Electrophotographic photoreceptor and image formation device

1. An electrophotographic photoreceptor comprising at least a photosensitive layer on a conductive substrate, wherein:

the photosensitive layer is a laminate having a charge transport layer and a charge generation layer,

the charge transport layer contains four or more types of compounds each having a maximum absorption wavelength falling within a wavelength range of from 300 nm to 500 nm in a 0.001 mass % tetrahydrofuran solution at 25° C., and

maximum absorption wavelengths falling within the wavelength range of at least four types of the compounds of said four or more types of the compounds are separated from each other by 10 nm or more, and

wherein at least one of said four or more types of the compounds is selected from the group consisting of compounds represented by the following formulas (4), (6), (10), (12), and (13):

2. The electrophotographic photoreceptor according to claim 1 , wherein the maximum absorption wavelengths falling within said wavelength range of at least four types of the compounds of said four or more types of the compounds are separated from each other by 20 nm or more.

3. The electrophotographic photoreceptor according to claim 1 , wherein said four or more types of the compounds contain at least a compound of which the maximum absorption wavelength falls within a wavelength range of from 300 to 350 nm and a compound of which the maximum absorption wavelength falls within a wavelength range of from 450 to 500 nm.

4. The electrophotographic photoreceptor according to claim 1 , wherein the charge transport layer contains a polyarylate resin or a polycarbonate resin.

5. The electrophotographic photoreceptor according to claim 1 , wherein the charge generation layer contains a phthalocyanine.

6. The electrophotographic photoreceptor according to claim 1 , wherein three or more types of said four or more types of the compounds are any three or more types of compounds represented by the following formula (I) to formula (VIII):

(In the formula (I), Ar 1 and Ar 2 each independently represent any of an aryl group, an alkoxy group or a hydrogen atom optionally having a substituent; and R 1 represents a substituent having from 12 to 30 carbon atoms)

(In the formula (II), Ar 3 and Ar 4 each independently represent an aryl group, an alkoxy group or a hydrogen atom optionally having a substituent; R 2 represents a substituent having from 18 to 70 carbon atoms; and y indicates an integer of from 1 to 3)

(In the formula (III), Ar 5 and Ar 6 each represent an arylene group; Ar 7 and Ar 8 each independently represent an aryl group or an alkoxy group optionally having a substituent; R 3 to R 5 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, or an aryl group optionally having a substituent)

(In the formula (IV), R 6 to R 9 each independently represents an alkyl group having 6 or less carbon atoms; and m indicates 0 or 1)

(In the formula (V), R 10 and R 11 each independently represent an alkyl group having 6 or less carbon atoms; and n indicates 0 or 1)

(In the formula (VI), R 12 and R 13 each independently represent an alkyl group having 6 or less carbon atoms; and Ar 9 represents an aryl group having 30 or less carbon atoms and optionally having a substituent)

(In the formula (VII), R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a phenyl group; and N indicates 0 or 1)

(In the formula R′ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a phenyl group).

7. The electrophotographic photoreceptor according to claim 1 , wherein the content of the compound, of which the content is the smallest of said four or more types of the compounds, is from 0.01 to 20 parts by mass relative to 100 parts by mass of the binder resin in the charge transport layer.

8. The electrophotographic photoreceptor according to claim 6 , wherein the content in the charge transport layer of each of the other compounds than the compound having the largest content of said four or more types of the compounds is from 0.01 to 20 parts by mass relative to 100 parts by mass of the binder resin in the charge transport layer.

9. The electrophotographic photoreceptor according to claim 6 , wherein the three or more types of said four or more types of the compounds are any three or more types of the compounds represented by the formula (IV), the formula (V) and the formula (VII).

10. An image formation device comprising the electrophotographic photoreceptor of claim 1 , a charging means of charging the electrophotographic photoreceptor, an exposure means of exposing the charged electrophotographic photoreceptor to light to form an electrostatic latent image, a development means of developing the electrostatic latent image with a toner, a transfer means of transferring the toner to a transferred medium, and a fixation means of fixing the toner transferred to the transferred medium.

11. An image formation device comprising the electrophotographic photoreceptor of claim 1 , a charging means of charging the electrophotographic photoreceptor, an exposure means of exposing the charged electrophotographic photoreceptor to light to form an electrostatic latent image, a development means of developing the electrostatic latent image with a toner, a transfer means of transferring the toner to a transferred medium, and a fixation means of fixing the toner transferred to the transferred medium, wherein a maximum exposure wavelength of the exposure light for use in the exposure means is from 650 nm to 900 nm.

12. The electrophotographic photoreceptor according to claim 1 , wherein three or more types of said four or more types of the compounds are any three or more types of compounds represented by the following formulas (III), (IV), (V), (VII), and (VIII):

(In the formula (III), A 5 and Ar 6 each represent an arylene group; Ar 7 and Ar 8 each independently represent an aryl group or an alkoxy group optionally having a substituent; R 3 to R 5 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, or an aryl group optionally having a substituent)

(In the formula (IV), R 6 to R 9 each independently represents an alkyl group having 6 or less carbon atoms; and m indicates 0 or 1)

(In the formula (V), R 10 and R 11 each independently represent an alkyl group having 6 or less carbon atoms; and n indicates 0 or 1)

(In the formula (VI), R 12 and R 13 each independently represent an alkyl group having 6 or less carbon atoms; and Ar 9 represents an aryl group having 30 or less carbon atoms and optionally having a substituent)

(In the formula (VII), R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a phenyl group; and N indicates 0 or 1)

(In the formula (VIII), R′ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, or a phenyl group).

13. The electrophotographic photoreceptor according to claim 1 , wherein at least two of said four or more types of the compounds are selected from the group consisting of compounds represented by the following formulas (6), (10), (12), (13) and (14):

14. The electrophotographic photoreceptor according to claim 1 , wherein at least three of said four or more types of the compounds are selected from the group consisting of compounds represented by the following formulas (6), (10), (12), (13) and (14):

15. The electrophotogaphic photoreceptor according to claim 1 , wherein at least four of said four or more types of the compounds are selected from the group consisting of compounds represented by the following formulas (6), (10), (12), (13) and (14):