Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/043—Photoconductive layers characterised by having two or more layers or characterised by their composite structure
  • G03G5/0433—Photoconductive layers characterised by having two or more layers or characterised by their composite structure all layers being inorganic
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/043—Photoconductive layers characterised by having two or more layers or characterised by their composite structure
  • G03G5/0436—Photoconductive layers characterised by having two or more layers or characterised by their composite structure combining organic and inorganic layers

Definitions

• the photoconductive insulator performs two functions, namely charge generation and charge transport. In themost commonly used processes, both functions are performed by a single layer, for example a layer of vitreous selenium. These two functions may each be performed by a separate layer, and it is with such systems that the present invention deals.
• the present invention provides novel charge generation layers for use in electrophotographic plates. These novel charge generation layers consist essentailly of from 5 to 35 percent by weight tellurium, and from 0.5 to 20 percent by weight arsenic, with the substantial balance being vitreous selenium. The most preferred composition is from 25 to 30 percent tellurium and from 2 to percent arsenic.
• This three-component composition possesses unexpected advantages as a charge generation layer. In particular, it is extremely versatile.
• the charge generation layers of the present invention can generate either electrons or holes. Furthermore, they are in some cases suitable for use on top of charge transport layers, and in other cases, beneath charge transport layers.
• the novel charge generation layers of the present invention may be used with either positive charging or negative charging.
• the versatility of the charge generation layers of the present invention is such that they can, for example, be used to generate holes when they are positively charged as an overcoat for a vitreous selenium charge transport layer.
• the charge generation layers of the present invention may be used to generate electrons when they are negatively charged and rest upon a layer of organic photoconductor such as described in U.S. Pat. No. 3,484,237 of Shattuck and Vahtra.
• the novel charge generating layers of the present invention may be overcoated by a layer of polyester containing trinitrofluorenone and charged in the positive mode.
• vitreous selenium transport layer having as an interface with the charge generation layer a gradient composition comprising selenium and amounts of arsenic and tellurium which decrease with increasing distance from the charge generation layer surface. It is thus seen that, depending upon the proper choice of charge transport layer, the charge genera-tion layers of the present invention may be either overcoated onto the charge transport layer. or overcoated by the charge transport layer, and may be charged in either the negative mode or the positive mode. This extreme versatility was totally unexpected, and constitutes one of the major advantages of the present invention.
• the most outstanding advantage of the present invention is its very high sensitivity, over a very broad spectral range, when it is used as a charge generation layer with a suitable charge transport layer.
• An additional advantage of the present invention is that it is suitable for use on a wide variety of substrates, both rigid and flexible, and of many different shapes.
• the charge generating layers of the present invention be from about 0.02 to about 1.5 microns thick, most preferably from about 0.05 to 1.0 microns. In most cases, the charge transport layers will be much thicker, for example from about 8 to about 15 microns. When the charge transport layer is on top of the charge generation layer, the charge transport layer must be at least partially transparent.
• barrier layer When the charge generation layers of the present invention are used in electrophotographic plates, in most cases it is preferred that a suitable barrier layer also be employed. Many types of barrier layers are well known in the art. They serve the functions of holding the charge and preventing carrier injection from the conductor substrate. Barrier layers may be organic, for example, polyamide or polyurethane, or they may be inorganic, for example, aluminum oxide. In many cases the aluminum oxide film normally present on an aluminum conductive substrate is a suitable barrier layer.
• a positive charging electrophotographic plate which consists of an I [L Se (68 wt. %)-Te (30 wt. %)-As (2 wt. generation layer overcoated onto a 35 to 50p vitreous Se transport layer on an anodized Al substrate, is prepared by using vacuum evaporation.
• the substrate is held at a temperature near 70C when the evaporations are conducted in a high vacuum system at a pressure of approximately I X 10" torr.
• the Se film is vacuum deposited by heating the Se source to approximately 290C for approximately 30 minutes. This is immediately followed by the deposition of the SeTeAs overlayer using flash evaporation of prealloyed granules.
• the crucible temperature for flash evaporation of SeTeAs is normally maintained at about 500C.
• a Sloan AMNl-II is used to monitor the deposit rates and film thicknesses of the Se and SeTeAs films.
• the electrophotographic plate is cooled in situ to 25C.
• this plate is corona charged to a positive potential of about 900 volts, and then exposed to a photocopy green light source at about 0.28 micro joules/Cm to form a latent electrostatic image on the plate surface.
• the latent image is then developed and transferred to a sheet of paper. A good quality image reproduced from the original is thus obtained.
• Quantum efficiency measurements indicate that this electrophotographic plate exhibits a broad spectral response with peak quantum efficiencies up to l, 0.8, and 0.5 at 4,000, 5,000 and 6,000 A respectively and shows weak field dependence of the quantum efficiency.
• EXAMPLE II A negative charging electrophotographic plate which consists of a 0.1;. Se (68 wt. %)-Te (30 wt. %)-As (2 wt. generation layer overcoated onto a 1 transport layer of the organic photoconductor disclosed in U.S. Pat. No. 3,484,237, on an aluminized Mylar substrate is prepared. (Mylar is duPonts brand of polyethyleneterephthalate.) the vacuum deposition of the SeTeAs film is carried out in the same manner as in Example 1 above except that in place of the 70C substrate temperature a substrate temperature of 45C is used.
• This plate is corona charged to a negative potential of about 700 volts and exposed to a photocopy green light source at about 0.87 micro-joules/cm to form a latent electrostatic image on the plate surface.
• the electrostatic image is then developed and transferred to a paper. The image thus obtained shows excellent quality with minimal background.
• a positive charging electrophotographic plate which consists of an aliminized Mylar substrate, a 0.3;. du Pont Elvamide 8061 (polyamide) barrier layer, an 1 u Se(68 wt. percent)-Te (30 wt. percent)-As (2 wt. percent) charge generation layer and a 10p. 1 to 1 by weight trinitrofluorenonepolyester resin transport layer, is prepared.
• the SeTeAs charge generation layer is fabricated as in Example 1 above.
• the transport layer is prepared by dissolving the 2, 4, 7-trinitrofluorenone (TNF) in tetrahydrofurane (THF) solvent with the Goodyear Vitel PE-ZOO polyester resin.
• Application of the transport layer, overlaying on the SeTeAs generation layer is normally accomplished by using a meniscus coating technique.
• This electrophotographic plate is corona charged to a positive potential of about 750 volts and exposed to a photocopy green light source at about 0.41 micro joules/cm 2 to form a latent image on the plate surface.
• This latent image when developed and transferred to a paper, shows excellent quality with little background.
• a positive charging electrophotographic plate is prepared as in Example lll above except that in place of the 1p. Se(68 wt %)-Te (30 wt. %)-As (2 wt. film, an In Se(70 wt. %)-Te (20 wt. %)-As (10 wt. is used as the generation layer.
• This plate is corona charged to a positive potential of about 700 volts. Upon exposure to a tungstenhalogen liggt source at about 0.89 micro joules/cm the plate is observed to discharge to a potential of about 200 volts.
• EXAMPLE V A negative charging electrophotographic plate, which consists of an anodized Al substrate, an lp. Se (73 wt. %)-Te (25 wt. %)-As (2 wt. charge generation layer and a lip.
• This plate is negatively corona charged and then exposed, developed and the toned image transferred in the same manner as the plate in Example 111. The image thus obtained shows good quality with a slight background. Quantum efficiency measurements indicate that this plate shows a broad spectral response with peak quantum efficiencies up to 0.56, 0.54 and 0.29 at 4,500, 5,000 and 6,000 A respectively.
• An electrophotographic plate comprising a conductive substrate, a charge transport layer, and a charge generation layer consisting essentially of from 5 to 35 percent by weight tellurium and from 0.5 to 20 percent by weight arsenic, with the substantial balance being vitreous selenium.
• An electrophotographic plate as claimed in claim 1 wherein the charge generation layer comprises from 2 to 10 percent by weight arsenic and from 25 to 30 percent by weight tellurium.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Light Receiving Elements (AREA)

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Cited By (15)

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Citations (7)

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• 1972
  • 1972-03-31 US US239984A patent/US3861913A/en not_active Expired - Lifetime
• 1973
  • 1973-02-12 JP JP48016686A patent/JPS5015137B2/ja not_active Expired
  • 1973-02-13 IT IT20301/73A patent/IT979037B/it active
  • 1973-02-20 FR FR7306808A patent/FR2178868B1/fr not_active Expired
  • 1973-02-28 CA CA165,478A patent/CA985550A/en not_active Expired
  • 1973-03-26 DE DE19732314867 patent/DE2314867A1/de not_active Ceased

Patent Citations (7)

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