EP0895867A2 - Appareil d'impression électrostatique directe comprenant une électrode de bord et un champ de courant alternatif sur la surface des moyens d'alimentation en toner - Google Patents

Appareil d'impression électrostatique directe comprenant une électrode de bord et un champ de courant alternatif sur la surface des moyens d'alimentation en toner Download PDF

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Publication number
EP0895867A2
EP0895867A2 EP98202302A EP98202302A EP0895867A2 EP 0895867 A2 EP0895867 A2 EP 0895867A2 EP 98202302 A EP98202302 A EP 98202302A EP 98202302 A EP98202302 A EP 98202302A EP 0895867 A2 EP0895867 A2 EP 0895867A2
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EP
European Patent Office
Prior art keywords
toner particles
control electrodes
edge
printhead structure
flow
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.)
Withdrawn
Application number
EP98202302A
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German (de)
English (en)
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EP0895867A3 (fr
Inventor
Guido Desie
Frans Backeljauw
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Agfa Gevaert NV
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Agfa Gevaert NV
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Priority to EP98202302A priority Critical patent/EP0895867A3/fr
Publication of EP0895867A2 publication Critical patent/EP0895867A2/fr
Publication of EP0895867A3 publication Critical patent/EP0895867A3/fr
Withdrawn legal-status Critical Current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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/34—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner
    • G03G15/344—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner by selectively transferring the powder to the recording medium, e.g. by using a LED array
    • G03G15/348—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner by selectively transferring the powder to the recording medium, e.g. by using a LED array using a stylus or a multi-styli array
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/385—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material
    • B41J2/41—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing
    • B41J2/415—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing by passing charged particles through a hole or a slit
    • B41J2/4155—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing by passing charged particles through a hole or a slit for direct electrostatic printing [DEP]
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2217/00—Details of electrographic processes using patterns other than charge patterns
    • G03G2217/0008—Process where toner image is produced by controlling which part of the toner should move to the image- carrying member
    • G03G2217/0025—Process where toner image is produced by controlling which part of the toner should move to the image- carrying member where the toner starts moving from behind the electrode array, e.g. a mask of holes

Definitions

  • This invention relates to an apparatus used in the process of electrostatic printing and more particularly in Direct Electrostatic Printing (DEP).
  • DEP Direct Electrostatic Printing
  • electrostatic printing is performed directly from a toner delivery means on a receiving substrate by means of an electronically addressable printhead structure.
  • the toner or developing material is deposited directly in an image-wise way on a receiving substrate, the latter not bearing any image-wise latent electrostatic image.
  • the substrate can be an intermediate endless flexible belt (e.g. aluminium, polyimide etc.).
  • the image-wise deposited toner must be transferred onto another final substrate.
  • the toner is deposited directly on the final receiving substrate, thus offering a possibility to create directly the image on the final receiving substrate, e.g. plain paper, transparency, etc.
  • This deposition step is followed by a final fusing step.
  • the method makes the method different from classical electrography, in which a latent electrostatic image on a charge retentive surface is developed by a suitable material to make the latent image visible. Further on, either the powder image is fused directly to said charge retentive surface, which then results in a direct electrographic print, or the powder image is subsequently transferred to the final substrate and then fused to that medium. The latter process results in an indirect electrographic print.
  • the final substrate may be a transparent medium, opaque polymeric film, paper, etc.
  • DEP is also markedly different from electrophotography in which an additional step and additional member is introduced to create the latent electrostatic image. More specifically, a photoconductor is used and a charging/exposure cycle is necessary.
  • a DEP device is disclosed in e.g. US-A-3 689 935 This document discloses an electrostatic line printer having a multi-layered particle modulator or printhead structure comprising :
  • Each control electrode is formed around one aperture and is isolated from each other control electrode.
  • Selected electric potentials are applied to each of the control electrodes while a fixed potential is applied to the shield electrode.
  • An overall applied propulsion field between a toner delivery means and a support for a toner receiving substrate projects charged toner particles through a row of apertures of the printhead structure.
  • the intensity of the particle stream is modulated according to the pattern of potentials applied to the control electrodes.
  • the modulated stream of charged particles impinges upon a receiving substrate, interposed in the modulated particle stream.
  • the receiving substrate is transported in a direction orthogonal to the printhead structure, to provide a line-by-line scan printing.
  • the shield electrode may face the toner delivery means and the control electrodes may face the receiving substrate.
  • a DC-field is applied between the printhead structure and a single back electrode on the receiving substrate. This propulsion field is responsible for the attraction of toner to the receiving substrate that is placed between the printhead structure and the back electrode.
  • a DEP printer wherein the printhead structure is a mesh instead of a insulating base with printing apertures trough this base has been disclosed in US-A-5 036 341 .
  • this disclosure it is taught to introduce an AC-field with frequency between 2 and 5 kHz and peak voltages between 500 and 2000 V on the toner delivery means in order to speed up the printing.
  • the AC-voltage (in this disclosure 300 V peak to peak and frequency of 4.5 kHz) is adjusted such as to allow the toner particles to reach the printhead structure, thus enabling the overall DC voltage laid between the printhead structure and the image receiving substrate member to extract said toner particles from said powder cloud.
  • the overall DC voltage propels the toner particles onto the image receiving substrate interposed between the printhead and a backing electrode.
  • an AC voltage is used for the backing electrode during the cleaning cycle.
  • the AC voltage on the back electrode is phase shifted by 180° if compared with the AC field (400 V peak to peak, no frequency disclosed) that is used upon the charged toner conveyor which is needed to obtain a high toner mist production, leading to high optical densities and short printing times. Further on the AC voltage can also have a certain DC-offset.
  • a printhead structure is made from a thin ceramic insulating member with control electrodes applied to said ceramic member by thin film techniques such as sputtering, vacuum deposition, ion plating, chemical vapour deposition and screen printing. It is claimed in this patent application that the absence of a sticky coating layer under the conductive layer does make the printhead structure less sensitive to clogging. A big drawback of this technique, however, is the reduced adhesive power of the conductors to the substrate.
  • SA and SB sides of said insulating material
  • control electrodes characterised in that only one of said two sides forming said slit carries control electrodes.
  • Said edge electrode system proposed in US-A-5 625 392 suffers however from the drawback that, in order to obtain a good image contrast between image parts of low density and image parts of high density, the overall applied propulsion field between the toner applicator and the receiver on the back electrode must be set to a rather low value, leading to only a moderate printing speed.
  • a DEP device i.e. A device for direct electrostatic printing that can print at high speed with low clogging of the control electrodes and with high maximum density and with a high degree of density resolution (i.e. for producing an image comprising a high amount of differentiated density levels) and spatial resolution.
  • a further object of the invention is to provide a DEP device that can be used with a wide variety of types of toner particles, and that can print at high speed with low clogging of the control electrodes, with high maximum density and with a printing quality that is constant over a long period of time.
  • Edge printhead structure is a printhead structure, comprising an insulating material carrying control electrodes for image-wise modulating the toner flow at the edge of the insulating material, that is interposed in the toner flow in a DEP device on only one side of a toner flow.
  • NO toner flow influencing members are present on the side of the toner flow opposite to the side wherein the edge printhead structure is interposed. This differentiates the "edge printhead structure” from a printhead structure having a slit wherein the toner flow is image-wise modulated, as disclosed in EP-A- 780 740.
  • Toner bearing surface is the surface of the means for delivering toner particles from where a flow of toner particles to the image receiving substrate originates.
  • the frequency of an AC-field used in a DEP device wherein the printhead structure controls the flow of toner particles only from one side has to have a frequency between quite narrow limits. Only when the frequency of the AC-field, applied to the toner bearing surface, is between 1.5 and 3 kHz, good maximum density was obtained. Preferably the frequency of the AC-field is between 1.75 and 2.75 kHz. It was moreover found that a peak tot peak voltage lower than these disclosed in the prior art gave good results. A peak to peak voltage between 400 and 1000 V gave sufficient Dmax.
  • V AC The peak to peak voltage of the AC field (V AC ) to be used was found to be a function of the distance (d) from the toner bearing surface and the control electrodes on the edge printhead structure. It was found that, in a DEP device using an edge printhead structure an acceptable D max was reached when V AC /d ⁇ 10, an even better D max was reached when V AC /d ⁇ 15.
  • the device could also be operated when the distance between the control electrodes in the edge printhead structure and the surface of the toner delivery means was such that there was no sliding contact between the edge of the printhead structure and the toner delivery means. In this case there was only sliding contact between a spacer means mounted upon the edge electrode in a zone near to the edge of the edge electrode, and the toner delivery means.
  • said edge electrode could also be mounted on a rigid frame so that there is no sliding contact at all between the edge electrode and the toner delivery means.
  • the distance between the edge printhead structure and the back electrode could be raised to 1000 ⁇ m or more without loss in printing quality, thus enabling the printing on thick image receiving substrates or on image receiving substrates with large thickness variations.
  • the DEP device shown comprises means for delivering toner particles with a container (101) for developer (102) wherein a magnetic brush (103) having a core (103a) wherein magnets are present and a sleeve (103b) rotatably mounted around the core is present.
  • the developer (102) can be a mono component developer with magnetic toner particles and then on the surface of the sleeve of the magnetic brush, toner particles are present, i.e. the surface of the sleeve (103b) of the magnetic brush is the toner bearing surface.
  • the developer (102) can as well be a multi-component developer containing magnetic carrier particles and non-magnetic toner particles and then on the sleeve of the magnetic brush carrier and toner particles are present, but the sleeve is still a toner bearing surface.
  • the magnetic brush (103) can have a fixed core (103a) and a sleeve (103b) rotatably mounted around the core equipped with means for rotating the core.
  • the core (103a) of the magnetic brush is also equipped with means for rotating the core and can thus also be rotated and the sleeve (103b) can be rotated around the core or kept stationary. (The means for rotating the core and/or the sleeve are not shown in the figure).
  • a device for applying a DC voltage is connected to the sleeve of the magnetic brush and applies voltage V1 to said sleeve and a device for applying an AC-field is connected to the sleeve of the magnetic brush and applies AC-field AC1 to said sleeve (the toner bearing surface).
  • the amount of developer on the toner bearing surface is regulated by a doctor blade (113).
  • the device further comprises a back electrode (105) connected to a DC voltage source applying a voltage V4 to the electrode.
  • An image receiving substrate (108) is passed by means for moving the substrate (107) in the direction of arrow A between the surface of the sleeve (103b) and the back electrode by conveying means (107).
  • the difference between V4 and V1 applies a DC propulsion field wherein a flow of toner particles (104) is created from the sleeve of the magnetic brush (the toner bearing surface) to the image receiving substrate on the back electrode.
  • the AC-field - AC1 - on the sleeve of the magnetic brush makes the flow (104) of toner particles denser than when no AC-field would be present.
  • a printhead structure On one side of the flow of toner particles, a printhead structure (106), with an insulating material (106c) carrying control electrodes (106a) is interposed in the flow (104) of toner particles.
  • a DC-source (V3) is connected to the control electrodes and the voltage applied by this DC-source is image-wise modulated in order to modulate the toner flow image wise in the vicinity of the control electrodes.
  • the voltage applied by the DC source V3 can be varied between a value totally blocking the passage of the toner particles, and a value leaving the toner flow pass totally unimpeded.
  • the control electrodes in said printhead structure are placed at a distance d from the toner bearing surface, a spacer (110) keeps the distance d constant during operation of the device.
  • the device comprises further means (109) for fixing the toner particles to the image receiving substrate.
  • the toner bearing surface is the surface of the sleeve of a magnetic brush
  • a device according to a further embodiment of the invention is shown, wherein the toner bearing surface is the surface of an applicator carrying toner particles derived from a non-magnetic mono-component developer.
  • the device, shown in figure 2 is the same as the one shown in figure 1, except for the toner bearing surface, so only the numericals different from those used in figure 1 will be described.
  • a roller (112) is present, having a surface On this surface toner particles are applied by means of a feeding roller (111) made of porous foamed polymers.
  • a developer mixing blade (114) mixes and transports said non-magnetic mono-component developer towards said feeding roller.
  • a doctor blade (113) regulates the thickness of the charged toner particles upon the surface said roller (112), i.e. on the toner bearing surface.
  • FIG 2a an enlarged portion (within circle X) of figure 2 is shown with a specific design of the edge printhead structure.
  • an edge printhead structure is shown comprising an insulating material (106c) and carrying on the edge control electrodes (106a), isolated from each other and each connected over an integrated circuit with a DC voltage source V3.
  • the voltage applied by this DC-source is image-wise modulated in order to modulate the toner flow image wise in the vicinity of the control electrodes.
  • the voltage applied by the DC source V3 can be varied between a value totally blocking the passage of the toner particles, and a value leaving the toner flow pass totally unimpeded.
  • insulating material (106c) carrying the control electrodes (106a) is covered with an insulating material (110) serving as spacer, keeping the control electrodes at a distance, d, from the toner bearing surface (112).
  • This surface was connected to a DC source (V1) and an AC source (AC1).
  • V1 DC source
  • AC1 AC source
  • the edge printhead structure is attached to a frame (116) in such a way that the printhead structure has a free length (FL).
  • a back electrode (105) is present whereon a DC source applies a voltage V4. Between the back electrode and the printhead structure an image receiving substrate (108) is passed.
  • FIG 2b an enlarged portion (within circle X) of figure 2 is shown with a specific design of the edge printhead structure.
  • an edge printhead structure is shown comprising an insulating material (106c) and carrying on one face, at the edge of the face, control electrodes (106a) connected over an integrated circuit with a voltage source V3.
  • the face of the insulating material (106c) opposite to the face carrying the control electrodes (106a) is covered with a single shield electrode (106b) (whereon a single DC voltage is applied (V2).
  • V2 single DC voltage is applied
  • the shield electrode does not extend to the edge of the edge printhead structure.
  • On the shield electrode a spacer (110) is present keeping the control electrodes at a distance, d, from the toner bearing surface (112). This surface was connected to a DC source (V1) and an AC source (AC1). ).
  • a back electrode (105) is present whereon a DC source applies a voltage V4. Between the back electrode and the printhead structure an image receiving substrate (10
  • the toner bearing surface is the surface of the sleeve of a magnetic brush (in fig 1), or the surface of an applicator for non-magnetic mono-component developer.
  • a DEP device according to this invention can also be equipped with a charged toner conveyer (CTC) on the surface of which charged toner particles are applied by a magnetic brush or an applicator for non-magnetic mono-component developer.
  • CTC charged toner conveyer
  • the toner bearing surface is the surface of the CTC and the means for applying the AC-field AC1, are connected to that surface.
  • the printhead structure, used in a DEP device according to this invention can have any shape and form as described in US-A-5 625 392 .
  • the printhead structure (106) used in a DEP device according to the present invention preferably has the shape and form as shown in figure 3.
  • 106c represents the insulating material
  • 106a represents a complex addressable electrode structure, hereinafter called "control electrodes"
  • 106d represent the edge of the printhead structure interposed in the flow of toner particles
  • arrow TF represents the direction of the toner flow, from the toner bearing surface (not shown) to the image receiving substrate (not shown).
  • control electrodes 106d
  • arrow TF represents the direction of the toner flow, from the toner bearing surface (not shown) to the image receiving substrate (not shown).
  • FIG 3a the simplest form of the first embodiment of a printhead structure according to the present invention is shown : on one face of the insulating material (106c) control electrodes (106a) are present.
  • the printhead structure is shown with the control electrodes facing in the direction of the toner flow (i.e.
  • FIG. 3b a further variant a printhead structure according useful in a DEP device according to the present invention are shown.
  • control electrodes (106a) On both faces of the insulating material (106c) control electrodes (106a) are present.
  • the control electrodes (106a) on both faces of the insulating are located such as to have pairs of control electrodes (106a) (one on every face) exactly in register in pairs.
  • control electrodes (106a), being present on both faces of the insulating material (106c) can - as shown in figure 3c - , in pairs, be connected to each other via metallisation over edge (106d), forming a single control electrode.
  • Ways and means for connecting electrodes trough printing apertures are known in the art. Examples of such means have been disclosed in EP-A-753 413 .
  • FIG 3d and 3e further variants of a printhead structure useful in a DEP device according to the present invention are shown.
  • the control electrodes (106a) on both faces of the insulating material are staggered.
  • the width of the control electrodes parallel to the length of the edge (106d) is selected such as to have some overlap between the control electrodes on one face of the insulating material (106c) and control electrodes present on the other face.
  • the width of the control electrodes parallel to the length of the edge (106d) is selected such as to have no overlap between the control electrodes on one face of the insulating material (106c) and those on the other face.
  • FIG 4 an edge electrode according to an other embodiment of the present invention is shown.
  • 106c represents the insulating material
  • 106a represents a complex addressable electrode structure, hereinafter called “control electrodes”
  • 106b represents a common shield electrode located at the other side of said insulating material
  • 106d represent the edge of the printhead structure interposed in the flow of toner particles
  • arrow TF represents the direction of the toner flow, from the toner bearing surface means (not shown) to the image receiving substrate (not shown).
  • FIG 4a the simplest form of a printhead structure according to this embodiment of the present invention is shown : on one face of the insulating material (106c) control electrodes (106a) are present, on the other side the common shield electrode (106b) is present.
  • the edge 106d cuts in a single plane both control electrodes, isolating member and shield electrode.
  • the printhead structure is shown with the control electrodes facing in the direction of the toner flow (i.e. facing the image receiving substrate), it is possible to introduce such a printhead structure in a DEP device according to this invention with the control electrodes facing the other way round, i.e. facing the toner bearing surface.
  • FIG 4b a further embodiment of the present invention is shown.
  • a common shield electrode is present on one side of an isolating member control electrodes are present, on the other side a common shield electrode is present.
  • the edge is cutting down both control electrodes and isolating member but the shield electrode does not extent till the edge: i.e. the shield electrode ends at a certain distance from said edge, e.g. 500 ⁇ from said edge.
  • the use of a shield electrode on an edge printhead structure has the advantage that a larger tonal scale or larger density range can be printed than by using an edge printhead structure without shield electrode. . It was found that the distance of the shield electrode from the edge was an important parameter for achieving an optimum compromise between printable tonal range and the fog level in the print.
  • FIG 5 an edge electrode according to a further embodiment of the present invention is shown.
  • 106c represents the insulating material
  • 106a represents a complex addressable electrode structure, hereinafter called "control electrodes”
  • 106d represent the edge of the printhead structure interposed in the flow of toner particles
  • arrow TF represents the direction of the toner flow, from the toner bearing surface means (not shown) to the image receiving substrate (not shown).
  • said edge is not a straight line but is two-level-shaped.
  • the edge looks like a battlement with alternating crenels and merlons.
  • the crenels have a shape making it possible to position control electrodes at the edge of the crenels and the edge of the merlons parallel to the edge of the printhead structure in such a way that neighbouring control electrodes overlap each other to a certain extent.
  • FIG 5c an other way for making an edge printhead structure wherein neighbouring control electrodes overlap each other to a certain extent.
  • the edge is saw- toothed and each of the teeth carries a control electrode.
  • neighbouring control electrodes overlap each other as in figure 3b but in the embodiments shown in figure 5, both of said neighbouring control electrodes are located on the same face of the insulating material (106c) and are in a single plane.
  • the edge cut (either the saw-toothed shape or the battlement ) can be performed by e.g. an excimer laser.
  • the insulating material used for producing printhead structure, useful in a DEP device according to the present invention, can be glass, ceramic, plastic, etc.
  • said insulating material is a plastic material, and can be a polyimide, a polyester (e.g. polyethylelene terephthalate, polyethylene naphthalate, etc.), polyolefines, an epoxy resin, an organosilicon resin, rubber, etc.
  • Insulating material useful in the present invention, has a elasticity modulus between 0.1 and 10 Gpa, both limits included, preferably between 2 and 8 GPa and most preferably between 4 and 6 Gpa.
  • the insulating material has a thickness between 25 and 1000 ⁇ m, preferably between 50 and 200 ⁇ m.
  • the back electrode (105) of a DEP device according to this invention can also be made to co-operate with the printhead structure, said back electrode being constructed from different styli or wires that are galvanically isolated and connected to a voltage source as disclosed in e.g. US-A- 4, 568 ,955 and US-A-4, 733, 256 .
  • the back electrode, co-operating with the printhead structure can also comprise one or more flexible PCB's (Printed Circuit Board).
  • the present invention incorporates the operation of a DEP device according to the present invention in a method for direct electrostatic printing comprising the steps of :
  • a DEP device can also be operated without back electrode in a method for DEP printing on an insulating image receiving substrate, having a first and a second face, comprising the steps of :
  • a DEP device can further be operated in a method for direct electrostatic printing with reduced banding comprising the steps of :
  • a DEP device In a DEP device, according to of the present invention operate in the methods described above, and wherein the surface of the sleeve of the magnetic brush is used as toner bearing surface, (i.e. the toner flow originates directly from the surface of the sleeve of the magnetic brush), any type of known carrier particles and toner particles can successfully be used. It is however preferred to use "soft" magnetic carrier particles.
  • "Soft" magnetic carrier particles useful in a DEP device according to a preferred embodiment of the present invention are soft ferrite carrier particles. Such soft ferrite particles exhibit only a small amount of remanent behaviour, characterised in coercivity values ranging from about 4 up to 20 kA/m (from 50 up to 250 Oe).
  • Further very useful soft magnetic carrier particles for use in a DEP device according to a preferred embodiment of the present invention, are composite carrier particles, comprising a resin binder and a mixture of two magnetites having a different particle size as described in EP-B-289 663.
  • the particle size of both magnetites will vary between 0.05 and 3 ⁇ m.
  • the carrier particles have preferably an average volume diameter (dv50) between 10 and 300 ⁇ m, preferably between 20 and 100 ⁇ m. More detailed descriptions of carrier particles, as mentioned above, can be found EP 675 417, that is incorporated herein by reference.
  • toner particles with an absolute average charge corresponding to 1 fC ⁇
  • the absolute average charge of the toner particles is measured by an apparatus sold by Dr. R. Epping PES-Laboratorium D-8056 Neufahrn, Germany under the name "q-meter”. The q-meter is used to measure the distribution of the toner particle charge (q in fC) with respect to a measured toner diameter (d in 10 ⁇ m). From the absolute average charge per 10 ⁇ m (
  • the charge distribution measured with the apparatus cited above, is narrow, i.e. shows a distribution wherein the coefficient of variability ( ⁇ ), i.e. the ratio of the standard deviation to the average value, is equal to or lower than 0.33.
  • ⁇ coefficient of variability
  • the toner particles used in a device according to the present invention have an average volume diameter (dv50) between 1 and 20 ⁇ m more preferably between 3 and 15 ⁇ m. More detailed descriptions of toner particles, as mentioned above, can be found in EP-A-675 417.
  • a DEP device making use of the above mentioned marking toner particles can be addressed in a way that enables it to give black and white. It can thus be operated in a "binary way", useful for black and white text and graphics and useful for classical bilevel halftoning to render continuous tone images.
  • a DEP device is especially suited for rendering an image with a plurality of grey levels.
  • Grey level printing can be controlled by either an amplitude modulation of the voltage V2 applied on the control electrodes 106a or by a time modulation of V2. By changing the duty cycle of the time modulation at a specific frequency, it is possible to print accurately fine differences in grey levels. It is also possible to control the grey level printing by a combination of an amplitude modulation and a time modulation of the voltage V3, applied on the control electrode.
  • the printhead structure The printhead structure.
  • a printhead structure was made from a polyimide film of 50 ⁇ m thickness (106c), single sided coated with a 5 ⁇ m thick copper film.
  • 106c polyimide film of 50 ⁇ m thickness
  • rectangular control electrodes (106a) being 220 ⁇ m large (measured in the direction parallel with the edge) were arranged at a linear pitch of 300 ⁇ m.
  • Each of said control electrodes was connected over 2 M ⁇ resistors to a HV 507 (trade name) high voltage switching IC, commercially available through Supertex, USA, that was powered from a high voltage power supply.
  • a 110 ⁇ m thick polyurethane (110) was present, said polyurethane coating making physical frictional contact with the charged toner particles on the sleeve of the toner delivery means.
  • a 230 ⁇ m thick adhesive coating (not shown in the figures) and 175 ⁇ m thick polyester sheet was present (115).
  • the printhead structure was mounted on a PVC-frame so that 8 mm (FL) of said edge electrode remained flexible and bendable.
  • the toner delivery means The toner delivery means
  • the toner delivery means was a commercially available toner cartridge comprising non magnetic mono component developer, the COLOR LASER TONER CARTRIDGE MAGENTA (M3760GIA), for the COLOR LASER WRITER (Trade names of Apple Computer, USA).
  • the toner bearing surface is the surface of an aluminium roller (112), whereon tone surface was changed as indicated in table 1. The results of the measurement of the printing density is also included in table 1.
  • a printhead structure was made from a polyimide film of 50 ⁇ m thickness (106c), single sided coated with a 5 ⁇ m thick copper film.
  • 106c polyimide film of 50 ⁇ m thickness
  • rectangular control electrodes (106a) being 220 ⁇ m large (measured in the direction parallel with the edge) were arranged at a linear pitch of 300 ⁇ m.
  • Each of said control electrodes was connected over 2 M ⁇ resistors to a HV 507 (trade name) high voltage switching IC, commercially available through Supertex, USA, that was powered from a high voltage power supply.
  • the 110 ⁇ m thick polyurethane coating was used as self-regulating spacer means (110).
  • a back electrode was present behind the paper whereon the printing proceeded, the distance between the back electrode (105) and the back side of the printhead structure (i.e. control electrodes (106a)) was set to 1000 ⁇ m and the paper travelled at 200 cm/min.
  • a printhead structure was made from a polyimide film of 50 ⁇ m thickness, single sided coated with a 5 ⁇ m thick copper film.
  • rectangular control electrodes being 220 ⁇ m large (measured in the direction parallel with the edge) were arranged at a linear pitch of 300 ⁇ m.
  • Each of said control electrodes was connected over 2 M ⁇ resistors to a HV 507 (trade name) high voltage switching IC, commercially available through Supertex, USA, that was powered from a high voltage power supply.
  • the shield electrode reached to the very edge of the printhead structure, the paper travelled at 200 cm/min, i.e. the printing speed is 200 cm/min.
  • example 11 the same printing device was used except that the continuous copper shield electrode with polyamide spacer means was located at 500 ⁇ m away from the edge of the control electrodes.
  • the printing speed was 100 cm/min.
  • example 12 the same printing device was used except that the continuous copper shield electrode with polyamide spacer means was located at 1000 ⁇ m away from the edge of the control electrodes.
  • the printing speed was 40 cm/min
  • Example 13 Example 13 was repeated except for the printing speed, which was now set at 100 cm/min.
  • Example 14 Example 14 was repeated except for the printing speed, which was now set at 200 cm/min.
  • Example 15 Example 15 was repeated except for the thickness of the spacing means, which was now 200 ⁇ m instead of 800 ⁇ m.
  • example 14 was repeated except for the thickness of the spacing means, which was now 200 ⁇ m instead of 800 ⁇ m.
  • the examples 12 to 16 showed not only a low background density (D min ), but also a wide density range. When comparing the density range that was printed in examples 12 to 16 with the density range printed in example 3, it was found that the density range printed in examples 12 to 16 was larger.
  • edge electrode on a rigid frame without spacer means towards the toner delivery means, it is possible to enhance the resolution of the device by making an edge electrode having separate sets of control electrodes as depicted in figure 3e, or it is possible to enhance the effect of the control electrodes over a larger area by staggering and overlapping said sets of control electrodes either in different planes as depicted in figure 3d or in the same plane as depicted in figure 4.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
EP98202302A 1997-08-07 1998-07-08 Appareil d'impression électrostatique directe comprenant une électrode de bord et un champ de courant alternatif sur la surface des moyens d'alimentation en toner Withdrawn EP0895867A3 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP98202302A EP0895867A3 (fr) 1997-08-07 1998-07-08 Appareil d'impression électrostatique directe comprenant une électrode de bord et un champ de courant alternatif sur la surface des moyens d'alimentation en toner

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP97202443 1997-08-07
EP97202443 1997-08-07
EP98202302A EP0895867A3 (fr) 1997-08-07 1998-07-08 Appareil d'impression électrostatique directe comprenant une électrode de bord et un champ de courant alternatif sur la surface des moyens d'alimentation en toner

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EP0895867A2 true EP0895867A2 (fr) 1999-02-10
EP0895867A3 EP0895867A3 (fr) 1999-03-31

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1193070A3 (fr) * 2000-09-29 2003-01-22 Seiko Epson Corporation Appareil de formation d'images
EP1296203A1 (fr) * 2001-08-28 2003-03-26 Seiko Epson Corporation Appareil de formation d'image comprenant un dispositif d'impression électrostatique directe sur une plaquette à circuit imprimé élastique dotée de moyen de réglage pour égaliser l'épaisseur de la couche de développateur déposée sur un rouleau
US7524014B2 (en) * 2005-09-06 2009-04-28 Seiko Epson Corporation Image forming apparatus and image forming method

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US3689935A (en) 1969-10-06 1972-09-05 Electroprint Inc Electrostatic line printer
US4478510A (en) 1981-12-16 1984-10-23 Canon Kabushiki Kaisha Cleaning device for modulation control means
US4491855A (en) 1981-09-11 1985-01-01 Canon Kabushiki Kaisha Image recording method and apparatus
US4755837A (en) 1986-11-03 1988-07-05 Xerox Corporation Direct electrostatic printing apparatus and printhead cleaning structure therefor
US4876561A (en) 1988-05-31 1989-10-24 Xerox Corporation Printing apparatus and toner/developer delivery system therefor
US4903050A (en) 1989-07-03 1990-02-20 Xerox Corporation Toner recovery for DEP cleaning process
US5036341A (en) 1987-12-08 1991-07-30 Ove Larsson Production Ab Method for producing a latent electric charge pattern and a device for performing the method
US5095322A (en) 1990-10-11 1992-03-10 Xerox Corporation Avoidance of DEP wrong sign toner hole clogging by out of phase shield bias

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JPH0361960A (ja) * 1989-07-31 1991-03-18 Ricoh Co Ltd 画像記録装置
US5038159A (en) * 1989-12-18 1991-08-06 Xerox Corporation Apertured printhead for direct electrostatic printing
JP3271816B2 (ja) * 1993-03-09 2002-04-08 ブラザー工業株式会社 画像形成装置
EP0769384A3 (fr) * 1995-10-18 1997-07-30 Hewlett Packard Co Impression à l'éjection de toner
DE69522948T2 (de) * 1995-12-18 2002-04-25 Agfa-Gevaert N.V., Mortsel Vorrichtung zum direkten elektrostatischen Drucken mit einer Druckkopfstruktur mit Schlitzöffnungen

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Publication number Priority date Publication date Assignee Title
US3689935A (en) 1969-10-06 1972-09-05 Electroprint Inc Electrostatic line printer
US4491855A (en) 1981-09-11 1985-01-01 Canon Kabushiki Kaisha Image recording method and apparatus
US4478510A (en) 1981-12-16 1984-10-23 Canon Kabushiki Kaisha Cleaning device for modulation control means
US4755837A (en) 1986-11-03 1988-07-05 Xerox Corporation Direct electrostatic printing apparatus and printhead cleaning structure therefor
US5036341A (en) 1987-12-08 1991-07-30 Ove Larsson Production Ab Method for producing a latent electric charge pattern and a device for performing the method
US4876561A (en) 1988-05-31 1989-10-24 Xerox Corporation Printing apparatus and toner/developer delivery system therefor
US4903050A (en) 1989-07-03 1990-02-20 Xerox Corporation Toner recovery for DEP cleaning process
US5095322A (en) 1990-10-11 1992-03-10 Xerox Corporation Avoidance of DEP wrong sign toner hole clogging by out of phase shield bias

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1193070A3 (fr) * 2000-09-29 2003-01-22 Seiko Epson Corporation Appareil de formation d'images
EP1296203A1 (fr) * 2001-08-28 2003-03-26 Seiko Epson Corporation Appareil de formation d'image comprenant un dispositif d'impression électrostatique directe sur une plaquette à circuit imprimé élastique dotée de moyen de réglage pour égaliser l'épaisseur de la couche de développateur déposée sur un rouleau
US6817701B2 (en) 2001-08-28 2004-11-16 Seiko Epson Corporation Image forming apparatus
US7524014B2 (en) * 2005-09-06 2009-04-28 Seiko Epson Corporation Image forming apparatus and image forming method

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