Patent ID: 7457571

Claim:
An image forming apparatus comprising: an image carrier which holds an electrostatic latent image on the surface thereof; a developer carrier, having internally fixed magnetic field generating means which rotates while holding a two-component developer comprising a magnetic carrier and a toner on the surface thereof to oppose the image carrier; and developing electric field generating means which generates a developing electric field between said image carrier and said developer carrier; wherein the electrostatic latent image on said image carrier is converted into a toner image by the action of said developing electric field, using said toner of said two-component developer held on said developer carrier; the volume-average particle size of said toner is 5.5 through 8.0 (μm); the volume-average particle size of said magnetic carrier is 20 through 40 (μm); the gap between said image carrier and said developer carrier is 0.3 through 0.6 (mm) and the tolerance is within ±0.125 (mm); and 0.2 through 0.7 (wt %) of hydrophobic silica having a particle size of 100 (nm) or above, 1.0 through 2.0 (wt %) of hydrophobic silica having a particle size of 20 (nm) or below, and 0.7 through 1.0 (wt %) of titanium oxide are added to said toner.