Developing apparatus, process cartridge, and electrophotographic image forming apparatus

An electrophotographic image forming apparatus comprising the developing apparatus, wherein

• the developing apparatus comprising:
• a toner comprising a toner particle and an external additive;
• a toner carrying member for carrying the toner;
• and
• a charging member used for injecting charge into the toner carried on the toner carrying member, wherein
• the external additive comprises a fine particle A and a fine particle B,
• the fine particle A is at least one fine particle selected from a group consisting of a silica fine particle and a silicone fine particle,
• the fine particle B is at least one fine particle selected from a group consisting of a fine particle of antimony-tin oxide-titanium oxide, a fine particle of an antimony-titanium oxide, a fine particle of an antimony-tin oxide, a fine particle of indium-tin oxide, a fine particle of indium-titanium oxide, a fine particles of niobium-tin oxide, a fine particle of niobium-titanium oxide, and a fine particle of zinc oxide,
• the toner carrying member is a developing roller having:
• a substrate having an outer surface having conductivity;
• and
• a resin layer on the outer surface of the substrate,
• a metal film is directly provided on an outer surface of the developing roller, and under an environment of 23° C. temperature and 50% relative humidity, when an AC voltage of which an amplitude is 50 V is applied between the outer surface of the substrate and the metal film with a frequency changing in a range of 1.0×10−1 to 1.0×105 Hz while a DC voltage of 50 V is applied therebetween, an impedance at the frequency of 1.0×100 to 1.0×101 Hz is 1.00×106Ω or more, and
• when under an environment of 23° C. temperature and 50% relative humidity, a corona discharger having a grid portion of which a width is 3.0 mm is arranged such that a distance between the grid portion and the outer surface of the developing roller is 1.0 mm, and a direction of the width of the grid portion coincides with an axial direction of the developing roller, and when a voltage of 8 kV is applied to the grid portion, and the outer surface of the developing roller is charged by relatively moving the corona discharger in the axial direction of the developing roller at the speed of 400 mm/sec, a maximum value of an electric potential is less than 20.0 V when the electric potential of the outer surface is measured after 0.06 seconds from passage of the grid portion.

A developing apparatus comprising:

• a toner comprising a toner particle and an external additive;
• a toner carrying member used for carrying the toner;
• and
• a charging member used for injecting charge into the toner carried on the toner carrying member, wherein
• the external additive comprises a fine particle A and a fine particle B,
• the fine particle A is at least one fine particle selected from a group consisting of a silica fine particle and a silicone fine particle,
• conductivity of the fine particle B acquired through impedance measurement is 1.0×10−5 to 1.0×102 S/m,
• the toner carrying member is a developing roller having a substrate that has an outer surface having conductivity and a resin layer on the outer surface of the substrate,
• a metal film is directly provided on an outer surface of the developing roller, and under an environment of 23° C. temperature and 50% relative humidity, when an AC voltage of which an amplitude is 50 V is applied between the outer surface of the substrate and the metal film with a frequency changing in a range of 1.0×10−1 to 1.0×105 Hz while a DC voltage of 50 V is applied therebetween, an impedance at the frequency of 1.0×100 to 1.0×101 Hz is 1.00×106Ω or more, and
• when under an environment of 23° C. temperature and 50% relative humidity, a corona discharger having a grid portion of which a width is 3.0 mm is arranged such that a distance between the grid portion and the outer surface of the developing roller is 1.0 mm, and a direction of the width of the grid portion coincides with an axial direction of the developing roller, and when a voltage of 8 kV is applied to the grid portion, and the outer surface of the developing roller is charged by relatively moving the corona discharger in the axial direction of the developing roller at the speed of 400 mm/sec, a maximum value of an electric potential is less than 20.0 V when the electric potential of the outer surface is measured after 0.06 seconds from passage of the grid portion.