Charging device, image forming unit and image forming apparatus
View Patent ↗A charging device includes a charging member that charges a surface of an image bearing body. The charging member includes a rotation shaft applied with a voltage, and a resilient conductive layer provided on an outer circumferential surface of the rotation shaft. The resilient conductive layer charges the surface of the image bearing body. The resilient conductive layer has a plurality of high resistance regions arranged at intervals in an axial direction of the rotation shaft.
1. A charging device comprising:
a charging member that charges a surface of an image bearing body;
wherein the charging member includes a rotation shaft applied with a voltage, and a resilient conductive layer provided on an outer circumferential surface of the rotation shaft, the resilient conductive layer having a plurality of grooves on a surface thereof;
wherein the resilient conductive layer further has a plurality of cracks formed at valleys of the grooves; and
wherein the cracks extend in a rotating direction of the charging member, and are arranged at intervals in an axial direction of the rotation shaft.
2. The charging device according to claim 1 , wherein:
the cracks have a depth greater than or equal to 20 μm from the surface of the resilient conductive layer; and
at least five cracks are provided in an area of 5 mm 2 on the surface of the resilient conductive layer parallel to the axial direction.
3. The charging device according to claim 1 , wherein:
the cracks have a depth greater than or equal to 20 μm from the surface of the resilient conductive layer; and
at least one crack is provided in an area of 1 mm 2 on the surface of the resilient conductive layer parallel to the axial direction.
4. The charging device according to claim 1 , wherein the cracks are formed by irradiating the surface of the resilient conductive layer with ultraviolet rays.
5. The charging device according to claim 1 , wherein the grooves extend in the rotational direction of the charging member.
6. The charging device according to claim 1 , wherein:
a protection film is formed on the surface of the resilient conductive layer; and
the cracks are formed in the protection film.
7. The charging device according to claim 6 , wherein the protection film is an oxide film.
8. The charging device according to claim 6 , wherein a protection film covers surfaces of the cracks.
9. The charging device according to claim 1 , wherein the voltage applied to the rotation shaft is a direct voltage.
10. The charging device according to claim 1 , wherein the resilient conductive layer contains 20 weight parts or more of diene-based rubber with respect to 100 weight parts epichlorohydrin rubber.
11. The charging device according to claim 1 , wherein the resilient conductive layer contains 150 weight parts or less of diene-based rubber with respect to 100 weight parts epichlorohydrin rubber.
12. An image forming unit comprising the charging device according to claim 1 .
13. An image forming apparatus comprising the charging device according to claim 1 .
14. The charging device according to claim 1 , wherein the cracks do not cross each other.
15. The charging device according to claim 1 , wherein the grooves have a maximum height roughness Ry of between 1 μm and 40 μm.