Patent ID: 7890028

Claim:
A developing device, comprising: a developer carrier that is provided opposite to an image carrier supporting a latent image on the surface, that supports a two-component developer comprising magnetic particles and toner on the surface, and that forms a developing gap between the image carrier, the developing device developing the latent image by moving the toner on the developer carrier to the image carrier side, wherein the amount of developer carried per unit area on the developer carrier is 30 mg/cm 2 or more and 60 mg/cm 2 or less in a developing region where toner on the developer carrier is moved to the image carrier side; the weight mean particle diameter of the toner is 4.5 μm or more and 8.0 μm or less, and the ratio Dw/Dn of the toner weight mean particle diameter (Dw) and the number mean particle diameter (Dn) is 1.20 or less; the maximum height Rz of the surface roughness of the developer carrier is 20 to 40 μm, the mean space Sm of the roughness of the developer carrier surface is 100 to 200 μm, and the surface roughness of the developer carrier has an irregular height and space roughness pattern; and the value, which is obtained by dividing the gap DG between the developer carrier and a developer restricting member provided opposite to the developer carrier and restricting the amount of developer transported to the development region, by the developing gap PG between the image carrier and the developer carrier, is 1.0 or more and 3.0 or less.