JPS61214130A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of the titled medium by providing a plasma-polymerized protective film layer on the magnetic layer formed on a substrate. CONSTITUTION:A plasma-polymerized protective film layer 9 contg. sulfur is formed on a magnetic layer 8 to form cross linkages with the sulfur atom as a nucleus, hence the cross-linking density of the plasma-polymerized film layer 9 is increased and the corrosion resistance is sufficiently improved. The plasma-polymerized protective film layer 9 is formed by exposing the magnetic layer 8 to the plasma of the gaseous monomer of an org. compd. contg. sulfur or the gaseous mixture of the org. compd. monomer and another org. compd. monomer and performing plasma polymerization. Since the plasma-polymerized protective film layer 9 contains sulfur atoms capable of forming up to 6 linkages per atom, the cross-linking density of the plasma-polymerized film layer 9 is increased, water and air are hardly permeated and the magnetic recording medium with sufficiently improved durability can be obtained.

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
It is usually made by depositing a ferromagnetic metal thin film layer made of metals or their alloys on a substrate by vacuum evaporation, or by coating ferromagnetic metal powder with a binder resin on the substrate and drying. Although it has characteristics suitable for recording, on the other hand, 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 oxidation4.
What are the difficulties?

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 plasma-polymerized protective film layer of a silicon-based organic compound on a ferromagnetic metal thin film layer [Tetsuo Iijima,
Ken Hanabusa, Journal 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 Problem C] The present invention was made as a result of various studies in view of the current situation, and by forming a plasma polymerized protective film layer containing sulfur on the magnetic layer, sulfur atoms can be removed. The corrosion resistance of the plasma-polymerized protective film layer is sufficiently improved by forming cross-linked bonds with a high cross-linking density.

In this invention, the sulfur-containing plasma polymerized protective film layer formed on the magnetic layer is formed using a monomer gas of a sulfur-containing organic compound, or a monomer gas of a sulfur-containing organic compound and a monomer gas of another organic compound. It is formed by exposing the magnetic layer to plasma of a mixed gas with plasma and polymerizing the magnetic layer. This plasma-polymerized protective film layer contains sulfur atoms that can form up to six bonds per atom, which improves the crosslinking density of the plasma-polymerized protective film layer, making it difficult for water and air to pass through. , a magnetic recording medium with sufficiently improved corrosion resistance can be obtained.

The content of sulfur in the plasma-polymerized protective film layer thus formed is preferably within the range of 0.1 to 20% by weight based on all constituent atoms constituting the plasma-polymerized protective film layer. If it is too small, the desired effect will not be obtained, and if it is too large, sulfur alone will precipitate and corrosion resistance will not be improved.

As the monomer gas of the sulfur-containing organic compound used in such plasma polymerization, for example, thiophene, thianthrene, thianafucene, thioacetamide, etc. are preferably used, and in addition to these sulfur-containing organic compounds, A mixture of the monomer gas and the monomer gas of the organic compound in the pond is preferably used. Here, monomer gases of other organic compounds used in combination include, for example, monomer gases of hydrocarbon compounds such as propane, ethylene, propylene, C2F4
, monomer gas of fluorine-based organic compounds such as C3FG, and monomer gas of silicon-based organic compounds such as tetramethylsilane, octamethylcyclotetrasiloxane, hexamethyldisilazane, etc. are preferably used. When mixing with a monomer gas of an organic compound containing sulfur, the mixing ratio is O:1 to 1:3 in terms of volume ratio of monomer gas of these organic compounds to monomer gas of an organic compound containing sulfur. It is preferable that the amount of sulfur-containing organic compound gas is too small, and the desired effect cannot be obtained.

Monomer gas of these sulfur-containing organic compounds,
Alternatively, when a monomer gas such as a mixed gas of a monomer gas of an organic compound containing sulfur and a monomer gas of another organic compound is subjected to plasma polymerization by high frequency,
Radicals are generated by high frequency, and the generated radicals react and polymerize to form a film. In this way, when plasma polymerizing these monomer gases, coexistence of carrier gases such as argon gas and helium gas results in a polymerization rate of 3 to 5
Since the deposition rate is doubled, 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 (on the other hand, the monomer gas is plasma-polymerized with a relatively low degree of crosslinking, resulting in a hard protective film). A membrane layer cannot be 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/cJ, 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/ctA. 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, CO
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.

C 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 5xlO-5t-ole to form a 1000 μm thick polyester film on the polyester film. A ferromagnetic metal thin film layer made of a cobalt-nickel alloy 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. thiophene monomer gas from 4Q
The gas was introduced at a flow rate of sccm, the gas pressure was set to 0.03 Torr, and plasma polymerization was performed at a power density of 0.3 W/- for the electrode 5 to form a plasma polymerized protective film layer with a thickness of 300 mm. The sulfur content in this plasma polymerized protective film layer was 8% by weight. 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 tape A.

Example 3 In the formation of the plasma-polymerized protective film layer in Example 1, a film was prepared in the same manner as in Example 1 except that the same amount of thianthrene monomer gas was used in place of the thiophene monomer gas. A plasma-polymerized protective film layer having a content of 7% by weight was formed, and magnetic tape A was then used.

Example 4 In forming the plasma-polymerized protective film layer in Example 1, the flow rate of thiophene monomer gas was changed from 40 sec to 33 sec, and C2F4 monomer gas was introduced at a flow rate of 10 scn+ to raise the total pressure to 0.02.
)~L, and a plasma polymerized protective film layer having a thickness of 300 mm and a sulfur content of 4% by weight was formed in the same manner as in Example 1, except that the power density was 0.3 W/cd, and the magnetic I made tape A.

Example 5 α-p'6 magnetic powder 600 parts by weight Esresoku CN (manufactured by Tanemizu Kagaku Kogyo 80 ~ Co., Ltd., fluorinated vinyl-hinyl acetate copolymer) Bandex T-5250 (large 30μ manufactured by Nippon Ink Co., Ltd., urethane elastomer) Coronate Nippon Boliureta 10 Manufactured by Kogyo 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 the plasma polymerized protective film layer in Example 1, 40 scn+ of octamethylcyclotetrasiloxane monomer gas was used instead of thiophene monomer gas.
The thickness was measured in the same manner as in Example 1, except that nitrogen gas was introduced at a flow rate of 300 people formed a plasma polymerized protective film layer and made 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,
Tested for corrosion resistance. 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 5 had a lower deterioration rate than the magnetic tapes obtained in Comparative Examples 1 and 2, and from this, the present invention was applied. 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 thin 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 sulfur is provided on the magnetic layer.