US3599605A - Self-biasing development electrode for electrophotography - Google Patents

Self-biasing development electrode for electrophotography Download PDF

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Publication number
US3599605A
US3599605A US808823A US3599605DA US3599605A US 3599605 A US3599605 A US 3599605A US 808823 A US808823 A US 808823A US 3599605D A US3599605D A US 3599605DA US 3599605 A US3599605 A US 3599605A
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United States
Prior art keywords
image
electrode
resistor
development
potential
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Expired - Lifetime
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US808823A
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English (en)
Inventor
James C Ralston
Robert T Ritchie
Bernard G Thompson
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International Business Machines Corp
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International Business Machines 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/065—Arrangements for controlling the potential of the developing electrode

Definitions

  • Electrophotography using photoconductive insulating layers by which an electrostatic image is formed has become embodied in a number of high speed copying processes.
  • the photoconductive insulating layer is backed by a conductive layer and can be formed in the shape of a cylinder which is rotated to bring the photoconductive surface to a number of stations involved in the electrophotographic process.
  • An elec trical potential is first applied across the photoconductive insulating layer.
  • the charged photoconductive layer is then exposed imagewise to light and the electrical potential decays in the surface areas which are struck by light.
  • the dark areas on the projected image retain their electrostatic charge and the image is then developed by exposing the surface of the photoconductive layer to small'colored particles known as toner particles which have the desired charge relative to that of the image.
  • the charged toner particles are attracted to the charged image areas of :the photoconductor surface and thereby develop the electrostatic image.
  • the image can then be transferred from the photoconductive surface to a copy sheet.
  • a number of ways are conventionally employed to develop the electrostatic image such as cascade development described, for example, in U.S. Pat. No. 2,618,552; powder cloud development described, for example, in U.S. Pat. No. 2,22 1,776; magnetic brush development described, for example, in U.S. Pat. No. 2,874,963 and liquid development.
  • a development electrode in an apparatus for developing a latent electrostatic image on a charged member employing a development electrode in close proximity to the surface of the member being developed and having means for contacting the image with electroscopic-marking particles an improvement which comprises impedance means connected to the electrode to absorb a portion of the charge induced on the electrode by the image to thereby bias the electrode to an average potential which is somewhat greater in magnitude than the background potential of the image on the member.
  • FIG. 1, 11 represents a drum mounted for rotation which has on its surface a photoconductive insulating layer 13 such as, for example, vitreous selenium or a mixture of a polyvinyl carbazole and a Lewis acid beneath which is an electrically conductive layer 15.
  • a latent electrostatic image is formed on the photoconductor, for example by charging the photoconductor with a corona discharge unit and then discharging portions of the photoconductor, for example, by exposing the photoconductor imagewise to electromagnetic radiation.
  • the photoconductor surface is then rotated to developer station 17 where the surface is contacted by charged, electroscopic, finely divided marking particles which usually comprise, as is well known in the art, a heat softenable resin binder material, for example, a natural, or a synthetic organic polymer such as styrene polymers and copolymers, epoxy resins, rosin, rosin esters, and various combinations thereof mixed with coloring matter, for example carbon black so that a colored image can be easily fused onto a copy sheet.
  • a heat softenable resin binder material for example, a natural, or a synthetic organic polymer such as styrene polymers and copolymers, epoxy resins, rosin, rosin esters, and various combinations thereof mixed with coloring matter, for example carbon black so that a colored image can be easily fused onto a copy sheet.
  • the developer station 17 can be any convenient developer means such as, for example, a cascade developer unit, powder cloud developer unit or a magnetic brush developer unit.
  • the station illustrated at 17 is a magnetic brush developer unit in which a steel cylinder 19 is mounted for rotation on shaft 21 and adapted to be driven by a drive means (not shown). Inside the steel cylinder are a series of permanent magnets 18 which are arranged along the axis of the cylinder.
  • the developer mix utilized in magnetic brush development contains, in addition to the toner particles, carrier particles which are ferromagnetic and probably conductive, for example, iron or steelshot.
  • the particles can be coated with a resin to give the carrier the correct triboelectric properties such as is described, for example, in U.S. Pat. No. 2,618,551 so that the toner particles will assume the desired charge relative to that of the image areas and adhere to the carrier particles by electrostatic forces.
  • the carrier particles are held by magnetic attraction to the surface of the cylinder 19 in the form of brushlike tendrils 23 of carrier and toner.
  • Bucket conveyor 31 carries a fresh supply of toner and carrier to cylinder 19 so that the tendrils which have contacted the surface of the photoconductor and has become depleted in toner are continuously replenished with toner particles.
  • the surface of the cylinder 19 in closest proximity to the surface of photoconductive layer 13, acts as a conductive development electrode.
  • the charge on the photoconductor passing by the development station 17 induces a charge on the cylinder 19.
  • the magnitude of this induced charge is sufficient so that if cylinder 19 is allowed to float," i.e.
  • the charge will build up to the point where sufficient toner particles will not be attracted away from the carrier and cylinder 19 to the electrostatic image on the surface of the photoconductor and the image will be underdeveloped
  • the development electrode effect will not only enhance development of the image areas but will also increase the field over the background areas so that these areas attract toner away from the carrier and develop the background areas of the image.
  • cylinder 19 is grounded through an electrical impedance circuit in this instance comprising wire 34 and resistor 35.
  • a movable wiper 36 enables adjustment of the impedance where desired to obtain development of various types of image information.
  • This circuit retards the flow of charge from cylinder 19 and has the effect of maintaining the cylinder at a potential above ground during the time that an electrostatic image is being developed but allows a portion of the charge to bleed off so that cylinder 19 is at a potential less than the potential that would accumulate on cylinder 19 if it was allowed to float.
  • the resistance is chosen to provide the potential necessary to give the desired background suppression. The size of the resistance used depends upon the potential on the photoconductor and can be easily determined empirically by those skilled in the art.
  • the apparatus was utilized to produce and develop latent electrostatic images on the surface of photoconductor layer 13 which comprised both line copy and continuous tones and mixtures thereof with the resistance being varied from infinity to ground.
  • the resistance was at infinity (electrode floating)
  • a negative potential of about 700-750 volts was measured on the development electrode and almost no image could be developed on the photoconductor by the toner particles.
  • the electrode was grounded by removing the resistance, the image was fully developed but the background area was very dark.
  • resistances varying from about IXIO IOXIO" ohms the induced voltages measured on the development electrode are shown in table I-.
  • the variation in voltage due to the variation in the amount of charged image passing by cylinder 41 was reduced by the capacitor which dampened the sharp peaks observed when the resistor was used alone.
  • the overall variation in the voltage was reduced to about volts for the same master image which produced about a 200 volt variation using a resistor alone.
  • a capacitor 45 of 0.0l microfarad in parallel with a resistor 43 of 6.0Xl0" ohms developed an image, which was a combination of line and half tone copy, having excellent fill with no background being observable.
  • circuit means connected to said electrode and to ground 1 and solely including impedance means of a size selected so that a portion of the charge induced on the electrode by the charge on the member biases the potential on the electrode to an average potential which is somewhat greater in magnitude than the background potential of the image on the member.
  • said impedance means comprises a resistor
  • said impedance means comprises a resistor and a capacitor connected in parallel.
  • said impedance means comprises at least one adjustable impedance element.
  • the impedance means includes an adjustable resistor.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Developing For Electrophotography (AREA)
  • Dry Development In Electrophotography (AREA)
  • Magnetic Brush Developing In Electrophotography (AREA)
US808823A 1969-03-20 1969-03-20 Self-biasing development electrode for electrophotography Expired - Lifetime US3599605A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US80882369A 1969-03-20 1969-03-20

Publications (1)

Publication Number Publication Date
US3599605A true US3599605A (en) 1971-08-17

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Family Applications (1)

Application Number Title Priority Date Filing Date
US808823A Expired - Lifetime US3599605A (en) 1969-03-20 1969-03-20 Self-biasing development electrode for electrophotography

Country Status (8)

Country Link
US (1) US3599605A (ja)
JP (1) JPS4835501B1 (ja)
BE (1) BE745695A (ja)
CH (1) CH503297A (ja)
DE (1) DE2010097C3 (ja)
GB (1) GB1291944A (ja)
NL (1) NL169376C (ja)
SE (1) SE352457B (ja)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3691993A (en) * 1970-11-23 1972-09-19 Ibm Apparatus for transferring developed image
US3696784A (en) * 1970-12-15 1972-10-10 Xerox Corp Xerographic development apparatus
US3719165A (en) * 1971-09-03 1973-03-06 Eastman Kodak Co Tuner concentration control apparatus
US3822670A (en) * 1970-12-28 1974-07-09 Fuji Photo Film Co Ltd Liquid development apparatus for electrophotography
US3850662A (en) * 1971-09-10 1974-11-26 Kalle Ag Electrophotographic developing process and apparatus
US3850142A (en) * 1971-07-09 1974-11-26 Diagnostic Instr Inc Image development amplification
US3889637A (en) * 1973-06-28 1975-06-17 Xerox Corp Self-biased development electrode and reproducing machine employing same
US3901189A (en) * 1974-01-28 1975-08-26 Xerox Corp Magnetic brush developing apparatus
US3990394A (en) * 1973-08-27 1976-11-09 Konishiroku Photo Industry Co., Ltd. Control circuit used in development of electrostatic latent images and developing apparatus
US4040387A (en) * 1972-09-24 1977-08-09 Mita Industrial Co. Ltd. Electrostatic photographic copying apparatus
US4052127A (en) * 1973-01-24 1977-10-04 Ricoh Co., Ltd. Developing system
US4084538A (en) * 1976-02-09 1978-04-18 Rank Xerox, Ltd. Ambient temperature compensating device for power source apparatus for developing electrodes
FR2373083A1 (fr) * 1976-12-06 1978-06-30 Hoechst Ag Procede et dispositif de developpement d'une image electrostatique latente
US4111152A (en) * 1976-05-17 1978-09-05 Ricoh Co., Ltd. Electrostatographic apparatus comprising improved development bias means
USRE31371E (en) * 1973-01-24 1983-09-06 Ricoh Co., Ltd. Developing system
US4565438A (en) * 1984-02-01 1986-01-21 Xerox Corporation Development system using electrically field dependent developer material
US5138385A (en) * 1990-06-27 1992-08-11 Minolta Camera Kabushiki Kaisha Developing device with electrically floating developing roller

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5021254B1 (ja) * 1971-05-29 1975-07-22

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160091A (en) * 1959-05-14 1964-12-08 Xerox Corp High speed xeroprinter and method therefor
US3166432A (en) * 1959-05-07 1965-01-19 Xerox Corp Image development
US3428025A (en) * 1966-12-27 1969-02-18 Xerox Corp Xerographic development apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3166432A (en) * 1959-05-07 1965-01-19 Xerox Corp Image development
US3160091A (en) * 1959-05-14 1964-12-08 Xerox Corp High speed xeroprinter and method therefor
US3428025A (en) * 1966-12-27 1969-02-18 Xerox Corp Xerographic development apparatus

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3691993A (en) * 1970-11-23 1972-09-19 Ibm Apparatus for transferring developed image
US3696784A (en) * 1970-12-15 1972-10-10 Xerox Corp Xerographic development apparatus
US3822670A (en) * 1970-12-28 1974-07-09 Fuji Photo Film Co Ltd Liquid development apparatus for electrophotography
US3850142A (en) * 1971-07-09 1974-11-26 Diagnostic Instr Inc Image development amplification
US3719165A (en) * 1971-09-03 1973-03-06 Eastman Kodak Co Tuner concentration control apparatus
US3850662A (en) * 1971-09-10 1974-11-26 Kalle Ag Electrophotographic developing process and apparatus
US4040387A (en) * 1972-09-24 1977-08-09 Mita Industrial Co. Ltd. Electrostatic photographic copying apparatus
US4052127A (en) * 1973-01-24 1977-10-04 Ricoh Co., Ltd. Developing system
USRE31371E (en) * 1973-01-24 1983-09-06 Ricoh Co., Ltd. Developing system
US3889637A (en) * 1973-06-28 1975-06-17 Xerox Corp Self-biased development electrode and reproducing machine employing same
US3990394A (en) * 1973-08-27 1976-11-09 Konishiroku Photo Industry Co., Ltd. Control circuit used in development of electrostatic latent images and developing apparatus
US3901189A (en) * 1974-01-28 1975-08-26 Xerox Corp Magnetic brush developing apparatus
US4084538A (en) * 1976-02-09 1978-04-18 Rank Xerox, Ltd. Ambient temperature compensating device for power source apparatus for developing electrodes
US4111152A (en) * 1976-05-17 1978-09-05 Ricoh Co., Ltd. Electrostatographic apparatus comprising improved development bias means
FR2373083A1 (fr) * 1976-12-06 1978-06-30 Hoechst Ag Procede et dispositif de developpement d'une image electrostatique latente
US4565438A (en) * 1984-02-01 1986-01-21 Xerox Corporation Development system using electrically field dependent developer material
US5138385A (en) * 1990-06-27 1992-08-11 Minolta Camera Kabushiki Kaisha Developing device with electrically floating developing roller

Also Published As

Publication number Publication date
BE745695A (fr) 1970-07-16
SE352457B (ja) 1972-12-27
NL169376C (nl) 1982-07-01
DE2010097B2 (de) 1978-02-16
NL169376B (nl) 1982-02-01
DE2010097A1 (ja) 1970-10-08
NL7002172A (ja) 1970-09-22
CH503297A (de) 1971-02-15
DE2010097C3 (de) 1979-09-06
GB1291944A (en) 1972-10-04
JPS4835501B1 (ja) 1973-10-29

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