JPS6233322A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the deterioration of magnetic characteristics with age by providing an alloy magnetic layer in such a manner that the nickel content in the magnetic layer decreases stepwise from the magnetic layer in a magnetic recording medium toward the magnetic layer in the surface part. CONSTITUTION:The alloy magnetic layer formed on the surface part of the magnetic recording medium by optional means such as electroless plating consists of the easily oxidizable alloy of the compsn. which contains cobalt as an essential component and contains nickel at a low ratio. The alloy magnetic layer of the inside thereof is the alloy of cobalt contg. nickel at high ratio, i.e., the hardly oxidizable alloy. The alloy magnetic layer of the surface part is subjected to an oxidation treatment. The preferable nickel content to oxidize the alloy magnetic layer of the surface part is 10% and <=30% is required to make the inside alloy magnetic layer hardly oxidizable. The surface oxidation is thereby made easy and good scratch resistance is obtd; in addition, the deterioration of the magnetic characteristics with age is decreased.

Description

[Detailed description of the invention] [Industrial application field] The present invention provides a magnetic recording medium, Especially gold) 1! Thin film magnetic recording It is related to recording media.

[Conventional technology]

Conventional magnetic recording media have mainly been so-called coating-type magnetic recording media, in which a mixture of magnetic powder and a binder is coated on a tape- or sheet-shaped non-magnetic support. In this method, there was a problem from the viewpoint of recording density because the binder cannot be removed in principle by dispersing magnetic powder in the binder. On the other hand, in recent years, there has been a demand from various quarters to further improve recording density, and in order to do so, metal thin film type magnetism, in which a magnetic metal thin film is formed on a non-magnetic support, that is, there is no binder between magnetic materials, has been developed. Recording media are attracting attention. This metal thin film type magnetic recording medium records on a magnetic metal thin film with a thickness of 1 micron or less, and enables extremely high-density recording compared to the coating type.

However, metal thin film magnetic recording media have poor durability against long-term deterioration, impact, friction, etc.
In particular, there is a problem with scratch resistance. Much research has already been done to improve this scratch resistance. Among them, a method of oxidizing the surface of a magnetic recording layer containing cobalt to convert it into cobalt oxide (equity 4
2-20025) is known to be simple and highly effective.

[Problems that the invention attempts to address]

By the way, the above-mentioned magnetic recording type containing cobalt as a component is
Usually used as an alloy with other metals such as nickel,
However, when the alloy composition contains a large amount of nickel, the alloy magnetic layer is difficult to oxidize, and the objective of improving scratch resistance cannot be achieved. In addition, an alloy magnetic layer whose main component is cobalt and does not contain nickel can be quickly subjected to oxidation treatment, but in a magnetic recording medium whose surface portion is formed with this alloy magnetic layer, after manufacturing or Even after magnetic recording, oxidation tends to proceed further than necessary, resulting in deterioration of magnetic properties over time, which poses a problem in terms of reliability.

In view of the above points, the present invention has excellent scratch resistance,
It is an object of the present invention to provide a magnetic recording medium whose magnetic properties are less likely to deteriorate over time and which are capable of high-density recording.

[Failure to solve the problem]

In the magnetic recording medium of the present invention, in order to achieve the above object, the alloy compositions of the alloy magnetic layer in the surface portion and inside are changed. That is, in the magnetic recording medium of the present invention, the alloy magnetic layer on the surface is formed of an easily oxidized alloy containing cobalt as a main component and a small amount of nickel by any means such as electroless plating, and the inner alloy magnetic layer is made of an alloy with cobalt that contains more nickel than the surface portion, that is, an alloy that is difficult to oxidize, and the alloy magnetic layer on the surface portion is oxidized.

The preferred nickel content is 10% or less in order to oxidize the alloy magnetic layer on the surface, and 50% or more is considered to be necessary in order to make the inner alloy magnetic layer difficult to oxidize.

〔Example〕

Example 20 A 5-inch aluminum disk substrate with a nickel-phosphorus nonmagnetic layer of MikuPn was degreased and acid-activated, and then subjected to the following four steps of electroless plating. g) Forming 4 layers of magnetic layers.

Process 1 Plating bath A 3 minutes Process 2 Plating bath B 30 seconds Process 3 Plating bath 0 20 seconds Process 4 Plating bath D 20 seconds However, other plating conditions were kept constant at pH = &5 and liquid temperature 70°C. The liquid composition is as shown in Table 1.

The obtained product was placed in a constant temperature and humidity chamber at 60°C.
Oxidation treatment was performed at 90% RH for 48 hours, and this was used as a sample for the example.

Comparative Example 1 After performing the same pretreatment as in the previous example, electroless plating was performed for 4 minutes using plating bath A listed in Table 1.
Formed a sexual layer.

The round pieces thus obtained were subjected to oxidation treatment in the same manner as in the examples.

Comparative Example 2 After performing the same pretreatment as in the previous example, electroless plating was performed for 4 minutes using the plating bath listed in Table 1 to form a magnetic layer.

The product thus obtained was subjected to oxidation treatment in the same manner as in the examples.

Comparative Example 3 After performing the same pretreatment as in the previous example, electroless plating was performed for 3 minutes using plating bath A listed in Table 1, and then electroless plating was performed for 1 minute using the plating bath. Plating was performed to form a double magnetic layer.

The product thus obtained was subjected to oxidation treatment in the same manner as in the examples.

Comparative Example 4 After performing the same pretreatment as in the previous example, plating bath A listed in Table 1 was used! Electroless plating was performed for 5 minutes, and then electroless plating was performed for 20 seconds using a plating bath to form a double magnetic layer.

The product thus obtained was subjected to oxidation treatment in the same manner as in the examples.

Figures 1a-e are schematic diagrams of five alloy magnetic layers produced as described above. In the figure, A1, B', c l, D
f represents the magnetic layer formed by plating baths A, B, C, and D, respectively.

Durability Test A durability test was conducted on five oxidized samples obtained from Examples and Comparative Examples 1 to 4.

First, a scratch test was conducted on the above five samples by hand using a VHS video head.

In addition, after measuring the magnetic properties of the five samples subjected to the oxidation treatment,
'The oxidation treatment was carried out at LH for 72 hours, and then the magnetic properties were measured again. From the changes in the magnetic properties in these two measurements, the aging [1] deterioration of the alloy magnetic layer was estimated.

These results are shown in Table 2.

Table 2 Durability test results The magnetic properties were measured using VSM (manufactured by Toei Kogyo Co., Ltd.).

In this way, in the samples obtained from the examples,
The results showed that the durability against both the scratch test and the change in magnetic properties over time was excellent.

〔Effect of the invention〕

Since the magnetic recording medium of the present invention has the above configuration,
The alloy magnetic layer on the surface is easily oxidized, and the inner alloy magnetic layer is difficult to oxidize. Therefore, this magnetic recording medium has the advantage that surface oxidation is easy, good scratch resistance can be obtained, and magnetic properties are less likely to deteriorate over time.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an alloy magnetic layer in an example of a magnetic recording medium of the present invention and a comparative example thereof, where a is an example of the present invention and b, e, d, and e are comparative examples. Figure 1 a b c d e

Claims (2)

[Claims] (1) In a magnetic recording medium having an alloy magnetic layer containing cobalt and nickel, the alloy magnetic layer has at least three layers, and the nickel content in the magnetic layer is lower than that of the magnetic recording medium. 1. A magnetic recording medium, characterized in that the alloy magnetic layer is provided so as to be gradually smaller from the inner magnetic layer to the surface magnetic layer, and the alloy magnetic layer on the surface is oxidized. (2) The magnetic recording medium according to claim 1, wherein the alloy magnetic layer of the magnetic recording medium is formed by electroless plating.