Patent ID: 7079795

Claim:
An image forming apparatus comprising: a first developing device containing a black developer including black chromatic toner and a carrier and for developing an electrostatic image with the black chromatic toner, wherein a resistivity of the carrier in the black developer is not less than 1.0×10 9 Ωcm and not more than 1.0×10 10 Ωcm; a first developer supply device for supplying a black supply developer including black chromatic toner and a carrier into said first developing device, wherein a weight ratio of the carrier in the black supply developer is not less than 10 Wt % and not more than 40 Wt %; a first developer discharging means for discharging the developer from said first developing device; a second developing device containing a chromatic developer including chromatic toner and a carrier and for developing an electrostatic image with the chromatic toner, wherein a resistivity of the carrier in the chromatic developer is not less than 1.0×10 7 Ωcm and less than 1.0×10 9 Ωcm; a second developer supply device for supplying a chromatic supply developer including chromatic toner and a carrier into said second developing device, wherein a weight ratio of the carrier in the chromatic supply developer is lower than the weight ratio of the carrier in the black supply developer and is not less than 1 Wt % and not more than 15 Wt %; and second developer discharging means for discharging the developer from said second developing device.