JPH09120591A - Method for coating optical disk with organic protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily use a resin difficult to apply as an org. protective film material by thermally spraying the material for protecting the film forming face of an optical disk on the face. SOLUTION: A thermal spraying device for coating is made of a thermal spraying gun 1 with an oxygen cylinder, an acetylene cylinder and a compressed air feeding pipe. At the time of coating, a powdery resin filled into the vessel 2 of the gun 1 is melted with a flame of gaseous acetyelen-oxygen mixture and the resultant molten resin is sprayed as fine mist from the nozzle of the gun 1 on an optical disk substrate 3 by blowing compressed air to form a thin resin coating film on the substrate 3. A properly rugged texture pattern is formed by coating the same face with the resin plural times and then the resin is solidified and fixed on the surface of the substrate 3 to form an org. protective film.

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 an optical disk, and more particularly to a method for applying an organic protective film on an optical disk.

[0002]

2. Description of the Related Art Conventionally, a method of applying an organic protective film to a magneto-optical disk is to apply an ultraviolet curable resin to the inner circumference of the disk, then spin the disk by spin coating and shake it off to form a uniform film. Generally, a method of curing the resin with ultraviolet rays or a coating method of dipping the disk in an ultraviolet curable resin or the like and then shaking it off to cure the resin with ultraviolet rays has been generally used. After that, in the magnetic field modulation disk, a so-called texture pattern is formed to roughen the substrate surface in order to prevent a crash during sliding of the disk head. This is formed by polishing the protective film surface with a polishing tape and then cleaning. Was performed to wash the polishing dust.

[0003]

However, in such a method, it is necessary to use an ultraviolet curable resin in order to impart the function of high hardness and high durability required for the protective film,
A usual ultraviolet curable resin is mainly an acrylic polymer and has a limited hardness. In addition, the ultraviolet curable resin itself is expensive, resulting in a cost increase and the need for an ultraviolet lamp.

Further, in the magnetic field modulation disk, it is necessary to add a texture pattern to the surface of the disk in order to prevent the crash when the head of the disk slides as described above. A fixed-abrasive method, which uses a polishing tape in which alumina abrasive grains and the like are coated on a base film together with a binder, is the mainstream method for applying this texture pattern. However, there is a problem in that polishing debris, polishing liquid, etc. remain in the layer to be processed, so that a cleaning step must be provided to remove them.

[0005]

Means for Solving the Problems In view of the above problems, the inventors of the present invention have conducted extensive studies, and as a result, formed a texture pattern on the surface by a thermal spraying method in which an organic protective film material heated and melted is sprayed with compressed air. Focusing on the formation of the organic protective film of the present invention, various studies were conducted to complete the present invention. That is, the present invention provides an organic protective film coating method for protecting a film-formed surface of an optical disc, wherein an organic protective film material is sprayed onto the film-formed surface of the optical disc. It is what This will be described in more detail below.

The coating method in the present invention can be carried out, for example, by a known thermal spraying apparatus shown in FIG. The thermal spray apparatus shown in FIG. 1 comprises a thermal spray gun 1 in which an oxygen cylinder, an acetylene cylinder and a compressed air supply pipe are arranged. The coating method is as follows: The powdered resin filled in the container 2 of the spray gun 1 is melted by an acetylene / oxygen mixed gas flame, and while maintaining this state, compressed air is blown into the melted resin from the nozzle of the spray gun. Is sprayed onto the disk substrate 3 to form a coating film. At this time, the resin melted by the gas flame is sprayed into a fine mist on the optical disk by the compressed air, and the resin in the mist hits the surface of the optical disk to form a thin resin film. In this way, by applying the resin a plurality of times on the same surface, a texture pattern with appropriate unevenness is formed. After that, the resin is solidified and fixed on the surface of the optical disc to form an organic protective film.

The resin used in the present invention may be any of a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin and the like. A thermosetting resin that undergoes a crosslinking reaction by heat is more preferable.
Examples of the thermoplastic resin include polyethylene and polystyrene, and examples of the thermosetting resin include an epoxy resin and a melamine resin. If the average particle size of the resin is too large, there is a problem of head crash with the substrate, and if it is too small, there is a problem that the head does not float, so that the average particle size is 20 μm to 1 μm.
The range may be 00 μm. The resin used in the present invention preferably has a pencil hardness of F or higher. If it is softer than F, there is a problem that the protective film is scraped off by contact with the head. If the surface roughness of the texture pattern is too rough, there is a problem of head crash, and if it is too fine, there is a problem that the head does not float. Therefore, Ra is 0.01 μm to 0.5.
It may be in the range of μm. The average film thickness after curing is
When it is too thin, there are problems such as corrosion and weak mechanical durability, and when it is too thick, there is a problem of warpage, so 1 μm to 30 μm
The range may be m. Further, the acetylene / oxygen pressure ratio and the compressed air pressure at this time may be known values.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to Examples and Comparative Examples.

[0009]

EXAMPLE In FIG. 1, an epoxy resin having an average particle size of 100 μm (manufactured by Yutec Co., product name S
(SM40-29300) filled in a container 2 with a thermal spray gun 1 (manufactured by Nippon Yutec Co., Ltd., product name DS8000) and epoxied into a molten state by a gas flame of acetylene / oxygen = 4.0 / 0.7 kgf / cm ^2. The resin was compressed with 2.0 kgf / cm ² of compressed air,
It was sprayed and applied to the film-forming surface of the optical disk substrate 3 having an outer diameter of 86 mm and an inner diameter of 15 mm, which were separated by a distance of about 60 cm. During the thermal spraying, the substrate of the optical disk was not sprayed by the heat of the gas flame, and the thermal spraying was performed in five times in 10 seconds to form a protective film having a texture pattern on the optical disk film formation surface. The average film thickness of the protective film was about 103 μm, the pencil hardness was H, and the surface roughness Ra was 0.1 μm. The average byte error rate of the five optical disks obtained was 8 × 10 ⁻⁶ .

Comparative Example For comparison, after applying a conventional spin coat method to form a protective film, the surface was polished with an abrasive tape to form a texture pattern. OD-1 (spin coater product name) manufactured by Origin Electric Co., Ltd. is used as the spin coater, and an ultraviolet curable acrylic resin (product name SD manufactured by DIS company is used within a range of 22 mm from the center of the film forming surface of the substrate of the optical disk.
-301), then spin the substrate by rotating the substrate, and then use an ultraviolet lamp for 12 seconds of ultraviolet light (output 3
kV) was irradiated to cure the resin, and a protective film was formed on the optical disk film formation surface. Next, in order to give a texture pattern, a # 4000 polishing tape was used to polish the surface of the protective film with a load of 0.8 kg / cm ² , and then the surface was washed. The average film thickness of this resin was 14 μm. The pencil hardness of the resin was F and the surface roughness Ra was 0.04 μm. The average byte error rate of the five optical disks obtained was 8 × 10 ⁻⁶ .

[0011]

According to the present invention, a resin which has been difficult to apply can be used as an organic protective film material easily, and a resin which is expected to have a functionality can be applied directly onto an optical disk. The cost of resin and equipment can be reduced. Furthermore, a texture pattern can be formed on the surface of the protective film at the same time, which can shorten the process.

[Brief description of the drawings]

FIG. 1 is a schematic view of a coating apparatus used in the present invention.

[Explanation of symbols]

 1 Thermal spray gun 2 Container 3 Optical disk substrate

Claims (2)

[Claims] 1. An organic protective film coating method for protecting a film-forming surface of an optical disk, which comprises spraying an organic protective film material onto the film-forming surface of the optical disk. 2. The method for applying an organic protective film on an optical disk according to claim 1, wherein a texture pattern is formed on the organic protective film.