MAGNETIC TONER Russian patent published in 2018 - IPC G03G9/83 

FIELD: physics.

SUBSTANCE: toner contains magnetic toner particles having a resin binder and a magnetic material and inorganic fine particles attached to the surface of the magnetic toner particles, where when the inorganic fine particles are classified according to the strength of their fixing to the magnetic toner particles and in order of weakening of the fixing strength as weakly-fixed inorganic fine particles, medium-fixed inorganic fine particles and firmly-fixed inorganic fine particles. The content of weakly-fixed inorganic fine particles is at least 0.10 wt parts to not more than 0.30 wt parts per 100 wt parts of the magnetic toner, medium-fixed inorganic fine particles are present at a content that is from at least 2.0 times to no more than 5.0 times the content of weakly-fixed inorganic fine particles. The degree of X surface covering of the magnetic toner by the firmly-fixed inorganic fine particles when determined by the X-ray photoelectron spectrometer (ESCA) is from at least 60.0% of the area to no more than 90.0% of the area, and wherein the weakly-fixed inorganic fine particles are inorganic fine particles, which are separated when a dispersion prepared by adding a magnetic toner to water purified by ion exchange containing a surfactant, is shaken for 2 minutes at a shaking speed of 46.7 cm/s and amplitude of shaking of 4.0 cm. The medium-fixed inorganic fine particles are inorganic fine particles which are not separated by shaking but determined by ultrasonic dispersion for 30 minutes at the intensity of 120 W/cm². The firmly-fixed inorganic fine particles are inorganic fine particles which are not separated by shaking and ultrasonic dispersion.

EFFECT: exhibits excellent uniformity of charge characteristics, uniformity of charge characteristics even after a long-life test in a system with a high operating speed to maintain higher speeds and when using a roller with a reduced diameter in favour of reducing the size of the device, can suppress the formation of image defects associated with heterogeneity of charging.

10 cl, 5 dwg, 7 tbl