Photoreceptor, method of manufacturing same, image formation method, image forming apparatus, and process cartridge

1. A photoreceptor comprising:

an electroconductive substrate;

a photosensitive layer located overlying the electroconductive substrate; and

a surface layer located overlying the photosensitive layer, the surface layer comprising a cross-linked material of a radical polymerizable monomer having at least 3 functional groups with no charge transport structure and a radical polymerizable compound having a charge transport structure, the surface layer having a sulfur concentration of 50 ppmw or lower.

2. The photoreceptor according to claim 1 , wherein the radical polymerizable monomer having at least 3 functional groups with no charge transport structure has a sulfur concentration of 50 ppmw or lower.

3. An image formation method comprising:

charging the photoreceptor of claim 1 ;

irradiating the photoreceptor to form a latent electrostatic image thereon;

developing the latent electrostatic image with a development agent to obtain a visualized image; and

furring the visualized image to a transfer medium.

4. An image forming apparatus comprising:

the photoreceptor of claim 1 ;

an irradiation device that irradiates the photoreceptor with light to form a latent electrostatic image thereon;

a development device that develops the latent electrostatic image with a development agent to obtain a visualized image; and

a transfer device that transfers the visualized image to a transfer medium.

5. A process cartridge detachably attachable to an image forming apparatus, comprising:

the photoreceptor of claim 1 ; and

at least one of a charging device, a development device, a transfer device, a discharging device and a cleaning device.

6. A method of manufacturing a photoreceptor, comprising:

refining a radical polymerizable monomer having at least 3 functional groups with no charge transport structure such that the radical polymerizable monomer having at least 3 functional groups with no charge transport structure has a sulfur concentration of 90 ppmw or less;

forming a photosensitive layer comprising a charge transport material overlying an electroconductive substrate; and

forming a surface layer overlying the photosensitive layer by applying a liquid application of the surface layer comprising the radical polymerizable monomer having at least 3 functional groups with no charge transport structure and a radical polymerizable compound having a charge transport structure, followed by curing and cross-linking upon application of an optical energy, whereby a sulfur concentration of the surface layer is 50 ppmw or less.

7. The method of manufacturing a photoreceptor according to claim 6 , wherein, in the step of refining, the radical polymerizable monomer having at least 3 functional groups with no charge transport structure is refined such that a ratio of a total number of colonies calculated according to a mutation test of Ames Test using salmonella of TA1535 to a number of colonies of a control solvent according thereto is 2.0 at maximum.

8. The method of manufacturing a photoreceptor according to claim 7 , wherein, in the step of refining, the radical polymerizable monomer having at least 3 functional groups with no charge transport structure is refined by separation refinement according to column chromatography.

9. The method of manufacturing a photoreceptor according to claim 6 , wherein, in the step of refining, the radical polymerizable monomer having at least 3 functional groups with no charge transport structure is refined by absorption refinement using an absorbent.

10. The method of manufacturing a photoreceptor according to claim 9 , wherein the absorbent in the step of refining is basic.