Contact transfer device and image forming equipment

Abstract

An image forming apparatus includes an image carrier, a transfer member contactable to the image carrier for transferring toner to a recording member and a bias source connected to the transfer member. The toner includes resin particles and external additives added thereto. The transfer member satisfies the following relationship, R.gtoreq.0.350+(0.001H) where R represents the aerated bulk density of the toner and H represents the hardness (JISA) of the transfer member. Also, the transfer member satisfies 4.gtoreq.W.gtoreq.16.0-3.52.times.R+0.2.times.R.sup.2, where R represents the logarithmic value of the resistance of the transfer member and W (wt %) represents the amount of external additives added to the resin particles of the toner. In addition, where the resistance of the transfer member is expressed as R(.OMEGA.) and a current value of the transfer bias is expressed as It (.mu.A), the following relationship is satisfied: 1.32.times.10.sup.-4 LV.sub.p .ltoreq. It.ltoreq.2.66.times.10.sup.-3 (log(R)-3.15) LV.sub.p /d and It.ltoreq.1.29.times.10.sup.-2 LV.sub.p /d, where L (mm) is the longitudinal length of the contact surface between the transfer member and image carrier, V.sub.p (mm/s) represents the process speed and d (.mu.m) represents the thickness of the photosensitive layer on the image carrier.