This invention relates in general to an electrophotographic imaging system, and more specifically, to an electrophotographic imaging member containing an interface layer and a method of utilizing such device.
The formation and development of images on the imaging surfaces of electrophotographic imaging members by electrostatic means is well known. One of the most widely used processes being xerography described, for example, in U.S. Pat. No. 2,297,691. Numerous different types of photoreceptors can be used in the electrophotographic imaging process. Such electrophotographic imaging members may include inorganic materials, organic materials, and mixtures thereof. Electrophotographic imaging members may comprise contiguous layers in which one or more of the layers performs a charge generation function and the other layer forms a charge carrier transport function or may comprise a single layer which performs both the generation and transport functions. These electrophotographic imaging members may be coated with a protective overcoating to improve wear. For Carlson type electrophotographic imaging processes, the protective overcoating must allow the electrostatic charge initially deposited on the outer surface of the overcoating to form at the interface between the protective overcoating and the underlying photoconductive layer prior to repeating the next imaging cycle. Protective overcoatings may be of various organic and inorganic materials including resins, photoconductive materials and the like.
Electrophotographic imaging members based on amorphous selenium have been modified to improve panchromatic response, increase speed and to improve color copyability. These devices are typically based on alloys of selenium with tellurium. The selenium electrophotographic imaging members may be fabricated as single layer devices comprising a selenium-tellurium alloy layer which performs both charge generation and charge transport functions. The selenium electrophotographic imaging members may also contain multiple layers such as, for example, a selenium alloy transport layer and a contiguous selenium-tellurium alloy generator layer. These multiple layer electrophotographic imaging members containing a selenium-tellurium alloy generator layer are characterized by varying degrees of electrical instability during cycling. For example, multiple layer electrophotographic imaging members containing a selenium-tellurium alloy generator layer containing about 10 percent by weight tellurium and a selenium-arsenic alloy transport layer exhibit significant levels of residual cycle-up which may be further aggravated by cycle rate, thermal cycling at elevated temperatures and by undesirable interactions with lamps around the electrophotographic imaging member. Residual cycle up is the cumulative development of increasing levels of residual voltage with cycling. Residual voltage is that potential measured at the surface of the photoreceptor following photodischarge of the photoreceptor by high levels of light exposure. The residual voltage is a reflection of the existence of positive charge (in the case of a positive charging system) trapped in the bulk of the photoconductive layers or at interfaces between layers in the device. The rate of residual cycle up and its ultimate saturation value is generally observed to increase with increasing cycle rate. Equilibration of the photoreceptor at temperatures above room temperature either during photoreceptor storage or during machine operation also generally leads to a temporary enhancement of residual cycle up, both its rate of increase and its saturation value. Similarly, exposure of electrophotographic imaging members containing a selenium-tellurium alloy generator layer to radiation in the 600 to 700 nanometer range, e.g. light from tungsten or fluourescent room lights, during installation of the imaging member in a copier, duplicator or printer can cause a marked increase in cycle-up during subsequent use due to bulk absorbed radiation.
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