DEVELOPING DEVICE

摘要

PROBLEM TO BE SOLVED: To obtain a developing device where the amount of developer carried to a developing area is regulated by brining a regulating member into press- contact with the surface of a developer carrier and by which a situation that the developer is cracked by the press-contact of the regulating member and impalpable powder is produced is restrained, and the filming of the developer on the surface of the developer carrier or surface fogging on a formed image is restrained. SOLUTION: In this developing device, the amount of the developer carried to the developing area is regulated by bringing the regulating member 15 into press-contact with the surface of the developer carrier 11 carrying the developer 12 to the developing area opposed to the image carrier 1 and the developer is triboelectrified. Then, an elastic layer 11b is provided on the surface of the developer carrier, and toner using polyester resin whose acid number is within the range of 1 to 30 KOHmg/g and electrified to be negative is used as the developer, and the work function Wf(eV) in the elastic layer and the acid number An(KOHmg/g) of the polyester resin are set to satisfy a condition 4.25