JPS63229620A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the travelling durability of a magnetic recording medium and the oxidation resistance of a thin ferromagnetic metallic film when the metallic film contg. oxygen is formed on a nonmagnetic supporting body to produce the medium, by treating the surface of the metallic film with alcohol contg. a specified amt. of water and by forming a protective film of an org. compd. on the metallic film. CONSTITUTION:The surface of a thin ferromagnetic metallic film formed on a nonmagnetic supporting body is treated with alcohol contg. 1-80wt.% water and a protective film of an org. compd. is formed on the metallic film. Inorg. foreign matter is removed from the surface of the metallic film chiefly by the physical detergency of the solvent, water soluble and oil soluble org. foreign matters are removed by the chemical detergency and the surface of the metallic film is activated by partial conversion into oxide or hydroxide. Since the protective film is formed on the clean activated surface of the metallic film, the protective film adheres firmly to the metallic film, improving the travelling durability of the resulting magnetic recording medium and the oxidation resistance of the metallic film.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of manufacturing a magnetic recording medium having a magnetic recording layer made of a ferromagnetic metal thin film.

(Prior Art) Conventionally, as a magnetic recording medium, Y-Fe is used on a non-magnetic support.
20. , 'I Fe20i *F83 containing Co
A coated type in which oxide magnetic powder such as 04 or alloy magnetic powder mainly composed of Fe, Co, Ni, etc. is dispersed in an organic binder such as vinyl chloride-vinyl acetate copolymer or polyurethane, coated, and dried. magnetic recording media are widely used.

In recent years, with the increasing demand for higher density, magnetic recording media in which the magnetic recording layer is made of a ferromagnetic metal thin film have been attracting attention.

The method for manufacturing such a ferromagnetic metal thin film type magnetic recording medium involves depositing gold f'1jtI made of a ferromagnetic metal material on a non-magnetic support.
A thin film is formed by a vacuum evaporation method, a sputtering method, an ion blating method, etc., a protective layer is formed on the ferromagnetic metal thin film by a solution coating method, a plasma polymerization method, a vacuum evaporation method, etc., and if necessary, It is common to further apply a back coat layer and process it into a predetermined shape. This ferromagnetic metal thin film type magnetic recording medium not only has various magnetic properties, but also because the magnetic layer thickness can be made extremely thin.

It has many advantages such as being able to record for a long time.

However, unlike a coated magnetic layer, the ferromagnetic metal thin film described above cannot have a lubricant impregnated into the magnetic layer, so the wear resistance of the ferromagnetic metal thin film is limited.

Surface treatment is important to improve running properties, running durability, etc., and to reduce changes over time such as oxidation.

For this reason, protective films made of various organic compounds have traditionally been provided on ferromagnetic metal thin film layers to improve wear resistance.

Efforts are being made to improve running properties or oxidation resistance. For example, protective films made of organic compounds can be formed by applying various lubricants or resins with good coating properties, or in recent years, by vacuum-depositing lubricants, etc., or by plasma polymerizing monomer gas of organic compounds. Attempts have been made to provide it on a ferromagnetic metal thin film layer.

(Problems to be Solved by the Invention) However, the protective film made of these organic compounds does not have good adhesion to the ferromagnetic metal thin film layer, and the protective film is removed in a relatively short time due to sliding contact with the magnetic head. Under harsh conditions of high temperature and humidity, the ferromagnetic metal thin film layer under the protective film may corrode in a relatively short period of time, or the protective film itself may peel off. performance has not been sufficiently improved.

The present invention has been made in view of the above-mentioned circumstances, and provides a method for manufacturing a magnetic recording medium with improved repeated running durability and oxidation resistance of a metal thin film.

(Means for Solving the Problems) In order to solve the above problems, the method for manufacturing a magnetic recording medium of the present invention includes applying 10 wt. % to 80 wt % of alcohol, and then a protective film made of an organic compound is formed on the ferromagnetic metal thin film.

(Function) According to experiments conducted by the present inventors, the surface of a ferromagnetic metal thin film is contaminated with fine dust, inorganic foreign matter such as missing magnetic powder, and various other organic foreign matter. This deteriorates the running durability and also has an adverse effect on the adhesion with the protective film. The surface of such a ferromagnetic metal thin film is
When water is treated with alcohol containing 10% it% to 80wt, inorganic foreign substances are removed mainly by the physical detergency of the solvent, and water-soluble and oil-soluble organic foreign substances are removed by the chemical detergency. Moreover, a part of the surface of the ferromagnetic metal thin film is converted into oxide or hydroxide and activated. In this way, on the surface of a clean and highly activated ferromagnetic metal thin film, a lubricant or the like can be vacuum-deposited, or an organic compound monomer gas can be plasma-polymerized, or a lubricant or a resin with good film properties can be applied. When a protective film made of an organic compound is formed by coating the ferromagnetic metal thin film, the protective film is firmly adhered to the ferromagnetic metal thin film, and the running durability and oxidation resistance are sufficiently improved.

(Example) An example of the method for producing a magnetic recording medium according to the present invention will be described below according to the process order.6 Materials for the nonmagnetic support on which the ferromagnetic metal thin film is deposited include polyethylene terephthalate, polybutylene, etc. Polyesters such as terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose diacetate and cellulose triacetate, polyetherketone, polyetheretherketone, polyvinyl chloride, and polyvinylidene chloride. , polyimide, polyamideimide, polycarbonate, etc. are used.

As the ferromagnetic metal thin film, Go formed by a vacuum evaporation method, an ion blating method, a sputtering method, etc.
Metal thin films mainly composed of Ni, Fe, etc., or metal thin films mainly composed of alloys thereof (e.g. Go-Nu, Co-
Cr, Co-Fe, Co-Ni-Cr, etc.).

Next, if necessary, a back coat layer is formed on the surface of the support opposite to the ferromagnetic metal thin film.

The main binder of the back coat is polyester,
Examples include polyurethane, vinyl, and acrylic fillers, and examples of fillers added include finely divided aluminum oxide, finely divided titanium oxide, silica, calcium carbonate, and carbon black.

Subsequently, the surface of the ferromagnetic metal thin film was coated with 10 wt of water.
% to 80 wt % of alcohol, a protective film made of an organic compound is formed on the surface of this ferromagnetic metal thin film.

Examples of alcohols used in the treatment include methanol, ethanol, n-propanol, isopropanol, and the like alone or in mixtures.

As a treatment method, it is sufficient to simply pass the ferromagnetic metal thin film through hydrous alcohol, or the surface of the ferromagnetic metal thin film may be treated with a large amount of hydrous alcohol and then the excess solvent remaining on the surface is scraped off with a metal roll. A slit reverse method in which the coating is removed or an air knife coating method in which the material is blown out with high-pressure air can also be applied.

As a protective film, all general protective films can be applied.
For example, it is a protective film made of a lubricant, a thermoplastic resin, a thermosetting resin, an electron beam curing resin, a plasma polymerized film, or the like.

As the lubricant, silicone oil, fluorine compounds, fatty acids, fatty acid esters, paraffin, surfactants, etc. can be used, and the fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. acid, oleic acid, linoleic acid, liluic acid, etc., and the fatty acid ester has 12 to 16 carbon atoms.
Fatty acid esters consisting of monobasic fatty acids and m alcohols having 3 to 12 carbon atoms are used. As the silicone oil, dialkylpolysiloxane, dialkoxypolysiloxane, monoalkylmonoalkoxypolysiloxane, monoalkylmonoalkoxypolysiloxane, phenylpolysiloxane, fluoroalkylpolysiloxane, etc. can be used. As the fluorine compound, perfluoroalkyl carboxylic acid, perfluoroalkyl phosphate, perfluoroalkyltrimethylammonium salt, perfluoroethylene oxide, perfluoroalkyl fatty acid ester, etc. can be used.

Examples of thermoplastic resins include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, and acrylic acid ester-acrylonitrile copolymer. polymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, methacrylic ester-acrylonitrile copolymer, methacrylic ester-vinylidene chloride copolymer,
Methacrylic acid ester-styrene copolymer.

and mixtures thereof are used.

As the thermosetting resin, phenol resin, epoxy resin, polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, etc. are used.

Acrylic ester is used as electron beam curing resin.

Methacrylic acid ester, vinyl acetate, etc. are used.

Any commonly used monomer gas may be used in plasma polymerization, such as CF4. C2F
4. C2F, ,C3F, ,C,H,F,C,)I2
Fluorine-containing compounds such as F, silicon compounds such as tetramethylsilane, hexamethyldisilazane, vinyltrimethylsilane, tetramethoxysilane, hexamethyldisiloxane, octamethylmicrotetrasiloxane, trimethylsilylacetylene, trimethylmethoxysilane, methane Hydrocarbon compounds such as , ethane, propane, ethylene, propylene, and acetonitrile are used.

In the present invention, when the surface of a ferromagnetic metal thin film is treated with hydrous alcohol, inorganic foreign matter such as fine dust attached to the surface and missing magnetic powder can be removed by physical cleaning power such as the pressure of the treatment solvent or by the treatment solvent. acts on the interface between the inorganic foreign matter and the ferromagnetic metal thin film.

The affinity of the inorganic foreign matter to the surface of the ferromagnetic metal thin film decreases and is removed. In addition, organic foreign matter contaminating the surface of the ferromagnetic metal thin film, including water-soluble foreign matter, is absorbed into the water in the processing solvent.
Oil-soluble foreign substances are removed by dissolving them in alcohol in the processing solvent.

Further, a part of the surface of the ferromagnetic metal thin film is changed into an oxide or hydroxide by the water in the treatment solution and is activated, thereby improving the adhesion with the protective film.

As described above, by keeping the surface of the ferromagnetic metal thin film clean and firmly adhering to the protective film, running durability, oxidation resistance, etc. are improved.

Hereinafter, embodiments of the present invention will be further described with reference to the drawings.

FIG. 1 is an enlarged sectional view showing the basic structure of a magnetic recording medium manufactured according to an embodiment of the present invention.

In FIG. 1, 1 is a back coat layer, 2 is a base film, 3 is a ferromagnetic metal thin film, and 4 is a protective film.

FIG. 2 is an enlarged view of the surface of a magnetic recording medium prepared by the method of the present invention, and as shown in FIG. 1, most of the inorganic foreign matter 6 such as minute dust and missing magnetic pieces on the surface of the ferromagnetic metal thin film 5 has been removed. Also, most of the organic foreign matter 7 is also removed. Furthermore, a part of the surface of the ferromagnetic metal thin film 5 changes into oxide or hydroxide, and the adhesion with the protective film 8 is improved. These effects improve running durability such as dropout or clogging, and oxidation resistance.

On the other hand, in the magnetic recording medium prepared by the conventional method, as shown in FIG. Since the surface activity is also low, the adhesion of the protective film 8 is poor, causing problems in running durability and oxidation resistance.

Comparative Example 1 Go was electron beam evaporated on a polyethylene terephthalate film with a thickness of 10 units along a cylindrical can with a diameter of 1 m in oxygen at 4 x 10-4 torr at a minimum incident angle of 43 degrees, and the film thickness was approximately 1500 mm. Comparative Example 2 The treated web prepared in Comparative Example 1 was prepared using myristic acid 11.
The ferromagnetic metal thin film was immersed in a 000pp benzene solution and dried to form a protective film made of myristic acid on the surface of the ferromagnetic metal thin film.

Example 1 After preparing the following treatment solutions 1 to 6 and treating the surface of the ferromagnetic metal thin film of the treated web prepared in Comparative Example 1,
These were immersed in a 11,000 ppp solution of myristic acid in benzene and dried to form a protective film made of myristic acid. As a treatment method, an air doctor method was applied, and during the treatment, a large amount of treatment liquid remaining on the surface of the ferromagnetic metal thin film was blown away with air, followed by drying at 100°C.

Treatment liquid ■ Methanol ■ Methanol + water (contains 5 wt% water) ■ Methanol + water (contains 10% water + 1%) ■ Methanol + water (contains 50 wt% water) ■ Methanol + water (80 w water
methanol + water (containing 90 wt% water) Example 2 After preparing the following treatment solutions 7 to 9 and treating the surface of the ferromagnetic metal thin film of the treated web prepared in Comparative Example 1,
These were immersed in a 11,000 ppp solution of myristic acid in benzene and dried to form a protective film made of myristic acid. Note that the processing method is the same as in Example 1.

Treatment liquid ■ Ethanol + water (50 wt% water) ■ n-propanol + water (50 wt% water) ■ Isopropanol + water (50 wt% water) 15 am width prepared in Comparative Examples 1 and 2 and Examples 1 and 2 , 5 rolls of 10my tape were arbitrarily extracted from each 500m long web by slitting it into a width of 8mm, and running durability (clogging, dropout) was measured using an 8mm video tape recorder.

The running durability was evaluated based on the clogging time during repeated 50-pass running. Dropouts were evaluated based on the average number of drops of −16 dB or more per minute for 15 μsec at the beginning of the run. In addition, regarding the oxidation resistance of the ferromagnetic metal thin film, each tape was heated at 60°C.
Evaluation was made based on changes in the tape surface (discoloration, rust, etc.) when the tape was left for 2 weeks under 90% RIIQ conditions. The results of these evaluations are summarized in the table below.

(Effects of the Invention) As explained above, according to the manufacturing method of the present invention, excellent effects such as improved running durability and oxidation resistance of the ferromagnetic thin film and uniform performance can be obtained. be.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a magnetic recording medium that can be obtained by the method of manufacturing a magnetic recording medium according to an embodiment of the present invention, FIG. 2 is an enlarged surface view of the same magnetic recording medium, and FIG. 3 is a conventional FIG. 2 is a surface view showing a magnetic recording medium. 1... Back coat layer, 2... Base film, 3... Ferromagnetic metal thin film, 4... Protective film,
5...Ferromagnetic metal thin film. 6...Inorganic foreign matter, 7...Organic foreign matter, 8...
Protective film. Figure 1 1・Back coat layer 2'・Base J12 Rem 3・Kaede bottle housing metal thin film 4・I Ami (protection)

Claims (1)

[Claims] A ferromagnetic metal film containing oxygen is formed on a non-magnetic support, and water is added from 10 wt% to 8 wt% to the surface of this ferromagnetic metal thin film.
A method for manufacturing a magnetic recording medium, which comprises treating the medium with alcohol containing 0 wt%, and further providing a protective film made of an organic compound thereon.