JPS61168146A - Information recording medium - Google Patents

Abstract

PURPOSE:To prevent the oxidation of a recording layer resulting from air and a substrate and to obtain the title medium capable of being used for a long period by providing a silicon carbide layer to protect the recording layer formed on the substrate. CONSTITUTION:Although a recording layer 2 of Te or a chalcogenide material contg. Te is provided on a substrate 1 consisting of glass, etc., antioxidant layers 3a and 3b using a silicon carbide film are formed in the form of a film on the upper and the lower surface of the recording layer 2. To produce the information recording medium, Si is sputtered on the substrate 1 in a methane atmosphere by using Si as a target to form the film of the silicon carbide layer 3a, and the recording layer 2 is laminated on the layer 3a by sputtering Te from the target of the Te. Furthermore, the film of the silicon carbide layer 3b is likewise formed on the recording layer 2. At this time, the film thickness of the silicon carbide layers 3a and 3b is regulated to 1000Angstrom , and the film thickness of the recording layer 2 is controlled to 500Angstrom . Accordingly, the silicon carbide layers 3a and 3b act extremely efficiently as the antioxidant layer even in the deterioration test at high temps. and humidity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in the layer structure of an information recording medium capable of recording, reproducing and erasing information, for example in an optical disk memory.

[Technical background of the invention and its problems]

In recent years, as the amount of information has increased, media have been developed that can record and reproduce information at high density. One of the methods for recording information on media in this building is a method that utilizes changes in the optical properties (absorption, reflection, transmission) of the recording material due to energy such as laser light or short pulses of xenon light. This method has (1) high recording surface density and low memory cost per bit; ).

(2) High-speed access is possible. (3) The recording medium has good storage stability. It has the following advantages. Until now, these recording materials have been either metals (tungsten, chromium, nickel, etc.) or semimetals (810°8i 0.
Inorganic thin films such as those made of silicon-based materials (e.g., silicon-based materials) and organic thin films made of polymers containing dyes, etc., are known.

In addition, as a recording method, a method is used in which a recording medium is melted and evaporated by the heat of a laser beam to form minute holes (bits), and the change in reflectance of the bits is read. This method has the disadvantage that recorded pit information cannot be erased.

In response, progress is being made in the development of rewritable information recording media that utilize a change in reflectance due to a phase change between crystal and amorphous due to laser beam irradiation, as seen in chalcogenide materials.

Such a rewritable recording layer is made of Te or Te.
Chalcogenide materials mainly composed of are widely used. Te-based materials (11 have a low melting point, - and +21 have low transmission coefficients, and (3) have large light absorption at the wavelength of laser light.

On the other hand, it has the disadvantage that it is easily oxidized in the atmosphere and becomes an oxide. The Te oxide film does not undergo a change in optical density even when the phase changes from crystal to amorphous or from amorphous to crystal due to light irradiation.
Information cannot be recorded. Therefore, increasing the oxidation resistance of the recording layer is an important point for putting this type of recording medium into practical use. Therefore, attempts have been made to prevent oxidation by laminating various materials on this recording layer. Other gold layer thin films (N1°Cr
, W) and organic thin films are used on soil.

However, these gold layer thin films have drawbacks such as poor adhesion to recording layers such as Te (and poor mechanical strength and easy surface scratches).

On the other hand, in the case of an organic thin film, the heat resistance is poor, so there is a possibility that the film may be deformed or pores may be formed due to heat during information recording.

Silicon oxide (Sin, 5in2, etc.) is used to compensate for the drawbacks of such anti-oxidation layers of metal thin films and organic thin films. This silicon oxide film has the advantages of excellent heat resistance, is hard to scratch, and is dense, making it suitable as a protective layer.However, on the other hand, it has hygroscopic properties, so its strength is weak compared to silicon oxide films, and it can be used for resins, etc. It has the disadvantage that it is necessary to form a covering layer.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and by using a material with higher oxidation resistance than conventional ones as an oxidation-preventing layer, it can prevent oxidation from the air and from the substrate, and can withstand long-term use. The purpose is to provide recording media.

[Summary of the invention]

In order to achieve the above object, the present invention prevents oxidation by attaching to the recording layer a silicon carbide film in which oxygen is replaced with carbon, which has a greater anti-oxidation effect than the conventionally used silicon oxide film. It is characterized by this.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on one embodiment shown on page 1. In the figure, (1) is acrylic, polycarbonate,
Substrate made of material such as glass, (2) is Te or T
(3a) a recording layer of chalcogenide material containing e.

(3b) is an anti-oxidation layer using a silicon carbide film formed on the upper and lower surfaces of the recording layer (2).

Next, a method for producing an information recording medium according to the present invention will be explained. First, a silicon carbide layer (3a) is formed on the substrate (1) by sputtering using silicon as a target in a methane atmosphere. Next, the silicon carbide layer (
3a) Recordings 11+21 are laminated on top by sputtering using Te as a target.

Finally, the silicon carbide layer (3b) is laminated on the recording N (21) in the same manner as the beginning. At this time,
The thickness of the silicon carbide layers (3a) and (3b) for preventing oxidation is approximately 100 OA on both the upper and lower parts of the recording layer (2),
The film thickness of 2) is 500A. It also targets silicon.

As a result of repeated recording and erasing using a recording medium created in this way, it was confirmed that the intended purpose was achieved, and the recording medium was further subjected to a deterioration test at high temperatures. As a result, it was proved that the silicon carbide film has an extremely significant effect as an anti-oxidation layer.

Note that in the above embodiment, a silicon carbide film is placed on the recording layer.

Although the silicon carbide film is laminated on the top and bottom of the recording layer, it is not necessarily limited to this, and by laminating the silicon carbide film only on the top of the recording layer, some oxidation may occur on the substrate side, but it is not practical. There is no problem with the above.

〔Effect of the invention〕

As explained above, according to the present invention, the silicon carbide film formed on one or both sides of the recording layer is chemically more stable than conventional silicon oxide films, and has a greater blocking effect against moisture and alkali ions. It also has the advantage of excellent mechanical strength. In addition, since it has better adhesion with the recording layer than a silicon oxide film, there is no phenomenon of cracks occurring, and furthermore, by preventing the evaporation of the recording layer, it changes from crystalline to amorphous, or from amorphous to amorphous. It is possible to widen the phase change region of the crystal and reduce the pressure during recording and erasing. In addition, because of its low thermal conductivity, it has other effects such as preventing heat diffusion and narrowing the spot diameter, and has excellent properties as an oxidation-preventing layer of a recording layer.

[Brief explanation of drawings]

The drawing is a layer configuration diagram of an information recording medium showing an embodiment of the present invention. ■...Substrate 2...Recording layer 3a, 3
b...silicon carbide layer) Z plane

Claims (4)

[Claims] (1) An information recording medium in which information is recorded using focused light, including a substrate, a recording layer formed on the substrate, and a silicon carbide layer provided to protect the recording layer. Characteristic information recording media. (2) The information recording medium according to claim 1, wherein the recording layer is formed of Te or chalcogenide containing Te. (3) The information recording medium according to claim 1, wherein the silicon carbide layer is formed only on the upper part of the recording layer. (4) The information recording medium according to claim 1, wherein the silicon carbide layer is formed above the recording layer and between the recording layer and the substrate.