1. Field of the Invention
The subject matter of this invention relates to photoreceptors. More particularly, the subject matter of this invention relates to self erasing photoreceptors containing an optically transparent, conductive electroluminescent carbon nanotube ground plane for use in an electrophotographic apparatus.
2. Background of the Invention
Trends in color xerographic printing include reduced box weight and size, higher process speeds and parallel printing in order to minimize cost, improve productivity and reliability. This has led to a drive for smaller photoreceptors, particularly drum photoreceptors which results in squeezing the space available to the subsystem components disposed around the photoreceptor. In electrophotographic systems, after the transfer of the toner to the paper, the toner is cleaned off the photoreceptor and the photoreceptor is exposed to an erase light to remove the residual latent image. However, long print runs of a single image can lead to variations in optical transparency related to image content. Further conductive ground planes based on strongly reducing metals such as Al, Ti, Zr are gradually converted to their oxides as a result of xerographic cycling. Also, holes traversing the photoreceptor in combination with ambient water electrochemically convert the metals to their insulating oxides resulting in a change in charge acceptance and transparency. Consequently both the erase illumination and ground plane conductivity vary spatially according to image content leading to image ghosts which limits photoreceptor life. Suitable materials for non-electrochemically reactive, optically transparent conductive ground planes are limited. Dispersed carbon particles are not electrochemically reactive but they are unsuitable material for conductive ground plane because of poor optical transparency. Other alternative optically transparent conductive ground planes such as cuprous oxide and conducting polymers including polypyrrole and polyaniline have problems due to relative immaturity of the technology.
Furthermore, it is difficult to achieve both high optical transparency and low ground plane resistivity (i.e. sheet resistivity) at the same time in either carbon filled or conductive ground planes based on metals such as Al, Ti, Zr. Moreover, belt photoreceptors that erase by illuminating through the ground plane, i.e. by “rear erase” require further increase in erase lamp intensity. In addition, the use of an anti-curl back coat on a belt photoreceptor further increases the need for higher intensity erase illumination because over time its surface becomes rather scratched and abraded. Consequently some of the illumination is scattered or diffracted and is prevented from reaching the charge generator layer.
Thus, there is a need to overcome these and other problems of the prior art to provide a method and system for internal erase illumination or “self erasing” of the photoreceptor comprising electroluminescent conductive ground plane.
In accordance with the invention, there is an electrophotographic photoreceptor. The electrophotographic photoreceptor can include a conductive layer including a plurality of electroluminescent nanomaterials. The electrophotographic photoreceptor can also include a first contact electrically connected to a first edge of the conductive layer and an electrical ground and a second contact electrically connected to a second edge of the conductive layer and a D.C. power supply. Furthermore, the electrophotographic photoreceptor can have the D.C. power supply configured to supply a lateral voltage bias at the second contact to generate a localized electroluminescence across the conductive layer and deliver an erase illumination from within the electrophotographic photoreceptor. The electrophotographic photoreceptor can also include a photosensitive layer disposed over the conductive layer, wherein the photosensitive layer includes a charge generation material and a charge transport material. Moreover, the electrophotographic photoreceptor can have the D.C. power supply configured to supply a lateral voltage bias at the second contact to generate a localized electroluminescence across the conductive layer and deliver an erase illumination from within the electrophotographic photoreceptor.
According to another embodiment of the present teachings, there is an image forming apparatus. The image forming apparatus can include an electrophotographic photoreceptor, wherein the electrophotographic photoreceptor includes a conductive layer, and wherein the conductive layer includes a plurality of electroluminescent nanomaterials. The image forming apparatus can also include a charging station for uniformly charging the electrophotographic photoreceptor and an imaging station for forming a latent image on the electrophotographic photoreceptor. The image forming apparatus can further include a development subsystem for converting the latent image to a visible image on the electrophotographic photoreceptor and a transfer station for transferring and fixing the visible image onto a media. The image forming apparatus can have the conductive layer with a first edge and a second edge opposite the first edge, wherein the first edge has a first contact connected to an electrical ground and the second edge has a second contact connected to a D.C. power supply. Moreover, the image forming apparatus can have the D.C. power supply configured to supply a lateral voltage bias at the second contact to generate a localized electroluminescence across the conductive layer and deliver an erase illumination from within the electrophotographic photoreceptor.
According to yet another embodiment of the present teachings, there is a method of forming an image. The method can include providing an electrophotographic photoreceptor, wherein the electrophotographic photoreceptor includes a conductive layer, and wherein the conductive layer includes a plurality of electroluminescent nanomaterials. The method can also include providing an imaging station for forming a latent image on the electrophotographic photoreceptor and providing a development subsystem for converting the latent image to a visible image on the electrophotographic photoreceptor. The method can further include providing a transfer station for transferring and fixing the visible image onto a media and applying a bias voltage laterally across the conductive layer to make the conductive layer glow laterally and deliver erase illumination from within the electrophotographic photoreceptor.
Additional advantages of the embodiments will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present embodiments, 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.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5.
The term “electrophotographic photoreceptor” is used interchangeably herein with “image receptor” and “photoreceptor”. The term “conductive layer” is used interchangeably herein with “ground plane”, “conductive ground plane”, “electroluminescent conductive layer”, “optically transparent conductive ground plane”, etc. The term “nanomaterial” is used herein to refer to any material having at least one dimension in the nanoscale range of about 0.1 nm to about 100 nm, including but not limited to, for example, nanotubes, nanofibers, nanotorus, etc. Hence, nanomaterials, such as carbon nanotubes, need to have only a diameter in the nanoscale range, but a length of the carbon nanotube can be several millimeters, and similarly carbon nanotube sheets need to have only thickness in the nanoscale region, the width and length of the carbon nanotube sheet can be in the nanoscale, microscopic, or macroscopic range.
Self erasing photoreceptor including a conductive ground plane including a plurality of electroluminescent nanomaterials can provide several advantages. In some embodiments, the internal erase illumination can provide optical advantage of minimal required erase illumination because of proximity to the charge generating layer. In other embodiments, the fewer internal reflections can also minimize the required erase electroluminescent illumination. Additionally, internally generated illumination can not be diffracted by the scratched rear surface of a belt photoreceptor which occurs over time.
According to various embodiments, the plurality of electroluminescent nanomaterials can include a plurality of carbon nanotubes. In some embodiments, the conductive layer 110 can include carbon nanotube composite, including but not limited to carbon nanotube polymer composite, epoxy based carbon nanotube composite, and carbon nanotube filled resin.
The conductive layer 110 including carbon nanotubes can have several advantages over conventional metal films used for conductive ground planes. Carbon nanotubes exhibit many desirable properties for conductive ground plane such as high optical transparency with electronic conductivity, are non-oxidizable, flexible, and have high tensile strength. Carbon nanotubes can also exhibit electroluminescence in the visible and into the infrared spectrum, the wavelength range used for erasing in a photoreceptor. Baughman et. al. in Science, 2005, Vol. 309, No. 5738, pp. 1215-1219 disclosed a new method of producing transparent carbon nanotube sheets at a rate more than about seven meters per minute, which is incorporated by reference herein in its entirety. These un-optimized carbon nanotube sheets can exceed steel and carbon fiber material such as Kevlar in gravimetric strength. For example, micron thick carbon nanotube sheets can support liquid droplets 50,000 times their own weight. Also, carbon nanotube sheet can act as electrodes that can be reversibly deformed without losing electrical conductivity. Further, as electrodes, the carbon nanotube sheets can exhibit very little change in conductivity over a very wide temperature range.
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According to various embodiments, the electrophotographic receptor 100, 300 can be a belt photoreceptor or a drum photoreceptor. However, current drum photoreceptors are based on a conductive drum substrate. Hence, the conductive substrate of the drum photoreceptor can be anodized in order not to short out the lateral voltage bias applied to the conductive layer 110. Alternatively, a plastic substrate can be used in the drum photoreceptor, and electrophotographic photoreceptor 100, 300 can be disposed over the plastic substrate. Further, to save space in drum photoreceptor, the location of the light emission can be coincident with the cleaning sub-system.
In accordance with the invention, there is a method of forming an image. The method can include providing an electrophotographic photoreceptor 401, wherein the electrophotographic photoreceptor 401 can include a conductive layer 410 including a plurality of electroluminescent nanomaterials and a photosensitive layer 430 disposed over the conductive layer 410. The method can also include providing a charging station 440 for uniformly charging the electrophotographic photoreceptor 401. The method can further include providing an imaging station 450 where an original document (not shown) can be exposed to a light source (also not shown) for forming a latent image on the electrophotographic photoreceptor 401. The method can also include providing a development subsystem 460 for converting the latent image to a visible image on the electrophotographic photoreceptor 401 and a transfer station 470 for transferring and fixing the visible image onto a paper or other media. Furthermore, the method can include applying a bias voltage laterally across the conductive layer 410 to make the conductive layer 410 glow laterally and thereby deliver erase illumination. The erase illumination across the conductive layer 410 can be from about 0.5 mm to about 10 cm and in some cases from about 1 mm to about 5 cm in width. According to various embodiments, the plurality of electroluminescent nanomaterials can include a plurality of carbon nanotubes. In other embodiments, the plurality of electroluminescent nanomaterials can include at least one carbon nanotube sheet.
While the invention has been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.