JPH05258299A - Production of magnetic disk medium - Google Patents

Abstract

PURPOSE:To promote the intrasurface orientation of grains in a magnetic film formed by electroless plating method and to improve the coercive force of a magnetic disk medium forming this magnetic film. CONSTITUTION:A base layer of a NiP alloy layer 2 is formed on an aluminum substrate 1, on which a NiP oxide of hydroxide film 3 is formed, and further a magnetic film layer 4 is formed by electroless plating. The NiP oxide film 3 is treated with an acid to be left as spots on the aluminum substrate 1 to limit points for generation of nucleus. The growth of the magnetic film layer 4 is promoted from these nucleus generating points to inactive areas for plating and to give intrasurface orientation. Thereby, the obtd. magnetic film layer 4 has high coercive force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic disk medium mounted on a magnetic disk device, and more particularly to a method for manufacturing a magnetic disk medium which has a high coercive force of a magnetic film layer by electroless plating.

[0002]

2. Description of the Related Art In recent magnetic disk media, a thin film magnetic disk medium using a magnetic thin film formed by a plating method, a sputtering method, an evaporation method or the like as a magnetic recording layer has become mainstream in order to achieve a high recording density. is there. The magnetic characteristics of such a thin film magnetic disk medium are as follows: residual magnetic flux density: Br = 8000 to 10000 [Gauss], coercive force:
High values of Hc = 1000 to 2000 [Oersted] have appeared.

A thin film magnetic disk medium (hereinafter referred to as a plating medium) in which a magnetic film is formed by a plating method has been mass-produced from an early stage due to its excellent mass productivity. Is required to improve.

FIG. 2 is a schematic sectional view showing an example of a conventional typical plating medium. As shown in FIG. 2, the conventional plating medium has a NiP alloy layer 12 on an aluminum substrate 11.
Is formed on the underlayer, and the magnetic film layer 13 is formed on the underlayer by electroless plating. And the magnetic film layer 1
The protective film layer 14 and the lubricating film layer 15 are sequentially formed on the surface of No. 3.

[0005]

In the above-mentioned conventional plating medium, the NiP alloy layer is used as the underlayer.
It is not always possible to increase the coercive force. The reason for this is
This is because, when the magnetic film layer is formed on the NiP alloy layer by the electroless plating method, the nucleation reaction occurs preferentially, the nuclear growth reaction is suppressed, and the magnetic film grows isotropically. A plating medium having a coercive force of Hc = 1500 [Oersted] or higher has not been reported yet.

Therefore, in order to increase the coercive force of the plating medium, it is necessary to orient the crystal in a direction parallel to the surface of the plating medium for crystal growth. However, there is a drawback that this technique cannot be easily achieved.

[0007]

The present invention provides a magnetic disk medium in which an underlayer made of a NiP alloy layer is formed on an aluminum substrate and a magnetic film layer is formed on the underlayer by electroless plating. An oxide film or a hydroxide film is formed on the formation. Next, after a part of the oxide film or the hydroxide film is removed by acid treatment and scattered, a magnetic film layer is formed thereon.

The oxide film may be formed on the surface of the underlayer by a thermal oxidation method, or a hydroxide film may be formed on the surface of the underlayer by immersing it in an alkaline treatment solution.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of the present invention. As shown in FIG. 1, the magnetic disk medium of this embodiment has a NiP alloy layer 2 and a NiP alloy layer on an aluminum substrate 1.
The oxide film 3, the magnetic film layer 4, the protective film layer 5, and the lubricating film layer 6 are sequentially formed. That is, the structure is such that an oxide film layer is formed between the NiP alloy layer 12 and the magnetic film layer 13 in the conventional plating medium described with reference to FIG.

In the magnetic disk medium of this embodiment, first, the NiP alloy layer 2 is formed on the aluminum substrate 1 by electroless plating to have a film thickness of about 15 μm. Next, temperature 150
NiP is used to oxidize the surface by firing under the conditions of ℃ and 1 hour.
The oxide film 3 is formed. Then, this is immersed in a 3% sulfuric acid solution to remove a part of the oxide film layer 3. That is, N
NiP oxide films 3 are scattered on the iP alloy layer 2. Also,
The NiP alloy layer 2 may be dipped in an alkaline treatment liquid, and a hydroxide film may be formed on the surface thereof instead of the NiP oxide film 3.

Next, an electroless plating solution having the composition shown in Table 1 is used to perform plating on the upper portion to form the magnetic film layer 4.

[0013]

[Table 1]

This electroless plating is inactive with respect to the NiP oxide film 3 or the hydroxide film and limits the nucleation sites. Since nuclei grow from this nucleation site toward the plating inactive site, in-plane crystal orientation is promoted. Therefore, it is desirable that the NiP oxide film 3 or the hydroxide film is scattered in the plane, and if it is uniform, an acid treatment is carried out to remove a part of the film. Further, when the density of the scattered NiP oxide film 3 or hydroxide film is low, a portion where plating is not deposited is formed, and therefore it is necessary to control by acid treatment.

Next, a solution in which a silicon low polymer is dispersed in isopropyl alcohol is applied on the magnetic film layer 4 and baked at a temperature of 290 ° C. for 1 hour to form a protective film layer 5 of SiO 2. Further, a fluorine-based liquid lubricant (for example, perfluoropolyether) is applied to the upper part of the film to form the lubricating film layer 6.

Table 2 shows the coercive force of the plating medium thus obtained. For comparison, the values when the conventional oxide film is not formed are also shown.

[0017]

[Table 2]

According to Table 2, the plating medium of this embodiment is
It is clear that the coercive force is improved as compared with the conventional plating medium.

As described above, according to the present invention, an oxide film or a hydroxide film is formed on a base layer made of a NiP alloy layer, and a part of the oxide film or the hydroxide film is removed by an acid treatment to be scattered. By forming the magnetic film layer on the
The in-plane orientation can be promoted by giving priority to the nucleus growth reaction of the magnetic film layer, and a magnetic disk medium having a high coercive force can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a conventional example.

[Explanation of symbols]

 1,11 Aluminum substrate 2,12 NiP alloy layer 3 NiP oxide film 4,13 Magnetic film layer 5,14 Protective film layer 6,15 Lubricating film layer

Claims (3)

[Claims] 1. A magnetic disk medium in which an underlayer made of a NiP alloy layer is formed on an aluminum substrate, and a magnetic film layer is formed on the underlayer by electroless plating. An oxide film or water is formed on the underlayer. A magnetic disk medium characterized by forming an oxide film, subsequently removing a part of the oxide film or the hydroxide film by acid treatment to make them scattered, and then forming the magnetic film layer thereon. Manufacturing method. 2. The method of manufacturing a magnetic disk medium according to claim 1, wherein the oxide film is formed on the surface of the underlayer by a thermal oxidation method. 3. The method of manufacturing a magnetic disk medium according to claim 1, wherein the hydroxide film is formed on the surface of the underlayer by dipping an alkali treatment liquid.