JPS6299915A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve running property and durability without spoiling the corrosion preventive effect of a thin ferromagnetic metallic film by a plasma- polymerized film layer by forming the thin plasma-polymerized film layer of an org. compd. on the thin ferromagnetic metallic film layer and forming a graft-polymerized layer to the thin plasma-polymerized film layer. CONSTITUTION:The thin ferromagnetic metallic film consisting of a prescribed metal or alloy is formed on a substrate 5 and the plasma-polymerized protective film layer 1 of the org. compd. is formed thereon; thereafter, the protective layer is exposed to a gaseous monomer of the vinyl deriv. expressed by the general formula CH2=CHX or the vinyli dene deriv. expressed by CH2=CXX', by which the graft-polymerized layer 4 consisting of the plasma-polymerized film layer as a backbone polymer is formed. The magnetic recording medium having excellent corrosion resistance, running property and durability is thus obtd.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a magnetic recording medium and a method for manufacturing the same, and particularly to a structure of a magnetic recording medium that reduces the coefficient of friction while maintaining high corrosion resistance, and a method for manufacturing the same. The present invention relates to a method of manufacturing a magnetic recording medium having the above structure.

<Prior Art> Among magnetic recording media, magnetic recording media that have a ferromagnetic metal thin film layer as a magnetic recording layer are usually made by depositing magnetic metals or their alloys on a substrate by vacuum deposition, sputtering, etc. It has characteristics suitable for high-density recording. On the other hand,
Direct contact of magnetic metal with the atmosphere causes corrosion, which causes deterioration of magnetism. Furthermore, since the coefficient of friction with the magnetic head is large, there is a problem that wear and sticking are likely to occur. For this reason, a technique has recently been proposed to provide a plasma-polymerized protective film layer of an organic compound (Japanese Unexamined Patent Publication No. 57-82
229, JP-A No. 58-102330), this plasma polymerized protective film layer can be formed thinly and uniformly on the ferromagnetic metal thin film layer, and has a highly crosslinked dense structure, so it is possible to
It is highly effective in preventing corrosion of lactic metals.

<Problems to be Solved by the Present Invention> However, with only the protective film layer obtained by the above method, the friction with the magnetic head is still large at 1.7, and the running performance and durability of the magnetic recording medium are significantly reduced. Couldn't improve it.

Means for Solving the Problems> The present invention was constructed to solve the above problems, and includes a magnetic film in which a protective layer for further reducing the coefficient of friction is formed on a plasma polymerized film formed on a base. It is a recording medium.

This will be explained in detail below.

In order to improve runnability and durability while taking advantage of the corrosion protection effect of the ferromagnetic metal thin film provided by the plasma polymerized film, the inventors created a coating on the plasma polymerized film that has a small coefficient of friction and therefore has a good lubrication effect. An attempt was made to form a second protective film layer having the following properties. As a result of this attempt, after forming a ferromagnetic metal thin film layer made of a predetermined metal or alloy on a substrate, and forming a plasma polymerized protective film layer of an organic compound on top of this, the general formula GHz was obtained without breaking the vacuum. The plasma-polymerized film layer is exposed to a monomer gas of a vinyl derivative 71 represented by CHX, or a gene represented by CH□=cxx', or a functional group such as a methyl group, a vinyl group, or a carboxyl group. A graft polymer layer with the backbone polymer is formed,
It has been found that a magnetic recording medium with excellent corrosion resistance, runnability, and durability can be obtained.

FIG. 1 shows the process of forming this kraft polymer layer.

In the figure, a large number of radicals 2 are present on the plasma polymerized film 1 immediately after the plasma polymerized film is formed [the same figure (
a)]. In this state, when the above-mentioned spring 3 comes into contact, the double bond or epoxy bond is easily cleaved and combines with the radical 2 on the plasma polymerized film 1 [Figure (b)].
, then the polymerization reaction proceeds in a chain manner [Figure (c)],
Eventually, the polymer ends bond together or hydrogen atoms are extracted from the monomer, the radicals disappear, and the polymerization reaction ends, finally forming the graft polymer layer 4 [FIG. 4(d)]. This graft-polymerized layer has a linear polymer structure with one end firmly bonded to the plasma-polymerized membrane layer, which is a backbone polymer.

For this reason, it is thought that a lubricating (gliding) effect occurs because it has a structure similar to that when a lubricant such as stearic acid is applied to a metal surface.

An example of a specific method for achieving the above configuration is shown below.

To form a plasma polymerized layer on a ferromagnetic metal thin film layer, a high frequency wave is applied while flowing an organic compound monomer gas in a processing tank, and the generated active species are deposited on the ferromagnetic metal thin film layer. This is done by growing.

The organic compounds used at this time are not limited to hydrocarbons such as propane, ethylene, and propylene, but also those containing oxygen, nitrogen, sulfur, etc., those containing fluorine such as tetrafluoroethylene, and tetramethylsilane and octamethylcyclo. Among those containing silicon such as tetrasiloxane and those containing metal elements such as tetramethyltin, organic compounds that have sufficient vapor pressure as a gas or liquid at room temperature are preferably used. . When actually forming a plasma polymerized protective film layer, one or more of these organic compounds are mixed and introduced into a vacuum chamber. In addition, for the purpose of accelerating the formation rate or introducing different elements,
In some cases, rare gases such as oxygen gas, nitrogen gas, fluorine gas, etc. are mixed with the above organic compounds and introduced into the vacuum chamber.

The graft polymer of the plasma-polymerized film layer formed as described above is grown by exposing the surface of the plasma-polymerized film layer to an atmosphere of monomer gas that allows graft polymerization without breaking the vacuum immediately after plasma polymerization. To do this. Examples of chemicals used in this case include ethylene, butadiene, vinyl chloride, acrylic acid, vinyl acetate, vinyl derivatives such as acrylonitrile, vinylidene chloride, methacrylic acid, vinylidene derivatives such as methyl methacrylate, and ethylene oxide, propylene oxide, etc. The following epoxy compounds are preferably used. The pressure of these 1,000-ton gas when exposing the plasma-polymerized layer is suitably 0.1 Torr or more; if it is less than this, the reaction will not occur quickly and it is not practical. Also, during the graft polymerization reaction, it is necessary to supply monomer gas to keep the monomer gas pressure constant.

Materials for forming the ferromagnetic metal thin film include C0% Fe, N
i, Co-Ni alloy, Go-Cr alloy, Co-P alloy,
A ferromagnetic material such as a Co-N1-P alloy is used, and a ferromagnetic metal thin film layer made of these ferromagnetic materials is deposited on a substrate by means such as vacuum evaporation, ion blasting, sputtering, or plating. Ru.

In addition, magnetic recording media include magnetic tapes based on synthetic resin films such as polyester films and polyimide films, magnetic disks and magnetic drums based on disks and drums made of synthetic resin films, aluminum plates, glass plates, etc. , including various forms of structures that come into sliding contact with the magnetic head.

Next, embodiments of this invention will be described.

<Example 1> First, a polyethylene terephthalate film with a thickness of 10AtI11 was loaded into a vacuum evaporation apparatus, and
' Cobalt is heated and evaporated under a pressure of Torr to form a polyethylene terephthalate film with a thickness of 1
A ferromagnetic metal R film layer made of 0,000 cobalt was formed. Next, the following processing was performed using the processing apparatus shown in FIG.

A polyethylene terephthalate film 5 with a ferromagnetic metal thin film layer formed thereon is unwound from a raw roll 7 placed in a film feed chamber 6, moved along a cylindrical can roll 8, passed through a graft polymerization chamber 9, and transferred to a take-up roll 10. I set it to wind up. Then film 5 is
While traveling in the direction of the arrow in the diagram at a speed of 13 using a high frequency of 13.56 MHz at 0.5W
Plasma polymerization is performed by applying a power density of / cal.
A plasma polymerized film layer was formed. At this time, the thickness of the plasma polymerized film was 120 people. Furthermore, at the same time, vinyl chloride 7-mer gas was introduced from the gas introduction pipe 14 attached to the graft polymerization chamber 9 at a flow rate of 1000 scem, and the gas pressure was increased to 100 scem.
As Torr, a graft polymerized layer of polyvinyl chloride was formed on the plasma polymerized layer. The time it takes for the film 5 to pass through the graft polymerization chamber 9 is 10 minutes, and one of the graft polymerization layers
Moatoshi had 130 people. Then cut it to the specified width and make a third
A magnetic tape as shown in the figure was manufactured. Reference numerals 15, 16, and 17 in FIG. It is a high frequency power source, and 19.20 is a vacuum seal part between the film feeding chamber 6 and the graft polymerization chamber 9. Also the third
In the figure, reference numeral 21 is a ferromagnetic metal fiiJ film layer, 1 is a plasma polymerization layer, and 22 is a graft polymerization layer.

<Example 2> When forming the graft polymerization layer in Example 1, ethylene oxide monomer gas was used instead of vinyl chloride monomer.
Introduced at a flow rate of 000 sec, and the gas pressure was set to 2Q Tor.
A magnetic tape was manufactured under the same conditions as in Example 1, except that r was used. The thickness of the graft polymer layer at this time was 90 layers.

<Example 3> A magnetic tape was manufactured under the same conditions as in Example 1, except that when forming the graft polymerization layer in Example 1, a butadiene gas was introduced instead of a vinyl chloride gas.

The thickness of the graft polymer layer at this time was 100 layers.

<Example 4> During the plasma polymerization layer formation in Example 1, propane monomer gas was introduced at a flow rate of 100 sec instead of tetramethylsilane monomer gas, and the gas pressure was set to 0.0.
7 Torr, and the power density of the applied high frequency is 0.7
A magnetic tape was manufactured under the same conditions as in Example 1 except that the magnetic tape was changed to W/-. The thickness of the plasma polymerized layer at this time was 140.

Comparative Example 1 A magnetic tape was manufactured under the same conditions as in Example 1 except that the polyvinyl chloride graft polymer layer was omitted.

Comparative Example 2 A magnetic tape was manufactured under the same conditions as in Example 4 except that the polyvinyl chloride graft polymer layer was omitted.

<Comparative Example 3> A magnetic tape was manufactured in the same manner as in Example 1 without attaching any protective film on the ferromagnetic metal thin film layer.

Corrosion resistance, runnability, and durability of the magnetic tapes obtained in each of the Examples and Comparative Examples above were investigated. The results are shown in the table below.

Corrosion resistance was evaluated by the deterioration rate of saturation magnetization when left in an atmosphere of 60" and 90% RH for one week. Running performance was evaluated by measuring the coefficient of friction with a stainless steel pin. Furthermore, durability was evaluated by a still test. The evaluation was made based on the time it took for the output to drop by 6 db.

As is clear from the above results, for the magnetic tapes obtained by the present invention (Examples 1 to 4), the deterioration rate of saturation magnetization was lower than that of the magnetic tapes of Comparative Example 1.2 in which only the plasma polymerized film was used as a protective film layer. It was at the same level as the magnetic tape of Comparative Example 3 without a protective film, and was smaller than that of the magnetic tape of Comparative Example 3 without a protective film, and both the friction coefficient and anti-still time showed significantly better values than Comparative Examples 1 to 3.

From the above points, by exposing the plasma-polymerized film to a monomer that can be graft-polymerized without breaking the vacuum after forming the plasma-polymerized film, a graft-polymerized layer is formed as a second protective layer on the plasma-polymerized layer, and the plasma-polymerized film layer becomes stronger. It was confirmed that it is possible to obtain a magnetic recording medium with significantly improved runnability and durability without impairing the anticorrosion effect of the magnetic metal thin film.

<Effects> As shown above, the present invention improves runnability, without impairing the anticorrosion effect of the ferromagnetic metal thin film by the plasma polymerized film layer.
A magnetic recording medium with significantly improved durability can be obtained.

[Brief explanation of drawings]

Figures 1 (a) to d) are schematic diagrams showing the process of forming a graft polymerization layer, and Figure 2 shows an example of the arrangement of processing equipment used when forming a plasma polymerization film layer and a graft polymerization layer. A schematic cross-sectional view of the device, and FIG. 3 is an enlarged partial view of the magnetic tape according to the present invention. 1... Plasma polymerization layer 4... Graft polymerization layer 21... Ferromagnetic metal thin film layer Fig. 1 Fig. 2 Fig. 3

Claims (2)

[Claims] (1) By forming a ferromagnetic metal thin film layer on a substrate, forming a plasma polymerized thin film layer of an organic compound on this ferromagnetic metal thin film layer, and further forming a graft polymerization layer on this plasma polymerized thin film layer, A magnetic recording medium characterized by having a layered structure. (2) After forming the plasma polymerized thin film layer of the organic compound, the graft polymerization layer is formed using a vinyl derivative represented by the general formula CH_2=CHX, or C
Vinylidene derivatives represented by H_2=CXX', or epoxy compounds represented by ▲There are mathematical formulas, chemical formulas, tables, etc. (However, XX' is hydrogen, halogen, or a functional group such as a methyl group, vinyl group, or carboxyl group. A method for producing a magnetic recording medium, characterized in that the method is carried out by exposing it to a monomer gas of