JPS60237640A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent corrosion resistance and durability by forming a metal-contg. hydrocarbon base protective film having no hydrophilic property by plasma polymn. on a magnetic layer on a substrate in a gaseous monomer of a hydrocarbon organo metallic compd. CONSTITUTION:A carrier gas such as Ar or He is mixed at the same volume or above with the gaseous monomer of the hydrocarbon base org. compd. such as Sn(CH3)4 or Ge(CH3)4 in order to increase the rate of the plasma polymn. Such gaseous mixture is fed into a treating vessel 2 of a plasma treating device to form the metal contg. hydrocarbon base plasma-polymerized film 9 without contg. elements such as O and N having hydrophilicity on the magnetic film 8 formed on the substrate 1 of polyester, etc. which is set to face downward on the substrate 3 in the upper part in the vessel 2 and on which the thin ferromagnetic metallic film 8 is provided. The film 9 is thereby provided with high adhesive force to the layer 8 and good corrosion resistance even in high-humidity environment. The magnetic recording medium having excellent durability is obtd.

Description

[Detailed Description of the Invention] [Technical Field and Objectives] The present invention relates to a method for manufacturing a magnetic recording medium using a metal magnetic material as a recording element, and the objective of the invention is to produce a magnetic recording medium with excellent corrosion resistance. The purpose of this invention is to provide a method for manufacturing the same.

[Background 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 adhesion, or by applying ferromagnetic metal powder together with a binder resin onto the substrate and drying. Although it has characteristics suitable for high-density recording, it has the disadvantage that the magnetic layer, which uses a metallic magnetic material as a recording element, is easily oxidized by oxygen in the air, and as a result of gradual oxidation, the maximum magnetic flux density deteriorates.

For this reason, corrosion resistance has traditionally been improved by providing various protective film layers on magnetic layers that use metal magnetic materials as recording elements. is used with nitrogen gas as a carrier gas to perform plasma polymerization to provide a plasma-polymerized protective film layer of a silicon-based organic compound on a ferromagnetic metal thin film layer [Tetsuo Iijima, Hiroaki Hanabusa, Transactions of the Institute of Electrical Communication Engineers, J67- =C,, Nol ('84)) has been proposed.

However, this type of plasma-polymerized protective film layer made of silicon-based organic compounds contains many nitrogen and oxygen atoms that exhibit hydrophilic properties, and the crosslinking density of the protective film itself is low, so moisture in the air can be absorbed into this protective film layer. The problem is that the permeated moisture corrodes the magnetic layer, which uses a metal magnetic material as a recording element, and its corrosion resistance has not yet been sufficiently improved.

[Summary of the invention]

This invention was developed as a result of various studies in view of the current situation.
When plasma polymerization is performed using monomer gas of a hydrocarbon-based organometallic compound to form a plasma polymerized protective film layer made of a metal-containing hydrocarbon-based compound on a magnetic layer that uses a metal magnetic material as a recording element, this type of It was discovered that the plasma polymerized protective film layer does not contain nitrogen atoms or oxygen atoms, which exhibit hydrophilic properties, and has a high crosslinking density, so it does not allow moisture in the air to pass through, and its corrosion resistance is sufficiently improved. In this method, a magnetic layer containing a metal magnetic material as a recording element is exposed to a monomer gas of a hydrocarbon-based organometallic compound to perform plasma polymerization.
This method is characterized in that a plasma polymerized protective film layer made of a hydrocarbon compound containing metal is formed on the magnetic layer.

In this invention, when plasma polymerization is performed by exposing a magnetic layer containing a metal magnetic material as a recording element to a monomer gas of a hydrocarbon-based organometallic compound, plasma polymerization protection that does not contain nitrogen atoms or oxygen atoms exhibiting hydrophilic properties is achieved. A membrane layer is formed,
Furthermore, the metal contained in the plasma polymerized protective film layer acts as a catalyst to promote plasma polymerization, forming a plasma polymerized protective film layer with extremely high crosslinking density. The metal also provides good compatibility with the magnetic layer in which the metal magnetic material is used as a recording element, and also improves adhesion to the magnetic layer. As a result, it does not contain nitrogen atoms or @ elements that exhibit hydrophilic properties, and has a dense and high crosslinking density.
A plasma-polymerized protective film layer made of a hydrocarbon compound containing metal is firmly adhered to the magnetic layer whose recording element is a metal magnetic material, and moisture in the air does not permeate through the plasma-polymerized protective film layer. , a magnetic recording medium with sufficiently improved corrosion resistance can be obtained.

Monomer gases for hydrocarbon-based organometallic compounds used in such plasma polymerization include tetramethyltin,
Monomer gases such as tetramethylgermanium, diethylmercury, ferrotricarbonyl, pentaethoxytantalum, etc. are preferably used, and monomer gases of these hydrocarbon-based organometallic compounds can be used for plasma polymerization using radiofrequency waves. Radicals are generated, and the generated radicals react and polymerize to form a film. When plasma polymerizing these monomer gases, if a carrier gas such as argon gas or helium gas is present, the deposition rate will be 3 to 5 times faster than when plasma polymerizing monomer gases alone. It is preferable to carry out this process in the presence of a gas. When coexisting with these carrier gases, it is preferable that the composition ratio is within a range of 1:1 to 20:1 based on the volume ratio of the carrier gas to the 7-unit volume of the hydrocarbon-based organometallic compound. If the amount is too small, the precipitation rate will decrease, and if it is too large, the amount of monomer gas will decrease, which will interfere with the plasma polymerization reaction.

When carrying out such plasma polymerization, the force pressure and high-frequency power used are such that the higher the gas pressure, the faster the deposition rate of the plasma-polymerized protective film layer, but the monomer gas is plasma-polymerized with a relatively low molecular weight. A hard protective film layer cannot be obtained, and if the gas pressure is low and the high frequency power is high, the deposition rate will be slow, but on the other hand, a relatively hard polymerized protective film layer can be obtained. If the power is too high, the monomer gas will turn into powder and a plasma polymerized protective film layer will not be formed. Therefore, the gas pressure should be in the range of 0.03 to 5 Torr, and the high frequency power should be in the range of 0.03 to IW/-. More preferably, the gas pressure is within the range of 0.05 to 1 Torr, and the high frequency power is within the range of 0.05 to 0.5 W/cd. The plasma polymerized protective film layer made of a metal-containing hydrocarbon compound precipitated by performing plasma polymerization in this way is
It has a high degree of hardness, is dense, has a small coefficient of friction, and does not contain nitrogen or oxygen atoms that exhibit hydrophilic properties, so it extremely effectively prevents moisture from permeating and further improves corrosion resistance. The thickness of the plasma-polymerized protective film layer of a hydrocarbon compound containing such a metal 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 be lost. If the thickness is too thick and the spacing loss is too large, the electromagnetic conversion characteristics will be adversely affected.

The magnetic layer that uses a metal magnetic material as a recording element is made of Fe powder, Co
Metal magnetic powder such as Fe-Ni powder or Fe-Ni powder is coated on the substrate together with a binder component and an organic solvent and dried, or GO%Fe%Ni, Co-Ni alloy, Co
It is formed by depositing a ferromagnetic material such as -Cr alloy or Co-P%CoNiP on a substrate by means such as vacuum evaporation, ion blasting, sputtering, or 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 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. Tetramethyltin monomer gas was introduced from the gas introduction pipe 4 at a flow rate of 4 sec, the gas pressure was set to 0.03 Torr, and plasma polymerization was performed at a power density of 0.2 W/c+J of the electrode 5. A plasma polymerized protective film layer made of a hydrocarbon compound containing tin was formed. After that, it was cut to a predetermined width and a ferromagnetic metal thin film layer 8 and a plasma polymerized protective film layer 9 made of a hydrocarbon compound containing metal were sequentially laminated on the polyester film l as shown in FIG. I made magnetic tape A. In addition, 6 in the figure
7 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, the same procedure as in Example 1 was performed except that the same amount of tetramethylgermanium monomer gas was used instead of the tetramethyltin monomer gas. A plasma polymerized protective film layer made of a hydrocarbon compound containing 300% germanium was formed to produce magnetic tape A.

Example 4 In the formation of the plasma polymerized protective film layer in Example 1, the same procedure as in Example 1 was carried out except that the same amount of diethyl mercury monomer gas was used instead of the tetramethyltin monomer gas, and the thickness was 300 mm. A plasma-polymerized protective film layer made of a hydrocarbon compound containing human mercury was formed to produce magnetic tape A.

Example 5 In the formation of the plasma polymerized protective M91 layer in Example 1, the thickness was 300 people formed a plasma-polymerized protective film layer made of iron-containing hydrocarbon compounds and created magnetic tape 8.

Example 6 In forming the plasma-polymerized protective film layer in Example 1, the thickness was changed in the same manner as in Example 1, except that the same amount of pentaethoxytantalum monomer gas was used instead of the tetramethyltin-sulfur gas. A plasma polymerized protective film layer made of a hydrocarbon compound containing 300 tantalum was formed to produce magnetic tape A.

Example 7 α-Fe magnetic powder 600 parts by weight Esresoku CN (manufactured by Block Chemical Industry Co., Ltd. 80 μ, vinyl chloride-vinyl acetate copolymer) Pandesoku T-5250 (large 30 μ, manufactured by Nippon Ink Co., Ltd., urethane elastomer) Coronate L (Japan Polyurethane) 10〃 Trifunctional low molecular weight isocyanate compound manufactured by Ingyo Co., Ltd.) Methyl isobutyl ketone 400〃 Toluene 400〃 This composition was mixed and dispersed in a hole mill for 72 hours to prepare a magnetic paint. A magnetic layer was formed by coating on a polyester film to a dry thickness of 4 μm and drying. Next, on this magnetic layer, a plasma polymerized protective film layer having a thickness of 300 mm and made of a hydrocarbon compound containing tin was formed in the same manner as in Example 1, thereby producing magnetic tape A.

Comparative Example 1 In the formation of the plasma polymerized protective film layer in Example 1, 45 cc of octamethylcyclotetrasiloxane monomer gas was used instead of tetramethyltin monomer gas.
At the same time, nitrogen gas was introduced at a flow rate of I11.
A silicon-based organic compound having a thickness of 300 cm was prepared in the same manner as in Example 1, except that the total pressure was 0.05 Torr and the power density was 0.3 W/cot. A plasma polymerized protective film layer was formed and a magnetic tape was made.

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.

Table [Effects of the Invention] As is clear from the above table, the magnetic tapes obtained in Examples 1 to 7 all had lower deterioration rates than the magnetic tapes obtained in Comparative Examples 1 and 2. This shows that according to the manufacturing method of the present invention, a magnetic recording medium with even better corrosion resistance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus used in forming a plasma polymerized protective film layer made of a metal-containing hydrocarbon compound by the manufacturing method of the present invention, and FIG. FIG. 2 is a partially enlarged sectional view of a magnetic tape obtained by the manufacturing method of FIG. 1... Polyester film (substrate), 8... Ferromagnetic metal thin l! Layer iii, 9... Plasma polymerized protective film layer, A... Magnetic tape (magnetic recording medium) Patent applicant Hitachi Maxell Co., Ltd. Agent Takaoka-Haru j-1,,t! l! ;('-゛. 1)-j Niimi 3・

Claims (1)

[Claims] 1. A magnetic layer having a metal magnetic material as a recording element is formed on a substrate, and then this magnetic layer is exposed to a monomer gas of a hydrocarbon-based organometallic compound to perform plasma polymerization to form a hydrocarbon-based material containing a metal. A method for manufacturing a magnetic recording medium, comprising forming a plasma polymerized protective film layer made of a compound on a magnetic layer.