JPS607631A - optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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.

Optical recording media conventionally used in optical disks 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, and thermostatic recording media. 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, Mn13
i, polycrystalline thin films such as MnCuB1, GdCo, G
dFe, TbFe r DyFeyQdTbFe
, TbDyFe amorphous thin films, GdIG monocrystalline thin films, etc. are known.

Among these thin films, the film forming performance when producing a large area thin film at a temperature near room temperature, the writing efficiency for writing signals with small photothermal energy, and the readout for reading out written signals with a good S ratio. Taking efficiency etc. into consideration,
Recently, the amorphous thin film is considered to be excellent as an optical recording medium. GdTbFe also has a large Kerr rotation angle (it has a single Curie point around 150°C, making it suitable as a magneto-optical recording medium. Furthermore, as a result of our research aimed at improving the Kerr rotation angle, we found that GdTl)FeCO has a large Kerr rotation angle. It has been found that this is a magneto-optical recording medium that has a sufficiently large value and can be read with a good S/N ratio.

However, amorphous magnetic materials, such as GdTbF''e, generally have poor corrosion resistance, and have the disadvantage of being corroded in a humid atmosphere, resulting in deterioration of magnetic properties. This is a common problem not only with media but also with the above-mentioned optical recording media.

In order to eliminate these drawbacks, conventional methods have been to provide a protective layer on the recording magnetic layer made of an amorphous magnetic material, or to create an air sandwich structure or a bonded structure in which the recording magnetic layer is sealed with an inert gas. A disc-shaped magneto-optical recording medium has been proposed.

Protective layer C: Ti, Cr, Zn, A7. Metals such as S, i, SiO2゜5x()+Tt()z+Al2O3,
It is formed by vapor depositing an oxide such as CrzOa or MgF 2 . A protective layer made of oxide or MgF 2 tends to have pinholes when formed, and a protective layer made of metal has the disadvantage that the battery action with the magnetic material may actually accelerate the corrosion of the magnetic material. Ta.

In addition, since metal has high thermal conductivity, heat easily escapes during recording (and recording sensitivity may decrease. This can be improved by using an organic resin with excellent heat insulation properties, but organic resin absorbs moisture. , since it is moisture permeable, its corrosion prevention effect is low.

An object of the present invention is to provide an optical recording medium in which corrosion of the recording layer is substantially prevented without reducing sensitivity.

This objective is achieved by the following optical recording medium. An optical recording medium characterized in that a dielectric layer is formed on an optical recording medium, and a metal layer is further formed on the dielectric layer.

As a dielectric layer, one that has low thermal conductivity, can be formed into a thin film, and does not alter the quality of the recording layer is suitable, and the inventors of the present invention found out after investigation that a nonmetal, that is, a dielectric material, would meet this purpose. Ta. For example, SiO, 5iOz, Al2
O3, MgF2. Inorganic materials such as ZrO2 are formed using methods such as vacuum evaporation or sputtering, or organic resins such as epoxy, silicon, urethane, and acrylic are used by dip coating or spin cording.

It can be formed by coating with a method such as roll coating, or it can be formed by vacuum deposition or CVD using a resin such as Voripa or laxylylene, or it can be formed by forming a resin from a monomer such as tetrafluoroethylene by a method such as plasma polymerization. .

As for the metal layer, Ti, AA! , Cr, Sn, Zn, Ni
, Ta, or other material with good corrosion resistance, and is formed by a method such as vacuum evaporation or sputtering.

The dielectric layer and the metal layer have a thickness of o and i to 10.0 μm, respectively.

It is preferable to form it to a thickness of 0.05 to 1.0 μm.

The present invention can be applied to optical recording media having an air sandwich structure or a bonded structure. Further, an anti-reflection layer for use light can be formed between the write-side substrate and the optical recording layer. The adhesive layer used to bond the substrate with the recording layer and the protective substrate is Diana [Ryoe Kagaku ■] and Coal Top [
Nippon Kako Paper ■〕, V, I), M (Nihon Kagaku ml industry■〕
, Ferroguard [Ronco Laboratories, Inc., USA], Zelast [Ocean Liquefied Gas], Killesguard [Nippon Kagaku Sangyo]
] Corrosion protection layer containing volatile rust preventive agent such as metal guard [
Mobil Oil ■], Ruston [Tobi Chemical ■], C, Rl
C, an anti-corrosion layer containing an oil-soluble rust preventive agent such as Diarate [Ryoe Kagaku ■], a metal fine powder-containing layer containing fine metal powder such as AA, Sn, Zn, Ti, Cr, etc., MgO.

B ao * CaOr AN 203 , CaC12
1KOI ■z Na0f-1* Ca SO4・'/
21-I20 rSi02. xH2O,, P2O5, activated alumina, a desiccant-containing layer containing a desiccant such as Mg(clo4)2IZnBrz, 2,4゜6-drimethylpyridine, sodium dimethylglycine, tris(hydroxymethyl)aminomethane, 2-amino -2-methyl-
It can also be replaced with a basic organic substance-containing layer containing a basic organic substance such as 1,8-propanediol.

In the optical recording medium of the present invention, by forming a dielectric layer on the second side of the optical recording layer and further providing a metal layer on top of the dielectric layer, the corrosion resistance of the recording layer is superior to that of the conventional one. Equivalent recording sensitivity can be obtained.

EXAMPLES The present invention will be specifically described below with reference to Examples.

Example 1 A magneto-optical recording medium having the structure shown in FIG. 1 was manufactured as follows.

In a high-frequency sputtering device, a magnetic recording layer (2) was formed by sputtering using a 1-inch square white plate glass as a substrate (IJ) and a composite target consisting of 5 mm square Gd and Tb pieces uniformly arranged on 100 mm diameter FeO. did.

On top of that, A#03 was deposited as a dielectric layer (3) to a thickness of 0.3 μm by electron beam heating using a vacuum evaporation device, and then Ti was deposited as a metal layer (4) to a thickness of 0.3 μm. A magneto-optical recording medium was fabricated by vapor deposition at a thickness of 2 μm.

This magneto-optical recording medium was placed in a constant temperature and humidity chamber at 85° C. and 85% relative humidity to conduct a corrosion resistance test.

AA for comparison! A zo3 dielectric layer formed in the same manner, a Ti metal layer formed in the same manner, and a magneto-optical recording medium in which neither a dielectric layer nor a metal layer were formed were also tested at the same time. The results are shown in Figure 2.

The vertical axis of FIG. 2 shows the change in coercive force as a ratio to the initial value, and the horizontal axis shows the test time.

The larger the decrease in coercive force, the more advanced the corrosion.

As is clear from Figure 2, the magneto-optical recording medium with a dielectric layer and a metal layer has higher durability than those with only a dielectric layer, only a metal layer, and those with neither layer. Excellent corrosivity.

Example 2 A magnetic recording layer (2) was formed on the substrate (1) in the same manner as in Example 1.
After that, a dielectric layer (3) of Al2O3 with a thickness of 0.8 μm was formed by electron beam heating using a vacuum evaporation device.
A magneto-optical recording medium was fabricated by depositing Cr to a thickness of 0.3 μm as a metal layer (4) thereon. This magneto-optical recording medium was placed in a constant temperature and humidity chamber at 85° C. and 85% relative humidity to conduct a corrosion resistance test. For comparison, a magneto-optical recording medium formed in the same manner except for the Cr metal layer was also tested at the same time, and the results are shown in FIG. The graph can be viewed in the same way as in Figure 2.

As is clear from FIG. 3, the magneto-optical recording medium in which a dielectric layer and a metal layer are formed has better corrosion resistance than the magneto-optical recording medium in which only a metal layer is formed.

Example 3 A magnetic recording layer (2) was formed on the substrate (1) in the same manner as in Example 1.
After that, a dielectric layer (3) of SiO is deposited to a thickness of 0.3 μm by electron beam heating using a vacuum evaporation apparatus, and then a metal layer (4) of Ti is deposited on top of the dielectric layer (3).
A magneto-optical recording medium was fabricated by depositing a film with a thickness of 0.2 μm. This magneto-optical recording medium was placed in a constant temperature and humidity chamber at 85° C. and 85% relative humidity to conduct a corrosion resistance test.

For comparison, a magneto-optical recording medium having only a dielectric layer of SiO was also tested at the same time. The results are shown in Figure 4. The graph can be viewed in the same way as in Figure 2.

As is clear from FIG. 4, the magneto-optical recording medium in which a dielectric layer and a metal layer are formed has better corrosion resistance than the magneto-optical recording medium in which only a dielectric layer is formed.

Example 4 A magnetic recording layer (2) was formed on the substrate (1) in the same manner as in Example 1.
After forming, a dielectric layer (3) of polyparaxylylene (trade name: PA, RYLENE) was deposited to a thickness of 1.0 by vacuum evaporation.
A magneto-optical recording medium was fabricated by depositing A with a thickness of 0.3 μm as a metal layer (4) thereon. This magneto-optical recording medium was heated at 85°C and relative humidity 85%.
A corrosion resistance test was conducted by placing the sample in a constant temperature and humidity chamber. For comparison, a magneto-optical recording medium in which only a dielectric layer of polyparaxylylene was formed in the same manner, and a magneto-optical recording medium in which only a metal layer of AA was formed in the same manner were also tested at the same time. The results are shown in Figure 5. The graph can be viewed in the same way as in Figure 2.

As is clear from FIG. 5, the magneto-optical recording medium in which a dielectric layer and a metal layer are formed has superior corrosion resistance compared to those in which only a dielectric layer is formed and those in which only a metal layer is formed.

Further, after irradiating a pulse of semiconductor laser light (wavelength 5s2o'h) from the substrate side, the diameter of the recording spot was measured using a polarizing microscope to examine the recording sensitivity. The results are shown in Table 1.

Table 1 The recording sensitivity of this example is superior to that of the one having only the A7 layer, and the sensitivity is equivalent to that of a magneto-optical recording medium having only a polyparaxylylene layer.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the structure of the magneto-optical recording medium of the present invention, and FIGS. 2, 3, 4, and 5 are corrosion resistance tests of the magneto-optical recording medium of the present invention. This is a graph showing the results for a conventional magneto-optical recording medium. 1...Glass substrate 2...Magnetic recording layer 3...Dielectric layer 4...Metal layer No. Fig. 1 @ Fig. 2 t Ya test time light (Hr) Fig. 3 Anchor ゛ time qC city) @ 4wi Mukuro's breeding time (acid) Flute 5 Fig. % + Tokizono (8r) Continuation of 1st page 0 shots Author: Koji Sawamura, 3-30-2 Shimomaruko, Ota-ku, Tokyo, Canon Co., Ltd. -1ε

Claims (1)

[Claims] An optical recording medium characterized in that a dielectric layer is formed on an optical recording layer, and a metal layer is further formed on the dielectric layer.