JP2797384B2 - Method for manufacturing magneto-optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magneto-optical recording medium, and more particularly to a method for manufacturing a magneto-optical recording medium using a translucent resin substrate.

(Prior Art) Optical disks are being actively studied because a large amount of information can be recorded at a high density. As a recording medium for this optical disk, an amorphous perpendicular magnetization film made of a rare earth-transition metal is mainly used in view of the ease of preparation and high recording sensitivity. However, this amorphous magnetic film has a drawback that it tends to be oxidized, and its magnetic properties change when it is placed in a high-humidity environment. Here, if a resin substrate is used as the transparent substrate due to its price and resistance to cracking,
A small amount of water through the substrate may cause corrosion of the magnetic film. Therefore, as shown in FIG. 2, a recording layer 3 is usually sandwiched between protective films 2, 2 'on a transparent substrate 1 to prevent oxidation and corrosion of the magnetic film.

(Problem to be Solved by the Invention) Here, a film having a higher refractive index than the substrate is selected as the protective film 2 in order to increase the Kerr rotation angle and improve the performance of the recording and reproducing characteristics together with the protective effect. Further, the Kerr rotation angle is related to the thickness of the protective film, and a film thickness that maximizes the Kerr rotation angle is selected (500 ° to 1000 °). In consideration of the moisture resistance of the protective film, the thicker the film thickness, the more the protective effect on the recording film increases, but it cannot be made too thick due to the above-described effect of increasing the Kerr rotation angle and the difficulty in preparation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a protective film having a stable and excellent moisture-proof effect in a protective film having a film thickness that maximizes the Kerr rotation angle.

[Means for solving the problem]

The method for manufacturing a magneto-optical recording medium of the present invention is a method for manufacturing a magneto-optical recording medium by laminating a protective film, a magneto-optical recording layer, and a surface protective film on a light-transmitting resin substrate.
After forming an Nx-based (SiNx) protective film, a heating and humidifying treatment is performed in a high-temperature, high-humidity atmosphere to realize a protective film excellent in moisture proofing.

This protective film may be a protective film in which a SiN-based film is laminated on an SiO ₂ -based film, or a heating / humidifying treatment may be performed after forming a SiN-based protective film as a surface protective film. it can.

The heating temperature may be 45 ° C. or higher and within the allowable temperature of the translucent resin, and is preferably 60 ° C. The humidity is 60%
It is sufficient that it is not less than 100% and preferably not more than 90%.

(Function) When a high-temperature and high-humidity treatment was performed after forming a protective film on a resin substrate, it was observed that the film that had shown moisture permeability changed to moisture-proof. FIG. 3 shows a sectional structural view of the sample used in the experiment.
In the figure, 1 is a transparent resin substrate such as a polycarbonate (hereinafter, referred to as PC) substrate, and 2 is SiN of about 800 mm.
And the like. FIG. 4 shows a change in weight of the substrate when the substrate is left in an atmosphere in which environmental conditions are changed. The upper diagram of FIG. 4 shows values of temperature and relative humidity indicating environmental conditions. The figure below shows the change in weight of the substrate at that time. This change in weight indicates a change in the moisture content of the substrate during moisture absorption and dehumidification. At 60 ° C. and 90% RH for about 60 hours, a weight increase of 50 mg was observed. The weight increase rate is about 0.27%, which is close to the equilibrium moisture absorption rate (0.3%) of the PC board. The result is the protective film 2
Means moisture permeable. That is, although water enters the PC board from the part not covered with the protective film 2, the value is roughly estimated to be at most 0.05%, and the weight increase of 0.27% is caused by the moisture content through the protective film 2. Is big. Next, the substrate was blown at 60 ° C. N _{2 for} 3 hours and then blown at 20 ° C. N ₂ (<10%
RH) Even after drying for about 60 hours, the weight did not return to the original initial weight value indicated by A. Then 60 ℃ 90% RH
Although it was left for about 50 hours, no change in weight was observed as in the initial stage. FIG. 1 shows the relationship between the weight change rates based on the assumption of the above weight change and the environmental conditions of 60 ° C. and 90% RH.

In the case of only the PC board indicated by ○,
0.3%. □ indicates a sample with 2000 mm of Ti formed on both sides of the PC, and ● indicates a sample with 800 nm of SiN formed on both sides of the PC board. The weight change rate of the sample indicated by □ can be explained by the fact that water enters the PC substrate from the portion where the Ti film is not formed. As shown in Fig. 3, the protective film that showed moisture permeability as shown at the beginning shows the same moisture change rate as the square mark as shown in Fig. 3. Indicates that it has changed. Here, the value indicated by point B in FIG. 4 was adopted as the initial weight of the sample when calculating the weight change rate. This means that a reliable film can be formed even if a thin protective film optimally designed when increasing the apparent Kerr rotation angle for improving the recording / reproducing characteristics is used.

For comparison, a PC substrate and a substrate coated with a moisture permeable film on both sides of a PC substrate were placed in a 60% RH 90% RH for about 100 hours, and
After drying at 0 ° C N ₂ blast (<10% RH),
It has returned to its original weight in about 3 hours. This result is
Shown in the figure. From this and the result in FIG. 4, the point B in FIG.
The PC board is considered to be sufficiently dry.
It can be seen from the change in weight due to the increase in humidity that the protective film of the present invention certainly changed to moisture-proof.

First Embodiment Next, an embodiment of the present invention will be described with reference to the drawings. 5 (a) to 5 (d) show the steps of manufacturing a magneto-optical recording medium according to the present invention. Using a high-frequency sputtering device on a PC board 1 having a thickness of 1.2 mm, as shown in FIG.
A system protective film 2 is formed to a thickness of about 800. After that, it was left in an atmosphere of 60 ° C. and 90% RH for about 50 hours, dried, and used in a high-frequency sputtering device to form a TbFeCo layer 3 and a Si film as shown in FIG.
N-type protective films 2 'were formed to a thickness of about 800.degree. The magneto-optical recording medium produced by using this manufacturing method did not corrode even in the reliability test as compared with the conventional magneto-optical recording medium, and the reliability was improved.

Second Embodiment FIGS. 6 (a) to 6 (d) show a manufacturing method for explaining a second embodiment. In the second embodiment, the present invention is applied to a composite protective film instead of a single-layer protective film. 1.2m thick
The SiO ₂ protective film 4 and the SiN protective film 5 having small internal stress are applied to a PC substrate of about 80 m in total by using a high frequency sputtering apparatus.
0 ° formed. Thereafter, the substrate was left in an atmosphere of 60 ° C. and 90% RH for approximately 50 hours, and then dried. As shown in FIG. The recording medium was used. The magneto-optical recording medium produced by using this manufacturing method did not corrode even in the reliability test as compared with the conventional magneto-optical recording medium, and the reliability was improved.

Third Embodiment FIGS. 7A to 7C show a manufacturing method for explaining a third embodiment. As shown in (b), a PCN 1 having a thickness of 1.2 mm is coated with a SiN-based protective film using a high-frequency sputtering device.
The TbFeCo layer 3 is formed continuously by about 800 ° for 2,2 ′ and about 800 °. Thereafter, the substrate was allowed to stand in an atmosphere of 60 ° C. and 90% RH for about 50 hours and then dried to obtain a magneto-optical recording medium. The magneto-optical recording medium produced by using this manufacturing method did not corrode even in the reliability test as compared with the conventional magneto-optical recording medium, and the reliability was improved.

(Effect of the Invention) As described above, by using the manufacturing method of the present invention, a protective film having excellent moisture proofness can be obtained even with a thin protective film, and the life of the magneto-optical disk can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing the results of a moisture absorption experiment for explaining the present invention,
FIG. 2 is a cross-sectional view of the magneto-optical recording medium, FIG. 3 is a cross-sectional view of the sample used in the moisture absorption test, FIGS. 4 and 8 show the results of the moisture absorption test, and FIG. FIG. 6 is a sectional structural view showing a manufacturing method for explaining a first embodiment of the present invention, FIG. 6 is a sectional structural view showing a manufacturing method for explaining a second embodiment of the present invention, and FIG. FIG. 11 is a sectional structural view illustrating a manufacturing method for describing a third embodiment. In the figure, 1 is a transparent substrate, 2, 2 'are protective films, 3 is TbFeCo
The recording layers 4 and 5 are protective films.

Claims (5)

(57) [Claims] 1. A method for manufacturing a magneto-optical recording medium by laminating a protective film, a magneto-optical recording layer, and a surface protective film on a light-transmitting resin substrate, comprising the steps of: providing silicon nitride (SiNx) on the light-transmitting resin substrate; After forming a protective film of the film, the light-transmitting resin substrate on which the silicon nitride protective film is formed is at least 45 ° C. or more within the allowable temperature range of the light-transmitting resin substrate, and at least 60% or more of humidity. A method for producing a magneto-optical recording medium, comprising: performing a heating and humidifying treatment in an atmosphere; drying the film; and then forming the optical recording layer and the surface protective film. 2. A light-transmissive resin substrate on the protective film, a magneto-optical recording layer, the method by laminating a surface protective film to produce a magneto-optical recording medium, silicon oxide on the light-transmissive resin substrate (SiO ₂ A) forming a protective film in which a silicon nitride film is laminated on the film; and then forming the light-transmitting resin substrate having the protective film formed on the resin substrate from at least 45 ° C. to the allowable temperature of the light-transmitting resin substrate. A method for manufacturing a magneto-optical recording medium, comprising: performing a heating and humidifying treatment in an atmosphere having a humidity of 90% or more within a range, drying the magneto-optical recording layer and the surface protective film. 3. A method for manufacturing a magneto-optical recording medium by laminating a protective film, a magneto-optical recording layer, and a surface protective film on a light-transmitting resin substrate, comprising the steps of: protecting a silicon nitride film on the light-transmitting resin substrate; A film, a magneto-optical recording layer, a surface protection film of a silicon nitride film are formed, and the light-transmitting resin substrate formed up to the surface protection film is at least 45 ° C. or more within an allowable temperature range of the light-transmitting resin substrate, A method for producing a magneto-optical recording medium, comprising performing a heating and humidifying treatment in an atmosphere having a humidity of 60% or more and then drying. 4. The method for manufacturing a magneto-optical recording medium according to claim 1, wherein said protective film is a protective film in which a silicon nitride film is laminated on a silicon oxide film. 5. The method for manufacturing a magneto-optical recording medium according to claim 1, wherein the humidifying heat treatment is performed in an atmosphere of 60 ° C. and 90% humidity.