Developing assembly, image-forming apparatus and process cartridge

An image-forming apparatus comprising (i) an electrostatic-latent-image-bearing member for holding thereon an electrostatic latent image and (ii) a developing assembly for developing the electrostatic latent image with a developer at a developing zone to form a developed image, wherein;

• said developing assembly comprises a developer container which holds therein a two-component developer comprised of a magnetic carrier and a non-magnetic toner, and a developer-carrying member;
• said magnetic carrier has a weight-average particle diameter of from 15 μm to 60 μm;
• said developer-carrying member has at least a substrate and a resin coat layer formed on the substrate surface;
• and
• said resin coat layer contains at least a binder resin and solid particles for forming unevenness on the resin coat layer surface;
• said solid particles satisfying an average circularity of 0.64 or more which is an average value of values calculated according to the following equation (1):
• Circularity=(4×A)/{(ML)2×Π} (1)
• wherein ML represents the Pythagorean-method maximum length of a particle projected image, and A represents a projected area of a particle image;
• and
• said resin coat layer fulfilling the following condition:
• S≧3.0
• where, in a surface profile of the resin coat layer measured using a laser of a confocal optical system, an average value of heights from the bottoms of dales to the vertexes of hills of the unevenness of the resin coat layer surface in the whole measurement region is regarded as a standard height, and a proportion of surface area occupied by parts of hills more than 0.1×r (r:
• weight-average particle diameter (μm) of the carrier used) higher than the standard height is represented by S (%);
• and further fulfilling the following conditions:
• Rp/Rv≧1.2, Rz/Rv≧2.0 and r/Rp≦6.0
• where a ten-point average roughness of the resin coat layer surface is represented by Rz (μm), an average-line depth by Rp (μm), and a average-line height by Rv (μm).

A process cartridge which is detachably mountable on the main body of an image-forming apparatus, which process cartridge integrally holds at least a developing assembly for developing an electrostatic latent image with a developer at a developing zone to form a developed image, wherein;

• said developing assembly comprises a developer container which holds therein a two-component developer comprised of a magnetic carrier and a non-magnetic toner, and a developer-carrying member;
• said magnetic carrier has a weight-average particle diameter of from 15 μm to 60 μm;
• said developer-carrying member has at least a substrate and a resin coat layer formed on the substrate surface;
• and
• said resin coat layer contains at least a binder resin and solid particles for forming unevenness on the resin coat layer surface;
• said solid particles satisfying an average circularity of 0.64 or more which is an average value of values calculated according to the following equation (1):
• Circularity=(4×A)/{(ML)2×Π} (1)
• wherein ML represents the Pythagorean-method maximum length of a particle projected image, and A represents a projected area of a particle image;
• and
• said resin coat layer fulfilling the following condition:
• S≧3.0
• where, in a surface profile of the resin coat layer measured using a laser of a confocal optical system, an average value of heights from the bottoms of dales to the vertexes of hills of the unevenness of the resin coat layer surface in the whole measurement region is regarded as a standard height, and a proportion of surface area occupied by parts of hills more than 0.1×r (r:
• weight-average particle diameter (μm) of the carrier used) higher than the standard height is represented by S (%);
• and further fulfilling the following conditions:
• Rp/Rv≧1.2, Rz/Rv≧2.0 and r/Rp≦6.0
• where a ten-point average roughness of the resin coat layer surface is represented by Hz (μm), an average-line depth by Rp (μm), and an average-line height by Rv (μm).