Patent ID: 8019260

Claim:
An image forming apparatus comprising: a first image bearing member; a first developer carrying member, contactable to said first image bearing member, that carries a black developer to a first developing position to develop a first electrostatic image formed on said first image bearing member with the black developer; a first developer regulating member, contacted to the surface of said first developer carrying member, that regulates an amount of the black developer carried on said first developer carrying member; a second image bearing member; a second developer carrying member, contactable to said second image bearing member, that carries a chromatic developer to a second developing position to develop a second electrostatic image formed on said second image bearing member with the chromatic developer; and a second developer regulating member, contacted to the surface of said second developer carrying member, that regulates an amount of the chromatic developer carried on said second developer carrying member, wherein a peripheral speed of said first developer carrying member is not less than 1.05 times and not more than 1.20 times a peripheral speed of said first image bearing member, and a peripheral speed of said second developer carrying member is not less than 1.05 times and not more than 1.20 times a peripheral speed of said second image bearing member, wherein an arithmetic average roughness Ra of a surface of said first developer carrying member is less than 0.20 times a volume average particle size of the black developer, and an arithmetic average roughness Ra of a surface of said second developer carrying member is less than 0.20 times a volume average particle size of the chromatic developer, wherein a potential of said first developer regulating member is different from a potential of said first developer carrying member toward a larger potential of a regular charge polarity of the black developer, and a potential of said second developer regulating member is different from a potential of said second developer carrying member toward a larger potential of a regular charge polarity of the chromatic developer, wherein a potential difference between the potential of said first developer regulating member and the potential of said first developer carrying member is not less than 50V and not more than 250V, and a potential difference between the potential of said second developer regulating member and the potential of said second developer carrying member is not less than 50V and not more than 250V, and wherein a ratio of the peripheral speed of said second developer carrying member to the peripheral speed of said second image bearing member is smaller than a ratio of the peripheral speed of said first developer carrying member to the peripheral speed of said first image bearing member.