This invention is generally directed to the use of amorphous carbon, including hydrogenated, and halogenated amorphous carbon compositions as electrostatographic imaging members. More specifically, the present invention is directed to photoresponsive imaging members, including layered members comprised of amorphous carbon that possesses photoconductive properties. In one embodiment of the present invention there are provided photoconductive imaging members comprised of amorphous carbon with a band gap of from about 0.5 to about 5 electron volts. Also encompassed within the present invention are layered photoconductive imaging members comprised of amorphous carbon with photoconductive properties situated on a supporting substrate, and wherein the member further includes an overcoating layer. Moreover, there is provided in accordance with the present invention imaging members comprised of amorphous carbon, and photoconductive hydrogenated amorphous silicon. Also, in another embodiment of the present invention, the photoconductive amorphous carbon is present in the imaging member in a gradient as detailed hereinafter. The aforementioned imaging members are particularly useful in electrostatographic imaging processes; and further, in some configurations the imaging members of the present invention can be selected for xerographic printing systems.
Electrostatographic imaging systems, and particularly xerographic imaging processes are extensively described in the prior art. Generally, in these processes, a photoresponsive or photoconductive material is selected for forming the latent electrostatic image thereon. The photoreceptor can be comprised of a conductive substrate containing on its surface a layer of photoconductive material, and in many instances a thin barrier layer is situated therebetween to prevent charge injection from the substrate, which could adversely affect the quality of the resulting image. Examples of known useful photoconductive materials include amorphous selenium, alloys of selenium such as selenium tellurium, selenium arsenic, and the like. Additionally, there can be selected as the imaging member various organic photoconductive materials including, for example, complexes of trinitrofluorenone and polyvinylcarbazole. Recently, there has been disclosed layered organic photoresponsive devices with arylamine hole transport molecules and photogenerating layers, reference U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference.
Many other patents are in existence describing photoresponsive devices with generating substances, such as U.S. Pat. No. 3,041,167, which discloses an overcoated imaging member containing a conductive substrate, a photoconductive layer, and an overcoating layer of an electrically insulating polymeric material. This member is utilized in an electrophotographic copying method by initially charging with an electrostatic charge of a first polarity, imagewise exposing, and subsequently developing to enable the formation of a visible image. Prior to each succeeding imaging cycle, the photoconductive member can be charged with an electrostatic charge of a second opposite polarity. Sufficient additional charges of the second polarity are applied so as to create across the member a net electrical field. Simultaneously, mobile charges of the first polarity are formed in the photoconductive layer by applying an electrical potential to the conductive substrate.
Also known are amorphous silicon photoconductors, reference for example U.S. Pat. Nos. 4,265,991 and 4,225,222. There is disclosed in the U.S. Pat. No. 4,265,991 an electrophotographic photosensitive member comprised of a substrate, and a photoconductive overlayer of amorphous silicon containing 10 to 40 atomic percent of hydrogen and having a thickness of 5 to 80 microns. Additionally, this patent describes several processes for preparing amorphous silicon. In one process, there is prepared an electrophotographic photosensitive member which involves heating the member present in a chamber to a temperature of 50.degree. C. to 350.degree. C., introducing a gas with a hydrogen atom, providing an electrical discharge in the chamber by electric energy to ionize the gas, followed by depositing amorphous silicon on an electrophotographic substrate at a rate of 0.5 to 100 Angstroms per second by utilizing an electric discharge while raising the temperature of the substrate thereby resulting in an amorphous silicon photoconductive layer of a predetermined thickness. Although the amorphous silicon device described in this patent is photosensitive, after a minimum number of imaging cycles, less than about 10 for example, unacceptable low quality images of poor resolution with many deletions may result. With further cycling, that is, subsequent to 10 imaging cycles and after 100 imaging cycles, the image quality may continue to deteriorate often until images are partially deleted.
There are also illustrated in copending applications photoconductive imaging member comprised of amorphous silicon. Accordingly, for examples, there is disclosed in copending application U.S. Ser. No. 695,990, entitled Electrophotographic Devices Containing Compensated Amorphous Silicon Compositions, the disclosure of which is totally incorporated herein by reference, an imaging member comprised of a supporting substrate and an amorphous hydrogenated silicon composition containing from about 25 parts per million by weight to about 1 percent by weight of boron compensated with substantially equal amounts of phosphorous and boron. Furthermore, described in copending application U.S. Ser. No. 548,117, entitled Electrophotographic Devices Containing Overcoated Amorphous Silicon Compositions, the disclosure of which is totally incorporated herein by reference, are imaging members comprised of a supporting substrate, an amorphous silicon layer, a trapping layer comprised of doped amorphous silicon, and a top overcoating layer. Additionally, described in copending application U.S. Ser. No. 662,328, entitled Heterogeneous Electrophotographic Imaging Members of Amorphous Silicon, the disclosure of which is totally incorporated herein by reference, are imaging members comprised of hydrogenated amorphous silicon photogenerating compositions, and a charge transporting layer of plasma deposited silicon oxide. There is further disclosed in the latter copending application an interface transition gradient between the silicon oxide charge transport layer and the photogenerating layer.
Other representative prior art patents that disclose amorphous silicon imaging members include for example, U.S. Pat. No. 4,357,179 directed to methods for preparing imaging members containing high density amorphous silicon or germanium; U.S. Pat. No. 4,237,501 which discloses a method for preparing hydrogenated amorphous silicon wherein ammonia is introduced into a reaction chamber; U.S. Pat. Nos. 4,359,514; 4,404,076; 4,403,026; 4,397,933; 4,416,962; 4,423,133; 4,461,819, 4,490,453; 4,237,151; 4,356,246; 4,361,638; 4,365,013; 3,160,521; 3,160,522; 3,496,037; 4,394,426; and 3,892,650.
Although the above-described amorphous silicon photoresponsive imaging members, including the compensated members, may be useful for their intended purposes, there continues to be a need for new imaging members. Also, there is a need for improved photoconductive materials which can be continuously used in a number of imaging cycles without deterioration therefrom. Additionally, there is a need for improved photoresponsive imaging members comprised of amorphous carbon which are humidity insensitive and are not adversely affected by the electrical consequences resulting from scratching and abrasion. Moreover, there is a need for improved photoconductive imaging members comprised of amorphous carbon which can be prepared with a minimum number of processing steps, and wherein the layers are sufficiently adhered to one another to enable the continuous use thereof in repetitive imaging and printing processes. Furthermore, there continues to be a need for amorphous carbon photoconductive substances which can be selected for incorporation into electrostatographic imaging processes; and wherein these substances are not sensitive to humidity and corona ions generated by the charging apparatus, thereby allowing the use thereof over a substantial number of imaging cycles without causing a degradation in image quality, and which members possess other desirable characteristics. Furthermore, there is a need for photoresponsive imaging members will superior hardness characteristics, enabling them to be useful for substantially an unlimited number of imaging cycles. Also, there is a need for photoresponsive imaging members wherein amorphous carbon can be selected as a transporting layer, and wherein the member further includes therein a photogenerating substance such as amorphous silicon. Additionally, there is a need for imaging members wherein there is selected as a grounding strip or grounding plane amorphous carbon.