JPS60191449A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a recording medium without spoiling its characteristics by forming a boron nitride film on one or both sides of an optical recording layer. CONSTITUTION:A boron nitride film 7 is formed on a write-side substrate 1a, and a recording layer 3, boron nitride film 8, and reflecting film 5 are provided and stuck on an external substrate 1b through an adhesive layer 6. The write- side substrate and external substrate may use any materials such as glass and plastic, and when a plastic substrate is used, this invention is effective because moisture hardly enters it. The boron nitride film is provided preferably to both sides of the recording layer, but may be formed only on one side. The fil thickness of the boron nitride film is preferably 500-3,000Angstrom ; dump resistance effect is insufficient below 500Angstrom and evil influence is exerted upon the magnetic characteristics of the recording layer above 3,000Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording medium on which recording and reproduction can be performed using a light beam.

Conventionally, optical recording media used in optical disks include thin films of rare earth-transition metal alloys, thin films of cyclic oxides such as chalcogen compounds that utilize phase transition from amorphous to crystalline, and heat mode recording media. , thermoplastic recording media, etc. are known. For example, as a magneto-optical recording medium formed of a rare earth-transition metal alloy thin film, MnB
1. Polycrystalline thin films such as MnCuB1, Ga, Co,
GaFe, TbFe, DyFe.

Amorphous thin films such as GaTbFe, 'TbDyFe,
Single crystal thin films such as GaIG are known.

Among these thin films, the film-forming properties of large-area thin films at temperatures near room temperature, the writing efficiency of writing signals with small photothermal energy, and the ability of reading written signals with a good S/N ratio are important. In consideration of read efficiency and the like, the amorphous thin film is recently considered to be excellent as a photothermal recording medium. Gd and TbFe have a sharp Kerr rotation angle and a single Curie point around 150°C, so they are suitable as photothermal magnetic recording media. Furthermore, as a result of research aimed at improving the Kerr rotation angle, the inventors found that GdTbFs
It has been found that Co is a magneto-optical recording medium that has a sufficiently large Kerr rotation angle and allows readout with a good S/N ratio.

However, amorphous magnetic materials used in magnetic recording media, including magneto-optical recording media such as GdTbFe, generally have a drawback of poor corrosion resistance. That is, when it comes into contact with air or water vapor, its magnetic properties deteriorate, and eventually it becomes completely oxidized and becomes transparent. Further, this problem is common not only to magneto-optical recording media but also to the optical recording media mentioned above.

In order to eliminate such drawbacks, a protective cover made of, for example, a transparent material, such as 8j02, is conventionally provided on the recording layer.
Disc-shaped recording media provided with a protective layer of SiO or further sealed with an inert gas have been proposed. Also,
As shown in FIG.
, a recording magnetic layer 3, a spacer layer 4. By providing a reflective layer 5 and bonding it to an external substrate 1b via an adhesive layer 6, an optical recording medium was formed.

However, even with the table structure described above, in practice,
It was difficult to obtain sufficient corrosion resistance. For example, even in the optical recording medium shown in Figure 1, several hundred layers of the recording layer may be damaged by moisture that has entered through the write-side substrate or the external substrate (substrates made of plastic have a strong water-absorbing property, so this tendency is strong). In some cases, such as a thin magnetic film, if it is left in a humid environment for a long period of time, problems can arise if the magnetic properties deteriorate.

An object of the present invention is to provide an optical recording medium that has improved corrosion resistance without impairing its characteristics as a recording medium.

The above object of the present invention is achieved by forming a boronitride film on one or both sides of the optical recording layer in an optical recording medium comprising an optical recording layer provided on a substrate.

In a preferred embodiment of the optical recording medium of the present invention, as shown in FIG. 2, a boron nitride film 7 is formed on a writing side substrate la, and a recording layer 8 . Nitride nitride film 8. and a reflective layer 5 are provided, and an external substrate 1 is further provided via an adhesive layer 6.
Obtained by bonding with b. Next, as shown in FIG. 3, an undercoat layer 2 is formed on the writing side substrate la, and a boron nitride film 9 is sequentially formed. Recording layer 8. A nitride nitride film 10, a spacer layer, and a reflective layer 5 may be provided, and further bonded to the external substrate 1b via an adhesive layer 6.

The present invention can be applied to any material such as glass or plastic used for the write-side substrate and external substrate, but if a plastic substrate is used, moisture can easily enter. The present invention is particularly effective. Although it is preferable that the nitride film is provided on both sides of the recording layer as in the example shown in the second figure, it may be formed only on one side of the structure. For example, in the case of a bonded structure in which one substrate is made of glass and the other is made of plastic, an application example may be in which a boron nitride film is formed only on the plastic substrate side. Furthermore, the present invention is not limited to the various bonded structures described above, but is also effective for optical recording media of a type in which a recording layer or the like is simply laminated on a substrate.

A range of 500A to 3000A is preferred. If it is thinner than 500A, the moisture resistance effect will be insufficient, while if it is thicker than 3000A, it will affect the magnetic properties of the recording layer, which is not preferable.

According to the optical recording medium of the present invention, even if the recording layer is a magnetic layer with a thickness of about several hundred, a boronitride film with excellent moisture resistance can be provided on one or both sides. As a result, we were able to improve durability even in constant temperature and humidity tests.

The present invention will be further explained below by showing an example in which the present invention is applied to a magneto-optical recording medium.

Example 1 In FIG. 2, an acrylic resin material is used as the substrate 1a, a nitride nitride film 7 is formed on it to a thickness of about 100 OA, and a quaternary amorphous magnetic film of about 20 OA is formed as the recording layer 3. Using a thin film, a boronitride film 8 is similarly formed thereon, and an external substrate 1b made of an acrylic resin material is bonded using A and J films as the reflective layer 5 and a silicon adhesive as the adhesive layer 6. A magneto-optical recording medium was obtained. No change was observed in the rotation angle θ from the obtained magneto-optical recording medium, nor in the coercive force Hc due to the addition of boron nitride, under the conditions of 45°0 relative humidity 95 degrees and a standing time of 200 hours. As a result of the moisture resistance test, no deterioration of magnetic properties was observed, and durability was improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the structure of a conventional optical recording medium. FIG. 2 is a schematic diagram for explaining the configuration of one embodiment of the optical recording medium of the present invention. FIG. 8 is a schematic diagram for explaining the structure of another embodiment of the optical recording medium of the present invention. ]-a...Writing side substrate]-1]...External substrate 2...Undercoat layer 8...Recording layer 4,...Spacer layer 5...Reflection layer 6...Adhesive layer 7, 8.9.10...Nitride oxide membrane patent applicant Canon Co., Ltd. 7- o e C5, J Co.

Claims (1)

[Claims] 1. An optical recording medium comprising an optical recording layer provided on a substrate, characterized in that a boronitride film is formed on one or both sides of the optical recording layer.