JPH07311938A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate defect on the surface of a substrate caused by contaminants or the residue of alkaline detergent or surfactant by employing electrolyzed water in place of pure water for cleaning the surface of the nonmagnetic substrate of a magnetic recording medium. CONSTITUTION:When an electrolyzed water, i.e., an oxidative water (anode 2 water) or a reductive water (cathode 3 water) produced through electrolysis of water is employes as a cleaning water for the nonmagnetic substrate of a magnetic recording medium, the cleaning power is enhanced significantly by the oxidative or reductive properties thereof. Consequently, even if an alkaline detergent or a surfactant is used only a small quantity or it is not used at all, contaminants including oily contaminants can be removed effectively from the surface of the substrate. This method provides sufficient cleanliness for the substrate of magnetic recording medium.

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 recording medium, and more particularly to a method for cleaning a non-magnetic substrate of a magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, fixed magnetic disk devices have been widely used as external storage devices for information processing devices such as computers. A magnetic recording medium used in such a fixed magnetic disk device generally includes a non-magnetic substrate, a non-magnetic metal underlayer, a thin-film magnetic layer made of a ferromagnetic alloy, a protective layer,
A lubricating layer is sequentially provided and configured.

As the non-magnetic substrate, a substrate formed of an aluminum alloy on which a Ni-P layer is formed by electroless plating is usually used. After the surface of this substrate is processed to be smooth, in order to obtain good magnetic properties, it is subjected to texture processing to form a texture having fine irregularities. On top of that, as a non-magnetic metal underlayer, for example, C
Although r is formed into a film by a sputtering method, it is important to sufficiently clean the surface of the substrate in order to form a uniform layer having a uniform film thickness. Therefore, conventionally, the substrate is subjected to precision cleaning, for example, cleaning with bubbling N ₂ in pure water to remove the polishing agent used for the surface processing before the sputter film formation, and then the hot pure water is made alkaline. After degreasing cleaning with a cleaning solution containing detergent, warm pure water shower cleaning, pure water shower cleaning, and ultrapure water shower cleaning,
Extremely high degree of cleaning has been performed such as steam drying using IPA.

For these cleanings, pure water which has been filtered and sterilized by ultraviolet rays, and ultrapure water from which ions in the pure water have been removed are used. However, although water has a high dissolving power for many substances and is excellent as a cleaning liquid, it has no dissolving power for oily substances having a low polarity and has no cleaning effect. For that purpose, as described above, washing is performed with a washing liquid having an ability to wash oily substances by adding an alkaline detergent and a suitable surfactant to warm pure water, and then washing with pure water or ultrapure water. Came.

[0005]

However, it is difficult to completely remove the alkaline detergent or the surfactant added to wash and remove the oily substance after that, and these residues affect the non-magnetic metal underlayer. However, there was a problem that the uniform and homogeneous film formation was hindered. If the amount of the alkaline detergent or the surfactant added is reduced, the residue can be eliminated, but on the other hand, a problem that oily contaminants remain and a good film formation is hindered occurs.

The present invention solves the above-mentioned problems and reduces the amount of alkaline detergent or surfactant added, or even if alkaline detergent or surfactant is not used, A method of cleaning a substrate capable of sufficiently removing contaminants including oily contaminants, and a method for producing a magnetic recording medium free from defects caused by contaminants on the substrate surface, residues of alkaline detergents and surfactants The purpose is to provide.

[0007]

According to the present invention, the above problems are solved by cleaning the surface of a non-magnetic substrate with a cleaning liquid, and further, at least a non-magnetic metal underlayer, a thin film magnetic layer made of a ferromagnetic alloy, and a protective layer. In a method of manufacturing a magnetic recording medium in which a layer and a lubricating layer are formed in this order, the problem can be solved by using electrolyzed water as cleaning water used for cleaning the non-magnetic substrate.

Among the electrolyzed water, cathode water having hydrogen (H ₂ ) and having a reducing property is particularly suitable as the washing water. This method is extremely effective regardless of whether the non-magnetic substrate is a substrate having a Ni-P layer formed by electroless plating on the surface of a substrate made of an aluminum alloy or a substrate made of glass.

[0009]

When water is subjected to DC electrolysis, oxygen is generated at the anode and hydrogen is generated at the cathode. Therefore, the water near the anode electrode contains oxygen and is oxidative, and the water near the cathode electrode contains hydrogen and is reducing. Oxidizing water (hereinafter referred to as "anode water") and reducing water (hereinafter referred to as "cathode water") obtained by electrolysis of such water, that is, electrolyzed water, is a non-magnetic substrate of a magnetic recording medium. When used as cleaning water for, the cleaning ability is greatly improved due to its oxidizing and reducing properties, and alkaline detergent,
It is possible to effectively remove contaminants on the surface of the substrate including oily contaminants even if the amount of surfactant used is reduced or even not used, and it is possible to clean the substrate sufficiently as a magnetic recording medium substrate. You get a degree.

[0010]

EXAMPLE FIG. 2 is an explanatory view of an example of an electrolytic cell used for electrolyzing water according to the present invention. In FIG. 2, an anode 2 and a cathode 3 made of Pt are inserted in an electrolytic cell 1, and a fluorine-based cation exchange membrane 4 is attached in close contact with the surfaces of both electrodes facing each other. The inside of the electrolytic cell 1 is divided into an anode chamber 1a, a cathode chamber 1b, and an intermediate chamber 1c by an anode electrode 2 and a cathode electrode 3.
When a required low voltage is applied between the both electrodes by the DC power source 5, the water in the electrolytic cell 1 is electrolyzed, and at the anode electrode

[0011]

## EQU1 ## The reaction of 2H ₂ O-4e ⁻ → 4H ⁺ + O ₂ occurs to generate O ₂ (oxygen), and at the cathode electrode,

[0012]

## EQU2 ## The reaction of 4H ⁺ + 4e ⁻ → 2H ₂ occurs to generate H ₂ (hydrogen). As a result, anode water containing oxygen and having oxidizing properties is obtained in the anode chamber 1a, cathode water containing hydrogen and having reducing properties is obtained in the cathode chamber 1b, and intermediate chamber water containing H is obtained in the intermediate chamber 1c. .

The surface of the substrate, which is formed by coating the surface of the disk-shaped aluminum alloy substrate with the Ni-P layer by electroless plating, is commercially available as a grinding liquid (mineral oil, surfactant, organic amine, chlorine-based extreme pressure agent, etc.). Is used), and then scribe cleaning is performed with a cleaning liquid obtained by adding a surfactant to pure water and air drying is performed to obtain a substrate sample. The cleaning residue adheres to the surface of the substrate sample as a contaminant.

On the surface of such a sample, anode water, intermediate chamber water, cathode water and ordinary pure water, which are electrolyzed water obtained in the electrolytic cell shown in FIG. The amount of C present on the surface of the sample after that was measured by a grim glow surface analyzer. The result is shown in FIG. In FIG. 1, the vertical axis represents the amount of C on the surface of the sample as 1 before washing, and shows the amount of C after washing with each washing water as a relative ratio. This amount of C is derived from contaminants remaining on the sample surface, and it is considered that the smaller the amount of C, the higher the cleanliness of the sample surface.

As shown in FIG. 1, it can be seen that the amount of C washed with electrolyzed water is smaller than that of washed with pure water, and the ability to wash electrolyzed water is higher. Among them, the cleaning ability of cathode water is particularly high. Since the electrolyzed water has a high cleaning ability as described above, by using the electrolyzed water for cleaning the substrate of the magnetic recording medium, the amount of the alkaline detergent and the surfactant added to the cleaning water can be reduced as compared with the conventional one. It is also possible to use no alkaline detergent or surfactant.

In the above examples, a substrate obtained by coating the surface of an aluminum alloy substrate with a Ni-P layer by electroless plating was used as the substrate sample, but the substrate sample is not limited to this, and a substrate sample made of glass is used. Against this, cleaning with electrolyzed water is similarly effective.

[0017]

According to the present invention, by using electrolytic water instead of pure water as the cleaning water used for cleaning the surface of the non-magnetic substrate of the magnetic recording medium, an alkaline detergent or a surfactant added to the cleaning water. Can be effectively and sufficiently removed including the oily contaminants even if the amount of is less than the conventional amount, and further, without using an alkaline detergent or a surfactant. It is possible to manufacture a magnetic recording medium without defects due to contaminants on the surface of the substrate, residues of alkaline detergents and surfactants.

[Brief description of drawings]

FIG. 1 is a diagram relatively showing the amount of residual C on the surface of a substrate sample after washing with various types of washing water, with the amount of C before washing being 1

FIG. 2 is an explanatory view of an example of a water electrolyzer according to the present invention.

[Explanation of symbols]

 1 Electrolyzer 1a Anode chamber 1b Cathode chamber 1c Intermediate chamber 2 Anode 3 Cathode 4 Cation exchange membrane 5 DC power supply

Claims (4)

[Claims] 1. A method of manufacturing a magnetic recording medium, wherein the surface of a non-magnetic substrate is cleaned with a cleaning liquid, and at least a non-magnetic metal underlayer, a thin film magnetic layer made of a ferromagnetic alloy, a protective layer, and a lubricating layer are formed in this order. 2. A method for manufacturing a magnetic recording medium, wherein electrolyzed water is used as cleaning water used for cleaning the surface of the non-magnetic substrate. 2. Hydrogen (H) in electrolyzed water is used as washing water.
_{2. The} method for producing a magnetic recording medium according to claim 1, wherein cathode water containing ₂ ) and having a reducing property is used. 3. The method of manufacturing a magnetic recording medium according to claim 1, wherein the non-magnetic substrate comprises a substrate made of an aluminum alloy, and a Ni-P layer formed on the surface of the substrate by electroless plating. 4. The method for manufacturing a magnetic recording medium according to claim 1, wherein the non-magnetic substrate is made of glass.