Patent ID: 7570905

Claim:
A developing roller having an elastic layer on the outer periphery of a mandrel and having a surface layer containing a resin and resin particles on the outer periphery thereof, wherein the surface layer has a convex portion attributable to the resin particles, and has a surface of roughness in which a distortion degree Rsk of a roughness curve is 0.15 or more and 0.70 or less, wherein the resin particles have a peak P 1 at a particle diameter d 1 in a volume particle size distribution, and wherein “a”, “b”, “c”, d 1 , d 2 and d 3 satisfy the following relational formulas: 4 μm≦ d 2− d 1≦12 μm 6 μm≦d1≦22 μm 10 μm≦d2≦27 μm 2.0 Vol. %≦b ≦8.0 Vol. % 1.5 ≦a/b≦ 7.0 0.0 ≦c/b≦ 1.1, and d1<d3<d2 where, “a” denotes a volume fraction of the resin particle having the particle diameter d 1 in the volume particle size distribution, and “b” and “c” denote volume fractions at particle diameters d 2 and d 3 respectively in the volume particle size distribution, wherein, “A”, “t” and “B” satisfy the following formulas: 15≦A≦40 8.0≦t≦15.0 3.0 ≦A×B/ 100≦9.0, where, “A” denotes a blending quantity of the resin particle relative to the resin 100 parts by mass, “t” denotes the thickness of the surface layer in microns, and “B” denotes the volume fraction of the resin particle having a particle diameter not less than 1.2 times the thickness of the surface layer in the volume particle size distribution.