JP2692146B2 - optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc.

[Conventional technology]

An optical disc has been developed and put into practical use as an information recording medium using a high energy density beam such as a laser beam. This optical disc is used for a video disc, an audio disc, a disc memory for large-capacity image files and computer data, and the like.

This optical disc has a disk substrate made of plastic, glass or the like as a basic structure on a disc substrate on which concentric or spiral groups and pits are formed, and has a recording layer thereon. This disk substrate has a through hole at the center for fixing the optical disk to the optical disk device.

[Problems to be solved by the invention]

In recent years, it has been a challenge to realize downsizing without impairing the large capacity of the optical disc due to the improvement in flexibility, but having a through hole in the optical disc reduces the recording area by that much. Will be there.

An object of the present invention is to provide an optical disc that solves such a problem and alleviates a decrease in storage capacity that accompanies a smaller disc diameter.

[Means for Solving the Problems] The structure of the optical disc of the present invention comprises a disc-shaped disc having a small diameter with no through hole in the center, and concentric or spiral groups and pits extending from the disc center to the outer periphery. ,
A recording layer is provided on these groups and pits.

〔Example〕

 The present invention will be described below with reference to the drawings.

FIG. 1 shows a diameter of 12 cm for a single-sided recording system according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a rewritable optical disc of less than. In the figure, a disk-shaped disk substrate 1 made of transparent plastic such as polycarbonate has a diameter of 12 cm or less, and a recording surface 1a is provided with concentric or spiral groups and pits 1b, and dielectrics are formed on these groups and pits 1b. It has a recording region in which the TbFeCo recording film 2 protected by the body layer is formed. Further, an ultraviolet curable resin 3 for protecting the recording area is applied. The plastic disc substrate is integrally formed with groups and pits on the disc substrate by injection molding at positions corresponding to the outer peripheral edge.

As the disc substrate 1, besides plastic,
There is also a substrate in which concentric or spiral groups and pits are formed at positions corresponding to the outer peripheral edge on the glass. In this case, the method of forming the groups and pits on the flat glass substrate by the direct etching method, or the 2P method (Photo-
Polymer method) is used to form groups and pits.

Since the structure of the optical disk of this embodiment does not have a central through hole, the fixing method of the optical disk device is realized by clamping the outer peripheral edge of the disk substrate. If the recording area is eccentric with respect to the center of rotation of the disc substrate 1, accurate tracking cannot be performed, but since the group and the pits 1b are formed at positions corresponding to the outer peripheral edge of the disc substrate 1, There is no problem of eccentricity where tracking does not work properly.

Since this optical disc does not have a central through hole, unlike the conventional optical disc, the entire optical disc surface can be used as a recording surface, and therefore the reduction in recording capacity due to the reduction in diameter of the optical disc can be reduced.

FIG. 2 is a sectional view of an optical disk according to the second embodiment of the present invention. This embodiment shows a double-sided recording type optical disc in which two disc substrates 1 are arranged so that the recording films 2 face each other. The two optical discs are bonded by an adhesive layer 4 such as a hot melt agent. ing.

Also in the case of this embodiment, the reduction of the recording capacity due to the reduction of the diameter of the optical disc can be reduced by adopting the optical disc structure having no central through hole.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reduce the decrease in the storage capacity of the optical disc by reducing the diameter.

[Brief description of the drawings]

1 and 2 are sectional views of the optical discs of the embodiments of FIGS. 1 and 2 of the present invention. 1 ... Optical disc substrate, 1a ... Recording surface, 1b ... Group (pit), 2 ... Recording layer, 3 ... Protective film, 4 ... Adhesive.

Claims (1)

(57) [Claims] 1. A small-diameter disk-shaped disk having no through hole in the center thereof is provided with concentric or spiral groups and pits from the center of the disk to the outer periphery, and a recording layer is provided on these groups and pits. An optical disc characterized in that.