Patent ID: 9651888
Date: 2017-05-16
CPC Classifications: G03G

Claim:
1. A charging member for electrophotography comprising: an electroconductive support bearing a surface layer comprising a porous body of a polymeric material, said porous body comprising a three-dimensionally continuous skeleton and a three-dimensionally continuous open pore, wherein a porosity of the porous body is 40 to 98%, and a specific surface area of the porous body is 0.5 to 100 μm the surface layer has a thickness of 1 μm to 200 μm, and has a volume resistivity of the surface layer is at least 1.0×10 the charging member satisfies the following (1) and (2): (1) a surface potential of the charging member is at least 10 V after an elapse of 10 seconds since a completion of a discharge for charging of the surface of the charging member, the charging of the surface of the charging member being conducted with a corona discharge unit which is disposed so that a grid portion of the corona discharge unit is apart from the surface of the charging member by 1 mm, by applying a voltage of 8 kV to the corona discharge unit and discharging therefrom, and (2) the charging member satisfies |Vd|≧|Vin|−|Vth|, |Vin|>|Vth| and |Vd|≧|Vin|−|Vth| when: (a) a polyethylene terephthalate sheet having a first surface which is aluminum-deposited and a second surface which is not aluminum is disposed so that the surface of the surface layer of the charging member is opposed to the second surface of the polyethylene terephthalate sheet at a clearance of 8 μm; (b) a negative voltage Vin is applied to the support and the first surface of the polyethylene terephthalate is grounded; (c) the charging member and the polyethylene terephthalate sheet are moved relatively at a speed of 10 mm/s without charging the clearance therebetween, and a region of 20 mm square or more of the second surface of the polyethylene terephthalate sheet is charged; (d) a discharge starting voltage Vth of the charging member is determined by increasing the negative voltage Vin from 0V; (e) a surface potential Vd of the second surface of the polyethylene terephthalate sheet is the average value obtained when the applied negative voltage Vin is equal to Vth−300V three times; and (f) a surface potential Vd of the second surface of the polyethylene terephthalate sheet is the average value obtained when the applied negative voltage Vin is equal to Vth−600V three times.