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WO1994022060A1 - Appareil de developpement a toner liquide - Google Patents

Appareil de developpement a toner liquide Download PDF

Info

Publication number
WO1994022060A1
WO1994022060A1 PCT/NL1993/000066 NL9300066W WO9422060A1 WO 1994022060 A1 WO1994022060 A1 WO 1994022060A1 NL 9300066 W NL9300066 W NL 9300066W WO 9422060 A1 WO9422060 A1 WO 9422060A1
Authority
WO
WIPO (PCT)
Prior art keywords
operative
developer
resilient blade
latent image
built
Prior art date
Application number
PCT/NL1993/000066
Other languages
English (en)
Inventor
Dorron Levy
Original Assignee
Indigo N.V.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Indigo N.V. filed Critical Indigo N.V.
Priority to PCT/NL1993/000066 priority Critical patent/WO1994022060A1/fr
Publication of WO1994022060A1 publication Critical patent/WO1994022060A1/fr

Links

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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
    • G03G15/101—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer for wetting the recording material

Definitions

  • the present invention relates to imaging apparatus using liquid toner in general and, more particularly, to development apparatus of such imaging apparatus.
  • electrostatic imaging systems known in the art in which liquid toner is used to develop an electrostatic latent image.
  • Such systems may include a photoconductive surface which is electrically charged and then selectively discharged, by exposure to an optical image, to form an electrostatic latent image on the photoconductor surface.
  • Some imaging systems, using liquid toner employ moving developer electrodes having electrically conductive surfaces such as endless metal belts or rollers in developing the image.
  • a portion of the electrode is closely spaced from the imaging surface so as to form therebetween a development region that contains liquid toner.
  • the closely spaced electrode enhances the electrostatic field at the imaging surface and aids in the removal of excess carrier liquid and unused toner particles from the development region.
  • U.S. Patent 4,400,079 to Landa describes a developing system utilizing a roller electrode having a conductive outer surface, a portion of which is closely spaced from the imaging surface.
  • a foam wiper pad mounted against the electrode surface is used to remove toner deposits therefrom.
  • used toner particles adhering to the developer surface are removed therefrom downstream of the development region by one or more resilient blades which engage the cylindrical surface of the developer roller.
  • blades consist of a thin sheet, having an operative edge which is urged against the outer surface of the developer electrode in either a "chiseling mode” (i.e. pointing to the direction generally opposite that of the electrode surface movement) or a “wiping mode” (i.e. generally parallel to surface and pointing in generally the same direction as the electrode surface movemen ) .
  • the blades are operative either to completely remove the toner particles from the developer electrode's surface, typically in the "chiseling mode", or to meter the thickness of the toner layer on the developer electrode, typically in the "wiper mode".
  • U.S. Patent 3,910,231 describes a system for removing used toner from a drum or belt including blades secured to rotatable shafts and disposed for operation in response to each color.
  • U.S. Patent 4,264,191 describes a two-layered cleaning blade. According to this invention, a relatively hard layer, made of a material having a Shore A durometer hardness of between 60 and 95, is laminated with a relatively soft resilient layer, having a Shore A durometer hardness of between 5 and 50, wherein the soft layer is much thicker than the hard layer. Apparently, this combination yields a relatively flexible blade having a relatively hard edge.
  • Patent 1,443,128 describes a generally metallic, thin, cleaning blade having an elastomer cleaning tip mounted only along the operative edge of the thin blade.
  • the non-metallic tip is operative to reduce the friction between the cleaning blade and the surface of a photoreceptor drum while the surface is being cleaned by the blade.
  • SUMMARY OF THE INVENTION The present inventor have found that when hard, thin, blades (typically, metal blades) are used for removing unused liquid toner from the developer electrode, agglomerations of toner particles tend to accumulate on the back side of the cleaning blade (i.e. the side not facing the developer electrode) forming a considerable buildup of toner waste.
  • This toner build-up may result in serious malfunctioning of the development apparatus caused, for example, by occasional breaking away of toner agglomerates into the toner collection system. Such agglomerates can interrupt the free-flow of toner or even clog the system.
  • prior art development systems using liquid toner cleaning blades require frequent maintenance including removal of the "sludge” gradually formed on the back side of the cleaning blade.
  • an object of the present invention to provide improved development apparatus for use with electrostatographic imaging systems employing liquid toner. More specifically, it is an object of the present invention to provide single color or multi-color electrostatic liquid toner imaging apparatus with reduced sludge formation within the development system of such apparatus.
  • the present invention provides, in a preferred embodiment thereof, development apparatus having a cleaning assembly including one or more sludge inhibiting, resilient blades operatively associated with the developer electrode. Used toner particles are removed efficiently, without accumulation of toner residues or sludge on the blade surfaces, from the surface of the developer electrode and preferably transported to used toner collection apparatus.
  • the present invention thereby provides, in a preferred embodiment, electrophotographic imaging apparatus combining a clean, relatively maintenance-free developer assembly with excellent image performance.
  • the present inventor has found that by forming an appropriate hydrodynamic profile on at least a portion of the back-surface of the cleaning blade, sludge formation on the back-surface may be dramatically reduced and, for most practical purposes, completely eliminated.
  • the back- surface of a thin metal cleaning blade is provided with a sludge-inhibiting hydrodynamic profile on its back which is operative to reduce sludge accumulations on the back surface of the blades to negligible amounts so that the apparatus does not require maintenance for removal of the sludge.
  • the hydrodynamic profile consists of a relatively thick layer of a preferably non conductive, preferably non-metallic, material. The hydrodynamic profile preferably varies in thickness such that the back surface profile is shaped to allow optimal flow of toner on the back surface. Applicant believes that when such flow is laminar, sludge formation is inhibited.
  • the hydrodynamic profile attached to the back surface of the cleaning blade is shaped in accordance with the shape of the typical sludge-profile equilibrium. According to this aspect, toner particles moving along such a hydrodynamic profile will generally not adhere to the profile, if the shape of the hydrodynamic profile is approximately equivalent to the maximal sludge accumulation profile of conventional planar surfaces.
  • the present invention includes electrostatic imaging apparatus for use with liquid toners, including an imaging surface, apparatus for forming on the imaging surface a latent image including image portions at a first voltage and background portions at a second voltage and a development apparatus for developing the latent image with a liquid toner including charged toner particles and carrier liquid .
  • the development apparatus includes a developer electrode rol ler , electri f ied to a third voltage intermediate the first and second voltages, having a portion closely spaced f rom the imaging surf ace to form a development region therebetween, whereat the latent image is developed with the liquid toner.
  • the development apparatus further includes , in accordance with a preferred embodiment of the invention, a toner removal assembly preferably including a resilient blade , urged against the outer surface of the developer roller, for removing the toner particles from the developer roller.
  • the resilient blade is formed of a thin hard base-sheet having attached to at least a portion of the back surface thereof a sludge inhibiting hydrodynamic profile.
  • the sludge- inhibiting hydrodynamic profile is formed of a relatively thick layer of a relatively flexible material and , more preferably, the relatively flexible material is also a non- conductive material .
  • the hard base sheet is a sheet of metal such as, for example, stainless steel.
  • the general shape of the hydrodynamic profile attached to the base-sheet is approximately equivalent to the shape of typical sludge formation equilibrium in the absence of the hydrodynamic profile.
  • FIG. 1 is a schematic, cross sectional, illustration of electrostatic imaging apparatus constructed and operative in accordance with a preferred embodiment of the present invention
  • Fig . 2 is schematic, cross-sectional , illustration of part of the imaging apparatus of Fig . 1 , il lustrating particularly a development apparatus in accordance with a preferred embodiment of the invention
  • Fig . 3 is a schematic, cross sectional, illustration of part of the development apparatus of Fig . 2 , illustrating particularly a cleaning assembly in accordance with a preferred embodiment of the present invention.
  • DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference is now made to Fig . 1 , which illustrates an electrostatic imaging system constructed and operative in accordance with a preferred embodiment of the present invention .
  • the imaging system includes a rotating drum 10 having a photoconductive surface 12 of selenium or any other suitable photoconductor known in the art .
  • a charging device 14 which may be a corotron or a scorotron or any other charging device known in the art, is juxtaposed with surface 12 and is operative to charge surface 12 to a generally uni form predetermined voltage as drum 10 rotates past charging device 14. Further rotation of drum 10 brings charged photoreceptor surface 12 opposite an exposure station 15 which may include, for example, a laser scanner .
  • Exposure station 15 is operative to selectively expose portions of surface 12 to light, thus forming on surface 12 an electrostatic latent image including image portions at a first voltage and background portions at a second voltage.
  • an electrostatic master may be used to provide the electrostatic image in which case no exposure station is required.
  • Other methods of providing a latent image are also useful in the present invention.
  • Continued rotation of drum 10 brings photoconductor surface 12 into operative engagement with a developer electrode roller 18 forming a development region 20 between surface 12 and developer roller 18.
  • the latent image is developed at development region 20 by application thereat of liquid toner, including charged toner particles and carrier liquid, which is preferably dispensed by a liquid toner dispensing assembly 16.
  • Dispensing assembly 16 preferably includes a plurality of nozzles each of which sends a jet of liquid toner, preferably, toward the developer roller as shown in Fig. 2.
  • the liquid toner is preferably supplied to dispensing assembly 16 through a liquid toner inlet 17.
  • developer roller 18 is closely spaced from drum 10 and preferably rotates in the same direction as drum 10. Such preferred rotation provides that surface 12 and the surface of developer roller 18 move in opposite directions at development region 20.
  • developer roller 18 is electrified to a third voltage intermediate the first and second voltages of the image and background portions, respectively, of the latent image on surface 12. As a result of the difference in voltage between the surface potential of developer roller 18 and the image and background voltages of the latent image on surface 12, the charged toner particles selectively adhere only to the image portions of the latent image thereby developing the latent image.
  • toner particles in development region 20 opposite the background portions of the latent image are attracted to roller 18.
  • Dispensing assembly 16 and developer roller 18 form part of development apparatus 30 which is discussed in detail hereinbelow, in conjunction with figure 2.
  • a preferred type of toner for use with the present invention is described in example 1 of U.S. patent No. 4,794,651, the teachings of which are incorporated herein by reference.
  • Other carbon black toners may alternatively be used as well as colored liquid developers, in which the carbon black is replaced by color pigments as is well known in the art.
  • photoconductor surface 12 is engaged by an excess liquid removal assembly 22 , such as a squeegee roller urged against photoconductive surface 12.
  • the squeegee roller serves to compact the toned image , remove excess carrier l iquid therefrom and remove carrier liquid from the background portions of the latent image on surface 12 .
  • the squeegee rol ler i s preferably formed of a res i l ient , slightly conductive , polymeric material , and is electrified to a voltage of several hundreds to a few thousand volts of the same polarity as that of the charge toner particles .
  • Various types of intermediate transfer members are known in the art , some examples of which are described in U . S .
  • intermediate transfer member 24 is shown in Fig. 1 as a transfer drum, it may be equally suitable to use a transfer belt as transfer member 24. Alternatively, in a preferred embodiment of the invention , intermediate member 24 may be omitted and , in such a case , the developed image is directly transferred onto a final substrate . Transfer member 24 rotates in a direction opposite that of drum 10, as indicated by arrow 27 , such that there is substantially zero relative motion between their respective surface at their area of contact . Due to the simultaneous 1 rotation of drum 10, whose surface 12 bears the toner
  • substrate 26 such as a sheet of paper.
  • Drum 10 then returns to its starting position, ready for an
  • development apparatus 30 includes
  • a cleaning assembly 32 which may be selectably
  • each of the plurality of cleaners is
  • cleaning assembly 32 includes a resilient blade member 34 having an operative edge 35 and is preferably pivoted about a pivot 37.
  • member 34 When member 34 is activated, as described hereinbelow, operative edge 35 is urged against the cylindrical outer surface 19 of developer roller 18 thereby to remove used liquid toner from surface 19 and to direct the removed used toner into used toner collection unit 36.
  • the removed toner collected by collection unit 36 is later recycled, as is well known in the art, so as to be ready for reuse by toner dispensing assembly 16.
  • cleaning assembly 32 preferably includes two side wiping portions 38 which are arranged to engage the two end portions of outer surface 19 of roller 18.
  • Blade member 34 is mounted on a linkage which is selectably positioned by a conventional actuator 40. Further details of developers of this type can be found in WO Publication 90/14619, the disclosure of which is incorporated herein by reference.
  • the inventor of the present invention has found that, generally, when undeveloped liquid toner is removed from the developer roller by conventional blades, the toner particles tend to agglomerate and stick to the surfaces of blades forming a relatively large concentration of residual toner particles generally referred to as "sludge".
  • the inventor has discovered that such "sludge” build up appears mainly on the back surfaces of those conventional blades (i.e. the surface facing away from the developer roller).
  • the back-profile shape be such that the has also been found that the exact shape of the profile is not critical, since other shapes which reduce the turbulence substantially (for example by avoiding sharp corners)also result in reduction of sludge accumu1ations. It should be appreciated that sludge accumulation can not be generally reduced by simply using a very thin cleaning blade, as may be presumed. Similarly, the amount of accumulated sludge can generally be only partially reduced by coating the cleaning blade with a non- conductive or very toner-abhesive material . On the other hand sludge formation can be reduced by nearly an order of magnitude i f the appropriate hydrodynamic shape is used. Reference is now made to Fig .
  • blade member 34 includes a base- sheet 38 , which i s preferably made of sheet metal and whose thickness is approximately 100 micrometers .
  • base sheet 38 On back surface 42 of base sheet 38 there is preferably attached a prefabricated hydrodynamic back-profile 44 which covers at least a portion of back surface 42 , near operative edge 35 of blade 34.
  • Back profile 44 is preferably formed of relatively flexible , preferably plastic, material and has a cross-sectional shape as can be generally seen in Fig. 3.
  • profile 44 is similar to that of the "typical sludge profile" (i.e. the shape of typical sludge accumulation on the back surface of a conventional flat blade) or other turbulence reducing profile, sludge accumulation on the back surface of blade member 34 is dramatically reduced and, with the possible exception of a thin layer of toner on a face portion 47 of profile 44, even completely eliminated.
  • typical sludge profile i.e. the shape of typical sludge accumulation on the back surface of a conventional flat blade
  • other turbulence reducing profile sludge accumulation on the back surface of blade member 34 is dramatically reduced and, with the possible exception of a thin layer of toner on a face portion 47 of profile 44, even completely eliminated.
  • other, less ideal, hydrodynamic profiles are used, a lesser, but still striking, reduction of sludge formation is achieved. In general, shapes which have no sharp corners are most desirable.
  • back profile 44 is shaped in accordance with a turbulence reducing profile such as the "typical sludge profile", as shown in Fig. 3, its back surface 46 remains substantially free of sludge accumulation. It is a feature of an embodiment of the present invention that only negligible amounts of toner "sludge” accumulate on surface 46 of profile 44, when profile 44 is formed in accordance with this proper hydrodynamic shape. It should be appreciated that, unlike the typical sludge profile, profile 44 is formed of a physically stable material which is not likely to break- apart during operation of the development apparatus. Thus, clogging of the toner collection system by detached portions of the profile, which is typical of "the real sludge profile", is highly unlikely.
  • hydrodynamic back profile 44 is formed of a non-conductive material . In such a case , discharge of toner particles flowing on back surface 46 of profile 44 is prevented and sludge accumulation on surface 46 may be reduced even further .
  • developer electrode roller 18 may be coated with a non-conductive layer 19 which is operative to prevent discharge of the toner particles on the roller.
  • base sheet 38 is typically 100 micrometers thick and the total thickness of the blade i s between 1 - 5 mm thick , more preferably between 2-4 mm thick. A typical desired thickness is about 3 mm. It is appreciated that the "typical sludge profile" is dependent upon features of the specific development apparatus which is used. For example, there is generally more sludge accumulation in line with the toner jet (not shown in the Figures) which are generally employed by toner dispensing assembly 16.

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

Abstract

Appareil de formation d'images comprenant une surface (12) de formation d'images sur laquelle est formée une image latente, comportant des zones d'images chargées à une première tension et des zones de fond chargées à une seconde tension, ainsi qu'un révélateur servant à révéler l'image latente à l'aide d'un toner liquide comportant des particules de toner chargées et un liquide véhicule. Le révélateur comprend une électrode mobile et électrifiée de révélation (18) associée activement à la surface de formation d'images de manière à former entre elles une région de révélation dans laquelle l'image latente est révélée, et une lamelle élastique (32) dont le bord actif s'appuie contre la face externe (19) de l'électrode de révélation (18) après sa sortie de la région de révélation, afin d'évacuer les particules de toner de l'électrode de révélation. La lamelle élastique (32) comprend une feuille de base relativement mince (38) en matière relativement dure, constituant le bord actif et possédant une face postérieure (42) tournée généralement vers l'extérieur par rapport au rouleau de révélation, ainsi qu'une surépaisseur (44) présentant dans le sens de son épaisseur un profil non homogène formé par voie hydrodynamique, et étant montée sur au moins une partie de la face postérieure (42) de la lamelle élastique à proximité du bord actif, cette surépaisseur étant destinée à réduire sensiblement l'accumulation de particules de toner sur la lamelle élastique.
PCT/NL1993/000066 1993-03-23 1993-03-23 Appareil de developpement a toner liquide WO1994022060A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/NL1993/000066 WO1994022060A1 (fr) 1993-03-23 1993-03-23 Appareil de developpement a toner liquide

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/NL1993/000066 WO1994022060A1 (fr) 1993-03-23 1993-03-23 Appareil de developpement a toner liquide

Publications (1)

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WO1994022060A1 true WO1994022060A1 (fr) 1994-09-29

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WO (1) WO1994022060A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6100442A (en) * 1997-06-24 2000-08-08 Sca Hygiene Products Aktiebolag Absorbent article with improved leakage security
CN103092043A (zh) * 2013-02-07 2013-05-08 珠海天威飞马打印耗材有限公司 清洁刮刀及处理盒

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3910231A (en) * 1973-02-21 1975-10-07 Canon Kk Developing device for a polychromatic electrophotographic copier
GB1443128A (en) * 1973-05-03 1976-07-21 Xerox Corp Cleaning dry particulate material from a surface
US4042415A (en) * 1974-05-28 1977-08-16 Xerox Corporation Method for scraping liquids from a moving surface
US4264191A (en) * 1979-10-22 1981-04-28 Xerox Corporation Electrophotographic imaging system including a laminated cleaning and/or doctor blade
EP0333199A2 (fr) * 1988-03-17 1989-09-20 Nec Corporation Appareil de développement par liquide comprenant une bande perforée de transport de liquide
EP0356163A1 (fr) * 1988-08-23 1990-02-28 Minnesota Mining And Manufacturing Company Electrode de développement d'une image électrophotographique, avec un ruban continu

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3910231A (en) * 1973-02-21 1975-10-07 Canon Kk Developing device for a polychromatic electrophotographic copier
GB1443128A (en) * 1973-05-03 1976-07-21 Xerox Corp Cleaning dry particulate material from a surface
US4042415A (en) * 1974-05-28 1977-08-16 Xerox Corporation Method for scraping liquids from a moving surface
US4264191A (en) * 1979-10-22 1981-04-28 Xerox Corporation Electrophotographic imaging system including a laminated cleaning and/or doctor blade
EP0333199A2 (fr) * 1988-03-17 1989-09-20 Nec Corporation Appareil de développement par liquide comprenant une bande perforée de transport de liquide
EP0356163A1 (fr) * 1988-08-23 1990-02-28 Minnesota Mining And Manufacturing Company Electrode de développement d'une image électrophotographique, avec un ruban continu

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6100442A (en) * 1997-06-24 2000-08-08 Sca Hygiene Products Aktiebolag Absorbent article with improved leakage security
CN103092043A (zh) * 2013-02-07 2013-05-08 珠海天威飞马打印耗材有限公司 清洁刮刀及处理盒
CN103092043B (zh) * 2013-02-07 2016-03-09 珠海天威飞马打印耗材有限公司 清洁刮刀及处理盒

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