Color image forming method

Claim 1

A color image forming method in which a superimposed image is formed on a surface of a photoreceptor body by sequential superposition of plural kinds of toner in a predetermined order from a first kind of toner to a last kind of toner, each kind of toner having a different color from each other kind of toner and being used in a development of a toner image by means of a thin layer, non-contact inversion development technique, the method comprising the steps of: (1) selecting a kind of toner for development in accordance with the predetermined order, the selected kind of toner being recognized as the n-th kind of toner; (2) charging the selected kind of toner with an electrostatic charge; (3) charging the surface of the photoreceptor body to a uniform electric potential; (4) forming an electrostatic latent image on the surface of the photoreceptor body corresponding to the selected kind of toner; (5) developing the electrostatic latent image using the selected kind of toner to form a toner image using the selected kind of toner; (6) repeating the steps (1) to (4) for a subsequent kind of toner recognized as a (N+1)th kind of toner until the last kind of toner of the predetermined order has been selected and developed under a condition that the following formulas are satisfied: 15micro C/g=<(Q/M)n=<30 micro C/g, 1.1=<(Q/M)n/(Q/M)n+1=<1.5, and (developing efficiency)n+1<(developing efficiency)n, wherein (Q/M)n is defined as an amount of electrostatic charge per unit mass of the n-th kind of toner charged for the development, (Q/M)n+1 is defined as an amount of electrostatic charge per unit mass of the (n+1)th kind of toner subsequently charged for the development, (developing efficiency)n is an amount of n-th kind of toner developed per unit area in a solid image divided by an amount of n-th kind of toner supplied from a corresponding developing unit, and (developing efficiency)n+1 is an amount of (n+1)th kind of toner developed per unit area in a solid image divided by an amount of (n+1)th kind of toner supplied from a corresponding developing unit; and (7) transferring the toner image superimposed on the surface of the photoreceptor body to a copy sheet.