Electrophotographic photoreceptor, process cartridge, and image forming apparatus

1. An electrophotographic photoreceptor, comprising:

a conductive substrate; and

a photosensitive layer provided on the conductive substrate,

wherein:

an uppermost surface layer of the electrophotographic photoreceptor is constituted with a cured film of a composition that contains:

at least two reactive charge transporting materials, wherein a first reactive charge transporting material has an —OH group as a reactive functional group and a second reactive charge transporting material has an —OCH 3 group as a reactive functional group,

fluororesin particles,

an alkyl fluoride group-containing copolymer having repeating units represented by the following Structural Formulae A and B, and

at least one compound selected from the group consisting of bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenyl)-methane and bis(4-diethylamino-2-methylphenyl)-phenylmethane,

a relative dielectric constant ∈r of the uppermost surface layer satisfies the following Formula (1):

3.5 ≦∈r≦ 4.0, and   Formula (1):

a charge amount Q of carrier traps of the uppermost surface layer satisfies the following Formula (2):

wherein in Structural Formulae A and B,

each of R 1 , R 2 , R 3 , and R 4 independently represents a hydrogen atom or an alkyl group;

X represents an alkylene chain, a halogen-substituted alkylene chain, —S—, —O—, —NH—, or a single bond;

Y represents an alkylene chain, a halogen-substituted alkylene chain, —(C z H 2z-1 (OH))—, or a single bond;

Q represents —O— or —NH—;

each of l, m, and n independently represents an integer of 1 or greater;

each of p, q, r, and s independently represents 0 or an integer of 1 or greater;

t represents an integer of from 1 to 7; and

z represents an integer of 1 or greater.

2. The electrophotographic photoreceptor according to claim 1 , wherein the relative dielectric constant ∈r of the uppermost surface layer satisfies the following Formula (1-2):

3.6 ≦∈r≦ 4.0.  Formula (1-2):

3. The electrophotographic photoreceptor according to claim 1 , wherein the relative dielectric constant ∈r of the uppermost surface layer satisfies the following Formula (1-3):

3.6 ≦∈r≦ 3.9.  Formula (1-3):

4. The electrophotographic photoreceptor according to claim 1 , wherein a ratio between a weight of the first reactive charge transporting material and a weight of the second reactive charge transporting material is from about 2 to about 20.

5. The electrophotographic photoreceptor according to claim 1 , wherein

the photosensitive layer includes a charge generating layer and a charge transporting layer in this order,

the uppermost surface layer is provided on the charge transporting layer, and

a difference between an ionization potential IP(OCL) of the uppermost surface layer and an ionization potential IP(CTL) of the charge transporting layer satisfies Formula (4):

IP ( OCL )− IP ( CTL )≦1.0.  Formula (4):

6. The electrophotographic photoreceptor according to claim 1 , wherein

the photosensitive layer includes the charge generating layer and the charge transporting layer in this order,

the uppermost surface layer is provided on the charge transporting layer, and

a difference between the ionization potential IP(OCL) of the uppermost surface layer and the ionization potential IP(CTL) of the charge transporting layer satisfies Formula (4-2):

IP ( OCL )− IP ( CTL )≦0.5.  Formula (4-2):

7. The electrophotographic photoreceptor according to claim 1 , wherein

the photosensitive layer includes the charge generating layer and the charge transporting layer in this order,

the uppermost surface layer is provided on the charge transporting layer, and

a difference between the ionization potential IP(OCL) of the uppermost surface layer and the ionization potential IP(CTL) of the charge transporting layer satisfies Formula (4-3):

IP ( OCL )− IP ( CTL )≦0.2.  Formula (4-3):

8. The electrophotographic photoreceptor according to claim 1 , wherein the at least two reactive charge transporting materials are compounds represented by Formula (I):

F—((—R 13 —X) n1 (R 14 ) n2 —Y) n3   (I)

wherein in Formula (I),

F represents a charge transporting skeleton and is an organic group derived from a compound with an ability to transport charge;

each of R 13 and R 14 independently represents a linear or branched alkylene group having from 1 to 5 carbon atoms;

n1 represents 0 or 1;

n2 represents 0 or 1;

n3 represents an integer of from 1 to 4;

X represents oxygen, NH, or a sulfur atom; and

Y represents an —OH group in the first reactive charge transporting material, and an —OCH 3 group in the second reactive charge transporting material.

9. The electrophotographic photoreceptor according to claim 8 , wherein the at least two reactive charge transporting materials are compounds represented by Formula (II):

wherein in Formula (II),

Ar 1 to Ar 4 may be the same as or different from each other;

each of Ar 1 to Ar 4 independently represents a substituted or unsubstituted aryl group;

Ar 5 represents a substituted or unsubstituted aryl group or a substituted or unsubstituted arylene group;

D represents —(—R 13 —X) n1 (R 14 ) n2 —Y;

each of c1 to c5 independently represents 0 or 1;

k represents 0 or 1;

a total number of D is from 1 to 4;

each of R 13 and R 14 independently represents a linear or branched alkylene group having from 1 to 5 carbon atoms;

n1 represents 0 or 1;

n2 represents 0 or 1;

X represents oxygen, NH, or a sulfur atom; and

Y represents an —OH group in the first reactive charge transporting material, and an —OCH 3 group in the second reactive charge transporting material.

10. An electrophotographic photoreceptor, comprising:

a conductive substrate; and

a photosensitive layer provided on the conductive substrate,

wherein:

an uppermost surface layer of the electrophotographic photoreceptor is constituted with a cured film of a composition that contains:

at least two reactive charge transporting materials, wherein a first reactive charge transporting material has an —OH group as a reactive functional group and a second reactive charge transporting material has an —OCH 3 group as a reactive functional group,

fluororesin particles,

an alkyl fluoride group-containing copolymer having repeating units represented by the following Structural Formulae A and B, and

at least one compound selected from the group consisting of bis(4-diethylamino-2-methylphenyl)-(4-diethylaminophenyl)-methane and bis(4-diethylamino-2-methylphenyl)-phenylmethane, and

a relative dielectric constant ∈r of the uppermost surface layer satisfies the following Formula (1):

wherein in Structural Formulae A and B,

each of R 1 , R 2 , R 3 , and R 4 independently represents a hydrogen atom or an alkyl group;

X represents an alkylene chain, a halogen-substituted alkylene chain, —S—, —O—, —NH—, or a single bond;

Y represents an alkylene chain, a halogen-substituted alkylene chain, —(C z H 2z-1 (OH))—, or a single bond;

Q represents —O— or —NH—;

each of l, m, and n independently represents an integer of 1 or greater;

each of p, q, r, and s independently represents 0 or an integer of 1 or greater;

t represents an integer of from 1 to 7; and

z represents an integer of 1 or greater.

11. A process cartridge detachable from an image forming apparatus, comprising the electrophotographic photoreceptor according to claim 1 .

12. An image forming apparatus comprising:

the electrophotographic photoreceptor according to claim 1 ;

a charging unit that charges the electrophotographic photoreceptor;

an electrostatic latent image forming unit that forms an electrostatic latent image on the charged electrophotographic photoreceptor;

a developing unit that accommodates a developer containing a toner and develops the electrostatic latent image formed on the electrophotographic photoreceptor into a toner image by using the developer; and

a transfer unit that transfers the toner image to a transfer medium.