EP0462174B1 - Flüssige entwicklungssysteme mit selbst-beibehaltender schütt-leitfähigkeit - Google Patents

Flüssige entwicklungssysteme mit selbst-beibehaltender schütt-leitfähigkeit Download PDF

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Publication number
EP0462174B1
EP0462174B1 EP90904452A EP90904452A EP0462174B1 EP 0462174 B1 EP0462174 B1 EP 0462174B1 EP 90904452 A EP90904452 A EP 90904452A EP 90904452 A EP90904452 A EP 90904452A EP 0462174 B1 EP0462174 B1 EP 0462174B1
Authority
EP
European Patent Office
Prior art keywords
liquid developer
liquid
charge director
developer system
carrier liquid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP90904452A
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English (en)
French (fr)
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EP0462174A1 (de
Inventor
Benzion Landa
Yaacov Almog
Amnon Peled
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HP Indigo BV
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Indigo BV
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Filing date
Publication date
Application filed by Indigo BV filed Critical Indigo BV
Publication of EP0462174A1 publication Critical patent/EP0462174A1/de
Application granted granted Critical
Publication of EP0462174B1 publication Critical patent/EP0462174B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/06—Developing
    • G03G13/10—Developing using a liquid developer, e.g. liquid suspension
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/12—Developers with toner particles in liquid developer mixtures
    • G03G9/135—Developers with toner particles in liquid developer mixtures characterised by stabiliser or charge-controlling agents
    • G03G9/1355—Ionic, organic compounds

Definitions

  • This invention relates to the field of electrostatic imaging, and more particularly to a liquid developer system having improved properties.
  • a latent electrostatic image is generally produced by first providing a photoconductive imaging surface with a uniform electrostatic charge, e.g. by exposing the imaging surface to a charge corona. The uniform electrostatic charge is then selectively discharged by exposing it to a modulated beam of light corresponding, e.g., to an optical image of an original to be copied, thereby forming an electrostatic charge pattern on the photoconductive imaging surface, i.e. a latent electrostatic image.
  • the latent image may have either a positive charge (e.g. on a selenium Photoconductor) or a negative charge (e.g.
  • the latent electrostatic image can then be developed by applying to it oppositely charged pigmented toner particles, which adhere to the undischarged "print” portions of the photoconductive surface to form a toner image which is sub sequently transferred by various techniques to a copy sheet (e.g. paper).
  • a copy sheet e.g. paper
  • the toner particles are generally dispersed in an insulating non-polar liquid carrier, generally an aliphatic hydrocarbon fraction, which generally has a high-volume resistivity above 109 ohm cm, a dielectric constant below 3.0 and a low vapor pressure (less then 10 torr. at 25°C).
  • the liquid developer system further comprises so-called charge directors, i.e. compounds capable of imparting to the toner particles an electrical charge of the desired polarity and uniform magnitude so that the particles may be electrophoretically deposited on the photoconductive surface to form a toner image.
  • charge director compounds are generally ionic or zwitterionic compounds which are soluble in the non polar carrier liquid. This desired charging is achieved by providing a constant optimum concentration of charge director compound in the carrier liquid, which concentration is usually determined so as to achieve the highest copy quality for the particular application.
  • Stable electrical characteristics of the liquid developer are crucial to achieve high quality imaging, particularly when a large number of impressions are to be produced without changing the liquid developer system.
  • liquid developer to the photoconductive surface clearly depletes the overall amount of liquid developer in the reservoir of an electrocopying or electroprinting machine of this type.
  • the liquid reservoir is continuously replenished, as necessary, by addition of two liquids from two separate sources, the one providing carrier liquid and the other - a concentrated dispersion of toner particles in the carrier liquid. This is necessary in order to maintain in the carrier liquid in the reservoir a relatively constant concentration of toner particles, because the total amounts of carrier liquid and toner particles utilised per electrocopy vary as a function of the proportional area of the printed portions of the latent image on the photoconductive surface.
  • the rate of replenishment of carrier liquid is controlled by monitoring the overall amount or level of liquid developer in the reservoir, whereas the rate of replenishment of toner particles (in the form of a concentrated dispersion in carrier liquid) is controlled by monitoring the concentration of toner particles in the liquid developer in the reservoir.
  • An optical float can combine both these functions, i.e. can be utilized to monitor both the overall amount of liquid developer in the reservoir and the toner particle concentration therein.
  • the amount of charge director in the liquid developer reservoir must also be replenished, since the charge director is also depleted together with the carrier liquid and the toner particles.
  • the charge director is replenished by adding it with the carrier liquid replenishment or with the concentrated toner dispersion. As explained hereinbelow, this results in charge director imbalance in the liquid developer system with consequent impairment of the quality of the copies.
  • the amount of toner particles utilized per electrocopy varies in proportion to the relative printed area of the image.
  • a large number of so-called "white” copies i.e. originals with small printed areas
  • the amount of carrier liquid depleted will be comparatively large.
  • This amount of carrier liquid will be replenished and, in machines designed for adding the charge director only with the replenished carrier liquid, this will result in an increase of the concentration of charge director relative to the toner concentration. It can easily be seen that an opposite result will be observed in a photocopier machine designed so that the charge director is replenished together with the concentrated toner suspension only. In such machines a large number of "white” copies will cause a decrease in the concentration of charge director in the liquid developer system.
  • the present invention which, in accordance with one aspect thereof, provides a self-replenishing liquid developer system for use in electrostatic imaging, which system comprises:
  • the present invention is based on the concept of using a charge director compound which has a limited low solubility in the carrier liquid, such that the saturation concentration of the charge director in the carrier liquid is at a proper concentration as to bring about the electrical charging of the toner particles, to disperse them and to maintain them at the desired degree of dispersion.
  • a saturated solution of charge director in the carrier liquid is maintained in contact with a solid phase comprising or consisting of a considerable excess of the charge director compound, this solid phase will serve as a reservoir for the charge director compound.
  • concentration of this charge director in the liquid phase i.e.
  • the toner particles themselves which serve as the solid phase comprising the excess charge director compound.
  • the toner particles themselves which serve as the solid phase comprising the excess charge director compound.
  • the concentration of the charge director compound is continuously maintained by natural and rapid equilibration between the charge director in solution in the carrier liquid and the excess charge director comprised in the toner particles.
  • some charge director compound will diffuse from the solid phase, i.e. from within the toner particles, into the carrier liquid until dynamic equilibrium is reached when the concentration of charge director in the carrier liquid reaches its saturation value.
  • the excess of charge director compound preferably in the form of a finely dispersed powder, is contained in a container, at least a portion of the walls of which being made of a porous material which is permeable to the carrier liquid but does not permit the passage therethrough of the particulate solid charge director compound.
  • a container will be wholly or partially immersed in the reservoir of liquid developer so as to be in direct contact therewith.
  • a suitable container may be, for example a closed bag made of thin porous sheet material, e.g. filter paper or the like.
  • the liquid developer is always in direct equilibrium contact with the excess charge director in solid form, thereby achieving a constant saturation concentration of charge director in the liquid developer.
  • Black imaging material which is used in Examples 1 to 5 hereinbelow is prepared as follows:
  • a mixture of 2.5 parts by weight of Mogul L carbon black (Cabot) and 5 parts by weight of Isopar L is then added to the mix in the double planetary mixer and the resultant mixture is further mixed for 1 hour at high speed. 20 parts by weight of Isopar L preheated to 110°C are added to the mixer and mixing is continued at high speed for 1 hour.
  • the heating unit is then disconnected and mixing is continued until the temperature of the mixture drops to 40°C.
  • One part by weight of the solid dry calcium lauryl benzenesulfonate was co-melted with 9 parts by weight of black imaging material at 130°C.
  • the melt was cooled and 100 g thereof and 120 g of Isopar L were milled together for 19 hours in an attritor to obtain a dispersion of particles with an average diameter of about 2».
  • the attrited material obtained was washed several times with Isopar H and then dispersed in Isopar H at a content of 1% n.v.s.
  • the conductance of the toner was 3 pmho/cm.
  • the title material was purchased from Fluka and used without further treatment, after being left to equilibrate with air moisture. The material was repeatedly washed with Isopar H until a constant conductance of the supernatant solution was reached.
  • the solubility of sodium laurylbenzenesulfonate in Isopar H was determined spectrophotometrically to be 0.027% by weight.
  • Aerosol AY Cosmeticamide
  • Example 2 5 parts of sodium diamyl sulfosuccinate and one part of aluminium stearate were co-melted with 44 parts by weight of black imaging material in accordance with the procedure described in Example 1. 100 g of the co-melt were added to 120 g of Isopar H and milled for 19 hours as described in Example 1. The milled toner thus obtained was washed several times with Isopar and diluted with Isopar G to a 1% n.v.s. content of toner.
  • Example 1 The material obtained as described in Example 1 was placed in a bag prepared from folded Whatman MN filter paper, and the bag was immersed in a liquid developer and the conductance of the liquid developer measured. From time to time the bag was removed from the liquid developer which was centrifuged to remove the supernatant and the resultant toner particles were redispersed in pure Isopar H. Thereafter, the filter paper bag containing the charge director compound was re-installed and after several hours of stirring the conductivity of the liquid developer was measured again. To eliminate effects related to possible permeation of the charged toner particles through the filter paper, the conductance values obtained were compared with those of an identical control bag immersed in pure Isopar H.
  • Example 4 When the procedure of Example 4 was repeated with sodium laurylbenzenesulfonate (in Isopar H), calcium diisobutyl sulfosuccinate (in Isopar G) and sodium diamyl sulfosuccinate (in Isopar H using a bag made from Whatman No. 2 filter paper), similar results as in Example 4 were obtained.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Liquid Developers In Electrophotography (AREA)
  • Wet Developing In Electrophotography (AREA)

Claims (17)

  1. Selbstnachfüllendes Flüssigentwicklersystem für ein elektrostatisches Abbildungssystem, welches folgendes aufweist:
    (a) eine isolierende, nicht polare Trägerflüssigkeit;
    (b) Tonerpartikel, welche in der Trägerflüssigkeit dispergiert sind;
    (c) wenigstens eine Ladungsleiterverbindung, welche eine begrenzte Löslichkeit in der Trägerflüssigkeit hat und darin mit ihrer Sättingungskonzentration gelöst ist; und
    (d) der Überschuß der wenigstens einen Ladungsleiterverbindung in einer Festphase vorliegt und in Gleichgewichtskontakt mit der Trägerflüssigkeit ist.
  2. Flüssigentwicklersystem nach Anspruch 1, bei dem der Überschuß der Ladungsleiterverbindung in den Tonerpartikeln enthalten ist.
  3. Flüssigentwicklersystem nach Anspruch 1, bei dem der Überschuß der Ladungsleiterverbindung in fein dispergierter Feststoffform vorliegt und in einem Behälter in Kontakt mit und durchlässig für die Trägerflüssigkeit durch wenigstens einen Teil der Wände des Behälters enthalten ist.
  4. Flüssigentwicklersystem nach Anspruch 3, bei dem der Behälter ein Beutel ist, welcher aus dünnen Flächengebilden aus einem porösen Material hergestellt ist.
  5. Flüssigentwicklersystem nach Anspruch 4, bei dem das poröse Material Filterpapier ist.
  6. Flüssigentwicklersystem nach einem der vorangehenden Ansprüche, bei dem die Trägerflüssigkeit ein verzweigtkettiger aliphatischer Kohlenwasserstoff oder ein Gemisch aus derartigen Kohlenwasserstoffen ist.
  7. Flüssigentwicklersystem nach einem der vorangehenden Ansprüche, bei dem die Trägerflüssigkeit eine isoparaffinische Kohlenwasserstoffraktion ist, welche einen Siedebereich über 155°C hat.
  8. Flüssigentwicklersystem nach einem der vorangehenden Ansprüche, bei dem die Ladungsleiterverbindung ionisch oder zwitterionisch ist.
  9. Flüssigentwicklersystem nach Anspruch 8, bei dem die Ladungsleiterverbindung eine Metallseife ist.
  10. Flüssigentwicklersystem nach einem der vorangehenden Ansprüche, bei dem die Ladungsleiterverbindung die Fähigkeit hat, den Tonerpartikeln eine negative Ladung zu verleihen, welche in der Trägerflüssigkeit suspendiert sind.
  11. Flüssigentwicklersystem nach einem der vorangehenden Ansprüche, bei dem die Ladungsleiterverbindung Calziumlaurylbenzolsulfonat ist.
  12. Flüssigentwicklersystem nach einem der vorangehenden Ansprüche, bei dem die Ladungsleiterverbindung Natriumlaurylbenzolsulfonat ist.
  13. Flüssigentwicklersystem nach einem der vorangehenden Ansprüche, bei dem die Ladungsleiterverbindung Natriumdiamylsulfosuccinat ist.
  14. Elektrostatisches Abbildungsverfahren, welches die folgenden Schritte aufweist:
    (a) Ausbilden eines latenten Ladungsbildes auf einer Oberfläche;
    (b) Aufbringen von elektrisch geladenen Tonerpartikeln aus einem Flüssigentwicklersystem nach einem der vorangehenden Ansprüche auf die Oberfläche, um ein Tonerbild auf der Oberfläche auszubilden; und
    (c) Übertragen des erhaltenen Tonerbildes auf ein Substrat.
  15. Elektrostatisches Abbildungsverfahren, welches die folgenden Schritte aufweist:
    (a) elektrostatisches Aufladen einer lichtleitfähigen Oberfläche;
    (b) Belichten der lichtleitfähigen Oberfläche mit einem optischen Bild, wodurch ein latentes elektrostatisches Bild auf der lichtleitfähigen Oberfläche ausgebildet wird;
    (c) Aufbringen von elektrisch geladenen Tonerpartikeln aus einem Flüssigentwicklersystem nach einem der Ansprüche 1 bis 13 auf die lichtleitfähige Oberfläche, um ein Tonerbild auf der lichtleitfähigen Oberfläche auszubilden; und
    (d) Übertragen des erhaltenen Tonerbilds auf ein Kopierblattsubstrat.
  16. Verfahren zum Entwickeln eines latenten elektrostatischen Bildes bei einem flüssig entwickelnden elektrostatischen Abbildungsverfahren, welches die Verwendung eines Flüssigentwicklersystems nach einem der Ansprüche 1 bis 13 aufweist.
  17. Elektrokopier- oder Elektrodruckvorrichtung mit Flüssigentwicklung, welche ein selbstnachfüllendes Flüssigentwicklersystem nach einem der Ansprüche 1 bis 13 aufweist.
EP90904452A 1989-03-06 1990-03-05 Flüssige entwicklungssysteme mit selbst-beibehaltender schütt-leitfähigkeit Expired - Lifetime EP0462174B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US31912689A 1989-03-06 1989-03-06
US319126 1989-03-06
PCT/NL1990/000025 WO1990010894A1 (en) 1989-03-06 1990-03-05 Liquid developer systems with self-replenishment of bulk conductivity

Publications (2)

Publication Number Publication Date
EP0462174A1 EP0462174A1 (de) 1991-12-27
EP0462174B1 true EP0462174B1 (de) 1994-09-28

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Application Number Title Priority Date Filing Date
EP90904452A Expired - Lifetime EP0462174B1 (de) 1989-03-06 1990-03-05 Flüssige entwicklungssysteme mit selbst-beibehaltender schütt-leitfähigkeit

Country Status (5)

Country Link
EP (1) EP0462174B1 (de)
CA (1) CA2047675C (de)
DE (1) DE69012987T2 (de)
HK (1) HK137695A (de)
WO (1) WO1990010894A1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7144671B2 (en) 2003-09-30 2006-12-05 Samsung Electronics Company Adjuvants for negatively charged toners
US7118842B2 (en) 2003-09-30 2006-10-10 Samsung Electronics Company Charge adjuvant delivery system and methods
US7070900B2 (en) * 2003-09-30 2006-07-04 Samsung Electronics Company Adjuvants for positively charged toners

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3669886A (en) * 1968-09-11 1972-06-13 Hunt Chem Corp Philip A Liquid developer for electrostatography
US4003500A (en) * 1970-12-31 1977-01-18 Hoechst Aktiengesellschaft Metering device
US4193683A (en) * 1978-08-21 1980-03-18 Langner Fred R Method and apparatus for filtering developing liquid in a photocopier
AU7083687A (en) * 1986-02-14 1987-09-09 Savin Corp. Liquid developer charge director control
US4707429A (en) * 1986-04-30 1987-11-17 E. I. Du Pont De Nemours And Company Metallic soap as adjuvant for electrostatic liquid developer
DE3725002C2 (de) * 1986-07-28 1998-04-30 Ricoh Kk Entwicklungsnachfüllmaterial für ein elektrostatisches Kopiergerät
US4656966A (en) * 1986-08-04 1987-04-14 Eastman Kodak Company Method and apparatus for developing electrographic images uses molecular sieve zeolite
US4785327A (en) * 1987-09-03 1988-11-15 Savin Corporation Pneumatic charge director dispensing apparatus
US4812382A (en) * 1987-12-17 1989-03-14 Eastman Kodak Company Electrostatographic toners and developers containing new charge-control agents
US4869991A (en) * 1988-03-24 1989-09-26 Olin Hunt Specialty Products Inc. Charge director composition for liquid toner formulations

Also Published As

Publication number Publication date
CA2047675A1 (en) 1990-09-07
DE69012987T2 (de) 1995-05-04
CA2047675C (en) 1998-08-11
DE69012987D1 (de) 1994-11-03
EP0462174A1 (de) 1991-12-27
WO1990010894A1 (en) 1990-09-20
HK137695A (en) 1995-09-08

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