JPS60231936A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a thoroughly high C/N ratio in the stage of reproducing and to prevent approximately thoroughly the oxidation corrosion of a magnetic layer by providing a dielectric layer having high refractive index on the conventional dielectric layer having low refractive index or high transparency. CONSTITUTION:The magnetic layer 2 having vertical magnetic anisotropy is provided on a substrate 1 and the dielectric layer 3 (the 1st dielectric layer) having 300-10,000Angstrom thickness and having low refractive index or high transparency is provided thereon; further the dielectric layer 3' (the 2nd dielectric layer) having 20-100Angstrom thickness and having high refractive index is provided thereon. The layer 3' having the high refractive index is provided on the conventional layer 3 having low refractive index or high transparency and therefore the C/N ratio in the stage of reproduction is improved by the improved repetitive interference effect of light. The oxidation corrosion of the magnetic layer is approximately thoroughly prevented by the protective effect of the novel dielectric layer and the generation of deterioration in performance is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a magneto-optical recording medium for recording and reproducing information using laser light.

BACKGROUND OF THE INVENTION In recent years, magneto-optical recording media, so-called magneto-optical disks, in which information is recorded and reproduced using laser light, have been actively researched as recording media suitable for high-density recording. The basic structure of such magneto-optical recording media is that a magnetic layer with perpendicular magnetic anisotropy, such as a rare earth metal to transition metal amorphous alloy film, is provided on a transparent substrate such as a glass plate. Reproduction is performed by utilizing the rapid change in magnetic properties of the magnetic layer when irradiated with laser light, and reproduction is performed using the magneto-optical effect (
This is done using the Kerr effect, Faraday effect, etc.).

Here, it is desirable that the C/N ratio during reproduction (proportional to the product of the square root of the light reflectance R and the magneto-optic rotation angle θ) is as large as possible, and for this reason, the material aspect of the magneto-optical recording medium is limited. Various proposals have been made from a structural standpoint as well.

For example, the Kerr effect enhancement type as shown in Figure 1 (in the figure, 1 is the substrate, 2 is the magnetic layer, 3 is the dielectric layer with low refractive index or high transparency), Figure 2 (in the figure, 2' is TbFe
(F is a magnetic layer with a large Kerr rotation angle such as GdFe. Reflective film structure types are known.

However, none of these proposed recording media can obtain a sufficient C/N ratio during reproduction, and even if there is a surface layer such as a dielectric layer on the magnetic layer, the performance deteriorates due to oxidation corrosion of the magnetic layer over time. was unavoidable.

Object The object of the present invention is to provide a magneto-optical recording medium which can obtain a sufficiently high C/N ratio during reproduction and can almost completely prevent oxidative corrosion of the magnetic layer.

Structure The magneto-optical recording medium of the present invention has a structure 5 shown in FIG.
A dielectric layer 3 with a low refractive index or high transparency of 0 to 10.00 OA (hereinafter referred to as the first dielectric layer) and a thickness of 2
A dielectric layer 3' (hereinafter referred to as a second dielectric layer) having a high refractive index of 0 to 100 A is provided.

As described above, the magneto-optical recording medium of the present invention belongs to the Kerr effect enhancement type, and by providing a dielectric layer with a high refraction $zv low i** on a conventional dielectric layer with a low refractive index or random brightness, it can be further improved. This is the Kerr effect, that is, the Kerr rotation angle θk is increased. In other words, in the conventional Kerr effect enhancement type magneto-optical recording medium, the light reflected by the magnetic layer is repeatedly interfered with by the dielectric layer.
However, in the case of the magneto-optical recording medium of the present invention, the light reflected by the magnetic layer is reflected even more than the conventional area by the second dielectric layer, and as a result, the light reflected by the magnetic layer and the second dielectric layer is The repeated interference effect of light with the body layer is further strengthened, and Ok is significantly increased. On the other hand, for this reason, the intensity of the reflected light returning to the light receiving element that detects the recorded information signal is reduced compared to the conventional one, but the decrease in reflectance R is
Since the increase in k exceeds this, the C/N ratio improves as a result.

Next, a method of forming a material layer used in the magneto-optical array of the present invention will be explained.

First, the substrate materials are generally quartz glass; GGG single crystal; sapphire; lithium tantalate: crystallized transparent glass; nogilex glass; single crystal silicon with or without oxidation treatment on the surface; kL@0@g A40
B・MgO, MgO・I, IF, Y, O,・Li
F, B @ OoZ r O@ ' Y! 011
* Transparent ceramic materials such as TbO@'Cao; inorganic materials such as inorganic silicon materials, or organic materials such as acrylic resins, polycarbonate resins, and polyester resins can be used.

The magnetic layer is a film having magnetic anisotropy, for example, TbF.

Rare earth metal to transition metal amorphous alloy films such as GdFs, TbFaCo, and GdTbFa, and MnCuB1. It is made of a polycrystalline film such as Ba ferrite. Generally, a vacuum evaporation method, a sputtering method, or an ion blating method is employed as a method for forming the magnetic layer. Thickness is 500~5.0
A range of 00 A is appropriate.

The first dielectric layer may be made of a dielectric material 1 having a low refractive index or high transparency, such as S i O! g S l O, T i
O! eT 10. Coo, I(f O! p B
ed, 'rho, IS 1B N4, etc. are used. The method for forming the third dielectric layer is the same as that for the magnetic layer. The appropriate thickness is 300 to 10, ooo A in order to cause Kerr effect enhancement due to repeated interference of light. If it is less than 3OOA, sufficient effect cannot be obtained,
Moreover, even if it exceeds 10,000 OOA, no further effect can be obtained.

The material of the second dielectric layer is a high refractive index dielectric, for example Lk.
i Amorphous silicon, amorphous germanium, etc. are used. The method for forming the second dielectric layer is the same as that for the magnetic layer, and plasma CVD can also be used. A suitable thickness is 20 to 100A. It is difficult to obtain a membrane of less than 20A, and if it exceeds 100 people, the transmittance decreases, which is not preferable.

Effects As described above, the magneto-optical recording medium of the present invention has a dielectric layer with a high refractive index on top of the conventional dielectric layer with a low refractive index or high transparency. C
/N ratio is improved, and due to the protective effect of this new dielectric layer, oxidation corrosion of the magnetic layer is almost completely prevented, and performance does not deteriorate.

Examples of the present invention are shown below.

Example: TbFe was vacuum deposited on a quartz glass plate to a thickness of 500 mm.
A magnetic layer A is formed, and then StO is vacuum-deposited on it to form a first dielectric layer with a thickness of 400A, and amorphous silicon is further deposited on top of it by plasma CVD to form a first dielectric layer with a thickness of 50A. Two dielectric layers were formed to create a magneto-optical recording medium.

On the other hand, for comparison, a magneto-optical recording medium was prepared in the same manner except that the second dielectric layer was not provided.

Next, these recording media are magnetized in one direction, and while applying a magnetic field of 500 oersted opposite to the direction of magnetization, a semiconductor laser beam with an output of 20 mW is applied to the recording medium surface at an intensity of 10 mW and a frequency of I Ml (z After irradiation and recording with a pulse of 0, the C/N ratio was similarly high at 48 dB for the product of the present invention, but was low at 42 dB for the comparative product.

Furthermore, when the above recording medium was stored in an atmosphere of 60°C and 90% R1 for 200 hours, and recording and playback were performed in the same manner, the C/N ratio of the inventive product was 45 dB, which was almost the same as before storage. On the other hand, the comparative product showed a significant decrease of 38 dB.

[Brief explanation of drawings]

1 to 3 are block diagrams of a conventional magneto-optical recording medium, and FIG. 4 is a block diagram of a magneto-optical recording medium of the present invention. 1...Transparent substrate 2...Magnetic layer l...Magnetic layer with high Curie point l...Magnetic layer with high Kerr rotation angle 3...Dielectric layer 3' with low refractive index or high transparency
...High refractive index dielectric layer 4...Metal reflective film: Sui (F, 1 person)

Claims (1)

[Claims] 1. A magnetic layer with perpendicular magnetic anisotropy on the substrate, a dielectric layer with a low refractive index or high transparency with a thickness of 300 to 10,000 A, and a high refractive layer with a thickness of 20 to 100 A on top of that. a magneto-optical recording medium provided with a dielectric layer of