Patent ID: 6537714
Filing Date: 2003-03-25
Classification: G03G

Abstract:
An image-forming method used in an image-forming apparatus comprising:four image-forming units making use of a first toner, a second toner, a third toner and a fourth toner which have colors different from one another, for forming toner images on a transfer medium; and a heat-and-pressure fixing means for performing heat-and-pressure treatment on the transfer medium having the toner images thereon; said four image-forming units each having; a photosensitive member having an amorphous silicon or non-single-crystal silicon layer; a charging means for charging the photosensitive member electrostatically; an exposure means for exposing the photosensitive member to form an electrostatic latent image thereon: and a developing means having a developing sleeve for developing the electrostatic latent image formed on the photosensitive member; said photosensitive member having a diameter of from 20 mm to 80 mm; after charging said photosensitive member with the charging means, the electrostatic latent image being formed by exposure with the exposure means, and, at a development position in unexposed areas, said photosensitive member being made to have a surface potential of from 300 V to 450 V as an absolute value; said developing means having a two-component developer containing the toner and a carrier; said photosensitive member and said developing sleeve being so disposed as to have a minimum gap between them of from 350 &mgr;m to 800 &mgr;m; while the developing sleeve rotates at a peripheral speed from 1.1 times to 4.0 times the peripheral speed of the photosensitive member, the electrostatic latent image being developed with a magnetic brush of the two-component developer to form a toner image on the photosensitive member; said first toner, second toner, third toner and fourth toner being selected from the group consisting of a non-magnetic yellow toner, a non-magnetic magenta toner, a non-magnetic cyan toner and a non-magnetic black toner; said non-magnetic yellow toner, non-magnetic magenta toner, non-magnetic cyan toner and non-magnetic black toner having negative chargeability and each having a weight-average particle diameter of from 4.0 &mgr;m to 10.0 &mgr;m; the carrier of said two-component developer having a 50% average particle diameter of from 10 &mgr;m to 80 &mgr;m; and where a coloring power of the toner of each color is defined as image density D0.5 measured after being fixed once when a quantity of unfixed toner on a transfer medium, M/S, is 0.5 mg/cm2 and the coloring power of the non-magnetic yellow toner is represented by D0.5Y, the coloring power of the non-magnetic magenta toner by D0.5M, the coloring power of the non-magnetic cyan toner by D0.5C and the coloring power of the nonmagnetic black toner by DO.5Bk, each of D0.5Y, D0.5M, D0.5C and D0.5Bk being from 1.0 to 1.8 as image density, and, where the coloring power of the toner showing the maximum coloring power among the three colors of yellow, magenta and cyan is represented by D0.5max, and the coloring power of the toner showing the minimum coloring power by D0.5min, a difference between D0.5max and D0.5min being 0.5 or less.