JPS61104430A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease the coefft. of permeation of moisture and to improve corrosion resistance by forming a magnetic layer on a base body then exposing the magnetic layer to the plasma of the gaseous monomer of an org. compd. having a nitrile group and executing plasma polymn. thereby forming a plasma- polymerized protective film layer. CONSTITUTION:A polyester film is mounted to a vacuum deposition device and a cobalt-nickel alloy (8:2 by weight) is heated to evaporate in a vacuum to form a thin ferromagnetic metallic film layer consisting of the cobalt-nickel alloy on the polyester film. The film 1 on which the thin ferromagnetic material film layer is then set to the bottom surface of a substrate 3 disposed to the upper part in a plasma treating vessel and the gaseous monomer of acetonitrile is introduced into said vessel then the gaseous pressure is maintained under 0.03Torr and plasma polymn. is executed by an electrode to form the plasma- polymerized protective film layer by using the plasma treating device. The magnetic A laminated and formed successively with the thin ferromagnetic metallic film layer 8 and the plasma-polymerized protective film layer 9 on the polyester film 1 is thus manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly, to a method for manufacturing a magnetic recording medium with excellent corrosion resistance.

[Conventional technology]

Magnetic recording media that use metallic magnetic materials as recording elements are
Usually, a ferromagnetic metal thin film layer made of metals or their alloys is deposited on a substrate by vacuum evaporation, etc., but it is also made by coating ferromagnetic metal powder together with a binder resin on a substrate and drying it. Although it has characteristics suitable for recording, it has the disadvantage that the magnetic layer is easily oxidized by oxygen and moisture in the air, and the maximum magnetic flux density deteriorates as a result of gradual oxidation.

For this reason, efforts have been made to improve corrosion resistance by providing various protective film layers on the magnetic layer, and in recent years,
For example, a monomer gas of octamethylcyclotetrasiloxane is used together with nitrogen gas as a carrier gas, and plasma polymerization is performed to form a silicon-based organic compound plasma polymerized protective film layer on a ferromagnetic metal thin film layer [Tetsuo Iijima,
Hiroaki Hanafusa, Transactions of the Institute of Electrical Communication Engineers, J67-C, Nol.
('84)] has been proposed.

[Problem that the invention seeks to solve]

However, since this type of plasma-polymerized protective film layer made of silicon-based organic compounds contains many oxygen atoms, there are many gaps between atoms, and moisture in the air easily permeates through this protective film layer. The problem is that the magnetic layer is corroded by the moisture, and corrosion resistance has not yet been sufficiently improved.

[Means for solving problems]

This invention was made as a result of various studies in view of the current situation, and the magnetic layer is made of a monomer gas of an organic compound having a nitrile group, or a mixture of this type of monomer gas and a monomer gas of another organic compound. By exposing it to gas plasma and performing plasma polymerization to form a plasma polymerized protective film layer on the magnetic layer, the presence of nitrile groups facilitates the generation of radicals and increases the crosslinking density of the plasma polymerized protective film layer. to reduce the moisture permeability coefficient,
It has sufficiently improved corrosion resistance.

In this invention, the plasma polymerized protective film layer is formed on the magnetic layer by using a monomer gas of an organic compound having a nitrile group, or a monomer gas of an organic compound having a nitrile group and a mixture of another organic compound. It is formed by being deposited on the magnetic layer by exposing it to a plasma of a mixed gas with a monomer gas and performing plasma polymerization. This plasma-polymerized protective film layer contains nitrile groups in the monomer gas of the organic compound, so radicals are generated well during plasma polymerization, forming a plasma-polymerized protective film layer with high crosslinking density, and pores through which water molecules permeate. Since it becomes difficult to generate and the water permeability coefficient becomes small, the permeation of water molecules is effectively suppressed, and a magnetic recording medium with sufficiently improved corrosion resistance can be obtained.

Monomer gases for organic compounds having nitrile groups used in such plasma polymerization include acetonitrile,
Suitable examples include aliphatic nitriles such as propionitrile and butyronitrile, aliphatic dinitriles such as malonitrile, adiponitrile, and glutaronitrile, and aromatic nitriles such as benzonitrile and trinitrile. Mixed gases with monomer gases of other organic compounds are also preferably used, and when these monomer gases are subjected to plasma polymerization by high frequency, radicals are generated by the high frequency, and the generated radicals react and polymerize to form a film. becomes. Here, examples of other organic compound gases used in combination include monomer gases of hydrocarbon compounds such as propane, ethylene, and propylene, C2F 4 , C3F
A monomer gas of a fluorine-based organic compound such as G and a monomer gas of a silicon-based organic compound such as tetramethylsilane, octamethylcyclotetrasiloxane, hexamethyldisilazane, etc. are preferably used. The mixing ratio is
The volume ratio of the monomer gas of these organic compounds to the monomer gas of the organic compound having a nitrile group is 0:1 to 1.
It is preferable that the ratio be within the range of 1:3; if the monomer gas of the organic compound having a nitrile group is too small, the desired effect cannot be obtained. In this way, when plasma polymerizing these monomer gases, if a carrier gas such as argon gas or helium gas is present, the monomer gases will be deposited at a rate 3 to 5 times faster than when plasma polymerizing them alone. It is preferable to use these carrier gases together.

When coexisting with these carrier gases, the composition ratio is 1:1 in volume ratio of the carrier gas to the monomer gas.
It is preferable that the carrier gas coexist in the range of 20 to 1. If the carrier gas is too small, the deposition rate will be reduced, and if it is too large, the monomer gas will be too small, which will interfere with the plasma polymerization reaction.

When performing such plasma polymerization, the gas pressure and high frequency power are such that the higher the gas pressure, the faster the deposition rate of the plasma-polymerized protective film layer, but on the other hand, the plasma polymerization of the plasma polymerized gas with a relatively low degree of crosslinking results in a hard protective film. Layer is not obtained,
Furthermore, when the gas pressure is lowered and the high frequency power is increased, the deposition rate becomes slower, but a highly crosslinked and relatively hard protective film layer can be obtained. However, if the gas pressure is too low (and the high frequency power is too high), the monomer gas will turn into powder and a plasma polymerized protective film layer will not be formed.
003 to 5 Torr, and the high frequency power is 0.03
It is preferable that the range is ˜I W/aa, the gas pressure is o, oos ˜0.1 Torr, and the high frequency power is 0.05 Torr.
It is more preferable to set it within the range of ~0.5 W/cal.゛In the plasma-polymerized protective film layer that is deposited and formed by performing plasma polymerization in this way, the presence of nitrile groups facilitates the generation of radicals, resulting in a high crosslinking density, making it difficult to create pores through which water molecules can pass. As a result, moisture permeation is extremely effectively prevented, and corrosion resistance is further improved. The thickness of such a plasma polymerized protective film layer is 20-
The thickness is preferably within the range of 1,000 people. If the film thickness is too thin, the corrosion resistance effect of this protective film layer will not be fully exhibited, and if it is too thick, the spacing loss will be too large (too much, which will have a negative effect on the electromagnetic conversion characteristics). effect.

The magnetic layer that uses a metal magnetic material as a recording element is made of Fe powder, Co
A metal magnetic powder such as Fe-Ni powder or Fe-Ni powder is coated on a substrate together with a binder component and an organic solvent and dried, or CO5Fe, Ni, Go-Ni-
It is formed by depositing a ferromagnetic material such as P on a substrate by means such as vacuum evaporation, ion blating, sputtering, and plating.

In addition, as magnetic recording media, polyester film,
Various types of structures that come into sliding contact with magnetic heads, such as magnetic tapes based on synthetic resin films such as polyimide films, magnetic disks and magnetic drums based on disks and drums made of synthetic resin films, aluminum plates, glass plates, etc. includes.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 A polyester film with a thickness of 10 μm was loaded into a vacuum evaporation apparatus, and a cobalt-nickel alloy (weight ratio 8:2) was heated and evaporated under a vacuum of 5×10 −5 ) to form a thickness of 10 μm on the polyester film. A ferromagnetic metal thin film layer consisting of a cobalt-nickel alloy of 1000% was formed. Then the first
Using the plasma processing apparatus shown in the figure, a polyester film 1 on which a ferromagnetic metal thin film layer is formed is set on the lower surface of a substrate 3 disposed at the upper part of a processing tank 2, and a gas introduction pipe 4 is attached to the processing tank 2. A monomer gas of acetonitrile was introduced at a flow rate of 4 secm, the gas pressure was set to 0.03 Torr, and plasma polymerization was performed at a power density of 0.2 W/cni of the electrode 5 to form a plasma-polymerized protective film with a thickness of 30 mm. formed a layer. Thereafter, it is cut to a predetermined width and a ferromagnetic metal thin film layer 8 is placed on the polyester film 1 as shown in FIG.
A magnetic tape A was prepared in which a plasma polymerized protective film layer 9 was sequentially laminated. In the figure, 6 is an exhaust system for reducing the pressure inside the processing tank 2, and 7 is a high frequency power source for applying high frequency to the electrode 5.

Example 2 A ferromagnetic metal thin II made of cobalt was prepared in the same manner as in Example 1, except that cobalt was used instead of the cobalt-nickel alloy in forming the ferromagnetic metal thin film layer in Example 1.
! ! i! A layer was formed to produce magnetic tape A.

Example 3 In the formation of the plasma polymerized protective film layer in Example 1, the same process as in Example 1 was performed except that the same amount of malonitrile monomer gas was used instead of acetonitrile monomer gas. A plasma polymerized protective film layer was formed to produce magnetic tape A.

Example 4 The plasma polymerized protective film layer was formed in the same manner as in Example 1 except that the same amount of benzonitrile monomer gas was used instead of acetonitrile monomer gas in forming the plasma polymerized protective film layer in Example 1. A plasma polymerized protective film layer was formed to produce magnetic tape A.

Example 5 In forming the plasma polymerized protective film layer in Example 1, the flow rate of acetonitrile monomer gas was set at 4 sccm.
At the same time, the monomer gas of tetramethylsilane was introduced at a flow rate of 0.5 scm to make the total pressure 0.04)-L, and the power density was changed to 0.4 W/L.
The thickness was 300 mm in the same manner as in Example 1 except that it was set to aa.
A magnetic tape A was produced by forming a plasma-polymerized protective film layer.

Example 6 α-Fe magnetic powder 6003! i part S-LEC CN (manufactured by Block Chemical Industry Co., Ltd. 80 μ, vinyl chloride-vinyl acetate copolymer) Pandesox T-5250 (large 30 μ, manufactured by Nippon Ink Co., Ltd., urethane elastomer) Coronate L (manufactured by Nippon Polyurethane Co., Ltd.,
Trifunctional low molecular weight isocyanate compound) Methyl isobutyl ketone 400〃Toluene
400 This composition was mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint, and this magnetic paint was coated on a polyester film with a dry thickness of 4 μm.
A magnetic layer was formed by coating and drying so as to have a thickness of μ. Next, a layer with a thickness of 30 mm was applied on this magnetic layer in the same manner as in Example 1.
Magnetic tape A was produced by forming a plasma polymerized protective film layer.

Comparative Example 1 In the formation of a plasma polymerized protective film layer in the example process, octamethylcyclotetrasiloxane monomer gas was used for 4 sec instead of acetonitrile monomer gas.
Nitrogen gas was introduced at a flow rate of m sccm and nitrogen gas was introduced at a flow rate of l sccm.
A plasma-polymerized protective film layer with a thickness of 300 mm was formed in the same manner as in Example 1, except that the total pressure was 0.051 L and the power density was 0.3 W/-. and created magnetic tape.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1 except that the formation of the plasma polymerized protective film layer was omitted.

Regarding the magnetic tapes obtained in each example and comparative example,
The corrosion-resistant layer was tested. In the corrosion resistance test, the obtained magnetic tape was left under conditions of 60°C and 90% RH for 7 days and the maximum magnetic flux density was measured, and the maximum magnetic flux density of the magnetic tape before being left was 1.
00%, and the deterioration rate was investigated using the value compared with this value.

The table below shows the results.

〔Effect of the invention〕

As is clear from the table above, the magnetic tapes obtained in Examples 1 to 6 all had lower deterioration rates than the magnetic tapes obtained in Comparative Examples 1 and 2, and from this, the manufacturing method of the present invention It can be seen that a magnetic recording medium with even better corrosion resistance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus used when forming a plasma polymerized protective film layer by the manufacturing method of the present invention, and FIG. 2 is a magnetic tape obtained by the manufacturing method of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Polyester film (substrate), 8... Ferromagnetic metal thin film layer, 9... Plasma polymerization protective film layer, A...
・Magnetic tape (magnetic recording medium)

Claims (1)

[Claims] 1. Form a magnetic layer on the substrate, then apply this magnetic layer to
A method for manufacturing a magnetic recording medium, which comprises exposing the medium to a plasma of a monomer gas containing a monomer gas of an organic compound having a nitrile group to perform plasma polymerization to form a plasma polymerized protective film layer.