| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing roller capable of securing electrified amount of toner and conveyed amount of toner within a desirable range even when performing printing for many sheets, and yielding a toner image having high density, made free from unevenness in a halftone density part and excelling in the reproducibility of a thin line. SOLUTION: The developing roller 25 is constituted by forming a covering layer 12 having conductivity on the outer periphery of a conductive shaft 11, and carries non-magnetic one-component developer on the surface of the covering layer 12 so as to form a thin layer 20 of the non-magnetic one-component developer. In such a state, the non-magnetic one-component developer is stuck to an electrostatic latent image on the surface of a latent image holding body, which holds the electrostatic latent image on its surface, from the thin layer of the non-magnetic one-component developer without bringing the developing roller 25 into contact with the latent image holding body, whereby the electrostatic latent image is made a visible image. In the developing roller 25, relation between the film thickness dr of the covering layer 12 and the film thickness dt of the thin layer 20 of the non-magnetic one-component developer is 0.5≤dr/dt≤1.5 and relation between a relative dielectric constantεr of the covering layer and a relative dielectric constantεt of the non-magnetic one-component developer isεt-1≤εr≤εt+4. COPYRIGHT: (C)2008,JPO&INPIT |
