JPS60237635A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To manufacture a magnetic recording medium provided with a protective film having good durability by subjecting a thin ferromagnetic metallic film to repeated glow polymn. treatments. CONSTITUTION:A gaseous monomer introduced through a nozzle 11 into a vacuum chamber 4 is adsorbed on a web 15 of a thin metallic film consisting of a ferromagnetic material and the monomer is repeatedly glow-polymerized by succeeding glow discharge treatments effected by discharge electrodes 8A-8C, by which the polymerized layer to serve as the protective film is laminated on the web. The discharge electric power by the electrodes 8A-8C is made smaller by such formation of the laminated layer than said electric power of the case in which the polymerized layer is formed by one time of glow polymn. The generation of the decomposition conflicting with the polymn. is prevented and the magnetic recording medium provided with the protective film having the good durability is formed.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method of manufacturing a magnetic recording medium suitable for short wavelength recording.

Conventional configurations and their problems In recent years, the density of magnetic recording has rapidly increased, and there is a strong desire to put into practical use magnetic recording media whose magnetic recording layer is a ferromagnetic metal thin film, which is theoretically suitable for short wavelength recording. Development is currently underway both domestically and internationally. Regardless of whether it is longitudinal recording or perpendicular recording, as long as recording and reproduction are performed according to the principle of electromagnetic induction, high-speed sliding contact with a magnetic head is inevitable.

On the other hand, the spacing loss during recording and reproduction of short wavelengths is large, and in any recording method, it is necessary to take sufficient consideration into the design.In particular, the thickness of the protective film should be changed from the conventionally used thickness range of 0.1 μm to 0.1 μm. Since a thickness of 0.3 μm is not practical at all, a method for forming a protective film that satisfies sufficient protective performance with a thickness of 0.05 μm, preferably 0.02 μm or less is desired.

FIG. 1 is an enlarged cross-sectional view of a typical magnetic recording medium.

In FIG. 1, 1 is a polymer substrate, 2 is a ferromagnetic metal thin film, and 3 is a protective film. For magnetic disks that must withstand high-speed sliding contact under particularly severe conditions, it is said that the protective film (3) should preferably have a thickness of 0.1 μm or more, even for silane-based plasma polymerized films, and this can be greatly improved. desired.

OBJECTS OF THE INVENTION The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing a magnetic recording medium with an improved method for forming a protective film.

Structure of the Invention The method for manufacturing a magnetic recording medium of the present invention is characterized by adsorbing a monomer gas onto a ferromagnetic metal thin film and then subjecting it to glow discharge treatment, which results in large losses during short wavelength recording and reproduction. A protective film can be formed in a thickness range where separation loss can be ignored.

Description of examples The present invention will be described below with reference to the drawings.

FIG. 2 shows a protective film forming apparatus used in carrying out the present invention.

In Figure 2, 4 is the vacuum chamber, 5 is the vacuum chamber B, 6 is the feed shaft, 7 is the winding shaft, 8 is the discharge electrode, 9 is the insulation introduction terminal, 10 is the discharge power source, and 11 is the monomer introduction terminal. Nozzle, 1
2 is a variable leak valve, and 13 is a free roller. Although the vacuum chambers A and B are evacuated separately, the exhaust system is omitted.

Reference numeral 14 denotes a slit in a passageway of a film-like processing body (hereinafter referred to as a web) 15.

Referring to FIG. 2, a brief explanation will be given of the procedure for processing the web 15 in which the ferromagnetic metal thin film 2 is disposed on the polymer substrate 1 in FIG. 1.

The web 16 is first subjected to a glow discharge treatment by eight people to clean and activate the ferromagnetic metal thin film surface. Next, it enters the vacuum chamber B5 and undergoes surface adsorption of monomer gas. next,
The monomer adsorbed on this surface is polymerized by glow discharge treatment of the electrode 8B. The quinomer is adsorbed again in the same manner and polymerized by discharge (electrode sC) treatment.

The number of repetitions of polymerization by such adsorption-current leakage treatment is determined by appropriate experiments depending on the required performance.

It is convenient for the discharge to be performed by applying an alternating current electric field ranging from a commercial frequency to a high frequency, and it is of course possible to use a known magnetron discharge or the like.

The manufacturing method of the present invention includes performing the glow discharge treatment in the presence of an inert gas and a monomer or in the presence of a monomer alone.

In any case, since thin polymer films are repeatedly laminated, the durability performance is improved compared to forming a film by one glow polymerization even if the film thickness is the same. Conventional methods require a large amount of discharge power to maintain a constant speed, and competition between polymerization and decomposition is considered to be favorable for improving durability, but decomposition cannot be ignored. In the present invention, since polymerization occurs on the surface where it was originally adsorbed, the film formation rate can be increased, so the discharge power can be reduced, and as a result, decomposition is further reduced, which is thought to produce better results.

Hereinafter, a more specific embodiment of the present invention will be described in detail.

Discharge electrode made of ViAl, width 5ecrn, length 50t-rn
Three of them were arranged as shown in Figure 2, and the own vessel with the web was 5 pots, and the slit at the entrance and exit to the chamber for adsorbing monomer was 0.2 crn x 55 m in thickness. . The vacuum chamber has an internal volume of approximately 0.85 folds, and vacuum chamber B has an internal volume of approximately 0.3 ηt, with an independent exhaust system, an oil diffusion pump system,
A mechanical booster pump and oil rotary pump system were used together.

The parameters considered were the degree of vacuum, the type of monomer, the passage time in vacuum chamber B (monomer adsorption), and the glow discharge conditions.

As a comparative example, a cylindrical can (diameter tso cm)
A discharge electrode with a radius of curvature of 3 ot-In (perimeter 1
A polymer film was formed on the same ferromagnetic metal thin film using a glow discharge polymerization apparatus in which the ferromagnetic metal thin film and the ferromagnetic metal thin film were formed using the same ferromagnetic metal thin film.

The ferromagnetic metal thin film used was made of Ni by high-frequency sputtering on polyethylene terephthalate with a thickness of 12 μm.
-Fe (Ni80 wt%) film 0.52 μm.

This is a stack of Go-Or (Or 20wt%) films of 0.18 μm.

The durability of the magnetic tape on which the protective film was formed was compared and evaluated from the viewpoint of output changes due to repeated reproduction using an amorphous alloy ring type head (gap length 0.19 μm).

The initial reproduction output was at a recording wavelength of 0.46 μm, and the value without the protective film was taken as the standard (odB).

(Hereinafter referred to as "Kinpaku") As described above, according to this example, a protective film having extremely good durability with a spacing loss of 1 dB or less can be obtained. Also, the values shown in the table are the average values at one arbitrary point on a tape length of 100 m, and are 10% of the values shown by the present invention.
In contrast, the comparative example had variations around the value of 50% or more and up to 90%.

This is due to the fact that the present invention is based on monomer adsorption; in conventional methods, it was necessary to strictly control not only the amount of monomer introduced but also the discharge conditions. Equilibrium is reached in a short time, so even if the discharge conditions change, it is good to keep the discharge power strong so that all the adsorbed monomers are polymerized, so good reproducibility and uniformity in the longitudinal direction can be obtained. It is.

This effect was sufficiently confirmed in other examples of the present invention as well.

Note that the present invention is not limited to magnetic recording media, and can be applied to other applications.

In another embodiment of the present invention, the adsorption polymerization may be repeated by forming separate chambers for each adsorbed monomer to form a multilayer film, or by adsorption of mixed monomers, which yields good results. I have confirmed that it produces results.

Effects of the Invention The present invention is characterized in that a monomer gas is adsorbed onto a ferromagnetic metal thin film and then a glow discharge treatment is performed.
A protective film with sufficient durability can be formed with a thickness of 0.00 Å or less, and a practical magnetic recording medium can be manufactured, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a magnetic recording medium that can be obtained by the method of the present invention, and FIG. 2 is a block diagram of the main parts of an apparatus used for carrying out the present invention. 4...Vacuum chamber person, 6...Vacuum chamber B, 8A
, 8B. 8C...discharge electrode, 11...monomer introduction nozzle. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 7

Claims (1)

[Claims] A method for manufacturing a magnetic recording medium, which comprises adsorbing a monomer gas onto a ferromagnetic metal thin film and then subjecting the film to glow discharge treatment.