Dynamic information storage or retrieval – Storage medium structure – Specific disc profile
Patent
1983-10-04
1985-10-08
Stephan, Steven L.
Dynamic information storage or retrieval
Storage medium structure
Specific disc profile
369283, 369286, 427240, G11B 1902, B05D 138
Patent
active
045464642
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a method of manufacturing an optical recording/reproducing disc, and more particularly an optical recording/reproducing disc which is difficult to injure, and which is provided at the outer peripheral surface with a disc protecting layer to thereby protect a region for recording/reproducing signals.
BACKGROUND ART
Conventionaly, an optical recording disc has been formed by a round plastic plate having a recording layer capable of optically recording/reproducing and thereafter another plastic plate placed over the recording layer for protecting it. The protective plastic plate for the recording layer, however, has a problem in that the surface of the recording disc, when placed on a flat surface, is injured by contact with dust or foreign objects during manufacture. This has been a problem also with an optical recording/reproducing disc using a laser beam. In other words, a problem has been created in that the flaws on the protective plate will appear as noise during recording and/or reproducing of signals.
SUMMARY OF THE INVENTION
An optical recording/reproducing disc according to the invention comprises a round plastic plast, a recording layer provided on the plastic plate and enabling optical recording and/or reproducing, and a round protective layer of plastic material provided on the recording layer and having at the outer peripheral end a projection higher by 10 to 200.mu. than the inner peripheral surface at the effective recording/reproducing surface, thereby to protect the recording layer, so that when the disc is placed on a flat surface the projection of the protective layer forms a space between the recording layer and the flat surface, thereby preventing flaws from being produced by contact with dust or a foreign object.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional side view of an embodiment of an optical recording/reproducing disc manufactured according to the method of the invention, and
FIGS. 2, 3 and 4 are partially sectional views of outer peripheral end portions of the embodiment of FIG. 1 and of modified embodiments manufactured according to the method of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
The optical recording/reproducing disc base member of the invention, as shown in FIG. 1, mainly comprises three layers. Namely, a recording layer 2 necessary for optical recording and/or reproducing is interposed between two plastic plates 1 of acrylic resin each having a center bore and a diameter of 210 mm. In further detail, the recording layer 2 utilizes the principle that irradiation by a laser beam causes a phase transition to change the reflectivity of the layer.
FIGS. 2 and 3 are partially enlarged sectional views of a portion designated by A in FIG. 1, and each shows the disc in FIG. 1 coated with a protective layer 3. The disc in FIG. 2 is chamfered as at 4 at the corners of the outer peripheral end portion of disc, and the disc in FIG. 3 is rounded-chamfered at the same portion. A projection 6 is provided at the outermost periphery of each disc. In FIG. 4, the projection 6 of the protective layer 3 provided at the outermost peripheral end of the disc comprising the plastic plates 1 and recording layer 2 preferably has a height m as large as possible. However, when height m becomes too large, the area of projection 6 and width l thereof are increased, resulting in a poor appearance. Thus, the projection 6 preferably has a height of about 200.mu. or less from the viewpoint of the positional relation with the laser head. However, a height of 10.mu. or less has not been effective in prevention of flaws caused by dust or the like. The embodiment in FIG. 4 is obtained by a coating operation wherein a coating liquid is filled in a dip tank, and the coating material is applied simultaneously to both surfaces of the resin disc by rotating the disc by a rotary shaft, thereby simultaneously forming the protective layer 3 and projection 6.
The coating apparatus and method used for this embodiment prov
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patent: 4175145 (1979-11-01), Fetchet
patent: 4371954 (1983-02-01), Cornet
Inoue Takao
Maeda Yukio
Uchida Masami
Matsushita Electric - Industrial Co., Ltd.
Stephan Steven L.
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