JPH03273543A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium having high recording sensitivity, reproducing C/N and excellent long-term stability by using a Ge- contg. Al alloy having high reflectance and small thermal conductivity to constitute a reflecting layer. CONSTITUTION:The magneto-optical recording medium consists of a transparent substrate 1 having pregrooves, and an interference layer 2, recording layer 3 and reflecting layer 4 successively formed on the substrate. The reflecting layer consists of a Ge-contg. Al alloy. The amt. of Ge is preferably 0.1-30 at.%, and more preferably, 1-20 at.%. By using such an Al alloy containing Ge as the reflecting layer 4, the obtd. magneto-optical medium has high recording sensitivity, high carrier level, and excellent long-term stability.

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.

[Conventional technology]

Magneto-optical disks use laser light to record, reproduce, and erase information, so they have a large storage capacity.

Moreover, since a magnetic material is used for the recording film, rewriting is possible. Also, you can record and play back without contact, J! ! It also has excellent stability because it is not affected by dust.

The materials used for this magneto-optical recording layer (hereinafter referred to as recording layer) include TbFeCo, NdDyFeCo, and TbDyFe.
Rare earth-transition metal (RE-D) amorphous alloys such as Co are known, and these amorphous alloys have no grain boundary noise and can be easily formed into perpendicularly magnetized films by sputtering or the like. It is actively being developed because of its
Some of them are currently at the commercialization stage.

As a structure for this magneto-optical recording medium, a method has been proposed in which the recording layer is made thin to 200 to 300 layers and a reflective layer is provided on top of it in order to improve the recording and reproducing efficiency of laser light (Japanese Patent Publication No. 62 -27458, etc.). In this case, it is desirable that the reflective layer has a high reflectance, and examples of such a constituent material include metals such as Al, Ag, Au, and Cu. The above method is superior in that it can utilize both the Kerr effect and the Faraday effect, and therefore can provide a large C/N and jitter margin.

[Problem to be solved by the invention]

However, the above conventional technology has the following problems.

When a material with high reflectivity for laser light, which is the recording/reproducing light, is used as the material for the reflective layer, such as Au=Ag, Al, Cu, etc., the C/N, especially the carrier level, increases. For materials with high thermal conductivity, such as Ag and Cu, the heat from laser light irradiation is diffused in the reflective layer during recording, resulting in a significant decrease in recording sensitivity compared to a medium configured without a reflective layer. It has drawbacks such as: For this reason, among the above-mentioned materials with high reflectivity, Al, which has a relatively low thermal conductivity, is currently generally used. However, considering the recording laser power required to increase the speed of magneto-optical recording media, the liver reflection layer cannot be said to be sufficient in terms of sensitivity, and in the case of the A2 reflection layer, under high temperature and high humidity environmental conditions, it cannot be said that the liver reflection layer has sufficient sensitivity due to oxidation. The reflectance changes,
There are drawbacks such as a decrease in C and an increase in error rate due to the occurrence of pitting corrosion.

The present invention has been made to solve the problems of the prior art as described above, and provides a reflective layer type magneto-optical recording medium that has high recording sensitivity and reproduction C/N and has excellent stability over time. The purpose is to

[Means and effects for solving the problem] As a result of extensive studies to achieve the above object, the inventors have developed a reflective layer using Ge.
The present inventors have discovered that a magneto-optical recording medium with high recording sensitivity, high carrier level, and excellent stability over time can be obtained by comprising a liver alloy containing .

That is, according to the present invention, in a magneto-optical recording medium in which at least an interference layer, a magneto-optical recording layer and a reflective layer are sequentially laminated on a transparent substrate, the reflective layer is made of a base metal thin film containing Ge. A magneto-optical recording medium is provided.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is a sectional view showing an example of the configuration of a reflective layer type magneto-optical recording medium according to the present invention. This medium consists of a transparent substrate 1 with a pregroup, an interference layer 2, a recording layer 3 and a reflective layer 4.
It is constructed by sequentially laminating layers.

A structural feature of the magneto-optical recording medium of the present invention is that the reflective layer 4 is made of a static alloy containing Ge.

To explain the materials constituting the magneto-optical recording medium of the present invention and the necessary characteristics of each layer, first, the transparent substrate 1 is made of polycarbonate (PC), polymethyl methacrylate (
PMHA), a plastic substrate made of resin such as amorphous polyolefin (APO), or aluminosilicate,
Examples include substrates in which grooved resin is formed on glass such as barium borosilicate. These substrates are disk-shaped and have a thickness of about 1 to 2 mm.

As the recording layer 3, TbFeCo, NdDyFeCo,
DingbDyFec.

Amorphous alloy thin film of rare earth metal and transition metal such as BaF
e, , 0□, , CoFe, O, , (Bi, Y), F
oxide thin film such as e50□2, MnB1. Examples include polycrystalline alloy thin films such as CoPt, and all of these have an axis of easy magnetization in a direction perpendicular to the film surface. In the case of an alloy thin film, the film thickness is 100 to 1000, preferably 200 to 400.
It is Å. In the case of oxide thin films, there are no particular restrictions on the film thickness, as most have high transparency for recording and reproducing light;
A value of 0 to 5000λ is appropriate. Further, the recording layer 3 is not limited to a single layer film, but may be a multilayer film.

The interference layer 3 is provided between the substrate 1 and the recording layer 3.

The interference layer 3 uses a transparent film with a high refractive index (1.8 or more) to enhance the magneto-optic effect by the interference effect of light, and reduce noise by lowering the reflectance, and improves C/N. It is established for the purpose of improving the Furthermore, when the recording layer 3 is composed of an amorphous alloy thin film made of rare earth metals and transition metals, it must also have the function of preventing corrosion such as oxidation. That is,
It is necessary to prevent moisture and oxygen from entering the air or from the substrate 1, have high corrosion resistance, and have low reactivity with recording Fr13.A specific material is 5iO1Si.
O2, Al203. Metal oxides such as Ta2O, 84C
, inorganic carbides such as SiC, and metal sulfides such as ZrS.

These materials may be used in combination (for example, 5iA
1ON, 5iZrN, etc.), and is not limited to a single layer film, but may be a multilayer film. The optimum film thickness varies depending on the refractive index, but is usually 300 to 1500 Å, preferably 800 to 13
00 Å.

The reflective layer 4 is a feature of the present invention, and as described above, a static alloy containing Ge is used as a constituent material.

The content of Ge is preferably 0.1 to 30 atomic%, particularly preferably 1 to 20 atomic%. G of the present invention
The base total reflection layer 4 containing e has a reflectance of 70-90% for recording/reproducing light (wavelength: 830 nm) and a thermal conductivity of 0.
．． 3 to 0.5 caQ/cvsec・'C, so the apparent Kerr rotation angle is increased to increase the reproduction signal, and at the same time, the diffusion of heat due to laser light irradiation during recording is reduced to improve recording sensitivity. act.

This Al alloy may further contain small amounts of other elements (Cu, Mn, Mg, etc.) to improve corrosion resistance and the like.

The thickness of the reflective layer 4 is preferably 200 to 1000A, and 30A to 1000A is preferable.
Particularly preferred is 0-800 Å. If the film thickness is too thin, the C/N will decrease, and if it is too thick, the recording sensitivity will decrease.

As means for forming the interference layer 2, the recording layer 3, and the reflective layer 4 on the substrate 1, physical vapor deposition methods such as sputtering and ion blasting, chemical vapor deposition methods such as plasma CVD, etc. are used. In addition to the layer structure shown in Figure 1,
A second interference layer 5 may be further provided between the recording layer 3 and the reflective layer 4 (FIG. 2), a protective layer may be provided on the reflective layer 4,
Furthermore, the effects of the present invention are not impaired even in the case of a double-sided recording type structure in which the film surfaces are bonded together with an adhesive.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to the embodiments illustrated herein.

(Example) A polycarbonate substrate with a pre-group having a diameter of 130+wm and a thickness of 1 or 2 mm was set in a vacuum chamber of a sputtering apparatus, and the vacuum chamber was evacuated to 5×10 −' Torr or less. Next, a mixed gas of Ar and N2 was introduced into the vacuum chamber, the pressure was adjusted to 5 x 10-' Torr, and S
Discharge power 2kW (4w/cm") with i as target
Using high frequency sputtering, 1000 SiN films were deposited on the substrate as an interference layer. Next, a ThxzDyxzFegsCO* alloy (the suffix indicates the composition (
atomic%)) was similarly sputtered using TbDyFeC as a target.

250 membranes were installed. Furthermore, a reflective layer having a thickness of 500 Å was formed by sputtering an Al metal having Ge chips arranged thereon, and a recording medium of the example was obtained. Note that the amount of Ge in the reflective layer is determined by changing the number of Al chips on the Ni target.
I did i5.

(Comparative Examples 1 and 2) The recording layer was formed in the same manner as in the above example, and a 400 mm film and a Ge film were formed as a reflective layer by sputtering on the recording layer of Comparative Examples 1 and 2, respectively. And so.

The C/N and recording sensitivity of each recording medium produced as described above were measured. The results are shown in FIG.

The recording sensitivity was determined as the recording power at which the second-order distortion was minimized. Note that the recording and reproducing conditions were as follows.

Recording conditions: CAV 1800 rpm, recording position with a radius of 30 mm.

Recording frequency 3.7MHz Playback conditions: CAV 1800rpm, playback power 1m
W Figure 3 shows that the recording sensitivity improves as the Ge content in the alloy increases, while the C/N tends to gradually decrease as the Ge content increases. 30
It can be seen that it does not decrease much up to atomic%. In other words, it was confirmed that the recording sensitivity was improved without decreasing the C/N when the Ge content in the liver alloy reached 30 atomic gourd. Further, a double-sided recording type recording medium was prepared by bonding the film surfaces of two media of the example together using an adhesive, and an environmental test was conducted on the recording medium under conditions of 80° C. and 85% RH. As a result, this recording medium has 2
Even after 1,000 hours, there was no change in the pit error rate compared to the initial period, and it was found that the stability over time was also excellent.

〔Effect of the invention〕

As explained in detail above, according to the present invention, since the reflective layer is constructed using a Ge-containing Al alloy that has high reflectance and low thermal conductivity, recording sensitivity and reproduction C/N are high. Moreover, it becomes possible to provide a magneto-optical recording medium with excellent stability over time.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the layer structure of the magneto-optical recording medium according to the present invention, FIG. 2 is a cross-sectional view showing another example of the layer structure of the magneto-optical recording medium according to the present invention, and FIG. It is a graph showing measurement results of recording sensitivity. 1...Substrate 2,5...Interference layer 3...Magneto-optical recording layer 4...Reflection layer

Claims (1)

[Claims] (1) A magneto-optical recording medium in which at least an interference layer, a magneto-optical recording layer and a reflective layer are sequentially laminated on a transparent substrate, wherein the reflective layer is made of an Al alloy thin film containing Ge. magnetic recording medium.