Patent ID: 6682813
Filing Date: 2004-01-27
Classification: B22F,G11B,H01F,Y10T

Abstract:
A magnetic recording medium comprising:a non-magnetic substrate; and a magnetic layer formed on said substrate, comprising a binder resin and magnetic acicular alloy particles containing iron as a main component which have an average major axial diameter of 0.05 to 0.2 &mgr;m, an ammoniacal nitrogen content of 30 to 800 ppm based on said magnetic acicular alloy particles containing iron as a main component, soluble salts of not more than 800 ppm based on said magnetic acicular alloy particles containing iron as a and pH values of water suspensions of said magnetic acicular alloy particles containing iron as a main component, which satisfies the formula: (pH value of water suspension treated by A method)âˆ’(pH value of water suspension treated by B method)<0 whereinsaid A method comprises: placing 5 g of said magnetic acicular alloy particles in a hard conical flask; adding 100 ml of water into the flask; after heating to boiling for approximately 5 minutes, boiling the content of the flask for 5 minutes; compensating a reduced amount of water in the flask by adding thereto water which is previously boiled to remove a carbon dioxide gas therefrom; and after plugging the flask, allowing the content of the flask to stand for cooling to room temperature, said B method comprises: placing 5 g of said magnetic acicular alloy particles in a hard conical flask; adding 100 ml of water which is previously boiled to remove a carbon dioxide gas therefrom, into the flask; and after plugging the flask, shaking the content of the flask for 5 minutes, and the pH values of the respective water suspensions treated by said A and B methods are measured by a pH meter.