JPH0883445A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE: To improve the CNR of a reproduced signal by reducing crosstalk due to recording domain of adjacent land (or groove). CONSTITUTION: This recording medium is a magneto-optical recording medium of a land/groove recording system in which the width of the domain D of a signal to be recorded in a land L is set to be shorter than the width of the land L. Moreover, the width of the domain D of a signal to be recorded in a groove G is set to be shorter than the width of the groove G.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a land / groove recording type magneto-optical recording medium which achieves a high recording density by recording an information signal on both a land and a groove.

[0002]

2. Description of the Related Art Magneto-optical recording media have been attracting attention as rewritable recording media with large storage capacity and high reliability, and they have been put to practical use in many fields including computer memory and have begun to spread. There is. However, with the increase in the amount of information and downsizing of equipment,
There is a demand for higher density recording / reproducing technology.

The high-density recording / reproducing technique is composed of a device-side technique and a medium-side technique. As the former technique,
There are optical super-resolution methods for obtaining a focused spot that exceeds the diffraction limit of laser light, and shortening of laser light wavelength. As the latter technique, the reproduction resolution is improved by the magnetic multilayer film, the pitch of the medium is narrowed, or the track density is improved by recording and reproducing on both the land and the groove (Iwanaga, Homma: “ High density magneto-optical disk using both land and groove areas ";OPTRONICS;No5; 199
4; pp. 117-121) and other technologies.

[0004]

DISCLOSURE OF THE INVENTION In the technology for improving the track density by the land / groove recording system, the existing land recording technology and the existing groove recording technology are used by using the existing optical system. If they are used as they are, the recording domains adjacent to each other in the direction orthogonal to the track exist at a distance exceeding the diffraction limit of the laser light, and therefore interference (crosstalk) due to the adjacent domains during reproduction is caused. Occurred, CNR (Carrier to Noise R
There is a problem that the audio is reduced. An object of the present invention is to improve the CNR of a reproduced signal by reducing the crosstalk.

[0005]

According to the present invention, as shown in FIG. 1, a signal recorded in a land L has a width of a domain D set to be equal to or less than a width of a land L and a signal recorded in a group G. Is a magneto-optical recording medium in which the width of the domain D is set to be equal to or smaller than the width of the group G. The present invention is also a magneto-optical recording medium in which the width of the recording domain D is larger than a value obtained by multiplying the effective laser spot diameter effectively involved in recording / reproduction of an information signal by 0.85. . Further, the present invention is, as shown in FIG. 3, a magneto-optical recording medium in which the sum of the width of the groove G and the width of the land L is smaller than the interval (pitch) of the groove G. Further, the present invention is a magneto-optical recording medium comprising a reflective layer 5 having a good thermal conductivity, which is formed on the opposite side of the substrate 1 with the magnetic layer 3 interposed therebetween, as shown in FIG.

[0006]

As shown in FIG. 1, the width of the domain D of the signal recorded on the land L is less than or equal to the width of the land L, and the groove G
If the width of the domain D of the signal to be recorded is set to be equal to or smaller than the width of the groove G, the crosstalk from the recording domain D of the adjacent groove G (or land L) is reduced during reproduction. Further, when the width of the recording domain is set to be larger than the value obtained by multiplying the effective laser spot diameter by 0.85, the adjacent groove G (or land L) is formed.
Crosstalk from the recording domain D is reduced. Further, as shown in FIG. 3, the sum of the width of the groove G and the width of the land L is set smaller than the pitch of the groove G (= track pitch), and the width of the land L = the width of the recording domain D or the width of the groove G. = When the width of the recording domain D is set,
The width of the recording domain D becomes stable regardless of the fluctuation of the laser power. Further, as shown in FIG. 4, when the reflective layer 5 having good thermal conductivity is provided, the high temperature region due to the laser spot at the time of recording becomes small, and as a result, the recording domain D becomes small.

[0007]

Embodiments of the present invention will be described below. Figure 1
This is an embodiment corresponding to claim 1, and the land L formed in a spiral shape on the disk substrate 1 made of polycarbonate.
The widths of the groove G and the groove G are set to 0.8 μm. Further, the width of the recording domain D is recorded narrower than the width of the conventional recording domain d shown in FIG.

When the CNR of the reproduced signal is measured for each of the recording domain D of FIG. 1 and the recording domain d of FIG. 2, the CNR when reproducing the recording domain D of FIG. About 3 than the CNR when replayed
It was good in dB. The reason is that there is an area having no recording domain between the domain D recorded in the land L and the domain D recorded in the groove G adjacent to the land L, which causes the crosstalk. It is considered that this is due to the reduction of

Further, when "effective laser spot diameter × 0.85 <recording domain width" is set as in claim 2,
The crosstalk can be suppressed to -20 dB or less.

FIG. 7 shows theoretical values of land width dependence of crosstalk with respect to effective laser spot diameter. When the laser spot diameter was 1.2 μm and the width of the land L was 0.8 μm, it actually agreed with the theoretical value shown in FIG. Therefore, it is very effective in designing the recording / reproducing characteristics of the disc. Further, it can be seen that if the land width (or groove width) is the same, crosstalk can be reduced by reducing the effective laser spot diameter.

FIG. 3 shows an embodiment corresponding to claim 3, in which the widths of the land L0 and the groove G0 spirally formed on the polycarbonate disk substrate 10 are set to 0.6 μm, respectively. In addition, the boundary between the land L0 and the groove G0 is an inclined region 11 that is neither a land nor a groove. The groove pitch (= land pitch = track pitch) is 1.6 μm, which is larger than 1.2 μm, which is the sum of the widths of the land L0 and the groove G0. In the disc of FIG. 3, when an information signal was recorded on the land L0 and the groove G0 and each recording domain was observed with a polarization microscope, it was confirmed that a uniform domain d having a width of 0.6 μm was formed on each. did it.

FIG. 5 shows an embodiment corresponding to claim 4, in which a transparent substrate 1 made of polycarbonate is provided on the transparent substrate 1.
In order from the side, a high refractive index layer 2 made of SiN having a thickness of 1100 Å, a reproducing layer 30 made of GdDyFeCo having a thickness of 300 Å,
Antioxidation layer 4 made of SiN with a thickness of 500Å, thickness of 500Å
The Al reflective layer 50 and the protective layer 6 made of an ultraviolet curable resin having a thickness of about 20 μm are formed. In addition, this structure is
It can be manufactured using a conventionally known sputtering method or the like.

FIG. 8 shows the magneto-optical recording medium of FIG. 5 and the conventional magneto-optical recording medium (the magneto-optical recording medium of FIG. 6;
In FIG. 5, there is no reflective layer 50 and the thickness of the magnetic layer 31 is 800Å
CRO of each crosstalk
The results of measurement (normalized by the CNR of the signal of the part to which the focus is applied) are shown. Here, in each magneto-optical recording medium, the track pitch is 1.6 μm, the width of the land L is 0.8 μm, and the width of the groove G is 0.8 μm.
That is, it is similar to FIG.

As can be seen from FIG. 8, the crosstalk is sufficiently reduced in the area where the recording power is high. this is,
Due to the thermal diffusion in the reflective layer 50 made of Al, it is possible to read the data during recording.
This is because the area of high temperature at the spot becomes smaller, and as a result, the recording domain D becomes smaller.

[0015]

According to the present invention, since the width of the domain recorded on the land and the groove is set to be equal to or smaller than the land width or the domain width, crosstalk from the recording domain of the adjacent groove (or land) is reduced. As a result, the CNR of the reproduction signal becomes good. Further, in the present invention, as a result of “effective laser spot diameter × 0.85 <recording domain width”,
Crosstalk is sufficiently reduced and the CNR of the reproduced signal becomes good. Further, in the present invention, since there is a region which is neither a land nor a groove between the land and the groove, and the information signal is recorded only in the land and the groove, it is possible to record a domain having a uniform recording domain width. Further, in the present invention, since the high temperature region is reduced by the reflective layer having good thermal conductivity, the recording domain D is reduced, crosstalk from the recording domains of the adjacent grooves (or lands) is reduced, and the reproduced signal is reduced. CNR becomes good.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a magneto-optical recording medium of the present invention.

FIG. 2 is a schematic diagram showing a conventional magneto-optical recording medium.

FIG. 3 is a schematic diagram showing a magneto-optical recording medium of the present invention.

FIG. 4 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of the present invention.

FIG. 5 is a schematic diagram showing a cross-sectional structure of a magneto-optical recording medium of an example.

FIG. 6 is a schematic diagram showing a cross-sectional structure of a conventional magneto-optical recording medium.

FIG. 7 is a graph showing theoretical values of land width dependence of crosstalk with respect to effective laser spot diameter.

8 is a graph showing the CNR measurement results of crosstalk between the magneto-optical recording medium of FIG. 5 and the magneto-optical recording medium of FIG.

[Explanation of symbols]

 5,50 Reflective layer G Groove L Land

Claims (4)

[Claims] 1. A magneto-optical recording medium in which an information signal is recorded both in a guide groove (groove) and between guide grooves (land), wherein the domain width of the signal recorded in the groove is the groove. A magneto-optical recording medium having a width less than or equal to the domain width of a signal recorded on the land. 2. The magneto-optical recording medium according to claim 1, wherein the recording domain width is larger than a value obtained by multiplying 0.85 by an effective laser spot diameter that is effectively involved in recording and reproduction of an information signal. 3. The magneto-optical recording medium according to claim 2, wherein a sum of the groove width and the land width is smaller than an interval between the grooves. 4. The magneto-optical recording medium according to claim 3, wherein a reflective layer having good thermal conductivity is formed on the side opposite to the substrate with the magnetic layer interposed therebetween.