JP2004139735A - Magneto-optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a land and groove recording magneto-optical recording medium in which cross talk between adjacent land section and groove section is reduced and high density recording is made possible. <P>SOLUTION: In an optical recording medium which is capable of conducting land and groove recording, the land section and the groove section are constituted so that phase differences of the polarized components are made different. As the concrete means, the followings are considered, i.e., the land section is formed on a transparent substrate using the material having a refractive index that differs from the refractive index of the substrate, the land and the groove sections are formed using the material having a refractive index that is made different from the refractive index of the substrate, the sections are formed specifically using material having double refractivity and the thickness or the refractivity of the dielectric bodies is made different in the land section and the groove section. Having provided the above constitutions, signals recorded in the groove section or the land section are selectively read by phase controlling the phase differences, which are generated by mutual interference of the light beams being reflected from the land section and the groove section, using a phase compensating element. <P>COPYRIGHT: (C)2004,JPO

Description

<< The present invention relates to a magneto-optical recording medium capable of performing land & groove recording.

光 デ ィ ス ク Currently, optical disks are used as recording media that can reproduce audio signals and image signals. In particular, magneto-optical disks and phase change disks are being actively developed as rewritable high-density recording media. There are two methods for increasing the recording density of an optical disk recording medium that records information spirally or concentrically, that is, shortening the track pitch and improving the linear recording density. In any case, this is realized by shortening the wavelength of the semiconductor laser used for recording and reproduction. However, it will take some time before semiconductor lasers of short wavelengths such as blue and green are stably continually oscillated at room temperature, and are commercially available at low cost for commercial use. In such a situation, a method for maximizing the recording density while using a laser of the current wavelength, such as an optical super-resolution method using a temperature distribution of a refractive index and an MSR in a magneto-optical disk. Is being sought.

RAM disks such as phase-change disks and magneto-optical disks use light of the same wavelength when writing and reproducing information, whereas ROM disks in which information is recorded in advance use short-wavelength gas. Pits are formed using a laser or the like. From the viewpoint of the RAM disk, the ROM disk has the same reproduction conditions, but it is like writing information with light that can be used in the future. Disadvantageous. For this reason, even in the DVD standard, which has attracted attention as a next-generation video recording medium for home use, no proposal has been made to support the recording capacity of a full ROM disk with a RAM disk of the same size.

Land and groove recording is an attractive technique for developing a high-density optical recording medium because the recording density can be doubled if the recording density is the same and the track pitch is the same. In particular, most of currently used RAM disks record data on either a land or a groove on a substrate in which a groove is formed in advance, and it is desired that data can be recorded on both of them. For example, in land & groove recording of a phase change type disc, a method of improving recording density by adjusting recording sensitivity in a land portion and a groove portion has been proposed as disclosed in Japanese Patent Application Laid-Open No. Hei 7-130006. I have.
JP-A-7-130006

(4) By reducing the track pitch, there is a problem of crosstalk in which data signals in adjacent areas are mixed in output signals during reproduction. In land recording or groove recording, a groove or land exists between lands or between grooves, and there is a gap between areas where information is written, so that crosstalk is suppressed. However, in the land & groove recording, since the information recording areas are adjacent to each other, the influence on the reproduction characteristics of crosstalk is large. Japanese Patent Application Laid-Open No. 5-62250 provides a means for optically suppressing crosstalk by defining the depth of a groove to be an integral multiple of 1/4 wavelength. When this method is used, the zero-order and first-order diffracted lights cancel each other out, so that 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. This is a problem. An object of the present invention is to provide a magneto-optical recording medium capable of high-density recording with reduced crosstalk in land and groove recording.

According to the structure of the present invention, in a magneto-optical recording medium having a dielectric layer, a recording layer, and a reflective layer on a substrate having land portions and groove portions which are substantially flat and have substantially the same width, polarized incident light is applied to the land portion. The light condensed on the recording track of the groove portion and reflected from the land portion and the groove portion interfere with each other, and the land portion and the groove portion are formed such that a polarization component thereof generates a phase difference. This is a characteristic magneto-optical recording medium.

In the above-described magneto-optical recording medium, the light reflected from the land and the groove interferes with each other, so that a polarization component of the reflected light causes a phase difference, and the phase difference is controlled by a phase compensating means. Alternatively, the signal from the groove portion can be detected with a good C / N ratio and with suppressed crosstalk.

In addition, the land portion, or the land portion and the groove portion are formed on the substrate with an optically substantially transparent material having a different refractive index from the substrate, so that reflected light A phase difference can be generated in the polarization component.

The land portion, or the land portion and the groove portion are different from the substrate and are formed on the substrate with an optically substantially transparent material having birefringence, so that reflected light A phase difference can be generated in the polarization component.

Also, a phase difference can be generated in the polarization component of the reflected light by using a configuration in which the thickness of the dielectric layer is different between the land portion and the groove.

Further, a phase difference can be generated in the polarization component of the reflected light by making the refractive index of the dielectric layer constituting the magneto-optical recording medium different between the land portion and the groove portion.

The optical information detecting device for detecting a signal recorded on the magneto-optical recording medium has a means for performing optical phase compensation in a magnetic Kerr effect detecting optical system.

光 In the optical information detecting device used for reading from the above-described magneto-optical recording medium, an optical element for performing optical phase compensation is arranged in an 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 each detection system has means for providing a different amount of phase compensation.

(4) As an optical element for performing optical phase compensation in the optical information detecting device, an electro-optical element or a half-wave plate that is arranged to be inclined with respect to the optical axis can be used.

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 light at the time of reading differs between the land and the groove. If information is recorded / reproduced using the magneto-optical recording medium of the present invention and the optical information detecting device of the present invention, optimal phase compensation can be performed for each of the lands and the grooves. 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. By this effect, in the magneto-optical recording medium and the optical information detecting device according to the present invention, an effect of reducing crosstalk can be obtained.

(4) Due to this crosstalk reduction effect, high-density recording becomes possible in land and groove recording of a 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, land and groove recording with a track pitch of 1.4 μm and 1-7 modulation random with a shortest mark length of 0.48 μm are performed. When the recording / reproduction of the signal was examined, a value of 10% or less was obtained as the jitter characteristic. Thus, using a magneto-optical disk having a track pitch substantially the same as that of the 3.5-inch ISO standard 230 MB recording magnetic 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. It turned out that there was an effect obtained.

The technology according to the present invention is universal irrespective of the wavelength of light used in the optical information detecting device, and therefore, even if a green or blue semiconductor laser is used as a light source of the optical information detecting device in the future, The effect of is obtained.

光 The magneto-optical recording medium of the present invention can be manufactured with the same configuration as the current magneto-optical recording medium, except for a structure that creates a difference in the phase difference of the polarization component between the land and the groove, so that the production cost can be reduced.

In the optical information detecting device, an existing optical element is used as a means for compensating the phase, and the burden on manufacturing the drive device is small. By using two magnetic Kerr effect detection systems having an element for performing phase compensation, adjustment of the optical element including phase compensation can be an initial adjustment at the time of manufacturing. Further, by using an electro-optical element as the phase compensating means, the phase can be automatically and automatically adjusted. As described above, in the optical information detection device according to the present invention, there is obtained an advantage that manufacturing and adjustment are low cost and convenient.

A polycarbonate resin is injection-molded by a conventional method to obtain a substrate in which a groove is formed with a groove depth of about 57 nm and a ratio of land width to groove width of 1: 1. A low-viscosity UV-curable resin is spin-coated on a polycarbonate substrate to a thickness of about 1 μm, and cured by irradiating UV rays. The refractive index of the polycarbonate substrate is, for example, 1.58, while the refractive index of the ultraviolet-curable resin after ultraviolet curing is, for example, 1.47. A first dielectric layer, a magnetic recording layer, a second dielectric layer, and a reflective layer were formed on the ultraviolet curable resin by a sputtering method. The first dielectric layer is formed to a thickness of 83 nm by reactive sputtering in a mixed gas of Ar and N ₂ using a Si target. The flow ratio of N _{2 in} the mixed gas is, for example, 20%. The refractive index at this time is 2.04. Magnetic recording comprising, on the first dielectric layer, an alloy thin film of a transition metal and a rare-earth metal having ferrimagnetism having a Curie temperature of about 200 ° C. and a good coercive force of about 8 kOe and exhibiting good perpendicular magnetic anisotropy A layer is deposited to a thickness of about 22 nm. A 20-nm-thick second dielectric layer is formed thereon under the same conditions as the first dielectric layer, and a 100-nm-thick reflective layer 6 made of Al is formed thereon. On the reflective layer, a UV curable resin is spin-coated uniformly at about 10 μm and irradiated with UV rays to form a protective layer.

Although an embodiment of the present invention has been described, in the above case, a difference in the multiple interference condition of light due to a difference in thickness between the land and the groove of the first ultraviolet curable resin layer causes a difference between the land portion and the groove. A phase difference occurs in the polarization component in the portion.

光 Regarding the magneto-optical medium of the present invention, other embodiments will be described in detail in the examples, but in any case, a phase difference occurs between the polarization components in the land portion and the groove portion due to a difference in light interference conditions. Since a phase difference occurs in the polarization component between the land portion and the groove portion, the phase compensation condition for reading out the magneto-optical signal is adjusted to the optimum condition for the land portion and the groove portion, so that the phase difference from the adjacent groove or land can be reduced. Since light deviates from the phase compensation condition, crosstalk can be reduced.

A description will now be given of an optical information detection device for detecting a signal recorded on the magneto-optical recording medium, which is another configuration of the present invention. The above-described device is an optical information detecting device having means for giving an optical phase difference to a magnetic Kerr effect detecting optical system. In particular, it is desirable to have two magnetic Kerr effect detection optical systems, and the two magnetic Kerr effect detection optical systems each have means for sharing a different phase difference. With this optical information detection device, the phase compensation conditions of the land portion and the groove portion are optimized. Further, two magnetic Kerr effect detecting optical systems having phase optical elements 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 conditions of each optical system, the crosstalk between adjacent lands and grooves can be reduced, and if the phase compensation conditions are set first, the lands and grooves can be reduced. It is not necessary to adjust the phase compensation condition even if the signals are read alternately. Further, by performing the phase compensation using the electro-optical element, the phase compensation condition when accessing the land or the groove can be automatically optimized using the magneto-optical signal. More specifically, by using a half-wave plate inclined as a phase compensation element, the phase difference around the half wavelength can be arbitrarily adjusted.

As described above, according to the first configuration of the present invention, information on a magneto-optical recording medium having a phase difference in polarization components between the land portion and the groove portion was obtained, and the phase compensating element was included according to the second configuration of the present invention. By performing reading using the optical information detection device, crosstalk between adjacent lands and grooves can be reduced.

Hereinafter, an optical recording medium and an optical information detecting device according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a cross section of a magneto-optical recording medium (disk A) used in an embodiment of the present invention. The polycarbonate substrate 1 having a thickness of 1.2 mm is obtained by injection molding using a Ni stamper. In the production of the Ni stamper, a glass master having a flatness of 12 mm in thickness and 300 mm in diameter, which is uniformly coated with a photoresist having a thickness of about 60 nm by spin coating, is used. The photoresist used was a positive type in which exposed portions were developed. The above glass master was baked at 90 ° C. for 30 minutes in order to evaporate MIBK, a solvent used for diluting the photoresist. For exposure of the master, a high-output Ar laser beam having a wavelength of 4579 nm was used. The glass master was rotated at a constant rotational angular velocity of 600 rpm, and was translated at a constant speed with respect to the laser beam so that the track pitch of the spiral groove was 1.4 μm.

Since the angular velocity is constant, the linear velocity of the exposed portion differs depending on the radial position, so that the effective exposure amount (exposure laser power / linear velocity) decreases at the outer peripheral portion, so that the exposure power is proportional to the radial position. Was set as follows. Exposure was performed from a radius of 23 mm to 42 mm. A developing solution was applied to the master thus exposed by spin coating to perform development. Several glass masters were developed by changing the development time, and their groove shapes were measured using STM. The conditions under which the ratio of land width to groove width in the groove shape was 1: 1 were determined. . 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 further formed by an electroforming method, and the back surface is polished. The glass substrate was peeled off and washed and used as a stamper.

(4) Using this stamper, the polycarbonate substrate 1 was injection-molded and its groove shape was measured by STM. As a result, a groove was formed with a groove depth of about 57 nm and a ratio of land width to groove width of 1: 1. A low-viscosity ultraviolet-curable resin 2 was spin-coated on a polycarbonate substrate 1 to a thickness of about 1 μm, and cured by irradiating ultraviolet rays. When the surface of the ultraviolet curable resin was examined by STM, gentle unevenness of about ± 10 nm corresponding to the land and the groove was confirmed. However, when compared with the sharp unevenness of the polycarbonate substrate 1, a schematic diagram of FIG. It can be said that the upper portion is almost flat as shown in FIG.

While the refractive index of the polycarbonate substrate 1 was 1.58, 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 the ultraviolet curable resin by a sputtering method. The first dielectric layer 3 was formed to a thickness of 83 nm by reactive sputtering in a mixed gas of Ar and N ₂ using a Si target. The flow rate ratio of N _{2 in} the mixed gas was 20%. The refractive index at this time was 2.04. Magnetic recording comprising, on the first dielectric layer, an alloy thin film of a transition metal and a rare-earth metal having ferrimagnetism having a Curie temperature of about 200 ° C. and a good coercive force of about 8 kOe and exhibiting good perpendicular magnetic anisotropy Layer 4 was deposited to a thickness of about 22 nm. A 20-nm-thick second dielectric layer 5 was formed thereon under the same conditions as the first dielectric layer, and a 100-nm-thick reflective layer 6 of Al was formed thereon. On the reflective layer 6, a UV curable resin was spin-coated uniformly at about 10 μm and irradiated with UV to form a protective layer.

FIG. 2 is a schematic diagram showing a cross section of a magneto-optical recording medium (disk B) used in the embodiment of the present invention. On a glass substrate 8 made of soda lime glass having a refractive index of 1.52 and a hole having a thickness of 1.2 mm, a diameter of 86 mm, and an inner diameter of 15 mm, a photoresist coating, baking treatment, exposure and development were performed under the same conditions as for the disk A. went. The unexposed portion of the photoresist remains on the glass substrate 8 as a land portion 10, the exposed portion is removed of the photoresist, and a groove portion 11 is formed by the glass surface. The groove shape had a groove depth of 55 nm and a ratio of land width to groove width of approximately 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 thereon under exactly the same conditions as for the disk A.

FIG. 3 is a schematic diagram showing a cross section of a magneto-optical recording medium (disk C) used in an embodiment of the present invention. A groove was formed on a glass substrate 8 having the same shape and the same properties as those used for the disc B by a 2P method using a stamper manufactured under the same conditions as those used for the disc A. The photopolymer layer 12 having a thickness of about 3 μm was formed by using an oligomer having polycarbonate diacrylate as a main component and curing the material with high-power ultraviolet light. 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 thereon under exactly the same conditions as for the disk A.

FIG. 4 is a schematic diagram showing a cross section of the magneto-optical recording medium used in the embodiment (disk 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 for the disk A under the same conditions as for the disk A, and ion-etched using an inert gas. A cross section of the land and the groove portion after the ion etching was examined by an electron microscope. As a result, almost no dielectric layer was present in the land portion, but a dielectric layer of about 30 nm remained in the groove portion. A dielectric layer was further formed thereon to a thickness of 70 nm, and the land dielectric layer 13 and the groove dielectric layer 14 had different thicknesses. On this, the magnetic recording layer 4, the second dielectric layer 5, the reflective layer 6, and the protective layer 7 were formed under the same conditions as for the disk A.

(Disk E) FIG. 5 is a schematic diagram showing a cross section of a magneto-optical recording medium (disk E) used in the embodiment of the present invention. A resin was spin-coated on a polycarbonate substrate manufactured under the same conditions as for the disk A to a thickness of 1 μm. 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 portion disappeared. In this state, a dielectric layer having a thickness of 80 nm was formed under the same conditions as for the disk A, and then the resin and the dielectric layer in the groove portions were removed using an organic solvent. On this was further performed 130nm the deposition of the dielectric layer the flow ratio of N ₂ occupying the mixed gas of Ar and N ₂ as 8%. At this time, the refractive index was 2.30. Next, ion etching with an inert gas was performed to remove almost all of the dielectric layer of about 130 nm in the land portion. By the above-described 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 this, a magnetic recording layer 4, a second dielectric layer 5, a reflective layer 6, and a protective layer 7 were formed under the same conditions as for the disk A.

FIG. 6 is a schematic diagram 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 converted into parallel light by a collimator lens 20 and condensed by an objective lens 22 via a polarizing beam splitter 21 (hereinafter referred to as PBS) on a magneto-optical disk 17 rotated by a spindle motor 18. 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 passes through the PBS 21, the PBS 24, and the cylindrical lens 25, and is condensed on the quadrant photodetector 27 by the converging lens 26. The signals of the quadrant photodetector 27 are used as a focus servo signal by an astigmatism method and a tracking servo signal by a push-pull method to control the movement of the objective lens to perform focusing and tracking. The switching of tracking to the land and groove portions utilizes the positive or negative of the signal slope at the zero cross position of the push-pull signal. The light passing through the PBS 24 is condensed on the photodetectors 32 and 33 by the converging lenses 30 and 31 via the half-wave plate 28. A magneto-optical signal is read from the difference signal between the photo detectors 32 and 33.

FIG. 7 shows another example of the optical information detecting device used in the present invention. The structure up to the PBS 24 is the same as that of the optical information detecting device of FIG. 6 described above. However, as an optical system for reading out a magneto-optical signal, the light is divided into two by a half mirror prism 34, and a half-wave plate 35, After passing through 36, the light passes through a Wollaston prism 37. At this time, each light beam is split into two directions depending on the polarization direction. Is collected. 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, by using the Wollaston prism 37, the extinction ratio is higher than that of PBS, so that the noise of the reproduced signal can be reduced. Further, the size of the device can be reduced.

(6) In the photodetector shown in FIG. 6, a device using a Babinet Soleil plate instead of the half-wave plate 28 is referred to as a device A. The optical inspection apparatus shown in FIG. 7 in which two Babinet Soleil plates are arranged instead of the half-wave plates 35 and 36 is referred to as a device B. A device C in which an electro-optical element is arranged instead of the half-wave plate 28 in FIG. In FIG. 7, a device D is a device in which the half-wave plates 35 and 36 are separately arranged obliquely with respect to the optical axis.

反射 When the light was condensed on each of the land portion and the groove portion of the disk A, the reflectivity was 62% for the land portion and 62% for the groove portion. The disk A is according 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 from the configuration. In the disk C, the polycarbonate diacrylate was cured by irradiating high-power ultraviolet light to the polycarbonate diacrylate, so that birefringence due to molecular orientation was confirmed. The disk C is according to claim 3 of the present invention. The disk D whose structure is shown in FIG. 4 is related to claim 4 of the present invention because of its structure. The disk E whose structure is shown in FIG. 5 is related to claim 5 of the present invention because of its structure.

Regarding the optical information detecting device, the devices A to D are according to claims 6 to 9 of the present invention, respectively, due to the configuration.

Crosstalk was examined for the above-described disks A to E using the devices A to D. The crosstalk amount is determined by erasing data of five adjacent lands or groove areas using a constant magnetic field and laser light, and then recording a mark having a mark length of 2.0 μm on the center land or groove by a magnetic field modulation method. After measuring the carrier level C _C , the adjacent lands or grooves are reproduced, and the higher value of the measured carrier levels is set as C _MAX , and the crosstalk C _CR = C _MAX −C Asked for _C. The crosstalk amount was measured for each of the land and the groove, and the larger one including the sign is shown in Table 1.

Writing recording power C _C measures the writing power dependency of the C _C, was set to a power P _S whose value is saturated. Reproduction and power were all performed at a constant 0.74 mW. Although not shown in this embodiment, by shifting the write power sensitivity of the magneto-optical recording medium to a higher power side, the reproducing power can be increased, and 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 apparatus A and the apparatus C, the Babinet Soleil plate or the electro-optical element is adjusted with respect to the tracked land or groove so that the 1.25 MHz C / N corresponding to the 2 μm mark is maximized. In this state, tracking was performed on an adjacent groove portion or land portion to measure a carrier level, and crosstalk was obtained. When an electro-optical element is used in the device C, a structure is provided in which a carrier level signal is fed back to automatically compensate for phase.

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

FIG. 8 shows the result of examining the write power of crosstalk using the apparatus A for the disc 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 when the write power is in the range of 4.6 to 5.9 mW. Furthermore, when the mark length dependence of the C / N was examined using the same disk and the same apparatus, a C / N of 46 dB was obtained even with a mark length of 0.5 μm. FIG. 9 shows the result of examining the write power dependency of the jitter value for a 1-7 modulation type random signal having the shortest mark length of 0.55 μm. The reading laser power was set at 0.74 mW, which is the same as the crosstalk measurement described above. The signal is first written to the groove and then to the land.

(4) Although the jitter value in the groove portion was high due to the influence of cross erase, a jitter value of 10% or less was obtained when the write power was in the range of 4.5 to 6.5 mW. Furthermore, when the measurement was performed with the shortest mark length set to 0.48 μm, a jitter value of 10% or less was obtained although the power margin of the jitter was narrow.

FIG. 3 is a schematic diagram showing a cross section of a substrate of a disk A in an example of the present invention. FIG. 3 is a schematic diagram showing a cross section of a substrate of a disk B in an example of the present invention. FIG. 3 is a schematic diagram showing a cross section of a substrate of a disk C in an example of the present invention. FIG. 3 is a schematic diagram illustrating a cross section of a substrate of a disk D according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a cross section of a substrate of a disk E according to an embodiment of the present invention. It is a schematic diagram which shows the structure of the photodetector (apparatus A, C) in the Example of this invention. It is a schematic diagram which shows the structure of the photodetector (device B, D) in the Example of this invention. 4 is a graph showing the write power dependency (disk B, device A) of crosstalk in the example of the present invention. 5 is a graph showing the write power dependence of jitter characteristics in an example of the present invention.

Explanation of reference numerals

1. 1. Polycarbonate substrate 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 section 12. Photopolymer 13. Land part dielectric layer 14. 14. Groove portion dielectric layer 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. Polarizing beam splitter (PBS)
22. Objective lens 23. Flying magnetic head 24. PBS
26. Convergent lens 27.4 split photodetector 28.1 / 2 wavelength plate 29. PBS
30. Convergent lens 31. Convergent lens 32. Photodetector 33. Photodetector 34. Half mirror prism 35.1 / 2 wavelength plate 36.1 / 2 wavelength plate 37. Wollaston prism 38. Convergent lens Convergent lens 40.2 split photodetector 41.2 split photodetector

Claims (5)

On a magneto-optical recording medium having a dielectric layer, a recording layer and a reflective layer on a substrate having land portions and groove portions having substantially flat and substantially equal widths,
The polarized incident light is condensed on the recording tracks of the lands and grooves, and the lights reflected from the lands and grooves interfere with each other, so that the lands and the grooves have a phase difference in their polarization components. A magneto-optical recording medium comprising a groove portion. The land portion, or the land portion and the groove portion,
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is formed on the substrate with an optically transparent material having a refractive index different from that of the substrate. The land portion, or the land portion and the groove portion,
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is formed on the substrate with an optically transparent material having a birefringence different from the substrate. 2. 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. 2. The magneto-optical recording medium according to claim 1, wherein the refractive index of the dielectric layer on the land portion is different from that of the dielectric layer on the groove portion.

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