Electric charging device, image forming apparatus, electric charging method, and manufacturing method of electric charging device

Abstract

A needle electrode having a pointed section is provided so as to face a charge-target object, and a voltage to be applied to the needle electrode is set so that 2≦(E·S)/(ES)≦5 is satisfied, where an ionization area Aindicates an area where ionization occurs to oxygen molecules in an atmosphere; a dissociation area Aindicates an area where dissociation occurs to the oxygen molecules in the atmosphere (excluding the ionization area A); Eindicates an average electric field strength in the ionization area A; Eindicates an average electric field strength in the dissociation area A; Sindicates square measure of the ionization area Aon a plane which includes a straight line connecting the needle electrode and the charge-target object so that a distance between the needle electrode and the charge-target object becomes a shortest distance; and Sindicates square measure of the dissociation area Aof the plane. Thus, the electric charging device is capable of carrying out charging which (i) excels in charging uniformity, (ii) reduces products such as ozone and nitrogen oxide and (iii) stably continues for a long stretch of time.