Developing roller, process cartridge and electrophotographic image forming apparatus

A process cartridge detachably mounted on a main body of an electrophotographic apparatus, comprising a developing roller,

• the developing roller comprising:
• an electro-conductive substrate;
• an electro-conductive elastic layer on the electro-conductive substrate;
• and
• a surface layer on the electro-conductive elastic layer,
• the surface layer comprising a matrix and resin particles dispersed in the matrix, the matrix containing polyurethane as a binder, the resin particles including a first resin particle and a second resin particle,
• the matrix has an elastic modulus Eb of 10 to 100 MPa, the elastic modulus being measured at a region in a cross section in a thickness direction of the surface layer, the region being a depth of 1.0 μm or more from an outer surface of the surface layer,
• the outer surface of the surface layer is constituted by
• a first protrusion, and
• a second protrusion existing in an area which is free from the first protrusion, the second protrusion has a height lower than a height of the first protrusion by 5.0 μm or more,
• the first protrusion being formed by the first resin particle, and the second protrusion being formed by the second resin particle,
• the first resin particle comprising polyurethane, and having an elastic modulus E1 of 100 to 2000 MPa, when measured in a cross section in a thickness direction of the surface layer, the second resin particle having an elastic modulus E2 of 2 to 50 MPa, when measured in a cross section in the thickness direction of the surface layer,
• the outer surface of the developing roller having a maximum height roughness of 6 to 18 μm, and having a peak vertex density Spd of 5.0×103 (1/mm2) to 5.0×104 (1/mm2).

An electrophotographic image forming apparatus comprising:

• a photosensitive member;
• and a developing roller for supplying a developer to an electrostatic latent image formed on the photosensitive member,
• the developing roller comprising:
• an electro-conductive substrate;
• an electro-conductive elastic layer on the electro-conductive substrate;
• and
• a surface layer on the electro-conductive elastic layer,
• the surface layer comprising a matrix and resin particles dispersed in the matrix, the matrix containing polyurethane as a binder, the resin particles including a first resin particle and a second resin particle,
• the matrix has an elastic modulus Eb of 10 to 100 MPa, the elastic modulus being measured at a region in a cross section in a thickness direction of the surface layer, the region being a depth of 1.0 μm or more from an outer surface of the surface layer,
• the outer surface of the surface layer is constituted by
• a first protrusion, and
• a second protrusion existing in an area which is free from the first protrusion, the second protrusion has a height lower than a height of the first protrusion by 5.0 μm or more,
• the first protrusion being formed by the first resin particle, and the second protrusion being formed by the second resin particle,
• the first resin particle comprising polyurethane, and having an elastic modulus E1 of 100 to 2000 MPa, when measured in a cross section in a thickness direction of the surface layer, the second resin particle having an elastic modulus E2 of 2 to 50 MPa, when measured in a cross section in the thickness direction of the surface layer,
• the outer surface of the developing roller having a maximum height roughness of 6 to 18 μm, and having a peak vertex density Spd of 5.0×103 (1/mm2) to 5.0×104 (1/mm2).