Surface coatings for the bias charging roller

#In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member. The latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. Specifically, the photosensitive member is charged and then exposed to light from an optical system or an image input apparatus to form the electrostatic latent image thereon. After the toner particles have been deposited on the surface of the photoconductive member, they are transferred to a copy sheet or to an intermediate transfer member and subsequently transferred to a copy sheet. Permanent images are then formed on the copy sheet by a fusing process.

#Bias charging rollers (BCRs) are often used as chargers for corona charging the photosensitive member because they emit less ozone and are more environmentally friendly, as compared with scorotron chargers. However, BCR charging requires direct contact with the photosensitive member and with other related printer members. Due to this direct contact, stress is added on the surface of the BCRs as well as on the related printer members that come in direct contact with the BCRs. Surface deformations are then formed including streaks, abrasions, and pothole-like deformations that consequently produce print defects. For example, dark streaks and white/dark spots can appear as a result of degradation and/or debris built up on the surface of BCRs. Usage life of BCRs and the related printer members is then reduced.

#There is a need to provide materials and methods for bias charging members with desirable surface, electrical, and/or mechanical properties to extend their usage life.

#The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the present teachings and together with the description, serve to explain the principles of the present teachings.

#FIGS. 1A-1B depict various exemplary bias charging devices in accordance with various embodiments of the present teachings.

#FIGS. 2A-2B depict various exemplary outer surface coatings for a bias charging member in accordance with various embodiments of the present teachings.

#It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale.

#Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments in which the present teachings may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present teachings and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present teachings. The following description is, therefore, merely exemplary.

#FIGS. 1A-1B depict exemplary bias charging devices in accordance with various embodiments of the present teachings. For example, each device in FIGS. 1A-1B can include a photosensitive member, such as a photoconductive drum 110, which can be charged on its surface by a charger to which a voltage can be supplied by a power source 108. The charger can be, for example, a bias charging member in a form of a bias charging roller 120 A-B as depicted in FIGS. 1A-1B, although one of ordinary skill in the art will understand that other types of bias charging members can be used including a bias charging belt, sheet, film, or drelt (a cross between a belt and a drum) in accordance with various embodiments of the present teachings. Accordingly, various conductive substrates in a form of a roller, a belt, and/or a drelt can be used for the bias charging members in the bias charging devices.