JPS60205845A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance of a recording layer and to increase durability with a medium which performs recording and reproducing by a light beam by laminating alternately respectively >=1 layers of the 1st protective layers consisting of an inorg. material and the 2nd protective layer consisting of a metallic film and inorg. material on said layers adjacently to the recording layer. CONSTITUTION:An undercoating layer 2 consisting of SiO, etc. is formed on a writing side transparent substrate 1a made of plastic, a recording layer 3 and an org. layer consisting of SiO2, Si3N4, AlN, etc. as the 1st protective layer 4a are formed thereon with a recording medium having a photomagnetic recording layer 3 consisting of CdTbFe. etc. Respectively >=1 layers of metallic films 6 consisting of a metal having excellent moisture resistance such as Al, Cr, Au, Si, Ti, etc. or the alloy thereof, etc. and inorg. material films consisting of SiO, etc. as the 2nd protective film 4b are alternately laminated on the layer 4a. An outside plastic substrate 1b is adhered via a silicone adhesive agent 5, etc. onto the layer 4b. The deterioration of the recording layer as a result of oxidation by exposure to the atm. and moisture is thus prevented and the optical disk, etc. having excellent durability are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording medium capable of performing recording reproduction using a light beam.

Conventionally, optical recording media used in optical discs 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, Thermoplastic recording media and the like are known. For example, it is formed of an alloy thin film of a local earth-transition metal. As a magneto-optical recording medium, Hn
Polycrystalline thin films such as Bi, MnGuBi, GdCo,
GdFe, TbFe, DyFe.

Amorphous thin films such as GdTbFe and TbDyFe, G
Single crystal thin films such as dIG are known.

Among these thin films, there are various issues such as film formability when manufacturing large-area thin films at temperatures near room temperature, writing efficiency for writing signals with small photothermal energy, and readout of written signals with a good S/N ratio. In consideration of read efficiency and the like, recently, the amorphous fi4JII is 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 GdT
It has been discovered that bFeCo is a magneto-optical recording medium with a sufficiently large Kerr rotation angle and readout capability 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, such deterioration of recording characteristics due to oxidation is a common drawback not only in magneto-optical recording media but also in optical recording media.

In order to eliminate such drawbacks, a protective cover made of, for example, a transparent material, such as 5i02, Si
A disk-shaped recording medium provided with a protective layer of O or further sealed with an inert gas has been proposed.

That is, in a conventional optical recording medium, for example, as shown in FIG. 1, an undercoat layer 2 is formed on a writing side plastic substrate la, and a recording layer 3. It is obtained by bonding to the external plastic substrate 1b via the protective layer 4 and the adhesive layer 5.

However, even with this configuration, when left in a high humidity state for a long time, the recording characteristics deteriorated and sufficient corrosion resistance could not be obtained.

An object of the present invention is to provide an optical recording medium that has better corrosion resistance than conventional recording media.

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

That is, a first layer made of an inorganic material is placed adjacent to the optical recording layer.
This is achieved by an optical recording medium comprising a protective layer, and one or more metal films and a second protective layer made of an inorganic material are alternately laminated on the first protective layer.

The metal film is Aj! , Cr, Au, Si,
It is preferable to use a single metal having excellent moisture resistance, such as Ti, or an alloy thereof. A suitable thickness of the metal film is 10G0A to 2000mm.

The inorganic substance constituting the first and second protective films is S.
iO+S13Nm+AIIN etc. are suitable, and a mixture of these may be used. The thickness of the protective layer needs to be 1000 to 3000A. If it is thinner than IGOOA, a sufficient protective effect cannot be obtained, and if it is thicker than 3000A, cracks may occur, which is not preferable. In the present invention, as long as one or more metal films and one or more second protective layers are provided on the first protective layer, a structure in which two or more layers of these layers are alternately laminated may also be used.

The optical recording medium of the present invention can have either a laminated structure or an air sandwich structure.

An embodiment of the optical recording medium of the present invention having a laminated structure is shown in FIG.

In the optical recording medium shown in FIG. 2, an undercoat layer 2 is formed on a writing side plastic substrate la, and a recording layer 3, a first protective film 4a, a metal film 6. A second protective layer 4b is provided, and an external plastic substrate ib is further provided via an adhesive layer 5.
Obtained by bonding with.

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

Example 1 In FIG. 2, an acrylic material is used as the plastic substrate 1a, an SiO film of about 1000 is formed as the undercoat layer 2, and a GdTbFe film of tooA is used as the recording layer 3.
Using a Co quaternary amorphous thin film, a SiO film with a thickness of 3000 mm as the first protective film 4a, and a SiO film with a thickness of approximately 10 mm as the metal film 6.
An optical recording medium of the present invention was obtained by providing a 00A AI film, a SiO film having a thickness of 3000A as the second protective film 4b, and using a silicon adhesive as the adhesive layer 5. With the thickness of this example, the recording layer does not transmit 4i reproduction light. In addition to measuring the rotation angle θk and coercive force Hc from the obtained recording medium, a 500-hour humidity test was conducted in a constant temperature and humidity chamber at 45° C. and 95% relative humidity.

For comparison, a test was also conducted on a recording medium having the same configuration except that the metal film 6 and the second protective film 4b were not provided.

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

Example 2 A magneto-optical recording medium having the same film structure as in Example 1 was produced except that a Ti film was provided as a metal film instead of the Aj film in Example 1.

As in Example 1, a 500-hour humidity test was conducted in a constant temperature and humidity chamber at a rotation angle θk, a coercive force Hc, 45° C., and a relative humidity of 95%.

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

The present invention is effective not only for magneto-optical recording media but also for media having a recording layer made of a chalcogen compound that is easily oxidized.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the structure of a conventional optical recording medium, and FIG. 2 is a schematic diagram for explaining the structure of the optical recording medium of the present invention. la, lb ---Plastic substrate 2 ---Undercoating layer 3 ---Recording layer 4, 4a, 4b ---Protective layer 5 -m-Adhesive layer 6--Metal film

Claims (1)

[Claims] In an optical recording medium having an optical recording layer, 111
A first protective layer made of an inorganic material is provided adjacent to the recording layer, and further, one or more layers of a single-layer film and a second protective layer made of an inorganic material are alternately laminated on the first protective layer. An optical recording medium made of