JPH08335309A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To provide a magnetic recording medium excellent in magnetic characteristics as well as corrosion resistance. CONSTITUTION: A metallic magnetic thin film consisting of Co, Ni and 0 is formed on a nonmagnetic substrate 2. The concn. ratio between Co and Ni elements in the thin film is represented by the relational formula Co1-x Nix (where X<=0.15) and the ratio of Co as oxide to metal Co is higher than that of Ni as oxide to metal Ni.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic card and a magnetic disk, and more particularly to a magnetic recording medium having a Co--Ni--O magnetic thin film.

[0002]

2. Description of the Related Art Co-based thin film magnetic recording media are suitable for high density recording, but they are significantly inferior to conventional coating type magnetic recording media in terms of reliability such as durability and corrosion resistance. There is an urgent need for improvement. As a method of improving the corrosion resistance, there is a method of including a metal having excellent corrosion resistance in the magnetic film, and Co-containing Ni added for the purpose of improving the corrosion resistance.
Research and development of Ni—O based magnetic thin films have been advanced, and various proposals have been made.

[0003]

The value of X of Co _1-X Ni _{X in} the Co-Ni-O system magnetic thin film which has been studied conventionally is 0.2 or more (for example, 0.25).
In addition, as a gas to be introduced during vapor deposition, oxygen gas alone or a mixed gas of oxygen and nitrogen dioxide (for example, O 2
₂ : NO ₂ = 1: 2 mixed gas) was used.

However, according to the results of various studies by the present inventors, as described above, the Ni concentration in the magnetic film is high as described above, or (and) the gas introduced during vapor deposition is as described above. If you use a gas with strong oxidizing power,
The magnetic properties are not necessarily excellent, because they have a problem that they adversely affect the magnetic properties and cause a decrease in anisotropic magnetic field and eventually a decrease in coercive force.

The present invention has been made based on such a background, and an object thereof is to provide a magnetic recording medium excellent in corrosion resistance and magnetic characteristics at the same time.

[0006]

In order to achieve the above object, the present invention is directed to a magnetic recording medium provided with a metal magnetic thin film made of Co, Ni and O on a non-magnetic substrate.

The value of X in the relational expression Co _1-X Ni _X showing the concentration ratio of the Co element and the Ni element in the metal magnetic thin film is 0.15 or less and the oxide Co with respect to the metal Co is Co. Is larger than the ratio of oxide Ni to metal Ni, that is, oxide Co / metal Co>
It is characterized by having a relationship of oxide Ni / metal Ni.

[0008]

According to the present invention, as described above, Co,
In a magnetic recording medium on which a metal magnetic thin film made of Ni and O is formed, the value of X in the formula of Co _1-X Ni _X is 0.
By restricting it to 15 or less, the Ni concentration in the magnetic film can be kept low, and by preferentially oxidizing Co with respect to Ni, the Ni concentration in the metal part can be made slightly higher to improve corrosion resistance and magnetic properties at the same time. I was able to.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a continuous winding type vacuum vapor deposition apparatus for manufacturing a magnetic recording medium according to the present invention.

In the vacuum vapor deposition tank 1, a non-magnetic flexible substrate 2 such as a polyethylene terephthalate (PET) film is wound from the unwinding roll 3 along the coating drum (can roll) 4 to the winding roll 5.
Run so that it winds up.

On the other hand, an electron beam 7 emitted from an electron gun 6 is irradiated toward the inside of the crucible 8 to produce Co--N having various compositions.
The ferromagnetic metal 9 made of i alloy is heated and melted to evaporate,
A magnetic layer is continuously deposited on the substrate 2 within the range regulated by the shield plate 10. Further, gas is introduced into the vapor deposition atmosphere by the gas introduction nozzle 11.

A more specific description is as follows. (Example 1) Using a continuous vapor deposition apparatus as shown in FIG. 1, a Co-Ni-O-based magnetic thin film having a thickness of 200 was formed on a substrate 2 made of a polyethylene terephthalate film having a thickness of 10 μm.
A sample was prepared by oblique vapor deposition so as to be 0Å. The gas introduced into the atmosphere contains N in order to moderate the oxidizing power.
Using a mixed gas of ₂ : O ₂ = 5: 1, a tape-shaped magnetic recording medium was produced in which Co was preferentially oxidized with respect to Ni.

The elemental composition in the magnetic film at this time is Co85.
%, Ni 15%, that is, the value of X in the formula of Co _1-X Ni _X is 0.15, and the concentration ratio of the oxide and the metal examined by Auger electron spectroscopy is oxide Co / metal Co =
0.2, oxide Ni / metal Ni = 0.07, and the relationship is oxide Co / metal Co> oxide Ni / metal Ni.

(Example 2) The elemental composition of the magnetic film was Co9.
A magnetic recording medium was prepared in the same manner as in Example 1 except that 5%, Ni 5%, that is, Co _1-X Ni _X was vacuum-deposited so that the value of X was 0.05.

At this time, the concentration ratio of the oxide and the metal examined by Auger electron spectroscopy is oxide Co / metal Co =
0.14, oxide Ni / metal Ni = 0, and in the end, the relationship is oxide Co / metal Co> oxide Ni / metal Ni.

(Comparative Example 1) NO ₂ and O ₂ with strong oxidizing power were added to the gas introduced during vapor deposition in Example 1 as NO ₂ : O ₂ =
A magnetic recording medium was manufactured in the same manner as in Example 1 except that the magnetic recording medium was used in the ratio of 2: 1. At this time, the ratio of oxide and metal examined by Auger electron spectroscopy was almost the same for Co and Ni, and was about 0.
18, that is, the value of X in the formula of Co _1-X Ni _X is 0.1
However, the relationship is oxide Co / metal Co = oxide Ni / metal Ni.

Comparative Example 2 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the elemental composition of the sample in Example 1 was changed to 75 atomic% Co and 25 atomic% Ni.

That is, in this comparative example, the relation of oxide Co / metal Co> oxide Ni / metal Ni is satisfied.
The value of _{X in} the formula of o _1-X Ni _X is as high as 0.25.

The gas flow rates were controlled so that the saturation magnetizations were almost the same in the above-mentioned Examples and Comparative Examples.

Saturation magnetization and coercive force of the sample prepared as described above were measured, and further measured at 60 ° C. and 90% RH for 16 minutes.
A corrosion test was performed for 8 hours, and the corrosion resistance was evaluated from the deterioration rate of saturation magnetization. The results of these evaluations are shown in Table 1 below.

Table 1  Saturation magnetization (G) Coercive force (Oe) Saturation magnetization deterioration rate (%)  Example 1 435 1420 3.0 Example 2 445 1480 4.8 Comparative Example 1 425 1500 500 8.0 Comparative Example 2 430 1030 2.7   As is clear from the results in Table 1, the magnetic properties of Comparative Example 1 were
Ni concentration in the film is low, but oxide Co / metal Co = oxide
Since there is a Ni / metal Ni relationship, the deterioration rate of saturation magnetization is
It is 8% and the corrosion resistance is not sufficient. On the other hand, in Comparative Example 2, acid
Compound Co / metal Co> oxide Ni / metal Ni
However, due to the high Ni concentration in the magnetic film, a sufficient coercive force can be obtained.
I can't get it. Although not shown in this table, conventional magnets
The Ni concentration in the magnetic film is high like in a magnetic recording medium, and
When a gas with strong oxidizing power is introduced, coercive force and corrosion resistance
Is bad.

On the other hand, according to the present invention, Co _1-X
The value of _{X in} the formula of Ni _x is 0.15 or less, and the relationship of oxide Co / metal Co> oxide Ni / metal Ni, that is, by preferentially oxidizing Co with respect to Ni,
Excellent in both corrosion resistance and magnetic properties.

From the results of various experiments conducted by the present inventors, if the Ni concentration in the metal magnetic thin film is too low, a sufficient effect of improving the corrosion resistance cannot be obtained. Therefore, the lower limit of the X value in the formula Co _1-X Ni _X is It is better to set it to 0.05.

In the above embodiment, the case of the magnetic tape has been described, but the present invention is also applicable to other forms of magnetic recording media such as a magnetic disk. When the present invention is applied to the magnetic disk as described above, the magnetic layer may be formed by vapor deposition while rotating the substrate in the vacuum vapor deposition apparatus. At this time, by rotating the substrate a plurality of times (for example, three times), a magnetic layer having a multilayer structure (for example, three-layer structure) can be formed.

[0026]

As described above, the present invention provides a magnetic recording medium in which a metal magnetic thin film made of Co, Ni and O is formed on a non-magnetic substrate, and the value of X in the formula Co _1-X Ni _X Is controlled to 0.15 or less to suppress the Ni concentration in the magnetic film to a low level, and Co is preferentially oxidized with respect to Ni to slightly increase the Ni concentration in the metal part.
A magnetic recording medium having excellent corrosion resistance and magnetic properties can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a continuous winding type vacuum evaporation apparatus for manufacturing a magnetic recording medium according to the present invention.

[Explanation of symbols]

 1 vacuum deposition tank 2 substrate 3 unwinding roll 4 coating drum 5 winding roll 6 electron gun 7 electron beam 8 crucible 9 ferromagnetic metal 10 shielding plate 11 gas introduction nozzle

Claims (2)

[Claims] 1. A magnetic recording medium in which a metal magnetic thin film made of Co, Ni and O is provided on a non-magnetic substrate, and a relational expression Co _{1 -X} showing the concentration ratio of Co element and Ni element in the metal magnetic thin film. A magnetic recording medium, wherein the value of _{X in} the formula of Ni _x is 0.15 or less, and the ratio of oxide Co to metal Co is larger than the ratio of oxide Ni to metal Ni. 2. The magnetic recording medium according to claim 1, wherein the value of X is 0.05 or more.