Photoreceptor, process cartridge and image forming apparatus

1. A photoreceptor, comprising:

an electroconductive substrate;

a photosensitive layer overlying the electroconductive substrate; and

a protection layer overlying the photosensitive layer, wherein the protection layer comprises:

a crosslinked product of a radical polymerizable compound having three or more radical polymerizable groups without a charge transportable group and a compound having formula (1):

wherein p, q and r independently represent an integer of from 0 to 2; s and t independently represent an integer of from 0 to 3; R 1 represents a hydrogen atom or a methyl group; R 2 and R 3 independently represent an alkyl group having 1 to 5 carbon atoms wherein plural R 2 may be different from each other when s is 2 or 3 and R 3 may be different from each other when t is 2 or 3; and R 4 represents a single bond, a methylene group, an ethylene group, an ethyleneoxy group, a 2-methylethyleneoxy group or a phenyleneethylene group; and

a compound having formula (2):

wherein R 5 , R 7 and R 8 independently represent a hydrogen atom, an amino group, an alkoxy group, a thioalkoxy group, an aryloxy group, a methylenedioxy group, an alkyl group optionally having a substituent, a halo group or an aryl group optionally having a substituent; R 6 represents a hydrogen atom, an alkoxy group, an alkyl group optionally having a substituent or a halo group; k, l, m and n independently represent an integer of from 1 to 4wherein plural R 5 may be different from each other when k is an integer of from 2 to 4, plural R 6 may be different from each other when l is an integer of from 2 to 4, plural R 7 may be different from each other when m is an integer of from 2 to 4 and plural R 8 may be different from each other when n is an integer of from 2 to 4.

2. The photoreceptor of claim 1 , wherein a ratio of the total weight of the compound having the formula (1) and the compound having the formula (2) to the weight of the radical polymerizable compound is from 0.2 to 4.

3. The photoreceptor of claim 1 , wherein a weight ratio of the compound having the formula (2) to the compound having the formula (1) is from 0.2 to 4.

4. The photoreceptor of claim 1 , wherein the composition further comprises an inorganic particulate material and a particulate resin.

5. The photoreceptor of claim 1 , wherein the crosslinked product of the protection layer is formed by crosslinking via light or an electron beam.

6. A method of preparing a photoreceptor comprising an electroconductive substrate; a photosensitive layer overlying the electroconductive substrate; and a protection layer overlying the photosensitive layer, comprising:

coating a coating liquid on the photosensitive layer, comprising a composition comprising a radical polymerizable compound having three or more radical polymerizable groups without a charge transportable group, a compound having the following formula (1):

wherein p, q and r independently represent an integer of from 0 to 2; s and t independently represent an integer of from 0 to 3; R 1 represents a hydrogen atom or a methyl group; R 2 and R 3 independently represent an alkyl group having 1 to 5 carbon atoms wherein plural R 2 may be different from each other when s is 2 or 3 and R 3 may be different from each other when t is 2 or 3; and R 4 represents a single bond, a methylene group, an ethylene group, an ethyleneoxy group, a 2-methylethyleneoxy group or a phenyleneethylene group, and a compound having the following formula (2):

wherein R 5 , R 7 and R 8 independently represent a hydrogen atom, an amino group, an alkoxy group, a thioalkoxy group, an aryloxy group, a methylenedioxy group, an alkyl group optionally having a substituent, a halo group or an aryl group optionally having a substituent; R 6 represents a hydrogen atom, an alkoxy group, an alkyl group optionally having a substituent or a halo group; k, l, m and n independently represent an integer of from 1 to 4wherein plural R 5 may be different from each other when k is an integer of from 2 to 4, plural R 6 may be different from each other when l is an integer of from 2 to 4, plural R 7 may be different from each other when m is an integer of from 2 to 4 and plural R 8 may be different from each other when n is an integer of from 2 to 4; and

irradiating the coating liquid coated on the photosensitive layer with light or an electron beam such that the composition comprising the radical polymerizable compound, the compound having the formula (1) and the compound having the formula (2) are crosslinked to form the protection layer thereon.

7. An image forming apparatus, comprising:

the photoreceptor according to claim 1 ;

a charger configured to charge the photoreceptor;

an irradiator configured to irradiate the charged photoreceptor to form an electrostatic latent image thereon;

an image developer configured to develop the electrostatic latent image formed on the photoreceptor with a toner to form a toner image; and

a transferer configured to transfer the toner image formed on the photoreceptor to a recording medium.

8. A process cartridge detachable from image forming apparatus, comprising the photoreceptor according to claim 1 and one of a charger, an irradiator, an image developer, a transferer, a cleaner and a discharger.

9. The photoreceptor of claim 1 , wherein the compound of formula (1) is selected from the group consisting of formula (1-1), formula (1-2) and formula (1-3):

10. The photoreceptor of claim 1 , wherein the compound of formula (2) is selected from the group consisting of formula (2-1), formula (2-2) and formula (2-3):