JP2590925B2 - Magneto-optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium used for a magneto-optical memory, and more particularly to a magneto-optical recording medium that has been subjected to a process for improving weather resistance.

[Conventional technology]

The recording layer of a magneto-optical recording medium is made by combining a polycrystalline thin film such as MnBi and MnCuBi formed on a transparent substrate, a rare earth metal such as Tb, Gd, and Dy and a transition metal group such as Fe and Co. Non-crystalline alloy thin films are known. Among these thin films, amorphous alloy thin films have advantages such as high writing sensitivity, no grain boundary noise, and easy formation of a film having magnetic anisotropy perpendicular to the film surface. Most promising as a layer.

FIG. 2 is a sectional view of a conventional magneto-optical recording medium. In the figure, since the amorphous alloy thin film 3 is made of an element having high activity, usually, SiO, SiO ₂ , Si
A dielectric thin film of ₃ N ₄ , AlN or the like is formed as protective layers 2 and 4, and the substrate 1 is air-sandwiched so that the recording layers 3 are located inside each other to protect the recording layer 3 (FIG. 1). (A)) or a method of bonding together by a close contact structure (FIG. 1 (b)) has been proposed. Here, glass or plastic is used as a substrate material family, but especially plastic substrates are widely used because they are not easily broken and are lightweight and inexpensive.

[Problems to be solved by the invention]

However, since the above plastic substrate has high water absorption, water permeability and oxygen permeability, when a protective layer is not formed on the outside of the substrate as in the above-described structure, when exposed to high temperature and high humidity conditions for a long time, Moisture and oxygen in the air gradually permeate from the outside of the substrate to cause the substrate to absorb moisture and elongate, which may cause peeling or cracking of the protective layer or deterioration of the recording layer.

An object of the present invention is to provide a highly reliable magneto-optical recording medium by providing a protective layer having an excellent moisture-proof effect on the outer surface of a plastic substrate to prevent the above-mentioned problems caused by water absorption of the plastic substrate. .

[Means for solving the problem]

The magneto-optical recording medium of the present invention includes a plastic substrate having a recording layer formed on one surface, or a substrate having an air sandwich structure or a close bonding structure in which the recording layers of the two substrates oppose each other inside. The magneto-optical recording medium includes a dielectric layer formed on the entire surface including the front and back surfaces and side surfaces of the medium, and a protective layer of perfluoropolyether formed on the dielectric layer.

[Action]

A typical layer configuration of the magneto-optical recording medium according to the present invention is as shown in FIG. That is, on a plastic substrate 1 such as polycarbonate (PC) or polymethyl methacrylate (PMMA), the first and second dielectric layers 2 and 4 made of Si ₃ N ₄ etc. In a magneto-optical recording medium on which a recording layer 3 made of a non-crystalline alloy thin film such as TbFeCo, GdTbFe, DyFeCo or the like having a perpendicular easy axis of magnetization is formed, this corresponds to the side of the medium opposite to the surface on which the recording layer 3 is formed. Third dielectric layer 7 made of SiO ₂ or the like on the outer surface
Is formed, and a moisture-proof layer 8 made of perfluoropolyether is formed thereon. FIG. 1A shows an air sandwich structure, and FIG. 1B shows a close bonding structure. Reference numeral 5 denotes a spacer constituting the air sandwich, and reference numeral 6 denotes an adhesive.

The perfluoropolyether used in the present invention has the following structure.

F (CF (CF ₃ ) CF ₂ O) _n C ₂ F ₅ CF ₃ O (CF ₂ CF (CF ₃ ) O) _m (CF ₂ O) _n CF ₃ CF ₃ O (C ₂ F ₄ O) _p ( CF ₂ O) _q CF ₃ F (C ₃ F ₆ O) _n C ₂ F ₅ RCF ₂ O (CF ₂ O) _m (C ₂ F ₄ O) _n CF ₂ R F (CF (CF ₃ ) CF ₂ O ) _n R where R is _{-COOH, -COOCH 3, -NH 3,} -CH 2 OH, -CONH (CH
_{3) C 6 H 3 NCO,} -CONHC 2 H 4 Si (OCH 3) 3 is a functional group such as. n, m, p, and q are integers from 1 to 100.

〔Example〕

 Next, examples of the present invention will be described.

SiN with a refractive index of 2.0 and a thickness of 1,000 mm as a first protective layer on a polycarbonate substrate with a thickness of 1.2 mm, an outer diameter of 130 mm, and an inner diameter of 15 mm
1000 Å thick Tb _0.22 (Fe _0.9 Co _0.1 ) as film and recording layer
_0.78 film, the same as the first protective layer SiN as the second protective layer
Films were formed in order. Each film was continuously formed by magnetron sputtering without breaking vacuum.

The two substrates on which the thin films were formed as described above were bonded together so that the recording layers were located inside each other to form an air sandwich structure. After that, 2,000 SiO ₂ was added on this outer surface.
Å Vapor deposition, followed by spin-coating a 0.03% solution of perfluoropolyether having the above structure (solvent: 1,1,3 chlorotrichloroethane) at 1,000 rpm for 10 seconds to obtain a film thickness of about 5
An optical recording medium (A) of the present invention having a structure in which a 0 ° moisture-proof layer is formed; a magneto-optical recording medium (B) having a structure in which the moisture-proof layer is formed directly on a substrate without forming an SiO ₂ layer; Si
A magneto-optical recording medium (C) having a conventional structure without O ₂ or a moisture-proof layer was prepared, and subjected to a high-temperature and high-humidity storage test under the following three conditions.

Test conditions 60 ° C 90% 200 hours 70 ° C 90% 200 hours 85 ° C 90% 200 hours As a result, in the conditions, the magneto-optical recording medium (A),
No peeling or cracking occurred in both (B) and (C),
Under the conditions, the conventional structural medium (C) alone had cracks and cracks. The medium (B) having only the moisture-proof layer on which no SiO ₂ was formed did not peel or crack, but localized aggregation of the moisture-proof layer occurred, resulting in uneven coating of the moisture-proof layer. Only the magneto-optical recording medium (A) of the present invention did not exhibit peeling, cracking, or uneven coating under any of the above conditions.

It should be noted that the magneto-optical recording medium of the present invention is not limited to the above embodiment, and a recording layer is formed only on one surface of a medium having an adhesively bonded structure or a bonded structure without departing from the gist of the present invention. The present invention can be similarly applied to a medium having a single plate or a medium having a single-plate structure.

〔The invention's effect〕

As described above, according to the present invention, a magneto-optical recording medium having improved weather resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional example. DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... 1st dielectric layer, 3 ... recording layer, 4 ... 2nd dielectric layer, 5 ... spacer, 6 ... adhesive, 7 ... 3rd dielectric layer, 8 ...... Moisture-proof layer.

Claims (1)

(57) [Claims] 1. A magneto-optical recording medium comprising a plastic substrate having a recording layer formed on one side, or a substrate having an air-sandwich structure or a close-adhesion structure in which the recording layers of the two substrates face inward. In, a dielectric layer formed on the entire surface including the front and back and side surfaces of the medium,
And a protective layer of perfluoropolyether formed on the dielectric layer.