JPH0294146A - magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the warpage and deformation of the recording medium and to stably maintain reproducing characteristics over a long period of time by providing a cover layer which consists of the oxide or nitride of an inorg. material or the composite thereof for the substrate surface on the side opposite to a recording surface and the inside and outer peripheral ends of the recording medium. CONSTITUTION:A 1st protective layer (under coat) 2, a magneto-optical recording layer 3 and a 2nd protective layer (top coat) 4 are successively laminated on a light transparent substrate 1 and further, the cover layer 5 is formed to the surface of the medium on the side opposite to the recording surface and the end parts on the inner peripheral and outer peripheral sides (inner and outer peripheral surface parts) of the medium. The cover layer 5 is formed by a vapor deposition method and sputtering method using the oxide of the inorg. material, the nitride of the inorg. material or the composite of the oxide and nitride of the inorg. material. The warpage and deformation are prevented in this way even in the environment where the temp. and humidity change largely; in addition, the reproduction characteristics are stably maintained over a long period of time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a rewritable magneto-optical recording medium, and particularly to a magneto-optical recording medium that effectively prevents mechanical deformation and corrosion deterioration caused by moisture. It is.

[Conventional technology]

In recent years, magneto-optical recording media that utilize the magneto-optic effect have been actively researched and developed as rewritable optical recording media, and some have even been put into practical use.

This magneto-optical recording medium has the advantages of large-capacity, high-density recording, non-contact recording and playback, and ease of access, as well as the ability to overwrite document information files, video and still image files, and computer memory. It is expected that it will be used for

The above-mentioned magneto-optical recording medium has a perpendicular magnetization film, that is, a magnetic film having an axis of easy magnetization in a direction perpendicular to the film surface, as a recording layer, and can record, reproduce, and erase information by irradiating a laser beam and applying a magnetic field. It is supposed to be done.

The recording layer is made of an alloy of an amorphous heavy rare earth/light rare earth metal and a transition metal, such as Tb-Fe-Co, G
d-Tb-FeCo, Dy-Fe-Co, Dy-Tb
The use of materials such as -Fe-Co and Gd-Dy-Fe-Co has been proposed. These materials have the disadvantage that they are susceptible to corrosion due to oxidation, and their magnetic properties such as the coercive force and perpendicular magnetic anisotropy of recording (W) deteriorate over time. For this reason, a three-layer structure in which the recording layer is covered with a sand-inch protective film is often adopted as the structure of the recording medium.

On the other hand, as a substrate for a magneto-optical recording medium, a glass substrate with a pre-group, a polycarbonate (PC) substrate, etc. are used, and a polycarbonate substrate is particularly advantageous in practical use because it is inexpensive.

However, this polycarbonate substrate has high moisture permeability and oxygen permeability, and is susceptible to warping and deformation depending on the temperature and humidity during use. In particular, the influence of humidity is large, and when the outside air changes from a dry state to a humid state, warping occurs more frequently. Furthermore, the permeation of oxygen causes damage to the recording layer through pinholes in the protective film.

The mechanical deformation and corrosion deterioration described above cannot be said to be sufficient even if the recording polishing sand inch is covered with a protective layer.

On the other hand, Japanese Patent Application Laid-open No. 63-20745 discloses that by covering the resin substrate part in contact with the outside world with water-repellent resin or low moisture permeability resin, changes over time in C/N and pit error rate can be reduced. Techniques for reducing this have been disclosed.

[Problem to be solved by the invention]

However, the material used as the cover layer in the technology disclosed in the above publication is an organic material, and even if it is water repellent or has low moisture permeability, its protective effect cannot be said to be sufficient. It was hoped to improve the

The present invention solves the problems of the prior art, and provides a magneto-optical recording medium that can prevent warping and deformation even in environments where temperature and humidity change significantly, and that maintains stable playback characteristics over a long period of time. I'll refer to that as "I".

[Means to solve the problem]

In order to achieve the above object, the present invention provides a transparent resin substrate, a recording layer formed on the substrate and made of an amorphous magnetic alloy film, and a protective film covering both sides of the recording layer. In a magneto-optical recording medium comprising: an inorganic material made of oxide or nitride, or a composite thereof, on the substrate surface opposite to the recording surface of the recording medium and on the inner and outer peripheral edges of the recording medium; A magneto-optical recording medium is provided which is characterized by being provided with a cover layer.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of the configuration of a magneto-optical recording medium according to the present invention. This magneto-optical recording medium has a first protective layer M (undercoat) 2, a magneto-optical recording layer 3, and a second protective layer (top coat) 4 laminated in sequence on a transparent resin substrate 1, and the medium A cover layer 5 is formed on the surface opposite to the recording surface of the medium, and on the inner and outer edges (inner and outer circumferential side surfaces) of the medium.

The transparent resin substrate 1 is made of resin such as polycarbonate (PC), polymethyl methacrylate (PMMA), or epoxy.

The magneto-optical recording layer 3 contains at least one rare earth metal such as Tb, Gd, Dy, and Nd, and transition metals Fe and C.
.

An amorphous magnetic alloy is used in combination with at least one or more of the following. Examples of such alloys include TbFe
Co, GdTbFeCo, NdDyFeCo, TbD
yFeC.

etc. are exemplified. This magneto-optical recording layer 3 is formed to a thickness of 400 to 1000 layers by sputtering, vapor deposition, or the like.

The first and second protective layers 2 and 4 are SiN, 5iAQON
400 to 100 using vapor deposition method or sputtering method.
Formed to a film thickness of 0. Note that since the first protective layer 2 also serves as an enhancement film, the film thickness is set in accordance with its refractive index so that the magneto-optical effect of the appearance due to multiple reflections is as large as possible. In addition, the first protective layer 2 and the second protective layer 2
The protective layer 4 may be formed of the same material, or may be formed of a different material in consideration of each function.

The cover layer 5 is formed using an oxide of an inorganic material, a nitride of an inorganic material, or a composite of an oxide and a nitride of an inorganic material to a thickness of 100 to 3000 nm by vapor deposition or sputtering. Specific materials used to form the cover layer 5 are: ．． 5
i02・Au03, ZrO2, SnO2, engineering n2o3,
Examples include Nb2O5, Tie, Y2O3, AQN, GeN, etc. This cover layer 5 improves the moisture permeability and oxygen permeability of the recording medium, sufficiently prevents warping and deformation even in environments with large changes in temperature and humidity, and can maintain stable playback characteristics of the recording medium over a long period of time. shall be.

〔Example〕

The present invention will be further explained below with reference to Examples, but the present invention is not limited to these Examples.

(Example 1) Polycarbonate substrate (diameter approximately 130 m, thickness 1.2 m
n) was placed in a sputtering device, a SiN protective film (undercoat) was formed on the substrate by sputtering to a thickness of 800 mm, and Tb12Dy1□FeG1 was deposited on the substrate.
A 1 COIl magneto-optical recording layer was formed to a thickness of 800 nm, and a 5iiON protective film (top coat) was further formed to a thickness of 800 nm.

The disk thus obtained was placed in a sputtering apparatus using a sputtering apparatus 1 so that a cover layer could be formed on the side opposite to the recording surface of the disk. Then, the chamber of the sputtering device is evacuated until the vacuum level reaches IXIF7torr,
Water and occluded air in the polycarbonate substrate were dehydrated and degassed. Next, the mixed gas of Ar+02 was mixed with A':0
With a ratio of □=5:1, the inside of the chamber is 3×1O-3t, or
It was introduced so that r. Thereafter, a DC voltage was applied to the 5iAllkON target to cause discharge at a power of about IKW, and the discharge was continued until a film thickness of 1,000 layers was obtained to form a cover layer to obtain a recording medium having a single-plate structure.

On the other hand, a recording medium of a comparative example was obtained in the same manner as above except that a cover layer was not formed.

For the recording media (single disks) of Example 1 and Comparative Example produced as described above, the amount of warpage was first measured. The results are shown in FIG. The recording medium of the comparative example without the cover layer had warpage of 100 μm or more, and in some cases, the warpage reached 600 μm. However, according to the recording medium of Example 1, since the cover layer was provided, the warpage was reduced to about 10 μm. This is considered to be because the formation of the cover layer balanced the stress on both sides of the substrate.

Next, the amount of warpage and surface condition of the image recording medium were examined when the medium was continuously changed from a dry state of 70° C. and 20% Rh to a high humidity state of 70° C. and 80% R1+. As a result, the amount of warpage increased by about twice in the recording medium of Comparative Example, and remained unchanged in the recording medium of Example 1. Further, in the case of the recording medium of the comparative example, no cracks were observed because the amount of warpage was large.

As described above, the cover layer of Example 1 showed a 1-minute effect on the warpage of the medium.

Furthermore, the effect of the image recording medium on changes over time under high temperature and high humidity conditions of 80° C. and 85% RI+ was investigated.

Figure 3 shows the change in the amount of warpage over time. In the recording medium of the comparative example, the amount of warpage slightly increases after 500 hours and then decreases slightly.
There was an amount of warpage on the order of μm. On the other hand, in the recording medium of Example 1, the amount of warpage did not change and the magnitude was also 10
It was about μm.

As described above, in Example 1, a significant improvement in the long-term stability of mechanical properties was observed.

Next, the image recording medium was examined for changes in error rate over time under high temperature and high humidity conditions of 80° C. and 85% RH.

The results are shown in FIG. Note that the error rate in the figure is normalized to the initial value. In the recording medium of Example 1, 200
There was no change even after 0 hours had elapsed. However, in the recording medium of the comparative example, the error rate deteriorated by a factor of 10 after 500 hours = 8, and furthermore, the error rate deteriorated to such an extent that further measurements could not be performed due to the occurrence of cracks, etc.

As described above, the recording medium of Example 1 has an error rate (
A significant improvement was also observed in the long-term stability of regeneration properties.

(Example 2) In Example 1, a film thickness of 2000 S was used as the cover layer.
A recording medium was obtained in the same manner except that an iO film was formed.

(Example 3) In Example 1, the cover layer had a film thickness of 1000.
A recording medium was obtained in the same manner except that the ilQN film was formed.

(Example 4) In Example 1, 5iZrN was used as the undercoat layer.
was formed to a thickness of 700 mm, and on top of that, Tb1zDYx2
A magneto-optical recording layer of Feto Co6 was formed by 800 people, and a top coat layer of 5iZrN was formed thereon by 800 people. Furthermore, 5iZrN with a film thickness of 500 nm was used as a cover layer.
was formed to produce a recording medium.

Similar to Example 1, excellent effects could be obtained in the recording media of Examples 2 and 3 produced as described above.

In addition to -1], materials such as AQ203, Si
n, ・AQ203, ZrO7, SnO□, In2O,,
Using Nb2O6, Tie, y2o3, AQN and GeN, a recording medium with a cover layer formed with a thickness of 800 to 2000 layers was fabricated and its characteristics were evaluated. Whether it is an object or a composite thereof, the initial warpage of the medium, the amount of warpage and surface condition when continuously changed from dry to high temperature and high humidity, effects on changes over time under high temperature and high humidity, and errors. Regarding the rate change over time, the same or sufficient effect as in the above example was shown.

〔Effect of the invention〕

As described in detail above, according to the present invention, a cover layer made of an inorganic material oxide or nitride or a composite thereof is provided on the substrate surface opposite to the recording surface and on the inner and outer peripheral edges of the recording medium. Since this is provided, it becomes possible to sufficiently prevent warping and deformation of the recording medium even in an environment where the temperature and humidity change significantly, and it becomes possible to maintain stable playback characteristics over a long period of time. Therefore, it is possible to provide a highly reliable and high quality magneto-optical recording medium.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a magneto-optical recording medium according to the present invention, FIG. 2 is a diagram showing measurement results of the amount of warpage in recording media of an example of the present invention and a comparative example, and FIG. Figure 4 shows the change in the amount of warpage over time under high temperature and high humidity conditions in the recording media of the example and comparative example of the present invention. It is a figure showing a change over time. 1... Transparent resin substrate 2... First protective layer (undercoat) 3... Magneto-optical recording layer 4... Second protective layer (top coat) 5... Cover layer

Claims (1)

[Claims] (1) A magneto-optical recording medium comprising a translucent resin substrate, a recording layer made of an amorphous magnetic alloy film formed on the substrate, and a protective film covering both sides of the recording layer. A cover layer made of an oxide or nitride of an inorganic material or a composite thereof is provided on the substrate surface opposite to the recording surface of the recording medium and on the inner and outer peripheral edges of the recording medium. Magneto-optical recording medium.