JPH0246539A - Optical disk - Google Patents

Abstract

PURPOSE:To suppress the infiltration of moisture and to prevent the deterioration in adhesive strength of a medium film and the exfoliation thereof by coating the outer peripheral end face of the optical disk formed by sticking two sheets of glass substrates to each other with recording films on the inner side. CONSTITUTION:The medium film 3 consisting of SiN/TbFeCo/SiN is continuously formed by a sputtering method on the glass substrate 1 formed with grooves on the surface by a 2P resin 2 and two sheets of such substrates are stuck to each other by a hot melt adhesive agent 5. The outer peripheral end face is then coated by using an olefinic hot melt as a coating material 4. The exfoliation of the medium film from the substrates is prevented in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical disc, and more particularly to a laminated glass substrate optical disc with improved reliability.

[Prior Art] The outer peripheral edge surface of a laminated glass substrate optical disk is most easily treated without any treatment or with a cold-curing, solvent-free adhesive such as an epoxy resin or a photo-curing acrylate resin. It is being covered with

[Problem to be solved by the invention] Even if the above-mentioned conventional optical disks whose outer peripheral edge surfaces are untreated or coated are available, their materials are epoxy-based, acrylate-based, or olefin-based. For example, in the case of optical disks made of hot melt materials such as ethylene vinyl acetate, etc., when tested at high temperatures and high humidity, the phenomenon that the medium film including the recording film peels off from the substrate occurs, especially from the outer edge of the film formed on the medium film. occurs,
This had become a weakness in the reliability of optical discs.

The present invention has been made to solve the conventional problems as described above, and an object of the present invention is to provide an optical disc that does not cause peeling of the medium film from the substrate and has improved reliability.

[Means for Solving the Problems] The present invention provides an optical disc in which two glass substrates, each of which has a recording film formed on at least one side, are bonded together with the recording film inside. This optical disc is characterized in that the outer peripheral end face is coated with an olefin hot melt.

The olefin hot melt coating part in the present invention is
It may include not only the outer peripheral end surface but also the inner peripheral end surface. Regarding the inner peripheral surface of an optical disk, the hole diameter of 15 Φ, which is the inner peripheral edge of the disk, and the inner peripheral edge diameter of the recording area (usually 60 Φ) are distanced apart, so even if an abnormality occurs, recording will not be possible. Although it is difficult to reach the area and there is little problem even without special treatment, it can be applied not only to the outer circumferential end face but also to the inner circumferential end face if necessary.

[Function] In a laminated glass substrate disk, the moisture permeability of the glass is negligible, so deterioration caused by infiltration of moisture from the outside occurs only from the inner or outer edge of the disk. Moisture penetrates through the 2P resin protruding from the end face, which provides the groups to the glass substrate, or through the bonding adhesive. This moisture reduces the adhesion of the media film, resulting in phenomena such as peeling. When coated with the material of the present invention, this moisture infiltration is suppressed and the adhesion of the media film does not decrease.
Phenomena such as peeling do not occur.

[Example] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of an optical disc according to an embodiment of the present invention. The manufacturing method for this optical disc is as follows:
Glass substrate 1 with groups formed on the surface by resin 2
A medium film 3 made of SiN/TbFeCo/SiN is continuously formed on top by sputtering, and a hot melt adhesive 5 is applied.
Paste the two sheets together. Next, as the outer peripheral end face coating material 4, olefin type #3797 hot melt (manufactured by Sumitomo 3M Ltd.) is used to coat the outer peripheral end face.

The optical disc obtained as above was heated to 80'C.

A high temperature and high humidity test was conducted for 600 hours under the condition of 90% RH, but no abnormality occurred.

As comparative examples, disks without outer peripheral edge treatment and disks coated with epoxy adhesive EP-331 (manufactured by Cemedine Co., Ltd.) were prepared and heated at 80°C and 90% R.
A high temperature and high humidity test was conducted. As a result, it was found that in 100 hours, the media film was 2P
The phenomenon of peeling from the resin began to occur from the outer peripheral edge.

On the other hand, in the disk coated with EP-331, corrosion and peeling of the recording film occurred after 200 hours.

[Effects of the Invention] As described above, according to the present invention, separation between the disk substrate and the medium film does not occur, making it possible to achieve high reliability of the medium of the optical disk and to ensure a long life.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an embodiment of the present invention.

Claims (1)

[Claims] (1) In an optical disc in which two glass substrates each having a recording film formed on at least one side are bonded together with the recording film on the inside, at least the outer peripheral edge of the optical disc is coated with an olefin-based hot melt. An optical disc characterized by: