Electrophotographic photoreceptor, and process cartridge and image forming apparatus using the same

1. An electrophotographic photoreceptor comprising:

an electroconductive substrate;

a photosensitive layer arranged on or above the electroconductive substrate; and

a surface layer arranged on or above the photosensitive layer, and containing about 90% or more by atom of gallium (Ga), oxygen (O) and hydrogen (H), and having an atomic number density of about 7.8×10 22 cm −3 or more in the layer.

2. The electrophotographic photoreceptor according to claim 1 , wherein the atomic number density is from about 7.8×10 22 cm −3 to about 10.4×10 22 cm −3 .

3. The electrophotographic photoreceptor according to claim 1 , wherein the film thickness of the surface layer is from about 1.5μm to 10.0μm.

4. The electrophotographic photoreceptor according to claim 1 , wherein the element composition ratio of oxygen to gallium (oxygen/gallium) is from about 1.1 to about 1.5.

5. The electrophotographic photoreceptor according to claim 1 , wherein the total proportion of oxygen, gallium and hydrogen is about 95% or more by atom and the element composition ratio of oxygen to gallium (oxygen/gallium) is from about 1.1 to about 1.4.

6. The electrophotographic photoreceptor according to claim 1 , wherein the photosensitive layer is an organic photosensitive layer.

7. A process cartridge comprising, as a unit:

an electrophotographic photoreceptor comprising:

an electroconductive substrate;

a photosensitive layer arranged on or above the electroconductive substrate; and

a surface layer arranged on or above the photosensitive layer, and containing about 90% or more by atom of gallium (Ga), oxygen (O) and hydrogen (H), and having an atomic number density of about 7.8×10 22 cm −3 or more; and

at least one selected from the group consisting of an charging unit for charging the electrophotographic photoreceptor, a developing unit for developing an electrostatic latent image formed on the electrophotographic photoreceptor charged by the charging unit with a developing agent containing a toner, and a cleaning unit for removing an adherent substance adhered to the electrophotographic photoreceptor.

8. The process cartridge according to claim 7 , wherein the atomic number density is from about 7.8×10 22 cm −3 to about 10.4×10 22 cm −3 .

9. The process cartridge according to claim 7 , wherein the film thickness of the surface layer is from about 1.5μm to 10.0μm.

10. The process cartridge according to claim 7 , wherein the element composition ratio of oxygen to gallium (oxygen/gallium) is from about 1.1 to about 1.5.

11. The process cartridge according to claim 7 , wherein the total proportion of oxygen, gallium and hydrogen is about 95% or more by atom and the element composition ratio of oxygen to gallium (oxygen/gallium) is from about 1.1 to about 1.4.

12. The process cartridge according to claim 7 , wherein the photosensitive layer is an organic photosensitive layer.

13. An image forming apparatus comprising:

an electrophotographic photoreceptor comprising:

an electroconductive substrate;

a photosensitive layer arranged on or above the electroconductive substrate; and

a surface layer arranged on or above the photosensitive layer, and containing about 90% or more by atom of gallium (Ga), oxygen (O) and hydrogen (H), and having an atomic number density of about 7.8×10 22 cm −3 or more;

an charging unit for charging the electrophotographic photoreceptor;

an electrostatic latent image forming unit for forming an electrostatic latent image on the electrophotographic photoreceptor charged by the charging unit;

a developing unit for developing the electrostatic latent image into a toner image with a developing agent containing a toner; and

a transferring unit for transferring the toner image onto a recording medium.

14. The image forming apparatus according to claim 13 , wherein the atomic number density is from about 7.8×10 22 cm −3 to about 10.4×10 22 cm −3 .

15. The image forming apparatus according to claim 13 , wherein the film thickness of the surface layer is from about 1.5μm to 10.0μm.

16. The image forming apparatus according to claim 13 , wherein the element composition ratio of oxygen to gallium (oxygen/gallium) is from about 1.1 to about 1.5.

17. The image forming apparatus according to claim 13 , wherein the total proportion of oxygen, gallium and hydrogen is about 95% or more by atom and the element composition ratio of oxygen to gallium (oxygen/gallium) is from about 1.1 to about 1.4.

18. The image forming apparatus according to claim 13 , wherein the photosensitive layer is an organic photosensitive layer.