Process cartridge and electrophotographic apparatus

A process cartridge detachably attachable to a main body of an electrophotographic apparatus, the process cartridge comprising:

• an electrophotographic photosensitive member and a charging member,
• wherein the electrophotographic photosensitive member includes a support and a photosensitive layer,
• when average local potential differences of respective calculated lengths, the calculated lengths each are obtained by defining n as respective integers from 1 to 5,000, are determined based on the following calculation method by using a value obtained by charging an outer surface of the electrophotographic photosensitive member with −500 V, assuming that a straight line having a length of 5,000 μm is placed at an arbitrary position on the charged outer surface, and measuring potentials at measurement points located on the straight line at a pitch of 1 μm, a maximum value of the average local potential differences is 2 V or more,
• the charging member includes a support and an electro-conductive layer,
• the electro-conductive layer has a matrix and domains dispersed in the matrix,
• at least some domains are exposed to an outer surface of the charging member,
• the matrix contains a first rubber,
• the domain contains a second rubber and an electronic electro-conductive agent,
• a volume resistivity ρM of the matrix is at least 1.00×105 times a volume resistivity ρD of the domain, and
• when a calculated length in which a maximum value of the average local potential difference is obtained in the electrophotographic photosensitive member is defined as SCP [μm] and an arithmetic mean value of distances between wall surfaces of the domains observed on the outer surface of the charging member is defined as Dms [μm], SCP≥3×Dms,
• the calculation method comprising:
• i) dividing the straight line into calculated length n×1 μm (where, n is an integer of 1 or more) to obtain 5,000/n [number] regions;
• ii) calculating an average value of potentials, the potentials being obtained at all measurement points included in each region;
• iii) calculating a difference between regions adjacent to each other with respect to the average value of the potentials at each region calculated in ii) (local potential difference);
• and
• iv) calculating an average value of the local potential differences (average local potential difference) obtained between the regions.