A charging roll includes a core member, a rubber base material disposed around the core member, and a surface layer disposed around the rubber base material. The ten point height of irregularities R.sub.Z of a surface of the surface layer is equal to or greater than 6.5 micrometers, and is equal to or less than 11.7 micrometers. The mean spacing between peaks S.sub.m of the surface of the surface layer is equal to or greater than 16.5 micrometers and is equal to or less than 18.8 micrometers.

Provided an electrophotographic electro-conductive member that can stably suppress an occurrence of fogging in an electrophotographic image. The member comprises a support having an electro-conductive outer surface, and an electro-conductive layer on the outer surface of the support, the electro-conductive layer having a matrix including a cross-linked product of a first rubber, and domains dispersed in the matrix, the domains each includes a cross-linked product of a second rubber and an electro-conductive particle, at least some of the domains is exposed to the outer surface of the electro-conductive member to constitute protrusions on an outer surface of the member, the outer surface of the electro-conductive member is constituted by the matrix and the domains exposed to the outer surface of the electrophotographic electro-conductive member, the electrophotographic electro-conductive member has an impedance of 1.0×10.sup.3Ω or more and 1.0×10.sup.8Ω or less, and some of the domains satisfy two specific requirements.

An electroconductive member for electrophotography has an electroconductive support and an electroconductive layer in the order mentioned. The electroconductive layer has a matrix including a crosslinked product of a first rubber, and a domain including a crosslinked product of a second rubber and an electroconductive particle. The impedance of an outer surface of the electroconductive member is 1.0×10.sup.3 to 1.0×10.sup.8Ω. 80% by number or more of domains observed at each of a total of nine 15-μm square observation regions, which are disposed at any three points in a thickness region from the outer surface to a specific depth on each of cross sections in a thickness direction at three points: the center of the electroconductive layer in the longitudinal direction and points at a specific distance from both edges of the electroconductive layer toward the center, satisfy specific requirements.

A development roller for an electrophotographic device that can both reduce resistance and suppress bleeding-out of an ion-conducting agent is provided. A development roller for an electrophotographic device 10 is provided with a shaft body 12, an elastic body layer 14 formed on the outer periphery of the shaft body 12, and a surface layer formed on the outer periphery of the elastic body layer 14. The surface layer 16 includes the following constituents (a) to (c), and the content of constituent (b) is 3.0 to 60 parts by mass, relative to 100 parts by mass of constituent (a). Constituent (a) is a binder comprising acrylonitrile-butadiene rubber, where the content of acrylonitrile is 31 mass % or more and 36 mass % or less. Constituent (b) is an ion-conducting agent. Constituent (c) is an acrylic polymer comprising at least one selected from among a silicone group and a fluorine group.

Provided an electrophotographic electro-conductive member that can stably suppress an occurrence of fogging in an electrophotographic image. The member comprises a support having an electro-conductive outer surface, and an electro-conductive layer on the outer surface of the support, the electro-conductive layer having a matrix including a cross-linked product of a first rubber, and domains dispersed in the matrix, the domains each includes a cross-linked product of a second rubber and an electro-conductive particle, at least some of the domains is exposed to the outer surface of the electro-conductive member to constitute protrusions on an outer surface of the member, the outer surface of the electro-conductive member is constituted by the matrix and the domains exposed to the outer surface of the electrophotographic electro-conductive member, the electrophotographic electro-conductive member has an impedance of 1.0×10.sup.3Ω or more and 1.0×10.sup.8Ω or less, and some of the domains satisfy two specific requirements.

An elastic body layer is composed of a conductive rubber composition containing an isoprene rubber, a rubber other than the isoprene rubber, and carbon black. The elastic body layer is phase-separated into a first rubber phase containing the isoprene rubber and a second rubber phase containing the rubber other than the isoprene rubber; in the range of a 5 μm×5 μm square of an arbitrary cross section of the elastic body layer, the area ratio of the first rubber phase is within a range of 10 to 90%. The resistance value of the elastic body layer is within a range of 1.0×10.sup.3 to 1.0×10.sup.6Ω. A surface layer contains an electronic conductive agent and a crosslinked body of at least one polyurethane resin of an ether polyurethane resin and a carbonate polyurethane resin, and the glass transition point of the surface layer is within a range of −10 to −70° C.

A charging member of a contact charging system that applies only a direct-current voltage to the charging member includes a conductive substrate, an elastic layer disposed on the conductive substrate, and a surface layer disposed on the elastic layer. When measured by an alternating-current impedance method within a range of 1 MHz to 1 mHz in an environment at a temperature of 28° C. and a humidity of 85%, a resistance component R of an impedance within a range of 1 Hz to 100 Hz is 4.0×10.sup.4 Ω or more and 1.0×10.sup.6 Ω or less and an impedance Z within a range of 1 Hz to 100 Hz is over 3.6×10.sup.4 Ω and 3.5×10.sup.5 Ω or less.

A conductive roller includes: a core member including an outer surface along and about an axial line thereof; and a surface layer arranged along the outer surface of the core member. The surface layer includes a conductive portion formed of a conductive resin composition, and a surface roughness imparting material in a form of particles dispersed in the conductive portion. An average particle size of the surface roughness imparting material is in a range of 6 micrometers or greater and 10 micrometers or less. The number of particles of the surface roughness imparting material per unit area of the surface layer is in a range of 1.0×10.sup.4 particles per mm.sup.2 or greater and 2.0×10.sup.6 particles per mm.sup.2 or less. An average thickness of the surface layer is in a range of 3.0 micrometers or greater and 15.0 micrometers or less.

In a charging roll, grooves regularly defining spirals are formed on an elastic body layer, with a groove width of 4 μm to 280 μm and a groove depth of 2 μm to 30 μm. On an outer peripheral surface of the elastic body layer, an area ratio between an area of a bottom surface of the groove and an area of a plane part is 0.3 to 2.4. The surface layer includes a binder polymer and a roughness forming particle. The roughness forming particle is arranged on the plane part and the groove. A surface roughness of the surface layer on the groove is 2 μm to 16 μm. A surface roughness of the entire surface layer is 5 μm to 26 μm. A thickness of the binder polymer covering the roughness forming particle on the groove is greater than that on the plane part.

A conductive roller includes a base including an outer surface along and about an axial line thereof, and a surface layer arranged on the outer surface of the base. The surface layer includes particles. The ten-point height of irregularities Rz of the outer surface of the base is greater than or equal to 6.0 micrometers and less than or equal to 8.0 micrometers. A ten-point height of irregularities Rz of an outer surface of the surface layer is greater than or equal to 5.5 micrometers and less than or equal to 8.5 micrometers. The base included in the conductive roller preferably includes a core member and a conductive elastic layer arranged between the core member and the surface layer. The surface layer preferably includes a conductive portion including a resin material and a conductive agent.