DEVELOPING DEVICE, PROCESS CARTRIDGE, AND IMAGE FORMING APPARATUS

A developing blade has a protrusion that protrudes toward a developing roller in an opposing portion facing the developing roller. When the potential difference between a supply bias and a developing bias is denoted by Δ(V), a contact pressure of the developing blade with respect to the developing roller is denoted by X (gf/cm), and a height of the protrusion from the opposing surface that faces the developing roller at a position further toward a tip side than the protrusion is denoted by H (mm) and a length of the opposing surface in the rotation direction of the developing roller is denoted by L (mm), when viewing a cross section perpendicular to the rotation axis of the developing roller, 0.05≦H≦0.1, 0.15≦L≦1.0, and 15≦X≦60 are established, and at least Δ≧−5*X−125 is satisfied.