JPS61104425A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the crosslinking density of a plasma-polymerized protective film layer and to improve the corrosion resistance thereof by forming a magnetic layer on a base body and providing the plasma-polymerized protective film layer contg. chlorine on said magnetic layer. CONSTITUTION:A polyester film is mounted to a vacuum deposition device and a cobalt-nickel alloy (8:2wt.) 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 polyester film 1 formed with the thin ferromagnetic metallic film layer is set to the bottom surface of a substrate 3 disposed to the upper part in a plasma treating vessel 2 and a gaseous monomer of vinylidene chloride is introduced into the vessel 2 through a gas introducing pipe 4 attached to the vessel 2 then the gaseous pressure is maintained under 0.03Torr and the plasma polymn. is executed with an electrode 5 by using the plasma treating device, by which the plasma-polymerized protective film layer is formed. The film is thereafter cut to a prescribed width and the magnetic tape 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 [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with excellent corrosion resistance.

[Conventional technology]

Magnetic recording media that use metallic magnetic materials as recording elements are
Usually, it is made by depositing a ferromagnetic metal thin film layer made of metals or their alloys on a substrate by vacuum deposition, or by coating ferromagnetic metal powder with a binder resin on the substrate and drying. 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 plasma-polymerized protective film layer of a silicon-based organic compound is formed on a ferromagnetic metal thin film layer by using a 7-mer gas of octamethylcyclotetrasiloxane together with nitrogen gas as a carrier gas [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 consists of 1. forming a plasma polymerized protective layer containing chlorine on the magnetic layer; The steric hindrance of chlorine closes the gaps between atoms, effectively suppressing the permeation of moisture through the plasma polymerization protective film layer, and chlorine also promotes the hydrogen abstraction reaction, facilitating the generation of radicals, and promoting plasma polymerization. The crosslinking density of the protective film layer is increased to sufficiently improve corrosion resistance.

In this invention, the chlorine-containing plasma polymerized protective film layer formed on the magnetic layer is formed using a chlorine-containing monomer gas of an organic compound, or a chlorine-containing monomer gas of an organic compound monomer gas and another organic compound. In a monomer gas plasma, such as a mixed gas with chlorine gas or a mixed gas with a monomer gas of another organic compound,
It is formed by exposing the magnetic layer and subjecting it to plasma polymerization. This plasma-polymerized protective film layer has a large substituent called chlorine, so the steric hindrance of this substituent closes the gaps between atoms, making it difficult for water molecules to pass through, and the presence of chlorine prevents the hydrogen abstraction reaction. This facilitates the generation of radicals during plasma polymerization, improves the crosslinking density of the plasma polymerized protective film layer, and provides a magnetic recording medium with sufficiently improved corrosion resistance. In this way,
The content of chlorine in the plasma-polymerized protective film layer to be formed is preferably within the range of 0.1 to 10 mol% based on all constituent atoms constituting the plasma-polymerized protective film layer, and should not be too small. The desired effect cannot be obtained, and if the amount is too large, the crosslinking density will be too low and corrosion resistance will not be improved.

Examples of preferable gases for organic compounds containing chlorine used in such plasma polymerization include vinylidene chloride, ethylidene chloride, ethylene chloride, and vinyl chloride. A mixed gas of a monomer gas of an organic compound and a monomer gas of another organic compound, and a mixed gas of chlorine gas and a monomer gas of another organic compound are preferably used. Here, examples of other organic compound gases used in combination include monomer gases of hydrocarbon compounds such as propane, ethylene, and propylene, and C2F4.
, C3F6, and silicon-based organic compounds such as tetramethylsilane, octamethylcyclotetrasiloxane, hexamethyldisilazane, etc. are preferably used. When mixing with the monomer gas of an organic compound containing chlorine, the mixing ratio is in the range of θ to 1 to 1 to 3 in terms of volume ratio of 7 molar gas of these organic compounds to monomer gas of the organic compound containing chlorine. If the monomer gas of the organic compound containing chlorine is too small, the desired effect cannot be obtained, and when mixing with chlorine gas, the monomer gas of these organic compounds vs. It is preferable that the volume ratio be within the range of 10:1 to 3:1; too little chlorine gas will not produce the desired effect, and too much chlorine gas will interfere with the plasma polymerization reaction. , it becomes difficult to form a plasma polymerized protective film layer.

A mixed gas of these chlorine-containing organic compounds, a mixed gas of a chlorine-containing monomer gas and a monomer gas of another organic compound, or a mixed gas of chlorine gas and a monomer gas of an organic compound in a pond. When plasma polymerization is carried out using high frequency waves, radicals are generated by the high frequency waves, and the generated radicals react and polymerize to form a film. in this way,
When plasma polymerizing these monomer gases, if a carrier gas such as argon gas and 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 carry out this process in the presence of a carrier gas. When coexisting with these carrier gases, it is preferable that the composition ratio is within the range of 1:1 to 20:1 in terms of the volume ratio of the carrier gas to the monomer gas, and if the carrier gas is too small, the precipitation rate will be reduced. If the amount is too high, the amount of monomer gas will decrease and the plasma polymerization reaction will be hindered.

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,
Further, when the gas pressure is lowered and the high frequency power is increased, the deposition rate becomes slower, but on the other hand, a highly crosslinked and relatively hard protective film layer is obtained. However, if the gas pressure is lowered and the high frequency power is increased too high, the 7-mer gas will turn into powder and the plasma polymerized protective film layer will not be formed.
The high frequency power should be within the range of 3 to 5 torr, and the high frequency power should be within the range of 0.03 to I.
It is preferable to set the gas pressure within the range of W/+f, and the gas pressure to be within the range of o, o
os ~ 0.1 Torr, and the high frequency power is 0.05~0.
More preferably, it is within the range of 5 W/, ffl. The plasma-polymerized protective film layer that is deposited and formed by plasma polymerization in this way has a hydrogen abstraction reaction promoted by the presence of chlorine, good generation of radicals, and a high crosslinking density, and a large substitution of chlorine. Since it contains a group, the steric hindrance of this substituent closes the interatomic gaps, extremely well preventing moisture permeation, and further improving corrosion resistance. The thickness of such a plasma polymerized protective film layer is preferably within the range of 20 to 1000. 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, Spacing loss becomes too large, which adversely affects electromagnetic conversion characteristics.

The magnetic layer, which uses a metal magnetic material as a recording element, is made of Fe powder, Go
A metal magnetic powder such as powder or Fe-Ni powder is coated on a substrate together with a binder component and an organic solvent and dried, or a ferromagnetic material such as Co, Fe, Ni, Go-Ni-P, etc. It is formed by depositing it on a substrate by means such as vacuum evaporation, ion blasting, 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 cobalt-nickel alloy (weight ratio 8:2) was heated and evaporated under a vacuum of 5×10′5 Torr to form a 100 μm thick polyester film on the polyester film. A ferromagnetic metal thin film layer made of a cobalt-nickel alloy was formed. Next, using the plasma processing apparatus shown in FIG. 1, the polyester film 1 on which the ferromagnetic metal thin film layer was formed was set on the lower surface of the substrate 3 disposed at the upper part of the processing tank 2, and attached to the processing tank 2. Inject vinylidene chloride 7-mer gas from gas inlet pipe 4.
The gas was introduced at a flow rate of secm, the gas pressure was set to 0.03), and plasma polymerization was carried out at a power density of 0.2 W/ci for the electrode 5 to form a plasma polymerized protective film layer with a thickness of 300 mm. Thereafter, the tape was cut to a predetermined width, and a magnetic tape A was prepared by sequentially laminating a ferromagnetic metal thin film layer 8 and a plasma polymerized protective film layer 9 on a polyester film 1 as shown in FIG. 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 film layer made of cobalt was formed in the same manner as in Example 1, except that cobalt was used instead of the cobalt-nickel alloy in the formation of the ferromagnetic metal thin film layer in Example 1. I made Team A.

Example 3 In the formation of the plasma polymerized protective film layer in Example 1, the same procedure as in Example 1 was performed except that the same amount of vinyl chloride monomer gas was used instead of the vinylidene chloride monomer gas, and the thickness was 300 mm. A plasma polymerized protective film layer was formed to prepare magnetic tape A.

Example 4 In the formation of the plasma polymerized protective film layer in Example 1, the flow rate of vinylidene chloride 7-mer gas was set at 4 sec.
to 3 sec+w, and introduced c2F4 monomer gas at a flow rate of 1 sec to bring the total pressure to 0.0.
2) Magnetic tape A was produced by forming a plasma polymerized protective film layer having a thickness of 300 mm in the same manner as in Example 1, except that the magnetic tape was set to 0.3 W/cm and the power density was set to 0.3 W/cm.

Example 5 In the formation of the plasma polymerized protective film layer in Example 1, instead of the vinylidene chloride monomer gas, vinyl chloride monomer gas was introduced at a flow rate of 5 seconds, and chlorine gas was introduced at a flow rate of l seconds. to reduce the total pressure to 0.
．． Magnetic tape A was produced by forming a plasma polymerized protective film layer having a thickness of 300 mm in the same manner as in Example 1, except that the magnetic tape was 0.02 ) - and the power density was 0.3 W/-.

Example 6 α-Fe magnetic powder 600 parts by weight S-Lefukus CN (manufactured by Tanemizu Kagaku Kogyo 80, vinyl chloride-vinyl acetate copolymer) Vandefuchs T-5250 (large 30μ made by Nippon Ink Co., Ltd., urethane elastomer) Coronate Shikoku Nippon Polyurethane manufactured by 10〃Ingyo 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 30μ.
Magnetic tape A was produced by forming a plasma polymerized protective film layer.

Comparative Example 1 In the formation of the plasma polymerized protective film layer in Example 1, octamethylcyclotetrasiloxane monomer gas was used at 4 scc instead of vinylidene chloride monomer gas.
At the same time, nitrogen gas was introduced at a flow rate of l 5cca.
A plasma-polymerized protective film layer with a thickness of 300 mm was prepared in the same manner as in Example 1, except that it was introduced at a flow rate of +, the total pressure was set to 0.05 ) -L, and the power density was set to 0.3 W/lj. 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,
Corrosion resistance 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.
00%, and the deterioration rate was investigated using the value compared with this value.

The table below shows the results.

As is clear from the table above, the magnetic tapes obtained in Examples 1 to 6 all had a lower deterioration rate than the magnetic tapes obtained in Comparative Examples 1 and 2, and therefore, according to 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 sectional view showing an example of a plasma processing apparatus used in forming the plasma polymerized protective film layer of the present invention, and FIG. 2 is a partially enlarged sectional view of a magnetic tape obtained by the present invention. be. DESCRIPTION OF SYMBOLS 1... Polyester film (substrate), 8... Ferromagnetic metal i-film layer, 9... Plasma polymerization protective film layer, A...
・□ Magnetic tape (magnetic recording medium) Patent applicant Hitachi Maxell, Ltd. Figure 1

Claims (1)

[Claims] 1. A magnetic recording medium characterized in that a magnetic layer is formed on a substrate, and a plasma polymerized protective film layer containing chlorine is provided on the magnetic layer.