JPS6057131B2 - Manufacturing method for high recording density magnetic disks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of manufacturing a high recording density magnetic disk.

[Background of the invention]

In the production of high recording density magnetic disks using thin film magnetic materials formed by plating, the thickness of the magnetic plating layer electrodeposited on the non-magnetic underlayer is on the order of 10008 or less. It has been found that when , the resulting magnetic material is highly susceptible to dispersion and of low quality.

This decrease in quality, namely the decrease in coercive force, the squareness ratio (Br
/Bm) is thought to be caused by the fact that magnetic plating is affected by the underlying surface structure. In order to eliminate this effect, ie, interaction, and obtain a high quality magnetic thin film with excellent magnetic properties, various intermediate plating layers have been investigated. For this purpose, a nickel-tin alloy plated layer has traditionally been used as the intermediate layer. Although this intermediate layer itself is nonmagnetic at room temperature, it has the effect of improving the magnetic properties of the magnetic film electrodeposited thereon. In other words, when comparing the characteristics of the magnetic layer when the magnetic layer is formed directly on the processed surface of the base layer of the magnetic disk by plating, and when the magnetic layer is formed by plating on the intermediate layer, the latter is better than the former. Improvements include an increase in magnetic force, (2) an increase in residual magnetization, (3) an increase in squareness ratio, and (4) a decrease in noise. Because of this improvement in magnetic properties, recording properties can also be improved, resulting in improved output and resolution.
However, a nickel layer is interposed between the nickel-tin alloy plating layer and the aluminum alloy substrate.

There was a problem in the adhesion of this nickel layer to the aluminum alloy substrate, and there was a risk that the nickel layer would peel off during use, and as a result, the magnetic layer would also peel off from the substrate (Japanese Patent Laid-Open No. 47-22706). [Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a high recording density magnetic disk that is free from the risk of peeling of the magnetic layer from the aluminum alloy substrate during use.

[Summary of the invention]

In order to achieve the above object, the surface of the aluminum alloy substrate is made flat and smooth, and this flat and smooth substrate surface is subjected to zinc substitution treatment to form a zinc substitution surface treatment layer, and this zinc substitution surface is A copper layer is formed on the treated layer, a base layer made of any one of a copper-tin alloy, a copper-zinc alloy, a nickel-phosphorus alloy, and a copper-nickel alloy is formed on the copper layer; The substrate on which the copper layer and the base layer have been formed is heat-treated, the top layer surface of the heat-treated substrate is made flat and smooth, and an intermediate layer made of a nickel-tin alloy is formed on the flat and smooth top layer. However, this is achieved by forming a magnetic layer on this intermediate layer and forming a protective layer on this magnetic layer.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples.

Example 1 The surface of a disk-shaped substrate 1 made of a corrosion-resistant aluminum alloy and having a diameter of 356mm and a thickness of 2mm was machined to have a flat and smooth surface.

This flat, smooth surface was treated with zinc substitution to a thickness of 0.5 μm.
A surface treatment layer 2 of m was formed. On top of this, to improve adhesion, copper strike plating is applied as a pretreatment layer to a thickness of 4 μm.
A copper layer 3 of m thickness was formed. Next, this disc was
- Copper that is placed in an electroplating bath characterized by using a perforated cutting board and an auxiliary cathode as described in 9447, has a uniform plating layer on the surface, and has little bulging at the outer peripheral edge. - Tin alloy plating was performed to obtain a base layer 4 made of a copper-tin alloy. The thickness of this base layer 4 was 30 to 40 microns. Next, in order to stabilize the properties of the substrate, the copper layer, and the underlayer made of the copper-tin alloy, heat treatment was performed at 320° C. for 1 hour, and then the surface of the underlayer 4 was mechanically polished. The purpose of this process is to create a flat, smooth, and defect-free base plated surface. This is because the recording density is 20
To obtain a plated disk of 000BpI or more, the recording medium thickness must be 0.1μ or less, and the spacing between the head and the disk must be 0.5μ or less, so the surface of the disk must be highly flat. This is because support, smoothness, and defect-free properties are required. Through this polishing process, the surface of the base layer made of copper-tin alloy has a surface roughness of 0.005 μm.
Ra, straightness (radial direction) 1.5μ/70Tn, diameter 2
The machined surface had no defects larger than μm. Next, an intermediate layer 5 made of a nickel-tin alloy plating layer with a thickness of 0.1μ is formed on this using the plating bath shown in Table 1, and then a plating bath shown in Table 2 is formed. A magnetic layer 6 made of cobalt-nickel alloy plating was formed using the following methods. Finally, a protective layer 7 was formed to obtain the high recording density magnetic disk shown in the figure. Table 3 shows the measurement results of magnetic properties and recording properties.
Example 2 A high recording density magnetic disk was manufactured in the same manner as in Example 1 except that the thickness of the magnetic layer 5 made of cobalt-nickel alloy was changed, and changes in coercive force were observed, and the results shown in Figure 2 were obtained. I got it.

Intermediate layer 5 consisting of a nickel-tin alloy plating layer
As shown in FIG. 2, the intermediate layer 5 has the effect of increasing the coercive force of the magnetic layer compared to the one without the intermediate layer (FIG. 2, 9), and the magnetic layer in actual use. It has been found that the dependence of the coercive force on the layer thickness becomes smaller when the thickness is between 0.1 and 0.2 μm, and there is a manufacturing advantage in that the range of variation in the coercive force due to variations in the magnetic layer thickness can be reduced. Example 3 Underlayer 4 is made of copper-zinc alloy, nickel-phosphorus alloy, copper-
A high recording density magnetic disk was manufactured in the same manner as in Example 1 except that it was made of one of the nickel alloys.

The same results as in Example 1 were obtained in these cases as well. [Effects of the Invention] As described above, according to the present invention, a high-output, high-resolution, low-noise, high-recording-density magnetic disk with a recording density of 20,000 BPI, in which the magnetic film does not peel off from the base during use, can be obtained. .

[Brief explanation of the drawing]

The figure is a cross-sectional view of a high recording density magnetic disk. DESCRIPTION OF SYMBOLS 1...Disk-shaped base, 2...Surface treatment layer, 3...Copper layer, 4...Underlayer, 5...
. . . Intermediate layer, 6 . . . Magnetic layer, 7 . . . Protective layer.

Claims (1)

[Claims] 1 The surface of an aluminum alloy substrate is made flat and smooth, this flat and smooth substrate surface is subjected to zinc substitution treatment to form a surface treatment layer, a copper layer is formed on this surface treatment layer, and a copper layer is formed on this copper layer. A base layer made of any one of a tin alloy, a copper-zinc alloy, a nickel-phosphorus alloy, or a copper-nickel alloy is formed, and the copper layer and the base on which the base layer is formed are heat-treated. The surface of the uppermost layer of the substrate is flattened and smoothed, an intermediate layer made of a nickel-tin alloy layer is further formed on the flattened and smooth uppermost layer, a magnetic layer is formed on the intermediate layer, and this magnetic layer A method for manufacturing a high recording density magnetic disk, comprising forming a protective layer thereon.