Electrophotographic photoreceptor, process cartridge, and image forming apparatus

1. An electrophotographic photoreceptor comprising:

a conductive substrate;

an undercoat layer that is provided on the conductive substrate;

a charge generation layer that is provided on the undercoat layer;

a charge transport layer that is provided on the charge generation layer; and

a protective layer that is provided on the charge transport layer and has a volume resistivity of from 2×10 13 Ωm to 4×10 13 Ω·m,

wherein work functions and electron affinities of the undercoat layer and the charge generation layer satisfy the following Expression (1):

0.4 eV≦( Efuc−Eauc )−( Efcg−Eacg )≦0.6 eV

wherein Efuc represents the work function of the undercoat layer, Eauc represents the electron affinity of the undercoat layer, Efcg represents the work function of the charge generation layer, and Eacg represents the electron affinity of the charge generation layer.

2. The electrophotographic photoreceptor according to claim 1 ,

wherein the volume resistivity of the protective layer is from 3×10 13 Ω·m to 3.5×10 13 Ω·m.

3. The electrophotographic photoreceptor according to claim 1 ,

wherein in Expression (1), “(Efuc−Eauc)−(Efcg−Eacg)” is from 0.4 eV to 0.5 eV.

4. The electrophotographic photoreceptor according to claim 1 ,

wherein in Expression (1), “(Efuc−Eauc)−(Efcg−Eacg)” is from 0.42 eV to 0.45 eV.

5. The electrophotographic photoreceptor according to claim 1 ,

wherein the protective layer is formed of a cured film of a composition including at least a reactive charge transport material and an antioxidant.

6. The electrophotographic photoreceptor according to claim 5 ,

wherein the content of the antioxidant is from 1% by weight to 30% by weight with respect to all of the constituent components of the layer (solid content).

7. The electrophotographic photoreceptor according to claim 5 ,

wherein the content of the antioxidant is from 5% by weight to 20% by weight with respect to all of the constituent components of the layer (solid content).

8. The electrophotographic photoreceptor according to claim 5 ,

wherein the content of the antioxidant is from 8% by weight to 16% by weight with respect to all of the constituent components of the layer (solid content).

9. The electrophotographic photoreceptor according to claim 5 ,

wherein the undercoat layer includes at least a binder resin, metallic oxide particles, and an electron-accepting compound.

10. The electrophotographic photoreceptor according to claim 1 ,

wherein the undercoat layer includes at least a binder resin, metallic oxide particles, and an electron-accepting compound.

11. The electrophotographic photoreceptor according to claim 1 ,

wherein the undercoat layer includes at least a binder resin, metallic oxide particles, and an electron-accepting compound having an anthraquinone structure.

12. The electrophotographic photoreceptor according to claim 11 ,

wherein the content of the electron-accepting compound having an anthraquinone structure is from 1% by weight to 10% by weight with respect to all of the constituent components of the layer.

13. A process cartridge that is detachable from an image forming apparatus, the cartridge comprising:

the electrophotographic photoreceptor according to claim 1 .

14. An image forming apparatus comprising:

the electrophotographic photoreceptor according to claim 1 ;

a charging unit that charges the electrophotographic photoreceptor;

an electrostatic latent image forming unit that forms an electrostatic latent image on a charged electrophotographic photoreceptor;

a developing unit that stores a developer including a toner and develops the electrostatic latent image formed on the electrophotographic photoreceptor with the developer to form a toner image; and

a transfer unit that transfers the toner image onto a transfer medium.