JPS59172140A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having a magnetic layer which is excellent in the dispersibility and dispersion stability of magnetic powder, has good surface smoothness and has an excellent electrical characteristics by incorporating high molecular weight perfluoroalkyl phosphate surface active agent in the magnetic layer. CONSTITUTION:Magnetic powder and high mol.wt. perfluoroalkyl phosphate surface active agent are incorporated in a magnetic layer. The high mol.wt. perfluoroalkyl phosphate surface active agent is expressed by the formula and is used preferably in a range of 0.1-10wt% to the magnetic powder. The high mol.wt. perfluoroalkyl phosphate surface active agent is soluble in water and when said agent contacts with the magnetic powder dispersed in an aq. soln., the agent sticks satisfactorily on the particle surfaces and forms a film, by which the dispersibility and dispersion stability of the magnetic powder are improved and the surface smoothness and electrical characteristics of the magnetic layer are improved.

Description

Detailed Description of the Invention The present invention relates to a magnetic recording medium, and its object is to have a magnetic layer having excellent dispersibility and dispersion stability of magnetic powder, good surface smoothness, and excellent electrical properties. The purpose of this invention is to provide a magnetic recording medium.

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating.
The magnetic layer is required to have good surface smoothness, excellent electrical properties, and excellent durability.

Therefore, the magnetic powder used has excellent dispersibility, and the surface smoothness of the magnetic layer is good, making it possible to provide magnetic recording media with high sensitivity and high S.
It is desirable to have something that can provide excellent electrical properties such as N ratio and improve durability, but because ordinary magnetic powder has a hydrophilic surface, it is difficult to disperse it well in a hydrophobic binder component. However, the dispersibility of the magnetic powder is not sufficiently good and tends to aggregate easily.

Therefore, in order to improve the dispersibility of magnetic powder, attempts have been made to improve the dispersibility of magnetic powder by, for example, treating the magnetic powder with a dispersant such as a dialkyl sulfosuccinate. In addition, this type of dispersant has a high foaming property and generates a large amount of bubbles when dispersing magnetic powder, making it difficult to work with.

The inventors conducted various studies in view of the current situation, and found that the dispersibility and dispersion stability of magnetic powder were sufficiently improved by including a perfluoroalkyl phosphate ester-based high molecular weight surfactant in the magnetic layer. It was discovered that the surface smoothness of the magnetic layer was further improved and the electrical characteristics were further improved, leading to the present invention.

The perfluoroalkyl phosphate high molecular weight surfactant used in this invention is 1 CF3 (CF2 CF2). -〇-P-OHH neutralized with jetanolamine, molecular weight 500
100,000 is preferably used, and specific examples include Surflon S-112 manufactured by Asahi Glass Co., Ltd.

This type of perfluoroalkyl phosphate ester-based high molecular weight surfactant is water-soluble and when it comes into contact with magnetic powder dispersed in an aqueous solution, it adheres well to the particle surface and forms a film.
The dispersibility and dispersion stability of the magnetic powder are sufficiently improved, the surface smoothness of the magnetic layer is improved, and the electrical characteristics are further improved.

In order to incorporate such perfluoroalkyl phosphate ester-based high molecular weight surfactants into the magnetic layer, they are dissolved in water, and dried magnetic powder is added to this aqueous solution to perform surface treatment of the magnetic powder. Alternatively, an aqueous dispersion of treated magnetic powder produced by mixing an aqueous solution of iron or other metal salts with an aqueous alkali solution is used as it is, and perfluoroalkyl phosphoric acid is added to the aqueous dispersion. The magnetic powder is surface-treated by adding an ester-based high-molecular-weight surfactant, and after drying, the magnetic powder is used to prepare a magnetic paint.

The amount used is preferably within the range of 0.1 to 10% by weight based on the magnetic powder; if it is too small, the desired effect will not be obtained, and if it is too large, the surface smoothness of the magnetic layer will deteriorate.

Examples of the magnetic powder used in this invention include r-
Fe203 powder, Fe3O4 powder, Co-containing r-Fe2
03 powder, co-containing Fe3O4 powder, Fe powder, C
Various conventionally known magnetic powders such as metal powders such as o powder and Fe-Ni powder are widely included.

In addition, as the binder resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, cellulose resin,
Any conventionally widely used binder resin such as polyurethane resin or isocyanate compound can be used.

Examples of organic solvents include ketone solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and sulfoxide solvents such as dimethyl sulfoxide. , ether solvents such as tetrahydrofuran, dioxane, etc.
Solvents suitable for melting the binder resin to be used are not particularly limited and may be used alone or in combination of two or more.

In addition, various additives commonly used in magnetic paints,
For example, dispersants, lubricants, abrasives, antistatic agents, etc. may be added as appropriate.

Next, embodiments of the invention will be described.

Example 1 Acicular r-Fe203 powder 1800g Cobalt sulfate (CoSO4・7H20) 600g Ferrous sulfate (Fe 304 ・7H20) 1800
g Caustic soda 2128 g 18 ff of a dispersion containing the above components was reacted at 45° C. for 8 hours, then washed with water and filtered. Next, 30 A of an aqueous solution in which 100 g of Surflon S-112 (perfluoroalkyl phosphate ester manufactured by Asahi Glass Co., Ltd.) was dissolved was added to the obtained slurry, and after dispersion treatment for 8 hours, it was dried to obtain cobalt-containing γ-F e A 203 m powder was obtained. The amount of Surflon S-112 deposited on the obtained cobalt-containing TFe203 magnetic powder was 35 g/g. Using the thus obtained cobalt-containing γ-Fe2Q3 magnetic powder, 100 parts by weight of CO-containing r-Fe203 magnetic powder (surflon S-112 coating amount 35 μ/g) was applied to VAGH (U.S. U, C, C manufactured by Narita Pharmaceutical Co., Ltd., 18 Vinyl chloride-vinyl acetate-vinyl alcohol copolymer> Takelac E-551T 12 (manufactured by Narita Pharmaceutical Co., Ltd., polyurethane elastomer) Desmodur L (manufactured by Bayer 3, trifunctional low molecular weight isocyanate compound ) Lauric acid 2 Cyclohexanone 80 Toluene
A magnetic paint was prepared by mixing and dispersing a mixture having a composition of 80% in a ball mill for about 100 hours. This magnetic paint was applied onto a 12 μm thick polyester film to a dry thickness of about 3 μm, dried, surface treated, and then cut to a predetermined width to produce a magnetic tape.

Comparative Example 1 A cobalt-containing γ-Fe203 magnetic powder was obtained in the same manner as in Example 1, except that the surface treatment of the cobalt-containing rFe2O3 magnetic powder in Example 1 was omitted, and the thus obtained cobalt-containing T- A magnetic tape was produced in the same manner as in Example 1, except that the same amount of Fe2O3 magnetic powder was used in place of the cobalt-containing T-Fe203 magnetic powder used in Example 1.

Comparative Example 2 In the surface treatment of the cobalt-containing r-Fe203 magnetic powder in Example 1, instead of Surflon S-112,
Cobalt-containing T-Fe20 was prepared in the same manner as in Example 1 except that the same amount of sodium dioctyl sulfosuccinate was used.
3 The magnetic powder was surface-treated, and instead of the cobalt-containing T-Fe203 magnetic powder used in Example 1, the same amount of cobalt-containing r-Fe203 magnetic powder coated with 35 μg/g of sodium dioctyl sulfosuccinate was used. A magnetic tape was made in the same manner as in Example 1.

Regarding the magnetic tapes obtained in Examples and Comparative Examples,
The output at 15K) Iz, DC noise, and surface roughness of the magnetic layer were measured. The surface roughness of the magnetic layer was measured using a stylus type surface roughness meter, and the numerical value of the surface roughness was expressed as a center line average (C, L, A).

The table below shows the results.

As is clear from the table above, the magnetic tape obtained by the present invention (Example 1) has a higher output and lower DC noise than conventional magnetic tapes (Comparative Examples 1 and 2), and The roughness is small, which indicates that the magnetic recording medium obtained by the present invention has excellent dispersibility of magnetic powder, good surface smoothness of the magnetic layer, and excellent electrical properties.

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Claims (1)

[Claims] 1. A magnetic recording medium containing magnetic powder, a perfluoroalkyl phosphate polymer, and a surfactant in the magnetic layer.