Patent ID: 7962076

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 having a negative charging property to a first developing position to develop a first electrostatic image formed on said first image bearing member with the black developer; a first voltage source that applies a first bias voltage to said first developer carrying member; a first supplying member that supplies the black developer to said first developer carrying member; a second voltage source that applies, to said first supplying member, a second bias voltage, wherein the first bias voltage is more positive than the second bias voltage; a second image bearing member; a second developer carrying member, contactable to said second image bearing member, that carries a chromatic developer having a negative charging property to a second developing position to develop a second electrostatic image formed on said second image bearing member with the chromatic developer; a third voltage source that applies a third bias voltage to said second developer carrying member; a second supplying member that supplies the chromatic developer to said second developer carrying member; and a fourth voltage source that applies, to said second supplying member a fourth bias voltage, wherein the third bias voltage is more positive than the fourth bias voltage, 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, an arithmetic average roughness Ra of a surface of said first developer carrying member is not less than 0.20 times and not more than 0.33 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 not less than 0.20 times and not more than 0.33 times a volume average particle size of the chromatic developer, 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.