The purpose of the present invention is to provide a developing roller which is not prone to scumming in a nonprinting area. The solution is to provide a developing roller which has an elastic layer, a coat layer formed on the elastic layer, and end portion coat layers formed on outermost surfaces on two axial end portions, wherein the end portion coat layer contains a conductive material.

Provided is a development roller which is capable of improving a black solid density and a 2-dot density simultaneously to form a satisfactory image with excellent contrast and thin line reproducibility. A development roller includes a roller body that contains a tubular inner layer consisting of an elastic material and an outer layer consisting of an elastic material, a roller resistance value R.sub.1 (, an applied voltage of 400 V) in a state when there is only the inner layer satisfies formula (1):
6.5log R.sub.19.5(1), and a volume resistivity R.sub.2 (.Math.cm, an applied voltage of 400 V) in a state when there is only the outer layer satisfies formula (2):
log R.sub.29.0(2).

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.

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.(?0.843?1?f)?e.sup.(?1.454?1?f)).Formula (V):

The present disclosure relates to an electroconductive roller for an electrophotographic printer. The roller comprises a polyurethane composition containing a polyurethane and an ionic liquid. The cation of the ionic liquid is an organic cation. The polyurethane composition has a specific resistivity of 110.sup.5 .Math.cm to 110.sup.8 .Math.cm.

The developing member includes a substrate, and an electroconductive layer on the substrate, wherein the electroconductive layer has electrically insulating domains on an outer surface thereof, the domains being independent from each other, the developing member has an outer surface including a surface of the electroconductive layer and surfaces of the domains, and wherein, when each of the domains is orthographically projected onto the surface of the electroconductive layer, defining respective areas of projected images of the domains as S, and defining respective areas of convex envelopes of the projected images as H, at least one domain satisfies the relation represented by 0.05S/H0.80.

Provided is a development roller which is capable of improving a black solid density and a 2-dot density simultaneously to form a satisfactory image with excellent contrast and thin line reproducibility. A development roller includes a roller body that contains a tubular inner layer consisting of an elastic material and an outer layer consisting of an elastic material, a roller resistance value R.sub.1 (, an applied voltage of 400 V) in a state when there is only the inner layer satisfies formula (1):

6.5log R.sub.19.5(1), and a volume resistivity R.sub.2 (.Math.cm, an applied voltage of 400 V) in a state when there is only the outer layer satisfies formula (2):

log R.sub.29.0(2).

The inventive developing roller (1) includes a roller body (2) having an outer peripheral surface (5) which includes a surface roughness component including a multiplicity of asperities and having a void volume Vv of not greater than 0.5 ml/m.sup.2, and a surface waviness component including a multiplicity of asperities having a longer periodicity than the surface roughness component and having a void volume Vv of not less than 0.05 ml/m.sup.2 and not greater than 3.5 ml/m.sup.2, the void volumes Vv being each defined as the sum Vvc+Vvv of a core void volume Vvc and a dale void volume Vvv. The inventive production method includes the steps of: polishing the outer peripheral surface (5); and finishing the polished outer peripheral surface by at least one method selected from the group consisting of a laser processing method, a wet blasting method and a dry blasting method, so that the outer peripheral surface has a surface geometry satisfying the requirements for the void volumes Vv.

A developing roller includes an electro-conductive shaft core and an elastic layer provided on an outer peripheral surface of the electro-conductive shaft core. The elastic layer includes a base layer formed of a rubber composition and an outermost layer formed on a surface of the base layer. The outermost layer is formed of a resin and is an incomplete film including a plurality of through-holes. A ratio of portions other than the through-holes of the outermost layer is 25% to 45% with respect to a total surface area of the elastic 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.