JPS63255821A - Method for preventing discoloration of substrate for magnetic disk - Google Patents

Abstract

PURPOSE:To permit importation of excellent resistance to discoloration to a substrate formed with an electroless Ni-Cu-P plating film by keeping the above-mentioned substrate immersed and stored in a prescribed aq. soln. during the time after polishing to a specular surface before drying. CONSTITUTION:The substrate subjected to an underlying treatment by the electroless Ni-Cu-P plating on an aluminum alloy substrate is kept immersed and stored in the aq. weak alkaline soln. during the time after the polishing to the specular surface before the drying via rinsing. The aq. weak alkaline soln. is exemplified by an aq. sodium carbonate soln., aq. sodium phosphate soln., etc. No discolorations are thereby admitted at all on the surface and exactly the same surface as the surface subjected to rinsing and drying right after polishing to a specular surface and slurry removal is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a manufacturing technology for a magnetic disk substrate, and more specifically, the present invention relates to a manufacturing technology for a magnetic disk substrate, and more specifically, the present invention relates to a manufacturing technology for a magnetic disk substrate. This invention relates to a method for preventing discoloration due to washing with water.

(Prior art) Generally, magnetic disk substrates are manufactured by forming a magnetic thin film medium on a metal disk substrate such as an aluminum alloy. In line with the demand, it has become increasingly strict to reduce the distance between the magnetic disk substrate and the magnetic head, and it has been requested to reduce the distance to about 0.1 .mu.m.

For this reason, the smoothness of the magnetic disk substrate has become an important characteristic, and specifically, it has become necessary to have as few defects as possible on the substrate surface and to have as high a surface precision as possible.

On the other hand, regarding thin film media, γ-Fe, O, and sputtered films have been developed in place of conventional metal plating films and metal sputtering films, and with this, new problems have arisen in terms of manufacturing technology for magnetic disk substrates. It's starting to happen.

For example, in the process of forming γ-Fe, O, and sputtered films, heat treatment at 300°C or higher is required, but conventional Ni-P plating films cannot maintain nonmagnetic properties during this heat treatment. cannot be used as a base plating base. Therefore, it is being considered to use a Ni--Cu--P plating film, which is nonmagnetic even when heat treated at 300'C or more, as a base.

(Problems to be solved by the invention) By the way, when manufacturing an aluminum alloy base,
After forming an electroless NiCu-P plating film on the substrate, mirror polishing is performed, and then a thin film medium is formed. After mirror polishing, cleaning with a neutral detergent and final cleaning are performed to remove the slurry. It is necessary to implement it. In this cleaning process, if the underlying Ni-Cu-P plating substrate is immersed in water even for a little while, the mirror-polished surface will discolor and oxides will be generated. There are problems such as uneven adhesion, poor accuracy and characteristic errors, and loss of value as a product.

In this regard, a method to prevent discoloration during water washing after mirror polishing is to wash with a neutral detergent to remove slurry after mirror polishing, and then quickly wash with water.
It is necessary to shorten the time immersed in water as much as possible, such as by immediately drying with Freon or the like.

However, in actual mirror polishing work, at least 5 to 40 disks are polished at the same time, depending on the disk size, and then they are cleaned. In practice, it is difficult to do this, so it is necessary to store it immersed in water for several minutes to several tens of minutes.

The present invention was made in view of the above situation, and
Electroless Ni- on aluminum alloy substrate for magnetic disks
The purpose of the present invention is to provide a new and practical storage method for a Ni-Cu-P base plated with Cu-P, which can prevent the surface of the base from discoloring during cleaning treatment after mirror polishing. It is.

(Means for Solving the Problems) In order to achieve the above object, the present inventor has proposed a method for storing a surface-treated substrate formed by electroless Ni-Cu-P plating on an aluminum alloy substrate in a mirror polisher. As a result of repeated studies, we have discovered that discoloration of the surface of the substrate can be prevented by storing the substrate immersed in a specific aqueous solution between mirror polishing, water washing, and drying.

That is, the method for preventing discoloration of a magnetic disk substrate according to the present invention includes electroless Ni-Cu-P on an aluminum alloy substrate.
For substrates that have been treated with plating,
After mirror polishing, washing with water, and drying, the product is immersed in a weak alkaline aqueous solution for storage.

The present invention will be explained in detail below based on examples.

The magnetic disk substrate targeted by the method of the present invention is produced by manufacturing an aluminum alloy substrate of an appropriate material in the same manner as in the past.
This is subjected to electroless Ni--Cu--P plating, and the manufacturing conditions, plating conditions, etc. are not particularly limited.

In addition, mirror polishing of the substrate can be performed using a double-sided polishing machine using a commercially available polishing agent such as Medipole N08 (Fujimi Abrasive Industry Co., Ltd., trade name), as in the past. There are no restrictions on polishing conditions, etc.

In the present invention, the mirror-polished substrate is washed with a neutral detergent to remove slurry, washed with water, and then stored in a weak alkaline aqueous solution before being dried. It is stored by soaking it in water. Therefore, when performing slurry removal cleaning after polishing, it is sufficient to store the product as described above, and then wash it with water and dry it, and if it is necessary to store it after polishing or slurry removal cleaning Various embodiments are possible, such as storing the data each time using the above method. Of course, if you only need to store some of the multiple substrates, you only need to store the relevant substrates using the above method, and it is not always necessary to store all the substrates. When storing,
After processing such as polishing, slurry removal cleaning or water cleaning,
It is desirable to store it immediately or promptly.

Examples of the weak alkaline aqueous solution include a sodium carbonate aqueous solution and a sodium phosphate aqueous solution, but are not particularly limited thereto.

In addition, slurry removal cleaning with a neutral detergent after polishing,
Water washing, drying, thin film media forming processes, etc. are not changed in any way by adopting the storage method of the present invention.

(Example) Next, examples of the present invention will be shown.

Example 1 After forming an electroless Ni-Cu-P plating film on a 5-inch aluminum alloy substrate by a conventional method,
Five sheets were mirror-polished at the same time using a double-sided polisher.

These were used as samples, and after mirror polishing, the slurry was removed using a Belklin cloth and a neutral detergent. time), immersed in a 1% aqueous sodium carbonate solution and stored.

Then, when all the samples had been washed with water, they were taken out of the aqueous sodium carbonate solution and dried as described above.

Samples were plated and mirror-polished in the same manner as in Example 1. After removing the slurry with a neutral detergent, the final cleaning with ion-exchanged water was completed, and then the samples were dried with IPA and CFC. for the entire time (approximately 1 hour for the first sample), 1
% sodium phosphate aqueous solution and stored.

Next, when all the samples had been washed with water, they were taken out of the aqueous sodium phosphate solution and dried as described above.

Comparative Example For comparison, samples were plated undercoat and mirror-polished in the same manner as in Example 1. After removing the slurry with a neutral detergent, the samples were immersed in ion-exchanged water and stored until drying with IPA and Freon. I kept it.

Next, when all the samples had been washed, they were taken out of the ion exchange water and dried as described above.

Regarding the samples obtained in each of the above Examples and Comparative Examples, the state of surface discoloration over time after washing with water was investigated. The results are shown in Table 1. In the same table, the cleaning order Nα indicates the order in which the samples were washed starting from the first sample Nα1.

As can be seen from Table 1, in the case of the comparative example that was immersed in ion-exchanged water and stored, no discoloration was observed in the last sample Nα5, which was washed with water and dried immediately after mirror polishing, but Items that have been washed with ion-exchanged water, immersed in the same ion-exchanged water, and stored will become more discolored on the surface as time passes after drying.

On the other hand, in the example of the present invention, which was kept immersed in a sodium carbonate aqueous solution or a sodium phosphate aqueous solution after washing with water until drying, no discoloration was observed on the surface even after 1 hour had passed. Immediately after mirror polishing and slurry removal, water washing and drying yielded the same surface.

In addition, each of these samples was treated with C using a conventional method.

A -Ni magnetic thin film medium was formed by a sputtering method and the medium characteristics were investigated, and it was confirmed that the inventive example had few errors and stable characteristics were obtained.

[Margin 1 (Effects of the Invention) As detailed above, according to the present invention, a substrate in which an electroless Ni-Cu-P plating film is formed on a magnetic disk substrate is mirror-polished and then dried. Since it is immersed and stored in a predetermined aqueous solution until then, extremely excellent color fastness can be imparted. Therefore, the subsequent formation of the magnetic thin film medium is good, and it is possible to prevent characteristic errors from occurring. Furthermore, since the method of the present invention is a simple and practical method, it can be carried out without any hindrance to other processing operations.

Claims (1)

[Claims] Substrates that have been subjected to surface treatment using electroless Ni-Cu-P plating on an aluminum alloy base are stored by immersing them in a weak alkaline aqueous solution after mirror polishing, washing with water, and until drying. A method for preventing discoloration of a magnetic disk substrate, characterized by: