An image forming method according to an electrophotographic system includes: forming an electrostatic latent image on the surface of an electrophotographic photoreceptor by means of charging (primary charging) and exposure (image exposure); developing the electrostatic latent image with toner; transferring the resultant developed image (toner image) onto a transfer material such as paper; and fixing the transferred image to obtain an image.
Systems for developing an electrostatic latent image are roughly classified into: a contact development system in which a developer layer carried on a developer carrier (such as a developing roller or a developing sleeve) is brought into contact with the surface of an electrophotographic photoreceptor to perform development; and a jumping development system in which a developer carried on a developer carrier is allowed to fly to the surface of an electrophotographic photoreceptor to perform development.
The contact development system has an advantage in that the structure of a developing device can be simplified because a mechanism for allowing a developer to fly is not needed. However, a developer layer is pressed against the surface of an electrophotographic photoreceptor, so there arises a disadvantage in that toner in the developer is apt to fuse to the surface of the electrophotographic photoreceptor (hereinafter, also referred to as “toner fusion”).
Therefore, an electrophotographic photoreceptor to be combined with contact development must have a surface with high releasability and hardly cause toner fusion.
In recent years, an organic electrophotographic photoreceptor using an organic photoconductive substance has been used as an electrophotographic photoreceptor because of its advantages, such as freedom from pollution, high productivity, and ease of material design Examples of a method of increasing the releasability of the surface of an electrophotographic photoreceptor, especially an organic electrophotographic photoreceptor include a method involving incorporating a releasing agent such as silicone oil or a fluorine atom-containing resin particle into the surface layer (outermost layer) of the electrophotographic photoreceptor.
However, it is difficult to allow silicone oil to be uniformly present in the surface layer. In addition, silicone oil is a material that tends to migrate to the surface of the surface layer. Therefore, there arises a disadvantage in that, even if desired releasability is obtained at an initial stage, the releasing effect disappears when the surface of the surface layer is worn out through repeated use.
In contrast, a fluorine atom-containing resin particle can be allowed to be uniformly present in the surface layer by means of a dispersing agent (see JP-A 2000-081715, JP-A 2001-249481, or the like). In addition, the particle has a higher releasing effect than that of silicone oil.