JPH01102723A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent corrosion resistance by interposing an insulating film between a thin ferromagnetic metallic film layer and inorg. protective film. CONSTITUTION:The insulating protective film 40 is interposed between the thin ferromagnetic metallic film 30 and the inorg. protective film 50. The galvanic reaction between the protective film 50 of Ni and the thin ferromagnetic film 30 of Co is conceivably suppressed by the presence of the insulating film 40, by which the corrosion resistance is improved. The insulating film can be constituted of, for example, SiO2, etc., and other materials, for example, polyethylene, alumina, etc., are usable for forming the insulating film. The insulating film has preferably the thickness ranging about 30-300Angstrom . The corrosion resistance is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film magnetic recording medium. For details on the history,
The present invention relates to a thin film magnetic recording medium having a protective film with improved corrosion resistance.

[Prior Art] Magnetic recording media that have been commonly used in the past are magnetic recording media that are coated with a magnetic coating mainly consisting of acicular magnetic powder and a polymeric binder on a non-magnetic substrate to form a magnetic layer. This is a type of magnetic recording medium.

Currently, there is a trend toward higher density magnetic recording and reproducing devices, and there is a demand for magnetic recording media with excellent short wavelength recording characteristics.

However, there are limits to the improvement of short wavelength recording characteristics in coated magnetic recording media. On the other hand, Co+ CoNi
, CoN1P, CoCr, and other Co-based ferromagnetic materials are formed on a nonmagnetic substrate by so-called physical vapor deposition methods such as vacuum evaporation, sputtering, or ion blating. Since no non-magnetic binder is mixed in the layer, it is extremely high [
? Since the magnetic flux density can be obtained and the magnetic layer can be formed extremely thin, it has the advantage of high output and excellent short wavelength response. Due to this feature, thin film magnetic recording media have recently become the mainstream of magnetic media.

Although thin-film magnetic recording media have a high magnetic recording density and excellent short-wavelength recording characteristics, cobalt is relatively easily corroded.
However, the corrosion resistance is poor because the magnetic layer is exposed.
It has the disadvantage of being susceptible to magnetic deterioration, which is a serious problem in practical use.

In order to solve this problem, for example, the magnetic layer L is made of Ti.
Although it has been proposed to provide a protective layer of , Cr, etc., corrosion resistance has not been sufficiently improved. In particular, there was a problem in corrosion resistance against corrosive gases such as 802.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the drawback of the above-mentioned prior art, which is that it is susceptible to corrosive gases, and thereby provide a magnetic recording medium with excellent corrosion resistance. .

[Means for Solving the Problems] As a result of extensive experiments and prototype production carried out by the present inventors over many years, we added a ferromagnetic metal thin film E whose main component is Co to a specific atomic ratio characterized by Ni. It has been discovered that when providing an inorganic protective film, interposing an insulating film between the ferromagnetic metal thin film layer and the inorganic protective film significantly improves the corrosion resistance of the magnetic recording medium. The present invention was completed based on this knowledge.

FIG. 1 shows the cross-sectional structure of the magnetic recording medium of the present invention. In the figure, 20 is a nonmagnetic substrate, 30 is a Co-based ferromagnetic metal thin film (magnetic film), 40 is an insulating film, and 50 is a Ni-based inorganic protective film.

Corrosion resistance can be improved to some extent by providing an inorganic protective film containing Ni as a main component on a ferromagnetic metal thin film containing Co as a main component, but with this alone, Co
is corroded and inadequate.

However, excellent corrosion resistance can be obtained by providing an insulating thin film between the ferromagnetic metal thin film and the inorganic protective film.

Although the exact mechanism has not yet been elucidated and is still in the realm of speculation, it is thought that the presence of the insulating film suppresses the battery reaction between the Ni protective film and the Go ferromagnetic thin film, improving corrosion resistance. It will be done.

The insulating film can be made of, for example, SiO2. Other materials, such as polyethylene, alumina, etc., can also be used to form the insulating film of the present invention.

The thickness of the insulating film itself is not an essential requirement of the present invention.

As a general guideline, it is preferable that the insulating film has a thickness within a range of approximately 30 to 300 thicknesses.

It is difficult to form an insulating film having a uniform thickness distribution with a thickness of 30 people. On the other hand, if the thickness exceeds 300, problems such as spacing loss will occur, which is not preferable.

In addition, the oxygen concentration of the protective film containing Ni as the main component was set to 15 to 5.
By setting the content to 0 at%, excellent wear resistance can be obtained. Below 15at%, it is soft <, 50at%
If it exceeds %, it becomes brittle and wear resistance deteriorates.

Furthermore, the atomic ratio of Fe/Ni+Fe in the protective film is 0°05~
Even better corrosion resistance can be obtained if Fe is included so that the amount of Fe is 0.4. When the atomic ratio of Fe exceeds 0.4, wear resistance decreases even within the above oxygen concentration range.

The ferromagnetic thin film in the magnetic recording medium of the present invention is made of Co or a Co alloy, and in the case of a Co alloy, it contains more than 50% Co. Co alloys suitable for magnetic films of magnetic recording media are well known to those skilled in the art.

The ferromagnetic metal thin film, the insulating film, and the Ni protective film can be formed by the thin paper deposition method. ′
"Vapor nib position method" means a method in which a substance or compound to be deposited is deposited on the gas as vapor or ionized vapor in a gas or vacuum space.This method includes vacuum evaporation, ionization, Brating method.

High frequency ion brating method, ion cluster beam method, ion beam deposition method.

Examples include sputtering method and CVD method. Each film can be formed by either oblique or vertical deposition.

Examples of the nonmagnetic substrate used in the magnetic recording medium of the present invention include polymer films such as polyimide and polyethylene terephthalate, glasses, and ceramics.

Metal plates such as aluminum, anodized aluminum, brass, Si? 1
There is a Si single crystal plate whose surface is thermally oxidized. This non-magnetic substrate may be provided with a base polishing layer such as a nickel-phosphorus alloy layer or an alumite treatment layer for surface polishing or texturing, if necessary.

In addition, as magnetic recording media, polyester film,
Magnetic tapes and magnetic disks whose bases are made of synthetic resin films such as polyimide films, magnetic disks and magnetic drums whose bases are disks and drums made of synthetic resin films, aluminum plates, glass plates, etc., which have a structure that makes sliding contact with the magnetic head. It includes various forms.

[Example] The present invention will be explained in more detail below using Example f1.

Real part [ A magnetic recording medium was produced using an apparatus as shown in FIG.

Polyethylene terephthalate film (10 μm thickness) 5
First, CoN i (80-20) is added in a vacuum chamber l.
After creating a vapor-deposited magnetic film (thickness: 1500) at a minimum incidence angle of 50° and an oxygen introduction rate of 200 ml/min, vacuum chamber 2
A silicon oxide insulating film (thickness: 100 mm) was created by sputtering in the vacuum chamber 3, and N i Fe was added in the vacuum chamber 3.
(80-20) A vapor-deposited protective film (thickness: 100) was prepared at a minimum incident angle of 50° and an oxygen introduction rate of 100 ml/min to obtain a magnetic recording medium.

Tsunetane Takumi 1 A magnetic recording medium was produced in the same manner as in Example 1 except that the amount of oxygen introduced during NiFe deposition was 200 ml/min.

A magnetic recording medium was produced in the same manner as in Example 1, except that the amount of oxygen introduced during NiFe deposition was 50 ml/n+in.

Actual weight 1 The amount of oxygen introduced during NiFe evaporation is 400 a+I/l1i
A magnetic recording medium was produced in the same manner as in Example 1 except that n was used.

A magnetic recording medium was produced in the same manner as in Example 1 except that the amount of oxygen introduced during NiFe deposition was omitted.

Point five beard 1 N i F e (80-20), N i F
A magnetic recording medium was produced in the same manner as in Example 1 except that e (95-5) was used.

【Actual】1 1- N i Fe (8G-20), N i F
A magnetic recording medium was produced in the same manner as in Example 1 except that e (llio-40) was used.

Real 11 Masu J, instead of N i Fe (8G-20), N i (
A magnetic recording medium was produced in the same manner as in Example 1 except that the magnetic recording medium was changed to 100).

Real I (instead of N i Fe (80-20), N i F
A magnetic recording medium was produced in the same manner as in Example 1 except that e (40-GO) was used.

Kitakami n A magnetic recording medium was manufactured in the same manner as in Example 1 except that the formation of the silicon oxide insulating film was omitted.

A magnetic recording medium was produced in the same manner as in Example 1, except that the preparation of the ratio MA 2-N i Fe (80-20) protective film was omitted.

Stopping Prevention 1 A magnetic recording medium was produced in the same manner as in Example 1, except that the silicon oxide insulating film and the NiFe protective film were omitted.

Regarding each magnetic tape produced as described below,
Oxygen and F in the NiFe protective film were determined by Auger electron spectroscopy.
The concentration of e was measured. In addition, in order to evaluate the corrosion resistance of each magnetic tape, the tape was treated with 5020.5 ppm NO2O,
5ppm, 8200.25ppm.

5. Exposure to 35°C, 975% RH atmosphere for 40 hours.
10. After 20 and 40 hours, the surface was observed using an optical microscope to check for pitting corrosion. Furthermore, the still time (time until the +17 raw output drops to 1/2 of the initial value using a VH8 type VTR) of each magnetic tape was measured. The measurement results are summarized in Table 1 below.

Table 1 As is clear from the above results, by interposing an insulating film between the co-based extrinsic film and the Ni-based protective film, the corrosion resistance of the magnetic recording medium can be significantly improved.
Oxygen and Fe in the Ni-based protective film are each 0.15≦O
/Ni+Fe+O≦0.50゜0.05≦Fe/Ni+
By setting Fe≦0.40, excellent corrosion resistance and wear resistance can be obtained.

[Effects of the Invention] As explained above, according to the present invention, by interposing an insulating protective film between a ferromagnetic metal thin film and an inorganic protective film, specific oxygen and Fe atoms can be used as an inorganic protective film. By using a Ni-based protective film of the same ratio, a magnetic recording medium with excellent corrosion resistance and wear resistance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the structure of the magnetic recording medium of the present invention, and FIG. 2 is a schematic diagram showing an example of an apparatus used for manufacturing the magnetic recording medium of the present invention.

Claims (5)

[Claims] (1) A magnetic recording medium having a ferromagnetic thin film and an inorganic protective film on a non-magnetic substrate, characterized in that an insulating protective film is interposed between the ferromagnetic thin film and the inorganic protective film. Medium. (2) Magnetic recording according to claim 1, characterized in that the inorganic protective film contains Ni as a main component among all elements except oxygen, and contains oxygen in a range of 15 to 50 at%. Medium. (3) The inorganic protective film has an atomic ratio of Fe/Ni+Fe of 0.0
3. The magnetic recording medium according to claim 1, wherein Fe is contained in a range of 5 to 0.4. (4) The magnetic recording medium according to claim 1, wherein the insulating protective film is made of SiO_2. (5) The magnetic recording medium according to claim 1, wherein the ferromagnetic thin film contains Co as a main component.