Developing apparatus using one-component toner

Abstract

An object of the present invention is to prevent an electrical breakdown of a toner layer and an occurrence of overcurrent, thereby preventing quality of image from being degraded at the time of development, when development with one-component toner is conducted using a developing roller of low resistance. The resistance value Rd of a developing roller which carries and conveys one-component toner in a manner of coming into contact with a photoconductor which bears an electrostatic latent image, is defined as Rd=.rho.d.multidot.(Dd1/S1), wherein S1 (cm.sup.2) is an area in which the developing roller comes into contact with the static image bearing member via a toner layer, Dd1 (cm) is a layer thickness of a semiconductive layer which composes the developing roller, and .rho.d (.OMEGA..multidot.cm) is a volume resistivity thereof. The range of the resistance Rd is set as 10.sup.4 <Rd<10.sup.5 and the resistance Rt (.OMEGA.) of the toner layer is set as Rt>5.times.10.sup.7. By using the developing roller of low resistance, excellent development is realized and an electrical breakdown and an overcurrent can be avoided by the resistance value of the toner layer.

Dependencies are inferred from the claim text.