| 摘要 |
PROBLEM TO BE SOLVED: To reduce the damage on a developer, optimize and stabilize the electrification quantity of toner when a copier is repeatedly used, and form a high-quality image as a result. SOLUTION: When the electrostatic latent image 4 on an electrostatic latent image carrier 3 is developed by a developer layer 2 carried on a developer carrier 1, the moving direction of the developer carrier 1 is made the same direction as the moving direction of the electrostatic latent image carrier 3. The peripheral speed ratio between the developer carrier 1 and the electrostatic latent image carrier 3 is set to 0.5-1.8. A developer is composed of a carrier and toner. The shape factor SF1 of the toner expressed by the equation (1 meets the condition expressed by the equation (A), and the shape factor SF2 expressed by the equation (2) meets the condition expressed by the equation (B), where (1): SF1 = (maximum length of diameter)<2>×100π/4, (2): SF2 = (peripheral length of projected image)<2>×100/(4π), (A):120<=SF1<=160, (B): 110<=SF2<=130.
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