Abstract: A toner containing toner base particles and an external additive, wherein regions with different tribocharging polarities with respect to a magnetic carrier are present in a domain-matrix structure on the surface of the toner base particles. The island region B has a predetermined height, the external additive has a reverse polarity to the region B in terms of tribocharging polarity to the magnetic carrier, the external additive contains a first external additive having a number-average primary particle size of 80-150 nm and a second external additive having a number-average primary particle size of 10-60 nm, and an average coverage Cb (%) with the first external additive in the region B is 27-100% and a coverage Ca (%) with the first external additive in the sea region A is 12% or less.

Abstract: In the formation of images by a two-component development system, provided is a magnetic carrier that can be used to output an image which has sufficient density, in which few white spots are present in a low-density portion located near the boundary between a high-density region and a low-density region, and in which the low-density portion has good graininess. The magnetic carrier contains magnetic carrier particles each of which has resin and a magnetic particle. The magnetic particle contains ferrite phases and phases comprising a perovskite-structured compound. The ferrite phases and phases comprising a perovskite-structured compound are combined.

Abstract: An image forming apparatus includes a developer carrying member to which a developing bias is applied. A frequency f of a developing bias waveform, a developing area S1 which is a time-integrated value of a difference between a voltage value of the developing bias and a solid electrostatic image potential VL in a developing period of the developing bias, a collecting area S2 which is a time-integrated value of a difference between the voltage value of the developing bias and VL in a collecting period of the developing bias, and a developing contrast value Vcon are used for defining a range of a value of the developing bias frequency f, a range of a value of a voltage change rate ? at VL during transition of the developing bias voltage value from a developing-side voltage to a collecting-side voltage, and a range of a value represented by the formula: {(S1?1.28×S2)×f/Vcon}×exp(?2.0×10?5×f/Hz).

Abstract: A carrier has an impedance Z having a frequency dependence, obtained by alternating current impedance measurement. When the frequency dependence is fitted by a fitting function, parameter ? lies in a range of 0.70 to 0.90 in an electric field of 103 V/cm.

Abstract: An image forming apparatus includes a developer carrying member to which a developing bias is applied. A frequency f of a developing bias waveform, a developing area S1 which is a time-integrated value of a difference between a voltage value of the developing bias and a solid electrostatic image potential VL in a developing period of the developing bias, a collecting area S2 which is a time-integrated value of a difference between the voltage value of the developing bias and VL in a collecting period of the developing bias, and a developing contrast value Vcon are used for defining a range of a value of the developing bias frequency f, a range of a value of a voltage change rate ? at VL during transition of the developing bias voltage value from a developing-side voltage to a collecting-side voltage, and a range of a value represented by the formula: {(S1?1.28×S2)×f/Vcon}×exp(?2.0×10?5×f/Hz).

Abstract: A developer regulating apparatus including: a flexible sheet member, which regulates a thickness of a developer layer on a developing roller; and a holding member having wall surfaces for holding the sheet member in a curved state, wherein when the sheet member is not pressed by the developing roller, an angle of circumference of an arc of the sheet member is not larger than 180 degrees, a perpendicular bisector of a chord corresponding to the arc when the sheet member is pressed by the developing roller is provided downstream in a rotation direction of the developing roller with respect to a normal line of a surface of the developing roller which is parallel to the perpendicular bisector, and a sheet member holding line of the wall surface of the holding member upstream in the rotation direction is provided coplanar with the normal line or upstream of the normal line.

Abstract: A sheet-shaped regulation member is supported by a supporting unit with an elastic force occurring by bending a sheet-shaped regulation member in the longitudinal direction thereof, and a force received as a result of being pressed by a developing roller. Thus, direct contact can be securely made onto a developer bearing member, and a regulation member can be provided which enables easily attaching thereof to the supporting member, as well as enabling a developing apparatus, processing cartridge, and image forming apparatus, to be reduced in size.

Abstract: A sheet-shaped regulation member is supported by a supporting unit with an elastic force occurring by bending a sheet-shaped regulation member in the longitudinal direction thereof, and a force received as a result of being pressed by a developing roller. Thus, direct contact can be securely made onto a developer bearing member, and a regulation member can be provided which enables easily attaching thereof to the supporting member, as well as enabling a developing apparatus, processing cartridge, and image forming apparatus, to be reduced in size.