Electrophotographic photosensitive member, process cartridge, and image forming apparatus

An electrophotographic photosensitive member comprising:

• a conductive substrate;
• and
• a photosensitive layer of a single layer, wherein
• the photosensitive layer contains a charge generating material, a hole transport material, an electron transport material, and a binder resin,
• an optical response time is 0.05 milliseconds or longer and 0.85 milliseconds or shorter,
• the optical response time is a time from irradiation of a surface of the photosensitive layer charged to +800 V with pulse light having a wavelength of 780 nm to decay of a surface potential of the photosensitive layer from +800 V to +400 V,
• the pulse light has an intensity that allows the surface potential of the photosensitive layer to decay to +200 V from +800 V after 400 milliseconds elapse from the irradiation of the surface of the photosensitive layer charged to +800 V with the pulse light,
• the photosensitive layer has a Martens hardness at 50° C. of at least 160 N/mm2, and
• the hole transport material includes a compound represented by chemical formula (19-HT17) shown below: