Patent ID: 7572505
Filing Date: 2009-08-11
Classification: C01G,C01P,C08K,C09C,C09D,G03G,H01F,Y10S,Y10T

Abstract:
1. Black magnetic iron oxide particles comprising core particles and a surface layer formed on a surface of the respective core particles, the surface layer consisting of a compound of at least one alkali earth metal element selected from the group consisting of Mg, Ca, Sr and Ba and an aluminum element, in which a content of the at least one alkali earth metal element present in the surface layer is from 100 ppm to 1000 ppm on the basis of a whole weight of the black magnetic iron oxide particles; a content of the aluminum element present in the surface layer is from 1000 ppm to 20000 ppm on the basis of a whole weight of the black magnetic iron oxide particles; a ratio [A/B] of the content [A (ppm)] of the aluminum element to the content [B (ppm)] of the at least one alkali earth metal element present in the surface layer is from 1 to 100; and said black magnetic iron oxide particles have a breakdown voltage of not less than 400 V/cm.