JPS61211852A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To simply device constitution and to improve recording, reproducing and erasing performance by providing a disk-shaped supporting substrate, protective layer formed thereon, photomagnetic recording layer formed on the photomagnetic recording layer and changing the film thickness of the reflection layer in the radial direction of a photomagnetic recording medium. CONSTITUTION:The protective layer 2 is formed on the supporting substrate 1 and the photomagnetic recording layer 3 is formed on the protective layer 2; further the reflection layer 4 is formed on the layer 3. An org. resin material such as polycarbonate or epoxy or glass is used for the substrate 1. A material which prevents the penetration of water from the substrate side and obviates absorption at the laser wavelength used is used for the protective layer 2. Oxides such as SiO2 and ZrO2, nitrides such as AlN and Si3N4, sulfides such as SnS and Sb2S3, fluorides such as ThF4 and PbF2 and semiconductors of Si and Ge are used for said layer. Al, Ti, etc. are used for the reflection layer 4. The layer 4 is formed by changing the film thickness from the inside toward outside circumference of the medium so that the film thickness is made smaller nearer the outside circumference.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magneto-optical recording medium that records, reproduces and erases information using laser light.

(Prior art and its problems) Optical disk memory is considered as a new memory to replace existing magnetic disk memory because it requires high density, large capacity, and high speed access. Among these, magneto-optical disks using a magneto-optical recording medium have attracted the most attention because of their rewritability, and have been actively researched and developed in recent years. The configuration of a conventionally known magneto-optical recording medium uses glass or organic resin as the support substrate 1, as shown in FIG. A magneto-optical recording layer 3 made of an i-based film is formed. Light W% RI'i
ll ToL, Tehaλ4nBi, MrlCuBi.

MnTiB1. Amorphous magnetic thin films obtained as crystalline magnetic auxiliary films such as Mn, IGe, and PtCo, or alloys with transitional metals such as rare earths such as Gd, Tb, Dy, and Ho, Co, and Ni are known. .

Further, as shown in FIG.
A media configuration is also known in which grooves 11 of 1.6 to 2.5 μm with a period of ~100080 are formed concentrically or in a thinly wound shape, and a magneto-optical recording layer 3 is formed on the support substrate 1. The groove 11 formed here is used for tracking access of a laser condensed beam used for recording, reproducing, or erasing information on a recording medium.

In addition, the 8th type of conventionally known magneto-optical recording medium
As shown in the figure, a reflective layer 4 is formed on the magneto-optical recording layer 3 on the retaining layer 2, and the reflected light 21 from the surface of the magneto-optical recording layer 3 of the laser beam 20 incident from the substrate side and the magneto-optic There is one in which the magneto-optic effect of the magneto-optical recording layer 3 is increased by utilizing the reflected light 22 that passes through the recording layer 3 and is reflected by the reflective layer 4. Also in the W body of this structure 1, as shown in FIG. 9, a supporting substrate 1 having concentric or thinly wound grooves 11 as shown in FIG.
Media using . However, in the conventionally known magneto-optical recording medium described above, the magneto-optical layer 3 and the reflective layer 4 are formed so that their thicknesses are constant in the radial direction. Recording information by rotating the medium at angular velocity, F4. When editing or deleting,
There was a drawback that the recording power, reproducing power, and erasing power had to be changed depending on the radius of one row. (If you follow, Youkubo et al.
84, -39) This is because the optimum recording power, optimum reproduction power, and optimum erasing power of a medium with a constant film thickness are largely dependent on the linear velocity of the medium.

(Objective of the Invention) The object of the present invention is to solve the drawbacks of the conventional magneto-optical recording medium mentioned above, and to achieve a constant optimum recording power in the radial direction without depending on the linear velocity, by using a simple medium configuration. The object of the present invention is to provide a new magneto-optical recording medium that has read power, optimum erase power, and good recording/reproducing/erasing performance.

(Structure of the Invention) According to the present invention, in a magneto-optical recording medium in which information is recorded, reproduced and erased using a laser, a disc-shaped support substrate, a protective layer formed on the support substrate, and a corruption prevention layer are provided. An optical recording medium comprising a magneto-optical recording layer formed on the magneto-optical recording medium and a reflective layer formed on the magneto-optical recording I stage, the thickness of the reflective layer changing in the radial direction of the magneto-optical recording medium. A magnetic recording medium is obtained.

(Detailed Description of Configuration) The present invention solves the problems of the prior art by adopting the above-described configuration. Hereinafter, details of the present invention will be explained using the drawings. FIG. 1 is a sectional view showing an example of a magneto-optical recording medium according to the present invention.

A protective layer 2 is formed on a support substrate 1, a magneto-optical recording layer 3 is further formed on the self-protective layer 2, and a reflective layer 4 is further formed on the magneto-optical recording layer 3. . The supporting substrate 1 is made of an organic resin material such as methyl methacrylate, phosphoric carbonate, or epoxy, or glass, and a type in which grooves 11 for laser beam tracking are preformed as shown in FIG. 2 is also used.

The protective layer 2 may be made of a material that prevents moisture from penetrating from the platen side and does not absorb at the laser wavelength used, such as Sio, Siot, CeO, ZrO, etc.

TtO= , B+t O-, VVO-, 8nO-, sb
,olAl,o,,MgO,'rho,,Lag o,
,Into,.

Oxides such as Nd, O, etc., A, I N, S IB
Nitride such as N4, ZnS, Sb, S,, CdS
Sulfides ThF, λ4gFt, LaF, etc.
NdFs, CeF-.

Fluorides such as P b F , and semiconductors such as Si and Ge are used. As the magneto-optical recording layer 3, Gd
.

Rare earth metals such as 'rb, Dy, no, Fe, Co
.

An amorphous abrasive thin film made of an alloy with a transition metal such as Ni is used. For example, GdCo.

GdTbCo, GdTbFeCo, TbFe, TbFe
Co.

TbDyFeCo, GdTbFe, GdTbDyFe
.

There are TbCo, TbDyCo, and TbFeNi.

The reflective layer 4 includes AI, Cu, Ti, Ag, and A.
Metals such as u and Pt are used. The reflective layer 4 is formed with a thickness that changes from the inner circumference to the outer circumference of the medium, with the thickness becoming thinner at the outer circumference. This is a feature of the magneto-optical recording medium according to the present invention.

The protection M2, the magneto-optical recording layer 3, and the reflective layer 4 are formed by a film forming method such as a vacuum evaporation method or a sputtering method. In order to form the reflective layer 4 so that its thickness becomes thinner toward the outer periphery, a deposition source or a sputter source 6 is provided at a position eccentric to the center of rotation of the disk 5, as shown in FIG. using equipment. 9 is an exhaust system, and 10 is an introduced gas. By forming and depositing the film while rotating the disk 5 by the motor 8, a magneto-optical recording medium having a desired film thickness distribution in the radial direction can be easily obtained. Figure 4 (a) (b) (C)
are diagrams showing the relationship between the optimum recording power, the optimum reproduction power, the optimum erasing power and the linear velocity of the magneto-optical recording medium, respectively. The thickness of the reflective layer 4 of the medium with the configuration shown in FIGS. 1 and 2 is taken as a parameter. The optimum recording power mentioned here is the recording power that allows recording bits to be formed most faithfully to the recording signal.

Further, the optimum reproduction power refers to the reproduction power at which the C/N of the reproduction signal, that is, the ratio between the reproduction signal level and the noise signal level is the largest. Furthermore, the optimum erasing power refers to the erasing power that can completely erase optimally recorded bits. The optimum recording power, optimum reproduction power, and optimum erasing power all shift toward higher powers as the linear velocity increases. Furthermore, as the thickness of the reflective layer increases, the optimum power increases even at the same linear velocity. Conversely, in order to keep the optimum power constant with respect to linear velocity, it is necessary to change the thickness of the reflective layer.

If the thickness of the reflective layer is uniform in the radial direction, the optimum recording power, reproducing power, and erasing power must be changed depending on the radial position, as shown in FIG. If the film thickness of the reflective layer is varied in the radial direction as shown in FIG. It can be kept constant.

(Example) A polymethyl methacrylate substrate (
8i, N on 120 mm diameter, thickness l, 2 mm).

A protective film consisting of G d T b F e Il@j,
A reflective film of Cu was sequentially formed by sputtering without breaking the vacuum while rotating the disk. Si, N,
For film formation, a reactive sputtering method using Sj as a target and a mixed gas of Ar and N was adopted. Film thickness is 7
00A and was adjusted using a shield plate placed between the disk and the target so that it was uniform in the radial direction.

The G d T b Fe film was created by a sputtering method using a composite target consisting of Gd, Tb, and Fe. The film thickness is 500A0, 8 to make it uniform in the radial direction. , adjusted with a shield plate like N4.

The Cu reflective film was formed by sputtering to have a thickness of 1500 A0 with a radius of 29 mm and a thickness of 50 OA□) with a radius of 58 rrfn. Here, the disk was eccentrically rotated with respect to the Cu sputtering source.

Next, information was recorded, reproduced, and erased using the prepared magneto-optical recording medium. Rotate the medium at 30 revolutions per second,
Recorded, played back, and erased.

In the radius from 29 mm to 53 mm, the optimal recording power, reproducing power, and erasing power were all constant, and good recording, reproducing, and erasing were possible.

(Effects of Mineaki) As described above, the present invention has the following effects compared to the conventional example.

■ When used with constant angular velocity rotation, the media is designed so that the optimum recording power, optimum reproduction power, and optimum erasing power are constant in the radial direction of the magneto-optical recording medium. There is no need to change each power depending on the situation, and the device configuration can be simplified.

(2) By making the disk rotation center eccentric with respect to the position of the evaporation source or sputtering source, it is possible to easily create a medium with a desired film thickness distribution in the radial direction.

(2) The present invention is applicable to all magneto-optical recording media used for constant angular velocity rotation. That is, not limited to the embodiments of the present invention,
It can be applied to magneto-optical recording media with various film configurations using various protective layer materials, magneto-optical recording materials, and reflective layer materials.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing an example of the structure of a magneto-optical recording medium according to the present invention, and FIG. Figure 4 (a
)(b)(C) are diagrams showing the relationship between the optimum recording power, optimum reproduction power, optimum erasing power and linear velocity of the magneto-optical recording medium, and FIG. 5 shows the reflective layer of the magneto-optical recording medium according to the present invention. Figures 6, 7, and 8 showing the radial film thickness distribution of
9 and 9 are cross-sectional views showing the structure of a conventional magneto-optical recording medium. In the figure 1... Support substrate, 2... Protective layer, 3... Magneto-optical recording layer, 4... Reflective layer, 5... Disc, 6...
・・Vapor deposition source or sputter source, 7・°・Vacuum chamber,
8...Motor, 9...Exhaust system, 10...Introduced gas, 11...Groove, 20.21.22...Laser light. Multi 1 Figure 1: Tsubo Raki base handling 2: Ho 4 layer 3: Ge C ru vent air ↓ Otsu j 1F layer 4: Anti 1 1: Houki Aoi 2: Ho yakuman J: Opto-magnetic 3C weight layer 4: And Nephew Gi layer ll: Mizohan 4 Mouthless 5 Figure te° ≧ Sukuhan wo 3: Nine certainty:! , l Roku layer 7 Figure 3: Daikamaki ↓ Koroku shield ll: Teitei 8 Painting I: Onna Seki 2: Hoj layer 3: Fugoki ↓ C record 4: Ogero layer 20, 21.22 : L, - the light 1 : tokutoku 11 anti 2 : f yoro layer 3 : to confirm shell ↓ Go rule 4 : β eaves tier I: groove

Claims (1)

[Claims] A magneto-optical recording medium in which information is recorded, read and erased using a laser, includes a disc-shaped support substrate, a protective layer formed on the support substrate, a magneto-optical recording layer formed on the protective layer, and the magneto-optical recording layer. and a reflective layer formed on the recording layer,
A magneto-optical recording medium, wherein the thickness of the reflective layer varies in the radial direction of the magneto-optical recording medium.