Patent ID: 9217943
Filing Date: 2015-12-22
Classification: G03G

Abstract:
1. A magnetic toner comprising: magnetic toner particles comprising a binder resin and a magnetic body; and inorganic fine particles present on the surface of the magnetic toner particles, wherein; the inorganic fine particles present on the surface of the magnetic toner particles comprise metal oxide fine particles, the metal oxide fine particles containing silica fine particles, and optionally containing titania fine particles and alumina fine particles, and a content of the silica fine particles being at least 85 mass % with respect to a total mass of the silica fine particles, the titania fine particles and the alumina fine particles, wherein; when a coverage ratio A (%) is a coverage ratio of the magnetic toner particles' surface by the inorganic fine particles and a coverage ratio B (%) is a coverage ratio of the magnetic toner particles' surface by the inorganic fine particles that are fixed to the magnetic toner particles' surface, the magnetic toner has a coverage ratio A of at least 45.0% and not more than 70.0% and a ratio [coverage ratio B/coverage ratio A] of the coverage ratio B to the coverage ratio A of from at least 0.50 to not more than 0.85, and the binder resin is a styrene resin; for a weight-average molecular weight (Mw) and an radius of gyration (Rw) measured on the ortho-dichlorobenzene-soluble matter from the magnetic toner in use of size exclusion chromatograph with a multiangle laser light scattering (SEC-MALLS), the weight-average molecular weight (Mw) is from at least 5000 to not more than 20000 and the ratio [Rw/Mw] of this radius of gyration (Rw) to the weight-average molecular weight (Mw) is from at least 3.0×10 the viscosity of the magnetic toner at 110° C. measured by a flow tester/temperature ramp-up method is from at least 5000 Pa·s to not more than 25000 Pa·s.