Developing device, process cartridge, and electrophotographic image forming apparatus

An electrophotographic process cartridge removably mountable onto a main body of an electrophotographic apparatus, the electrophotographic process cartridge comprising a developing device,

• wherein
• the developing device comprises a developer;
• and a developing member configured to carry the developer on a surface thereof,
• the developing member includes an electro-conductive substrate and a single-layer elastic layer serving as a surface layer on the substrate,
• the surface layer comprises a binder resin, and the binder resin contains a crosslinked urethane resin and a crosslinked acrylic resin,
• the crosslinked urethane resin and the crosslinked acrylic resin forms an interpenetrating polymer network structure in a first region from an outer surface of the surface layer to a position at a depth of 0.1 μm from the outer surface of the surface layer, and
• wherein
• the developer contains developer particles each containing at least a binder resin and a magnetic substance,
• the crosslinked urethane resin is a polycarbonate-modified urethane resin having, in its soft segment, a structure having a side-chain methyl group, and
• the binder resin incorporated into the surface layer (1) of the developing member has a volume resistivity of 1.0×1010 Ω·cm or more and 1.0×1018 Ω·cm or less.

An electrophotographic image forming apparatus comprising:

• an image-bearing member for bearing an electrostatic latent image;
• a charging device for primarily charging the image-bearing member;
• an exposing device for forming an electrostatic latent image on the image-bearing member that is primarily charged;
• a developing device for developing the electrostatic latent image with a developer to form a developer image;
• and
• a transferring device for transferring the developer image onto a transfer material,
• wherein
• the developing device comprises a developer;
• and a developing member configured to carry the developer on a surface thereof,
• the developing member includes an electro-conductive substrate and a single-layer elastic layer serving as a surface layer on the substrate,
• the surface layer comprises a binder resin, and the binder resin contains a crosslinked urethane resin and a crosslinked acrylic resin,
• the crosslinked urethane resin and the crosslinked acrylic resin forms an interpenetrating polymer network structure in a first region from an outer surface of the surface layer to a position at a depth of 0.1 μm from the outer surface of the surface layer, and wherein
• the developer contains developer particles each containing at least a binder resin and a magnetic substance,
• the crosslinked urethane resin is a polycarbonate-modified urethane resin having, in its soft segment, a structure having a side-chain methyl group, and
• the binder resin incorporated into the surface layer (1) of the developing member has a volume resistivity of 1.0×1010 Ω·cm or more and 1.0×1018 Ω·cm or less.

A developing device comprising:

• a developer;
• and
• a developing member configured to carry the developer on a surface thereof,
• the developing member including an electro-conductive substrate and a single-layer elastic layer serving as a surface layer on the substrate,
• the surface layer comprising a binder resin, and the binder resin containing a crosslinked urethane resin and a crosslinked acrylic resin,
• wherein a first region from an outer surface of the surface layer to a position at a depth of 0.1 μm from the outer surface of the surface layer contains both of the crosslinked urethane resin and the crosslinked acrylic resin,
• wherein when sampling a first sample from the first region and a peak top temperature of a thermal chromatogram derived from the crosslinked acrylic resin in the first sample is defined as A1(° C.), and
• when obtaining a second sample by decomposing the crosslinked urethane resin in the first sample, and a peak top temperature of a thermal chromatogram derived from the crosslinked acrylic resin in the second sample is defined as A2(° C.), A1 and A2 satisfy a relationship represented by formula (1):
• A1>A2, and Formula (1)
• wherein the developer contains developer particles each containing at least a binder resin and a magnetic substance,
• the crosslinked urethane resin is a polycarbonate-modified urethane resin having, in its soft segment, a structure having a side-chain methyl group, and
• the binder resin incorporated into the surface layer (1) of the developing member has a volume resistivity of 1.0×1010 Ω·cm or more and 1.0×1018 Ω·cm or less.