An electrophotographic roller includes: a mandrel and an elastic layer on the mandrel, and having a crown shape in which a diameter decreases from a central position O in a longitudinal direction of the mandrel toward an end portion. When a position of the end portion in the longitudinal direction of the elastic layer is defined as X2, a position between the ) and the X2 is defined as X1, a distance between the O and the X1 is defined as L1, and a distance between the X1 and the X2 is defined as L2, L1=0.6×(L1+L2). When outer diameters of the electrophotographic roller at O, X1 and X2 are defined as Do, DX1 and DX2, respectively, and Z1=(Do−DX1)/2 and Z2=(DX1−DX2)/2 are defined, Z1, Z2, L1 and L2 satisfy (Z2/L2)<1.931×(Z1/L1).

An image forming apparatus executes processing for calculating a complex number of a discharge current waveform which is a discharge current component of a current waveform in discharge based on a first complex number at an analyzing frequency near a charging frequency of a current waveform in non-discharge, a second complex number at the analyzing frequency of the current waveform in non-discharge, a third complex number at an analyzing frequency of the current waveform in discharge, and a fourth complex number at the analyzing frequency of the current waveform in discharge, and then for determining an AC voltage value of a charging voltage during image formation based on a calculation result of the complex number of the discharge current waveform. The controller controls a power supply portion to apply, to the charging member, the charging voltage including an AC voltage component with the determined value.

A cleaning body includes a core, a foam elastic layer that is disposed to be wound around an outer peripheral surface of the core in a helical shape from one end to the other end of the core, and an adhesive layer that adheres the core and the foam elastic layer, in which a diameter of a tip portion of a cell skeleton protruding on a surface of the foam elastic layer is equal to or less than 50 μm, and in a case where an inner peripheral length of the foam elastic layer in a cross section of the core in a radial direction is X (mm) and a thickness of the foam elastic layer is Y (mm), a value of X×Y.sup.2 is equal to or greater than 45.

An image forming apparatus detects a first current value and a second current value of currents flowing between an image bearing member and a developer carrying member. When a difference between the detected first current value and the detected second current value exceeds a threshold in a state in which the image bearing member and the developer carrying member are rotated and a first developing voltage is applied to the developer carrying member, a controller controls AC voltage applied to the developer carrying member.

A conductive roller includes a support member, an elastic layer disposed on an outer peripheral surface of the support member, and an outer layer disposed on an outer peripheral surface of the elastic layer. The elastic layer includes a cylindrical elastic foam and has a Young□s modulus of 150 kPa or less.

A conductive roll includes a support member, an elastic layer disposed on an outer peripheral surface of the support member, a surface layer disposed on an outer peripheral surface of the elastic layer, and an intermediate layer disposed between the elastic layer and the surface layer, the intermediate layer having a Poisson ratio of 0.40 or less.

An image forming apparatus includes a developing device that forms a toner image, by developing an electrostatic latent image formed on a photoconductor drum, a charging device that electrically charges the photoconductor drum, a developing power source that applies a predetermined developing bias voltage to the developing device, and a calculation device that calculates a surface potential of the photoconductor drum, on a basis of the developing current flowing in the developing device. The developing power source applies the developing bias voltage in a plurality of levels, to the developing device. A current measurement device measures a developing current, with respect to the developing bias voltage of each level. The calculation device calculates the surface potential, on the basis of each developing current.

Provided is an electrophotographic photosensitive member, which has high abrasion resistance and is resistant to being deeply flawed. Specifically, provided is an electrophotographic photosensitive member comprising a support and a surface layer formed on the support, wherein the surface layer comprises at least inorganic particles having pores in surfaces thereof, wherein at least a resin in the surface layer penetrates the pores, and wherein when vibration having a frequency of 0.5 Hz is applied to the surface layer at 28° C., the loss tangent tan δ of the dynamic viscoelasticity of the surface layer is from 0.005 to 0.05.

An electrophotographic photosensitive member includes: a support; an undercoat layer; a charge generation layer; and a charge transport layer, wherein the undercoat layer contains a polyamide resin and a titanium oxide fine particle, and on the surface of the undercoat layer, an arithmetic mean roughness Ra and an average length Rsm of a roughness curve element both according to JIS B0601:2001 satisfy Ra≤50 nm and 0.1≤Ra/Rsm≤0.5; and the charge generation layer contains a hydroxygallium phthalocyanine pigment, wherein the hydroxygallium phthalocyanine pigment includes crystal particles having a crystal form exhibiting peaks at 7.4°±0.3° and 28.2°±0.3° at Bragg angles 2θ in a spectrum of X-ray diffraction using a CuKα, ray; and in a size distribution of the crystal particles, which is measured using small-angle X-ray scattering, a peak exists in a range of 20 to 50 nm, and the peak has a half-value width of 50 nm or smaller.

Disclosed are an apparatus and method for forming a fine pattern. The apparatus for forming the fine pattern includes a lower electrode disposed on a bottom face of a fluid thin-film; an upper electrode positioned above the lower electrode, and spaced apart from the lower electrode by a first spacing, wherein a master pattern is formed on a bottom face of the upper electrode; and a power device configured to apply a high-voltage to between the lower electrode and the upper electrode, thereby generating an electric field therebetween.