1. Field of the Invention
The present invention relates to a member for electrophotography, a process cartridge and an image forming apparatus.
2. Description of the Related Art
In image forming apparatuses based on an electrophotographic method, a member for electrophotography is employed in various uses, for example, a charging member, a developing member and a transfer member. In the case of employing the member for electrophotography in these uses for a long period, powders such as external additives or toner remaining on an image bearing member adhere as dirty substances to the surface of the member for electrophotography. For example, as for a charging member, when such dirty substances adhere to the surface of the charging member, this area with the dirty substances adhering thereto partially has higher resistance resulting in poor charging. As a result, image density unevenness may occur due to the dirt.
In recent years, higher image quality, higher speed and higher durability have been demanded for image forming apparatuses. In response to these requirements, there is a tendency to reduce the particle diameter of toner and use various types of external additives. As a result, the dirty substances are deposited in larger amounts on the charging member.
A cleaner-less system (toner recycle system) has been proposed from the viewpoint of simplifying image forming apparatuses or eliminating wastes. This method does without a cleaner, which is a cleaning unit on an image bearing member, after a transfer step. The method removes residual toner on the image bearing member after transfer, from the image bearing member by “cleaning simultaneous with development” using a developing apparatus and recovers the toner into the developing apparatus for recycling. The cleaning simultaneous with development is a method which recovers residual toner remaining on the image bearing member after transfer, by use of a fog removing bias (fog removing potential difference Vback which is a potential difference between direct-current voltage applied to the developing apparatus and the surface potential of the image bearing member) during development in the subsequent step or later. In the case of applying a charging member of a contact charging method to the cleaner-less system, the amount of dirty substances, particularly, toner, remaining on the image bearing member is increased as compared with a case having a cleaner. Thus, the adhesion of dirty substances to the charging member is a more significant problem.
As a unit for reducing the adhesion of dirty substances such as external additives or toner, Japanese Patent No. 5455336 and Japanese Patent Application Laid-Open No. 2008-083404 disclose a charging member for which the amount of dirty substances adhering is reduced by the control of surface roughness through a particle contained in a surface layer.
The present invention is directed to providing a member for electrophotography that can more highly inhibit the adhesion of dirty substances to the surface.
The present invention is also directed to providing a process cartridge and an image forming apparatus that can form a high-quality image.