A charging member that contacts an image bearing member and charges the image bearing member has an electrically conductive support and an elastic layer in contact with the image bearing member. The elastic layer includes a semiconductive rubber composition including a matrix and domains having electric conductivity. The semiconductive rubber composition has a sea-island structure in which the domains form an island phase and the matrix forms a sea phase. The matrix has a higher volume resistivity than the domains. The developer includes a toner, and the toner has a Martens hardness of at least 200 MPa and not more than 1100 MPa when measured under a maximum load of 2.010.sup.4 N.

Provided is a developing roller comprising an electroconductive substrate and an electroconductive layer thereon, the electroconductive layer retaining resin particles so that at least a part of each of the resin particles is exposed on an outer surface of the developing roller; the outer surface of the developing roller constituted by electrically insulating domains and an electroconductive matrix, assuming that a square region 200-m in a side is put on the outer surface of the developing roller, the square region including the domains, among the domains in the square region at least two of them satisfying specific condition, and assuming that the outer surface of the developing roller is charged, and creating a potential map of the charged outer surface of the developing member, the two domains satisfying the specific condition being ascertained in the potential map.

A developing roller having a rubber elastomer layer on the outer periphery of a shaft core metal, having a coating layer formed from a binder (A) and silicone rubber particles (B) on the surface of the rubber elastomer, and having an electrostatic capacitance of 4 to 20 nF; wherein the binder (A) is formed from a diluting solvent solution of a terminal hydroxyl group-containing prepolymer (a) obtained by reaction of an isocyanate compound, an isocyanurate modified product thereof and a reactive silicone oil, and an isocyanate compound and/or an isocyanurate modified product thereof (b). This developing roller suppresses banding by suppressing electrostatic capacitance even if the nip width between the developing roll and the photoreceptor changes due to distortion of peripheral members in the development apparatus, and stick slip (vibration) of gears.

Provided is a developing roller comprising an electroconductive substrate and an electroconductive layer thereon, the electroconductive layer retaining resin particles so that at least a part of each of the resin particles is exposed on an outer surface of the developing roller; the outer surface of the developing roller constituted by electrically insulating domains and an electroconductive matrix, assuming that a square region 200-m in a side is put on the outer surface of the developing roller, the square region including the domains, among the domains in the square region at least two of them satisfying specific condition, and assuming that the outer surface of the developing roller is charged, and creating a potential map of the charged outer surface of the developing member, the two domains satisfying the specific condition being ascertained in the potential map.

There is provided an electrophotographic member which suppresses scraping and contamination of a surface even in the durable use of multiple sheet printing under a high temperature environment. The electrophotographic member has an electroconductive substrate and a single elastic layer as a surface layer, the surface layer includes a binder resin and carbon black dispersed in the binder resin, the carbon black has a volatile content of 0.4% or more, the binder resin includes a crosslinked urethane resin and a crosslinked acrylic resin, and the surface layer has a first area in which the crosslinked urethane resin and the crosslinked acrylic resin form an interpenetrating polymer network structure, the first area being from an outer surface of the surface layer to a depth of 0.1 m in the surface layer.

Described herein is a liquid electrostatic ink developer assembly comprising a developer roller having a surface coating, the surface coating comprising a polyurethane resin formed from a polyol; a hydroxyl-terminated polysiloxane; and a polyisocyanate. Also, described herein is a liquid electrostatic printing apparatus comprising the liquid electrostatic ink developer assembly.

Provided is a development roll for electrophotography devices in which image defects are suppressed and which achieve both maintenance of high charging properties and discharging properties. The development roll is provided with a shaft member, an elastic substance layer formed on the outer circumference of the shaft member, an intermediate layer formed on the outer circumference of the elastic substance layer, and a surface layer formed on the outer circumference of the intermediate layer. The volume resistivity of the surface layer 18 is within the range of 1.010.sup.14 to 1.010.sup.20 .Math.cm, and the volume resistivity of the intermediate layer 16 is within the range of 1.010.sup.7 to 1.010.sup.13 .Math.cm.

There is provided an electrophotographic member which suppresses scraping and contamination of a surface even in the durable use of multiple sheet printing under a high temperature environment. The electrophotographic member has an electroconductive substrate and a single elastic layer as a surface layer, the surface layer includes a binder resin and carbon black dispersed in the binder resin, the carbon black has a volatile content of 0.4% or more, the binder resin includes a crosslinked urethane resin and a crosslinked acrylic resin, and the surface layer has a first area in which the crosslinked urethane resin and the crosslinked acrylic resin form an interpenetrating polymer network structure, the first area being from an outer surface of the surface layer to a depth of 0.1 m in the surface layer.

The present disclosure relates to a liquid electrophotographic ink developer unit. The unit comprises a developer roller, and a secondary roller that co-operates with the developer roller. The developer roller is formed of a material having a specific resistivity of less than 110.sup.6 .Math.cm. The secondary roller is formed of a material having a specific resistivity of 110.sup.4 to 110.sup.9 .Math.cm.

A charging member includes: an electrically conductive base; an elastic layer disposed on the electrically conductive base; and a surface layer disposed on the elastic layer. A PFVTF value of a surface of the surface layer is 1.5 or less. The PFVTF value is obtained by Fourier transforming a roughness curve of the surface of the surface layer that is measured in a circumferential direction to thereby obtain amplitude intensities at different periods, multiplying the amplitude intensities at different periods by VTF coefficients at respective periods that are obtained from a visual characteristic VTFL* (f=period) for lightness L* represented by Formula (V) below to thereby obtain corrected amplitude intensities at different periods, and integrating the corrected amplitude intensities in a period range of from 100 m to 1000 m inclusive:

VTFL*(f)=5.05(e.sup.(0.8431f)e.sup.(1.4541f))Formula (V):