JPS6192458A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve the adhesiveness to a substrate, more particularly plastic substrate and corrosion resistance by providing a film which does not contain oxygen in the film itself and consists of a boride having excellent moisture resistance on one or both sides of a recording layer. CONSTITUTION:The film consisting of the boride may be provided between at least an undercoating layer and optical recording layer and may be provided on both sides of the optical recording layer. Any among Mo-B, Nb-B, Ta-B, Ti-B, W-B, Zr-B, Cr-B and Si-B is used for the film consisting of the boride and the film thickness thereof is suitably 150-2,000Angstrom . The optical recording medium is obtd. by forming an undercoating layer 2 consisting of an SiO film on the substrate 1a on the writing side, providing successively a boride film 7, an optical recording layer 3, a spacer layer 4 and a reflecting layer 5 and providing further a protective layer 9 and adhering the laminate via an adhesive layer 6 to a substrate 1b for protection. The substrate 1a on the writing side which is transparent to used light is usable and glass and plastic such as acrylic resin are usable. Glass and plastic are used for the substrate 1b.

Description

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

[Conventional technology]

Conventionally, optical recording media used in optical disks include rare earth-transition metal alloy thin films, reducing oxide thin films such as chalcogen compounds that utilize phase transition from amorphous to crystalline, heat mode recording media, and thermostats. Plastic recording media and the like are known. For example, as a magneto-optical recording medium formed of a rare earth-transition metal alloy thin film, MtIB
i, polycrystalline thin films such as MnCuB1, GdCo,
GdFe, TbFe, DyFe.

GdTbFe, TbDyFe, GdFe, Co
Amorphous thin films such as , TbFeCo, and GdTbCo, and single crystal thin films such as GdIG 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 has recently been considered to be excellent for use in magneto-optical recording media. In particular, GdTbFe has a Curie temperature of about 150 to 200°C, and GdTbFeCo has a large Kerr rotation angle and excellent playback performance.
8-196639) etc. are most suitable for magneto-optical recording media.

[Problem that the invention seeks to solve]

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.

In order to eliminate such drawbacks, various protective layers such as SiO□ and Sin have been conventionally applied on the optical recording layer.

Disc-shaped recording media have been proposed that are provided with a protective layer of a transparent material such as Al2O2 or further sealed with an inert gas.

An example of such a conventional optical recording medium is shown in FIG. An undercoat layer 2 of Sin, 5in2 is formed on the writing side substrate 1a, and an optical recording layer 6, S, ? - Obtained by bonding to the protective substrate 1b via the protective layer 4, the reflective layer 5, and the adhesive layer 6.

However, even with this configuration, there is a problem that the recording layer is oxidized due to seepage of oxygen and moisture from the auxiliary layer such as the protective layer or the undercoat layer, resulting in deterioration of recording characteristics and failure to obtain sufficient corrosion resistance.

Further, when a film containing only a ferride is used as the undercoat layer 2, there is a drawback that the adhesion to the plastic substrate is weak and cracks are likely to occur.

Yes, -, -11+1 ゛--- The purpose is to provide excellent optical recording media.

[Failure to solve the problem]

The object of the invention is achieved by the following optical recording medium.

That is, the optical recording medium is characterized in that an undercoat layer made of SiO is provided adjacent to a substrate, and a boride film is provided at least between the undercoat layer and the optical recording layer.

The object of the present invention can be achieved if the sterilized film is provided at least between the undercoat layer and the optical recording layer, but it may also be provided on both sides C of the optical recording layer.

The above-mentioned poride film is composed of M □ -B system, Nb-B system, T
a-B system, Ti-B system, V-B system, W-B system, Zr B
system, Ca-B system, Hf-B system, Cr-B system, Si-B
The film thickness of the hydride used in the system is preferably 150X to 2000X. If it is thinner than 1soX, sufficient protection cannot be obtained;
If it is thicker than 0A, the recording sensitivity will decrease and cracks will occur, which is not preferable. An embodiment of the optical recording medium of the present invention is shown in FIG.

The optical recording medium shown in FIG.
A subbing layer 2 of an iO film is formed, and a poride film 7,
The optical recording layer 6, the sintering layer 4, and the reflective layer 5 are provided, and the protective layer 9 is further provided by bonding the protective layer 1b to the protective substrate 1b via the adhesive layer 6.

As the write-side substrate 1a, various amorphous magnetic thin films can be used, for example, as an optical recording layer having an angle of 1° with respect to the light used. As this amorphous magnetic thin film, GdCo
, GdFe, TbFe, DyFe, GdTbFe.

An amorphous magnetic thin film such as TbDyFe is preferred. Among them, Gd Tb Fe and Gd Tb Fe Co are particularly preferable because they have a large Kerr rotation angle.

The layer thickness of the amorphous magnetic thin film is formed to a desired layer thickness within the range that functions as a recording layer, but is usually 160 to 10,000 mm.
That's about it. In order to improve the recording/reproducing sensitivity, it is desirable that the current be about 160A.

A silicon oxide film such as 5IOISiO2, a nitride film such as AlN, Si, or N4, a carbide film such as SiC, or a boride film such as the one of the present invention can be used as the single layer of the layer 4. The thickness of the single layer is 500~
3000A is suitable.

As the reflective layer 5, Al or Cu can be used. A film thickness of 400 to 1000A is suitable.

As the protective layer 9, a material such as Sin, 5i02, etc. can be used, and its film thickness is suitably 500 to 2000 mm).
As the adhesive layer, a silicone adhesive such as 5E1700 manufactured by Toshi Silicone ■ is used with a thickness of about 10 μm.

As the protective substrate 1b, glass, plastic, etc. are used.

A reflective layer, a protective layer, an adhesive layer, and a protective substrate may or may not be provided as necessary.

Other auxiliary layers may also be provided.

Although FIG. 1 shows an optical recording medium having a laminated structure, it may also have an air sandwich structure in which an inert gas is sealed.

〔Example〕

EXAMPLES In order to explain the present invention more specifically, Examples are shown below.

Example 1 A magneto-optical recording medium having the structure shown in FIG. 1 was manufactured as follows. A 1000A SiO film was formed as an undercoat layer 2 on a 7° plastic substrate 1a made of acrylic material and having a thickness of 1.2 mm. A B, Si film of 500 Å was formed as the fertilized film 7 by sputtering. On top of that, I
) A GdTbFeCo film was formed to a thickness of 200 Å 9 to form a recording layer 6 made of a magnetic film. Furthermore, an SiO film of approximately 70 OA was deposited as the thermal layer 4, an A7 film of approximately 500 Å was deposited as the reflective layer 5, an SiO film of 2,000 Å was deposited as the protective layer 9, and a silicon adhesive (Toshiba) was deposited as the adhesive layer 6. Silicone (made by ■: 5E1700) was screen printed to a thickness of 10 mm and bonded to a protective plastic substrate 1b to form a magneto-optical recording medium.

The obtained recording medium was subjected to a 500-hour humidity test in a constant temperature and humidity chamber at a temperature of 45° C. and a relative humidity of 95 degrees, in addition to measuring the coercive force Hc at the Kerr rotation angle θ.

For comparison, a recording medium having the same structure except that the protective layer 7 was not provided was manufactured in the same manner and tested at the same time.

The results are shown in Table 1, and the magneto-optical recording medium of the present invention showed no deterioration in magnetic properties and improved durability.

Example 2 In Example 10B, a CrB2 film was provided as the protective layer 2 instead of the Si film, and a 200A CrB2 film was provided as the protective layer 8 between the recording layer 6 and the silicon layer 4. 2
A medium having the configuration shown in the figure was prepared.

As in Example 1, in addition to measuring the Kerr rotation angle θk and coercive force IC, a 500-hour humidity test was conducted in a constant temperature and humidity chamber at a temperature of 45° C. and a relative humidity of 95 degrees.

The results are shown in Table 1, indicating that durability could be improved. In addition, the numerical values in Table 1 are shown as ratios when the initial value is 1.0.

Table 1 [Effects of the Invention] In the optical recording medium of the present invention, even if the recording layer is a magnetic layer with a thickness of about several hundred amps, a moisture-resistant film that does not contain oxygen in the film itself is coated on one or both sides. By providing an excellent boride film, it is possible to provide an optical recording medium with excellent adhesion to a substrate, especially a plastic substrate, and excellent corrosion resistance.

Note that the present invention is not limited to magneto-optical recording media Vζ, and is equally effective in improving the durability of other optical recording media having recording layers that are easily oxidized, such as thin films of chalcogen compounds. Some 0

[Brief explanation of drawings]

1 and 2 are schematic cross-sectional views of the optical recording medium of the present invention, and FIG. 6 is a schematic cross-sectional view of a conventional optical recording medium. 1a...Writing side substrate 1b...Protective substrate 2...Undercoat layer 6...Optical recording layer 4 ......S-s-+-1n 5......Reflection layer 6...Adhesive layer 7.8...Moulide Film 9...Protective layer

Claims (1)

[Claims] An undercoat layer made of SiO is provided adjacent to the substrate,
An optical recording medium comprising a boride film at least between the undercoat layer and the optical recording layer.