Electrophotographic electro-conductive member having a dual rubber elastic layer, method of producing the same, process cartridge, and electrophotographic apparatus
An electrophotographic electro-conductive member comprising an electro-conductive mandrel and an electro-conductive elastic layer on the electro-conductive mandrel, wherein the electro-conductive elastic layer has an elastic coefficient of 1 MPa or more and 100 MPa or less, as well as a matrix containing first rubber and a plurality of electro-conductive domains dispersed in the matrix. Each of the electro-conductive domains contains an electro-conductive particle, and the electro-conductive elastic layer includes regions containing second rubber in the circumferences of the electro-conductive domains. The matrix has an elastic coefficient R 1 , the regions containing second rubber have an elastic coefficient R 2 , and the elastic coefficients R 1 and R 2 satisfy a relationship: R 1 <R 2 .
1. An electrophotographic electro-conductive member comprising:
an electro-conductive mandrel; and
an electro-conductive elastic layer on the electro-conductive mandrel, wherein
the electro-conductive elastic layer has an elastic coefficient of 1 MPa or more and 100 MPa or less;
the electro-conductive elastic layer includes a matrix containing first rubber and a plurality of electro-conductive domains dispersed in the matrix;
each of the electro-conductive domains contains an electro-conductive particle;
the electro-conductive elastic layer includes regions containing second rubber in circumferences of the electro-conductive domains, the second rubber being a polymer gel derived from the first rubber; and
the matrix has an elastic coefficient R 1 , and the regions containing second rubber have an elastic coefficient R 2 , wherein the elastic coefficients R 1 and R 2 satisfy a relationship: R 1 <R 2 , wherein the elastic coefficients R1 and R2 are obtained from a mapping image of a measurement sample sampled from the electro-conductive elastic layer, the mapping image being obtained by measuring the measurement sample with a scanning probe microscope under condition of a spring constant of 0.315 N/m, an indentation load of 200 pN, a pixel number of 512×512, and a viewing field of 2.0×2.0 μm.
2. The electrophotographic electro-conductive member according to claim 1 , wherein the electro-conductive elastic layer has a hydrogen nuclear spin-spin relaxation time within a range of 200 μS or more and 500 μS or less at 50° C.
3. The electrophotographic electro-conductive member according to claim 1 , wherein the electro-conductive particle is carbon black.
4. The electrophotographic electro-conductive member according to claim 1 , wherein the first rubber contained in the electro-conductive elastic layer is nitrile butadiene rubber or styrene butadiene rubber.
5. A method of producing an electrophotographic electro-conductive member comprising an electro-conductive mandrel and an electro-conductive elastic layer on the electro-conductive mandrel, wherein
the electro-conductive elastic layer has an elastic coefficient of 1 MPa or more and 100 MPa or less;
the electro-conductive elastic layer includes a matrix containing first rubber and electro-conductive domains dispersed in the matrix;
each of the electro-conductive domains contains an electro-conductive particle;
the electro-conductive elastic layer includes regions containing second rubber in circumferences of the electro-conductive domains; and
the matrix has an elastic coefficient R 1 , and the regions containing second rubber have an elastic coefficient R 2 , wherein the elastic coefficients R 1 and R 2 satisfy a relationship: R 1 <R 2 , and
the method comprising:
(1) melting and kneading an electro-conductive elastic layer-forming rubber mixture containing first rubber or a raw material of the first rubber and an electro-conductive particle with a biaxial kneading extruder or a high shearing device equipped with a return screw, to obtain a rubber composition including
a matrix containing the first rubber or the raw material of the first rubber,
electro-conductive domains each of which contains an electro-conductive particles, and
regions in circumferences of the electro-conductive domains, the regions containing second rubber which is a polymer gel derived from the first rubber or the raw material of the first rubber;
(2) forming a layer of the rubber composition obtained in the step (1) on an electro-conductive mandrel; and
(3) curing the layer of the rubber composition to obtain the electrophotographic electro-conductive member.
6. The method according to claim 5 , wherein the rubber mixture is molten and kneaded with a biaxial kneading extruder, and the biaxial kneading extruder applies a shear velocity of 500 to 1500 sec −1 to the rubber mixture.
7. The method according to claim 5 , wherein the rubber mixture is molten and kneaded with a high shearing device equipped with a return screw, and the high shearing device equipped with a return screw applies a shear velocity of 500 to 10000 sec −1 to the rubber mixture.
8. The method according to claim 7 , wherein a shear velocity of 1000 to 10000 sec −1 is applied to the rubber mixture.
9. A process cartridge detachably attachable to a main body of an electrophotographic apparatus, comprising:
an electrophotographic photosensitive member; and
a charging member arranged so as to be capable of charging the electrophotographic photosensitive member, wherein
the charging member is an electrophotographic electro-conductive member;
the electrophotographic electro-conductive member includes an electro-conductive mandrel and an electro-conductive elastic layer on the electro-conductive mandrel;
the electro-conductive elastic layer has an elastic coefficient of 1 MPa or more and 100 MPa or less;
the electro-conductive elastic layer includes a matrix containing first rubber and a plurality of electro-conductive domains dispersed in the matrix;
each of the electro-conductive domains contains an electro-conductive particle;
the electro-conductive elastic layer includes regions containing second rubber in circumferences of the electro-conductive domains, the second rubber being a polymer gel derived from the first rubber; and
the matrix has an elastic coefficient R 1 , and the regions containing second rubber have an elastic coefficient R 2 , wherein the elastic coefficients R 1 and R 2 satisfy a relationship: R 1 <R 2 , wherein the elastic coefficients R1 and R2 are obtained from a mapping image of a measurement sample sampled from the electro-conductive elastic layer, the mapping image being obtained by measuring the measurement sample with a scanning probe microscope under condition of a spring constant of 0.315 N/m, an indentation load of 200 pN, a pixel number of 512×512, and a viewing field of 2.0×2.0 μm.
10. An electrophotographic apparatus comprising an electrophotographic electro-conductive member, wherein
the electrophotographic electro-conductive member includes an electro-conductive mandrel and an electro-conductive elastic layer on the electro-conductive mandrel;
the electro-conductive elastic layer has an elastic coefficient of 1 MPa or more and 100 MPa or less;
the electro-conductive elastic layer includes a matrix containing first rubber and a plurality of electro-conductive domains dispersed in the matrix;
each of the electro-conductive domains contains an electro-conductive particle;
the electro-conductive elastic layer includes regions containing second rubber in circumferences of the electro-conductive domains, the second rubber being a polymer gel derived from the first rubber; and
the matrix has an elastic coefficient R 1 , and the regions containing second rubber have an elastic coefficient R 2 , wherein the elastic coefficients R 1 and R 2 satisfy a relationship: R 1 <R 2 , wherein the elastic coefficients R1 and R2 are obtained from a mapping image of a measurement sample sampled from the electro-conductive elastic layer, the mapping image being obtained by measuring the measurement sample with a scanning probe microscope under condition of a spring constant of 0.315 N/m, an indentation load of 200 pN, a pixel number of 512×512, and a viewing field of 2.0×2.0 μm.