JPH0673169B2 - Magnetic disk - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic disk used as a file storage in an information processing system.

2. Description of the Related Art In recent years, in order to meet the demand for high-density magnetic recording, magnetic disks have been actively developed in which magnetic metal thin films are used as magnetic recording layers.

2 and 3 are sectional views of an example of a conventional magnetic disk.

In FIG. 2, 1 is a substrate made of a polyester film, 2 is a non-magnetic underlayer of Cr or the like, 3 is Co-Ni (Ni: 20 wt.
%) Sputtered film 4 is a fluorine-containing plasma polymerization protective film.

FIG. 3 shows a cross section of a floppy disk for double-sided access perpendicular magnetic recording.

In FIG. 3, 5 is a substrate 6 made of polyimide, and 6 and 7 are permalloy (Ni is often used in a content of around 80 wt%.).
Underlayers 8 and 9 are CoCr (Cr: 20 wt%) sputtered films, which are so-called perpendicularly magnetized films in which the direction of the easy axis of magnetization is perpendicular to the substrate surface. [For example, Tohoku University Research Institute Symposium Proceedings "Perpendicular Magnetic Recording" PP.131-141 (1984)] In both Figures 2 and 3, the total value of the thickness of the thin film was 0.3 μm to 0.7 μm. large.

It is explained that this is due to the fact that the coercive force required for high density magnetic recording is secured.

Reference numerals 10 and 11 in FIG. 3 are the same as 4 in FIG. 2 and are protective films.

Problems to be Solved by the Invention However, with the above-mentioned configuration, it is not possible to sufficiently avoid damage to the medium that occurs when the medium comes into contact with the magnetic head. This phenomenon remarkably lowers reliability and is desired to be improved.

This is probably because the strength of the thin film against the stress in the compression direction is weak in the dense magnetic thin film used in the conventional disk. In view of the above circumstances, the present invention receives it from the magnetic head. An object of the present invention is to provide a magnetic disk provided with a magnetic recording layer having strength against pulse-like fluctuation of compressive stress.

Means for Solving the Problems In order to solve the above problems, the magnetic disk of the present invention comprises:
A fine particle coating layer is arranged on a polymer film whose longitudinal heat shrinkage is 30% to 60%, and a ferromagnetic metal thin film formed by the oblique vapor deposition method is provided thereon.

Operation According to the present invention, the in-plane isotropy of the magnetic recording layer required for the magnetic disk has the anisotropy of the oblique vapor deposition film and the vapor deposition film in the longitudinal direction of the heat shrinkage ratio of the polymer film. It is considered that a large coercive force can be obtained because it is averaged due to the difference in the lateral direction, and the obliquely evaporated film has many defects and many voids, and is strong against pulse-like compressive stress. Therefore, the magnetic head can be prevented from being damaged, and the reliability of the magnetic disk can be maintained.

Embodiments Hereinafter, magnetic disks according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged sectional view of a magnetic recording medium according to an embodiment of the present invention.

In FIG. 1, 12 is a polyethylene terephthalate film having a thickness of 26 μm, and the thermal shrinkage ratio at 150 ° C. for 3 minutes is in the range of 30% to 60% in the longitudinal direction and the transverse direction. It is confirmed that the size of the heat shrinkage is determined by the ratio in the range of 1.5% to 8%.

Further, 150 ° C. for 3 minutes is one evaluation method, but it is sufficient for each film of polyethylene 2-6 naphthalate, polycarbonate and polyphenylene sulfide to satisfy this condition.

13 is a fine particle coating layer, which averages 300 fine particles of silica with a diameter of 1
It is fixed on the surface of the film 12 with 0 / (μm) ² and an epoxy resin (average thickness 40Å).

14 is a Co-O film formed by the oblique deposition method and has a thickness of 0.15 μm.
The atomic% ratio of Co: O is 84:16.

This film was formed by electron beam evaporation of Co under an oxygen partial pressure of 5 × 15 ⁻⁵ Torr while moving the film along a cylindrical can having a diameter of 1 m. The minimum incident angle was 22 degrees, and the surface temperature of the cylindrical can was kept at 66 [℃].

The coercive force of the obtained Co-O film was in the range of 805 ± 15 [e], and it could be considered to be almost isotropic in the plane.

Reference numeral 15 is a coating film of lead stearate formed by the solution coating method, and the average film thickness was 110Å.

A 3.5-inch magnetic disk with a wide width (50 cm width, length of 1000 m) was applied, and recording and reproduction were repeated using an amorphous alloy head.

The frequency of drop-out and drop-in was investigated by tracing the outermost track and the innermost track alternately for 10 minutes each.

For comparison, a polyimide film (thickness is
CoNi (N: 20wt%) is formed 0.16μm on 25μm), and lead stearate is spin-coated on top of it with an average film thickness of 110Å
The coated medium was used. The coercive force of this Co-Ni is 600 (
e).

Since there is a difference in coercive force from the example, the recording bit length is compared with 0.6 μm so as not to be disadvantageous to the comparative example, and the dropout is when the signal output has a steady value of 0 (dB),
The time when the output increased more than drop-in +3 (dB) when it decreased more than -10 (dB) was counted.

The table shows the results of comparison of the number of drip-out pulses and the number of drop-in pulses for each of the Examples and Comparative Examples every 10 minutes.

As described above, according to the present embodiment, it is possible to maintain a good level of dropout and dropin that are considered to change due to damage to the magnetic recording layer due to the combination of the anisotropy of heat shrinkage and the oblique deposition. Recognize.

Although polyethylene terephthalate is used as the polymer film in the examples, polyethylene 2-6 naphthalate, polycarbonate, polyphenylene sulfide, polyamide, polyimide or the like may be used.

The constituent material of the fine particle coating layer was the silica and epoxy resin, other _{CaCO 3, TiO 2, CaSO 4} , BaSO 4, Fe 3 O 4, a polyester sphere like particles, polyester, polysulfone, polyurethane, polyimide, etc. Resin may be used.

A Co-O film was used as the ferromagnetic metal thin film, but other Co-N films were used.
i, Co-Cr, Co-Ti, Co-Mo, Co-W, Co-Ta, Co-Si, Co-Sn,
An oblique deposition film such as Co-Sm, Co-Pt, Co-Rh, Co-Ru, Co-Ni-P, and Co-Ni-O may be used.

The overcoat for the purpose of protection and lubrication may be properly devised.

As described above, according to the present invention, since the surface of the magnetic disk is not damaged by the pulse-like compressive stress received from the magnetic head, even if it is repeatedly used for a long time, a signal error such as dropout or dropin occurs. It is possible to obtain an excellent effect that the state of the extremely small amount can be maintained.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a magnetic disk according to an embodiment of the present invention, and FIGS. 2 and 3 are enlarged sectional views of a conventional magnetic disk. 12 …… Polymer film, 13 …… Fine particle coating layer, 14 …… Ferromagnetic metal thin film.

Claims (1)

[Claims] 1. Thermal shrinkage in the longitudinal direction is 30% to 60% in the transverse direction.
A magnetic disk comprising a fine-particle coating layer on the polymer film, and a ferromagnetic metal thin film formed on the polymer film by oblique deposition.