JPH06158281A - Method for manufacturing magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] (Correction) [Object] An object of the present invention is to provide a method of manufacturing a magneto-optical recording medium having a reduced reflectance distribution in the circumferential direction. [Structure] The method for manufacturing a magneto-optical recording medium according to the present invention is
In a method of manufacturing a magneto-optical recording medium using a plastic substrate, the substrate is immediately evacuated to a vacuum degree of 3.5 × 10 ^-7 Torr or less inside the vacuum chamber where the recording layer is placed in the film forming chamber. Is formed, and the reflectance distribution thereof is set to 2% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magneto-optical recording medium, particularly in the same disc and between different lots.
The present invention relates to a method of manufacturing a magneto-optical recording medium with little variation in reflectance and recording / reproducing characteristics.

[0002]

2. Description of the Related Art In recent years, with the progress of information society, a high density and large capacity recording medium is required. Therefore, a magneto-optical disk capable of rewriting information is attracting attention. The magnetic recording medium consists of a dielectric film, a recording film, and a recording film on a substrate made of plastic such as polycarbonate resin.
It is generally known that a reflective film is sequentially formed. However, since this substrate material has hygroscopicity, it absorbs moisture in the atmosphere when stored in a normal environment. Therefore, when forming a recording film or the like on this substrate, leave it in a vacuum for 1-2 hours. However, it is necessary to heat the substrate to about 80 ° C. to release the moisture contained in the substrate in advance and degas.

[0003]

On the other hand, as a recording film constituting this magneto-optical recording medium, an amorphous alloy of a rare earth element and an iron group such as a TbFeCo film is used. Since it is active, it has a drawback that it is easily oxidized. Therefore, when forming this recording film on the substrate,
When the dried and degassed substrate is exposed to the atmosphere, water is taken up into this substrate immediately, and when the recording film is formed as it is, the water taken up by the substrate is released into the film formation chamber. As a result, the recording film is oxidized, which causes a problem that the reflectivity changes and a distribution of the reflectivity values occurs in one disk.

[0004]

The present invention relates to a method of manufacturing a magneto-optical recording medium which solves the above disadvantages and problems, and it relates to a method of manufacturing a magneto-optical recording medium using a plastic substrate. The substrate is put into a high vacuum chamber immediately before the film formation is started, and the inside of the high vacuum chamber is evacuated to a vacuum of 3.5 × 10 ^-7 Torr or less, and then the recording layer is formed in the film formation chamber and the reflectance distribution is 2%. It is characterized by the following.

That is, the present inventors
As a result of various studies on a method of manufacturing a magneto-optical recording medium with little variation in reflectance and recording / reproducing characteristics between different lots, when a recording film or the like is formed on a substrate made of a polycarbonate resin by a sputtering method or the like, this substrate is used. Is kept in a vacuum state in a vacuum chamber, and it was found that if the degree of vacuum is set to a high vacuum of 3.5 × 10 ^-7 Torr or less, it is possible to suppress the dispersion of the reflectance within one disk to a small level. The present invention was completed by further studying the reaction conditions and the like. This will be described in more detail below.

[0006]

The present invention relates to a method of manufacturing a magneto-optical recording medium, which is a method of manufacturing a magneto-optical recording medium using a plastic substrate, in which the degree of vacuum in a high vacuum chamber inside the high vacuum chamber in which the substrate is placed immediately before the start of film formation. Is evacuated to 3.5 × 10 ^-7 Torr, and then the recording layer is formed in the film formation chamber so that the reflectance distribution is 2% or less. This provides an advantage that a magneto-optical recording medium having a small reflectance distribution in the disc and a small reflectance distribution between different lots can be easily manufactured.

The present invention relates to a method of manufacturing a magneto-optical recording medium. In this manufacturing process, first, a plastic substrate made of polycarbonate resin or the like is degassed in an oven set at 90 ° C. for 1 hour or more. , Remove it from the oven, attach it to the disk carrier, and then put it in the vacuum exhaust chamber (loading chamber). After that, this disk carrier is evacuated in the loading chamber and then sent out to the film forming chamber,
In this film forming chamber, as in a normal film forming process, a silicon nitride film as a first dielectric layer, a rare earth / iron group amorphous alloy as a recording film, such as TbFeCo, is formed on the plastic substrate.
A film, a silicon nitride film as a second dielectric layer, an Al alloy film as a reflective film, and the like are formed by a sputtering method or the like to obtain a magneto-optical recording medium.

In this case, however, the ultimate vacuum in the loading chamber before the start of film formation was variously changed to prepare a magneto-optical recording medium (optical disk), and the reflectance distribution on the same disk was measured. This reflectance was measured by using an ordinary optical disc evaluation device, while the disc was rotated at 1,800 rpm and the optical head was tracked to a position with a radius of 24 mm. The reflectance is measured for 12 of these sectors, and the reflectance variation ΔR / R is (Rmax-Rmin) / Rmax +, where Rmax is the maximum reflectance value and Rmin is the minimum reflectance value. Defined by Rmin.

Based on this, the ultimate vacuum is 1 × 10 ^-6 To
When the reflectance of the discs obtained when each vacuum was reached in the case of 1 × 10 ⁻⁷ Torr from rr within the same disc was examined, the results shown in FIG. 1 were obtained. , The reflectance distribution was 12% at 1 × 10 ^-6 Torr, but at 3 × 10 ^-7 Torr
It was found to be 1.8%, and as a result, it was found that the reflectance can be set to 2% or less by setting it to 3.5 × 10 ⁻⁷ Torr or less.

The degree of vacuum when the loading chamber is evacuated by the vacuum pump is determined by the capacity of the chamber, the performance of the vacuum pump, and the evacuation time. Therefore, when the chamber capacity is small and the evacuation speed of the vacuum pump is high. Can be evacuated to a high vacuum in a short time, which is advantageous in terms of productivity, but in the case of the present invention, this is 3.5 × 10
^It can be anything that can pump up to ^-7 Torr.

[0011]

EXAMPLES Next, examples of the present invention will be given. Example A polycarbonate substrate having a diameter of 86 mmφ and a thickness of 1.2 mm and provided with a tracking groove was left in an oven heated to 90 ° C. for 1 hour (gas mainly taken in the substrate). Water) was sufficiently discharged. Then, the substrate was taken out into the air, mounted on a disk carrier, placed in a loading chamber, and evacuated to a vacuum degree of 3.5 × 10 ⁻⁷ Torr.

Next, at this degree of vacuum, a silicon nitride layer (thickness 30 nm) as a first dielectric film, a recording layer made of TbFeCo (thickness 13 nm) and a second dielectric layer were formed on this substrate by magnetron sputtering. A silicon nitride layer (thickness 30 nm) as a body film and an aluminum layer (thickness 60 nm) as a reflection film were sequentially formed to form a magneto-optical recording medium, and the reflectance distribution in the recording film layer was examined. However, it was confirmed that this was 2% or less and variation in the value could be suppressed between lots.

[0013]

The present invention relates to a method of manufacturing a magneto-optical recording medium, which is a vacuum in which a substrate is placed before the start of film formation in the method of manufacturing a magneto-optical recording medium using a plastic substrate as described above. The degree of vacuum in the room is 3.5 × 10
After evacuation to ^-7 Torr or less, the recording layer is formed in the film forming chamber, and the reflectance distribution is set to 2% or less. It is advantageous that the distribution of the reaction rate in the same disk of the magnetic recording medium is small and the distribution of the reflectance between different lots can be small.

[Brief description of drawings]

FIG. 1 Ultimate vacuum (Torr) of a loading chamber when a recording layer or the like is formed on a substrate of a magneto-optical recording medium
3 is a graph showing the relationship between the obtained reflectance distribution in the circumferential direction of the obtained magneto-optical recording medium.

Claims (1)

[Claims] 1. A method of manufacturing a magneto-optical recording medium using a plastic substrate, which is evacuated to a vacuum degree of 3.5 × 10 ⁻⁷ Torr or less in a vacuum chamber in which the substrate is placed immediately before the start of film formation. A method for manufacturing a magneto-optical recording medium, wherein a recording layer is formed in a film forming chamber, and the reflectance distribution is 2% or less.