Patent Number: 6,780,555

Title: Black magnetic iron oxide particles and magnetic toner

Abstract: Black magnetic iron oxide particles having an average particle diameter of 0.05 to 1.0 .mu.m have a three-phase structure comprising: a core portion containing at least one metal element other than Fe selected from the group consisting of Mn, Zn, Cu, Ni, Cr, Cd, Sn, Mg, Ti, Ca and Al in an amount of 0.1 to 10% by weight based on whole Fe contained in the particles; a surface coat portion containing at least one metal element other than Fe selected from the group consisting of Mn, Zn, Cu, Ni, Cr, Cd, Sn, Mg, Ti, Ca and Al in an amount of 0.1 to 10% by weight based on whole Fe contained in the particles; and an intermediate layer disposed between the core portion and the surface coat portion, containing substantially none of the metal elements other than Fe.

Inventors: Uchida; Naoki (Otake, JP), Kouzawa; Minoru (Hiroshima, JP), Misawa; Hiromitsu (Hatsukaichi, JP), Aoki; Koso (Hiroshima, JP), Miura; Suehiko (Hiroshima, JP)

Assignee: Toda Kogyo Corporation

International Classification: G03G 9/083 (20060101); H01F 1/032 (20060101); H01F 1/11 (20060101); G03G 009/083 (); B32B 009/000 ()

Expiration Date: 08/24/2012