Patent ID: 8883389

Claim:
A developing apparatus comprising an electrostatic latent image bearing member on which an electrostatic latent image is formed, magnetic toner for developing the electrostatic latent image formed on the electrostatic latent image bearing member, a magnetic toner-carrying member arranged so as to oppose the electrostatic latent image bearing member for carrying and transporting the magnetic toner, and a toner regulating member contacting the magnetic toner-carrying member and regulating the magnetic toner carried on the magnetic toner-carrying member, wherein: the magnetic toner-carrying member has a work function value of 4.6 eV or more and 4.9 eV or less, a portion of the toner regulating member, which is contacting the magnetic toner, is made of a polyphenylene sulfide or a polyolefin, and the magnetic toner i) comprises magnetic toner particles, each of which contains a binder resin and magnetic powder, and inorganic fine powder, ii) has negative charging property, iii) has an average circularity of 0.950 or more, and iv) has a surface tension index I for a 45 volume % aqueous solution of methanol measured by the capillary suction time method and calculated by the following equation (1) of 5.0×10 −3 N/m or more and 1.0×10 −1 N/m or less: I=P α/( A×B× 10 6 ) (1) wherein in the equation (1), I represents the surface tension index (N/m) of the magnetic toner; Pα represents a capillary pressure (N/m 2 ) of the magnetic toner for the 45 volume % aqueous solution of methanol; A represents a specific surface area (m 2 /g) of the magnetic toner; and B represents a true density (g/cm 3 ) of the magnetic toner.