Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/75—Details relating to xerographic drum, band or plate, e.g. replacing, testing
• • 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
  • G03G5/10—Bases for charge-receiving or other layers
• • 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
  • G03G5/14—Inert intermediate or cover layers for charge-receiving layers

Definitions

• a common type of electrographic element is an element comprising an electrically insulating support, an electrically conductive layer overlying the support, and an electrically insulating photoconductive layer overlying the electrically conductive layer.
• the photoconductive layer contains a normally insulating material whose electrical resistance varies with the amount of incident electromagnetic radiation it receives during an imagewise exposure.
• the electrically conductive layer can be a separate layer or a part of the support layer and can be formed from a wide variety of materials.
• the electrographic element can be opaque or transparent, depending upon the intended mode of use.
• the function of the electrically conducting layer in electrographic elements is to create a highly conducting reference plane which ideally is held at or near ground potential.
• the potential of the conducting layer has a tendency to build up with respect to ground if it is not grounded.
• the potential of an ungrounded conducting layer can vary from about 50 to about 450 volts or more.
• the differential between the conducting layer and the photoconductive layer may range from about 150 volts to about 550 volts.
• the photoconductive layer becomes conducting in the light-struck regions and the potential of the surface of the photoconductive layer in these areas approaches that of the conducting layer. Because of the small difference in potentials which may exist between areas struck by light and those not struck when the conducting layer is not grounded, little or no latent image is produced.
• the electrically conducting layer should be held at ground potential to insure that the maximum charge be impressed and stored in the photoconductive layer. Similarly poor results are obtained when the conducting layer is inefficiently grounded.
• Direct electrical contact with the conducting layer for grounding purposes is very difficult and inefficient when, as is usually the case, it is extremely thin, e.g., a few hundred angstroms, and creates wear problems if the element is contacted for grounding while in motion.
• the total thickness of material overlying the conductive layer can be so great as to prevent the electrically-conductive particles from being imbibed all the way from the surface of the element to the conductive layer and thereby render the method of U.S. Patent 3,6.84,503 inoperative.
• a piece of metallic foil is utilized to cover the exposed adhesive composition in the hole and provide a suitable surface for contact with an electrode.
• This patent also discloses that a channel can be formed in place of the hole and the electrically- conductive composition can be inserted into the channel.
• U.S. Patent 3,743,410 issued July 3, 1973 to R. I. Edelman et al, there is described an electrographic element adapted to be grounded while in motion which includes a channel in the photoconductive layer exposing the underlying conductive layer and an electrically-conductive material that has been inserted into the channel.
• Tha present invention provides improved electrical connection means within an electrographic element, which means are adapted to establish electrical connection between a conductive layer of the element and a grounding or biasing member which engages a surface of the element while the element is in motion.
• the electrographic element is comprised of an electrically insulating support, an electrically conductive layer overlying the support, and an electrically insulating.photoconductive layer overlying the conductive layer.
• the electrical connection means comprises a region of dispersed electrically-conducting particles within a non-recording portion of the element which extends from the surface of the element into contact with the conductive layer. This region defines on the surface of the element an elongated stripe which is longitudinally disposed in the direction of motion of the element and which encompasses an elongated longitudinally disposed groove.
• an elongated groove extending from the surface of the element at least to a position proximate to the conductive layer is formed in the element and an imbibable composition comprising the particulate material is then applied to the surface of the element as an elongated stripe which encompasses the groove.
• the groove serves to promote the imbibition of the particulate material into contact with the conductive layer so as to form an electrical path from the conductive layer to the stripe on the surface of the element and thus provide electrical connection with the grounding or biasing member which engages, the stripe.
• the electrographic element of this in- vention is adapted for use in an electrographic copier in which it is moved through a plurality of processing stations including an exposure station to form a visible image and in which the copier includes a grounding or biasing member for applying a reference potential to the conductive layer of the element during movement of the element through the exposure station.
• Means are provided within the copier for positioning the element during movement of an image area thereof through the exposure station to maintain effective contact between the grounding or biasing member and the stripe on the surface of the element, thereby connecting the reference potential to the conductive layer.
• FIG. 1 is a schematic representation of an electrographic copying apparatus employing the improved electrographic element of this invention.
• FIG. 2 is a face view of a portion of an electrographic element having electrical connection means in accordance with this invention disposed along one edge thereof and a row of perforations disposed along the opposite edge.
• FIG. 3 is a face view of a portion of an electrographic element having electrical connection means in accordance with this invention disposed along both edges thereof.
• FIG. 4-a is a cross sectional view taken along the line 4-4 in FIG. 2 illustrating the electrical connection means.
• FIG. 4-b is a cross sectional view of an alternative embodiment of the electrical connection means.
• FIG. 4-c is a cross sectional view of a further alternative embodiment of the electrical connection means.
• FIG. 5 is a cross sectional view illustrating the electrical connection means of this invention in an alternative embodiment of the electrographic element.
• FIG. 6 is a cross sectional view illustrating the electrical connection means in contact with a grounding or biasing member of an electrographic apparatus.
• PIG. 7 is a schematic illustration of the cutting of an elongated groove and formation of a conductive stripe in an electrographic element in accordance with this invention.
• FIG. 8 is a schematic illustration of an alternative procedure for cutting the elongated groove in an electrographic element.
• the present invention is characterized in its manufacture by the use, in combination, of an imbibable composition containing electrically conductive particles and a groove which extends from a surface of the electrographic element at least into proximity with the conductive layer of the element.
• This combination provides very effective electrical connection means under a wide variety of circumstances.
• the function of the groove in promoting the imbibition of the particulate material into contact with the conductive layer renders the method effective with electrographic elements having one or more layers overlying the conductive layer which to- gether are of such substantial thickness as to render it impossible to imbibe the particulate material all the way from the surface of the element to the conductive layer.
• a photoconductive layer, or other layer that overlies the conductive layer is comprised of a tough polymeric binder which is so resistant to imbibition of electrically conductive particles as to render it impossible to imbibe the particles all the way from the surface of the element to the conductive layer.
• the method of the present invention can be readily varied to render it especially suitable for the particular electrographic element involved.
• the groove can be relatively shallow as long as it is of sufficient depth to enable the electrically conductive particles to make good contact with the conductive layer.
• the groove may be desirable to form the groove with a depth such that only a very slight thickness of material overlies the conductive layer, or to form the groove with such a depth that the conductive layer is exposed but not penetrated, i.e., all overlying material is removed, or to form the groove with such a depth that it extends into the conductive layer or through the conductive layer and into the underlying material. Any of these techniques can be successfully utilized in carrying out the present invention.
• FIG. 1 there is schematically shown an electrographic copying apparatus 1 comprising an electrographic element 2 in the form of an endless belt configured for movement along an endless path past various operative stations of the apparatus.
• the electrographic element 2 is a layered structure comprising an electrically insulating support 3, an electrically conductive layer 4 overlying support 3, and an electrically insulating photoconductive layer 5 overlying conductive layer 4.
• the conductive layer 4 is electrically connected to ground or other selected reference potential source by engagement of element 2 with metal bristle brush 6.
• Operative stations of the apparatus 1 include a primary charging station at which corona discharge device 7 applies an overall charge to the external surface of photoconductive layer 5.
• a primary charging station at which corona discharge device 7 applies an overall charge to the external surface of photoconductive layer 5.
• an image segment of electrographic element 2 advances past the exposure station 8 wh.ere the segment is imagewise exposed by Xenon lamps or other known imaging apparatus to light patterns of a document to be copied.
• Rollers 16 serve to convey electrographic element 2 past the operative stations and properly position it during movement of the image segment through exposure station 8 to maintain effective contact between brush 6 and the surface of electrographic element 2.
• the electrostatic image residing on the image segment after passage through exposure station 8 is next advanced over a magnetic brush or other development station 9 where toner is attracted to the charge pattern corresponding to dark image areas of the document.
• the developed image is then advanced to a transfer station 10 where the toner image is transferred by the action of corona discharge device 12 to paper which is fed from supply 11.
• the paper bearing the toner image is then transported through a fixing station 13, for example, a roller fusing device, to a bin 14.
• the segment from which the toner is transferred advances past a cleaning station 15 in preparation for another copy cycle.
• electrographic element. 2 is shown to include a row of perforations 17 adjacent to one side thereof and electrical connection means 18 adjacent to the opposite side thereof.
• Electrographic element 2, provided with perforations 17, is especially adapted for use in an electrographic copying apparatus of the type described in U.S. Patent 3,914,047 issued October 21, 1975 to W. E. Hunt, Jr. et al.
• the perforations 17 are utilized to generate control timing signals for synchronizing machine functions as described in detail in U.S. Patent 3,914,047.
• Electrical connection means 18 comprises a region of dispersed electrically conductive particles, within a non- recording portion of electrographic element 2, which extends from the surface of electrographic element 2 and, as shown in FIG. 4, reaches into contact with electrically conductive layer 4.
• the dispersed electrically conductive particles can be of any suitable conducting material such as, for example, carbon black or graphite.
• the region of dispersed electrically conductive particles defines on the surface of electrographic element 2 an elongated stripe 19 which is longitudinally disposed in the direction of motion of electrographic element 2 and which encompasses an elongated longitudinally disposed groove 20.
• a second electrical connection means 21 comprising a region of dispersed electrically conductive particles which extends into contact with electrically conductive layer 4 and which defines an elongated longitudinally disposed stripe 22 which encompasses an elongated longitudinally disposed groove 23.
• contact of the dispersed electrically conductive particles with conductive layer 4 is achieved both as a result of the presence of groove 23 and as a result of contact with the exposed edges of conductive layer 4 within each of perforations 17.
• groove 20 extends from the exterior surface of electrographic element 2 at least to a position proximate to conductive layer 4.
• groove 20 terminates a short distance above the upper surface of conductive layer 4 and the dispersed electrically conductive particles have traveled by a process of imbibition from the bottom of groove 20 into contact with conductive layer 4.
• groove 20 is of a depth such as to expose conductive layer 4, that is, it terminates at the upper surface of conductive layer 4.
• Dispersed electrically conductive particles are in contact with conductive layer 4 at the bottom of groove 20 and also as a result of their lateral movement into photoconductive layer 5 by a process of imbibition.
• groove 20 extends completely through conductive layer 4 and into support 3 .
• Dispersed electrically conductive particles are in contact with conductive layer 4 at its exposed edges 24 and 24' within groove 20 and also as a result of their lateral movement into photoconductive layer 5 by a process of imbibition.
• FIG. 5 shows an alternative embodiment of electrographic element 2 which includes a subbing layer 25 between electrically conductive layer 4 and photoconductive layer 5 and a protective overcoat layer 26 over photoconductive layer 5.
• groove 20 extends from the surface of electrographic element 2 through each of overcoat layer 26, photoconductive layer 5, subbing layer 25, . and electrically conductive layer 4, and into support 3. Dispersed electrically conductive particles are in contact with conductive layer 4 at its exposed edges 24 and 24' within groove 20 and also as a result of their lateral movement into subbing layer 25 by a process of imbibition.
• grounded metal bristle brush 6 serves to engage stripe 19 as electrographic element 2 is conveyed past the operative stations of an electrographic copying apparatus. Since there is an electrical path from conductive layer 4 to the surface of electrographic element 2 (provided by the dispersed electrically conductive particles), this serves to ground conductive layer 4.
• Electrographic elements provided with improved electrical connection means in accordance with this invention can be formed using any of a wide variety of materials as the support.
• Typical supports include cellulose triacetate film, poly (vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film, paper, polymer-coated paper, and the like.
• Most usually the support is a tough, flexible, transparent, electrically insulating material such as a poly(ethylene terephthalate) film .
• the conductive layer in the electrographic elements of this invention is a thin layer which is sandwiched between the support and the photoconductive layer. It can be formed from many different photo- conductors, as is well known in the electrographic art. For example, it can be a thin sheet of a metal such as aluminum, copper, zinc or brass, or a metal foil such as an aluminum foil, or a vapor deposited metal layer of a metal such as silver, aluminum or nickel, or a layer which is a dispersion of a semi-conductor in a resin, as described for example in U.S. Patent 3,245,833, or a layer of an electrically conductive salt, as described for example in U.S. Patents 3,007,801 and 3,267,807.
• a further example of a useful conductive layer is a layer comprised of a dispersion of carbon black or graphite in a polymeric binder.
• the electrical connection means of this invention is a region of dispersed electrically conductive particles, which region defines an elongated conductive stripe on the surface of the electrographic element. This stripe can be located along the. edge of the electrographic element, as illustrated herein, or it can be spaced inwardly from the edge at any desired location. Typically, it will be at the edge or close to the edge of the element. In certain instances it is desirable to provide two stripes, one adjacent each edge of the element, as also illustrated herein. In this case, the electrographic copying apparatus is, of course, provided with means for engaging each of the stripes.
• Perforations can be located within the region of one of the stripes, as illustrated herein, or they can be located outside the stripe region.
• An advantage of locating them within a stripe is that it is then possible for them to assist in providing electrical connection to the conductive layer. Whether one, or more than one stripe is used, each such stripe will be located in a non-recording portion of the electrographic element.
• an imbibable suspension comprising the electrically conductive particles and at least one organic solvent is applied to the surface of the element as an elongated stripe and, with the aid of the elongated groove, imbibed into contact with the conductive layer.
• the imbibable suspension advantageously contains a polymeric binder which will aid in bonding the conductive particles within the element and assist in providing a stripe which is durable and abrasion resistant.
• a polymeric binder which will aid in bonding the conductive particles within the element and assist in providing a stripe which is durable and abrasion resistant.
• Any suitable form of grounding or biasing member can be used to engage the conductive stripe, for example, the member can be a metal bristle brush, as illustrated herein, or a metal strip, or a metal roller.
• ground as used herein is relative and merely represents a relative potential to which other positive or negative potentials are referred.
• ground potential is arbitrarily assigned a value of zero volts.
• the electrically conductive particles which form the electrical connection means of this invention can be any finely-divided particles having good electrical conducting properties.
• Typical conductive particles include particles of graphite, carbon black, nickel, silver, aluminum, copper, tin, etc. and mixtures thereof.
• the size of these conductive particles can vary depending on the particular material used but generally ranges from about 0.001 ⁇ to about 100 ⁇ .
• Graphite has been found to be very satisfactory based on its property of being a good lubricant as well as conductor. When graphite is used, less wear is encountered in those non-recording regions of the element which are in contact with the metal grounding devices.
• a liquid dispersion of the electrically conductive particles in a solvent is applied to the surface of the electrographic element.
• the solvent should be one which is capable of impregnating (e.g., by swelling, cracking or dissolving) the polymeric binder contained in a photoconductive layer or other layer, such as a subbing layer, which is in direct contact with the electrically conductive layer, and preferably one which is capable of impregnating the binders in all layers overlying the electrically conductive layer.
• Suitable solvents having these characteristics include aliphatic alcohols having 1 to 8 carbon atoms such as methanol, ethanol, isopropanol, etc.
• ketones having 3 to 10 carbon atoms such as acetone, methylethyl ketone, etc.
• chlorinated alkanes having 1 to 8 carbon atoms such as methylene chloride, propylene chloride, chloroform, etc.
• Mixtures of these solvents may also be used.
• the particular solvent or mixture employed is somewhat dependent upon the polymer to be impregnated and the selection of the optimum solvent to be used is apparent to those skilled in the art.
• a particularly useful solvent which is capable of impregnating most of the more common hydrophobic film-forming resin binders employed in the various layers of electrographic elements comprises a mixture of a ketone such as acetone or methyl ethyl ketone with a chlorinated hydrocarbon such as methylene chloride or propylene chloride.
• the solvent and electrically conductive particles are thoroughly mixed, e.g., with a ball mill or blender, so as to create a uniform dispersion of the conductive particles in the solvent.
• a ball mill or blender in order to obtain a uniform stable dispersion of solids in liquid, it is necessary to employ a small amount of a polymeric binder.
• the added binder aids primarily in the creation of a more uniform dispersion.
• the weight ratio of conductive particles to binder ranges from 0.5 to 10 parts and preferably 1.5 to 2.5 parts of conductive particles for each part of binder.
• Enough solvent is added to bring the solids content to at least 5% and not more than 90% of the liquid dispersion.
• the binder used in the imbibable suspension can be any of a wide variety of polymers. Suitable polymers include styrene-butadiene copolymers; silicone resins; styrenealkyd resins; silicone-alkyd resins; soya-alkyd resins; poly(vinyl chloride); poly(vinylidene chloride); vinylidene chloride-acrylonitrile copolymers; poly(vinyl acetate); vinyl acetate-vinyl chloride copolymers; poly (vinyl acetals) such as poly(vinyl butyral); poly- acrylic and methacrylic esters, such as polyCmethylmethacrylate), poly (n-butylmethacrylate), poly(isobutyl methacrylate), etc.; polystyrene; nitrated polystyrene; polymethylstyrene; polyesters such as poly(ethylene terephthalate.); phenolformaldehyde resins
• the electrographic elements of this invention can be composed of only three layers, namely, an electrically conductive layer sandwiched between a support and a photoconductive layer. However, they may include two or more contiguously disposed photoconductive layers, each of which exhibits different characteristics , and may include a variety of other layers such as barrier layers, subbing layers, overcoat layers, and so forth.
• the various layers making up the element typically vary greatly in thickness.
• the support may have a thickness of 100 microns and the photoconductive layer a thickness of 20 microns while each of the electrically conductive layer, subbing layer and overcoat layer may have a thickness of less than one micron.
• the electrographic element is typically utilized in the form of a continuous belt but it may be employed in other configurations such as for example in the form of a flat sheet or in cylindrical form.
• the photoconductive layer in the electrographic element of this invention can be prepared from a wide variety of materials.
• this layer is prepared by dispersing a photoconductor in a resinous binder and coating the resultant dispersion on the electrically conductive layer or on a subbing layer overlying the electrically conductive layer.
• Binders useful for this purpose include the same polymers referred to above as being useful as binders in the imbibable suspension.
• Photoconductors suitable for use in the photoconductive layer include inorganic, organic and organo-metallic photoconductors.
• Typical photoconductors which are useful include zinc oxide, titanium dioxide, organic derivatives of Group l ⁇ a and Va metals such as those having at least one amino-aryl group attached to the metal atom, aryl amines, polyarylalkanes having at least one amino substituent, and the like.
• the use of organic photoconductors is preferred.
• Illustrative examples of organic photoconductors are those described in U.S. patents 3,139,338; 3,139,339; 3,140,946; 3,141,770; 3,148,982; 3,155,503; 3,257,202; 3,257,203; 3,257,204; 3,265,496; 3,265,497; 3,274,000; and 3,6l5,4l4.
• a sensitizer for the photoconductor may optionally be included in the photoconductive layer to change the electrophotosensitivity or spectral sensitivity of the element.
• Sensitizing compounds useful in the photoconductive layers described herein can be selected from a wide variety of materials, including such materials as pyryliums, including thiapyrylium and selenapyrylium dye salts, disclosed in U.S.
• Patent 3,250,615 fluorenes such as 7,12- dioxo-13-dibenzo(a,h)fluorene, 5,10-dioxo-4a,ll- diazabenzo(b)fluorene, 3,13 -dioxo- 7 -oxadibenzo- (b,g)fluorene, and the like; aromatic nitro compounds of the kinds described in U.S. Patent 2,610,120; anthrones like those disclosed in U.S. Patent 2,670,284; quinones, U.S. Patent 2,670,286; benzophenones U.S. Patent 2,670,287; thiazoles U.S.
• Patent 2,732,301 mineral acids; carboxylic acids, such as maleic acid, dichloroacetic acid, and salicylic acid; sulfonic and phosphoric acids; and various dyes, such as cyanine (including carbocyanine), mercocyanine diarylmethane, thiazine, azine, oxazine, xanthene, phthalein, acridine, azo, anthraquinone dyes and the like and mixtures thereof.
• the sensitizing dyes preferred for use with this invention are selected from pyrylium, selenapyrylium and thiapyrylium salts, and cyanines, including carbocyanine dyes.
• sensitizer is employed with the binder and organic photoconductor to form a sensitized electrographic layer
• Other methods of incorporating the sensitizer or the effect of the sensitizer may, however, be employed consistent with the practice of this invention.
• no sensitizing compound is required to give photoconductivity in the layers which contain the photoconductors, therefore, no sensitizer is required in a particular photoconductive layer.
• relatively minor amounts of sensitizer give substantial improvement in speed in such layers, use of a sensitizer is preferred.
• sensitizer that can be added to the photoconductive layer to give effective increases in speed can vary widely.
• concentration in any given case will vary with the specific photoconductor and sensitizing compound used.
• substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from 0.0001 to 30 percent by weignt based on the weight of the film-forming coating composition.
• a sensitizer. is added to the coating composition in an amount by weight from
• Solvents useful for preparing the photoconductive coating compositions include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; 2-butanone; chlorinated hydrocarbons such as methylene chloride, ethylene chloride, and the like; ethers, such as tetrahydrofuran and the like, or mixtures of such solvents can advantageously be employed in the practice of this invention.
• solvents useful results are obtained where the photoconductive substance is present in an amount equal to at least about 1 weight percent of the coating composition. The upper limit on the amount of photoconductor present can be widely varied in accordance with usual practice.
• the photoconductor be present in an amount ranging from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition.
• a preferred weight range for the photoconductor in the coating composition is from about 10 weight percent to about 60 weight percent.
• Coating thicknesses of the photoconductive layer(s) can vary widely. Normally, a wet coating thickness in the range of 0.01 to 2 millimeters is useful in the practice of this invention. A preferred range of coating thickness is from 0.02 to 0.2 millimeters before drying, although such thicknesses can vary widely depending on the particular application desired for the electrographic element. In the method of manufacturing this invention an elongated longitudinally disposed groove is formed in a non-recording portion of the electrographic element.
• This groove extends from an exterior surface of the element at least to a position proximate to the electrically conductive layer. It is formed with a depth and width adapted to promote the imbibition of the suspension of electrically- conducting particles into contact with the electrically conductive layer. The optimum depth and width will depend upon numerous circumstances including the structure and composition of the electrographic element and the imbibing characteristics of the suspension containing the electrically conductive particles. As explained hereinabove, the groove may terminate a short distance above the electrically conductive layer, may terminate at the surface of the electrically conductive layer, or may extend into, or through the electrically conductive layer, but may not penetrate through, the electrographic element. Typically, a groove with a width of from 0.2 millimeters to 5 millimeters is suitable.
• Imbibition of the suspension containing the electrically conductive particles causes it to spread laterally as well as to penetrate downwardly from the surface to which it is applied. Since the suspension is applied as a stripe which encompasses the groove, it flows into the groove and spreads laterally from the walls of the groove as well as penetrating downwardly from the bottom of the groove. Even though the distance it is capable of penetrating may be relatively small, since the groove extends to a position at least proximate to the conductive layer the resulting region of imbibed electrically conductive particles will easily extend into effective contact with the conductive layer and thereby provide an electrically conductive path from the conductive layer to the surface of the element.
• the groove can be formed in the electrographic element in any suitable manner.
• One technique which is suitable for forming the groove is the use of a revolving knife blade which is rotated at high speeds, such as speeds of several thousand revolutions per minute.
• the blade is preferably made of a very durable and wear resistant material, such as stainless steel. It may be a steel blade with a diamond edge.
• An alternative technique is to carry out a localized pyrolysis in which part of the electrographic element is vaporized in a controlled manner along the desired path. Methods of accomplishing this include the use of a laser beam or an electron beam. In forming the groove by use of a laser, the action of the laser beam serves to vaporize the material on which the beam is impinged and thereby generate a groove. Suitable lasers for this purpose are well known.
• Laser beams having wavelengths in the infrared range are generally satisfactory.
• a C0 2 laser is preferred because of its high efficiency characteristics.
• the width of the laser beam will be selected in accordance with the desired width of the groove.
• the laser beam can be moved relative to a stationary substrate to form the groove but it will usually be more convenient for the laser beam to be fixed in position and the substrate moved at an appropriate rate to form a groove of the desired depth.
• the imbibable dispersion containing the electrically conductive particles is applied to the surface of the element as an elongated stripe which encompasses the groove.
• the stripe may be of any suitable width, with the width ordinarily being commensurate with the size of the grounding or biasing member in the electrographic apparatus which is intended to engage the stripe.
• the stripe will have a width of about 5 to about 25 millimeters and it will typically be about 5 to about 100 times as wide as the groove.
• the groove will usually be located at or near the midpoint of the stripe but it may be at any position within the stripe, as desired.
• the imbibable dispersion to the surface of the electrographic element can be carried out in any suitable manner. For example, it can be carried out by spraying or by the use of a coating hopper such as a hopper of the extrusion type.
• the imbibable dispersion flows into the groove and penetrates into the material surrounding the groove. If the groove does not extend all the way through, the photoconductive layer, the com position will be imbibed through the material which lies between the bottom of the groove and the electrically conductive layer. It will also spread laterally from the walls of the groove by the process of imbibition into the photoconductive layer and into any subbing layer overlying the electrically conductive layer.
• the Imbibable suspension is applied in an amount sufficient to provide effective contact of the electrically conductive particles with the electrically conductive layer.
• the optimum amount to be used will depend on the characteristics of both the imbibable suspension and the electrographic element, as well as the method of application of the suspension.
• the amount used can be sufficient to completely fill the groove and provide a level surface thereover. However, lesser amounts can also be used. In any event, the result will be that the groove will be at least partially filled with the electrically conductive particles.
• the method of this invention is a simple, effective and reliable procedure which is well adapted to use in a high volume production operation.
• the steps of forming the groove and applying the imbibable suspension can be carried out as independent operations or as sequential steps in a single continuous process. If carried out independently, they can, of course, be conducted at different speeds with the speed chosen for each step being optimum for that particular operation.
• the speed at which the web is advanced can be selected within a broad range, for example, a speed in the range of from 5 to 200 centimeters per second.
• the steps of forming the groove and and applying the imbibable suspension can also be carried out as part of a continuous process which involves other operations such as coating of the various layers on the support, forming the per forations, slitting, and so forth.
• the imbibable suspension After application of the imbibable suspension, it is preferred to impinge air or other gaseous medium on the element and/or to heat the element in order to drive off the solvent. Heating also serves to promote the penetrating action of the imbibable suspension and thereby facilitate good contact with the electrically conductive layer.
• the imbibable suspension preferably contains a polymeric binder. The binder promotes the bonding of the electrically conductive particles within the element and assists in forming a stripe which is durable and abrasion resistant.
• the electrographic element can be re-used a great many times while still maintaining excellent electrical contact with the grounding or biasing member.
• electrographic element 2 is unwound from supply roll 30 which is mounted for rotation about its axis on a suitable framework (not shown) and passes around guide rollers 32 and 34, which maintain it under proper tension, and over backing roll 36.
• an exhaust duct 42 connected to a vacuum source is positioned closely adjacent to.
• FIG. 8 illustrates an alternative embodiment of the method of this invention in which the groove is formed in the electrographic element by the use of a rotating knife blade. In this method, electrographic element 2 is unwound from supply roll 30 and passes around guide rollers 32 and 34 and over backing roll 36.
• a rotatable knife blade 48 driven by a suitable drive means 50, such as a variable-speed motor, engages the surface of electrographic element 2 as it passes over backing roll 36 and thereby forms a groove 20.
• a suitable drive means 50 such as a variable-speed motor
• exhaust duct 42 is positioned closely adjacent to the region where cutting takes place.
• the advancing element passes under spray nozzle 44, which directs liquid spray 46 onto its surface and thereby forms stripe 19 encompassing groove 20, and then passes through the drying chamber in which warm air impinges on the stripe.
• the web can be wound onto a . take-up roll after the stripe has been dried or it can be cut to appropriate lengths, each of which will serve to form an endless belt for use in an eiectrographic copying apparatus, or it can be subjected to additional operations such as slitting.
• the groove in the electrographic element it is ordinarily desirable that it be made as narrow as possible since this will involve the minimum removal of material and therefor the minimum formation of vapors or dust. It must, of course, be made wide enough to enable the imbibable suspension to enter the groove.
• the most appropriate width for the groove may be determined, at least in part, by the choice of method used to form the groove; for example, it may be determined by the minimum practical thickness for knife blades used in forming the groove by a cutting process. As previously indicated, there is a wide degree of choice in regard to the depth of the groove.
• the groove can be readily cut to a desired depth by, for example, varying the pressure applied to a rotating knife blade or varying the power output from a laser.
• the groove does not have to be cut to an exact predetermined depth and does not have to be of exactly the same depth at all points along its longitudinal extent. Since the imbibable suspension is capable of penetrating a substantial distance into the photoconductive layer, or other layer of the electrographic element, it is only necessary that the groove extend to a position at least proximate to the electrically-conductive layer, that is, to a position that is not so far away that the imbibable suspension will not be able to reach the electrically-conductive layer. It should be noted that while mechanical methods of cutting the groove, such as a rotating knife blade, result in the generation of dust, the use of a laser beam brings about a vaporization of the solid materials.
• the laser it may be necessary to control the laser such that it cuts a groove which reaches or at least very nearly reaches the electrically conductive layer or which extends into the electrically conductive layer or completely through it
• the electrically conductive layer is exposed by removing all overlying material this provides for contact between the electrically conductive particles and the electrically conductive layer at the bottom of the groove.
• the groove cuts into or through the electrically conductive layer, there is opportunity for contact between the electrically conductive particles and the edges of the electrically conductive layer within the groove. In either instance, contact between the electrically conductive particles and the electrically conductive layer is also provided as a result of the lateral spreading of the imbibable suspension.
• the lateral spreading action which occurs is an important feature of the present invention since it provides much more effective contact with the electrically conductive layer than is achieved merely as a result of contact at the bottom of a groove which exposes the electrically conductive layer.
• Use of an electrically conductive composition which is not capable of imbibition would, of course, not provide the lateral spreading action and thereby would give much less effective contact.
• the combined use of a grooye and an imbibable suspension in accordance with this invention is useful with electrographic elements of many different structural variations.
• the method of this invention is applicable in any situation where there is an inaccessible electrically conductive layer sandwiched between other layers of an electrographic element.
• Electrographic elements containing the novel electrical connection means of this invention are useful in the xerographic process.
• the electrographic element while held in the dark, is given a blanket electrostatic charge by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer.
• the electrically conducting layer is maintained at ground potential by electrically connecting the conductive stripe on the electrographic element to ground. In the absence of grounding in this manner, the difference in potential between the photoconductive layer and the conducting layer is not large enough to produce a suitable latent image.
• the charge is retained on the surface of the photoconductive layer because of the substantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark.
• the electrical connection means permits exceptionally good contact to be made between the conducting layer and the grounding means while the element is in motion.
• the electrostatic charge formed on the surface of the photoconductiye layer is then selectively dissipated from the surface of the layer by imagewise exposure to light by means of a conventional exposure operation such as for example, by a contact-printing technique, or by lens projection of an image, or by reflex techniques and the like, to thereby form a latent image in the photoconductive layer.
• Exposing the surface in this manner forms a pattern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the intensity of the illumination in a particular area.
• the charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charged or uncharged areas are rendered visible, by treatment with a medium comprising electrostatically responsible particles having optical density.
• a medium comprising electrostatically responsible particles having optical density.
• Liquid development of the latent electrostatic image may also be used. It is frequently necessary during development to maintain the electrically-conducting layer at a given potential in order to obtain a clean background.
• the electrical connection means provided in the elements of this invention enables one to easily maintain the potential of the electrically-conducting layer at a preselected level.
• an electrographic element comprised of a poly(ethylene terephthalate) support with a thickness of 100 microns, a nickel layer with a thickness of less than 1 micron overlying the support, and a photoconductive layer, comprised of an organic photoconductor dispersed in a polycarbonate binder and having a thickness of approximately 20 microns, overlying the nickel layer, is grooved by the use of a rotating knife blade and then spray coated to form the desired conductive stripe.
• the groove is formed with, a width of approximately 1 millimeter and a depth of approximately 15 microns and is cut by a rotating stainless steel knife blade driven by a motor at a speed of 6000 revolutions per minute while the electrographic element is advanced at a speed of 30 centimeters per second.
• a stripe with a width of 10 millimeters, which encompasses the groove is applied by spraying the following imbibable suspension onto the surface of the element:
• the solvent is removed by contacting the element with warm air at a temperature of about 165°F.
• the electrographic element described above is grooved by the use of a laser beam and then coated with an imbibable suspension to form the desired conductive stripe.
• a suitable laser for this purpose is a 50-watt C0 2 laser equipped with a 2.5 inch focal length lens.
• the groove can be formed along only one edge of the element or, by equipping the laser with two lenses and a beam splitter, grooves can be simultaneously formed along both edges.
• the element can be advanced at any suitable speed during the step of forming the grooves with a laser beam, such as a speed of 30 centimeters per second.
• the power output from the laser is regulated so that the groove is cut completely through the nickel layer of the element described above and into the polyCethylene terephthalate) support.
• an imbibable suspension as described above, is applied in the form of a stripe which encompasses the groove by a suitable method of application such as spraying or hopper coating .

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Discharging, Photosensitive Material Shape In Electrophotography (AREA)
• Photoreceptors In Electrophotography (AREA)

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• 1978
  • 1978-12-29 CA CA318,840A patent/CA1115334A/en not_active Expired
• 1979
  • 1979-06-21 JP JP50103479A patent/JPS55500394A/ja active Pending
  • 1979-06-21 WO PCT/US1979/000439 patent/WO1980000195A1/en unknown
• 1980
  • 1980-02-01 EP EP79900809A patent/EP0016110A1/en not_active Withdrawn

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