JPH04372737A - Optical recording medium - Google Patents

Abstract

PURPOSE:To assure an extremely smooth surface characteristic and to improve CSS durability by adhering an information layer formed on a substrate and a film having <=400mum thickness with a u/v cured resin in a vacuum. CONSTITUTION:A magneto-optical recording medium is so set in a vacuum that the recording surface is the front surface by using a vacuum sticking device and the u/v curing resin is applied thereon. The polyethylene terephthalate film is then dropped from above and is subjected to u/v exposing from the front surface. Dust is embedded in the final into the u/v resin layer in spite of the intrusion of the dust therein and the surface coated with the u/v resin is made equiv. to the smoothness of the polyethylene terephthalate film. Further, the durability by the test (CSS test) repeating the rotation and stop of the medium at the time of executing the overwriting of the magneto-optical recording memory is easily assured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of optical recording media.

0002

[Prior Art] A cross-sectional view of a conventional single-plate optical recording medium is shown in FIG.
As shown in FIG. 2, there is usually only a protective layer 23 on top of the information layer 22. For example, 21 is a 1.2 mm thick polycarbonate substrate, 22 is a magneto-optical recording layer as an information layer, and 23 is a U/V hardened resin layer as a protective layer. This u
/v The cured resin layer is usually applied by spin coating and has a thickness of about 5 μm.

0003

[Problems to be Solved by the Invention] However, the above-mentioned conventional techniques have problems in that the thickness of the U/V cured resin layer cannot be increased or that coating unevenness and dust defects occur due to the spin coating method. .

SUMMARY OF THE INVENTION The present invention aims to solve these problems, and its purpose is to provide an optical recording medium with a substantially thicker protective layer and a smoother surface of the protective layer. There it is.

[0005]

[Means for Solving the Problems] The optical recording medium of the present invention includes:
An optical recording medium in which information is reproduced, recorded, or erased through a substrate using a laser beam, characterized in that at least an information layer formed on the substrate and a film with a thickness of 400 μm or less are bonded in a vacuum with a U/V curing resin. shall be.

[0006]

[Function] According to the above structure of the present invention, since a transparent film is used, the surface condition of the protective layer (U/V resin layer + film) is the surface condition of the film, and the smoothness of the film is preserved. Therefore, it is very smooth. Also, u/v
The thickness of the resin layer can also be adjusted freely by using U/V resins of various viscosities. Furthermore, even if dirt exists in the U/V resin, it will be covered by the film and the smoothness will be preserved.

[0007]For easier understanding, the explanation will be made using figures. FIG. 2 shows a U/V resin protective layer provided by conventional spin coating, but the presence of dust 24 impairs the smoothness of the surface. Furthermore, when a highly viscous resin is spin-coated, uneven coating tends to occur. FIG. 3 is a schematic cross-sectional view of conventional surface coating unevenness. 31 is a u/v resin layer with uneven coating.

On the other hand, FIG. 1 shows a sectional view of an optical recording medium according to the present invention. 11 is a polycarbonate substrate with a thickness of 1.2 mm, 12 is a magneto-optical recording layer as an information layer, and 13 is a U/V cured resin layer as a protective layer and adhesive layer. 14 is garbage, 15
is a film.

As described above, when the method for protecting the information layer according to the present invention is adopted, even if there is dust, it will be buried in the U/V resin, and the smoothness of the film surface, which is the substantial surface of the protective layer, will be maintained. be done. Moreover, the surface tension of the U/V resin ensures a very smooth surface even in the case of uneven coating.

0010

[Example] 3.5 inch size polycarbonate (P
C) A magneto-optical recording film is formed on a substrate, and the medium is set in a vacuum bonding device. FIG. 4 is a conceptual diagram of the vacuum laminating apparatus used in producing the medium of the present invention. 40 is a vacuum chamber, 41 is a vacuum pump, 42 is a motor, 43 is a dispenser nozzle for applying adhesive, 44 is a dispenser horizontal movement unit, 45 is a dispenser unit, and 46 is a frame supporting the film 49. . The transparent film used in this example was made of polyethylene terephthalate and had a thickness of 100 μm. 47 is a switch that releases the support of the film 49 and drops the film 49 onto the recording medium 48.

Using the vacuum laminating apparatus shown in FIG. 4, the 3.5-inch magneto-optical recording medium was set in a vacuum with the recording surface facing upward, and a U/V curing resin was applied. Thereafter, a polyethylene terephthalate film was dropped from above, and U/V exposure was performed from above. FIG. 1 is a cross-sectional structural diagram of the resulting medium. As can be seen from FIG. 1, even if dust gets mixed in, it will sink into the U/V resin layer, and the surface coated with the U/V resin will have the same smoothness as the surface of the polyethylene terephthalate film. The thickness of this u/v resin layer was about 50 μm.

[0012] By adopting the structure of the present invention as described above,
Some major effects were obtained.

One is when a magnetic field modulation method using a flying head is used to overwrite a magneto-optical recording memory, a flying head is placed on the film as shown in FIG. 1, and the medium is repeatedly tested for rotation and rest (CSS test). Durability is easily ensured (1 million times). On the other hand, if there is dust on the protective coat shown in FIG. 2 or if there is uneven application of the protective coat shown in FIG. 3, a head crash will occur after a few times, making it impractical.

Another advantage is that the change in the amount of warpage of the medium is reduced when temperature and humidity changes peculiar to single-plate media (not laminated media) occur. Into a constant temperature and humidity chamber at 80°C and 85% RH, the medium with the configuration of the present invention shown in Fig. 1 and the conventional medium with the configuration of Figs.
The medium was taken out at room temperature and humidity at 0% RH, and the amount of warpage of the medium immediately after being taken out was measured. The results showed that the amount of change in warpage of the medium with the configuration of the present invention was limited to 2 mrad, while the amount of change in warp of the medium with the conventional configuration was 8 mrad.
It becomes rad.

Although this embodiment was used as a magneto-optical recording medium, it may also be used as a phase change type optical recording medium, an optical disk such as a CD/LD, or a CD-Write Once type as long as it does not depart from the spirit of the present invention. Applicable to various optical discs. In addition, the transparent film used in this example was polyethylene terephthalate, but other materials include polycarbonate, polyester, glass, polyvinyl chloride, polyethylene, polymethyl methacrylate, amorphous polyolefin, polystyrene, polyimide, polyolefin, cellulose, and Teflon. Materials such as celluloid, polyvinyl acetate, vinylon, polyurethane, silicone resin, etc. and metal films can also be used.

Furthermore, the reason why the film thickness is limited to 400 μm or less is because, due to the space available in the case (generally called a cartridge) in which the optical disc is placed, if the film exceeds this thickness, rubbing will occur within the cartridge.

[0017]

As described above, according to the present invention, an extremely smooth surface can be ensured by placing a film on and adhering the information layer, compared to simply applying a protective coat on the information layer in the past. It has good durability and has the effect of reducing changes in the amount of warpage.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an optical recording medium according to the present invention.

FIG. 2 is a cross-sectional view of a conventional single-plate optical recording medium.

FIG. 3 is a schematic cross-sectional view of conventional surface coating unevenness.

FIG. 4 is a conceptual diagram of a vacuum laminating apparatus used in producing the medium of the present invention.

[Explanation of symbols]

11 1.2mm thick polycarbonate substrate 12
Magneto-optical recording layer 13 as an information layer U/V hardening resin layer 14 as a protective layer and adhesive layer
Dust 15 Film 21 1.2mm thick polycarbonate substrate 22 Information layer 23 Protective layer 24 Dust 31 Coating unevenness 40 Vacuum chamber 41 Vacuum pump 42 Motor 43 Adhesive application dispenser nozzle 44 Dispenser horizontal movement unit 45 Dispenser unit 46 Frame 47 Switch 48 Recording medium 49 film

Claims (1)

[Claims] Claim 1: In an optical recording medium in which information is reproduced, recorded, or erased through a substrate using a laser beam, at least an information layer formed on the substrate and a film having a thickness of 400 μm or less are U/V cured in a vacuum. An optical recording medium that is bonded with resin.