventional method to obtain a substrate having grooves with a groove depth of about 57 nm and a land width / groove width ratio of 1: 1. A low-viscosity UV curable resin is spin-coated on a polycarbonate substrate to a thickness of about 1 μm, and is irradiated with UV rays to be cured. The refractive index of the polycarbonate substrate is 1.58 as an example, whereas the refractive index of the ultraviolet curable resin after ultraviolet curing is 1.47 as an example. A first dielectric layer, a magnetic recording layer, a second dielectric layer, and a reflective layer were formed on this ultraviolet curable resin by a sputtering method. The first dielectric layer has a thickness of 83 n formed by reactive sputtering in a mixed gas of Ar and N ₂ using a Si target.
m is deposited. The flow rate ratio of N _{2 in} the mixed gas is, for example, 20%. The refractive index at this time is 2.04. The Curie temperature is about 200 ° C. on the first dielectric layer.
And a coercive force of about 8 kOe and a good perpendicular magnetic anisotropy, and a magnetic recording layer made of an alloy thin film of a transition metal and a rare earth metal is formed to a thickness of about 22 nm. On top of that, the first
The second dielectric layer having a thickness of 20 nm is formed under the same conditions as those of the dielectric layer, and the reflective layer 6 made of Al having a thickness of 100 nm is further formed. About 1 UV curable resin on the reflective layer
A protective layer is formed by spin coating to a uniform thickness of 0 μm and irradiating with ultraviolet rays.

Although one embodiment of the invention has been described, in the above case, there is a difference in the multiple interference condition of light due to the difference in the thickness of the land and the groove of the first ultraviolet curable resin layer.
A phase difference occurs between the polarized light components in the land portion and the groove portion.

With respect to the magneto-optical medium of the present invention, other modes will be described in detail in Examples, but in any case, a phase difference occurs between the polarization components in the land portion and the groove portion due to the difference in the light interference condition. Since a phase difference occurs in the polarization component between the land part and the groove part, by adjusting the phase compensation condition when reading the magneto-optical signal to the optimum condition for the land part and the groove part, the adjacent groove or land Since light deviates from the phase compensation condition, crosstalk can be reduced.

An optical information detecting device for detecting a signal recorded on the magneto-optical recording medium, which is another constitution of the present invention, will be described. The above-mentioned device is an optical information detection device characterized in that it has means for giving an optical phase difference to the magnetic Kerr effect detection optical system. In particular, it is preferable to have two magnetic Kerr effect detection optical systems, and the two magnetic Kerr effect detection optical systems have means for sharing different phase differences. With this optical information detection device, the phase compensation conditions of the land portion and the groove portion are optimized. Furthermore, two magnetic Kerr effect detection optical systems in which phase optical elements are arranged are provided, and one optical system is allocated for detecting magneto-optical information in the land portion and the other optical system is allocated for detecting magneto-optical information in the groove portion. ,
By optimizing the phase compensation condition of each optical system,
In addition to reducing crosstalk between adjacent land and groove parts, if you first set the phase compensation conditions,
It is not necessary to adjust the phase compensation condition even if the land portion and the groove portion are read alternately. Further, by performing the phase compensation by the electro-optical element, the phase compensation condition when accessing the land portion or the groove portion can be automatically optimized by utilizing the magneto-optical signal. More specifically, by using a half-wave plate tilted as a phase compensation element, the phase difference near the half-wavelength can be adjusted arbitrarily.

As described above, the first configuration of the present invention obtains information on the magneto-optical recording medium having a polarization component having a phase difference between the land portion and the groove portion, and the phase compensation element according to the second configuration of the present invention. By using the optical information detection device including the optical disk, the crosstalk between the adjacent land and groove can be reduced.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording medium and an optical information detecting device according to embodiments of the present invention will be described in detail below with reference to the drawings.

(Disk A) FIG. 1 is a schematic view showing a cross section of a magneto-optical recording medium (disk A) used in the embodiment of the present invention. The polycarbonate substrate 1 having a thickness of 1.2 mm is injection-molded using a Ni stamper. In the production of the Ni stamper, a glass master having a thickness of 12 mm and a diameter of 300 mm, which is uniformly coated with a photoresist having a thickness of about 60 nm by a spin coating method, is used. The photoresist used was a positive type in which the exposed portion was developed. In order to evaporate MIBK, which is the solvent used to dilute the photoresist, the above glass master was baked at 90 ° C. for 30 minutes. For exposure of the master, a wavelength of 45
A 79 nm high power Ar laser light was used. The glass master is rotated at a constant angular velocity of 600 rpm,
The laser light was moved in parallel at a constant speed so that the track pitch of the spirally formed groove was 1.4 μm.

Since the angular velocity is constant, the linear velocity of the exposed portion varies depending on the radial position, and the effective exposure amount (exposure laser power / linear velocity) becomes small at the outer peripheral portion. Was set to be proportional to. The exposure was performed from a radius of 23 mm to 42 mm.
Development was performed by flowing a developing solution onto the master thus exposed by a spin coating method. Several glass masters developed by changing the developing time were prepared, and the groove shape was measured by using STM, and the condition that the ratio of the land width to the groove width was 1: 1 was determined in the groove shape. . As described above, a Ni layer having a thickness of about 70 nm is grown on the exposed and developed glass master by an electroless plating method, and a Ni layer having a thickness of about 300 μm is formed by an electrocasting method, and the back surface is polished. Then, it was peeled from the glass master and washed, and used as a stamper.

Using this stamper, a polycarbonate substrate 1 was injection-molded and the groove shape was measured by STM. As a result, a groove depth of about 57 nm and a land width / groove width ratio of 1: 1 were formed. Was there. A low-viscosity UV curable resin 2 was spin-coated on the polycarbonate substrate 1 to a thickness of about 1 μm, and was irradiated with UV rays to be cured. When the surface of this UV curable resin was examined by STM, smooth irregularities of about ± 10 nm corresponding to the lands and grooves were confirmed, but when compared to the sharp irregularities of the polycarbonate substrate 1, the pattern shown in 2 of FIG. It can be said that the upper part is almost flat as shown in the figure.

The refractive index of the polycarbonate substrate 1 is 1.5
While it was 8, the refractive index of the ultraviolet curable resin 2 after ultraviolet curing was 1.47. A first dielectric layer 3, a magnetic recording layer 4, a second dielectric layer 5, and a reflective layer 6 were formed on this ultraviolet curable resin by a sputtering method.
The first dielectric layer 3 is formed of Ar and N using a Si target.
83 nm thick by reactive sputtering in ₂ gas mixture
Was formed. The flow rate ratio of N _{2 in} the mixed gas is 20%
And The refractive index at this time was 2.04. Magnetic recording consisting of an alloy thin film of a transition metal and a rare earth metal, which has ferrimagnetism with a Curie temperature of about 200 ° C. and exhibits a good perpendicular magnetic anisotropy of about 8 kOe on the first dielectric layer. Layer 4 was deposited to about 22 nm. A second dielectric layer 5 having a thickness of 20 nm was formed thereon and a reflective layer 6 made of Al having a thickness of 100 nm was further formed thereon under the same conditions as the first dielectric layer. Approximately 10μ of UV curable resin on the reflective layer 6
m was spin-coated uniformly and irradiated with ultraviolet rays to form a protective layer 7.

(Disc B) FIG. 2 is a schematic view showing a cross section of a magneto-optical recording medium (disc B) used in the embodiment of the present invention. Thickness 1.2mm, diameter 86
disk A on a glass substrate 8 made of soda-lime glass having a refractive index of 1.52 and having a hole of 15 mm and an inner diameter of 15 mm.
Photoresist coating, baking treatment, exposure and development were performed under the same conditions. The unexposed portion of the photoresist remains on the glass substrate 8 as the land portion 10, the photoresist is removed from the exposed portion, and the groove portion 11 is formed by the glass surface. The groove shape has a groove depth of 55n
m, and the ratio of the land width to the groove width was about 1: 1. A first dielectric layer 3, a magnetic recording layer 4, a second dielectric layer 5, a reflective layer 6, and a protective coat 7 were formed on this under exactly the same conditions as for the disk A.

(Disk C) FIG. 3 is a schematic view showing a cross section of a magneto-optical recording medium (disk C) used in the embodiment of the present invention. On the glass substrate 8 having the same shape and the same properties as those used for the disc B, the disc A
Grooves were formed by the 2P method using the stamper manufactured under the same conditions as those used in 1. An oligomer containing polycarbonate diacrylate as a main component was used as a material, and was cured by high-power ultraviolet light to form a photopolymer layer 12 having a thickness of about 3 μm. On top of this, the first dielectric layer 3, magnetic recording layer 4,
The second dielectric layer 5, the reflective layer 6, and the protective coat 7 were formed.

(Disc D) FIG. 4 is a schematic view showing a cross section of a magneto-optical recording medium used in the embodiment (disc D) of the present invention. A first dielectric layer having a thickness of 50 nm was formed on the polycarbonate substrate manufactured under the same conditions as those for the disk A under the same conditions as those for the disk A, and ion etching was performed using an inert gas. When the cross section of the land and groove portion after ion etching was examined by an electron microscope, the land portion had almost no dielectric layer, while the groove portion had a dielectric layer of about 30 nm left. A dielectric layer of 70n
Then, the land portion dielectric layer 13 and the groove portion dielectric layer 14 have different thicknesses. The magnetic recording layer 4, the second dielectric layer 5, the reflective layer 6, and the protective layer 7 were formed on this under the same conditions as the disk A.

(Disc E) FIG. 5 is a schematic view showing a cross section of a magneto-optical recording medium (disc E) used in the embodiment of the present invention. A resin was spin-coated to a thickness of 1 μm on a polycarbonate substrate prepared under the same conditions as the disk A. Baking was performed at 90 ° C. for 30 minutes to remove the water content of the resin. This substrate was etched in an inert gas until the resin in the land part was used up. In this state, a dielectric layer having a thickness of 80 nm was formed under the same conditions as the disk A, and then the resin in the groove and the dielectric layer were removed using an organic solvent. On top of this,
The deposition of the dielectric layer was carried out further 130nm as 8% flow ratio of N ₂ occupying the mixed gas of Ar and N _2. The refractive index at this time was 2.30. Next, ion etching with an inert gas is carried out, and the dielectric layer of the land portion is about 130
Most of the nm was removed. Through the above steps, the low-refractive-index dielectric layer 15 was formed in the groove portion, and the high-refractive-index dielectric layer 16 was formed in the land portion with approximately the same film thickness of about 80 nm.
On top of this, the magnetic recording layer 4 and the second
The dielectric layer 5, the reflective layer 6, and the protective layer 7 were formed.

FIG. 6 is a schematic view showing an example of the optical information detecting device used in the embodiment of the present invention. The light emitted from the semiconductor laser 19 is collimated by the collimator lens 20 onto the magneto-optical disk 17 which is rotated by the spindle motor 18, and is converted into parallel light.
The light is focused by the objective lens 22 via (hereinafter referred to as PBS). In the embodiment of the present invention, the semiconductor laser 19 having a wavelength of 680 nm and the objective lens 22 having an NA of 0.55 are used. The light reflected by the magneto-optical disk 17 is reflected by the PBS 21, PBS 24, and cylindrical lens 2.
Via the converging lens 26 via the 5
It is focused on 7. The signal of the four-division photodetector 27 is used as a focus servo signal by the astigmatism method and a tracking servo signal by the push-pull method to control the movement of the objective lens to perform focusing and tracking. The switching of the tracking to the land part and the groove part uses the positive / negative of the inclination of the signal at the zero cross position of the push-pull signal. The light that has passed through the PBS 24 passes through the half-wave plate 28 and the converging lenses 30, 3
1 is focused on the photodetectors 32 and 33, respectively.
A magneto-optical signal is read from the difference signal of the photo detectors 32 and 33.

FIG. 7 shows another example of the optical information detecting device used in the present invention. Up to PBS24, the above-mentioned FIG.
Although it has the same structure as that of the optical information detection device of No. 1, the half mirror prism 34 divides the light into two as an optical system for reading out a magneto-optical signal, and the half-wave plates 35, 3
After passing through 6, the light passes through the Wollaston prism 37 and, at that time, each light is divided into two directions depending on the polarization direction, and is converged by the converging lenses 38 and 39 onto the two-division diodes 40 and 41, respectively. Is focused on. This device has an advantage that the phase compensation of the polarization components of the land portion and the groove portion can be performed separately. Further, since the extinction ratio is higher than that of the PBS by using the Wollaston prism 37, the noise of the reproduction signal can be reduced. Further, the device can be downsized.

In the photodetector of FIG. 6, a Babinet Soleil plate is used instead of the half-wave plate 28 in the device A.
And In the photodetector of FIG. 7, two Babinet Soleil plates are arranged instead of the half-wave plates 35 and 36, and the device B is used.
And A device C is one in which an electro-optical element is arranged instead of the half-wave plate 28 of FIG. In FIG. 7, 1
A device in which the / 2 wavelength plates 35 and 36 are separately arranged obliquely with respect to the optical axis is referred to as a device D.

When the light is focused on each of the land portion and the groove portion of the disk A, the reflectance is 68% of the land portion.
On the other hand, the groove portion was 62%. The disk A relates to claim 2 of the present invention. The disk B whose structure is shown in FIG. 2 also relates to claim 2 of the present invention because of its structure. In Disk C, polycarbonate diacrylate was irradiated with high-power ultraviolet light to be cured, and thus birefringence due to the orientation of molecules was confirmed. The disk C relates to claim 3 of the present invention. The disk D whose structure is shown in FIG. 4 is defined by claim 4 of the present invention because of its structure. Fifth, the disk E having the structure is defined by claim 5 of the present invention due to its structure.

With respect to the optical information detecting device, the devices A to D are related to claims 6 to 9 of the present invention due to the configuration thereof.

From device A for disks A-E above
Crosstalk was investigated using D. Crosstalk amount
Is the data of 5 adjacent land or groove areas
Is erased using a constant magnetic field and laser light, then the center
Marks with a mark length of 2.0 μm on each land or groove
Is recorded by the magnetic field modulation method and its carrier level C_C Measure
The land or groove on both sides adjacent to each other.
The highest of the measured values of the carrier level
The value is C_MAX And crosstalk C_CR= C_MAX -C _C Seeking
I did. Crosstalk amount for land and groove
Table 1 shows the one with the largest value including the sign.
I have.

[0035] The write recording power C _C measures the writing power dependency of the C _C, was set to a power P _S whose value is saturated. The playback and power are all 0.7.
It was performed at a constant 4 mW. Although not shown in this embodiment, the read power can be increased by shifting the write power sensitivity of the magneto-optical recording medium to the high power side, so that the recording characteristics are improved. The rotation speed of the disk was set so that the linear velocity at the measurement radius position was 5 m / sec. In the device A and the device C, the Babinet Soleil plate or the electro-optical element is adjusted with respect to the tracked land portion or groove portion so that the C / N of 1.25 MHz corresponding to the 2 μm mark is maximized. Then, the carrier level was measured by tracking to the adjacent groove or land, and the crosstalk was obtained. When the electro-optical element is used in the device C, a structure is provided in which the carrier level signal is fed back and the phase can be automatically compensated.

In the devices B and D, the optical system focused on the two-divided photodetector 40 is assigned to the land portion, and the optical system focused on the two-divided photodetector 41 is assigned to the groove portion. In the system, crosstalk was measured by adjusting the Babinet Soleil plate or the half-wave plate to optimize the phase compensation condition.

[0037]

[Table 1]

FIG. 8 shows the result of examining the write power of the crosstalk by using the device A for the disk B having the smallest crosstalk as compared with the others. It can be seen that the crosstalk satisfies the condition of −30 dB or less in the write power range of 4.6 to 5.9 mW. Further, when the dependency of C / N on the mark length was examined with the same disk and the same device, a C / N of 46 dB was obtained even with a mark length of 0.5 μm. Therefore, the shortest mark length is 0.55 μm
FIG. 9 shows the result of examining the write power dependence of the jitter value for the random signal of the 1-7 modulation method. The read laser power was 0.74 mW, which is the same as the above-mentioned crosstalk measurement. The signal is written to the groove first and then to the land.

Although the jitter value in the groove portion is high due to the influence of cross erase, the write power is 4.5 to 6.
A jitter value of 10% or less was obtained in the range of 5 mW. Further, when the shortest mark length was measured with 0.48 μm, the jitter power margin was narrow, but a jitter value of 10% or less was obtained.

[0040]

As described in detail above, when land-and-groove recording is performed using the magneto-optical recording medium according to the present invention, the phase difference of the polarization component of the light during reading differs between the land portion and the groove portion. . When information is recorded / reproduced using the magneto-optical recording medium of the present invention and the optical information detection device of the present invention, optimum phase compensation can be performed for each of the land portion and the groove portion. By optimizing the phase compensation condition for the land or groove, the crosstalk signal from the adjacent groove or land deviates from the phase compensation condition, thereby reducing the signal amplitude. With this action, the effect of reducing crosstalk can be obtained in the magneto-optical recording medium and the optical information detecting device according to the present invention.

Due to the effect of reducing the crosstalk, high density recording becomes possible in the land & groove recording of the magneto-optical recording medium. As shown in this embodiment, when the magneto-optical recording medium and the photodetector according to the present invention are used, in land and groove recording with a track pitch of 1.4 μm, the shortest mark length is 0.48 μm and 1-7 modulation random. When the recording / reproducing of the signal was examined, a value of 10% or less was obtained as the jitter characteristic. As a result, by using a magneto-optical disk having almost the same track pitch as the ISO standard 3.5-inch recording capacity 230 MB magneto-optical disk, a recording capacity of 1.5 GB which is more than twice that of the same 3.5-inch ISO standard 640 MB disk is obtained. It turned out that there is an effect to be obtained.

Since the technique according to the present invention is universal regardless of the wavelength of light used in the optical information detecting device, a green or blue semiconductor laser will be used as a light source of the optical information detecting device in the future. Also, the above effect can be obtained.

The magneto-optical recording medium of the present invention can be manufactured with the same structure as that of the existing magneto-optical recording medium except for the structure for producing the difference in the phase difference of the polarization component between the land portion and the groove portion, so that the production cost can be suppressed. You can

In the optical information detecting device of the present invention, the existing optical element is used as means for compensating the phase,
The burden on drive device manufacturing is small. As described in claim 7, by using two magnetic Kerr effect detection systems each having an element for performing phase compensation, adjustment of the optical element including phase compensation can be performed by initial adjustment at the time of manufacturing. Further, as described in claim 8, the phase adjustment can be electrically and automatically performed by using the electro-optical element as the phase compensation means. As described above, in the optical information detection device according to the present invention, it is possible to obtain the effects of low cost and good convenience in manufacturing and adjustment.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross section of a substrate of a disk A in an example of the present invention.

FIG. 2 is a schematic view showing a cross section of the substrate of the disk B in the example of the present invention.

FIG. 3 is a schematic view showing a cross section of the substrate of the disk C in the example of the present invention.

FIG. 4 is a schematic view showing a cross section of the substrate of the disk D in the example of the present invention.

FIG. 5 is a schematic diagram showing a cross section of a substrate of a disk E according to an example of the present invention.

FIG. 6 is a diagram illustrating a photodetection device (apparatus A,
It is a schematic diagram which shows the structure of C).

FIG. 7 is a diagram illustrating a photodetection device (device B, according to an embodiment of the present invention).
It is a schematic diagram which shows the structure of D).

FIG. 8 is a graph showing write power dependence of crosstalk (disk B, device A) in the example of the present invention.

FIG. 9 is a graph showing the write power dependence of the jitter characteristic in the example of the present invention.

[Explanation of symbols]

 1. Polycarbonate substrate 2. UV curable resin 3. First dielectric layer 4. Magnetic recording layer 5. Second dielectric layer 6. Reflective layer 7. Protective layer 8. Glass substrate 9. Photoresist 10. Land section 11. Groove part 12. Photopolymer 13. Land portion dielectric layer 14. Groove part dielectric layer 15. Low refractive index dielectric layer 16. High refractive index dielectric layer 17. Magneto-optical disk 18. Spindle motor 19. Semiconductor laser 20. Collimator lens 21. Polarization beam splitter (PBS) 22. Objective lens 23. Levitation magnetic head 24. PBS 25. Cylindrical lens 26. Converging lens 27.4 split photodetector 28.1 / 2 wavelength plate 29. PBS 30. Converging lens 31. Converging lens 32. Photodetector 33. Photodetector 34. Half mirror prism 35.1 / 2 wave plate 36.1 / 2 wave plate 37. Wollaston prism 38. Converging lens 39. Converging lens 40.2 split photo detector 41.2 split photo detector

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tomoaki Hara 3-78 Ina-cho, Kita-Adachi-gun, Saitama Kato Heights 306 (72) Inventor Kenji Morita 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Within the corporation

Claims (9)

[Claims] 1. A magneto-optical recording comprising a concentric or spiral substantially flat recording track composed of lands and grooves having substantially the same width, and having at least a dielectric film layer, a recording film layer and a reflective film layer thereon. In the medium, a light flux passing through each of a land portion and a groove portion formed on a substrate made of glass or resin is reflected by a recording film made of a magnetic material through a dielectric film layer, and the land portion after multiple interference A magneto-optical recording medium characterized in that each groove portion has a different reflectance. 2. The magneto-optical recording medium according to claim 1, wherein the land portion or the land portion and the groove portion are formed of an optically substantially transparent material having a refractive index different from that of the substrate. 3. The magneto-optical recording medium according to claim 1, wherein the land portion, or the land portion and the groove portion, are formed of an optically substantially transparent material different from the substrate and having birefringence. 4. The magneto-optical recording medium according to claim 1, wherein the thickness of the dielectric layer is different between the land portion and the groove portion. 5. The magneto-optical recording medium according to claim 1, wherein the dielectric layers on the land portion and the groove portion have different refractive indexes. 6. An optical information detecting device, wherein the optical information detecting device for detecting a signal recorded on the magneto-optical recording medium has means for giving an optical phase difference to a magnetic Kerr effect detecting optical system. 7. The optical information detecting device according to claim 6, further comprising two magnetic Kerr effect detection optical systems, and the two magnetic Kerr effect detection optical systems have means for sharing different phase differences. The optical information detection device described in 1. 8. The optical information detecting device according to claim 6, wherein the means for providing the phase difference is an electro-optical element. 9. The optical information according to claim 6, wherein the means for giving the phase difference is a half-wave plate, and the half-wave plate is inclined with respect to the optical axis. Detection device.