Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

1. An electrophotographic photosensitive member, comprising:

an electroconductive support;

a photosensitive layer; and

a protection layer, the protection layer comprising niobium-containing titanium oxide electroconductive particles, wherein

a content of the electroconductive particles in the protection layer is 40 to 70 vol %, and

a volume resistivity of the protection layer is 1.0×10 9 to 1.0×10 14 Ω·cm.

2. The electrophotographic photosensitive member according to claim 1 , which has a charge retainability is 9.5 or more, wherein

charge retainability is determined by procedures 1 to 4:

procedure 1 applies a voltage to a surface of the electrophotographic photosensitive member from one direction while rotating the electrophotographic photosensitive member at a rotational speed of 30 rpm under an environment of a temperature of 23° C. and a humidity of 50% RH, the voltage being a rectangular wave voltage having a frequency of 1 Hz, a Voffset of −450 V, and a Vpp of 500 V,

procedure 2 measures a potential on the surface of the electrophotographic photosensitive member at a position at which a portion to which the voltage is applied to the surface of the electrophotographic photosensitive member is rotated for 0.30 seconds at a measurement interval of 100 μs for a predetermined time within the range from 10 to 20 seconds,

procedure 3 plots the values obtained by the measurement using μs as a unit of a horizontal axis and V as a unit of a vertical axis, and a slope of each of a regression line derived from previous 25 measurement points and a regression line derived from latter 25 measurement points is determined at each measurement point, and

procedure 4 calculates charge retainability by averaging absolute values of a maximum value and a minimum value of the obtained slopes.

3. The electrophotographic photosensitive member according to claim 1 , wherein the electroconductive particle is a particle containing anatase-type titanium oxide as a core material, and

titanium oxide containing niobium coating a surface of the core material.

4. The electrophotographic photosensitive member according to claim 1 , wherein a content of niobium in the electroconductive particles is 2.6 to 10.0% by mass.

5. The electrophotographic photosensitive member according to claim 1 , wherein the protection layer contains a polymerized product of a composition containing a radically polymerizable monomer.

6. A process cartridge integrally supporting an electrophotographic photosensitive member and at least one unit selected from the group consisting of a charging unit, a developing unit and a cleaning unit, and being detachably attachable to a main body of an electrophotographic apparatus, the electrophotographic photosensitive member comprising:

an electroconductive support;

a photosensitive layer; and

a protection layer, the protection layer comprising niobium-containing titanium oxide electroconductive particles, wherein

a content of the electroconductive particles in the protection layer is 40 to 70 vol %, and

a volume resistivity of the protection layer is 1.0×10 9 to 1.0×10 14 Ω·cm.

7. An electrophotographic apparatus, comprising:

an electrophotographic photosensitive member comprising an electroconductive support, a photosensitive layer, and a protection layer comprising niobium-containing titanium oxide electroconductive particles,

a charging unit;

an exposing unit;

a developing unit; and

a transfer unit, wherein

a content of the electroconductive particles in the protection layer is 40 to 70 vol %, and

a volume resistivity of the protection layer is 1.0×10 9 to 1.0×10 14 Ω·cm.