US3472657A - Xerographic development method and apparatus - Google Patents

Xerographic development method and apparatus Download PDF

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Publication number
US3472657A
US3472657A US452098A US3472657DA US3472657A US 3472657 A US3472657 A US 3472657A US 452098 A US452098 A US 452098A US 3472657D A US3472657D A US 3472657DA US 3472657 A US3472657 A US 3472657A
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United States
Prior art keywords
image
developer
support
development
drum
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Expired - Lifetime
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US452098A
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English (en)
Inventor
Edward F Mayer
William A Sullivan Jr
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Xerox Corp
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Xerox Corp
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    • 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
    • G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0105—Details of unit
    • G03G15/0126—Details of unit using a solid developer
    • 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0801—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer for cascading

Definitions

  • a toner deposit is formed by forming an electrostatic charge on a surface and thereafter flowing spaced apart from the surface but within the effective field of the electrostatic charge a two-component developer mix comprising electroscopic developer particles carried by granular carrier particles.
  • This invention relates to xcrography and particularly to improved method and apparatus for development of electrostatic charge patterns.
  • a xerographic plate comprising a layer of photoconductive insulating material on a conductive backing is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the radiation intensity that reaches them, and thereby creates an electrostatic latent image on or in the photoconductive layer. Development of the latent image is effected with an electrostatically charged, finely divided material such as an electroscopic powder that is brought into surface contact with the photoconductive layer and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed xerographic powder image is usually transferred to a support surface to which it may be fixed by any suitable means.
  • the first of the properties is that of deposition in which the toner is attracted, as intended, to the superior electrostatic field emanating from the image charge pattern.
  • unwanted spurious toner deposit occurs in a statistical pattern as a result of toner insufficiently charged to be retained by their carrier.
  • the latter deposits randomly about the surface of the xerographic plate relatively independent of the plate fields as by Van der Waals forces. Still other deposits occur by the weakly held toner being attracted to the residual plate charges corresponding to the non-image or background areas of the pattern being reproduced.
  • FIG. 1 schematically illustrates an automatic drum type xerographic apparatus employing the developing system hereof;
  • FIG. 2 schematically illustrates an automatic flexible plate xerographic apparatus employing the development system hereof;
  • FIG. 3 is a schematic variation of FIG. 2 as adapted for two color development
  • FIG. 4 is a side elevation of a manually operable apparatus for developing fiat xerographic plates in accordance herewith;
  • FIG. 5 is a schematic apparatus for an out-of-contact belt system loaded in accordance herewith.
  • FIG. 6 is a schematic apparatus for a touchdown development loaded with developer in accordance herewith.
  • FIG. 1 For a general understanding of the xerographic processing system in which the invention is incorporated, reference is had to FIG. 1 in which the various components are schematically illustrated.
  • a radiation light image of copy to be reproduced is projected onto the sensitized surface of a xerographic plate to form an electrostatic latent image thereon.
  • the latent image is usually developed with an oppositely charged developing material to form a xerographic powder image, corresponding to the latent image on the plate surface.
  • the powder image is then electrostatically transferred to a support surface to which it may be fused by any suitable form of fusing device whereby the powder image is caused permanently to adhere to the support surface.
  • the xerographic apparatus described herein typically may be of a type disclosed in patent, US. 3,076,392, in which copy to be reproduced is placed on a support tray 10 from which it is fed onto a transport mechanism generally designated as 11. Suitable drive means are provided for the transport mechanism from motor 12 to endless belts 13 whereby the copy is moved past the optical axis of projection lens system 14 that is illuminated by a projection lamp LMP-l. The image of the copy is reflected by a mirror 15 through an adjustable objective lens 16 and then reflected by a mirror 17 downwardly through a variable slit aperture assembly 18 and onto the surface of a xerographic plate in the form of drum 19.
  • Xerographic drum 19 includes a cylindrical member mounted in suitable hearings in the frame of the machine and is driven in a clockwise direction by a motor 24 at a constant rate that is proportional to the transport rate of the copy, whereby the peripheral rate of the drum surface is identical to the rate of movement of the reflected light image.
  • the drum surface comprises a layer of photocon ductive material on a conductive backing that is sensitized to a potential of about 300l,000 volts prior to exposure by means of a corona generating device 25, which may be an adaptation of the type disclosed in patent, US. 2,836,- 725, and which is energized from a suitable high potential source.
  • the photoconductive surface is overcoated with an adhesive transparent material, such as Teflon, which facilitates transfer of the developed image and eases subsequent cleaning of the surface before recycling.
  • the exposure of the drum to the light image discharges the photoconductive layer in the areas struck by light, whereby there remains on the drum a latent electrostatic image in image configuration corresponding to the light image projected from the copy,
  • the electrostatic latent image passes through a developing station 26 at which a two-component developing material 27 of a type described above and as will be further described below is cascaded juxtaposed and out of contact with the plate surface to effect development of the image thereon.
  • the powder image passes through an image transfer station 42 at which the powder image is electrostatically transferred to a support surface web 43 by means of a second corona generating device 44 similar to corona charging device 25 mentioned above.
  • the support surface to which the powder image is transferred may be of any convenient type, such as paper, and is obtained from a supply roll 45 and is fed over guide rolls 46 and 47 and over suitable tensioning rolls being directed into surface contact with the drum in the immediate vicinity of transfer corona generating device 44. After transfer, the support surface is separated from the drum surface and guided through a suitable fusing apparatus 48 whereby the powder image is permanently aflixed thereto. Thereafter, the support surface is fed over a further system of guide and tensioning rolls and onto a take up roll 52 that is driven by motor 53.
  • the xerographic drum surface passes through a cleaning station 55 at which the surface is brushed by a cleaning brush assembly 56 rotated by a motor 57 whereby residual developing material remaining on the drum is removed. Thereafter, the drum surface passes through a discharge station 58 at which it is illuminated by a fluorescent lamp LMP2 whereby the drum surface in this region is completely flooded with light to remove any electrostatic charge that may remain thereon. Suitable light traps are provided in the system to prevent any light rays from reaching the drum surface, other than a projected image, during the period of drum travel immediately prior to sensitization by corona generating device 25 until after the drum surface is completely passed through the developing station 26.
  • Development in accordance with the invention hereof is effected by means of an apparatus 60 comprising a housing 61 and including a continuously operative offset conveyor 62 being driven by a motor 63.
  • the two-component developer material 27 is contained in the sump of the housing and is carried up by the conveyor for release onto an inclined chute 64.
  • the developer cascades downwardly in a direction towards the surface of drum 19 until striking the forward upper dependent wall 65 of the housing.
  • the wall interception deflects the developer flow in order to effect its cascade onto a support member 66 extending from about a four oclock drum position generally radially parallel and curvilinear to the circumference of the rotating drum 19.
  • Toner component 28 of the developer consumed in developing is stored in dispenser 58 and is controllably released by means of gate 59.
  • Support 66 can comprise any suitable material having sufficient durability and rigidity for uniformly maintaining the close spacing tolerances to the drum periphery during continuous operation and including electrically insulating as well as electrically conductive materials.
  • support 66 comprises an electrode member which is effective to enhance the development field of the image pattern as is associated with solid areas in order to obtain maximum benefits from the development techniques hereof.
  • the electrode support member is electrically biased relative to drum 19 by means of a potential source 67 from about the magnitude of the background potential on the drum surface up to about 200 volts.
  • a potential source 67 from about the magnitude of the background potential on the drum surface up to about 200 volts.
  • approximately three inches of curved electrode is about adequate for peripheral drum speeds of up to about 6 inches per second.
  • an opposite hand developing apparatus 68 as shown dashed can be employed to extend the development zone to about the eight oclock position.
  • the developer employed can comprise basic carrier beads of about 2.2 specific gravity and toner compositions both known in the art as for example, described above and as further described in patent, U.S. Reissue 25,136.
  • the carrier beads for use herein in contrast to about a 750 micron dimension in the prior art, preferably has a size range of approximately 100-300 microns generally about 250 microns and spherical as to provide substantially increased surface area of the carrier particles.
  • the toner concentration is preferably about 6-10 percent by weight usually about 8, as opposed to approximately 1% percent by weight in the prior art.
  • the higher toner concentration coupled with the small carrier dimension and higher density provides increased carrier surface area and a low average charge per toner particle to be easily attracted to the image charges.
  • carrier beads of about 4-5 specific gravity By employing carrier beads of about 4-5 specific gravity, improved mechanical flow action can be realized.
  • the latter will, of course, reflect a lower concentration of toner by weight to generally about 1 to 5% with about /2 to 2% deemed optimum. Since the carrier beads are maintained separated from the image drum surface, scavenging is non-existent and deposited toner is retained by the electrostatic image forces Which need only be adequate to attract the powder without regard to retaining it in subsequent competition with the carrier as was inherent in the prior art. This is particularly true as associated with the central image portions of solid area.
  • the apparatus embodiment hereof differs from that of the previous embodiment in that the xerographic plate comprises an endless flexible belt 70 such as vitreous selenium on a conductive flexible substrate.
  • the belt is continuously advanced over guide rolls by means of a motor 71 and is uniformly charged in the course of its movement by means of corona generator 25.
  • a copy sheet is supported at plane 72 and is exposed to the charged belt surface by means of objective lens 73 upon being illuminated by means of a pair of flash lamps 74 and 75.
  • developing apparatus 78 which is similar to apparatus 60 above, but having a straight developer support 66 extending parallel to the moving path of plate 70 at about 20 to 90 degrees to the horizontal and usually about 30 to 70 degrees.
  • the support provides extended electrode surface for extending the eifective development zone.
  • the apparatus can be adapted to accommodate belt speeds up to approximately 40 inches per second and above.
  • a desired electrode length is to a large degree a function of belt speed, developer flow as well as toner concentration.
  • the duplex unit shown is highly beneficial in minimizing directional effects from the developer flow.
  • the developed image is then transferred from the belt as it passes over guide roll 76 to transfer web 43 by means of corona generator 44 similarly as above.
  • the surface of the belt is cleaned before being recycled via a soft cotton web 79 passing counterdirectional to the belt over guide 82 in contact therewith from a supply roll 80 to a takeup roll 81 being driven by motor 83.
  • the development system of the invention is adapted for a two-color reproduction.
  • the belt 70 is first charged by corona generator 25 and then exposed to an original such as a separation original supported at exposure plane 72.
  • the image charge is then developed in a first color by a developing unit 111 containing a two-component developer with toner of the appropriate reproduction color.
  • belt 70 With a first developed image on its surface belt 70 is recharged by a second corona generator 112 and then reexposed through lens 114 to a second original supported at exposure plane 113.
  • the charge pattern formed by the second exposure is then developed in developing unit 115 containing a two-component developer with toner of the appropriate reproduction color differing from that in unit 111.
  • the belt is processed similarly as described in FIG. '2 above to result in transfer of a two-color reproduction onto support 43.
  • Suitable mechanisms or electric circuitry can be incorporated to ensure optical registration between the different exposures onto belt 70 as to result in a single composite reproduction on support 43.
  • FIG. 4 there is illustrated apparatus adapted to carry out the development method hereof particularly suitable for flat xerographic plates which have been remotely processed for forming the image charge pattern.
  • the apparatus is comprised of a horizontal tray 87 having opposite end pockets 88 and 89 formed therein for containing developer during its inactivity and to contain the developer passing from the opposite pocket during operation.
  • spring clasps 90 and 91 On the inside terminal lips of the pockets there is attached spring clasps 90 and 91 by which a Xerographic plate 86 is received and secured image side down uniformly spaced and parallel to bottom tray wall 92.
  • On the underside of bottom wall 92 there is secured a downward depending boss 93 axially drilled and mounted on pin 94 in stand 95.
  • End stops 96 and 97 each include adjustable posts 98 that are secured to limit the oscillatory travel of the tray in either direction.
  • 20 to 90 degrees is regarded as about the limiting range of angular displacement for cascading the developer out of contact with the plate surface.
  • About 3070 degrees is usually adequate and optimum and about 2 to 4 passes of developer will produce the high quality development expected of the technique hereof.
  • FIG. 5 there is illustrated an apparatus wherein the development system hereof, rather than for direct image development, is employed for loading the surface of an endless donor belt that is continuously advanced by means of a motor 106.
  • the belt surface receives a uniform application of electrostatic charge from a corona generator 107 before passing vertically inclined downwardly and in closely spaced relationship to the cascading developer material which deposits a uniform layer of toner material thereon.
  • the belt surface containing a uniform coating of toner particles on its exterior surface passes upwardly approaching a tangential spacing with the pattern bearing surface of rotating drum 19. Spacing between belt 105 and the drum is maintained by means of guide rolls 109 and 110 as not to exceed between approximately .003 to .05 inch at the closest point.
  • a vibrator 108 Secured behind the belt at the point closest to the drum surface is a vibrator 108 which can be actuated mechanically, electromechanically, piezoelectrically or acoustically.
  • the vibrator effects an oscillatory motion on the belt surface to dislodge toner thereon and produce a reduction of mechanical Van der Waal forces permitting the image field to more easily attract the toner across the gap to the image pattern on the drum surface and effect development thereof.
  • Potential source 116 maintains a positive bias on xerographic drum 19 for suppression of background potential as before.
  • belt 105 is operatively advanced in continuous contact with the surface of drum 19 in a manner disclosed in Mayo patent, US. 2,895,847. Uniform load ing of belt 105 is achieved in accordance with invention hereof by developer unit 78 which is effective for rapidly loading the belt surface with a uniform coating of toner particles.
  • a process for applying electroscopic powder particles onto an insulating support comprising the steps of:
  • a process for applying electroscopic powder particles in at least two colors onto an insulating support comprising the steps of:
  • Apparatus for depositing electroscopic developer particles on an electrostatic charge pattern comprising in combination:
  • a second support means to support a quantity of two component developer mix including electroscopic developer particles on granular carrier particles, said second support means being arranged extending uniformly opposite said surface of said insulating member and spaced apart therefrom a predetermined distance to support said developer mix out of contact with said surface within the effective field of said charge pattern thereon;
  • (c) means arranged to effect a gravity cascade flow of said developer mix on said second support whereby electroscopic developer particles of said developer mix are attracted to said charge pattern on said surface of said insulating member.
  • Apparatus according to claim 8 in which the supporting surface of said electrode is positioned subjacent and substantially parallel to said insulating member.
  • Apparatus according to claim 10 in which the charge pattern comprises an image pattern to be reproduced.
  • Apparatus for uniformly depositing electroscopic developer particles on a substantially uniformly charged surface comprising in combination:
  • second support means to support a quantity of two component developer mix including electroscopic developer particles on granular carrier particles, said second support means being arranged uniformly opposite said surface of said member and spaced apart therefrom a predetermined distance to support said developer mix out of contact with said surface and within the effective field of said uniform electrostatic charge thereon;
  • a xerograp 1c repro uc ion appara us 1116 u mg a xerographic plate and means to form an image charge g pattern on a surface of said plate of an original to be 291O963 11/1959 reproduced, a developing apparatus for developing said 2927554 3/1960 i 96 1 X charge pattern comprising in combination: 3O60020 10/1962 Gr i 00m 12 (a) container means to contain a supply of two-com- 3084043 4/1963 G '1 ponent developer mix including electroscopic de- 3146688 9/1964 ac ark et a1.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Color Electrophotography (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Dry Development In Electrophotography (AREA)
US452098A 1965-04-30 1965-04-30 Xerographic development method and apparatus Expired - Lifetime US3472657A (en)

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US45209865A 1965-04-30 1965-04-30

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BE (1) BE680374A (en(2012))
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GB (1) GB1141167A (en(2012))
NL (1) NL6605862A (en(2012))
SE (1) SE330833B (en(2012))

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3611992A (en) * 1969-07-03 1971-10-12 Xerox Corp Cleanup electrode
US3638610A (en) * 1969-07-03 1972-02-01 Xerox Corp Development apparatus
US3649262A (en) * 1968-12-31 1972-03-14 Xerox Corp Simultaneous development-cleaning of the same area of an electrostatographic image support surface
US3663291A (en) * 1969-10-14 1972-05-16 Xerox Corp Cascade development
US3670700A (en) * 1969-07-03 1972-06-20 Xerox Corp Development electrode
US3696784A (en) * 1970-12-15 1972-10-10 Xerox Corp Xerographic development apparatus
US3778144A (en) * 1971-08-18 1973-12-11 Xerox Corp Xerographic development electrode apparatus
US3948493A (en) * 1972-06-30 1976-04-06 Hoechst Aktiengesellschaft Process for conveying a developer mixture
US3984856A (en) * 1972-07-29 1976-10-05 Hoechst Aktiengesellschaft Process and apparatus for developing diazotype material
US4527509A (en) * 1984-05-10 1985-07-09 Gaf Corporation Dielectric film processor
US4600290A (en) * 1984-03-26 1986-07-15 Ricoh Co., Ltd. Magnetic brush/stationary electrode development system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2924912A1 (de) * 1978-06-22 1980-01-10 Coulter Systems Corp Verfahren und vorrichtung zum elektrostatischen bedrucken eines ausgedehnten traegers mit zusammengesetzten farbbildern

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2842456A (en) * 1955-08-30 1958-07-08 Battelle Development Corp Process for developing an electrostatic image
US2877132A (en) * 1955-02-18 1959-03-10 Haloid Xerox Inc Method for development of electrostatic images
US2910963A (en) * 1956-07-25 1959-11-03 Rca Corp Apparatus for developing an electrostatic image
US2927554A (en) * 1957-09-23 1960-03-08 Ibm Cascade developing apparatus
US3060020A (en) * 1958-03-20 1962-10-23 Rca Corp Method of electrophotographically producing a multicolor image
US3084043A (en) * 1959-05-07 1963-04-02 Xerox Corp Liquid development of electrostatic latent images
US3146688A (en) * 1961-05-01 1964-09-01 Xerox Corp Xerographic machine
US3232190A (en) * 1963-06-28 1966-02-01 Ibm Method and apparatus for copying
US3257223A (en) * 1962-11-01 1966-06-21 Xerox Corp Electrostatic powder cloud xerographic development method and apparatus

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2877132A (en) * 1955-02-18 1959-03-10 Haloid Xerox Inc Method for development of electrostatic images
US2842456A (en) * 1955-08-30 1958-07-08 Battelle Development Corp Process for developing an electrostatic image
US2910963A (en) * 1956-07-25 1959-11-03 Rca Corp Apparatus for developing an electrostatic image
US2927554A (en) * 1957-09-23 1960-03-08 Ibm Cascade developing apparatus
US3060020A (en) * 1958-03-20 1962-10-23 Rca Corp Method of electrophotographically producing a multicolor image
US3084043A (en) * 1959-05-07 1963-04-02 Xerox Corp Liquid development of electrostatic latent images
US3146688A (en) * 1961-05-01 1964-09-01 Xerox Corp Xerographic machine
US3257223A (en) * 1962-11-01 1966-06-21 Xerox Corp Electrostatic powder cloud xerographic development method and apparatus
US3232190A (en) * 1963-06-28 1966-02-01 Ibm Method and apparatus for copying

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3649262A (en) * 1968-12-31 1972-03-14 Xerox Corp Simultaneous development-cleaning of the same area of an electrostatographic image support surface
US3611992A (en) * 1969-07-03 1971-10-12 Xerox Corp Cleanup electrode
US3638610A (en) * 1969-07-03 1972-02-01 Xerox Corp Development apparatus
US3670700A (en) * 1969-07-03 1972-06-20 Xerox Corp Development electrode
US3663291A (en) * 1969-10-14 1972-05-16 Xerox Corp Cascade development
US3696784A (en) * 1970-12-15 1972-10-10 Xerox Corp Xerographic development apparatus
US3778144A (en) * 1971-08-18 1973-12-11 Xerox Corp Xerographic development electrode apparatus
US3948493A (en) * 1972-06-30 1976-04-06 Hoechst Aktiengesellschaft Process for conveying a developer mixture
US3984856A (en) * 1972-07-29 1976-10-05 Hoechst Aktiengesellschaft Process and apparatus for developing diazotype material
US4600290A (en) * 1984-03-26 1986-07-15 Ricoh Co., Ltd. Magnetic brush/stationary electrode development system
US4527509A (en) * 1984-05-10 1985-07-09 Gaf Corporation Dielectric film processor

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DE1522693A1 (de) 1969-10-30
GB1141167A (en) 1969-01-29
NL6605862A (en(2012)) 1966-10-31
BE680374A (en(2012)) 1966-10-03
SE330833B (en(2012)) 1970-11-30

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