JPH1021537A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable production of a magnetic recording medium having few defects by controlling the contact angle of the substrate surface with pure water after surface treatment within a specified range. SOLUTION: The surface state of a substrate after surface treatment relates to data defects of a magnetic recording medium, and especially among properties of the surface state, the contact angle with pure water largely relates to defects. The contact angle is preferably <=85 deg.. Since the contact angle is influenced by the cleaning state of the surface, the cleaning degree is increased by using a detergent having high cleaning performance, by increasing the temp. of the cleaning liquid, by extending the cleaning time, by cleaning while scrubbing, etc., in order to control the contact angle to 85 deg.. If the contact angle is >85 deg., the substrate surface is easily dried before the film forming process after the surface treatment and contamination deposits and fixed on the dried part. This causes peeling after a film is formed. Therefore, by controlling the contact angle to <=85 deg., the substrate is prevented from drying during carrying, and moreover, a magnetic recording medium having little defects can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a magnetic recording medium, and more particularly to a method of manufacturing a magnetic recording medium having a surface processing step.

[0002]

2. Description of the Related Art A magnetic recording medium in which a magnetic layer is provided on a non-magnetic substrate is incorporated in a magnetic disk device and is widely used as an external storage means of a computer device. Such magnetic recording media are often subjected to a surface processing called texture processing for the purpose of controlling the anisotropy of the magnetic layer and preventing sticking (adsorption) of the recording / reproducing head.

The texture processing is a processing for forming minute irregularities on the surface of a substrate, and many methods and processing patterns have been conventionally studied. That is,
Examples of the processing method include a method using free abrasive grains and a method using a polishing tape coated with abrasive grains, and the processing patterns include concentric ones and intersecting ones. As a result of such studies, it has been found that the processing method, the processing pattern, and the size of the irregularities affect the final characteristics of the magnetic recording medium.

[0004]

However, the relationship between the surface state of the substrate and the characteristics of the magnetic recording medium in the process from the surface processing to the sputtering of a thin film such as a magnetic layer has been studied so far. However, it was determined by factors such as the layout of the production line and the production schedule.

[0005]

The present inventor has found that there is a relationship between the substrate surface condition after the surface processing and the data defect of the magnetic recording medium. The inventors have found that the magnitude of the contact angle is particularly related to the surface state, and arrived at the present invention.

That is, the gist of the present invention is a method for manufacturing a magnetic recording medium in which at least a magnetic layer is provided on a non-magnetic substrate, the method including a surface processing step before a film forming process, and a method after the surface processing. Wherein the pure water contact angle on the substrate surface is 85 ° or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the present invention, as the non-magnetic substrate, usually, a silicon substrate, an aluminum alloy plate or a glass substrate is used, but a metal substrate such as copper and titanium, a ceramic substrate,
A resin substrate or the like can also be used.

[0008] An underlayer is usually provided on the substrate. The underlayer is usually made of a nonmagnetic material, preferably a NiP alloy layer, and is usually formed by electroless plating or sputtering. The thickness is preferably 50 to 2
000 nm, particularly preferably 100-15,000
nm. The substrate in the present invention refers to a substrate provided with these underlayers.

The surface processing is performed before depositing the thin film. The processing method may be any method such as a method using free abrasive grains and a method using a polishing tape coated with abrasive grains. In addition, the magnitude relationship between the surface roughness before and after the treatment does not matter. That is, the polishing may be performed more smoothly than before the processing, or the surface may be roughened. Further, the processing pattern is also arbitrary such as concentric or crossing.

[0010] An intermediate layer such as a Cr layer or a Cu layer is preferably provided between the underlayer and the magnetic layer, and the thickness thereof is usually 20 to 200 nm, preferably 50 to 100 nm.
nm.

The magnetic layer is formed by a method such as electroless plating, electroplating, sputtering, or vapor deposition.
o-Ni-P, Co-Ni-Cr, Co-Ni-Pt,
Co-Cr-Ta, Co-Cr-Pt, Co-Cr-T
A ferromagnetic alloy thin film such as an a-Pt alloy is formed, and its thickness is usually about 30 to 70 nm.

A protective layer is provided on the magnetic layer as required. The protective layer may be formed by a method such as vapor deposition, sputtering, plasma CVD, ion plating, or a wet method. Carbide films such as TiC and SiC, nitride films such as SiN and TiN, SiO, AlO,
An oxide film such as ZrO is formed. Among these, a carbon film and a hydrogenated carbon film are particularly preferable. Further, a lubricant layer is usually provided on the protective layer.

In the manufacturing method according to the present invention, the contact angle of the substrate after the surface processing is 85 degrees or less. Since the contact angle of the substrate is greatly affected by the degree of surface cleaning, it is necessary to consider a substrate cleaning method after the surface processing in order to make the contact angle 85 degrees or less.

More specifically, the contact angle becomes smaller when the degree of cleaning is increased, such as by using a detergent having a high cleaning ability, raising the temperature of the cleaning liquid, extending the cleaning time, or cleaning with a scrub.

When the contact angle exceeds 85 degrees, the surface of the substrate is easily dried before the film forming step after the surface processing. Dirt collects and adheres to the dried part, making it difficult to remove. The portion where such dirt is fixed becomes a cause of peeling after film formation. Therefore, in the present invention, by setting the contact angle to 85 degrees or less, it is possible to prevent the substrate from drying during transport, and to realize a magnetic recording medium with few defects.

[0016]

EXAMPLE An aluminum alloy plate having a diameter of 3.5 inches was coated with N.
Twenty-four substrates were subjected to i-P plating, mirror-polished and washed. Next, using a texture machine manufactured by Hitachi Electronics Engineering Co., Ltd., alumina tape (trade name: WA8000SFOY) manufactured by MIPOX Co., Ltd. was pressed against both sides of the substrate with rubber rollers, and the average surface roughness was 5
The surface processing was performed so as to be about 0 °.

Next, the substrate was washed under the conditions shown in Table 1, and four samples having different contact angles were manufactured.

[0018]

[Table 1]

In these samples, the contact angle was measured using a FACE contact angle meter CA-S150, manufactured by Kyowa Interface Science Co., Ltd., by a suitable method using pure water.

Next, a Cr underlayer (1000) was formed on the substrates obtained in Examples and Comparative Examples by sputtering.
Å), a CoCrTa magnetic film (500 Å) and a carbon protective film (200 Å) were sequentially formed, and a lubricant was applied on the protective layer to manufacture a magnetic disk. The number of surface defects (the number of CMs) of the obtained magnetic disk was evaluated by the following method.

Guzik tester RWA501 type Rotation speed 5500 rpm Test head Thin film head (GW = 5 μm) Test pitch 5.0 μm Missing slice 70% Frequency 13.7 to 23.7 MHZ at zone bit
Table 2 shows the evaluation results for each example and comparative example.

[0022]

[Table 2]

[0023]

As described above, according to the method for manufacturing a magnetic recording medium of the present invention, a magnetic recording medium with few defects can be realized by controlling the contact angle of the substrate after texture processing to a specific range. It has the effect of.

Claims (1)

[Claims] 1. A method of manufacturing a magnetic recording medium comprising a non-magnetic substrate having at least a magnetic layer provided thereon, comprising a surface processing step before a film forming step, wherein pure water on a substrate surface after the surface processing step is provided. A method for manufacturing a magnetic recording medium, wherein a contact angle is 85 ° or less.