JPS61255531A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled magnetic recording medium having excellent weather resistance and reliability by forming a Cr film on a metallic magnetic film with physical vapor deposition, further depositing a protective film thereon and allowing an active metallic Cr atom to remain in the Cr film layer. CONSTITUTION:A Cr film is coated on a metallic magnetic film 3 by sputtering with a PVD method (physical vapor deposition) wherein the partial pressure of Ar is regulated, for example, to 1-40mtorr and a protective film 5 is formed thereon. At this time, the Cr atom is not converted into a compd., etc., and allowed to remain in the layer as an active Cr atom layer having 5mm film thickness. Consequently, even when a defective part (uncoated part) is present in the thin Cr protective film 5 and water, etc., intrudes into the part to corrode the metallic magnetic film 3, Cr hydroxide, etc., is formed by the formation of a galvanic couple between the metallic magnetic film having a noble electrode potential and the active Cr film having a base electrode potential. Consequently, excellent corrosion resistance can be obtained by the coating of the magnetic film 3. Accordingly, even when the weather resistant protective film 5 is thin, the weather resistance can be improved and the high-density recording can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium used in a magnetic recording device, such as a magnetic disk device.

2. Description of the Related Art At present, most of the magnetic disks used as magnetic recording media are oxide-coated media, and metal thin film media formed by plating or sputtering are attracting attention as a means of further improving recording density.

However, metal thin film media do not have sufficient weather resistance (corrosion resistance), and also have insufficient abrasion resistance due to magnetic head contact during start/stop (C8C). A protective film is required on the metal magnetic thin film to impart properties and wear resistance.Also, in order to increase the recording density, it is preferable that the magnetic head be as close as possible to the surface of the metal magnetic film. The thinner the better.

Conventionally, this type of protective film has been formed by wet plating of metal thin films (Rh, Au, Cr, N1-P, etc.), oxide films (surface oxidation of metal magnetic films, SiO2, A12O3, etc.), and nitride films (813N4, etc.). ), and hard protective films such as carbide films (SiC, etc.) have been proposed.

Among these protective films, there are some that have considerably excellent weather resistance and abrasion resistance. For example, film thickness so
nm spin code S 102 film (Hanbe et al. 2'''3.2
"Continuous thin film media for gigabyte aggregated magnetic disk drives"
Research practical application report, Volume 31, No. 1, p277-289
). In order to further increase the recording density, we aim for a two-layer protective film with a thickness of 50 nm or less (lower layer is a chromium oxide film with good weather resistance, and upper layer is a Si02 film).
has also been proposed.

(Japanese Unexamined Patent Publication No. 58-177528) Problems to be Solved by the Invention However, although these protective films can ensure some degree of corrosion resistance, the thinner the film, the more corrosion occurs, and the longer the corrosion test time, the more corrosion occurs. It corrodes a lot. (Akio Tago, “Silicon Compound Protective Film for Plated Magnetic Disks”, Precision Machinery, Vol. 49, No. 6, P747-761, Figs 6-8
) On the other hand, when the recording density is further increased, even a very small corrosion defect will impair the reliability of the magnetic recording medium. In addition, the environment in which magnetic recording devices are used has become more severe for media, such as those for personal use, and there is a desire to develop magnetic recording media with better weather resistance.

Therefore, an object of the present invention is to provide a magnetic recording medium with high weather resistance in which the metal magnetic film does not corrode at all even in the case of an extremely thin protective film or a long-term corrosion test.

Means for Solving the Problems In order to solve the above problems, the present invention uses a PVD method (physical vapor deposition method), for example, an Ar gas partial pressure of 1 to 4 on a metal magnetic film.
Even when a chromium film is coated by sputtering at 0 mtorr and a protective film is formed on it, the chromium atoms remain intact as chromium compounds, and the active chromium atomic layer is sufficient, for example, with a film thickness of 5 nm or more. It is intended to ensure that it remains.

For production The effect of this technical means is as follows.

Generally, when coating a thin film, defects (uncoated areas)
The thinner the film is, the more difficult it is to completely cover the film with no particles. For example, in a coating method such as sputtering, when the film thickness is thin, an island-like structure and uncoated portions are formed.

The present invention can provide excellent weather resistance (corrosion resistance) even in the presence of such uncoated portions due to the following effects.

In other words, when water, which is a corrosion factor, invades the defective parts (uncoated parts) of the thin chromium protective film and tries to corrode the metal magnetic film, the metal magnetic film has a negative electrode potential and the base electrode potential. Chromium corrosion products such as chromium hydroxide are generated due to the formation of a battery couple with an active ROM film.
It can be coated with a metal magnetic film to provide excellent corrosion resistance.

By the way, a chromium film with such an excellent anticorrosion effect must be an active chromium film with a lower potential than a metal magnetic film, such as a film created by a PVD method such as sputtering. Wet-plated chrome film, which has been used as a protective film due to its hardness, is not suitable.

For example, as described in Japanese Unexamined Patent Publication No. 55-73931, the corrosion resistance as a protective film is insufficient, and wet-plated films cannot exhibit the functions and effects of the present invention.

Furthermore, as shown in, for example, Japanese Patent Application Laid-Open No. 56-41524, a chromium film is sometimes used as an interface layer to improve the adhesive strength between the metal magnetic film and the protective film. However, this chromium has strong chemical bonds with the upper and lower layers of the chromium film, and there is almost no active chromium atomic layer, and this is an interfacial layer that is desirable to eliminate the need for. , the effect is completely different.

EXAMPLE FIG. 2 shows the weather resistance of the chromium film coating of the present invention. This is done on a Co-20at%Ni metal magnetic film with a film thickness of 6~
The weather resistance is shown in terms of corrosion area percentage when an 80 nm chromium film was coated by sputtering and kept for 10 weeks in a constant temperature and humidity chamber maintained at a temperature of 26° C. and a relative humidity of 8 degrees.

As shown in FIG. 2, if a chromium film of 5 nm or more is coated, it exhibits extremely excellent weather resistance regardless of the film thickness. In particular, it is surprising that even with a 5 nm thick chromium film, corrosion is observed with a corrosion area ratio of less than 0.1 inch, which shows that the method of improving weather resistance by coating with a chromium film of the present invention is an extremely excellent method. I understand.

Next, FIG. 1 shows an embodiment in which the present invention is applied to a magnetic disk medium. As shown in the figure, a N1-P electroless plating base 12 with a film thickness of 2 μm, for example, is formed on a disk substrate 1 made of an aluminum alloy or the like, and on top of this, a Cr base], a Go-Ni base, etc. Alloy, Co-Cr
A metal magnetic film 3 such as an alloy is formed, and a chromium film 4 is formed on top of it to ensure weather resistance.
In order to ensure high wear resistance, any wear-resistant protective film is coated, such as a 51o2 film or a carbon film. As mentioned above, a magnetic disk medium with high reliability could be obtained using the configuration of No. 1. Especially Kuro.

Membrane 41. The thickness of the protective film 5 is 10 nm, 2
Even with a protective film as thin as 1 circle and a total thickness of 30 nm, we were able to create a magnetic disk with excellent weather resistance and wear resistance.

Effects of the Invention According to the present invention, a magnetic recording medium with extremely excellent weather resistance and high reliability can be obtained.

In addition, the weather resistance is excellent even if the thickness of the weather-resistant protective film is thin, so the protective film on the metal magnetic film can be made thinner.
A magnetic head is placed on the surface of the metal matrix film.

By being able to get closer to each other, it is possible to achieve higher recording densities.

[Brief explanation of the drawing]

Fig. 1 is a top view of an embodiment of the magnetic disk of the present invention, and Fig. 2 is a graph showing the relationship between the thickness of the chromium film t on the Co--Ni metal magnetic film and the corrosion area rate. ! 1...substrate, 2...base film,
3... Metal magnetic film, = 4... Chrome film, 5... Protective film. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] A chromium film is formed on the metal magnetic film by physical vapor deposition (PVD) such as sputtering or vapor deposition, and a protective film is further attached on top of the chromium film, and the chromium film layer has an active metal chromium atomic layer. A magnetic recording medium characterized by the fact that it remains.