JPH04232631A - Manufacture of magneto-optical disk - Google Patents

Abstract

PURPOSE:To obtain stable characteristics of less fluctuation of a magneto-optical disk by processing the transparent resin substrate of the magneto-optical disk by using dried air. CONSTITUTION:A transparent resin substrate can be uniformly degassed when the substrate is brought into contact with dried air. It is preferable to adjust the dew point of the dried air used for the degassing process to <=-15 deg.C. In addition, while the temperature of the dried air can be set at any temperature when the temperature is lower than the deformation temperature of the substrate, it is preferable to set the temperature at 50-100 deg.C in order to shorten the drying time by lowering the relative humidity and increasing the diffusion constant of the dried air. Therefore, the characteristic fluctuation of this magneto-optical disk can be reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magneto-optical disk, and more particularly to a method for manufacturing a magneto-optical disk using a transparent resin substrate as the substrate.

0002

2. Description of the Related Art Magneto-optical recording has been studied in various ways as a rewritable high-density recording method, and magneto-optical disks for rewriting using this method have recently been commercialized. In addition to the magneto-optical recording film, a protective film is provided on the transparent substrate to protect the recording film, or a reflective film is provided on the transparent substrate to extract clear signals from the magneto-optical disc at high output. It is constructed by providing a membrane. Further, the films constituting these magneto-optical disks are formed by a vacuum thin film forming method such as a sputtering method or a vacuum evaporation method.

Conventionally, various transparent resin substrates such as polycarbonate, PMMA, and amorphous polyolefin have been used as transparent substrates for magneto-optical disks. When forming a film constituting a disk, there is a problem in that gases such as H2O and O2 are released from the substrate in the vacuum chamber, resulting in a decrease in the degree of vacuum in the vacuum chamber.

Here, the degree of vacuum in the vacuum chamber during the formation of the magneto-optical recording film and the C of the resulting magneto-optical disk are determined.
The relationship between C/N is shown in FIG. 3, and it can be seen from FIG. 3 that if a magneto-optical recording film is formed without sufficiently exhausting the vacuum chamber, the C/N of the magneto-optical disk will drop significantly. Therefore, when manufacturing a magneto-optical disk using a transparent resin substrate, it is common to heat the transparent resin substrate in a vacuum oven in advance to perform a degassing treatment.

However, according to this method, the temperature distribution of the transparent resin substrate during heating becomes wide, making it impossible to perform a uniform degassing process, resulting in large variations in the characteristics of the resulting magneto-optical disk. There was a problem. Further, since dust is thrown up during evacuation or venting in the vacuum oven, there is a problem in that the obtained magneto-optical disk has an increased number of disk defects such as pinholes.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a magneto-optical disk with less variation in characteristics and less occurrence of disk defects.

[0007]

[Means for Solving the Problems] The present inventors have conducted extensive studies to solve the above problems, and have found that by processing a transparent resin substrate using dry air in advance, variations in characteristics can be reduced. The inventors have discovered that it is possible to manufacture magneto-optical disks with fewer disk defects, and have completed the present invention. That is, the present invention is a method for manufacturing a magneto-optical disk using a transparent resin substrate as a substrate, which is characterized in that the transparent resin substrate is brought into contact with dry air.

[0008] In the method of the present invention, by bringing the transparent resin substrate into contact with dry air, the substrate can be uniformly degassed, so that variations in the properties of the resulting magneto-optical disks are reduced.

Dry air is used in the manufacturing method of the present invention. This dry air is not particularly limited, but in order to degas the transparent resin substrate, it is preferable to use dry air with a dew point of -15°C or lower, and in order to perform more sufficient degassing, dry air with a dew point of -20°C or less is preferably used. It is preferable to use one with a dew point of ℃ or less.

[0010]Although the temperature of the drying air used should be below the deformation temperature of the transparent resin substrate, it is necessary to lower the relative humidity and increase the diffusion constant of the drying air to shorten the drying time. The temperature is preferably 100°C.

Furthermore, the contact time between the transparent resin substrate and the dry air is appropriately selected depending on the dew point of the dry air and the temperature of the dry air.

For example, when polycarbonate is used as a resin substrate and dry air with a dew point of -27° C. is brought into contact with it, the weight loss of polycarbonate changes over time as shown in FIG. When the temperature of the drying air is 25°C, the contact time with the drying air is preferably as long as about 100 hours. On the other hand, when the temperature of the drying air is 70°C, a contact time of about 8 hours is sufficient. It can be seen that degassing takes place.

Furthermore, in FIG. 2, the temperature of the drying air used is 2.
The figure shows the change over time in the weight loss of the polycarbonate substrate at 5°C, and it can be seen that if the dew point of the dry air is lowered, the transparent resin substrate can be degassed in a short time.

The method for manufacturing a magneto-optical disk of the present invention is to bring the transparent resin substrate used as described above into contact with dry air, and then form a film constituting the magneto-optical disk by a thin film forming method. Thin film formation can be carried out using conventional methods and conditions.

[0015]

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited to these in any way.

Example Dry air with a dew point of -27°C and a temperature of 70°C was
．． It was left in contact with a 5 inch polycarbonate substrate for 10 hours. Thereafter, a silicon nitride film with a thickness of 1000 angstroms was deposited on this substrate by a sputtering method as a protective film, and a T film with a thickness of 300 angstroms was deposited as a magneto-optical recording film.
A bFeCo alloy film, a 300 angstrom thick silicon nitride film as a protective film, and a 500 angstrom thick aluminum film as a reflective film were deposited.

Fifty magneto-optical disks were manufactured by the above method, and the average C/N, C
/N variation, sensitivity and average number of pinholes were measured. The results are shown in Table 1.

Comparative Example 1 A polycarbonate substrate was degassed in a vacuum oven at a temperature of 70° C. instead of being brought into contact with dry air, and then 50 magneto-optical disks were formed in the same manner as in the example. Manufactured. Table 1 shows the average C/N, variation in C/N, sensitivity, and average number of pinholes of the obtained magneto-optical disks.

Comparative Example 2 Magneto-optical disks were prepared in the same manner as in Example except that the polycarbonate substrate was not brought into contact with dry air.
0 sheets were manufactured. Average C/N of the obtained magneto-optical disk
, C/N variation, sensitivity, and average number of pinholes are shown in Table 1.

[0020]

From the above examples, it can be seen that the characteristics of the magneto-optical disk obtained by the method of the present invention have small variations, and the number of pinholes can be reduced compared to the conventional method using a vacuum oven. Understood.

[0022]

As described above, according to the method for manufacturing a magneto-optical recording medium of the present invention, it is possible to easily manufacture a magneto-optical disk with stable characteristics, and disk defects such as pinholes are reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the change in weight loss over time of a polycarbonate substrate when it is brought into contact with dry air having a dew point of -27°C.

FIG. 2 is a diagram showing the change in weight loss over time of a polycarbonate substrate when it is brought into contact with dry air at a temperature of 25°C.

FIG. 3 is a diagram showing the relationship between the degree of vacuum achieved in the vacuum chamber and the C/N of the obtained disk when a magneto-optical disk is manufactured by forming a magneto-optical recording film in the vacuum chamber. be.

Claims (2)

[Claims] 1. A method for manufacturing a magneto-optical disk using a transparent resin substrate as a substrate, characterized in that the transparent resin substrate is brought into contact with dry air. 2. The method for manufacturing a magneto-optical disk according to claim 1, wherein the dry air has a dew point of -15° C. or lower.