EP0811894A1 - Verfahren zum Drucken von Information auf Aufzeichnungsträgern mit Sicherheitsmerkmalen - Google Patents

Verfahren zum Drucken von Information auf Aufzeichnungsträgern mit Sicherheitsmerkmalen Download PDF

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Publication number
EP0811894A1
EP0811894A1 EP97201643A EP97201643A EP0811894A1 EP 0811894 A1 EP0811894 A1 EP 0811894A1 EP 97201643 A EP97201643 A EP 97201643A EP 97201643 A EP97201643 A EP 97201643A EP 0811894 A1 EP0811894 A1 EP 0811894A1
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EP
European Patent Office
Prior art keywords
substrate
back electrode
toner
printing
toner particles
Prior art date
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Withdrawn
Application number
EP97201643A
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English (en)
French (fr)
Inventor
Guido Desie
Leon Vermeulen
Michel Boulonne
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Agfa Gevaert NV
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Agfa Gevaert NV
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Publication date
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Priority to EP97201643A priority Critical patent/EP0811894A1/de
Publication of EP0811894A1 publication Critical patent/EP0811894A1/de
Withdrawn legal-status Critical Current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
    • G03G15/346—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 by modulating the powder through holes or a slit
    • 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

  • the present invention relates to an apparatus for Direct Electrostatic Printing (DEP). It relates in particular to a DEP device especially useful for printing on substrates incorporating security features.
  • DEP Direct Electrostatic Printing
  • Thermosublimation printing is not well suited for printing on rough surfaces and mostly a dye acceptor layer is necessary on the substrate.
  • Thermosublimation printing that proceeds by thermally evaporating solid dye or pigments, is not very well suited for security printing because of the dyes, usually used, are not sufficiently waterfast and lightfast, and are characterised by high bleeding, leading to documents with a restricted shelf life.
  • Thermosublimation printing does thus not offer an adequate possibility for printing on security paper.
  • Ink-jet printing offers at first sight interesting possibilities for printing on paper with a very rough surface, but is not very well suited for printing security documents.
  • the dyes or pigments, usually used in ink-jet printing are not sufficiently waterfast and lightfast to be used in security documents.
  • an ink-receiving layer is necessary on the substrate.
  • electro(photo)graphic and Direct Electrostatic Printing are preferred non-impact printing methods for security printing.
  • the advantage of these methods is that they use pigmented and/or dyed toner particles that are fused to the substrate, and that in the preparation of said toner particles the chemical structure of the pigments or dyes (chemical structure defining largely the water- and lightfastness) that are used is not very critical.
  • the chemical structure of the pigments or dyes (chemical structure defining largely the water- and lightfastness) that are used is not very critical.
  • toner particles a wide range of different pigments and dyes can be used. It is, e.g., possible to incorporate nacreous, iridescent or interference pigments, etc, in the toner particles, without interfering with the usefulness of this toner particles in the printing methods.
  • an image is first formed on a latent image bearing member and then transferred to a substrate, which in this case is a security paper with a rough surface.
  • the transferring step is still a contact step and therefore the image of even density patches on the substrate, having a rough substrate or comprising watermarks, is not very faithful.
  • DEP has the advantage to be a real non-impact method and is therefore the preferred method for printing on security paper having a rough surface.
  • the DEP method is a well known printing method
  • a DEP printing device is disclosed in e.g. US-P 3,689,935.
  • This document discloses an electrostatic line printer having a multi-layered particle modulator or printhead structure comprising :
  • Selected 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 (toner source) and a receiving member support 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 member substrate, interposed in the modulated particle stream.
  • the receiving member 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 (toner source) and the control electrode may face the receiving member substrate.
  • toner delivery means will be used to indicate said means for delivering toner particles.
  • Direct Electrostatic Printing proved to be an excellent printing method for printing on a substrate comprising security features.
  • the printing had to proceed on substrates comprising a watermark, fibres (natural, metallic, polymeric fibres) in the bulk of the substrate giving rise to lager thickness variations in the substrate, then DEP printing proved to be superior to classical electrostatic printing.
  • the printing could proceed by any DEP device where the distance L in ⁇ m between the surface of the printing structure facing the back electrode (back side of the printhead structure) and the surface of the back electrode facing the printhead structure (front side of the back electrode) was large enough to let the substrate comprising security features pass.
  • a distance L being at least 1.5 times larger than the largest thickness (T in ⁇ m) of the substrate yielded the better results than when the distance L was lower than 1.5 times the largest thickness of the substrate.
  • L > 2T.
  • the maximum thickness T of substrates comprising security features can easily reach 500 ⁇ m, which includes that L is then preferably at least 750 ⁇ m, or more preferably at least 1000 ⁇ m. It was found that printing quality, in terms of sharpness, resolution and fidelity of line reproduction, in DEP devices wherein the distance L between the printhead structure and the back electrode was larger than 500 ⁇ m was became vary acceptable when between said back electrode and said toner delivery means a DC potential difference (DC TB ) such that (DC TB
  • a DEP device could especially well be used for printing on a substrate comprising a watermark and/or wherein thickness variations between 10 % and 60 % of the average thickness of the substrate are present. Even when the thickness variations were form 10 % up to 80 % and even from 10 % up to 90 % even density printing was still possible.
  • the substrates carrying security features can be any substrate known in the art of security printing, e.g. paper, cardboard, plastic, etc.
  • the security features can be any known security feature known in the art, e.g. watermarks, incorporated fibres, both metallic and non-metallic, micro-relief printings, etc. Typical security papers are available through Portals (Bathford) Ltd, 253 London Road East, Batheaston, Bath, Avon, England.
  • DEP Direct Electrostatic Printing
  • the means (111) for adjusting the width of spacing L, between the back electrode and the printhead structure can be any means known in the art for adjusting distances on a micrometer scale.
  • Very suitable means for adjusting the width, L are e.g. a micrometer screw, stepping motor, a system based on levers, interposition of callibrated spacers, etc.
  • the means (111) for adjusting the spacing L are shown to be operative on the back electrode (105), a DEP device wherein said means (111) for adjusting the spacing L operate on the printhead structure (106) and a DEP device wherein said means (111) for adjusting the spacing L operate on the printhead structure (106) operate both on the back electrode (105) and the printhead strucutre (106) are also within the scope of this invention.
  • the means (106a) for imagewise modulating said flow of toner particles is a complex addressable electrode structure, hereinafter called “control electrode” around apertures (107), facing, in the shown embodiment, the toner-receiving member in said DEP device.
  • the control electrode can be an individual control electrode around each individual aperture, or can be an electrode controlling the toner flow through a plurality of printing apertures.
  • the printhead structure (106), shown in figure 1, is made from a plastic insulating film, coated with a metallic film formed from a electroless deposition step on a thin layer of catalyst.
  • the printhead structure (106) comprises a complex addressable electrode structure, the "control electrode” (106a) around printing apertures (107), facing, in the shown embodiment, the toner-receiving member in said DEP device. Said printing apertures are arranged in an array structure for which the total number of rows can be chosen according to the field of application.
  • a second conductive layer is present on the other side of said plastic material, said second conductive layer being called the shield electrode layer (106b).
  • a DEP method using two electrodes (106a and 106b) on printhead 106 it is possible to implement a DEP method with different constructions of the printhead (106). It is, e.g. possible to implement a DEP method with a device having a printhead comprising only one electrode structure (the control electrode (106a) or with more electrode structures.
  • the apertures in these printhead structures can have a constant diameter, or can have a broader entrance or exit diameter.
  • the toner delivery means (101) in figure 1 comprises a container for developer (102) and a magnetic brush (103). From this magnetic brush the toner cloud (104) is formed. The formation of said toner cloud is preferably aided by an AC bias on the sleeve of the magnetic brush.
  • the toner cloud directly formed from magnetic brush (103) may originate from a mono-component or from a multi-component developer.
  • DEP device were the toner delivery means is a magnetic brush carrying a multi-component developer are described in US 5,327,169, EP-A 675 417 and JP-A 60/263962.
  • the toner delivery means in a DEP device can also comprise a toner delivery means, comprising a container for developer, a charged toner conveyer (CTC) and a magnetic brush.
  • This magnetic brush forms a layer of charged toner particles upon said charged toner conveyer and from said charged toner conveyer a toner cloud (104) is formed in the vicinity of the printing apertures (107).
  • a DEP device, wherein a toner delivery means, comprising a container for developer, a charged toner conveyer (CTC) and a magnetic brush, is used has been disclosed in e.g. EP-A 740 224.
  • a DEP device with a CTC When a DEP device with a CTC is used, it can be operated successfully when a single magnetic brush or several magnetic brushes are used in contact with a Charged Toner Conveyor (CTC) to provide a layer of charged toner on said CTC.
  • CTC Charged Toner Conveyor
  • a DEP device using a CTC as toner source When a DEP device using a CTC as toner source is used in a DEP device according to this invention, it is possible to successfully use non-magnetic mono-component developers.
  • the formation of the toner cloud can be aided by applying an AC-bias on the CTC. It is in such a device also possible to connect an additional AC-source can also be to the sleeve of the magnetic brush, aiding the application of a toner layer to the charged toner conveyer.
  • the back electrode (105) of this DEP device can also be made to cooperate 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-P 4,568,955 and US-P 4,733,256.
  • the back electrode, cooperating with the printhead structure can also comprise one or more flexible PCB's (Printed Circuit Board).
  • the substrate (109) is shown as a web. It is clear that a DEP device and method according to the present invention can as well be operated for printing substrates in sheet form.
  • V3 The value of V3 is selected, according to the modulation of the image forming signals, between the values V3 0 and V3 n , on a timebasis or grey-level basis.
  • Voltage V4 is applied to the back electrode behind the toner receiving member. In other embodiments of the present invention multiple voltages V4 0 to V4 n can be used.
  • Voltage V2 is applied to the shield electrode (106b).
  • the DEP device for printing on substrates comprising security features can in fact be any DEP device known in the art. E.g., it can be a DEP device wherein the toner cloud in the vicinity of the printhead structure is provided directly from a magnetic brush with a multi-component developer; such devices are described in US 5,327,169, EP-A 675 417 and JP-A 60/263962.
  • Other useful modifications in a DEP device for printing on substrates comprising security features are a.o. the modifications described in e.g. EP-A 780 740, EP-A 763 785, EP-A 754 557, EP-A 753 413 and EP-A 731 394.
  • a magnetic brush When a magnetic brush is used in a DEP device according to the present invention, be it in an embodiment as shown in figure 1 or be it a magnetic brush applying a layer of charged toner particles on a CTC, it is preferably of the type with stationary core and rotating sleeve.
  • 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 50 up to 250 Oe (3.98 kA/m to 19.92 kA/m).
  • 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 (d v50 ) between 10 and 300 ⁇ m, preferably between 20 and 100 ⁇ m. More detailed descriptions of carrier particles, as mentioned above, can be found in EP-A 675 417, that is incorporated herein by reference.
  • developers wherein the toner particles have an absolute average charge to mass ratio (
  • the absolute average charge to mass ratio was measured by mixing a mixture toner particles (4 to 8 % by weight) and carrier particles in a standard tumbling set-up for 10 min.
  • the developer mixture was run in the development unit (magnetic brush assembly) for 5 minutes, after which the toner particles were, via a magnetic brush assembly, applied as a monolayer of charged toner particles on a charged toner conveyer (a CTC).
  • the charge distribution, measured, as described in EP-A 675 417 is narrow, i.e. shows a distribution wherein the coefficient of variability (v), i.e. the ratio of the standard deviation to the average value, is equal to or lower than 0.33, preferably equal to or lower than 0.25.
  • v coefficient of variability
  • Means for producing toner particles with a low average charge and a narrow charge distribution have been disclosed, for positively chargeable toners in EP-B 654 152 and for negatively chargeable toners in EP-B 650 609 and EP-A 650 610. This three references are incorporated herein by reference.
  • the method for producing toners with low average charge and narrow charge distribution consists in mixing in the toner resin a compound having a volume resistivity lower than the volume resistivity of the toner resin.
  • Preferred compound having lower volume resistivity than the toner resin are onium compounds.
  • the toner particles used in a device according to the present invention have an average volume diameter (d v50 ) between 1 and 20 ⁇ m, more preferably between 3 and 15 ⁇ m.
  • 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 V3 applied on the control electrode (106a) or by a time modulation of V3. 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.
  • Printing examples were made by an apparatus using a developer, comprising toner and carrier particles, as described further on.
  • the DEP device The DEP device
  • the DEP device used is essentially a device as shown in figure 1.
  • a printhead structure (106) made from a polyimide film of 50 ⁇ m thickness, double sided coated with a 17.5 ⁇ m thick copper film.
  • the printhead structure (106) had four rows of printing apertures.
  • a common shield electrode (106b) was present on the front side of the printhead structure, facing the toner delivery means.
  • the printing apertures had an aperture width of 100 ⁇ m.
  • the width of the copper electrodes was 50 ⁇ m.
  • the rows of printing apertures were staggered to obtain an overall resolution of 254 dpi (dots per inch or dots per 25.4 mm).
  • the toner delivery means (101) comprised a stationary core/rotating sleeve type magnetic brush (103) comprising two mixing rods and one metering roller. One rod was used to transport the developer through the unit, the other one to mix toner with developer.
  • the magnetic brush assembly (103) was constituted of the so called magnetic roller, which in this case contained inside the roller assembly a stationary magnetic core, showing nine magnetic poles of 500 Gauss (0.05 T) magnetic field intensity and with an open position to enable used developer to fall off from the magnetic roller.
  • the magnetic roller contained also a sleeve, fitting around said stationary magnetic core, and giving to the magnetic brush assembly an overall diameter of 20 mm.
  • the sleeve was made of stainless steel roughened with a fine grain to assist in transport ( ⁇ 50 ⁇ m).
  • a scraper blade was used to force developer to leave the magnetic roller.
  • a doctoring blade was used to meter a small amount of developer onto the surface of said magnetic brush assembly.
  • the sleeve was rotating at 100 rpm, the internal elements rotating at such a speed as to conform to a good internal transport within the development unit.
  • the magnetic brush assembly (103) was connected to an AC power supply with a square wave oscillating field of 600 V at a frequency of 3.0 kHz with 0 V DC-offset. This AC field and the DC-offset are the voltage V1 of figure 1.
  • the toner is the toner
  • the toner used for the experiment had the following composition : 97 parts of a co-polyester resin of fumaric acid and propoxylated bisphenol A, having an acid value of 18 and volume resistivity of 5.1 x 10 16 ohm.cm was melt-blended for 30 minutes at 110° C in a laboratory kneader with 3 parts of Cuphthalocyanine pigment (Colour Index PB 15:3).
  • a resistivity decreasing substance - having the following structural formula : (CH 3 ) 3 N + C 16 H 33 Br - was added in a quantity of 0.5 % with respect to the binder. It was found that - by mixing with 5 % of said ammonium salt - the volume resistivity of the applied binder resin was lowered to 5x10 14 ⁇ .cm. This proves a high resistivity decreasing capacity (reduction factor : 100).
  • the solidified mass was pulverized and milled using an ALPINE Fliessbettarnastrahlmühle type 100AFG (tradename) and further classified using an ALPINE multiplex zig-zag classifier type 100MZR (tradename).
  • the resulting particle size distribution of the separated toner measured by Coulter Counter model Multisizer (tradename), was found to be 6.3 ⁇ m average by number and 8.2 ⁇ m average by volume.
  • the toner particles were mixed with 0.5 % of hydrophobic colloidal silica particles (BET-value 130 m 2 /g).
  • the carrier particles are of the carrier particles.
  • a macroscopic "soft" ferrite carrier consisting of a MgZn-ferrite with average particle size 50 ⁇ m, a magnetisation at saturation of 29 emu/g (36.25 ⁇ T.m 3 /kg) was provided with a polymeric silicon coating of 0.6 % by weight (w/w), with respect to the total weight of the carrier core.
  • the polymeric silicon coating comprised between 0 and 30 % by weight, with respect to the total coating, of aminosilane compounds.
  • Such carriers have been described in EP-A 650 099. The material showed virtually no remanence.
  • electrostatographic developers were prepared by mixing said mixture of toner particles and colloidal silica in a 4 to 8 % ratio (w/w) with carrier particles.
  • the tribo-electric charging or the toner-carrier mixture was performed by mixing said mixture in a standard tumbling set-up for 10 min.
  • the developer mixture was run in the development unit (magnetic brush assembly) for 5 minutes, after which the toner was sampled and the tribo-electric properties were measured, according to the methods as described herein above.
  • the aminosilane content in % by weight of the coatings of the carrier particles used to prepare the various developers, the toner concentration in % by weight, the charge to mass ratio ( ⁇ C/g) of the toner particles and the charge distribution of the toner particles as coefficient of variability ⁇ are given in table 1.
  • TABLE 1 Developer weight % aminosilane weight % toner Charge/mass in ⁇ C/g ⁇ D1 0 8 - 5.6 0.321 D2 0 5 - 7.0 0.251 D3 14 4 - 13.7 0.172 D4 30 4 - 36 0.200
  • the shield electrode (106b) was grounded : V2 0 V.
  • To the individual control electrodes an (imagewise) voltage V3 between 0 V and 300 V was applied.
  • the back electrode (105) was connected to a high voltage power supply that applied a voltage (DC TB ) such that in each printing example DC TB /L was equal to or larger than 1.
  • DC TB voltage
  • To the sleeve of the magnetic brush an AC voltage of 600 V at 3.0 kHz was applied, with a DC offset of - 50V.
  • Example 1 was repeated, except for the developer that was used, instead of developer D1, developer D2 was used.
  • Example 1 was repeated, except for the developer that was used, instead of developer D1, developer D3 was used.
  • Example 1 was repeated, except for the developer that was used, instead of developer D1, developer D3 was used.
  • Example 1 was repeated, except for DC TB , instead of being 1500 V, DC TB was 400 V, giving a DC TB /L of 0.4.
  • Example 1 was repeated, but the printing proceeded on paper comprising a water mark.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
EP97201643A 1996-06-06 1997-06-02 Verfahren zum Drucken von Information auf Aufzeichnungsträgern mit Sicherheitsmerkmalen Withdrawn EP0811894A1 (de)

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EP96201580 1996-06-06
EP96201580 1996-06-06
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5880760A (en) * 1996-06-06 1999-03-09 Agfa-Gevaert Method and device for printing information on substrates having security features
EP1091264A1 (de) * 1999-10-04 2001-04-11 Agfa-Gevaert N.V. Direkte elektrostatische Druckvorrichtung, wo geladene Tonerteilchen auf einem in Kontakt mit dem Tonerabgabeteil eines nichtmagnetisches Einkomponenten Entwicklungssystems Tonertransportgerät aufgetragen werden

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4626459A (en) * 1986-09-09 1986-12-02 Minnesota Mining And Manufacturing Company Mounting structure for security strip
US5257046A (en) * 1992-08-31 1993-10-26 Xerox Corporation Direct electrostatic printing with latent image assist
US5374949A (en) * 1989-11-29 1994-12-20 Kyocera Corporation Image forming apparatus
EP0675417A1 (de) * 1994-03-29 1995-10-04 Agfa-Gevaert N.V. Verfahren und Vorrichtung für direktes elektrostatisches Drucken (DEP)
US5495273A (en) * 1993-03-02 1996-02-27 Brother Kogyo Kabushiki Kaisha Image recording apparatus having spacer between aperture electrode and opposing electrode
EP0763785A1 (de) * 1995-09-14 1997-03-19 Agfa-Gevaert N.V. Eine direkte elektrostatische Druckeinrichtung, die einen Gasstrom zur Bereitstellung einer Entwicklerwolke benutzt

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4626459A (en) * 1986-09-09 1986-12-02 Minnesota Mining And Manufacturing Company Mounting structure for security strip
US5374949A (en) * 1989-11-29 1994-12-20 Kyocera Corporation Image forming apparatus
US5257046A (en) * 1992-08-31 1993-10-26 Xerox Corporation Direct electrostatic printing with latent image assist
US5495273A (en) * 1993-03-02 1996-02-27 Brother Kogyo Kabushiki Kaisha Image recording apparatus having spacer between aperture electrode and opposing electrode
EP0675417A1 (de) * 1994-03-29 1995-10-04 Agfa-Gevaert N.V. Verfahren und Vorrichtung für direktes elektrostatisches Drucken (DEP)
EP0763785A1 (de) * 1995-09-14 1997-03-19 Agfa-Gevaert N.V. Eine direkte elektrostatische Druckeinrichtung, die einen Gasstrom zur Bereitstellung einer Entwicklerwolke benutzt

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5880760A (en) * 1996-06-06 1999-03-09 Agfa-Gevaert Method and device for printing information on substrates having security features
EP1091264A1 (de) * 1999-10-04 2001-04-11 Agfa-Gevaert N.V. Direkte elektrostatische Druckvorrichtung, wo geladene Tonerteilchen auf einem in Kontakt mit dem Tonerabgabeteil eines nichtmagnetisches Einkomponenten Entwicklungssystems Tonertransportgerät aufgetragen werden

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