Image-forming apparatus including an electrophotographic photoreceptor having an undercoat layer with metal oxide particles and an acceptor compound

1. An image forming apparatus comprising an electrophotographic photoreceptor, a charging unit, an exposure unit, a development unit, and a transfer unit, wherein:

the image forming apparatus conducts charging, exposure, development, and transfer while moving a circumferential surface of the electrophotographic photoreceptor in a predetermined direction;

the image forming apparatus further comprises a controlling unit which controls a moving velocity of the circumferential surface of the electrophotographic photoreceptor so that a time required for processes from charging to development is changeable;

the electrophotographic photoreceptor includes an undercoat layer and a photosensitive layer; and

the undercoat layer has a thickness of 15 to 50 μm and includes a metal oxide particle and an acceptor compound having a hydroxyl group, wherein the acceptor compound having the hydroxyl group is selected from the group consisting of monohydroxyanthraquinone, trihydroxyanthraquinone and aminohydroxyanthraquinone;

wherein the acceptor compound is reacted with the metal oxide particle; and

wherein the metal oxide particle was subjected to a surface treatment with a coupling agent.

2. The image forming apparatus according to claim 1 , wherein the controlling unit can switch among a plurality of control modes including a normal mode, a low-speed mode, and a high-speed mode, which satisfy the conditions represented by the following formulae (1) and (2):

T low ≧(⅓) T   Formula (1):

T high ≦3T  Formula (2):

wherein in the formulae (1) and (2), T represents the time required for processes from charging to development in the normal mode; T low represents the time required for processes from charging to development in the low-speed mode; and T high represents the time required for processes from charging to development in the high-speed mode.

3. The image forming apparatus according to claim 1 , wherein the coupling agent is a silane coupling agent.

4. The image forming apparatus according to claim 1 , wherein the metal oxide particle includes a substance selected from titanium oxide, zinc oxide, tin oxide, and zirconium oxide.

5. The image forming apparatus according to claim 1 , wherein the charging unit is a contact charging unit which charge the electrophotographic photoreceptor by contacting the electrophotographic photoreceptor.

6. A color image forming apparatus comprising a plurality of image forming units each of which comprises an electrophotographic photoreceptor, a charging unit, an exposure unit, a development unit, and a transfer unit, wherein:

in each image forming unit, the image forming apparatus conducts charging, exposure, development, and transfer while moving a circumferential surface of the electrophotographic photoreceptor in a predetermined direction;

each image forming unit further comprises a controlling unit which controls a moving velocity of the circumferential surface of the electrophotographic photoreceptor so that a time required for processes from charging to development is changeable;

the electrophotographic photoreceptor includes an undercoat layer and a photosensitive layer; and

the undercoat layer has a thickness of 15 to 50 μm and includes a metal oxide particle and an acceptor compound having a hydroxyl group, wherein the acceptor compound having the hydroxyl group is selected from the group consisting of monohydroxyanthraquinone, trihydroxyanthraquinone and aminohydroxyanthraquinone;

wherein the acceptor compound is reacted with the metal oxide particle; and

wherein the metal oxide particle was subjected to a surface treatment with a coupling agent.

7. The color image forming apparatus according to claim 6 , wherein the controlling unit can switch among a plurality of control modes including a normal mode, a low-speed mode, and a high-speed mode, which satisfy the conditions represented by the following formulae (1) and (2):

T low ≧(⅓) T   Formula (1):

T high ≦3T  Formula (2):

wherein in the formulae (1) and (2), T represents the time required for processes from charging to development in the normal mode; T low represents the time required for processes from charging to development in the low-speed mode; and T high represents the time required for processes from charging to development in the high-speed mode.

8. The color image forming apparatus according to claim 6 , wherein the coupling agent is a silane coupling agent.

9. The color image forming apparatus according to claim 6 , wherein the metal oxide particle includes a substance selected from titanium oxide, zinc oxide, tin oxide, and zirconium oxide.

10. The color image forming apparatus according to claim 6 , wherein the charging unit is a contact charging unit which charges the electrophotographic photoreceptor by contacting the electrophotographic photoreceptor.

11. The color image forming apparatus according to claim 6 , wherein the transfer unit uses an intermediate transfer method in which a toner image formed on the circumferential surface of the electrophotographic photoreceptor is transferred indirectly to an image receiving medium via an intermediate transfer member.

12. A process cartridge comprising an electrophotographic photoreceptor and at least one selected from the group consisting of a charging unit, a development unit, a transfer unit, and a cleaning unit, wherein:

the process cartridge is attachable to an image forming apparatus and detachable from the image forming apparatus;

the image forming apparatus conducts charging, exposure, development, and transfer while moving a circumferential surface of the electrophotographic photoreceptor in a predetermined direction;

the process cartridge further comprises a controlling unit which controls a moving velocity of the circumferential surface of the electrophotographic photoreceptor so that a time required for processes from charging to development is changeable;

the electrophotographic photoreceptor includes an undercoat layer and a photosensitive layer;

the undercoat layer has a thickness of 15 to 50 μm and includes a metal oxide particle and an acceptor compound having a hydroxyl group, wherein the acceptor compound having the hydroxyl group is selected from the group consisting of monohydroxyanthraquinone, trihydroxyanthraquinone and aminohydroxyanthraquinone;

wherein the acceptor compound is reacted with the metal oxide particle; and

wherein the metal oxide particle was subjected to a surface treatment with a coupling agent.