Process cartridge and electrophotographic apparatus
There is provided a process cartridge detachably attachable to a main body of an electrophotographic apparatus, the process cartridge including: an electrophotographic photosensitive member and a charging member, in which when average local potential differences of calculated lengths in the electrophotographic photosensitive member is calculated based on a specific method, a maximum value of the average local potential difference is 2 V or more, the charging member includes a support and an electro-conductive layer, the electro-conductive layer has a matrix and domains dispersed in the matrix, a volume resistivity ρM of the matrix is at least 1.00×10 5 times a volume resistivity ρD of the domain, and a specific calculated length S CP [μm] and a specific value relating a distance between the domains D ms [μm] satisfy S CP ≥3×D ms .
1. A process cartridge detachably attachable to a main body of an electrophotographic apparatus, the process cartridge comprising: an electrophotographic photosensitive member and a charging member,
wherein the electrophotographic photosensitive member includes a support and a photosensitive layer,
when average local potential differences of respective calculated lengths, the calculated lengths each are obtained by defining n as respective integers from 1 to 5,000, are determined based on the following calculation method by using a value obtained by charging an outer surface of the electrophotographic photosensitive member with −500 V, assuming that a straight line having a length of 5,000 μm is placed at an arbitrary position on the charged outer surface, and measuring potentials at measurement points located on the straight line at a pitch of 1 μm, a maximum value of the average local potential differences is 2 V or more,
the charging member includes a support and an electro-conductive layer,
the electro-conductive layer has a matrix and domains dispersed in the matrix,
at least some domains are exposed to an outer surface of the charging member,
the matrix contains a first rubber,
the domain contains a second rubber and an electronic electro-conductive agent,
a volume resistivity ρM of the matrix is at least 1.00×10 5 times a volume resistivity ρD of the domain, and
when a calculated length in which a maximum value of the average local potential difference is obtained in the electrophotographic photosensitive member is defined as S CP [μm] and an arithmetic mean value of distances between wall surfaces of the domains observed on the outer surface of the charging member is defined as D ms [μm], S CP ≥3×D ms ,
the calculation method comprising:
i) dividing the straight line into calculated length n×1 μm (where, n is an integer of 1 or more) to obtain 5,000/n [number] regions;
ii) calculating an average value of potentials, the potentials being obtained at all measurement points included in each region;
iii) calculating a difference between regions adjacent to each other with respect to the average value of the potentials at each region calculated in ii) (local potential difference); and
iv) calculating an average value of the local potential differences (average local potential difference) obtained between the regions.
2. The process cartridge according to claim 1 , wherein S CP ≥10×D ms .
3. The process cartridge according to claim 1 , wherein the maximum value of the average local potential difference is 8 V or more.
4. The process cartridge according to claim 1 , wherein S CP is in a range of 10 μm to 100 μm.
5. The process cartridge according to claim 1 , wherein D ms is 0.2 μm or more and 5.0 μm or less.
6. The process cartridge according to claim 1 , wherein the volume resistivity of the matrix is more than 1.0×10 12 Ω·cm.
7. An electrophotographic apparatus comprising: an electrophotographic photosensitive member and a charging member,
wherein the electrophotographic photosensitive member includes a support and a photosensitive layer,
when average local potential differences of respective calculated lengths, the calculated lengths each are obtained by defining n as respective integers from 1 to 5,000, are determined based on the following calculation method by using a value obtained by charging an outer surface of the electrophotographic photosensitive member with −500 V, assuming that a straight line having a length of 5,000 μm is placed at an arbitrary position on the charged outer surface, and measuring potentials at measurement points located on the straight line at a pitch of 1 μm, a maximum value of the average local potential differences is 2 V or more,
the charging member includes a support and an electro-conductive layer,
the electro-conductive layer has a matrix and domains dispersed in the matrix,
at least some domains are exposed to an outer surface of the charging member,
the matrix contains a first rubber,
the domain contains a second rubber and an electronic electro-conductive agent,
a volume resistivity ρM of the matrix is at least 1.00×10 5 times a volume resistivity ρD of the domain, and
when a calculated length in which a maximum value of the average local potential difference is obtained is defined as S CP [μm] and an arithmetic mean value of distances between wall surfaces of the domains observed on an outer surface of the electro-conductive layer is defined as D ms [μm], S CP ≥3×D ms ,
the calculation method comprising:
i) dividing the straight line into calculated length n×1 μm (where, n is an integer of 1 or more) to obtain 5,000/n [number] regions;
ii) calculating an average value of potentials, the potentials being obtained at all measurement points included in each region;
iii) calculating a difference between regions adjacent to each other with respect to the average value of the potentials at each region calculated in ii) (local potential difference); and
iv) calculating an average value of the local potential differences (average local potential difference) obtained between the regions.
8. The electrophotographic apparatus according to claim 7 , further comprising a transfer unit, wherein the transfer unit includes a support and a transfer member having an electro-conductive foam layer.
9. The electrophotographic apparatus according to claim 8 , wherein an average cell diameter L tr [μm] of foam cells in the electro-conductive foam layer observed on an outer surface of the transfer member is 3 times or more of S CP [μm].
10. The electrophotographic apparatus according to claim 9 , wherein L tr is 200 μm or more and 500 μm or less.
11. The electrophotographic apparatus according to claim 9 , wherein L tr , S CP , and D ms satisfy a relationship of 3×(D ms ·L tr ) 0.5 ≤S CP ≤7×(D ms ·L tr ) 0.5 .