Electroconductive member, process cartridge, and electrophotographic image forming apparatus
An electroconductive member for electrophotography including a support having electro-conductivity and an electroconductive layer on the outer surface of the support, the electroconductive layer including a matrix containing a crosslinked product of a first rubber and first electroconductive particles and domains each containing a crosslinked product of a second rubber and second electroconductive particles, wherein at least part of the first electroconductive particles are present as a primary particle in the crosslinked product of the first rubber, wherein, the first electroconductive particles of the matrix observed in a specific observation region have d1 of 200 nm or more, the second electroconductive particles in the domains observed therein have d2 of 50 nm or less, and 80 number % or more of the domains satisfy specific conditions.
1. An electroconductive member comprising:
a support having electro-conductivity; and
an electroconductive layer arranged on an outer surface of the support,
the electroconductive layer including:
a matrix containing:
a crosslinked product of a first rubber; and
first electroconductive particles; and
domains each containing:
a crosslinked product of a second rubber; and
second electroconductive particles,
at least a part of the first electroconductive particles being present as a primary particle in the crosslinked product of the first rubber, wherein
when defining a length of the electroconductive layer in a longitudinal direction as L and defining a thickness of the electroconductive layer as T, and when 15-micrometer square observation regions are put at arbitrary three positions in a thickness region from an outer surface of the electroconductive layer to a depth of 0.1 to 0.9T on each of cross-sections in a thickness direction of the electroconductive layer at three positions including a center of the electroconductive layer in the longitudinal direction and positions of L/4 from both ends of the electroconductive layer to the center,
an average primary particle diameter d1 of the first electroconductive particles present as a primary particle in the matrix observed in each of the nine observation regions in total is 200 nm or more, and
an average primary particle diameter d2 of the second electroconductive particles in the domains observed in each of the observation regions is 50 nm or less, and wherein
80 number % or more of the domains observed in each of the observation regions satisfy the following requirement (i) and requirement (ii)
requirement (i)
a ratio of cross-sectional areas of the second electroconductive particles included in a domain with respect to a cross-sectional area of the domain is 20% or more;
requirement (ii)
a circle-equivalent diameter of a domain is 4×d2 or more.
2. The electroconductive member according to claim 1 , wherein, among the first electroconductive particles, 90 number % or more of the first electroconductive particles are present as a primary particle in the matrix.
3. The electroconductive member according to claim 1 , wherein when a metal film is provided on an outer surface of the electroconductive member, and when an impedance A is measured by applying an AC voltage with an amplitude of 1V and a frequency of 1.0×10 −1 Hz between an outer surface of the support and the metal film under an environment having a temperature of 23° C. and a humidity of 50% RH, and an impedance B is measured by applying an AC voltage with an amplitude of 1V and a frequency of 1.0×10 −1 Hz and a DC voltage of 10 V between an outer surface of the support and the metal film under an environment having a temperature of 23° C. and a humidity of 50% RH, the impedance A and the impedance B satisfy the following relationship
Impedance A /impedance B≤ 60.
4. The electroconductive member according to claim 1 , wherein, when defining a length of the electroconductive layer in the longitudinal direction as L and defining a thickness of the electroconductive layer as T, and when 15-micrometer square observation regions are put at arbitrary three positions in a thickness region from an outer surface of the electroconductive layer to a depth of 0.1 to 0.9T on each of cross-sections in a thickness direction of the electroconductive layer at three positions including a center of the electroconductive layer in the longitudinal direction and positions of L/4 from both ends of the electroconductive layer to the center,
N(A) and N(B) satisfy the following relationship, where the N(A) represents a number of the first electroconductive particles observed in each of the nine observation regions in total and the N(B) represents a number of the domains observed therein:
0.2≤ N ( A )/ N ( B )≤3.0.
5. The electrophotographic member according to claim 4 , wherein N(A) and N(B) satisfy the following relationship:
0.35≤ N ( A )/ N ( B )≤0.70.
6. The electroconductive member according to claim 1 , wherein an arithmetic average value of distances between the first electroconductive particles and most proximate domains is 0.1 μm or more.
7. The electroconductive member according to claim 1 , wherein an arithmetic average value of distances between the domains is 0.2 μm or more and 2.0 μm or less.
8. The electroconductive member according to claim 1 , wherein the matrix has a volume resistivity of more than 1.0×10 8 Ω·cm and 1.0×10 17 Ω·cm or less.
9. The electroconductive member according to claim 1 , wherein, when a surface of the electroconductive member is charged with a corona discharger by setting a distance between a grid portion of the corona discharger and the surface of the electroconductive member to 1.0 mm and applying a voltage of 8 kV to the grid portion, and when a surface potential of the surface of the electroconductive member immediately after the charging is represented by E0 and a surface potential of the surface of the electroconductive member after a lapse of 10 seconds from completion of the charging is represented by E10, a charge attenuation ratio Q represented by the following equation is 83% or more.
Q
=
(
E
0
-
E
1
0
E
0
)
×
100
[
%
]
10. The electroconductive member according to claim 1 , wherein the first rubber is at least one selected from the group consisting of a natural rubber (NR), an isoprene rubber (IR), a butadiene rubber (BR), a styrene-butadiene rubber (SBR), a butyl rubber (IIR), an ethylene-propylene rubber (EPM), an ethylene-propylene-diene terpolymer rubber (EPDM), a chloroprene rubber (CR), an acrylonitrile-butadiene rubber (NBR), a hydrogenated product of NBR (H-NBR), an epichlorohydrin homopolymer, an epichlorohydrin-ethylene oxide copolymer, an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, and a silicone rubber.
11. The electrophotographic member according to claim 1 , wherein the second rubber is at least one selected from the group consisting of a natural rubber (NR); an isoprene rubber (IR); a butadiene rubber (BR); an acrylonitrile-butadiene rubber (NBR); a styrene-butadiene rubber (SBR); a butyl rubber (IIR); an ethylene-propylene rubber (EPM); an ethylene-propylene-diene rubber (EPDM); a chloroprene rubber (CR); a nitrile rubber (NBR); a hydrogenated nitrile rubber (H-NBR); a silicone rubber; and a urethane rubber (U).
12. The electrophotographic member according to claim 11 , wherein the carbon black has DBP absorption of less than 40 cm 3 /100 g.
13. The electroconductive member according to claim 1 , wherein difference of solubility parameter (SP value) between a rubber material for the domain and a rubber material for the matrix is 0.4 to 5.0 (J/cm 3 ) 0.5 .
14. The electroconductive member according to claim 1 , wherein the first rubber is SBR and the second rubber is NBR.
15. The electrophotographic member according to claim 13 , wherein the electroconductive carbon black has DBP absorption of 40 to 170 cm 3 /100 g.
16. The electroconductive member according to claim 1 , wherein the first rubber is NBR and the second rubber is SBR.
17. The electrophotographic member according to claim 1 , wherein the first electroconductive particles are at least one selected from the group consisting of carbon black and titanium oxide.
18. The electrophotographic member according to claim 1 , wherein the second electroconductive particles are electroconductive carbon black.
19. A process cartridge removably detachable to a main body of an electrophotographic image forming apparatus, the process cartridge comprising:
an electrophotographic photosensitive member; and
a charging member arranged to be able to charge the electrophotographic photosensitive member,
wherein the charging member is the electroconductive member comprising:
a support having electro-conductivity; and
an electroconductive layer arranged on an outer surface of the support,
the electroconductive layer including:
a matrix containing:
a crosslinked product of a first rubber; and
first electroconductive particles; and
domains each containing:
a crosslinked product of a second rubber; and
second electroconductive particles,
at least a part of the first electroconductive particles being present as a primary particle in the crosslinked product of the first rubber, wherein
when defining a length of the electroconductive layer in a longitudinal direction as L and defining a thickness of the electroconductive layer as T, and when 15-micrometer square observation regions are put at arbitrary three positions in a thickness region from an outer surface of the electroconductive layer to a depth of 0.1 to 0.9T on each of cross-sections in a thickness direction of the electroconductive layer at three positions including a center of the electroconductive layer in the longitudinal direction and positions of L/4 from both ends of the electroconductive layer to the center,
an average primary particle diameter d1 of the first electroconductive particles present as a primary particle in the matrix observed in each of the nine observation regions in total is 200 nm or more, and
an average primary particle diameter d2 of the second electroconductive particles in the domains observed in each of the observation regions is 50 nm or less, and wherein
80 number % or more of the domains observed in each of the observation regions satisfy the following requirement (i) and requirement (ii)
requirement (i)
a ratio of cross-sectional areas of the second electroconductive particles included in a domain with respect to a cross-sectional area of the domain is 20% or more;
requirement (ii)
a circle-equivalent diameter of a domain is 4×d2 or more.
20. An electrophotographic image forming apparatus comprising:
an electrophotographic photosensitive member; and
a charging roller arranged to be able to charge the electrophotographic photosensitive member,
wherein the charging roller is the electroconductive member comprising:
a support having electro-conductivity; and
an electroconductive layer arranged on an outer surface of the support,
the electroconductive layer including:
a matrix containing:
a crosslinked product of a first rubber; and
first electroconductive particles; and
domains each containing:
a crosslinked product of a second rubber; and
second electroconductive particles,
at least a part of the first electroconductive particles being present as a primary particle in the crosslinked product of the first rubber, wherein
when defining a length of the electroconductive layer in a longitudinal direction as L and defining a thickness of the electroconductive layer as T, and when 15-micrometer square observation regions are put at arbitrary three positions in a thickness region from an outer surface of the electroconductive layer to a depth of 0.1 to 0.9T on each of cross-sections in a thickness direction of the electroconductive layer at three positions including a center of the electroconductive layer in the longitudinal direction and positions of L/4 from both ends of the electroconductive layer to the center,
an average primary particle diameter d1 of the first electroconductive particles present as a primary particle in the matrix observed in each of the nine observation regions in total is 200 nm or more, and
an average primary particle diameter d2 of the second electroconductive particles in the domains observed in each of the observation regions is 50 nm or less, and wherein
80 number % or more of the domains observed in each of the observation regions satisfy the following requirement (i) and requirement (ii)
requirement (i)
a ratio of cross-sectional areas of the second electroconductive particles included in a domain with respect to a cross-sectional area of the domain is 20% or more;
requirement (ii)
a circle-equivalent diameter of a domain is 4×d2 or more.