Patent ID: 7890033

Claim:
A developing device, comprising: a developing agent housing chamber which houses a non-magnetic one component developing agent, and which extends in a vertical direction, and has an aperture, in a lower portion thereof, that is in opposition to an image carrier that forms an electrostatic latent image; a developing roller which is provided in the aperture and whose peripheral surface is partly exposed from the aperture to form a developing portion with the image carrier, and which carries the non-magnetic one component developing agent on the surface of the developing roller and transports the developing agent by rotation from the developing agent housing chamber to the developing portion, in order to develop on the developing portion, the electrostatic latent image of the image carrier; a regulating blade, which is disposed higher than the center of rotation of the developing roller and is disposed to contact the surface of the developing roller in the vicinity of the aperture on an upstream side of the developing portion, in a transport direction of the developing roller, and which regulates a thickness of the non-magnetic one component developing agent transported on the developing roller; a supply roller which is disposed within the developing agent housing chamber to pressure-contact the developing roller on the upstream side with respect to the regulating blade in the transport direction of the developing roller, and which supplies the non-magnetic one component developing agent within the developing agent housing chamber to the surface of the developing roller; an agitator which is disposed higher than the developing roller, the regulating blade, and the supply roller, and which agitates the non-magnetic one component developing agent within the developing agent housing chamber; and a developing agent ingress prevention member disposed higher than the supply roller, and lower than the agitator, wherein a side surface or edge portion of the developing agent ingress prevention member in the vicinity of the developing roller is higher than the topmost point of the supply roller, and lower than the lowermost point of a regulating nip formed by the contact of the developing roller and the regulating blade, and the closest distance from the supply roller to a bottom surface of the developing agent ingress prevention member is greater than 0mm and less than 5mm.