Electrophotographic image forming apparatus, process cartridge, and image forming method

A process cartridge comprising:

• a photosensitive drum;
• a charging roller for charging a surface of the photosensitive drum;
• and
• a developing means having toner and using the toner to develop an electrostatic latent image formed on the surface of the photosensitive drum, thereby forming a toner image, wherein
• a surface of the charging roller has a plurality of protrusions;
• when a group of protrusions having a height of 10.0 μm to 40.0 μm among the plurality of protrusions is taken as a group of first protrusions, and the number of vertices of the protrusions included in the group of first protrusions per unit area on the surface of the charging roller is denoted by Spd1, the Spd1 is 10/mm2 to 300/mm2;
• the number of vertices of the protrusions having a height exceeding 40.0 μm per unit area on the surface of the charging roller is not more than 3.0/mm2,
• the toner comprises a toner particle and titanium oxide fine particles;
• the titanium oxide fine particles comprise titanium oxide fine particles A that satisfy all of conditions (i) to (ii) below, and
• when the toner is observed using a scanning electron microscope, a proportion of the toner particle that can be confirmed to have, on the surface thereof, titanium oxide fine particles A is 80% by number to 99% by number:
• (i) The number-average value of major axis is 1.0 μm to 6.0 μm;
• (ii) The number-average value of aspect ratio is at least 5.0.

An image forming method comprising:

• a charging step of charging a surface of a photosensitive drum by using a charging roller;
• an exposure step of exposing charged photosensitive drum to form an electrostatic latent image on the photosensitive drum;
• a development step of using toner to develop the electrostatic latent image formed on the surface of the photosensitive drum, thereby forming a toner image;
• a transfer step of transferring the toner image to a transfer material, with or without an intermediate transfer member;
• and
• a fixing step of fixing the toner image on the transfer material, wherein
• a surface of the charging roller has a plurality of protrusions,
• when a group of protrusions having a height of 10.0 μm to 40.0 μm among the plurality of protrusions is taken as a group of first protrusions, and the number of vertices of the protrusions included in the group of first protrusions per unit area on the surface of the charging roller is denoted by Spd1, the Spd1 is 10/mm2 to 300/mm2,
• the number of vertices of the protrusions having a height exceeding 40.0 μm per unit area on the surface of the charging roller is not more than 3.0/mm2,
• the toner comprises a toner particle and titanium oxide fine particles;
• the titanium oxide fine particles comprise titanium oxide fine particles A that satisfy all of conditions (i) to (ii) below,
• when the toner is observed using a scanning electron microscope, a proportion of the toner particle that can be confirmed to have, on the surface thereof, titanium oxide fine particles A is 80% by number to 99% by number:
• (i) The number-average value of major axis is 1.0 μm to 6.0 μm;
• (ii) The number-average value of aspect ratio is at least 5.0.