JPH07121868A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium having enhanced coercive force by roughening and washing the surface of a nonmagnetic substrate and forming a magnetic layer within a specified time after the washing. CONSTITUTION:The roughened surface of a nonmagnetic substrate is washed so as to remove abrasive grains, chips, etc., and a magnetic layer is formed on the substrate within 15min after the washing. The coercive force of the produced magnetic recording medium is enhanced and unevenness in the medium and that between media are reduced.

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.

[0002]

2. Description of the Related Art Conventionally, the following methods have been known as methods for manufacturing magnetic recording media. That is, the surface of the non-magnetic substrate is subjected to a surface treatment such as lapping, polishing or texturing to form a fine circumferentially processed fine groove, and the surface is roughened, and then a detergent or an ultrasonic wave is applied. Abrasive particles, polishing debris, etc. generated during roughening are removed using applied water, high-pressure water, etc., dried and washed, and then the substrate is stored for 30 minutes to 1 week. The stored non-magnetic substrate is washed with a detergent, high-pressure water, etc. to remove dust and the like adhering to the storage environment, dried and washed, and then a magnetic layer (this is a magnetic recording layer) is formed on the substrate. C is formed before the formation of the magnetic recording layer in order to adjust the magnetic characteristics of the magnetic recording layer, if necessary.
(including an underlayer made of r, Cr alloy, etc.), and carbon or SiO for protecting the magnetic layer on the magnetic layer.
After forming a protective layer consisting of ₂ etc., a lubricating layer is formed on the protective layer.

By the way, in recent years, with the increase in density of magnetic recording media, there has been a strong demand for improvement of the coercive force thereof.

However, the coercive force of the magnetic recording medium manufactured by the above method is, for example, Co--C in the magnetic recording layer.
In the case of r-Ta system, it is 1400 to 1530 Oe,
This is not sufficient to obtain the current recording density of 100 Mbit / inch ² or more.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a magnetic recording medium which solves the above problems and has improved coercive force.

[0006]

In order to achieve the above-mentioned object, the present invention provides a method for forming a magnetic layer on a non-magnetic substrate surface after roughening the surface, followed by washing, The magnetic layer is formed within 15 minutes after washing.

[0007]

In the method for producing a magnetic recording medium of the present invention, in the above method, the roughened surface of the non-magnetic substrate is washed (first washing) to remove abrasive particles, polishing debris, etc., and then the substrate is cleaned. It is important to form the magnetic layer on the substrate within 15 minutes without storing for 30 minutes to 1 week and without performing cleaning (secondary cleaning) for removing dust and the like. By forming the magnetic layer within 15 minutes after the primary cleaning as described above, the coercive force of the manufactured magnetic recording medium is improved and the variation in the medium and between the medium is also reduced. This is because the magnetic material layer is adsorbed on the substrate surface after being stored for 30 minutes to 1 week after the primary cleaning, and before the contaminants such as organic substances, which have been insufficiently and unevenly removed by the secondary cleaning, are adsorbed. It is believed that this is because It is presumed that the contaminants are oil components and organic solvents floating in the clean room atmosphere.

[0008]

【Example】

Example 1 After a Ni-P alloy hardening treatment film was formed on an Al alloy substrate having a diameter of 3.5 inches by an electroless plating method, the surface roughness R of this substrate was lapped and polished.
_max (the height from the highest peak to the deepest valley bottom within the reference length (0.08 mm)) was set to 30 nm or less.

Next, to this mirror-finished substrate, a polishing tape in which alumina abrasive grains having an average particle diameter of 6 μm are bound on a polyester base film is attached at 1.0 kgf / cm ^2.
The surface was roughened.

This roughened substrate was immediately rubbed with a sponge with a detergent, water to which ultrasonic waves of 1.8 MHz was applied was applied to the surface of the substrate, and high-pressure water (150 kgf / c) was applied.
m ² ). Then, the substrate was washed by being dried by a spin drying method.

Immediately after setting the cleaned substrate in the chamber of the sputtering apparatus, the pressure in the chamber was about 1
After evacuating to 0 ^-7 Torr, this substrate is 300 times
Heated to ° C. Then, 2 minutes after the cleaning,
r Gas pressure 10 mTorr, DC input power 15 W / cm ²
Under these conditions, a Cr underlayer having a thickness of 50 nm was formed by the DC sputtering method. Then, a bias voltage of 150 V is applied between the substrate and the sputtering target to apply Co.
A -Cr-Ta magnetic recording layer was formed to a thickness of 50 nm.

Then, a carbon protective layer having a thickness of 20 nm was formed by a DC sputtering method using an amorphous carbon target under the conditions of Ar gas pressure of 6 mTorr and DC input power of 20 W / cm ² , and then spin coating was performed on the protective film. Perfluoropolyether (Krytox,
A lubricating layer having a thickness of 2.5 nm was formed by DuPont.

The coercive force, reproduction output and number of errors per surface of the magnetic recording medium manufactured as described above were measured. The coercive force was measured while applying a magnetic field in the circumferential direction at a position where the radius of the magnetic recording medium was 30 mm. Note that this measurement was performed on three magnetic recording media. The reproduction output was measured by rotating the magnetic recording medium at 3600 rpm, setting the thin film magnetic head at a position with a radius of 30 mm on this medium, recording at a recording frequency of 7 MHz, and then measuring the output when read. Note that this measurement was performed on 20 magnetic recording media. Furthermore, one side (300
The number of errors per Mbit) was measured by rotating the magnetic recording medium and causing the magnetic head to sweep the radius of the medium between 20 and 44 mm. This measurement was also carried out on 20 magnetic recording media.

Examples 2 to 5 and Comparative Example After cleaning, the elapsed time until the formation of the Cr underlayer by the DC sputtering method is 4 minutes (Example 2), 6 minutes (Example 3), 10 minutes (Example) Example 4), 15 minutes (Example 5),
The test was conducted in the same manner as in Example 1 except that the reproduction output and the number of errors per surface were not measured for 30 minutes (comparative example).

Conventional Example The cleaned substrate was once stored in a clean room for 24 hours, then washed again and set in the chamber of a sputtering apparatus. After that, the same test as in Example 1 was performed.

Table 1 shows the results obtained as described above.

[0017]

[Table 1]

As is clear from Table 1, the magnetic recording media of Examples 1 to 5 have improved coercive force as compared with the conventional magnetic recording media. Further, in the reproduction output showing the same tendency as the coercive force, the average value in Example 1 is improved as compared with the conventional example, and the variation between the media is reduced. Furthermore,
The average number of error numbers of the medium in Example 1 is smaller than that in the conventional example. Therefore, it can be said that the variation of the coercive force in the medium is smaller in the first embodiment than in the conventional example.

[0019]

According to the method of the present invention, it is possible to manufacture a magnetic recording medium in which the coercive force is improved and the variation in the medium and between the medium is reduced.

Front Page Continuation (72) Inventor Yuto Kanaitsuka Ichikawa City, Chiba Chugoku 3-18-5 Sumitomo Metal Mining Co., Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. A method for forming a magnetic layer on a non-magnetic substrate surface after roughening and then cleaning the substrate, wherein the magnetic layer is formed within 15 minutes after the cleaning. And a method for manufacturing a magnetic recording medium.