Image-forming apparatus including an electrophotographic photoreceptor having an undercoat layer

1. An image-forming apparatus, comprising an electrophotographic photoreceptor, a charging unit, a light-exposure unit, a development unit, a transfer unit, and a controller that controls the traveling speed of the peripheral surface of the electrophotographic photoreceptor and thus makes a period from charging to development variable, wherein:

the electrophotographic photoreceptor comprises an undercoat layer and a photosensitive layer; and the undercoat layer contains metal oxide fine particles with an acceptor compound added on the metal oxide fine particles in a content of about 0.01% to about 20% by weight and wherein the metal oxide fine particles with the acceptor compound added thereon are dispersed in a resin; and an image is formed by charging, light exposure, development and transfer while causing the peripheral surface of the electrophotographic photoreceptor to travel in a predetermined direction, wherein:

the acceptor compound is one or more compounds selected from monohydroxyanthraquinone and aminohydroxyanthraquinone.

2. The image-forming apparatus of claim 1 , wherein the controller controls the traveling speed of the peripheral surface of the electrophotographic photoreceptor such that operation is switchable between a plurality of control modes including a normal mode, a low-speed mode and a high-speed mode.

3. The image-forming apparatus of claim 1 , wherein the metal oxide fine particles are surface-treated with a coupling agent before addition of the acceptor compound.

4. The image-forming apparatus of claim 1 , wherein the metal oxide fine particles contain one or more kinds selected from titanium oxide, zinc oxide, tin oxide, and zirconium oxide particles.

5. The image-forming apparatus of claim 1 , wherein the charging unit is a contact-type charging device that is brought into contact with the electrophotographic photoreceptor to charge the electrophotographic photoreceptor.

6. The image forming apparatus of claim 1 , wherein the undercoat layer further contains electron transport materials selected from a group consisting of quinone compounds; tetracyanoquinodimethane compounds; fluorenone; oxadiazole compounds; xanthone compounds; thiophene compounds; diphenoquinone compounds; electron transport pigments; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents.

7. The image-forming apparatus of claim 1 , wherein the metal oxide fine particles have a powder resistance of about 10 2 to about 10 11 Ωcm.

8. The image-forming apparatus of claim 1 , wherein the metal oxide fine particles have a specific surface area of 10 m 2 /g or more.

9. The image-forming apparatus of claim 1 , wherein the addition of the acceptor compound on the metal oxide fine particles is carried out by applying, on the metal oxide fine particles, a solution in which the acceptor compound is dissolved in an organic solvent.

10. An image-forming device, comprising a plurality of image forming units each having an electrophotographic photoreceptor, a charging unit, a light-exposure unit, and a development unit, a transfer unit, and a controller that controls the traveling speed of the peripheral surface of each of the electrophotographic photoreceptors and thus makes a period from charging to development variable, wherein:

the electrophotographic photoreceptor comprises an undercoat layer and a photosensitive layer; and the undercoat layer contains metal oxide fine particles with an acceptor compound added on the metal oxide fine particles in a content of about 0.01% to about 20% by weight and wherein the metal oxide fine particles with the acceptor compound added thereon are dispersed in a resin; and an image is formed by charging, light exposure, development and transfer while causing the peripheral surface of each of the electrophotographic photoreceptors to travel in a predetermined direction, wherein:

the acceptor compound is one or more compounds selected from monohydroxyanthraquinone and aminohydroxyanthraquinone.

11. The image-forming device of claim 10 , wherein the controller controls the traveling speed of the peripheral surface of each of the electrophotographic photoreceptors such that operation is switchable between a plurality of control modes including a normal mode, a low-speed mode and a high-speed mode.

12. The image-forming device of claim 10 , wherein the metal oxide fine particles are surface-treated with a coupling agent before addition of the acceptor compound.

13. The image-forming device of claim 10 , wherein the metal oxide fine particles contain one or more kinds selected from titanium oxide, zinc oxide, tin oxide, and zirconium oxide particles.

14. The image-forming device of claim 10 , wherein the charging unit is a contact-type charging device that is brought into contact with the electrophotographic photoreceptor to charge the electrophotographic photoreceptor.

15. The image-forming device of claim 14 , wherein the transfer unit has an intermediate transfer member and transfers toner images formed on the peripheral surfaces of the electrophotographic photoreceptors to the intermediate transfer member and then transfers the toner images from the intermediate transfer member to an image-receiving medium.

16. The image-forming device of claim 10 , wherein the metal oxide fine particles have a powder resistance of about 10 2 to about 10 11 Ωcm.

17. The image-forming device of claim 10 , wherein the metal oxide fine particles have a specific surface area of 10 m 2 /g or more.

18. The image-forming device of claim 10 , wherein the addition of the acceptor compound on the metal oxide fine particles is carried out by applying, on the metal oxide fine particles, a solution in which the acceptor compound is dissolved in an organic solvent.

19. A process cartridge that is detachable from an image-forming apparatus for forming an image by charging, light exposure, development and transfer while causing the peripheral surface of an electrophotographic photoreceptor to travel in a predetermined direction, the process cartridge comprising: an electrophotographic photoreceptor, a controller that controls the traveling speed of the peripheral surface of the electrophotographic photoreceptor and that thus makes a period from charging to development variable, and at least one selected from a charging unit, a development unit, a transfer unit and a cleaning unit, wherein:

the electrophotographic photoreceptor comprises an undercoat layer and a photosensitive layer; and the undercoat layer contains metal oxide fine particles with an acceptor compound added on the metal oxide fine particles in a content of about 0.0 1% to about 20% by weight and wherein the metal oxide fine particles with the acceptor compound added thereon are dispersed in a resin; wherein:

the acceptor compound is one or more compounds selected from monohydroxyanthraquinone and aminohydroxyanthraquinone.

20. The process cartridge of claim 19 , wherein the metal oxide fine particles have a powder resistance of about 10 2 to about 10 11 Ωcm.

21. The process cartridge of claim 19 , wherein the metal oxide fine particles have a specific surface area of 10 m 2 /g or more.

22. The process cartridge of claim 19 , wherein the addition of the acceptor compound on the metal oxide fine particles is carried out by applying, on the metal oxide fine particles, a solution in which the acceptor compound is dissolved in an organic solvent.