Image forming apparatus and process cartridge

1. An image forming apparatus comprising:

an electrophotographic photosensitive member; and

a developing device for supplying a toner onto the electrophotographic photosensitive member, the developing device having the toner, wherein

the electrophotographic photosensitive member has a surface layer comprising a binder resin (A),

the toner has a toner particle,

the toner particle has a core-shell structure having:

a core comprising a binder resin (B) and a wax; and

a shell layer formed on a surface of the core,

the binder resin (A) has:

a structure represented by a following formula (1); and

a structure represented by a following formula (2):

where, R 11 and R 21 each independently represent a hydrogen atom or a methyl group, R 22 and R 23 each independently represent a hydrogen atom, a methyl group, an ethyl group or a phenyl group, or R 22 and R 23 are linked to C between R 22 and R 23 shown in the formula (2) to form a cycloalkylidene group,

the wax comprises a monoester compound represented by a following formula (3):

R 31 —COO—R 32   (3)

where, R 31 and R 32 each independently represent an alkyl group having 10 to 30 carbon atoms.

2. The image forming apparatus according to claim 1 , wherein the toner has an average circularity of at least 0.960.

3. The image forming apparatus according to claim 1 , wherein

in a cross section of the toner observed using a transmission electron microscope, with the wax being observed as domains, when

a sum total of areas occupied by the domains in the entire cross section is defined as Wp,

a sum total of areas occupied by the domains in a region bounded by a contour of the cross section and a line that partitions a region 0.1 μm inward of the contour of the cross section is defined as Ws, and

a sum total of areas occupied by the domains in an internal region inward of the line that partitions a region 0.1 μm inward of the contour of the cross section is defined as Wc,

a ratio of the Ws to the Wp is 0.0 to 10.0%, and

a ratio of the Ws to the Wc is 0.00 to 0.50%.

4. The image forming apparatus according to claim 1 , wherein the toner contains the wax in an amount of 1.0 to 20.0% by mass.

5. The image forming apparatus according to claim 1 , wherein when a dispersion term and a polar term of Hansen solubility parameters in the binder resin (B) are defined as SD1 [(J/cm 3 ) 1/2 ] and SP1 [(J/cm 3 ) 1/2 ], respectively, and a dispersion term and a polar term of Hansen solubility parameters in the wax are defined as SD2 [(J/cm 3 ) 1/2 ] and SP2 [(J/cm 3 ) 1/2 ], respectively, following formulas (4) and (5) are satisfied:

0.00≤ SD 1− SD 2≤3.00  (4)

0.00≤ SP 1− SP 2≤0.30  (5).

6. The image forming apparatus according to claim 1 , wherein when a dispersion term and a polar term of Hansen solubility parameters in the wax are SD2 [(J/cm 3 ) 1/2 ] and SP2 [(J/cm 3 ) 1/2 ], respectively, and a dispersion term and a polar term of Hansen solubility parameters in the structure shown in the formula (2) are SD(A2) [(J/cm 3 ) 1/2 ] and SP(A2) [(J/cm 3 ) 1/2 ], respectively, following formulas (6) and (7) are satisfied:

2.50≤ SD ( A 2)− SD 2≤5.00  (6)

2.50≤ SP ( A 2)− SP 2≤6.00  (7).

7. The image forming apparatus according to claim 1 , wherein when a dispersion term and a polar term of Hansen solubility parameters in the wax are SD2 [(J/cm 3 ) 1/2 ] and SP2 [(J/cm 3 ) 1/2 ], respectively, and a dispersion term and a polar term of Hansen solubility parameters in the structure shown in the formula (1) are SD(A1) [(J/cm 3 ) 1/2 ] and SP(A1) [(J/cm 3 ) 1/2 ], respectively, following formulas (8) and (9) are satisfied:

2.50≤ SD ( A 1)− SD 2≤5.00  (8)

2.50≤ SP ( A 1)− SP 2≤6.00  (9).

8. The image forming apparatus according to claim 1 , wherein the shell layer of the toner particle comprises a vinyl resin comprising a monomer unit derived from methyl methacrylate.

9. The image forming apparatus according to claim 8 , wherein

in secondary ion depth profile measurement of the surface of the toner by time-of-flight secondary ion mass spectrometry,

when secondary ion intensities derived from the wax and the vinyl resin at a depth of t (nm) from the surface of the toner are defined as Iw(t) and Ib(t), respectively, following formulas (10) and (11) are satisfied in a range of 0≤t≤10:

Iw ( t )< Ib ( t )  (10)

Iw ( t )<0.005  (11).

10. The image forming apparatus according to claim 1 , wherein a value of a molar ratio of the structure represented by the formula (1) to the structure represented by the formula (2) [(the structure represented by the formula (1))/(the structure represented by the formula (2))] in the binder resin (A) is 25/75 to 70/30.

11. The image forming apparatus according to claim 1 , wherein the toner contains the wax in an amount of 7.0 to 13.0% by mass.

12. A process cartridge attached detachably to a main body of an image forming apparatus,

the process cartridge comprising:

an electrophotographic photosensitive member; and

a developing device for supplying a toner onto the electrophotographic photosensitive member, the developing device having the toner, wherein

the electrophotographic photosensitive member has a surface layer comprising a binder resin (A),

the toner has a toner particle;

the toner particle has a core-shell structure having:

a core comprising a binder resin (B) and a wax; and

a shell layer formed on a surface of the core,

the binder resin (A) has:

a structure represented by a following formula (1); and

a structure represented by a following formula (2):

where, R 11 and R 21 each independently represent a hydrogen atom or a methyl group, R 22 and R 23 each independently represent a hydrogen atom, a methyl group, an ethyl group or a phenyl group, or R 22 and R 23 are linked to C between R 22 and R 23 shown in the formula (2) to form a cycloalkylidene group, and

the wax comprises a monoester compound represented by a following formula (3):

R 31 —COO—R 32   (3)

where, R 31 and R 32 each independently represent an alkyl group having 10 to 30 carbon atoms.