EP0092106B1 - Procédé de tirage électrophotographique pour ôter le liquide de développement d'une surface photoconductrice - Google Patents

Procédé de tirage électrophotographique pour ôter le liquide de développement d'une surface photoconductrice Download PDF

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Publication number
EP0092106B1
EP0092106B1 EP83103346A EP83103346A EP0092106B1 EP 0092106 B1 EP0092106 B1 EP 0092106B1 EP 83103346 A EP83103346 A EP 83103346A EP 83103346 A EP83103346 A EP 83103346A EP 0092106 B1 EP0092106 B1 EP 0092106B1
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EP
European Patent Office
Prior art keywords
photoconductor
metering
developer liquid
roller
voltage
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
Application number
EP83103346A
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German (de)
English (en)
Other versions
EP0092106A1 (fr
Inventor
Roland Dr. Moraw
Günther Schädlich
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.)
Hoechst AG
Original Assignee
Hoechst AG
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 Hoechst AG filed Critical Hoechst AG
Publication of EP0092106A1 publication Critical patent/EP0092106A1/fr
Application granted granted Critical
Publication of EP0092106B1 publication Critical patent/EP0092106B1/fr
Expired legal-status Critical Current

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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
    • G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
    • G03G15/11—Removing excess liquid developer, e.g. by heat

Definitions

  • the invention relates to an electrophotographic copying process with removal of developer liquid from a photoconductor surface, which is electrostatically charged and exposed for informational purposes, the latent charge image obtained with the developer liquid developing into a visible toner image and the excess developer liquid being removed with a metering element arranged at a short distance from the photoconductor surface , to which a bias voltage of the same polarity as that of the charged photoconductor surface is applied, the toner image is transferred from the photoconductor to an image receiving material, fixed thereon and the photoconductor is cleaned and / or discharged.
  • DE-A-3 018 241 discloses such a method for removing excess developer liquid from a liquid developer consisting of an insulating developer liquid and charged toner particles suspended therein from a photoconductive surface which bears an electrostatic charge image developed by means of the liquid developer.
  • a drying element in the form of a squeeze roller or a suction roller is brought into contact with the photoconductive surface, the squeeze roller or the suction roller being kept at a potential whose polarity is equal to the polarity of the charge of the charged toner particles and moreover the relative movement between the photoconductive surface and the squeeze roller or the suction roller is controlled so that the relative speed in the contact area becomes zero.
  • the outer surface of the squeeze roller or the suction roller consists of an elastomeric material which has a Shore A hardness of less than 45 and a resistance value of less than 10 9 ohm-cm.
  • the photoconductive surface is located on a drum which runs counterclockwise past a metering or stripping roller which is suitable for limiting the amount of liquid remaining on the photoconductor after the development of the latent charge image. This metering or stripping roller does not touch the developed charge pattern, so that neither streaks nor distortions are generated. A developer liquid layer with a thickness between 10 and 15 ⁇ m then remains on the photoconductor surface.
  • the drum surface runs past the squeeze or suction roller, which is held at such a pretension that an electrical field results, by means of which the toner is held on the photoconductor surface.
  • the bias applied to the nip roller has the same polarity as the toner particles in the developer liquid. In this way it is achieved that the developed image adheres to the surface of the photoconductor without streaks, without smearing and without the toner being transferred to the squeeze roller.
  • the liquid developer layer still present on the photoconductor surface is reduced to a thickness of 2 to 3 11 m after passing the squeeze roller, so that the layer thickness of the developer liquid on the photoconductor is reduced overall to about a fifth of the initial value.
  • the liquid development has the disadvantage that the copies have to be heated, since after the transfer of the toner image from the photoconductor surface to the image-receiving material together with residual developer liquid , this must be evaporated by heating when fixing the copies.
  • developer liquid is lost in large quantities and must be replenished again and again in the copying machine, and on the other hand, the air in the vicinity of the copying machine undesirably accumulates with evaporated developer liquid.
  • the usual developer liquids as such are not toxic, these are predominantly aliphatic hydrocarbons such as i-decane, in which the charged toner particles are dispersed, the large discharge of developer liquid is also undesirable for reasons of low environmental impact.
  • the stripping or dosing roller is separated from the photoconductor surface by a gap of 0.05 to 1 mm in width. Due to the counter-rotation of the metering roller with a greater peripheral speed than that of the photoconductor drum, the developer liquid in the metering gap between the photoconductor and the metering roller is divided into two oppositely directed flows, one flow being sheared off by the metering roller and removed by a downstream wiper blade. With a metering gap of 100 ⁇ m, the discharge is on Developer liquid through a DIN A4 copy about 0.2 g, so that because of the linearity between the developer liquid discharged and the metering gap it can be assumed that the discharge will be about 0.1 g developer liquid with a gap of 50 1 m.
  • the metering roller is held in insulated bearing disks, and a preload of approximately 300 V is formed on the roller by induction.
  • the image areas on the photoconductor surface have an electrical potential of 900 to 950 V, while the non-image background areas have an electrical potential of about 150 V. Since the electrical potential of the metering roller is lower than that of the image area and higher than that of the non-image areas on the photoconductor, the toner flows from the non-image areas to the image areas and is held on to them.
  • a reduction in the discharge of developer liquid due to a higher peripheral speed of the metering roller is hardly possible because of the asymptotic decrease in the discharge as a function of the peripheral speed, since the peripheral speed required for a noticeable discharge would be very difficult to achieve in conventional copying machines.
  • a noticeable reduction in the gap between the metering roller and the photoconductor surface below 50 .mu.m, which would lead to a reduction in the discharge of developer liquid, cannot be achieved because of the precision tolerances with regard to the straightness of the photoconductor drum and the metering roller.
  • gaps larger than 50 gm are to be aimed for, because the drums and metering rollers are more bulky, while at the same time reducing the discharge of developer liquid.
  • the object of the invention is to improve a method of the type described above so that the discharge of developer liquid in copies up to DIN Al formats is reduced without a reduction in the gap between the metering element and the photoconductor surface and an increase in the peripheral speed of the Dosing element is required.
  • bias of the metering element is greater than 1 kV and the maximum voltage on the photoconductor surface is selected to be equal to or less than the bias of the metering element.
  • the difference between the maximum voltage on the photoconductor surface and the bias of the dosing element is preferably up to 200 V.
  • the advantage is achieved that the discharge of developer liquid is considerably reduced by the simple measure of applying a large electric field in the gap between the metering element and the photoconductor surface while maintaining the other copying conditions.
  • FIG. 1 The structure of a copying machine with which the method according to the invention can be carried out corresponds to the prior art and is shown schematically in FIG. 1.
  • a trom mel 1 is provided with a photoconductor 21 and is rotated by a drive source, not shown, at a predetermined speed in the counterclockwise direction.
  • the photoconductor 21 is made of organic material, for example poly-N-vinylcarbazole / trinitrofluorenone, the photoconductor is negatively charged by the electrostatic charging device, while a positive charge takes place in the case of a photoconductor 21 made of selenium.
  • the charged photoconductor 21 is exposed to information in the exposure station 3 via its optics, i. H. exposed with a radiation pattern of an original.
  • the electrostatic latent charge image obtained is developed in the development station 22 into a visible toner image by means of the developer liquid.
  • the development station 22 consists of a curved plate 4, which is adapted with its curvature to the peripheral surface of the drum 1 and a trough 5, which is filled with developer liquid.
  • the plate 4 serves as a development electrode and is supplied with a certain voltage by a voltage source, not shown.
  • a roller can also be provided.
  • the toner particles dispersed in the developer liquid are positively charged, while in selenium layers they are negatively charged. Excess developer liquid is largely removed by the removal device, which consists of the roller 6 with a scraper 7.
  • image-receiving material for example a paper sheet 8 is fed to the drum 1 from a container 25.
  • the transfer station 16 contains a charging device 9, for example a corona, which charges the paper sheet 8 electrostatically from the rear. In the case of a selenium photoconductor 21, the paper sheet 8 is charged positively.
  • a pressure roller can also be provided, which bears against the peripheral surface of the drum 1 and is connected to a voltage source which charges the pressure roller to a suitable potential for the transfer. After the transfer of the toner image from the photoconductor 21 to the paper sheet 8, the latter is detached from the peripheral surface of the drum 1 and passed over a heating device 10 which dries the still moist toner image.
  • the cleaning device comprises a roller 11, for example a foam roller, and a wiper lip 12 which is arranged in the immediate vicinity of the roller 11.
  • the roller 11 is wetted with developer liquid and, together with the wiper lip 12, cleans the toner surface of the photoconductor surface.
  • the charging device 13 removes all residual charges of the photoconductor 21, which is completely discharged.
  • the DC corona 2 is supplied with an operating voltage of +6.3 kV when the photoconductor 21 is selenium.
  • the approximately 50 1 1m thick selenium photoconductor layer charged to approximately +1150 V is discharged and toner particles are deposited in accordance with the residual charge then present on the photoconductor layer in order to develop the latent charge image into a toner image .
  • the charging device 14 consists of the DC corona 2, which is connected to a high-voltage circuit 15, which is designed to carry out the method according to the invention for a continuous operating voltage of 8 kV of the DC corona 2.
  • the metering roller consists of aluminum, which is anodized on the surface and rotates at a distance of 50 ⁇ m in the opposite direction to drum 1 at three times the peripheral speed.
  • the metering roller 6 carries in a manner not shown, at the ends of its protruding stub shafts, rollers made of insulating material with built-in roller bearings which are rotatably mounted in shields. By selecting the diameters of these discharge rollers, the desired column S between the metering roller 6 and the photoconductor surface is predetermined.
  • the drain rollers are in fixed contact with the photoconductor surface on the drum 1.
  • a voltage source 17 is connected to the metering roller 6.
  • Isopar M is a liquid isoparaffinic hydrocarbon that boils at 223 "C.
  • the fusing station of the copying machine is switched off and a larger number of copy sheets are weighed before and after they have passed through the copying machine.
  • Different voltages between 0 and + 2 kV are applied in succession to the metering roller 6.
  • the amount of developer liquid discharged increases linearly with the width of the gap S when the metering roller 6 is without tension. Almost the same situation arises at a voltage of + 1 kV on the metering roller 6.
  • the influence of the speed of the counter-rotation of the metering roller 6 with respect to the photoconductor on the discharge of developer liquid is reduced by the high voltage on the metering roller 6.
  • the discharge is only 20 to 30% smaller if the metering roller 6 rotates at 1.5 times the peripheral speed instead of at 3 to 31 ⁇ 2 times the peripheral speed in the opposite direction to the photoconductor.
  • the circumferential speed of the metering roller 6 and the photoconductor aligned the reduction in the discharge of developer liquid when the high voltage is applied is considerable if only it is ensured that a developer, such as the wiper blade 7 in FIG. 1, removes the developer liquid drawn from the metering roller 6 by its Surface is removed.
  • measures are suitable which enable fast, stable and dense deposition of toner particles on the charged areas of the photoconductor.
  • it can be provided to provide an application roller for the toner instead of a sheet-like electrode 4, which has a distance of approximately 50 ⁇ m from the photoconductor and constantly supplies it with fresh developer liquid, so that no premature depletion by already deposited in the developer liquid layer in contact with the photoconductor Toner particles occur.
  • the strong electric field as a result of the short distance of only 50 ⁇ m, favors a rapid separation of the toner particles. This results in easy-to-read, groundless copies with a density of 0.65.
  • the toner density is determined by the logarithm of the ratio of the amount of light reflected on the copy and the amount of light reflected from the developed toner image.
  • the discharge of developer liquid through the copies is about 0.065 g per A4 copy. If the metering roller is earthed, i. H. if there is no voltage on it, the discharge is approx. 0.16 g per A4 copy.
  • the stability of the toner images deposited on the photoconductor can be further increased by an additional development electrode, not shown, between the application point of the developer liquid and the metering roller.
  • An effective measure to increase the stability of the toner images on the photoconductor is to charge the photoconductor layer beyond the charging voltage U maxD , this voltage determining the copying conditions under which copies of maximum toner density are obtained according to the prior art.
  • the maximum charging voltage for a photoconductor layer made of 50 ⁇ m selenium is +1150 V. If the corona voltage for charging is increased from + 6.3 kV to +8 kV, the photoconductor layer made of selenium is charged to approximately +1800 V.
  • the deposited toner images are not removed even by a metering roller with a potential of +2 kV. Under these conditions, the voltage of the transmission corona in the transmission station only has to be increased from +6.3 kV to +7.5 kV. If a transfer roller is used instead of a transfer corona, its potential must be increased accordingly.
  • the copies produced under such copying conditions with a gap of 50 ⁇ m have optical densities between 0.9 and 1.1. The copies themselves are dry because the Isopar M content is only about 0.015g per A4 copy.
  • the output of developer fluid of 0.015 g per A4 copy with a metering gap of 50 ⁇ m is remarkably low.
  • the template for such a copy has a coverage of 7% with black characters or symbols.
  • the discharge of developer liquid under otherwise identical conditions is only 0.003 g to 0.004 g per A4 copy.
  • a discharge of developer fluid of approximately 0.01 g per A4 copy with a 7% coverage original appears to be the lower amount required to give the toner particles deposited on the photoconductor the pasty consistency required for transfer to the image-receiving material to rent.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Wet Developing In Electrophotography (AREA)
  • Developing For Electrophotography (AREA)
  • Control Or Security For Electrophotography (AREA)

Claims (8)

1. Procédé de copiage électrophotographique avec enlèvement d'un liquide de développement d'une surface d'un photoconducteur, qui est chargée par voie électrostatique et est exposée conformément à l'information, et selon lequel l'image latente de charges obtenue est développée au moyen du liquide de développement en une image de toner visible et le liquide de développement en excès est éliminé au moyen d'un élément doseur disposé à faible distance de la surface du photoconducteur et auquel est appliquée une tension de polarisation de même polarité que celle de la surface chargée du photoconducteur, l'image de toner est transférée depuis le photoconducteur sur un matériau de réception de l'image et est fixée sur ce dernier et le photoconducteur est nettoyé et/ou est déchargé, caractérisé par le fait que la tension de polarisation de l'élément doseur est supérieure à 1 kV et la tension maximale à la surface du photoconducteur est égale ou inférieure A la tension do polnri sation de l'élément doseur.
2. Procédé de copiage électrophotographique selon la revendication 1, caractérisé par le fait que la différence entre la tension maximale à la surface du photoconducteur et la tension de polarisation de l'élément doseur est égale jusqu'à 200 volts.
3. Procédé de copiage électrophotographique selon les revendications 1 et 2, caractérisé en ce que la tension de polarisation de l'élément doseur se situe dans la gamme allant de 1,5 à 2 kV.
4. Procédé de copiage électrophotographique selon la revendication 1, caractérisé en ce que l'élément doseur est réalisé sous la forme d'un rouleau doseur et est disposé à une distance plus faible de la surface du photoconducteur, que l'épaisseur de la couche du liquide de développement sur la surface du photoconducteur.
5. Procédé de copiage électrophotographique selon la revendication 1, caractérisé en ce que la surface du photoconducteur est chargée à une tension supérieure à la tension de charge UmaxD pour la densité maximale du toner des copies.
6. Procédé de copiage électrophotographique selon la revendication 4, caractérisé en ce qu'une fente de dosage S de 50 à 130 µm est prévue entre la surface du photoconducteur en sélénium et le rouleau doseur, auquel est appliquée une tension de polarisation de +1,5 kV.
7. Procédé de copiage électrophotographique selon la revendication 4, caractérisé en ce qu'une fente de dosage S de 50 à 200 µm existe entre la surface du photoconducteur en sélénium et le rouleau doseur, pour une tension de polarisation de +2 kV du rouleau doseur.
8. Procédé de copiage électrophotographique selon une ou plusieurs des revendications 1 à 7, caractérisé en ce que le liquide de développement est enlevé le long d'une fente de dosage S d'une longueur allant jusqu'à 105 cm.
EP83103346A 1982-04-15 1983-04-06 Procédé de tirage électrophotographique pour ôter le liquide de développement d'une surface photoconductrice Expired EP0092106B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3213798 1982-04-15
DE19823213798 DE3213798A1 (de) 1982-04-15 1982-04-15 Elektrofotografisches kopierverfahren zum abtragen von entwicklerfluessigkeit von einer fotoleiteroberflaeche

Publications (2)

Publication Number Publication Date
EP0092106A1 EP0092106A1 (fr) 1983-10-26
EP0092106B1 true EP0092106B1 (fr) 1985-09-11

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EP83103346A Expired EP0092106B1 (fr) 1982-04-15 1983-04-06 Procédé de tirage électrophotographique pour ôter le liquide de développement d'une surface photoconductrice

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US (1) US4482241A (fr)
EP (1) EP0092106B1 (fr)
JP (1) JPS58187963A (fr)
AU (1) AU551304B2 (fr)
CA (1) CA1205125A (fr)
DE (2) DE3213798A1 (fr)

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Also Published As

Publication number Publication date
CA1205125A (fr) 1986-05-27
AU551304B2 (en) 1986-04-24
JPS58187963A (ja) 1983-11-02
EP0092106A1 (fr) 1983-10-26
US4482241A (en) 1984-11-13
DE3213798A1 (de) 1983-10-20
DE3360766D1 (en) 1985-10-17
AU1324483A (en) 1983-10-20

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