A developing device includes a development container, a developer carrying member, and a regulation blade. The development container is for containing a non-magnetic one-component developer composed only of the toner. The developer carrying member is manufactured by a polishing method and includes a rotary shaft and a roller portion stacked on an outer circumferential surface of the rotary shaft, and a toner layer is formed on the roller portion. The regulation blade contacts the outer circumferential surface of the roller portion so as to regulate a thickness of the toner layer. When ten-point average roughnesses in a circumferential direction and in an axial direction of the roller portion are indicated as Rz1 and Rz2, respectively, Rz1/Rz2?1.5 is satisfied, and a contact linear pressure of the regulation blade with respect to the roller portion is not less than 15 [N/m] and not more than 40 [N/m].

A toner includes binder resin 101 and a coloring agent 102. The coloring agent 102 is configured so that hue of a hue measurement print image printed on a print medium with the toner satisfies 8.6a*(Y)7.9 and 93.4b*(Y)95.4, where a*(Y) and b*(Y) represent an a* value and a b* value of the hue measurement print image and light resistance F of a light resistance measurement print image printed on a print medium with the toner, after an irradiation test in which the light resistance measurement print image is irradiated with light having 0.36 W/m.sup.2 spectral irradiance at a wavelength of 340 nm for 663 hours, is higher than or equal to 70%. The toner is configured so that its melt viscosity at 120 C. is higher than or equal to 1400 Pa.Math.s and lower than or equal to 1600 Pa.Math.s.

An image forming apparatus to perform an image forming operation for forming an image on a transfer material includes a photosensitive drum, a moving member, a detection unit, and a control unit. The detection unit detect information about a first movement in which the moving member moves from an open position to a shielding position or a second movement in which the moving member moves from the shielding position to the open position. During execution of a non-image forming operation, the control unit executes a multiple switching operation for performing a switching operation a plurality of times. The switching operation is an operation in which the control unit stops the photosensitive drum from being driven and then rotatably re-drives the photosensitive drum. Where the detection unit detects the information about the first movement or the second movement, the control unit performs control to execute the multiple switching operation.

An image forming apparatus includes a non-magnetic one-component developer, an image bearing member, and a development device that develops an electrostatic latent image formed on a surface of image bearing member by supplying non-magnetic one-component developer to the electrostatic latent image. Development device includes a development roller that carries non-magnetic one-component developer and a restricting member that restricts the thickness of a development layer constituted by non-magnetic one-component developer. Non-magnetic one-component developer contains a positively chargeable toner containing toner particles that include toner mother particles and external additive particles attached to the surfaces of toner mother particles and including resin particles and silica particles. When toner undergoes ultrasonic treatment that involves applying ultrasonic vibration at a frequency of 28 kHz and an output of 100 W for 5 minutes, resin particles and silica particles have detachment fractions within a range of 18% to 42%, and 5% to 25%, respectively.

The sensitivity of a sensor that detects the amount or density of magnetic substance is raised. The sensor includes an oscillation circuit, a differential transformer, and an amplification circuit. The oscillation circuit includes a resonance circuit having a coil. The differential transformer includes the coil, as a primary coil, and a secondary coil, and is configured such that, as the amount or density of magnetic substance as a detection target increases, a signal output from the secondary coil increases, and as the amount or density of magnetic substance decreases, the signal decreases. The amplification circuit amplifies the signal, and has, as its frequency characteristics, a frequency band such that, as the frequency of the signal decreases, the amplification factor of the signal increases, and as the frequency of the signal increases, the amplification factor of the signal decreases. The resonance frequency of the resonance circuit falls within the frequency band.

A developing device includes a development container, a developer carrying member, and a regulation blade. The development container is for containing a non-magnetic one-component developer composed only of the toner. The developer carrying member is manufactured by a polishing method and includes a rotary shaft and a roller portion stacked on an outer circumferential surface of the rotary shaft, and a toner layer is formed on the roller portion. The regulation blade contacts the outer circumferential surface of the roller portion so as to regulate a thickness of the toner layer. When ten-point average roughnesses in a circumferential direction and in an axial direction of the roller portion are indicated as Rz1 and Rz2, respectively, Rz1/Rz21.5 is satisfied, and a contact linear pressure of the regulation blade with respect to the roller portion is not less than 15 [N/m] and not more than 40 [N/m].

A cartridge to contain a developer includes a developing roller to carry the developer and a fur-brush type supplying roller to form a nip region with the developing roller to supply the developer to the developing roller. A surface layer of the developing roller includes a groove formed on the surface layer to come into contact with the fur-brush type supplying roller.

An image forming apparatus to perform an image forming operation for forming an image on a transfer material includes a photosensitive drum, a moving member, a detection unit, and a control unit. The detection unit detect information about a first movement in which the moving member moves from an open position to a shielding position or a second movement in which the moving member moves from the shielding position to the open position. During execution of a non-image forming operation, the control unit executes a multiple switching operation for performing a switching operation a plurality of times. The switching operation is an operation in which the control unit stops the photosensitive drum from being driven and then rotatably re-drives the photosensitive drum. Where the detection unit detects the information about the first movement or the second movement, the control unit performs control to execute the multiple switching operation.

A non-magnetic one-component developing toner comprises toner particles each including a toner core particle containing binder resin and a shell layer coating the toner core particle, and the toner particle contains no magnetic powder. The shell layer is formed using spherical resin particulates containing charge controlling resin. The toner particles have an average particle size of 6 m or more and 8 m or less, and when a surface of the toner particle is observed using a scanning electron microscope, a structure derived from the spherical resin particulates is not observed in the shell layer, and the outer surface of the shell layer is smoothed. When a cross section of the toner particle is observed using a transmission electron microscope, a crack derived from an interface between the resin particulates is observed inside the shell layer, in a direction substantially perpendicular to a surface of the toner core particle.

A cartridge to contain a developer includes a developing roller to carry the developer and a fur-brush type supplying roller to form a nip region with the developing roller to supply the developer to the developing roller. A surface layer of the developing roller includes a groove formed on the surface layer to come into contact with the fur-brush type supplying roller.