A magnetic recording medium prepared from magnetic particles having a coating of very thin continuous amorphous aluminum hydrated oxide (an extremely thin, continuous amorphous, aluminum hydrous oxide coating)

摘要

As a first aspect, the present invention relates to a method for producing coated magnetic particles. According to the above method, the aqueous sol of amorphous hydrolyzed aluminum-containing colloid particles is mixed with an aqueous suspension containing magnetic particles. The average particle size of the amorphous hydrolyzed aluminum-containing colloidal particles is in the range of about 0.5 to 5 nm and the average degree of hydrolysis thereof is in the range of 1.5 to about 3. During mixing, the amorphous hydrolyzed aluminum-containing colloidal particles form a coating of continuous amorphous aluminum hydrated oxide on the magnetic particles, wherein the average thickness of the coating is in the range of about 0.5 to about 5 nm. The present invention also relates to coated magnetic particles. The coated magnetic particles according to the present invention comprise a magnetized core and a coating of continuous amorphous aluminum hydrated oxide formed on said magnetized core. The average thickness of the coating is in the range of about 0.5 to about 5 nm. As a second aspect, the present invention relates to a magnetic recording medium comprising a magnetic layer formed on a non-magnetizable support. The magnetic layer comprises the above-described coated magnetic particles dispersed in a polymeric binder.