JPH01196729A - Surface treatment of underlying ni-cu-p plated substrate for magnetic disk - Google Patents

Abstract

PURPOSE:To prevent discoloration of the surface of a substrate subjected to a surface treatment at the time of rinsing and storing by subjecting the substrate to mirror polishing, then immersing the same into a specific soln. CONSTITUTION:The substrate formed by subjecting an Al alloy substrate to the surface treatment by electroless Ni-Cu-P plating is subjected to the mirror polishing and is then immersed into the aq. soln. of an org. compd. (e.g.: benzotriazole) which forms a reactive film insoluble in water by reacting with Ni-Cu or the like, by which an inhibitor film is formed on the surface. The discoloration of the substrate surface at the time of the rinsing after the mirror polishing or during the storage is then prevented and the corrosion resistance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a technology for manufacturing an underplating substrate for magnetic disks, and more specifically, the present invention relates to a technology for manufacturing an underplating substrate for magnetic disks, and more specifically, it relates to an electroless N-plated substrate on an aluminum alloy substrate.
The present invention relates to a surface treatment method that can improve the corrosion resistance, particularly the discoloration resistance, of a mirror-polished substrate that has been subjected to i-Cu-P plating treatment.

(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 and Off-sputtered films have been developed in place of conventional metal plating films and metal sputtering films, and this has brought with it several new problems in terms of manufacturing technology for magnetic disk substrates. It's starting to happen.

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

(Problems to be Solved by the Invention) By the way, when manufacturing a base plated substrate for a magnetic disk made of aluminum alloy, electroless Ni-
After forming the Cu-P plating film, mirror polishing is performed, and then a thin film medium is formed, but after mirror polishing, it is necessary to perform cleaning with a neutral detergent and final cleaning to remove slurry.

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, which may cause the thin film medium to There are problems such as uneven adhesion of the sputtered film during formation, 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
Provides a new and practical surface treatment method that can prevent discoloration of the substrate surface that occurs during water washing and storage after mirror polishing and improve corrosion resistance for Ni-Cu-P substrates coated with Cu-P plating. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the present inventors have proposed a method for surface treatment after mirror polishing a base treatment substrate in which electroless Ni-Cu-P plating is applied on an aluminum alloy base. As a result of repeated studies, we found that once the substrate is immersed in a specific solution after mirror polishing to form an inhibitor film, discoloration of the substrate surface can be prevented even if the substrate is stored in water. It has been discovered that the corrosion resistance can be improved and that it can be used satisfactorily in media on which a magnetic film is subsequently formed by sputtering without deteriorating performance.

That is, the magnetic disk base Ni-Cu according to the present invention
-The surface treatment method for P-plated substrates involves mirror-polishing the substrate, which is made by applying electroless Ni-Cu-P plating on an aluminum alloy substrate, and then reacts with Ni and Cu to form a water-insoluble material. This method is characterized by immersing the organic compound forming the reaction membrane in water or a solution in which the organic compound is dissolved in a water-soluble solvent.

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, the mirror polishing of the substrate can be performed using a commercially available abrasive such as Mediball N08 (Fujiko Abrasive Industries Co., Ltd., trade name) with a double-sided polishing machine, as in the past. There are no particular restrictions on the polishing conditions.

In the present invention, the mirror-polished substrate is immediately immersed in a solution containing a specific organic compound after mirror-polishing (usually followed by slurry removal cleaning and finishing water cleaning). That's what I do.

In this way, if the substrate is once immersed in an aqueous solution in which an organic compound is dissolved immediately after washing with water, it can be stored without discoloration until it is dried, even if it is returned to the water washing solution. Of course, it is possible to continue immersing the organic compound in the aqueous solution in which the organic compound is dissolved; A preferred embodiment is immersion in a solution containing an organic compound. In addition, various modes are possible, such as storing it by the above method each time it is necessary to store it after polishing.

The above organic compound is an organic compound that reacts with Ni-Cu to form a water-insoluble reaction film (inhibitor), such as benzotriazole, benzoic acid, mercaptobenzothiazole, tolyltriazole, penzimiazole, etc. be able to. These are used after being dissolved in water or an appropriate water-soluble solvent.

Note that the slurry removal cleaning using a neutral detergent, finishing water cleaning, drying, thin film medium forming process, etc. performed after polishing are not changed in any way even if the surface treatment method of the present invention is adopted.

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

After forming an electroless Ni--Cu--P plating film on a 5-inch size aluminum alloy substrate by Masuyo Oba using a conventional method, the five substrates were mirror-polished at the same time using a double-sided polishing machine.

These were used as samples, and after mirror polishing, the slurry was removed using a Berglin cloth and a neutral detergent. Immediately after the final cleaning with ion-exchanged water was completed, they were immersed in a 0.2% benzotriazole aqueous solution at 25°C for 1 minute, and then , IPA, until drying with Freon (approximately IR1' for the first sample)
Jl), immersed in ion exchange water and stored.

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

After removing the slurry with a neutral detergent, removing the slurry with ion-exchanged water, and finishing the final cleaning with ion-exchanged water, the sample was subjected to base plating and mirror polishing in the same manner as in Example 1. It was immersed in a 2% sodium benzoate aqueous solution at .degree. C. for 1 minute, and then immersed in ion-exchanged water and stored until it was dried with IPA and Freon.

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

For comparison, samples were plated and mirror-polished in the same manner as in Example 1, and after removing the slurry with a neutral detergent, they were immersed in ion-exchanged water 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 final sample Nα5, which was washed and dried immediately after mirror polishing, but Rinse with replacement water.

Items that have been immersed and stored in the same ion-exchanged water will become more discolored on the surface as time passes after drying.

On the other hand, the samples of the present invention that were temporarily immersed in an aqueous benzotriazole solution or an aqueous sodium benzoate solution showed no discoloration on the surface even after 1 hour had passed after being immersed in ion-exchanged water, resulting in a mirror-like surface. Immediately after polishing, the slurry was removed, washed with water, and dried to obtain the same surface.

[Left below] In addition, each of these samples was subjected to a conventional method to obtain C.

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.

In addition, it was confirmed that similar effects could be obtained when using an aqueous mercaptobenzothiazole solution, an aqueous solution of tolyltriazole, and an aqueous solution of penzimiazole.

(Effects of the Invention) As described in detail above, according to the present invention, a substrate in which an electroless Ni-Cu-P plating film is formed on an aluminum alloy base for a magnetic disk is polished to a predetermined position after mirror polishing. Because it is immersed in a solution of.

Thereafter, even if it is stored immersed in a water cleaning solution for a long time, the surface does not discolor, and extremely excellent corrosion resistance 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.

Patent applicant: Kobe Steel, Ltd. Representative Patent Attorney Takashi Nakamura

Claims (1)

[Claims] After mirror-polishing the aluminum alloy substrate, which has been subjected to a surface treatment using electroless Ni-Cu-P plating, an organic compound that reacts with Ni and Cu to form a water-insoluble reaction film is first coated with water or water. Ni-C base material for magnetic disks characterized by being immersed in a liquid dissolved in a soluble solvent
Surface treatment method for u-P plating base.