US Patent 7610003 Image forming apparatus for recycling toner

In a tandem type color image forming apparatus having a function which collects a residual toner for recycle, a particle diameter distribution of a carrier is expressed as that a ratio of the number of carrier particles whose particle diameter is not smaller than φ40 μm is not greater than 5% and a ratio of the number of carrier particles whose particle diameter is not smaller than φ30 μm is not greater than 20%, or an intermediate transfer body which has a laminated structure including two or more layers and has a layer with the low hardness arranged on an image carrier, or a total toner layer thickness T1+T2+T3 of first to third transfer image is less than 30 μm.