JPH0644355B2 - Light disk - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a structure of an optical disk such as a read-only video disk for reproducing information by laser light and a compact disk recording / reproducing (erasing) disk memory.

[Technical Background of the Invention and Problems Thereof] Generally, an optical disk substrate such as a video disk, a compact disk, a disk memory or the like is manufactured by injection molding an acrylic resin or a polycarbonate among thermoplastic resins.

The substrate manufactured in this manner is excellent in transferability of information patterns, transparency and heat resistance of the substrate, and low in water absorption and birefringence, and is thus excellent as a substrate for optical discs.

Currently, a reproduction-only optical disc (video disc) is capable of double-sided reproduction. A metal reflective film (generally Al) is provided on the recording surface of an optical disk substrate having a recording surface on only one surface by vapor deposition or sputtering, and a pair of metal reflective films are made to face each other and bonded by an adhesive. . With such a structure, the recording capacity of the optical disk is doubled, and the deformation over time due to changes in temperature and humidity of the environment is reduced.

By the way, conventionally, as an adhesive for laminating optical disks, an adhesive in which rubber is dissolved in a solvent, an epoxy adhesive, and a hot mel adhesive are known. However, these adhesives have the following problems. The adhesive obtained by dissolving the rubber of (1) in a solvent often attacks the synthetic resin substrate and the metal reflection film. Also, the epoxy-based adhesive will cure at room temperature,
It takes a very long time, one day or more, to completely cure, and it is not flexible after curing. Although the hot-melt adhesive of No. 1 is hardened quickly, the adhesive is in a molten state, so that the disk is heated by heat and is subject to thermal strain, which causes deformation and warpage, and easily causes blurring during rotation. Further, since the viscosity is high, the adhesive layer is apt to be thick, and there is a drawback that an expensive coating device is required for uniform coating.

[Object of the Invention]

The present invention eliminates the above drawbacks, by using a silicone rubber as an adhesive bonding material different from the conventional one, it is possible to work at room temperature, so the stress on the metal reflective film and the disk substrate is greatly reduced, It is an object of the present invention to provide a highly reliable double-sided reproducible bonded optical disc that can hold an input signal with high accuracy.

[Outline of Invention]

The present invention provides a bonded optical disk having a structure in which a metal reflective film is provided on the recording surface of an optical disk substrate having a recording surface on one side, and a pair of metal reflective films are made to face each other and bonded with a silicone rubber adhesive. It is a proposal.

Example of Invention

FIG. 1 is a sectional view of an optical disk after bonding according to the present invention, in which 1 is a disk substrate, 2 is a recording image, 3 is a metal reflection film, and 4 is a silicon rubber adhesive layer. In addition, a protective film may be further provided on the metal reflective film, but this is to prevent the metal reflective film from being directly distorted or scratched, and it is necessary to select a protective film that is also highly flexible. In conformity with this, the same as that used for the above-mentioned adhesive, that is, a silicone rubber-based material, which is preferable in that the temperature of the substrate does not rise when applying or bonding to the substrate, was found. As a method for forming the protective film on the substrate, a bar coater method, a screen printing method, a spinner method, or the like can be used to form a protective film on the reflective film by a conventional method.

Then, as shown in FIG. 2, the protective film 5 may be coated with the silicone rubber adhesive 4 in the same manner, and then the pair of optical disk substrates may be bonded together. As a silicone rubber adhesive, the self-shrinkage during curing is small so that the metal reflection film is not distorted, and it has excellent elasticity.
Liquid reaction type and room temperature curing type, for example, Toshiba Silicone
Examples include XE12-302 and TGS-701 manufactured by Co., Ltd. This two-component condensation type room temperature curing silicone rubber is
It is supplied separately in two components, a main body and a curing agent, and when both are mixed immediately before use, curing is promoted by moisture in the atmosphere to give a rubber-like elastic body.

In addition, in general, there are many materials that do not have adhesiveness, and therefore it is necessary to impart adhesiveness. The curing mechanism is a hydrolytic condensation reaction of silanol and a silicon compound containing a hydrolyzable group, and as the cross-linking agent, alkoxysilane is mainly used. At this time, water and a catalyst (tin compound, amines, etc.) are used.
The existence of is essential. Ethyl orthosilicate and its partial hydrolysis are used as alkoxysilanes, so the by-product during curing is tanol. Therefore,
There is little adverse effect on the disk substrate and the Al reflection film. The two-component condensation type is preferably a deep-curing type and is preferable because it does not expose an uncured portion. Further, the curing rate can be adjusted by the type and amount of the curing agent, which is convenient.

〔The invention's effect〕

Since the adhesive or protective film used in the optical disk of the present invention is a silicone rubber type, it can be formed into a flexible adhesive layer having extremely high elasticity after the adhesive effect, so that the metal reflective film of the optical disk substrate has a crease line. It is possible to easily provide a smooth optical disc with less warpage without the possibility of such things entering.

From the above, according to the present invention, it is possible to produce a high-quality, high-reliability optical disc with little dropout noise and high yield.

[Other Embodiments of the Invention]

Approximately 1000 Å of Al is vacuum-deposited as a reflective film on the recording surface of the optical disk substrate made by injection molding of acrylic resin, and the silicone rubber adhesive XE
12-302 (manufactured by Toshiba Silicone Co., Ltd.) was applied with a spinner to a thickness of about 10 μm to form a protective film / adhesive. The pair of layers were overlapped with the welding agent layers facing each other and sufficiently pressed by a pressing machine to bond them. It took about 8 hours at room temperature for complete curing. The bonded optical disk thus produced was smooth with less warpage and less dropout noise.

[Brief description of drawings]

1 and 2 are cross-sectional views of a bonded optical disc of the present invention. 1 ... Transparent substrate, 2 ... Recording surface, 3 ... Metal reflective film, 4 ... Silicon rubber adhesive layer, 5 ... Protective film.

Claims (2)

[Claims] 1. A structure in which a metal reflective film is provided on a recorded image of a disk substrate having a recording surface on one side, and a pair of the metal reflective films are opposed to each other and are bonded with a silicone rubber adhesive. Characteristic optical disc. 2. The optical disk according to claim 1, wherein the silicone rubber adhesive is a two-component condensation type room temperature curing type and self-adhesive.