JPH04219650A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain optical recording medium excellent in durability by providing under coating layer consisting of silicon oxide and contact with substrate between substrate and recording layer and consisting of mixture of carbide and nitride between this under coated layer and recording layer. CONSTITUTION:The under coated layer 2 and magnetic recording layer 3 are provided under a plastic substrate 1a of writing in side. The under coated layer 2 is formed with SiO or SiO2 having 500-3000Angstrom thickness and magnetic recording layer 3 is formed by 160-1000Angstrom thickness of Gd-Tb-Fe, Gd-Tb-Fe-Co. Between the undercoat layer 2 and the recording layer 3, protective layer 7, 8 having 100-2000Angstrom thickness consisting of mixture of carbide and nitride is provided and preventing corrosion of the magnetic recording layer 3 by moisture through the substrate 1 and oxygen from the undercoat layer 2. Additionally, spacer layer consist of SiO, SiO2, etc., reflectance layer 5 consisting of Cu, Al, Au, etc., and adhesion layer 6 of silicone base, etc., and protective substrate 1b consisting of glass and Al are also provided and constituted this medium body.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides recording and recording using a light beam.
The present invention relates to an optical recording medium that can be reproduced.

0002

[Prior Art] Conventionally, optical recording media used in optical discs include thin films of rare earth-transition metal alloys, thin films of reducing oxides such as chalcogen compounds that utilize phase transition from amorphous to crystalline, Heat mode recording media, thermoplastic recording media, etc. are known. For example, magneto-optical recording media formed of rare earth-transition metal alloy thin films include polycrystalline thin films such as MnBi and MnCuBi, GdCo, GdFe, TbFe, DyFe,
Amorphous thin films such as GdTbFe and TbDyFe, T
Single crystal thin films such as bFeO3 are known.

[0003] Among these thin films, the film forming performance when manufacturing a large-area thin film at a temperature near room temperature, the writing efficiency for writing signals with small photothermal energy, and the good S/N ratio of written signals are important. Considering readout efficiency and the like, the amorphous thin film is recently considered to be excellent as a photothermal recording medium. GdTbFe
has a large Kerr rotation angle and a Curie point of around 150°C, making it suitable as a photothermal magnetic recording medium. Furthermore, as a result of research aimed at improving the Kerr rotation angle, the inventors found that G
It has been found that dTbFeCo is a magneto-optical recording medium that has a sufficiently large Kerr rotation angle and can be read with a good S/N ratio.

0004

[Problems to be Solved by the Invention] 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.

[0005] In order to eliminate such drawbacks, conventionally,
For example, SiO2, SiO, Si3N4,
Disk-shaped recording media have been proposed in which a protective layer of AlN is provided or a magnetic recording layer is further sealed with an inert gas.

As an example of such a conventional magnetic recording medium, for example, as shown in FIG. 2, a protective layer 2 is formed on a writing side substrate 1a, and a magnetic recording layer 3, a spacer layer 4, and a reflective layer 5 are sequentially formed. It is known that the substrate is further bonded to an external plastic substrate 1b via an adhesive layer 6. However, if the magnetic recording layer 3 is as thin as several hundred angstroms due to the high water absorption of the plastic substrate, the magnetic recording layer 3 will become magnetic if left in a humid state for a long time despite the presence of the protective layer 2 and spacer layer 4. The disadvantage was that the characteristics deteriorated easily. In addition, the nitride film used as a protective layer has weak adhesion to substrates such as plastic.
It has the disadvantage of being prone to peeling and cracking. Furthermore, if a material with good thermal conductivity such as Si3N4, AlN, or BN is used as a nitride and the film thickness is increased to improve the durability of the recording medium, the temperature of the recording layer due to the light beam may not rise sufficiently, resulting in a decrease in recording sensitivity. There was also the drawback that it decreased.

The present invention has been made in view of the above problems, and provides a magnetic recording medium that has excellent corrosion resistance against moisture, oxygen, etc., and excellent durability without impairing the magnetic properties of the magnetic recording layer. , and to improve its recording sensitivity.

[0008]

[Means for Solving the Problems] The above-mentioned object of the present invention is to provide an optical recording medium comprising an optical recording layer provided on a plastic substrate. This is achieved by providing an undercoat layer made of silicon oxide and further providing a protective layer made of a mixture of carbide and nitride between the undercoat layer and the recording layer.

[0009] Examples of the above-mentioned carbide include Ti-C type,
Zr-C system, Hf-C system, V-C system, Ta-C system, M
o-C system, W-C system, Si-C system, B-C system, Cr
-C system, Al-C system, Ba-C system, Be-C system, Ce-
C system is used. Further, as the nitride, for example, Sn
-N system, In-N system, Zr-N system, Cr-N system, Al-
N system, Si-N system, Ta-N system, V-N system, Nb-N
type, Mo-N type, and W-N type.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, when the present invention is applied to a magneto-optical recording medium, an example of the structure of each layer of the recording medium will be described with reference to a schematic diagram showing a cross section thereof.

In the recording medium having the structure shown in FIG. 1, the write-side substrate 1a, the undercoat layer 2, and the magnetic recording layer 3 can be formed of the same material as used in the conventional magnetic recording medium shown in FIG. For example, the substrate 1a may be a plastic plate such as acrylic resin or polycarbonate, or a glass plate, and the undercoat layer 2 may be SiO or SiO2.
Various amorphous thin films can be used as the magnetic recording layer 3. As this amorphous magnetic thin film, GdCo,
GdFe, TbFe, DyFe, GdTbFe,
An amorphous magnetic thin film such as TbDyFe is preferred. Among these, GdTbFe and GdTbFeCo are particularly preferable because they have a large Kerr rotation angle.

[0012] The layer thickness of the undercoat layer 2 is generally 500 to 300
Although it varies depending on the layer thickness of the magnetic recording layer 3 and the layer thickness of the film 7 made of a mixture of carbide and nitride, it is preferably about 1000 angstrom from the viewpoint of durability and recording sensitivity. SiO 2 or SiO 2 provided as an undercoat layer is provided for the purpose of improving the compatibility of the film provided thereon with the substrate.

The thickness of the magnetic recording layer 3 is formed to a desired thickness within a range that functions as a recording layer, but is usually 160 to 1.
000 angstroms. However, from the viewpoint of improving recording and reproducing performance, the thickness is preferably about 160 angstroms.

a membrane 7 consisting of a mixture of carbides and nitrides;
8 is formed on both sides or one side of the recording layer 3. In the case of one side, it is formed between the undercoat layer 2 and the magnetic recording layer 3. Since the film made of a mixture of carbide and nitride does not contain oxygen, it functions to prevent the magnetic recording layer 3 from being corroded by oxygen from the undercoat layer 2 or moisture passing through the substrate. The thickness of the film made of a mixture of carbide and nitride is 100~2
A range of 0.000 angstroms is preferred. If it is thinner than 100 angstroms, the moisture resistance effect will be insufficient, while if it is thicker than 2000 angstroms, the recording sensitivity of the magnetic recording medium will decrease, which is undesirable.

The spacer layer 4 made of SiO, SiO2, etc., the reflective layer 5 made of Cu, Al, Au, etc., the adhesive layer 6 made of silicon adhesive, and the protective substrate 1b made of glass, plastic, or metal such as aluminum each play a role. The functionality is similar to that of conventional recording media.

In the example shown in FIG. 1, the film made of a mixture of carbide and nitride is provided adjacent to the recording layer, and although this case is more effective in terms of corrosion resistance, it is not true that the film is provided adjacent to the recording layer. Although not essential to the invention, the object of the invention can be achieved even if another auxiliary layer is interposed between the recording layer and the film made of a mixture of carbide and nitride. Further, as shown in another example in FIG. 3, a recording medium having a structure lacking auxiliary layers such as a spacer layer 4 and a reflective layer 5 also belongs to the present invention.

Referring to the example of FIG. 1, the method for manufacturing a recording medium of the present invention includes forming an undercoat layer 2 on a writing side substrate 1a.
A film 7 made of a mixture of carbide and nitride, a recording layer 3, and a film 8 again made of a mixture of carbide and nitride are sequentially formed by sputtering or the like. Further, a spacer layer 4 and a reflective layer 5 are laminated thereon by a vapor deposition method, and then the protective substrate 1b is laminated with an adhesive layer 6.
A recording medium having the configuration shown in FIG. 1 is completed by pasting the two layers together via the . Although not shown in FIG. 1, a protective layer such as a nitride film may be further interposed on the reflective layer 5 by sputtering or the like for the purpose of improving durability.

[0018] The present invention will be described in more detail below with reference to examples in which the present invention is applied to a magneto-optical recording medium.

Example 1 A SiO2 film of about 1000 angstroms is formed by vapor deposition as an undercoat layer 2 on a polyacrylate resin substrate 1a, and a mixed film 7 of Si3N4 and SiC of about 700 angstroms is formed by reactive sputtering.
Approximately 1000 angstroms by sputtering
GdTbFeCo quaternary amorphous thin film 3 was sputtered again to about 2000 angstroms of S.
Mixed films 8 of i3N4 and SiC were successively formed thereon. Further, a polyacrylate resin substrate 1b was attached via an adhesive layer 6 made of silicone adhesive to obtain a magneto-optical recording medium having the configuration shown in FIG. 3. The mixed films 7 and 8 of nitride and carbide are formed using a Si target and Ar
It was obtained by reactive sputtering in a mixed gas of CH4 and N2 at a gas introduction ratio of 90:5:5.

Regarding the obtained recording medium, its Kerr rotation angle θk and coercive force Hc were measured, and a humidity resistance test was conducted for 1000 hours in a constant temperature and humidity chamber at 45° C. and relative humidity of 95%.

For comparison, a test was also conducted on a recording medium having the same structure as above, except that the films 7 and 8 made of a mixture of carbide and nitride were not provided. 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. Furthermore, no deterioration in magnetic properties, recording sensitivity, or read efficiency was observed. Note that the values after the moisture resistance test in Table 1 are shown as ratios when the initial value is 1.0.

Example 2 A magneto-optical recording medium with the same film structure as in Example 1 was created except that a mixed film of SiC and AlN was provided as a protective layer instead of the mixed film of SiC and Si3N4 in Example 1. did. The mixed film of SiC and AlN is 5 inch φ SiC
Four Al pieces approximately 10 mm square were uniformly arranged on a compound target, and a film was formed by sputtering in a mixed gas of Ar and N2 at a ratio of 1:1.

[0023] This recording medium was also subjected to the same test as in Example 1, and the durability was improved as in Example 1. The durability results of Example 2 are shown in Table 1.

[0024]

[Table 1]
Table 1 ┌────┬──────┬
────────────┐ │
│Initial characteristics │ After 1000 hours of humidity test │ │ ├──┬─
─┼─────┬──────┤ │
│Hc │θk │Hc │
θk │ ├────┼─
─┼──┼──────┼──────┤
│Example 1│1.0 │1.0 │0.9
│ 0.9-1.0 │ │Example 2
│1.0 │1.0 │ 0.9 │ 0.
9-1.0 │ │Comparative example │1.0
│1.0 │ 0.2-0.3 │ 0.2-0.3
│ └────┴──┴──┴────
──┴─────┘

[0025]

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 angstroms, the film itself does not contain oxygen on the writing side substrate side or both sides thereof. By providing a film made of a mixture of carbide and nitride with excellent moisture resistance, the corrosion resistance of the recording medium can be significantly improved. The effect is particularly excellent when a film made of the mixture of carbide and nitride is provided in contact with the recording layer. Furthermore, by providing a film of SiO or SiO2 as an undercoat layer on the write-side substrate, it is possible to improve the compatibility of the film provided thereon with the substrate.

The present invention is not limited to magneto-optical recording media, but is equally effective in improving the corrosion resistance of other optical recording media having recording layers that are easily oxidized, such as thin films of chalcogen compounds. be.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an example of the structure of each layer of a recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view of an example of the structure of each layer of a conventional recording medium.

FIG. 3 is a schematic cross-sectional view of an example of the structure of each layer of the recording medium of the present invention.

[Explanation of symbols]

1a Write side board 1b Protective board 2 Undercoat layer 3 Recording layer 4 Spacer layer 5 Reflective layer 6 Adhesive layer

Claims (1)

[Claims] 1. An optical recording medium comprising an optical recording layer provided on a plastic substrate, wherein an undercoat layer made of silicon oxide is provided in contact with the substrate between the substrate and the recording layer. An optical recording medium further comprising a protective layer made of a mixture of carbide and nitride between the undercoat layer and the recording layer.