An image forming apparatus includes a main body provided with a mounting portion and an interference member, and a toner cartridge inserted into the mounting portion. The toner cartridge includes a housing containing toner, a coupling portion, a front cover coupled to one end of the housing via the coupling portion, and a switching member to weaken a coupling force of the coupling portion by interfering with the interference member when the toner cartridge is mounted on the mounting portion.

A developer cartridge includes a housing to accommodate a developer and including a developer outlet, and a sensing portion that forms a sensing area to detect whether or not the developer inside the housing is miming out. The sensing portion is recessed into a portion of a lower wall of the housing accordingly having a thickness less than a thickness of a remaining portion of the lower wall.

Provided is an electrostatic charge image developing toner including toner matrix particles containing at least a binder resin, wherein a photosensitizer having a singlet oxygen generating ability is contained inside the toner matrix particles or in an external additive attached to the toner matrix particles.

Provided is an electrostatic charge image developing toner including toner matrix particles containing at least a binder resin, wherein a photosensitizer having a singlet oxygen generating ability is contained inside the toner matrix particles or in an external additive attached to the toner matrix particles.

According to the present invention, there is provided a carrier core material that is formed of ferrite particles in which 48 to 52 mass % of Fe, 16 to 22 mass % of Mn, 1.0 to 3.5 mass % of Mg and 0.05 to 0.5 mass % of Ca are included, and when an electrical resistance value with an applied voltage of 500 V in an environment (in an L/L environment) in which the temperature is 10° C. and the relative humidity is 35% is R.sub.L (Ω.Math.cm), and an electrical resistance value with an applied voltage of 500 V in an environment (in an H/H environment) in which the temperature is 30° C. and the relative humidity is 70% is R.sub.H (Ω.Math.cm), formula (1) below is satisfied.
0.1≤(log R.sub.L−log R.sub.H)≤0.3  (1)

An image forming system includes a toner container and an image forming apparatus, the toner container including a first toner containing portion, a container base portion having a discharge port for discharging toner, and a container shutter that is moved between open and closed positions and includes an engaged portion, wherein the image forming apparatus includes a main body base portion that detachably attaches the toner container and has a receiving port for receiving the toner and, a second toner containing portion, a movable member that is moved between first and second positions and includes an engaging portion that engages with the engaged portion, a regulating member that is moved between a regulation position and a regulation release position, and an urging member that urges the movable member to move from the first position to the second position when the regulating member is located at the regulation release position.

An image formation apparatus includes an image-bearing member, an exposure device, an electro-conductive member, a bias application unit and a development device having a development roller and a toner supply roller. The bias application unit configured to apply biases to the toner supply roller, the development roller, and the electro-conductive member during image formation so that a first potential difference between the toner supply roller and the development roller and a second potential difference between the electro-conductive member and the development roller cause normally charged toner to travel respectively from the toner supply roller and the electro-conductive member to the development roller, and a third potential difference between the electro-conductive member and the toner supply roller causes normally charged toner to travel from the electro-conductive member to the toner supply roller. The second potential difference is larger than the first potential difference and is larger than the third potential difference.

A developing device includes a development casing, a developer carrying member, a regulating blade, a pair of pressing members, and a blade seal member. The development casing has an opening part. The developer carrying member has a developing area. The blade seal member includes a first layer material and a second layer material. The development casing has facing surfaces. The second layer material has positioning protrusions protruding from the first layer material in a rotation axis direction at positions inside both ends of the first layer material in the rotation axis direction, so as to contact the facing surfaces and be positioned in the rotation axis direction. When the second layer material is positioned in the rotation axis direction, the first layer material is pressed in contact with the pressing members in the rotation axis direction.

An electroconductive elastic body includes: a cross-linked product of a first ionic electro-conductive rubber, a cross-linked product of a second ionic electro-conductive rubber, and at least one of a fatty acid and a fatty acid metal salt; wherein the electroconductive elastic body has a matrix that includes the cross-linked product of the first ionic electro-conductive rubber, and a domain that includes the cross-linked product of the second ionic electro-conductive rubber; the cross-linked product of the second ionic electro-conductive rubber includes a polyether skeleton; an electrical resistance of the domain is lower than an electrical resistance of the matrix; in a waveform separation profile of the elastic body as obtained by a small-angle X-ray scattering method, A2 and A1 satisfy a relationship expressed by the following expression (1):
0.005≤(A2×C2/A1×C1)≤0.030  (1).

A toner container information acquiring method includes: measuring a toner amount contained in a resin forming a toner container; and acquiring information regarding mechanical strength of the toner container based on the measured toner amount.