Electrophotographic photoreceptor, process cartridge, and image forming apparatus

1. An electrophotographic photoreceptor comprising:

a conductive substrate;

an undercoat layer provided on the conductive substrate and including metal oxide particles; and

a photosensitive layer provided on the undercoat layer,

wherein, at the time of performing Cole-Cole plot analysis with respect to the undercoat layer, an angular frequency ωmax, at which a maximum complex impedance component is obtained, falls within a range of 4 (rad)≦ωmax≦7.5 (rad),

wherein the metal oxide particles are zinc oxide particles consisting of two portions, a first portion of the zinc oxide particles having a first diameter, and a second portion of the zinc oxide particles having a second diameter larger than that of the first diameter, and

wherein a weight ratio r (%) of the first portion of zinc oxide particles in the undercoat layer is from 49% to 78% by weight with respect to the zinc oxide particles.

2. The electrophotographic photoreceptor according to claim 1 ,

wherein powder resistance of the metal oxide particles falls within a range of 10 2 Ωcm to 10 11 Ωcm.

3. The electrophotographic photoreceptor according to claim 1 ,

wherein the undercoat layer contains a binder resin, and a content of the metal oxide particles is from 10% by weight to 80% by weight with respect to the binder resin.

4. The electrophotographic photoreceptor according to claim 1 ,

wherein the undercoat layer contains a binder resin, and a content of the metal oxide particles is from 40% by weight to 80% by weight with respect to the binder resin.

5. The electrophotographic photoreceptor according to claim 1 ,

wherein the undercoat layer contains a compound having an anthraquinone structure that has a hydroxyl group.

6. The electrophotographic photoreceptor according to claim 1 ,

wherein the undercoat layer contains a compound having an anthraquinone structure that has a hydroxyl group and an alkoxy group.

7. A process cartridge that comprises the electrophotographic photoreceptor according to claim 1 , and is detachable from an image forming apparatus.

8. An image forming apparatus, comprising:

the electrophotographic photoreceptor according to claim 1 ;

a contact charging type charging unit charging a surface of the electrophotographic photoreceptor;

an electrostatic latent image forming unit forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

a developing unit developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor by using a developer including a toner to form a toner image; and

a transfer unit transferring the toner image onto a surface of a recording medium.