JPH0466060B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to optical disks such as video disks, digital disks for digital audio signals, and computer memory disks.
In particular, the present invention relates to an optical disk in which one surface is a non-recording surface on which information signals cannot be recorded. [Background of the Invention] Conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication No. 57-103135, there has been known an optical disk that allows information signals to be recorded and reproduced only from one side. FIG. 3 is a sectional view showing such an optical disk, in which 1 is the optical disk, 1a and 1a' are substrates, 1b is a recording layer, and 1c is a protective layer. In the figure, the optical disc 1 has a recording layer 1b.
A substrate 1a having a recording layer 1b and a substrate 1a' having a recording layer 1b are bonded together, and information signals can be reproduced or recorded and reproduced by irradiating a light beam from the substrate 1a side. The substrates 1a and 1a' are transparent substrates made of glass, polymethyl methacrylate, polycarbonate, etc., and also have the function of shielding the recording layer 1b and the protective layer 1c from the outside air. Protective layer 1c is recording layer 1
This is to protect b. When the optical disc 1 is a playback-only disc, such as a video disc or a digital disc, the protective layer 1c is an Al vapor-deposited film with a reflectance of 75% or more, and the optical disc 1 is used for recording. In the case of a reproducible disk, a recording material having a reflectance higher than the surface reflectance of the substrate 1a and whose reflectance changes when irradiated with a high-energy light beam (for example, a chalcogen compound, a tellurium compound, etc.) is used. For amorphous thin films such as, their reflectances usually vary in the range of 10 to 40%). When recording or reproducing information signals on such an optical disc 1, as shown in FIG. 3, the optical disc 1 is mounted on a turntable 5, which is rotated by a motor 6, and While the pickup 3 is moved in the radial direction of the optical disk 1 by a drive motor 4, a light beam is irradiated onto the surface of the optical disk. In this case, a photodetector 2 is provided in the read-only device or the recording/playback device. This photodetector 2 emits a light beam, and depending on the presence or absence of reflected light from this light beam, it is determined whether or not the optical disc 1 is mounted on the turntable 5. When the reflected light is detected, Assuming that the optical disc 1 is mounted on the turntable 5, recording or reproducing operation is started. By the way, this optical disc 1 can be recorded or reproduced only from one side (hereinafter referred to as the recording surface), and cannot be performed from the other side (hereinafter referred to as the non-recording side). ). However, as shown in FIG. 3, when such an optical disk 1 is mounted on a turntable 5, the non-recording surface may be erroneously directed toward the photodetector 2 side. Since the pick-up 3 is placed on the same side as the photodetector 3 with respect to the optical disk 1, if the reflectance on the non-recording side is almost equal to or higher than the reflectance on the recording side, the photodetector Instrument 2 is a turntable 5 with an optical disc 1
is determined to be mounted, and recording or reproducing operation from the non-recording side is started. Therefore, since a high-energy light beam is used during the recording operation, the recording layer 1b and the like are destroyed, making the optical disk 1 unusable. Furthermore, in the case of a read-only disk, the amount of light reflected from the disk is small, so that the output of the light source is increased by the automatic control means, and as a result, the pickup is eventually damaged. [Object of the Invention] An object of the present invention is to provide an optical disc that solves the problems of the above-mentioned prior art and can prevent malfunctions of a reproducing device or a recording/reproducing device. [Summary of the Invention] In order to achieve this object, the present invention provides a light blocking device that blocks at least a part of the non-recording surface of an optical disk from a light beam from the photodetector in a playback device or a recording and playback device. The optical disc is characterized in that it can distinguish between the non-recording surface and the recording surface of the optical disc by using the photodetector. [Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the optical disc according to the present invention, and 7a and 7b indicate a label 8a as a recording surface, and 8b as a non-recording surface, which correspond to FIGS. 2 and 3. The parts are given the same symbols. In FIG. 1, a recording surface 8a and a non-recording surface 8
Label 7 with letters, marks, etc. attached to b
a and 7b are attached. Now, optical disk 1 is turntable 5
(FIG. 3), the center of the optical disk 1 at that time is represented by a line A, and the photodetector 2 is mounted at a distance X from the center line A. In this case, the radius R ₁ of the label 7a affixed to the recording surface 8a is R ₁ <X, and the radius R ₂ of the label 7b affixed to the non-recording surface 8b is
Let R ₂ >X. Here, it is assumed that at least the surface reflectance of the label 7b is small. With this configuration, when the optical disk 1 is mounted on the turntable 5 so that the recording surface 8a faces the photodetector 2 side, the amount of light reflected from the optical disk 1 to the photodetector 2 is large, so that photodetection is difficult. The device 2 detects that the optical disc 1 is mounted on the turntable 5, and starts recording and reproducing operations. On the other hand, when the optical disc 1 is mounted on the turntable 5 so that the non-recording surface 8b faces the photodetector 2, the amount of light reflected to the photodetector 2 is small because the surface reflectance of the label 7b is small. Therefore, the photodetector 2 assumes that the optical disc 1 is not mounted on the turntable 5, and recording and reproducing operations are not started. Specific examples of the colors of the label 7b and their detection effects are shown in the following table.

〔Effect of the invention〕

As explained above, according to the present invention, since the reflectance of the non-recording surface of the photodetector is reduced, the optical disk is arranged so that the non-recording surface faces the photodetector. Even if it is installed on a turntable by mistake, recording or playback will not start, making it possible to prevent erroneous recording or playback on the non-recording surface, and to reduce the manufacturing cost of optical discs. It is possible to obtain superior effects such as no significant difference compared to other techniques.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of an optical disc according to the present invention, Fig. 2 is a sectional view showing the basic configuration of a single-sided recording optical disc, and Fig. 3 is an optical disc mounted on a turntable. FIG. 3 is a schematic diagram showing the relative positional relationship between the photodetector and the photodetector. 1... Optical disk, 2... Photodetector, 3...
...Pickup, 5...Turntable, 7a,
7b...label, 8a...recording surface, 8b...non-recording surface.

Claims (1)

[Scope of Claims] 1. An optical disc that records and reproduces information using an optical disc device equipped with a photodetector that determines the presence or absence of a disc based on the presence or absence of reflected light, wherein one surface is a non-recording surface and the other is a non-recording surface. one side is a recording surface, the radius of the label on the recording surface is smaller than the position of the photodetector, the radius of the label on the non-recording surface is larger than the position of the photodetector, and the radius of the label on the non-recording surface is larger than the position of the photodetector; An optical disc characterized in that the reflectance of the label is lower than the reflectance of the recording surface of the optical disc, and recording and reproducing operations on the non-recording surface can be prohibited.