JPH0542739B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the structure of an optical information carrier disk.

Structure of conventional examples and their problems Generally, an optical information carrier disk has an information medium layer provided on a transparent substrate such as glass or plastic. During reproduction, laser light is irradiated and the information medium layer reflects light. It reads information recorded using light or transparent light. In this information carrier disk, if the information medium layer is scratched, it will cause a big problem when recording and reproducing information. Furthermore, when the information medium layer absorbs moisture from the air, it tends to deteriorate easily. It is therefore necessary to protect the information carrier layer from mechanical damage and moisture.

A common method for protecting the information medium layer is to bond another transparent substrate on top of the information medium layer, or to provide a hardened film made of a resin material or the like on top of the information medium layer. It is.

The former has problems such as an increase in the number of steps and costs, and the latter is more advantageous in terms of manufacturing. Here, the latter will be explained in more detail.

A method for forming a cured film on the information medium layer is to apply, for example, an ultraviolet-curable liquid organic material while rotating the substrate at a low speed, and to make the film thickness uniform while rotating at a medium speed. Thereafter, the material is rotated at high speed to shake off excess material, and then rotated again at medium speed to shape the outer peripheral edge while curing by irradiating ultraviolet rays. The so-called spin coating method has the highest productivity and is commonly used.

Here, when providing a hardened film to protect the information medium layer, if the hardened film is provided only on the surface having the information medium layer, warping will occur on the substrate due to curing shrinkage of the hardened film material, and the size of this warping will increase. The thickness is approximately proportional to the thickness of the cured film. If the cured film is made thick enough to strongly protect the information carrier layer, the warpage will increase to such an extent that it cannot be used as an optical information carrier disk. Therefore, in order to increase the thickness of the cured film, it is necessary to provide the cured film on both sides of the substrate.

FIG. 1 shows an example of a conventional optical information carrier disk, in which an information medium layer 2 is formed on an information track 4 on a disk-shaped transparent substrate 1, and a hardened film 3 is provided on both sides by spin coating. It is something. However,
When a cured film is provided by spin coating, the inner peripheral edge of the cured film becomes a distorted circle 10. This not only impairs the aesthetic appearance but also causes film thickness unevenness 11 in the cured film as shown in FIG.
The unevenness on the surface of the cured film caused by this causes a lens effect on the laser light, preventing the laser light from being properly focused on the information medium layer 2, which may impede the recording and reproduction of information, or cause the laser light to not reach near the center hole of the disk. Due to the uniformly flowing hardened film, there was a problem in that when it was mounted on the turntable of a recording/reproducing device during use, it would tilt and the surface would be shaken significantly.

OBJECT OF THE INVENTION The present invention solves the above-mentioned drawbacks.
To provide an optical information carrier disk which has a good appearance, has no recording/reproducing defects due to irregularities on the surface of a cured film, and can be mounted on a turntable of a recording/reproducing device without causing surface wobbling during use.

Structure of the Invention The optical information carrier disk of the present invention includes a disk-shaped transparent substrate, an information medium layer provided on one side of the transparent substrate, and a transparent hardened layer provided on both sides of the transparent substrate by spin coating. A circular step is formed around the rotation axis of the transparent substrate on both sides of the transparent substrate at a position inner than the information medium layer, and the position of the step and the transparent cured film are The inner circumferential edges of the discs are made to coincide with each other, and they have a good appearance and do not suffer from recording/reproduction defects due to unevenness on the surface of the cured film, and can be reliably mounted on the turntable of a recording/reproduction device during use.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Components that are the same as those of the conventional example are indicated by the same numbers.

FIG. 3 is a longitudinal sectional view of an embodiment of an optical information carrier disk according to the invention. An annular convex portion 5 centered on the rotation axis of the transparent substrate 1 is formed on both sides near the inner circumference of a disk-shaped transparent substrate 1, and an information track 4 and an information medium are formed on one surface on the outer circumference side. layer 2
, and a cured coating 3 is provided on both surfaces so that the inner circumferential edge thereof coincides with the annular convex portion 5. In this case, by providing the convex portion 5, the liquid before hardening of the cured coating 3 does not flow inward from the convex portion, so the inner peripheral edge becomes a perfect circle along the convex portion 5, which gives a good appearance and By making the film thickness uniform at the edges, the film thickness of the cured film 3 also becomes uniform at the middle circumferential portion of the substrate 1. In other words, the surface of the hardened coating 3 becomes a flat surface with no irregularities, so the laser beam is focused normally, and there is no obstacle to recording and reproducing information, and the turntable of the recording and reproducing device is transferred to the turntable without surface wobbling during use. It can be worn.

FIG. 4 is a longitudinal sectional view of another embodiment of the optical information carrier disk according to the invention. In this method, an annular recess 6 centered on the rotation axis of the transparent substrate 1 is formed on both sides near the inner periphery of a disk-shaped transparent substrate 1, and an information track 4 and an information medium layer are formed on one surface on the outer periphery. 2, and a cured film 3 is provided on both sides. In this case, at the corner 6-1 of the recess 6, due to the surface tension of the cured coating material, the inner peripheral edge of the cured coating 3 forms a perfect circle along the corner 6-1, as in the case of FIG. It has a good appearance, the surface of the cured film 3 is a flat surface with no irregularities, and it can be mounted on a turntable of a recording/reproducing device without causing surface wobbling during use.

In the embodiment of FIG. 4, instead of the recess 6 on either side, a protrusion like the embodiment of FIG. 3 may be provided. Further, a step 7 or 8 as shown in FIGS. 5 and 6 may be provided.

That is, by providing a step, whether convex or concave, the inner circumferential edge of the cured film can be regulated, and the same effect can be obtained.

Effects of the Invention As described above, the optical information carrier disk according to the present invention includes a disk-shaped transparent substrate, an information medium layer provided on one side of the transparent substrate, and a spin coating on both sides of the transparent substrate. A circular step is formed with the rotation axis of the transparent substrate as the center on both sides of the transparent substrate at a position inner than the information medium layer, and the position of the step and By aligning the inner circumferential edges of the transparent cured coating, the appearance is better than before, there is no recording/playback failure due to unevenness on the surface of the cured coating, and the recording/playback device does not cause surface wobbling during use. It can be attached to a turntable.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a conventional optical information carrier disk, and Fig. 2 is a plan view of the optical information carrier disk of Fig. 1.
AA sectional view, FIG. 3 is a vertical cross-sectional view of an optical information carrier disk in one embodiment of the present invention, FIG. 4 is a vertical cross-sectional view of an optical information carrier disk in a second embodiment of the present invention, and FIG. The figure is a sectional view of a main part of an optical information carrier disk according to a third embodiment of the invention, and FIG. 6 is a sectional view of a main part of an optical information carrier disk according to a fourth embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... Information medium layer, 3... Cured film, 4... Information track, 5... Annular convex part,
6... Annular recess, 7... Concave step, 8... Convex step.

Claims (1)

[Claims] 1 Consisting of a disc-shaped transparent substrate, an information medium layer provided on one side of the transparent substrate, and a transparent hardened coating provided on both sides of the transparent substrate by spin coating, the information medium on the transparent substrate A circular step centered on the rotation axis of the transparent substrate is formed on both sides at a position inner than the layer, and the position of this step is aligned with the inner circumferential end of the transparent cured coating. Optical information carrier disk.