A developing roller that enables the image density of electrophotographic images to be kept uniform even when used in an environment at a high temperature and a high humidity for a long period. The developing roller includes an electro-conductive mandrel and an electro-conductive layer on the mandrel, having an outer surface constituted by at least a first region which is electrically insulating, and a second region, the second region having higher electro-conductivity than that of the first region, the first region being arranged adjacent to the second region, the first region being disposed on an outer surface of the electro-conductive layer, the first region having a Vickers hardness of 10.0 or more as measured at an outer surface thereof, and the first region having a fracture toughness value of 800 Pa.Math.m.sup.0.5 or more as measured at the outer surface thereof by an indentation fracture method.

A developer bearing member including: a rotational shaft; and an elastic layer on an outer circumference surface of the rotational shaft, developer being borne on a surface of the elastic layer, wherein the elastic layer is configured such that a load per unit area of a contact portion between one surface of a flat glass plate and the surface of the elastic layer is to be 5.8 N/mm.sup.2 or more, in a state that the one surface of the flat glass plate being parallel with an axis direction of the rotational shaft and the one surface of the flat glass plate coming into contact with the surface of the elastic layer with a predetermined penetration level, and wherein a ten-point average roughness Rzjis on the surface of the elastic layer is greater than a volume-average particle diameter of a particle of the developer.

A conductive roller includes a supporting member and a conductive elastic foam layer disposed on the supporting member. In a spectrum of amplitude (m) vs. period (m) obtained by subjecting a roughness waveform of the outer circumferential surface of the conductive elastic foam layer in an axial direction to fast Fourier transformation, the integrated value St of the amplitude within a period range of 100 m or more and 300 m or less is 455 m or less.

There is provided a developing device including, when viewed in a section perpendicular to a rotational axis of a rotatable developing member, a recessed portion to grip a resin-made regulating blade formed on an upstream side of the regulating blade with respect to a closest position where the regulating blade comes closest to the rotatable developing member in a rotation direction of the rotatable developing member, and a vertical length of the recessed portion in a direction vertical to a straight line passing through the closest position and a rotation center of the rotatable developing member is 0.5 mm or more.

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.

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.

There are provided a developing roller having no risks of the image density of formed images rapidly decreasing and the occurrence of an uneven density since a toner transportation amount does not decrease greatly even if image formation is repeated, and a method of producing the same. In a developing roller, a plurality of recesses are disposed on an outer circumferential surface of a roller main body so that a ratio P.sub.A/P.sub.C of a pitch P.sub.A in an axial direction on the outer circumferential surface to a pitch P.sub.C in a circumferential direction is set to a range exceeding 1.1. The production method includes a process of forming the recesses on the outer circumferential surface by laser processing.

The developing member has an electroconductive substrate, and an elastic layer having a mono-layer structure on the substrate as a surface layer, wherein the elastic layer has a thickness of T m and a volume resistivity of 1.010.sup.5 .Math.cm to 1.010.sup.12 .Math.cm, and includes a first resin as a main binder; and the elastic layer further includes a second resin having a structural unit represented by Formula (1), in a region extending toward a first surface from a second surface by a depth of t m, where the first surface is defined as a surface of the elastic layer on a side facing the substrate, and the second surface is defined as a surface thereof opposite to the first surface, wherein in the region, a concentration of ether bonds is higher on the second surface side than on the first surface side (provided that T>t):

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There is provided a developing device including, when viewed in a section perpendicular to a rotational axis of a rotatable developing member, a recessed portion to grip a resin-made regulating blade formed on an upstream side of the regulating blade with respect to a closest position where the regulating blade comes closest to the rotatable developing member in a rotation direction of the rotatable developing member, and a vertical length of the recessed portion in a direction vertical to a straight line passing through the closest position and a rotation center of the rotatable developing member is 0.5 mm or more.

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.