JPS59172146A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the wear resistance of a magnetic layer and to improve the durability by applying an organic solvent type magnetic coating material containing oxide magnetic powder, on the grain surface of which a specific compound is attached, and binder onto a base. CONSTITUTION:An organic solvent type magnetic coating material containing oxide magnetic powder, on the grain surface of which a compound of an alkaline earth metal is attached, and binder is used as the magnetic coating material to be applied to the surface of a base. To make the surface treatment of the magnetic powder, the hydrochloride or sulfate of an alkaline earth metal is dissolved in an acidic aqueous solution and the magnetic powder is put into the solution thus prepared. The solution is then neutralized by adding an alkali, such as caustic alkali, etc., while the magnetic powder is dispersed and mixed into the solution. After the solution is neutralized, the magnetic powder is taken out from the solution and dried by heating. As a result, a film of strongly bonded compound of alkaline earth metal (usualy: oxide) is formed on the surface of each magnetic powder. It is desirable to set the attaching amount of the compound at a ratio of >=0.01wt% of the magnetic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape or other magnetic recording medium using magnetic powder such as metal powder or magnetic oxide powder as a recording element.

This type of magnetic recording medium is generally made by making a magnetic material by mixing and dispersing magnetic powder such as metal powder or magnetic oxide powder and a binder in an organic solvent, and then coating this on a base. However, conventional magnetic recording media made using this method lack durability, perhaps due to poor wear resistance of the magnetic layer.

This invention was discovered as a result of intensive studies to avoid the above problems, and its gist is that an organic solvent-based magnetic powder containing an alkaline earth metal compound attached to the particle surface and a binder. This is a magnetic recording medium made by coating a magnetic paint on a base.

That is, in this invention, when preparing an organic solvent-based magnetic paint by mixing A6 powder such as metal powder or magnetic oxide powder with a binder, the magnetic powder is surface-treated with an alkaline earth metal compound. It has been found that in some cases, the abrasion resistance of the magnetic layer formed by coating this type of material on a base is significantly improved, and a magnetic recording medium with good durability can be obtained.

A method for surface treatment of magnetic powder is to dissolve alkaline earth metal hydrochloride or sulfate in an acidic aqueous solution, add the magnetic powder to the solution, disperse and mix, and neutralize by adding an alkali such as caustic alkali. After that, you can take it out and heat dry it. As a result, a film of an alkaline earth metal compound (generally an oxide) bonded relatively firmly to the surface of the magnetic powder is formed.

The alkaline earth metals include Ca, Mg, Bay, (
which is preferably used. The amount of this metal compound attached should be such that it accounts for 0.01% by weight or more in the total amount of magnetic powder, but if too much is attached, good results may not be obtained in terms of magnetic properties. to preferably 0
It is 5% by weight or less.

Magnetic powders include metal magnetic powders such as Fe powder, SiO powder, and alloy powders, as well as iron oxide magnetic powders such as γ-Fe203 powder, Fe3O4 powder, or their intermediate oxidation states, and iron oxide magnetic powders containing iron. A wide range of oxide magnetic powders such as powders are included.

Among these, the effect of the present invention becomes more remarkable when cobalt-containing iron oxide magnetic powder, particularly the above-mentioned magnetic powder of the type in which cobalt is deposited on the particle surface, is used.

A wide range of conventional binders can be used to disperse and bind the oxide magnetic powder treated with the alkaline earth metal compound, such as polyester resin,
Examples include various resins such as polyurethane resin-cellulose resin, polyvinyl butyral resin, vinyl chloride-vinyl acetate copolymer resin, and vinylidene chloride resin, or those in combination with a low molecular weight isocyanate compound as a crosslinking agent.

In this invention, a magnetic paint is prepared by dissolving and dispersing the above magnetic powder and binder in an organic magent, but the organic solvent used here is not particularly limited, and various solvents such as cyclohexanone-toluene and methyl ethyl ketone can be used. Available for use.

The magnetic tape or other magnetic recording medium of the present invention having good durability can be obtained by applying the magnetic paint prepared by the above method onto a base such as a polyester film by a conventional method and drying it.

Examples of this invention will be described below. In the following, parts shall mean parts by weight.

Example: Calcium chloride was used as the alkaline earth metal compound and dissolved in an acidic water bath solution (P) (Prepare a bath solution of 6,5, and add 0-containing γ-Fe2O3 powder to this solution. The mixture was stirred and mixed.While stirring and mixing, an aqueous solution of caustic soda was added dropwise to adjust the pH of the liquid to 9.0.Then, the magnetic powder was taken out and dried by heating to form the alkaline earth metal oxide on the particle surface. Coated CO
Gold-containing γ-Fe2O3 powder was obtained. The coating amount of this magnetic powder was 0.05% by weight.

A magnetic paint was prepared using the above surface-treated magnetic powder with the following composition.

Surface treated magnetic powder 100 parts nitrified cotton
15 parts polyurethane resin
Part 15 Dismodule L
Part 5 Q Director A (-Kinmushi Watato Ashi Σ3F Yume Sumi Insia Fu-H Hitsukuda) Methyl ethyl ketone 80 parts Toluene 80 parts Stearic acid
1 part of the above magnetic material was placed on a 15 μm thick polyester base film with a thickness of 5 μm after drying.
The magnetic tape of the present invention was cut into pieces having a width of 1.2'7 AI.

A steel test (normal temperature steel regeneration time) was conducted to examine the durability characteristics of this tape, and the results were as follows.The comparative example below refers to untreated γ-F
These are the results when e2O3 powder was used.

Steel test (minutes) Example 60 or more Comparative example 20 As is clear from the above results, it can be seen that the magnetic tape of the present invention has extremely excellent durability.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

[Claims] (1) A magnetic recording medium in which an organic solvent-based magnetic paint containing a binder and magnetic powder with an alkaline earth metal compound attached to the particle surface is applied onto a base.