JPH0827977B2 - Write / erase type optical disk - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a write / erase type optical disc that performs writing (recording / reproducing) and recording / erasing using a laser beam,
Used for recording and recording.

2. Description of the Related Art In an optical disc for recording / reproducing using laser light, laser light is transmitted through a transparent substrate and is applied to a recording film formed in a recording groove on its back surface to cause a phase change due to energy of the laser light in the recording film. , A sound or image signal is recorded as a difference in reflectance due to the phase change, and is reproduced as a sound or image signal. Further, the original reflectance can be restored by changing the method of applying laser energy. The recording film is formed by vapor deposition or sputtering. Recording and erasing are performed by irradiating a recording film with a laser beam to cause a phase change to restore the reflectance and make it amorphous. As shown in Nikkei Electronics 1985, 3.25, there is a magneto-optical disk that uses the Kerr effect with a different recording method.

Conventionally, a glass substrate is mainly used as the transparent substrate, and a thermoplastic type polymethylmethacrylate (hereinafter abbreviated as PMMA) substrate or a polycarbonate (hereinafter abbreviated as PC) substrate is used as the resin substrate. There is.

Problems to be Solved by the Invention PMMA substrates and PC substrates, which are the conventional resin substrates, can be produced by an injection molding machine and have good productivity, but are not excellent in heat resistance and are suitable for write / erase type optical discs. It was inconvenient. That is, if recording, reproduction, and erasing are repeatedly performed on the recording film formed on the PC substrate by laser light, the recording film has holes due to thermal deformation of the PC substrate several times to several tens of times. . This is also the case with the PMMA substrate, and the quality cannot be guaranteed as a write / erase type optical disc, and it is used only as a single write type optical disc.

The inventors conducted computer analysis to obtain a heat resistance target around the recording film.
It was found that the temperature was ℃ or more. In addition, Kashihara et al. Matsushita Electric Industrial Co., Ltd. have published in the Optical Memory Symposium '85.

To cope with this, a method of forming an appropriate inorganic heat insulating film under the recording film is also conceivable, but there are problems and equipment for optimizing the equipment, method, materials, etc. for forming the inorganic film on the PC substrate. Since the cost is high, the present situation is that the reduction of the optical disk cost has not been put to practical use due to a problem.

Means for Solving the Problems In order to achieve the above object, the present invention provides a recording film which undergoes a phase change (crystalline or amorphous) by a laser beam applied through the transparent substrate to a recording groove on the back surface of the transparent substrate. Formed,
In the optical disc having a recording film covered with a protective layer, the transparent substrate is a cross-linking reaction-curable heat-resistant substrate. Preferably, the cross-linking reaction curable material is a heat resistant substrate in which the main chain molecule is a molecule having a tricyclo ring. Further, preferably, the protective layer is formed by adhering a groove-free heat-resistant substrate, and preferably a heat-resistant substrate in which a molecule having a tricyclo ring is cross-linked with a bifunctional acrylate or a bifunctional diacrylate, More preferably, the transparent substrate, which is a cross-linking-curable heat-resistant substrate, has a glass transition temperature of 150 ° C. or higher and a water absorption rate of 60 ° C., 90% RH is 1.5% or less at the saturation point.

Incidentally, a heat insulating inorganic film of ZnS or SiO _{2 having} a thickness of 400 Å or less may be formed on the upper or lower surface or one surface of the recording film and used.

Action The transparent substrate cross-linked under each of the above conditions prevents the recording film or the laser spot resin portion from being thermally deformed by the laser light energy during writing / erasing, and prevents the recording film from being destroyed. You can

EXAMPLE An example of the present invention shown in FIGS. 1, 2, and 3 will be described. A recording film 4 is formed on the back surface of a heat-resistant transparent substrate having a recording groove 6 and a track groove 7, and is formed thereon. A heat-resistant substrate 2 serving as a protective layer is adhered to the substrate with an adhesive 5. The heat-resistant transparent substrate 1 is composed of a nickel stamper adhered to a glass plate for recording grooves 6 and track grooves 7 on one side and a space between the glass plate and the silicone rubber spacer, and a monomer having the molecular structure shown in Table 1 and a thermal initiator. (Benzoyl peroxide (BP
O)) and its liquid compounding composition No. 1 are poured and heated to 80 ° C for primary curing, then demolded and post-cured at 80 ° C for 2 hours and 150 ° C for 1.5 hours to cure by crosslinking reaction. It is of a type. The heat-resistant substrate 2 is a glass plate made of a nickel stamper under the same conditions as the heat-resistant transparent substrate 1.
The heat resistant substrate 2 having a flat surface on both sides is formed. Recording film 4
Is a recording material mainly composed of tellurium oxide formed on the heat-resistant substrate 1 having a groove by sputtering with a thickness of about 400 liters. The heat-resistant transparent substrate 1 and epoxy have a better write / erase cycle life. Further, it can be seen that the substrate of the special methacrylate composition of the present invention shows further excellent long-life property, and No. 2 is the best (temporarily the current write / erase cycle is 10 ⁵ or more). . That is, it was more preferable that the glass transition temperature was 200 ° C. or higher.

EFFECTS OF THE INVENTION By using the cross-linking reaction-curable heat-resistant transparent substrate of the present invention, heat resistance sufficient to prevent the recording film from being perforated can be obtained, and a heat insulating inorganic film of several hundred Å to 1000 Å is formed There was no need for equipment costs because the manufacturing process was unnecessary. In particular, not the optical gap layer but the heat insulating film on the substrate side is unnecessary.
There is great industrial value in that an optical disk can be produced at low cost.

[Brief description of drawings]

FIG. 1 is a plan view of a half portion showing an embodiment of the present invention, FIG. 2 is a cross sectional front view, FIG. 3 is an enlarged sectional view of the same portion, and FIG. 4 is an embodiment of the present invention and a comparative example. FIG. 1 ... Transparent substrate, 2 ... Protective layer, 3 ... Recording film and adhesive layer, 4 ... Recording film, 5 ... Adhesive layer, 6 ... Recording groove, 7 ...
… Track grooves.

Claims (1)

[Claims] 1. An optical disc in which a recording film which undergoes a phase change by a laser beam applied through the transparent substrate is formed on at least the back surface of the transparent substrate, and the recording film is covered with a protective layer. Is a heat-resistant substrate obtained by crosslinking and curing a compound having at least a tricyclo ring, wherein the functional group of the compound having a tricyclo ring is 2
A write / erase type optical disc, which is a functional group and is diacrylate or dimethacrylate.