JPH0740360B2 - Method for manufacturing magnetic disk substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a magnetic disk substrate having a smooth surface and a flat surface.

(Prior Art) In recent years, as a magnetic disk capable of high density recording, a magnetic disk having a magnetic layer formed by plating, sputtering, vapor deposition or the like has been put into practical use.

This magnetic disk is formed by forming a non-magnetic underlayer such as nickel-phosphorus alloy on a non-magnetic metal substrate, usually an aluminum alloy substrate, and forming a magnetic layer on it by plating, sputtering, etc., and further protecting it if necessary. It is provided with layers.

However, since this type of magnetic disk substrate is required to have high smoothness and flatness, it is necessary to polish the aluminum substrate to have a highly smooth surface. However, since aluminum is soft, it is difficult to obtain a predetermined smoothness. There was a problem of difficulty and poor productivity.

In order to solve this problem, a method of applying a thin synthetic resin layer on an aluminum substrate to obtain surface smoothness and an attempt to manufacture the entire disk with a synthetic resin are known.

(Problems to be Solved by the Invention) However, even if the surface of the aluminum substrate is smoothed or flattened by various methods, if a nickel-phosphorus plating layer is formed on it, pinholes, etc. are formed on the surface of the plating layer in contact with the plating solution. Since the structural defect of 1) occurs, or the thickness of the plating layer becomes non-uniform and unevenness (waviness) occurs on the surface, the fact is that the nickel-phosphorus plating layer is polished again.

(Means for Solving the Problems) The present invention is a method for obtaining a magnetic disk substrate having a nickel-phosphorus plated layer having excellent surface smoothness and flatness without polishing, The feature is
A non-magnetic nickel-phosphorus plating layer is formed on the inner surface of a molding die having disk-shaped cavities and a smooth inner surface, and synthetic resin is supplied into the die, or a non-magnetic metal core plate is placed in the die. And a synthetic resin is supplied between the plating layer and the core plate, and the synthetic resin and the plating layer are integrated under heating to manufacture a magnetic disk substrate having a nickel-phosphorus plating layer on the surface. In point.

As a result, if the inner surface of the mold is made smooth, the surface of the plating layer that was in contact with the mold will come to the surface of the disk substrate, and it will be extremely smooth and flat without polishing the disk substrate individually. It is possible to obtain a plating layer with good quality.

The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a sectional view showing a first step (formation of a plating layer) of an example of the method of the present invention, and FIG. 2 is a sectional view showing the second step (supply of synthetic resin).

The molding die 1 includes, for example, a male die 11 and a female die 12, and a disc-shaped cavity is formed between the two. The upper and lower inner surfaces 111 and 121 of both molds 11 and 12 are flat and parallel to each other, and the center line average roughness Ra (JIS BO601) is
It has a mirror surface that is polished to 0.02 μm or less.

It is preferable to use stainless steel 304 or a metal plated with chrome for the upper and lower inner surfaces 111 and 121 of the mold 1 because the corrosion resistance to the plating solution is good and the nickel-phosphorus plating layer can be easily peeled off.

Masking 9 is applied to the peripheral surface of the mold 1 to form the upper and lower surfaces 11
The nickel-phosphorus alloy layer 2 is formed on the layers 1 and 121 by electroplating or electroless plating.

As the nickel-phosphorus alloy, one containing 6 to 20% by weight of phosphorus is preferable in order to make it non-magnetic.

The thickness of the plating layer 2 is usually about 30 to 50 μm.

As a method for forming the layer 2, an electroplating method having a high deposition rate is practical.

This is, for example, 300 g / l nickel sulphate and 1 phosphorous acid.
Add sulfuric acid to the plating solution consisting of 7.6 g / liter to adjust the pH.
Adjusted to 1.5-2.0, current density 2-10A / dm ² , bath temperature 60-7
It is possible to employ a usual method in which the molding die 1 is used as a cathode under the condition of 0 ° C. and electroplating is performed.

Alternatively, electroless plating can be used, but the deposition rate is slightly slower. In this case as well, it can be carried out by a known method in which the inner surface of the mold is subjected to a catalytic treatment and then a plating solution such as Blue Sumer is applied.

After the non-magnetic nickel-phosphorus plating layer 2 is formed on the inner surface of the mold 1 in this way, synthetic resin 3 is supplied and filled as shown in FIG. 2, and the plating layer 2 and the resin 3 are integrated under heating. Turn into. In this case, an adhesive may be applied in advance to the side of the plating layer 2 that contacts the resin 3.

It is desirable that the synthetic resin 3 has high heat resistance, the thermoplastic resin is polyphenylene sulfide, polyether ether ketone, polyether imide, polyether sulfone and the like, and the thermosetting resin is polyimide, bismaleimide-triazine. Resin, epoxy resin and the like are suitable. Further, these may be reinforced with glass fiber or the like.

As a resin filling method, for a thermoplastic resin, injection molding, compression molding in which a molten resin is injected into a mold and then the mold is clamped, or the like can be used. In the case of a thermosetting resin, transfer molding, compression molding in which a liquid resin is injected and heat-cured under pressure, a method of impregnating a fiber cloth with a resin and supplying it, and heat-curing the resin can be used.

The electroplating method has the advantages that the deposition rate is high and the obtained plating layer is dense and has high strength.
It is difficult to make the thickness uniform, and in the case of a disk, the plating thickness of the peripheral portion becomes large. However, according to the method of the present invention,
Even if the thickness of the plating layer 2 is not uniform, the thickness fluctuation is absorbed by pressing with the resin 3 in a fluid state, and the surface of the disk substrate becomes flat. The plating layer 2 imparts a head crushing property to the disk, and if the surface is smooth, there is no problem in performance even if the thickness is somewhat uneven.

Further, in the case of electroless plating, the thickness of the plating layer 2 becomes relatively uniform, but since hydrogen is generated, pinholes are easily generated on the surface in contact with the plating solution. However, according to the method of the present invention, such a problem does not occur because the surface not contacting the plating solution comes to the outer surface of the disk.

After the resin 3 is integrated with the plating layer 2, the disk substrate is taken out by cooling while maintaining pressure, and the plating layer 2 is peeled from the inner surface of the mold 1, and the surface is smooth and has the transferred mold surface. It becomes a flat surface, eliminating the need for polishing. If a magnetic layer is immediately formed on the plated layer 2 by a conventional method, a lightweight magnetic disk can be obtained.

FIG. 3 is a sectional view showing another embodiment of the present invention,
A non-magnetic metal core plate 4 such as an aluminum alloy is inserted into the mold 1 on which the plating layer 2 is formed, a resin 3 is supplied and filled between the core plate 4 and the plating layer 2, and the core plate is formed by the resin 3. 4 and the plating layer 2 are integrated. This is for example
The resin 3 impregnated fiber cloth, the core plate 4, and the resin 3 impregnated fiber cloth are sequentially stacked in the mold and heated and pressed.

In this case, the core plate 4 whose surface is not polished can be used as it is.

The thickness of the resin 3 ensures the adhesive force and the plating layer 2
100μ in order to absorb the thickness fluctuations and surface roughness of the core plate 4.
It is better to be m or more.

Since this disk substrate is composed of a metal core plate and a resin surface layer, it is lighter in weight than a metal only plate, and the metal core plate reduces sink marks at the time of molding, resulting in even better flatness.

In the above description, the plating layers are provided on both sides, but it goes without saying that this may be on one side.

(Effect of the Invention) According to the method of the present invention, a non-magnetic nickel-phosphorus plating layer is formed on a smooth inner surface of a molding die, and the non-magnetic nickel-phosphorus plating layer is integrated with the resin under heating in the die so as to be separated from the inner surface of the die. Because I chose
The plated surface located on the surface of the disk substrate is a very smooth surface obtained by transferring the surface of the mold, and there is no problem such as structural defects.

Further, it is desired to avoid that the thickness of the plating layer (particularly the electroplating layer) becomes non-uniform, but according to the method of the present invention, the unevenness of the surface of the plating layer which is not in contact with the mold is filled with the fluid resin,
A disk substrate having good flatness as a whole can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first step of an example of the method of the present invention, and FIG. 2 is a sectional view showing the same second step. FIG. 3 is a sectional view showing another example of the method of the present invention. DESCRIPTION OF SYMBOLS 1 ... Mold, 111, 121 ... Mold inner surface 2 ... Nonmagnetic nickel-phosphorus plating layer 3 ... Synthetic resin, 4 ... Nonmagnetic metal core plate

Claims (2)

[Claims] 1. A nonmagnetic nickel-phosphorus plating layer is formed on the inner surface of a molding die having disk-shaped cavities and a smooth inner surface, and a synthetic resin is supplied into the die to heat the resin and the plating layer. Is integrated into a disk substrate, and the molded disk substrate is then cooled and taken out. 2. A nonmagnetic nickel-phosphorus plating layer is formed on the inner surface of a molding die having disk-shaped cavities and a smooth inner surface, and a nonmagnetic metal core plate is inserted into the die and the plating layer and the core are inserted. A magnetic disk characterized in that a synthetic resin is supplied between the plate and the plating layer and the core plate are integrated by a synthetic resin under heating to form a disk substrate, and then the molded disk substrate is cooled and taken out. Substrate manufacturing method.