JPS61202325A - Magnetic disk - Google Patents

Abstract

PURPOSE:To increase the number of times of contact start stop (CSS) by forming an Ni-Cu-P alloy film contg. 1-95wt% copper as a nonmagnetic hardened layer. CONSTITUTION:The hardened layer 2 on a nonmagnetic substrate 1 is subjected to a heat treatment at >=400 deg.C to form a non-magnetized Ni-Cu-P alloy layer thereon, by which the magnetization of the hardened layer is obviated even if a thin barium ferrite film 3 formed by heating during sputtering is used. The decrease in the reproduced output is obviated and since the layer has substantial hardness, the number of times of CSS is increased and a magnetic disk having high reliability is obtd. The Ni-Cu-P plating film which is not magnetized even if the film is subjected to the heat treatment of, for example, >=400 deg.C contains 1-95wt% Cu.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk used in a magnetic disk device.

[Conventional technology]

In recent years, the importance of external storage devices such as magnetic disks in computer systems has increased, and the demand for higher recording densities is increasing.

A magnetic recording device is composed of the main components of a recording/reproducing head and a magnetic disk. The magnetic disk rotates at high speed, and the recording/reproducing head floats a minute distance above the magnetic disk.

As the performance of magnetic recording devices improves, the load on the recording/reproducing head is reduced in order to reduce the flying distance, and contact start/stop (contact Φ start/stop: C
55) type head flotation system is adopted. In order to increase the recording density and performance of magnetic disks.

By making the recording medium thinner and more uniform, improving its magnetic properties (improving coercive force and squareness ratio), and ensuring stable head flying conditions at low flying heights, head-disk collisions (head crashes) are avoided. In order to prevent this, it is necessary to improve disk surface precision and head crush resistance.

Accordingly, it has become important to improve the quality of the substrate that supports the magnetic medium layer.

Conditions for a substrate suitable for high-density recording include good mechanical flatness and surface roughness, and a small number of defects. Furthermore, as the recording medium becomes thinner, the substrate needs to have sufficient hardness. In other words, if the substrate is soft, it will cause deformation such as depression when the magnetic head comes into contact with the magnetic disk, and not only will the magnetic head not be able to maintain a stable floating state, but the contact start/stop (contact start/stop), which indicates the reliability of the magnetic recording device, will occur. CSS) There is a problem that the number of times becomes small.

A magnetic disk using a barium ferrite thin film as a magnetic recording medium uses a target of barium ferrite (B, 0.6Fe20g), heats the substrate f: 400 to 650℃, and performs a DC2C bipolar sputtering process (M, Naoe, S,
Hasunuma Y-Ho8hi, S, Yanla
naka engineering FEE Trans,, Mag, *
MAG-17, No. 6 (1981), 3184-318
Page 6: Yamanaka, Nao, Hoshi, Hasunuma, 28th Spring Science Lecture Proceedings (1981), 467 Sada) and facing target sputtering method (M, Naoe, B, Yamanaka)
tY-HOθhi, ENG]11i1E Tran8
0M, g, , MAG-16 volume.

No. 5 (198G), pp. 646-64g; M, 1Jao
e tY, Ho5hi e S-Yamanaka,
J, Appl, Phya, Volume 53, Issue 3,
Page 274B (1982); Matsuoka, Hoshi.

Naoya Yamanaka, Proceedings of the 5th Applied Magnetism Lecture (19111).

13 pages; Matsuoka, Hoshi, Naoe, Yamanaka, 1981 IEICE General University (1
982), p. 155; Hoshi, Matsuoka, Naoe, Yamanaka.

IEICE Theory, Vol. J66-C, No. 1 (1983) p. 9)
A barium ferrite thin film was formed from K. The substrate is a silicon wafer with thermal oxide film (5iOz/
SL), silicon wafer, quartz glass, sapphire, etc. have been tested, but 8102/S1 is said to be the best in terms of thermal expansion coefficient, thermal conductivity, and barium ferrite properties (as mentioned above, IEICE theory).

766-C, 1,000 (1983), p. 9). However, the above-mentioned substrate has problems with durability, etc., and cannot be used for magnetic disks. on the other hand.

Anodized aluminum alloy substrates, which are commonly used for magnetic disks, have advantages such as improved surface precision because the alumite layer is hard and can be polished, but they also have many surface defects and are difficult to produce barium ferrite thin films. It had the disadvantage of not being heat resistant to temperatures above 400°C and cracking.

To solve this problem, a Ni-P plating film was considered as a nonmagnetic hardened layer on an aluminum alloy substrate.

N1-p plated film has good polishability, can be made thicker, and has a higher surface accuracy than anodized aluminum film, with 2 surface defects.

Both heat resistance was significantly improved.

[Problem that the invention seeks to solve]

However, among the above processes for barium ferrite film magnetic disks, the substrate temperature during sputtering is usually 400°C.
That's all. Since the magnetism generation temperature of the Nl-P plated film is usually around 200°C, after the above process: 11-
The P-plated film is magnetic. If the hardened layer becomes magnetized, it will be recorded in the magnetic medium layer and the hardened layer below this during magnetic recording, increasing the magnetization transition width, and during reproduction, the magnetization of the magnetic medium layer will be changed by the hardened layer below this. There was a problem in that the magnetic flux generated outside the magnetic recording medium was reduced due to the closing, resulting in a decrease in head output.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a highly reliable magnetic disk that can increase the number of CSS without decreasing the reproduction output.

[Means for solving the problem]

The magnetic disk of the present invention has a Ni-C1-P alloy film having a copper content of 1 to 95% by weight formed as a nonmagnetic hardened layer.

[Effect]

Nl-C having a copper content of 1 to 95% by weight according to this invention
The u-P alloy film does not become magnetized even when subjected to heat treatment, the reproduction output does not decrease, and the number of CSSs increases.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In the drawings, (1) is an aluminum alloy substrate which is a non-magnetic substrate, and (2) is a Ni-Cu-P which is a non-magnetic hardened layer.
The plated film, (3) is a barium ferrite sputtered film which is a magnetic medium layer, and (4) is a lubricating film.

Example N1-Cu was deposited on an aluminum alloy substrate by electroless plating.
-P plating film f, 20, a m was applied. N1-Cu
-P plating film is electroless Ni Cu manufactured by Uezai Kogyo Co., Ltd.
It was formed using a P plating solution. The composition of the film at this time was 160% N, 35% Cu, and 5% P by weight. A mirror finish was obtained by polishing, and a barium ferrite thin film was formed by sputtering.

Comparative Example 1 A N1-p plating film of t-20 μm was deposited on an aluminum alloy substrate by electroless plating. The N1-p plating film was formed using Blue Schumer manufactured by Nippon Kanigen Co., Ltd. A mirror finish was obtained by polishing, and a barium ferrite thin film was formed by sputtering.

Comparative Example 2 A 2 μm thick alumite film was formed on an aluminum alloy substrate by alumite treatment. A mirror finish was obtained by polishing, and a barium ferrite thin film was formed by sputtering.

The magnetic disk obtained as in Comparative Example 2 above was
Cracks have occurred in the alumite film.

It could not be put to practical use.

The magnetic disk obtained as in the above-mentioned Example, as well as the magnetic disk obtained as in Comparative Example 1, showed no cracks and was subjected to the C8B test. The magnetic disk obtained in the example has C8 compared to the case of comparative example 1.
The number of S times is approximately 1.5 times.

The playback output was improved by 30%.

In addition, in the above example, the composition weight % of the film was N160%, C
Although the case of U 35% and P 5% is shown, the Ni Cu-P plating film, which does not become magnetized even after heat treatment at 400° C. or higher, has a CU content of 1 to 95% by weight. When the Cu content is extremely high or low, it is difficult to increase the film thickness with a uniform composition.
~80% by weight is desirable.

〔Effect of the invention〕

In addition to the above, according to the present invention, the cured layer on the substrate has four
N1- +4- which does not become magnetized by heat treatment above 00℃
Since the P alloy layer is used, even if a barium ferrite thin film formed by heating during sputtering is used, the hardened layer will not become magnetized and the reproduction output will not decrease.Since it is sufficiently hard, the number of CSS cycles can be increased. This has the effect of providing a highly reliable magnetic disk.

[Brief explanation of drawings]

The drawing is a sectional view showing a magnetic disk obtained according to an embodiment of the present invention. In the figure, (1) is a non-magnetic substrate, (2) is a Ni-C
A u-P alloy nonmagnetic hardened layer, (3) a barium ferrite magnetic medium layer, and (4) a lubricating film.

Claims (1)

[Claims] In a magnetic disk having a nonmagnetic substrate, a nonmagnetic hardened layer coated on the nonmagnetic substrate, and a barium ferrite magnetic medium layer coated on the nonmagnetic hardened layer, the nonmagnetic hardened layer has a copper content of 1. ~95% by weight Ni-Cu-P
A magnetic disk characterized by an alloy coating.