JPH09128830A - Magneto-optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance and productivity by forming recording media and protective films after discharging the moisture in substrates to the max. possible extent by heat treating these substrates at and for an adequate temp. and time. SOLUTION: The substrates consisting of a polycarbonate resin are heat treated for 2 to 6 hours at 100 to 120 deg.C. For example, a released gas rate (q) is proportional to t<-1> (t=discharge time) when the substrates are heat treated for two hours at 120 deg.C. The released gas rate (q) is proportional to t<-0.83> in the heat treatment for two hours at 80 deg.C. Then, the moisture remains in the substrates and the drying is insufficient in the case of the latter but the sufficient drying is resulted in the former. The films of the magneto-optical recording media are formed in a vacuum state on the substrates after the removal of the moisture in the substrates. The film formation is executed by subjecting a vacuum film forming system to a vacuum evacuation for the vacuum evacuation time determined by the heating conditions of the substrates and the number of the substrates to be formed with films, then forming the films of the magneto-optical recording media in the same manner as heretofore and, in succession, forming the protective films. As a result, the disks having the good performance are obtd, with the high productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk, and more particularly to a magneto-optical disk using a polycarbonate resin as a substrate, which has excellent productivity and good performance.

[0002]

2. Description of the Related Art Magneto-optical disks are made of, for example, glass or PM.
A recording medium such as TbFeCo or GdFeCo is attached to a substrate made of plastic such as MA or polycarbonate by vacuum film formation such as vapor deposition or sputtering. Since this magneto-optical recording medium is very susceptible to oxidation, it is usually necessary to carry out the film formation under a high vacuum of 10 ⁻⁴ Pa or less. In case of glass substrate,
The evacuation time for such vacuum film formation does not pose a problem, but in the case of a plastic substrate, the evacuation time for vacuum film formation takes a significant amount of time because the plastic substrate contains a relatively large amount of water. The current situation is that the For example, polycarbonate (P
C) When using a resin as a substrate, since this resin normally contains 0.2 to 0.3% of water at room temperature and humidity, one substrate with a diameter of 13 cm is vacuumed at a pressure of 10 ^-4 Pa. The exhaust time required for exhausting up to was about 10 times as long as that for a normal glass substrate.

[0003]

Therefore, the present invention solves the problems in the industrial production of the above-mentioned magneto-optical disk using polycarbonate as a substrate, and improves productivity by using polycarbonate as a substrate. It is an object of the present invention to provide a magneto-optical disk which is excellent and has good performance.

[0004]

According to the present invention, a magneto-optical disk substrate produced by heating a polycarbonate substrate at a temperature of 90 ° C. to 130 ° C. for 2 to 6 hours, and a substrate for the magneto-optical disk. The heating conditions and the number of magneto-optical disk substrates for film formation are set to a vacuum state after vacuum evacuation of the vacuum film-forming system for a vacuum evacuation time determined by the number of magneto-optical disk substrates to be film-formed. There is provided a magneto-optical disk comprising at least the above-described magneto-optical recording medium and a protective film formed on the magneto-optical recording medium in the vacuum state.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As a polycarbonate resin used as a substrate for a magneto-optical disk according to the present invention, any resin called a so-called polycarbonate resin can be used, and a commercially available polycarbonate resin is preferably used. be able to.

In manufacturing the magneto-optical disk according to the present invention, a polycarbonate resin is used as a substrate and prior to vacuum film formation of a magneto-optical recording medium, as described above, first, a polycarbonate substrate is made to have a thickness of about 90 to 130. ℃,
The heat treatment is preferably performed at a temperature of 100 to 120 ° C. for about 2 to 6 hours, preferably 4 to 6 hours. The heat treatment condition is that the size of the polycarbonate substrate is 12 mm.
It is applied when the thickness is -13 cm and the thickness is 1.2-1.5 mm, but when the size of the substrate is larger or smaller than this, the heat treatment conditions are slightly changed accordingly. In some cases, it may be preferable to add.

According to the present invention, as described above, in order to shorten the exhaust time of the polycarbonate substrate in manufacturing the magneto-optical disk, the polycarbonate substrate is heat-treated in a heating container at 90 ° C. to 130 ° C. for 2 to 6 hours. . With respect to the heating temperature and the heating time, it is necessary to select conditions that allow the water contained in the polycarbonate substrate to be exhausted to the maximum extent in the minimum time. According to the knowledge of the present inventor, the relationship between the discharge gas rate (the amount of gas discharged per unit area per second) q of the polycarbonate substrate and the exhaust time t is as shown in FIG. As is apparent from the graph of FIG. 1, q ∝t without heat treatment
^Although it is ^-0.5 , it becomes q∝t ^-1 when heat-treated at 120 ° C for 2 hours. On the other hand, the heat treatment at 80 ° C. for 2 hours gives an intermediate q∝t ^−0.83 . Theoretically, the relationship is q∝t ^{-1 in} the case of outgassing of molecules adsorbed on the surface, and q∝t ^{-0.5 in} the case of diffusion from the inside of a solid. Technology, see the University of Tokyo Press published in 1983). Therefore, when the heat treatment is carried out at 80 ° C. for 2 hours, moisture remains inside the substrate and the drying is insufficient.
It can be said that the drying is sufficient if the heat treatment is performed at 120 ° C. for 2 hours. As described above, it is possible to determine whether or not the drying processing is sufficient by actually putting the dried substrate in a vacuum device and exhausting the same.

Next, FIG. 2 is a graph showing the relationship between heating temperature and ^x of q∝t ^−x (heating time: 2 hours). That is,
When heated at a temperature of 90 to 130 ° C., the substrate is sufficiently dried. Since the heat distortion temperature of the polycarbonate resin was 135 ° C, heating at a temperature higher than this was not performed.

As described above, in manufacturing the magneto-optical disk according to the present invention, first, in the first step, the polycarbonate substrate is heat-treated at a temperature of 90 to 130 ° C. for 2 to 6 hours to be contained in the polycarbonate substrate. Water is removed, and then, as a second step, a magneto-optical recording medium is formed on the substrate in a vacuum state. In this film formation, the vacuum film formation system is evacuated at a vacuum evacuation time determined by the heating conditions of the magneto-optical disk substrate and the number of magneto-optical disk substrates for film formation. A recording medium is formed into a film, and then a protective film is formed on the magneto-optical recording medium.

[0010]

EXAMPLES As concrete examples, examples of producing magneto-optical discs will be shown with and without pretreatment of a polycarbonate substrate according to the present invention.

Example 1 Polycarbonate resin pellets (Novarex 7020AD2 manufactured by Mitsubishi Kasei Co., Ltd.) were used, and the resin temperature was 3
Diameter 130 after injection molding at 50 ℃ and mold temperature 105 ℃
A disk-shaped substrate having a size of mm × thickness of 1.2 mm was obtained. Next, these 6 substrates were pre-heated at a temperature of 120 ° C. for 2 hours, placed in a vacuum sputtering apparatus, and then evacuated by a cryopump at room temperature (displacement: 4000 liters / second). The vacuum degree of 5 × 10 ⁻⁵ Pa was reached. On the other hand, as a comparative example, when the same procedure as above was carried out except that the above pretreatment was not carried out at a temperature of 120 ° C. for 2 hours, a desired vacuum degree of 5 × 10 ⁻⁵ Pa was reached. It took about 11 hours to do. From this result, it is apparent that the present invention can provide a magneto-optical disk using polycarbonate as a substrate with high productivity.

A protective film (SiN ₃ : 100 mm) was formed on the substrate treated according to the embodiment of the present invention by a conventional method.
Thickness), recording medium (Tb-Fe-Co alloy: 100 mm thickness)
Then, a protective film (SiN ₃ : 100 mm thick) was sputtered in this order to manufacture a magneto-optical disk. The performance of the obtained magneto-optical disk was good.

Example 2 The same polycarbonate substrate as used in Example 1 having a diameter of 130 cm and a thickness of 1.2 mm was placed in a vacuum container having a volume of 66 liters, and it was first sucked up to 10 Pa by a rotary pump having an exhaust volume of 610 liters / min. Next, it was evacuated by a cryopump with a displacement of 4200 liters / second, and the number of substrates and 1 × 10 ⁻⁴
The time required to exhaust to Pa was examined. FIG. 3 shows the obtained results.

In the graph of FIG. 3, the substrate is at 80 ° C.
The case where the heating pretreatment was performed for 2 hours at 120 ° C. and the case where the heating pretreatment was performed at 120 ° C. for 2 hours were compared. As is clear from the results of FIG. 3, the number of substrates and the exhaust time are proportional in the 120 ° C. treatment, but not in the 80 ° C. treatment. That is, if the substrate is not sufficiently dried, the evacuation time cannot be determined. In this way, when q∝t ⁻¹ holds, the exhaust time is proportional to the number of substrates.

[0015]

As described above, according to the present invention, it is possible to obtain a magneto-optical disk having a polycarbonate as a substrate and having a good performance with extremely high productivity.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a discharge gas rate q of a polycarbonate substrate and an exhaust time.

FIG. 2 is a graph showing a relationship between a heating temperature of a polycarbonate substrate and ^x of q∝t ^−x .

FIG. 3 is a graph showing the relationship between the number of polycarbonate substrates shown in Example 2 and the released gas rate q.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area H01F 41/20 H01F 41/20

Claims (1)

[Claims] 1. A polycarbonate substrate at 90 ° C. to 130 ° C.
A magneto-optical disk substrate produced by heat treatment at a temperature of 2 ° C. for 2 to 6 hours, and a vacuum evacuation time determined by the heating conditions of the magneto-optical disk substrate and the number of magneto-optical disk substrates for film formation. After the film forming system is evacuated to a vacuum state, the magneto-optical recording medium is formed on the magneto-optical disk substrate in the vacuum state, and the magneto-optical recording medium is formed on the magneto-optical recording medium in the vacuum state. A protective film, and a magneto-optical disk.