A developing device, including a casing and a seal member is provided. The casing includes a divider wall, dividing a space inside the casing into a container chamber and a developing chamber, and a developing roller. The divider wall includes an opening. The container chamber accommodates a developing agent. The seal member is configured to seal the opening. The seal member includes a ventilation section configured to allow air to pass there-through but restrict the developing agent from passing there-through at least at a part of an area that seals the opening.

A toner has excellent low temperature fixing property, heat resistant preservability, and stable image quality. The toner contains a core including a crystalline polyester, and a shell formed on a surface of the core. An aspect ratio of the crystalline polyester in the toner is within a range from 1 to 3, and an average length of a longitudinal diameter of the crystalline polyester is within a range from 10 nm to 500 nm.

A direction in which a first drive transmission gear urges a first drive gear using a first urging portion when a drive force is not input to a first drive input portion is defined as a first direction. A direction in which a second drive transmission gear urges a second drive gear using a second urging portion when a drive force is not input to a second drive input portion is defined as a second direction. The second direction has a force component in a direction opposite to the first direction with respect to a straight line connecting a rotation center of the first drive gear and a rotation center of the second drive gear.

An electrophotographic photosensitive member that is excellent in image smearing resistance and low torque while maintaining its electrophotographic characteristic. The electrophotographic photosensitive member is an electrophotographic photosensitive member including, in this order: a support; a photosensitive layer; and a protection layer as a surface layer, wherein the protection layer has a surface having a developed area ratio Sdr of 1.0% to 40.0%, and wherein an A value represented by the following formula (1) is 0.10 to 0.27: A=S1/S2 . . . formula (1), where, in the formula (1), S1 represents a peak area based on C═C stretching vibration of an aromatic ring by attenuated total reflection Fourier transform infrared spectroscopy, and S2 represents a peak area based on C═O stretching vibration of an ester group by the same method.

An apparatus includes a developer container to and from which a replenishment container is attachable and detachable and which includes an accommodating portion and a replenishment port, a transfer portion configured to transfer a developer image on an image bearing member onto a recording material, a supporting tray including a supporting surface configured to support the recording material thereon, and a discharge portion configured to discharge the recording material, onto which the developer image has been transferred, on the supporting surface, wherein the supporting surface has an opening portion opening such that the replenishment port is exposed through the supporting surface, and wherein an opening/closing member configured to be movable between a closed position where the opening/closing member covers the replenishment port and serves as a part of the supporting surface and an open position where the replenishment port is exposed is provided.

A developing device includes a developer cartridge and a developing unit. The developer cartridge, in some instances, may include a shutter. This shutter may have a wall for closing a developer supply hole, and be movable, with respect to a developer cartridge casing, between an open position where the supply hole is opened by the wall and a closed position where the supply hole is closed by the wall. The shutter may further include a protrusion that is movable with respect to the wall of the shutter between a first position and a second position in an axial direction. The protrusion, in the first position, is engageable with a developing unit and, in the second position, would be disengaged from the developing unit.

An image forming apparatus includes a development cartridge having a developing roller. The developing roller includes a roller body, and a shaft to pass through a central axis of the roller body. A coupling structure is disposed at an end part of the shaft, is movable from a first position to a second position, and includes a first coupling piece and a second coupling piece. Positions of the first coupling piece and the second coupling piece are maintained with respect to one another by a static frictional force between surfaces of the first coupling piece and the second coupling piece to hold the coupling structure in the first position. When a predetermined force overcomes the static frictional force, the first coupling piece and the second coupling piece disengage from one another to allow the coupling structure to move from the first position to the second position.

A drum cartridge includes: a photosensitive drum rotatable about an axis extending in a first direction; a first drum frame to which a developing cartridge is attachable; and a second drum frame having an outer surface; and a memory having an electrical contact surface. The first drum frame is at one end portion of the drum cartridge in a second direction and the second drum frame is at another end portion of the drum cartridge in the second direction. The electrical contact surface is positioned at the outer surface of the second drum frame and is movable in a predetermined direction relative to the second drum frame.

A developing cartridge includes: a casing; a developing roller extending in a first direction; a boss movable with the casing; and a first lever movable relative to the casing. The first lever includes: one end portion functioning as a point of effort; another end portion functioning as a point of load; a shaft functions as a fulcrum and positioned between the one end portion and the another end portion; and a first hole into which the boss is fitted. By the one end portion receiving a driving force, the first lever is pivotally movable about the shaft. A dimension of the first hole in a second direction crossing the first direction is greater than a dimension in the second direction of the boss. In a case where the casing moves in the second direction relative to the first lever, the boss moves in the second direction within the first hole.

An electrostatic image developing toner includes toner particles, an external additive A, and an external additive B. At least the external additive A is deposited on the surfaces of the toner particles. At least the external additive B is deposited on the external additive A. The external additive B includes an aggregate of two or more particles. The coverage of the toner particles with the external additive B is 3% by area or more with respect to the total surface area of the toner particles.