Electrophotographic photoreceptor, process cartridge, and image forming apparatus

1. An electrophotographic photoreceptor comprising:

a conductive substrate;

an organic photosensitive layer that is provided on the conductive substrate; and

an inorganic protective layer that is provided on the organic photosensitive layer so as to be in contact with a surface of the organic photosensitive layer,

wherein the organic photosensitive layer includes at least a charge generation layer and a charge transport layer, the charge transport layer including at least a charge transport material and silica particles in a region on the surface side in contact with the inorganic protective layer and arranged on the conductive substrate in this order,

wherein a weight content of the silica particles in the charge transport layer is greater than a weight content of the charge transport material,

wherein a content of the silica particles is from 30% by weight to 70% by weight with respect to the total weight of the charge transport layer, the weight of the charge transport material obtained by subtracting the weight of the silica particles from the weight of all the components of the charge transport layer, and

wherein a surface side of the charge transport layer is in direct contact with the inorganic protective layer, and a side of the charge transport material opposite the surface side is in direct contact with the charge generation layer.

2. The electrophotographic photoreceptor according to claim 1 ,

wherein a content of the charge transport material is from 40% by weight to 60% by weight with respect to a weight obtained by subtracting the weight of the silica particles from the weight of all the components of the charge transport layer.

3. The electrophotographic photoreceptor according to claim 1 ,

wherein a surface roughness Ra of a surface of the charge transport layer on the side of the inorganic protective layer is less than or equal to 0.06 μm.

4. The electrophotographic photoreceptor according to claim 1 ,

wherein an elastic modulus of the charge transport layer is greater than or equal to 5 GPa.

5. The electrophotographic photoreceptor according to claim 1 ,

wherein a volume average particle diameter of the silica particles is from 20 nm to 200 nm.

6. The electrophotographic photoreceptor according to claim 1 ,

wherein surfaces of the silica particles are treated with a hydrophobizing agent.

7. The electrophotographic photoreceptor according to claim 6 ,

wherein the hydrophobizing agent is a silane compound having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group.

8. The electrophotographic photoreceptor according to claim 6 ,

wherein a condensation ratio of the silica particles, of which the surfaces are treated with the hydrophobizing agent, is higher than or equal to 90%.

9. The electrophotographic photoreceptor according to claim 1 ,

wherein a thickness of the charge transport layer is from 10 μm to 40 μm.

10. The electrophotographic photoreceptor according to claim 1 ,

wherein a volume resistivity of the silica particles is greater than or equal to 10 11 Ω·cm.

11. A process cartridge, which is detachable from an image forming apparatus, comprising

the electrophotographic photoreceptor according to claim 1 .

12. An image forming apparatus comprising:

the electrophotographic photoreceptor according to claim 1 ;

a charging unit that charges a surface of the electrophotographic photoreceptor;

a latent image forming unit that forms a latent image on a charged surface of the electrophotographic photoreceptor;

a developing unit that develops the latent image, formed on the surface of the electrophotographic photoreceptor, using a toner to form a toner image; and

a transfer unit that transfers the toner image, formed on the surface of the electrophotographic photoreceptor, onto a recording medium.