Charging member, manufacturing method therefor, a process cartridge, and electrophotographic apparatus

Abstract

To provide a charging member which suppresses the generation of density nonuniformity in an electrophotographic image caused by charge nonuniformity due to adhesion of charged substances, such as toner particles. There is provided a charging member which has a surface layer, the surface layer includes conductive zinc oxide whiskers each formed of a nuclear portion and four needle crystal portions extending radially outward therefrom, and the needle crystal portions are exposed to form convex portions of a surface of the surface layer.

1 . A charging member comprising a surface layer,
 wherein:   the surface layer comprises conductive zinc oxide whiskers each having a nuclear portion and four needle crystal portions extending radially outward therefrom, and   at least one of the needle crystal portions is exposed on the surface of the surface layer so as to form a convex portion on the surface of the surface layer.   
     
     
         2 . The charging member according to  claim 1 ,
 wherein the needle crystal portions exposed on the surface of the surface layer have an exposed average aspect ratio of 10 or more and an exposed average length of 5 μm or more.   
     
     
         3 . The charging member according to  claim 2 ,
 wherein the exposed average aspect ratio is 30 or less, and the exposed average length is 19 μm or less.   
     
     
         4 . The charging member according to  claim 1 ,
 wherein the surface layer further comprises a thermosetting resin.   
     
     
         5 . The charging member according to  claim 4 ,
 wherein the thermosetting resin is a thermosetting urethane resin.   
     
     
         6 . A charging member comprising:
 a conductive base; and   a surface layer comprising conductive zinc oxide whiskers,   wherein the conductive zinc oxide whiskers each have a nuclear portion and four needle crystal portions extending radially outward therefrom and are partially buried in the surface layer, and   at least one of the needle crystal portions is exposed on the surface of the surface layer so as to form a convex portion on the surface of the surface layer.   
     
     
         7 . A method for manufacturing a charging member provided with a surface layer, the surface layer comprising conductive zinc oxide whiskers each having a nuclear portion and four needle crystal portions extending radially outward therefrom, and at least one of the needle crystal portions are exposed on a surface of the surface layer so as to form a convex portion on a surface of the surface layer, wherein:
 the method comprises (1) forming a resin layer used as a base of the surface layer;
 (2) dispersing the conductive zinc oxide whiskers in a poor solvent for a resin forming the resin layer; 
 (3) applying a dispersion obtained in the step (2) on the resin layer, and 
 (4) melting the resin layer processed in the step (3) to bury a part of the conductive zinc oxide whiskers in the resin layer. 
   
     
     
         8 . A process cartridge comprising:
 an electrophotographic photosensitive member; and   a charging member according to  claim 1 ,   wherein the process cartridge is detachable and mountable to a main body of an electrophotographic apparatus.   
     
     
         9 . An electrophotographic apparatus comprising:
 an electrophotographic photosensitive member; and   a charging member according to  claim 1 .