Electrophotographic member with surface layer comprising tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and fixing device, and electrophotographic image forming apparatus including electrophotographic member
An electrophotographic member comprising a base layer, an elastic layer on an outer peripheral surface of the base layer, and a surface layer on an outer peripheral surface of the elastic layer, wherein the surface layer comprises a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, a plurality of crystals of the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having different circle-equivalent diameters is exposed on an outer surface of the surface layer, at least a part of an outer surface of the electrophotographic member is composed of a surface of the crystals and is roughened by the crystals, when an arithmetic-mean height Sa of each observation region in a specific region of the outer surface is determined, the electrophotographic member satisfies a specific relationship in a frequency distribution of the observation regions in which the arithmetic-mean height Sa is taken as a class and a class width is 0.05 μm.
1 . An electrophotographic member comprising a base layer, an elastic layer on an outer peripheral surface of the base layer, and a surface layer on an outer peripheral surface of the elastic layer, wherein
the surface layer comprises a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer,
a plurality of crystals of the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having different circle-equivalent diameters is exposed on an outer surface of the surface layer,
at least a part of an outer surface of the electrophotographic member is composed of a surface of the crystals and is roughened by the crystals,
when a rectangular region having a length of 5 mm in a direction along a circumferential direction of the electrophotographic member and a length of 10 mm in a longitudinal direction perpendicular to the circumferential direction is arranged on the outer surface of the electrophotographic member so that a center of the rectangular region in the longitudinal direction coincides with a center of the electrophotographic member in the longitudinal direction, the rectangular region is divided into 200 observation regions by squares with sides of 500 μm, and an arithmetic-mean height Sa of each observation region is determined,
in a frequency distribution of the observation regions in which the arithmetic-mean height Sa is taken as a class and a class width is 0.05 μm,
where the number of the observation regions comprised in an observation region group X1 belonging to a class where the arithmetic-mean height Sa is 0.10 to 0.40 μm is denoted by x1, x1 satisfies 160≤x1≤200, and
where the number of the observation regions comprised in an observation region group X2 belonging to a class where the arithmetic-mean height Sa is 0.10 to 0.20 μm is denoted by x2, and
the number of the observation regions comprised in an observation region group X3 belonging to a class where the arithmetic-mean height Sa is 0.25 to 0.40 μm is denoted by x3, x1 and x2 satisfy a following formula (1), and x1 and x3 satisfy a following formula (2):
0.25
·
x
1
≤
x
2
≤
0.75
·
x
1
(
1
)
0.25
·
x
1
≤
x
3
≤
0.75
·
x
1.
(
2
)
2 . The electrophotographic member according to claim 1 , wherein x1 and x2 satisfy a following formula (3), and x1 and x3 satisfy a following formula (4):
0.3
·
x
1
≤
x
2
≤
0.7
·
x
1
(
3
)
0.3
·
x
1
≤
x
3
≤
0.7
·
x
1.
(
4
)
3 . The electrophotographic member according to claim 1 , wherein an area-average diameter z2 of the crystals in at least one observation region among the observation regions comprised in the observation region group X2 is 10.0 to 25.0 μm.
4 . The electrophotographic member according to claim 1 , wherein an area-average diameter z3 of the crystals in at least one observation region among the observation regions comprised in the observation region group X3 is 35.0 to 60.0 μm.
5 . The electrophotographic member according to claim 1 , wherein, when an arithmetic-mean thickness of the surface layer in the 200 observation regions is determined, a difference Δt between a maximum value of the arithmetic-mean thickness and a minimum value of the arithmetic-mean thickness is 2.00 μm or less.
6 . The electrophotographic member according to claim 1 , wherein a thickness of the surface layer is 10 to 30 μm.
7 . The electrophotographic member according to claim 1 , wherein the electrophotographic member is an electrophotographic belt having an endless shape.
8 . The electrophotographic member according to claim 7 , wherein the electrophotographic member is a fixing belt.
9 . A fixing device in an electrophotographic image forming apparatus, wherein
the fixing device comprises a fixing member and a pressure member arranged opposite the fixing member, and
at least one of the fixing member and the pressure member is the electrophotographic member according to claim 1 .
10 . An electrophotographic image forming apparatus comprising a fixing device, wherein
the fixing device comprises a fixing member and a pressure member arranged opposite the fixing member, and
at least one of the fixing member and the pressure member is the electrophotographic member according to claim 1 .