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
  • G03G15/104—Preparing, mixing, transporting or dispensing developer

Definitions

• a recording medium e.g. a single sheet or a tape-shaped recording medium made of various materials, e.g. Paper or thin plastic or metal foils
• an intermediate image carrier e.g. a photoconductor
• potential images charge images
• the areas of the potential images to be colored are made visible by toner with a developer station (inking station). Subsequently, the toner image is transferred to the recording medium.
• developer liquid containing toner particles and carrier liquid may be used.
• the carrier liquid has a resistance of greater than 10 8 ohm * cm.
• Possible carrier fluids include silicone oil and hydrocarbons.
• a process for electrophoretic liquid development (electrographic development) in digital printing systems is known e.g. from WO 2005/013013 A2.
• a silicone oil-containing carrier liquid with dispersed therein color particles (toner particles) is used as the developer liquid. Further details can be taken from WO 2005/013013 A2, which is part of the disclosure of the present application.
• the supply of the developer liquid to the intermediate image carrier can be effected by means of an applicator roller, to which the developer liquid is fed through an anilox roller, on which a chamber doctor blade is arranged.
• an applicator roller to which the developer liquid is fed through an anilox roller, on which a chamber doctor blade is arranged.
• the use of chamber doctor blades for ink supply is known (EP 1 097 813 A2).
• the use of a chamber doctor blade in electrophoretic see pressure can be taken from WO 2005/013013 A2.
• a disadvantage of the known chamber doctor blades is that the flow of the developer liquid in the chamber doctor blade is not guided deliberately. As a result, vortices can occur and air bubbles can be introduced.
• the filling of the cells of the anilox roller takes place without potential assistance, so that the transition of the toner particles to the anilox roller is restricted.
• the achievable toner application per area element is limited and thus the inking area or the speed of the transition of the developer liquid to the anilox roller and thus the achievable
• a voltage is applied to the chambered doctor blade and the anilox roller.
• the anilox roller is constructed such that the shape of the wells can be changed by an electrical voltage.
• an elastic coating of the applicator roll which is required for nip formation to form the intermediate image carrier, quickly fades. sen.
• the pressure of the squeegee is too weak, a low cleaning efficiency is accepted, which leads to memory effects at high print load (areal coverage of the printed image) since not every spot of the applicator roll has the same amount of toner / area after one cycle ,
• the cleaning of the applicator can also be done by a cleaning roller with doctor.
• the problem to be solved by the invention is to provide a device and a method with which a stable, uniformly high coloring of the potential images on an intermediate image carrier with high transfer efficiency can be achieved. In this case, a high printing speed should be possible.
• the process involved in the transfer process of the developer liquid on the way to the intermediate image carrier Ligten functional elements are designed such that during each transfer process, the deposition time of the toner particles on the participating functional elements due to an electric field effect and the distance between the participating functional elements is less than the respective transmission time of the toner particles from functional element to functional element.
• the functional elements involved in the intermediate image carrier are designed in such a way that at each participating functional element in the cyclic process of the transition of the developer liquid from functional element to functional element in each cycle a force action is generated towards and away from the respective functional element.
• the force effect can be generated by acting on the charged toner particles electric field o- by a flow, d. H. a shearing action.
• the transition of the toner particles can also be assisted in the electric force effect by the fact that the functional elements involved have alternately a high-resistance and low-resistance.
• the device for developing potential images of images to be printed on an intermediate image carrier initially comprises, as the first component, a supply device which extracts developer liquid from a mixing device.
• the component can be used as functional elements - an anilox roller,
• the second component is an applicator device which is used as a functional element, e.g. an applicator roll or applicator belt is provided, which takes over the developer liquid from the supply device, and from which the developer liquid is transferred to the intermediate image carrier as a function of the potential images.
• an electrical voltage is applied between the feed device and the applicator device that the extent of the toner particle transition from the feed device to the applicator device is thereby defined. In addition, this can increase the toner concentration in the developer liquid.
• a cleaning device which cleans the residual image remaining after the development of the potential images on the applicator device.
• the cleaning device may comprise the functional elements cleaning roller, cleaning blade and cleaning flow element.
• roller and cleaning flow element is applied an electrical voltage, which facilitates the detachment of the toner particles of the residual image from the cleaning roller.
• the consequence is that the cleaning of the cleaning roller by the applied cleaning blade does not lead to a strong mechanical load on the toner particles.
• anilox roller of the feed device or the cleaning roller of the cleaning device have a high resistance, only a minimal electrical current transition of preferably ⁇ 1000 ⁇ A / Im, preferably ⁇ 100 ⁇ A / Im occurs at the transition area for the developer liquid between the supply device and applicator device or cleaning device and applicator device on. Then potential fluctuations over their surfaces are preferably ⁇ 10 V and the different potentials can be kept stable.
• the applicator device (applicator roller) transporting the developer liquid can have a small resistance and thus the voltage drop across its surface can be small, so that the potential difference present in the developer gap between applicator device and intermediate image carrier (eg photoconductor) (this results from the distance between charge potential or Discharge potential of the photoconductor and the symmetrically arranged therebetween bias potential of the applicator) is converted into a large electric field strength over the developer liquid.
• the surface layer of the applicator device may be chosen such that the resistance is ⁇ 10 8 ⁇ * cm, preferably 10 5 to 10 7 ⁇ * cm.
• the functional elements of the cleaning device, supply device or applicator device which transport the developer liquid may in each case be at least one roller which has a surface coating for determining its specific resistance according to the criteria given above.
• the resistance of the surface coating of the roller in the cleaning device (cleaning roller) and the roller in the feeding device (anilox roller) in the range of 10 6 ⁇ * cm to 10 10 ⁇ * cm, preferably 5 * 10 8 to 5 * 10 9 ⁇ cm and that of the roller in the applicator (applicator) at least factor 10 more conductive.
• Functional element may also be a band, but in the following is assumed in the explanation of rollers, without limiting the invention thereto.
• a conditioning device is arranged adjacent to the applicator device in the direction of movement of the developer liquid in front of the intermediate image carrier.
• the developer liquid to be supplied to the intermediate image carrier can be influenced in such a way that the toner particles in the developer liquid move to the surface of the applicator device.
• a layer which consists predominantly of carrier liquid forms on the surface of the developer liquid, with the result that the undesired coloring of non-image areas on the intermediate image carrier is reduced.
• the conditioning means may consist of a corotron at a potential, e.g. Drahtkorotron, or consist of a lying at an electrical potential roller (conditioning roller). The potential should be chosen so that charges are applied to the applicator roll as compared to toner particles of the same polarity.
• the diameter of the conditioning roll and the applicator roll are selected such that a separation flow between the applicator roll and conditioning roll is formed, the liquid surface on the applicator roll can be smoothed with the result that the toner particles are distributed more uniformly on the surface of the applicator roll. This leads to an improved print image.
• the feed device has an anilox roller with cups and webs and one at the Ras- ter roller arranged on chamber doctor blade.
• the chamber doctor blade can contain a chamber open to the anilox roller with an inlet and an overflow for the developer liquid, wherein the feed is designed such that the supplied amount of developer liquid is greater than or equal to the amount that passes to the anilox roller and the excess amount flows over the overflow.
• the sufficient and uniform supply of toner particles in the wells of the anilox roll is achieved by a sufficient supply and distribution of the Ent- Wicklertler crampkeit in the chamber doctor blade and by an electric field support within the chamber doctor blade.
• the function of the chamber doctor blade is further improved by providing in the chamber a first flow element adjacent to the anilox roller for distributing the developer fluid, inter alia, transversely to the pressure direction in the region of the transition of the developer fluid to the anilox roller.
• a first flow element adjacent to the anilox roller for distributing the developer fluid, inter alia, transversely to the pressure direction in the region of the transition of the developer fluid to the anilox roller.
• a further improvement in the function of the chambered doctor blade is achieved by a second flow element, which is arranged adjacent to the first flow element in the chamber and is located at an electrical voltage whose polarity is opposite to that of the first flow element. This serves to mix the developer liquid of the chamber with the residual liquid present in the wells of the anilox roll (which remains after the developer liquid has transferred to the applicator roll).
• the second flow element is therefore arranged in front of the first flow element in the direction of rotation of the anilox roller and lies adjacent to the anilox roller.
• the two flow elements are arranged and shaped to the anilox roller and the inner contour of the chamber such that a flow of the developer liquid is formed in the gap between the flow elements and the anilox roller, which is rectified to the direction of movement of the anilox roller surface.
• the Strömungsele- elements can be designed as electrically conductive profile elements, which are arranged in the chamber adjacent the opening parallel to the anilox roller and extend across the width of the chamber and are fixed electrically isolated, for example on the side walls of the chamber.
• the flow elements can be flattened in the direction of the anilox roller.
• the distance of the flow elements to the anilox roller can be adjusted to 10 to 2000 .mu.m, preferably 100 to 1000 .mu.m.
• the cleaning device may have a cleaning roller and a cleaning blade resting against the cleaning roller.
• the cleaning blade can be part of a half-chamber into which the istrakelte residual image flows. From there, the residual liquid can be discharged into a mixing device.
• the half-chamber which is at an electrical potential, is designed such that the level of the developer liquid is always above the cleaning blade to allow the toner particles present on the cleaning roller to disperse into the half-chamber.
• a fill level sensor can be provided, which controls a discharge pump, or the adjustment of the level in the half-chamber can be effected by an overflow, which is arranged above the cleaning blade.
• the function of the cleaning device can be improved by a cleaning flow element, which is arranged in the half-chamber adjacent to the cleaning roller, and is shaped so that a flow in the region between the cleaning flow element and the cleaning roller is formed, which is rectified to the direction of movement of the surface of the cleaning roller and having no discontinuities in the flow cross-section.
• the distance between the cleaning roller and the cleaning flow element should be set to 10 to 2000 ⁇ m, preferably 100 to 1000 ⁇ m. It is optimal if the cleaning flow element is arranged above the cleaning blade, but partially or completely below the level of the developer liquid in the half-chamber. Furthermore, it is expedient to apply an electric potential to the cleaning flow element, the z. B.
• the electrical voltage between the cleaning roller and the cleaning flow element should be selected such that the toner particles are detached from the surface of the cleaning roller, but deposition of the toner particles on the cleaning flow element is prevented.
• the electrical voltage between the cleaning roller and cleaning flow element can be between 10 V and 5000 V, preferably between 200 V and 2000 V.
• the tub In the lower part of the half-chamber, the tub, a movable element, eg. Example, a spiral-shaped spindle, are arranged below the liquid level, which can be actively moved by a drive.
• a movable element eg. Example, a spiral-shaped spindle
• the toner particles are deposited or removed within the developer liquid on the functional elements (anilox roller, applicator roller, cleaning roller). This compensates for fluctuations in the toner particles (charge, diameter).
• the wells of the anilox roller are defined by the field support between the first flow element and anilox roll filled with toner particles. The toner concentration is only increased during filling, so it can be previously dosed a low-concentration and thus better flowable developer liquid.
• 1 is a schematic diagram of an electrographic printing system
• FIG. 2 shows the construction of the device with indication of the voltage applied to the functional elements electrical potentials
• Figure 3 shows a further structure of the feeder
• Fig. 4 shows the structure of the conditioning within the
• FIG. 5 shows a second embodiment of the conditioning device within the developer device.
• Fig. 1 shows the components of a printing system DS, as z. B. from WO 2005/013013 A2 is known, this is hereby included in the disclosure.
• an intermediate image carrier 1 in FIG. 1 of a photoconductive drum, is a regeneration exposure 2, a charging station 3, an imagewise exposure element 4, a developing device 5, a transfer unit 6 for transferring the developed potential images onto a recording medium 7, an element 8 arranged for cleaning the photoconductor drum.
• the transfer unit 6 has an elastic transfer roller 60, a counterpressure roller 61 and a cleaning unit 62.
• the developer device 5 is treated in more detail below, the structure and the function of the other components are known and can be found, for example, in WO 2005/013013 A2.
• the developer device 5 has a feed device 51, an applicator device 52, a cleaning device 53 and optionally a conditioning device 54, FIG. 2.
• the applicator device 52 may be an applicator roller 520 or a developer belt, which is arranged in contact with the intermediate image carrier 1.
• the applicator roller 520 develops the potential images on the intermediate image carrier 1.
• the applicator roller 520 supplies a developer liquid at least from a carrier liquid and charged toner particles to the intermediate image carrier 1. The development takes place in a known manner.
• the developer liquid is supplied to the applicator roller 520 by a feeder 51.
• This feeding device 51 has an anilox roller 510 with cups and webs and a chamber doctor blade 511 arranged on the anilox roller 510.
• the chamber doctor blade 511 consists of at least one chamber 512, an inlet 513 and an overflow 514.
• the chamber doctor blade 511 according to FIG. 1 is described in the function in WO 2005/013013 A2.
• the developer liquid is taken from a mixing device MS and supplied by a first pump 515 of the cam blade 511.
• the excess liquid developer in the chamber 512 is passed via the overflow 514 in a collecting trough 516 and from there, the developer liquid can be pumped by means of a second pump 517 in the mixing device MS.
• FIGS. 2 and 3 The more detailed structure of the feeder 51 can be seen in FIGS. 2 and 3.
• This contains the chamber doctor blade 511 with the chamber 512, the inlet 513, the overflow 514 and the anilox roller 510 with the wells and webs.
• a first insulated flow element 518 is arranged adjacent to the anilox roller 510, to which an electric poWer 510 is arranged.
• tential U RW _p o t-eiement can be placed.
• a second insulated flow element 519 is arranged in the chamber 512, which can be supplied with an electrical potential U RW _p o t-Eiement2 independently of the first flow element 518.
• the flow elements 518, 519 are parallel to the anilox roller 510 and extend across the width of the chamber 512. They may be secured to sidewalls of the chamber 512 electrically isolated and may consist of an electrically conductive profile element.
• the chamber 512 may also be at an electrical potential U K ammer, as well as the anilox roller 510 at a potential U RW .
• the sufficient supply of toner particles in the developer liquid into the wells of the anilox roller 510 which is necessary for a high coloration of the potential images on the intermediate image carrier 1 at high printing speed, is achieved by a sufficient supply and distribution of the developer liquid in the chambered doctor blade 511 and achieved by an electric field support within the chambered doctor blade 511.
• an optimum of throughflowing volume of the developer liquid along the anilox roller 510 and the achievable electric field strength is achieved due to the distance between the anilox roller 510 and the potential U RW _p o t element provided first flow element 518.
• the supplied developer liquid is distributed via the inlet 513 in the chamber doctor blade 511 such
• the electrical field support is achieved by the electrical voltage between the first flow element 518 and the anilox roller 510.
• the voltage may optionally have a superposed AC voltage component.
• the arrangement and contour of the first flow element 518 thereby causes no field strength peaks arise and the area between the first flow element 518 and the anilox roller 510 is always filled with developer liquid. Accordingly, the achievable field strength is significantly higher than the air breakdown field strength and is in the range between 10 to 5 * 10 4 V / cm.
• the second flow element 510 can be used, to which a pure AC voltage or an AC voltage superimposed in combination with a DC voltage of the opposite polarity can be applied. It is arranged in front of the first flow element 518, seen in the direction of rotation of the anilox roller 510.
• the electric field between the second flow element 519 and the anilox roller 510 thus serves to mix the developer liquid with the residual liquid present in the wells of the anilox roller 510.
• the field between the first flow element 518 and the anilox roller 510 serves to increase the toner concentration in the wells of the anilox roller 510.
• the wells of the anilox roller 510 by field support between the first flow element 518 and the anilox roller 510 defined filled with toner particles.
• the toner concentration is only increased during the filling of the wells of the anilox roller 510, so it can be previously dosed a low-concentration and therefore better flowable developer liquid.
• the cleaning device 53 has, according to FIG. 2, a cleaning element realized as a cleaning roller 530 or a cleaning belt, which rests against the applicator roller 520; in the following, the cleaning roller is used as an example in the discussion.
• a cleaning blade 531 abuts, which wipes off the remaining image cleaned by the cleaning roller 530 from the applicator roller 520.
• the cleaning blade 531 is part of a half-chamber 532 having a trough 533 and a drain 534.
• a level sensor 537 may be provided in the half-chamber 532.
• an electrically insulated cleaning flow element 535 may be arranged in the half-chamber 532.
• the half-chamber 532 is designed such that a level of developer liquid is maintained, which lies above the cleaning blade 531, with the result that toner particles located on the cleaning roller 530 disperse into the amount of developing fluid present.
• a level of developer liquid is maintained, which lies above the cleaning blade 531, with the result that toner particles located on the cleaning roller 530 disperse into the amount of developing fluid present.
• a drainage pump (not shown in FIG. 2) which can be set via a filling level sensor 537 are provided.
• the cleaning flow element 535 may be near the cleaning roller 530 above the cleaning blade 531, but be arranged partially or completely below the level of the developer liquid.
• the distance may be in the range of 10 to 2000 microns, preferably 100 to 1000 microns.
• the voltage applied to the cleaning flow element 535 electric potential U Re w_p o t-Eiement3 is negative for a positive toner particles polarity than the potential U H is aibhunt on the cleaning blade 531 and the potential U Re w on the cleaning roller 530.
• the derived electric voltage sufficiently large to detach the toner particles from the surface of the cleaning roller 530, but low enough that the flow in the nip between the cleaning roller 530 and the cleaning flow member 535 prevents deposition of the toner particles on the cleaning flow member 535.
• the electrical voltage is between 10 V and 5000 V, preferably between 200 and 2000 V.
• the cleaning flow element 535 is shaped in such a way that discontinuities in the gap between the cleaning flow element 535 and the cleaning roller 530 in the flow cross-section can not occur and thus a flow in the flow
• Gap between the cleaning flow member 535 and the cleaning roller 530 is formed, which is rectified to the moving direction of the surface of the cleaning roller 530.
• a movable element for. B. a spiral spindle, are arranged below the desired liquid level.
• This element can be actively moved by a drive and serves to prevent deposits or the dissolution of deposits, e.g. after longer breaks due to
• the conditioning device 54 may be made of either a corotron, e.g. A wire corotron 540 (Fig. 4) to which an electric potential in the polarity of the toner particles is applied, or a conditioning roller 541 (Fig. 5). Charges of the same polarity as the toner particles are applied to the applicator roller 520 via the Korotron 540. Due to the insulating carrier liquid, the charges remain on the surface of the developer liquid. As a result, the toner particles are displaced from the surface of the developer liquid film in the direction of the applicator roll 520, there is a cover layer of carrier liquid on the developer liquid, which serves in the subsequent development step to avoid toner deposits on non-image areas on the intermediate image carrier 1.
• a corotron e.g. A wire corotron 540 (Fig. 4) to which an electric potential in the polarity of the toner particles is applied
• a conditioning roller 541 Fig. 5
• FIG. 5 shows the structure of the conditioning device 54 with conditioning roller 541. This is in contact with the developer liquid film on the applicator roller
• the conditioning roller 541 is provided with a separate electrical potential U Kon which is higher than the electrical potential of the applicator roller U A w.
• the resulting tension between conditioning roller 541 and applicator roller 520 is in the range of 10 V to 2000 V, preferably in the range from 200 V to 1000 V.
• the applicator roller 520 and the conditioning roller 541 roll off each other.
• the surface speed of the conditioning roller 541 is 0.8: 1 to 1: 0.8, preferably 1: 1 compared to the applicator roller 520.
• the toner particles are also displaced from the surface of the developer liquid film to the applicator roller 520 here.
• the suitable choice of the diameter of the conditioning roller 541 additionally generates a separation flow between the conditioning roller 541 and the applicator roller 520.
• the diameter of the conditioning roller 541 is selected to be in the range of 0.1 to 0.7 of the diameter of the applicator roller 520, preferably 0.2 to 0.5. Due to the small diameter of the conditioning roller 541, the separation flow has a pronounced velocity vector perpendicular to the surface of the applicator roller 520.
• the at the film cleavage after Disturbance of the liquid layer thickness arising from the roller contact has a short period length ( ⁇ 100 ⁇ m) and at the same time low amplitude. This causes a macroscopic smoothing of the liquid surface, correspondingly a uniform distribution of the toner particles on the applicator roller 520 and subsequently in the printed image.
• a conditioning blade 542 can be arranged on the conditioning roller 541.
• the conditioning blade 542 removes the carrier liquid located on the conditioning roller 541, which is depleted of toner particles due to the applied electric field and returns them to the mixer MS. Accordingly, the film of developer liquid remaining on the applicator roll 520 has an increased concentration of toner particles while having a lower total layer thickness.
• the field strength in the gap is determined by the unchanged applied potentials and the distance between them. The distance is reduced in accordance with the reduced layer thickness of the developer liquid and therefore leads to an advantageous for the development process higher field strength in the gap between insectsträ- ger 1 and applicator 520.
• it is possible to use a lower-concentrated and thus better flowable developer liquid to the conditioner
• the rollers used in the devices each have a surface coating.
• the coatings are selected such that no or only such a small electrical current flows via direct contact (eg webs of the anilox roller 510 on applicator roller 520, cleaning roller 530 or conditioning roller 541 on applicator roller 520) that different electrical potentials of the Rolls can be kept stable by the connected power supplies
• the coating of the elastic applicator roller 520 may have a specific resistance in the range between 10 4 to 10 8 ⁇ * cm, preferably between 10 5 to 10 7 , the resistance fluctuations may be ⁇ +/- 20% (preferably ⁇ +/- 10%). ), the layer thickness is between 3 and 12 mm, preferably 7 to 10 mm.
• the material used can be NBR rubber, PUR rubber. If the coating of the applicator roll 520 has two layers, the outer layer may consist of PVDF, ECO, fluoroelastomer, Teflon and have a layer thickness ⁇ 0.7 mm, the inner consist of the above-mentioned materials.
• the coating of the anilox roller 510 and the cleaning roller 530 may have a resistance between 10 8 ⁇ * cm and 10 10 ⁇ * cm and a layer thickness between 10 and 400 .mu.m, preferably between 50 and 200 .mu.m.
• the material used may include hard coat, ceramic (Al oxide, chromium oxide, titanium oxide or a mixture thereof).
• each share can be zero;
• the chamber doctor blade 511 preferably has the same potential as the anilox roller 510, optionally also higher potential compared to the anilox roller 510;
• the cleaning blade 531 and the half chamber 532 lateral sealing preferably have the same potential as the cleaning roller 530, optionally also a higher potential;
• the potentials at the flow elements 518, 519, 535 have been described above.
• the potentials are applied to the core of the rolls (510, 520, 530, 541) and of the inside of the strips.
• the surface coatings of the rollers form a system of matched resistances p.
• p anilox roller
• p applicator roller

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

Applications Claiming Priority (2)

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• 2005
  • 2005-11-18 DE DE102005055156A patent/DE102005055156B3/de not_active Expired - Fee Related
• 2006
  • 2006-11-14 AU AU2006314520A patent/AU2006314520A1/en not_active Abandoned
  • 2006-11-14 WO PCT/EP2006/068432 patent/WO2007057387A1/de active Application Filing
  • 2006-11-14 US US12/092,746 patent/US8099030B2/en not_active Expired - Fee Related
  • 2006-11-14 CN CN2006800417653A patent/CN101305326B/zh not_active Expired - Fee Related
  • 2006-11-14 EP EP06829990A patent/EP1955116A1/de not_active Withdrawn
  • 2006-11-14 JP JP2008540600A patent/JP5162463B2/ja not_active Expired - Fee Related

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