| 摘要 |
Provided is magnetic toner capable of favorably maintain fluidity of the magnetic toner in a developing unit even after a large number of image formation. The magnetic toner to which an external additive that has 1) a number average particle diameter of 70 or more and 200 or less, 2) a shape factor SF-1 of 100 or more and 250 or less, and 3) a shape factor SF-2 of 105 or more and 250 or less, is added, and a covering rate by silica on the surfaces of toner particles is 40.0% or more and 70.0% or less, and the magnetic toner has specific fluidity. |
| 主权项 |
1. Magnetic toner comprising:
magnetic toner particles, each of which contains a binder resin and a magnetic material; and a first external additive, wherein the first external additive 1) is silica fine particles, or resin composition-silica composite particles, 2) has a number average particle diameter of 70 nm or more and 200 nm or less, 3) has a shape factor SF-1 of 100 or more and 250 or less, and 4) has a shape factor SF-2 of 105 or more and 250 or less, and a covering rate of surfaces of the magnetic toner particles by silica measured by X-ray photoelectron spectroscopic analysis (ESCA) is 40.0% or more and 70.0% or less, and total energy calculated from a rotation torque and a vertical load is 80.0 mJ or more and 140.0 mJ or less, the rotation torque and the vertical load being obtained by the following steps of: putting the magnetic toner in the measurement container; compressing the magnetic toner put in the measurement container with a load of 5.8 kPa, and forming a compressed toner layer; and advancing a propeller type blade into the compressed toner layer at a constant speed vertically with respect to the surface of the compressed toner layer, the propeller type blade rotating at an outermost edge's peripheral speed of 100 mm/sec. |
