Patent ID: 9213251
Filing Date: 2015-12-15
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 strontium titanate fine particles and 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, the content of the strontium titanate fine particles, expressed with reference to the total amount of the magnetic toner, is from at least 0.1 mass % to not more than 3.0 mass %, the number-average particle diameter (D in a magnetic separation test during the application of a negative voltage, the release rate for the strontium titanate fine particles is at least 10%, and the ratio [D