Patent ID: 7885561

Claim:
An electric charging device comprising: at least one charging electrode to be provided in non-contact with a charge-target object; and voltage application means for applying a voltage to said at least one charging electrode, the electric charging device causing the charge-target object to be charged by ions generated when a voltage is applied to said at least one charging electrode, said at least one charging electrode having a pointed section provided so as to face the charge-target object; and the voltage to be applied to said at least one charging electrode is set so as to satisfy 2≦(E 2 ·S 2 )/(E 1 ·S 1 )≦5, where TH 1 indicates an ionization occurrence threshold value in MV/m which is a minimum value of an electric field strength causing oxygen molecules in an atmosphere to be ionized; TH 2 indicates a dissociation occurrence threshold value in MV/m which is a minimum value of an electric field strength causing oxygen molecules in the atmosphere to be dissociated; an ionization area A 1 indicates an area in which an electric field strength generated around the pointed section while a voltage is applied to said at least one charging electrode is not less than the ionization occurrence threshold value TH 1 ; a dissociation area A 2 indicates an area in which an electric field strength generated around the pointed section while a voltage is applied to said at least one charging electrode is not less than the dissociation occurrence threshold value TH 2 and less than the ionization occurrence threshold value TH 1 ; E 1 indicates an average electric field strength in MV/m in the ionization area A 1 ; E 2 indicates an average electric field strength in MV/m in the dissociation area A 2 ; S 1 in m 2 indicates cross section of the ionization area A 1 on a plane which includes a straight line connecting said at least one charging electrode and the charge-target object so that a distance between said at least one charging electrode and the charge-target object becomes a shortest distance; and S 2 in m 2 indicates cross section of the dissociation area A 2 of the plane.