Patent ID: 7090956

Claim:
An image forming method comprising: in a center feed developing system comprising first and second developing rollers and a developing agent distributing member formed between said first and second developing rollers, and using a two-component developing agent consisting mainly of toners and magnetic carriers: controlling a stress applied to said developing agent between said first and second developing rollers and said developing agent distributing member, by selecting a shape coefficient SF 2 of toner particles in said toners to be within a predetermined range to restrict an occurrence of photographic fog; developing an electrostatic latent image formed on an image carrier into a toner image using said toners; transferring said toner image onto a recording medium; and fixing said toner image transferred onto said recording medium to thereby form a recorded image on a recording sheet; wherein said latent image is developed by said first and second developing rollers disposed along the moving direction of said image carrier and rotatable in the mutually opposite directions using said two-component developing agent consisting mainly of toners and magnetic carriers, and said toners are supplied to said latent image on said image carrier by said first and second developing rollers, wherein the moving direction of said first developing roller is opposite to the moving direction of said image carrier in a developing area, and a peripheral speed ratio (S 1 =Vm1/Vp) between the peripheral speed (Vm1) of said first developing roller and the peripheral speed (Vp) of said image carrier is set in the range of 0.8–2.0, wherein the moving direction of said second developing roller is the same as the moving direction of said image carrier in a developing area, and a peripheral speed ratio (S 2 =Vm2/Vp) between the peripheral speed (Vm2) of said second developing roller and the peripheral speed (Vp) of said image carrier is set in the range of 1.05–2.0, and wherein a plurality of shape coefficients SF 1 , SF 2 of said toners of said two-component developing agent consisting mainly of toners and magnetic carriers are respectively defined according to the following expressions (1) and (2), SF 1=(maximum length of diameter) 2 /(area of toner particle)×π/4×100 (1) SF 2=(peripheral length of projected image) 2 /(area of toner particle)×100/4π (2), said shape coefficients SF 1 , SF 2 respectively satisfying the following conditions: 120 ≦SF 1≦170 110 ≦SF 2≦130.