Security Strip for a Security Paper for Currency & Banknotes and Method

Europäisches Patentamt

(19) European Patent Office Office européen des brevets (11) EP 0 536 855 B2

(12) NEW EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int. Cl.7: B42D 15/00, B41M 3/14 of the opposition decision: 12.04.2000 Bulletin 2000/15

(45) Mention of the grant of the patent: 11.12.1996 Bulletin 1996/50

(21) Application number: 92203692.6

(22) Date of filing: 24.02.1987

(54) Security strip for a security paper for currency & banknotes and method for producing a security strip Sicherheitsstreifen für ein Sicherheitspapier für Wertpapiere und Banknoten und Verfahren zu dessen Herstellung Ruban de sécurité pour papier de sécurité pour papiers fiduciaires et billets de banque et procédé de fabrication d'un ruban de sécurité

(84) Designated Contracting States: (56) References cited: CH DE FR GB IT LI NL SE EP-A- 0 070 172 EP-A- 0 105 969 EP-A- 0 181 770 DE-A- 1 446 851 (43) Date of publication of application: DE-A- 2 107 113 DE-A- 2 205 428 14.04.1993 Bulletin 1993/15 GB-A- 237 828 GB-A- 1 486 079 GB-A- 2 103 669 US-A- 1 929 828 (62) Document number(s) of the earlier application(s) in US-A- 4 552 617 US-A- 4 652 015 accordance with Art. 76 EPC: 87102596.1 / 0 279 880 • DATABASE WPIL Week 8446, Derwent Publications Ltd., London, GB; AN 84282244 & (73) Proprietor: CRANE & CO., INC. AU-A-1 793 283 (AQUINO) Dalton Massachusetts 01226 (US) • GB-A-J19963 (JULES GERNAERT) • Department of the Treasury, Bureau of Inventor: Crane, Timothy T. (72) Engraving and Printing, Washington, D.C. 20228, Windsor, Massachusetts 01226 (US) BEP Specification for Paper: Distinctive, Web, with security threads, published 1984, pp 1-8 (74) Representative: Williams, John Francis et al Remarks: WILLIAMS, POWELL & ASSOCIATES The file contains technical information submitted 4 St Paul's Churchyard after the application was filed and not included in London EC4M 8AY (GB) this specification EP 0 536 855 B2 Printed by Xerox (UK) Business Services 2.16.7 (HRS)/3.6 12EP 0 536 855 B2

Description security device within security paper by dissolving the security device carrier substrate and allowing the secu- BACKGROUND OF THE INVENTION rity device to be visually accessed from one side of the security paper. [0001] Methods are currently available for deploying 5[0006] All the aforementioned methods for incorpo- a thin strip of clear material such as polyester film within rating security devices within the security paper allow paper during the papermaking process. If the film is for visible access to the presence of the security device used as a security thread and is first micro-printed prior by means of the unaided eye. The Williams approach to dispensation during the papermaking process, the could lead an observer to believe that a blurred line on resulting paper then contains a legible code that is legi- 10 the surface of the security paper, for example, is a suffi- ble in transmitted light. With papers of the substance cient indication of authenticity without requiring that the and thickness used for currency and banknotes, the paper be held up to transmitted light for actual verifica- code is also visible under reflected light. The purpose of tion. The earlier security device also caused the secu- printed security threads is to deter a potential forger rity paper to exhibit an increased thickness in the vicinity since the coded indicia on the thread is buried within the 15 of the device compared to the thickness of the paper paper and cannot be duplicated by surface printing itself. This increased thickness or "bulge" line can be techniques. The authenticity of such a document can be duplicated by a skilled forger to lead the observer to readily verified by comparing the appearance of the believe that a security device is actually present, without security thread under reflected light against its appear- further examination. ance in transmitted light. It is the reflected light appear- 20 [0007] When an unprinted metallized plastic thread ance that is most relied upon by the public when such as described within the aforementioned patent to handling currency and banknotes in general circulation. Williams is used as a security thread, the optical and The reflected light appearance, however, does not electrical properties of the thread can be used for auto- directly reveal the presence of the printing that is com- matic verification by determining optical variations pletely legible in transmitted light. In fact, the nondistinct 25 across the paper as well as by standard electronic metal muted line of the security thread that is conspicuous at detection techniques. It has been determined, however, the surface of the currency and banknotes becomes the that the optical properties of such a metallized thread distinctive feature in the eyes of the general public. can be duplicated to some extent by means of a pale but [0002] The inclusion of the security device within opaque line printed on the surface of the paper in the the body of the security paper now requires sophisti- 30 vicinity of where the security thread would be located. A cated papermaking machinery which is not available to dull pencil line may also fool the unskilled observer as to forgers. One method of incorporating the security the presence of a buried security thread. device is described within U.S. patent 3,880,706 to Wil- [0008] For reliable verification, the currency or ban- liams, wherein the security device is sandwiched knote must be held up to a light source to reveal the between two layers of formed paper midway during the 35 coded indicia on the security thread that make a secu- papermaking process. rity thread virtually impossible to forge. The nondistinc- [0003] An opaque item embedded within security tive line that is the visible surface manifestation of the paper is also described as early as the issue dates of embedded security thread under reflected light is easily U.S. patents 210,089; 964,014; and 1,929,828. It is simulated also by a variety of printing processes. believed that the two ply insertion approach disclosed 40 [0009] Earlier attempts at printing on plastic strips within these patents deterred feasibility for use within and embedding the strips within the paper have not currency paper, since the two ply papers could conceiv- heretofore proved feasible since the ink used to form the ably be replicated by laminating thin sheets of counter- printed information that was legible under transmitted feit paper without requiring a sophisticated light also allowed the information to become legible papermaking machine. The simplicity in the configura- 45 under reflected light. The public could then rely upon the tion and design of the proposed security items were presence of the printed matter solely under reflected such that a forger could replicate them without a great light, which printing is easily replicated by counterfeit deal of skill or expense. means. [0004] Another method of incorporating the security [0010] One way to ensure that the public does not device within the security paper comprises pressing the 50 come to rely on such an easily simulated security thread device within the wet paper fibers while the fibers are characteristic is to manufacture currency and banknote unconsolidated and pliable as taught by U.S. patent paper containing a security thread that is virtually invis- 4,534,398 to Timothy Crane, which patent is incorpo- ible under reflected light with no manifestation on the rated herein for purposes of reference. In this method surface of the currency or banknote that such a security the security device is visible from one surface of the 55 thread is present. This two-fold test of authentication, security paper for visual verification. namely, legible under transmitted light and invisible [0005] U.S. patent 4,552,617 also in the name of under reflected light, has heretofore not been met by Timothy Crane describes a method of incorporating a any of the earlier noted devices.

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[0011] US-A-4,552,617 discloses a system for Figure 2 is a side view in partial section of a four- embedding into paper security indicia, which includes drenier papermaking machine with a funnel tube for providing a soluble carrier substrate in strip form with introducing the security device from a continuous micro-coded information. The strip is inserted into the strip within the paper fibers; fibres used for forming paper during the paper-making 5Figure 3 is a side view in partial section of a cylinder process, such that the strip dissolves to leave the micro- type papermaking machine adapted for inserting coded information intact as security indicia within the the security device from a continuous strip within paper. the paper fibers; [0012] EP-A-0,181,770 discloses an optical inter- Figure 4 is an enlarged top perspective view of a ference authenticating device which includes a polyes- 10 part of an aluminized polyester security device strip ter film substrate and at least two coatings thereon, one depicted in Figures 2 and 3 after a clear protective being radiation absorbing so as to be selectively overcoat has been applied to the aluminized print; removed by an infrared laser beam after being depos- Figure 5 is a top perspective view of an aluminized ited on the substrate by a method of vapour deposition. polyester security device film with a clear protective [0013] GB-A-2,103,669 discloses a security device 15 overcoat applied to the area where indicia is to be in the form of a diffractor grating structure applied to a retained and after an etchant solution has been dissolvable carrier web. applied producing a soluble aluminum salt in the [0014] The purpose of this invention therefore, is to unprotected area; provide a method for incorporating a security thread Figure 6 is a top perspective view of the security bearing printed information within security paper that is 20 device film of Figure 5 after the etchant solution has easily readable in transmitted light but virtually undetec- been applied and the soluble aluminum salt has table when it is viewed under reflected light. A further been removed; and purpose of this invention is to provide the printed infor- Figure 7 is a side sectional view of the security mation at a specific location within the security paper device of Figure 6 embedded within paper formed and to economically produce the paper at high speeds 25 within the papermaking machines depicted in Fig- using modern manufacturing techniques. ures 2 and 3 according to the invention. [0015] According to an aspect of the present inven- tion, there is provided a security strip as specified in DESCRIPTION OF THE PREFERRED EMBODIMENT claim 1. [0016] According to another aspect of the present 30 [0020] The security paper of the invention finds invention, there is provided a method of producing a application in the form of a banknote or currency such security strip as specified in claim 5. as the United States Federal Reserve note 10 depicted [0017] The invention thus comprises the encoding in Figure 1 as consisting of a rectangular sheet of paper of printed information onto a strip of clear plastic film 7 with a portrait 6 of a former United States President which is later incorporated within the paper during the 35 along with a numerical designation 5 of the value of the paper-making process. The printed information can be note. A plastic strip 11 is embedded within the paper in visually read or machine detected. The methods of a manner to be described below in some detail. The detection include differences in transmission optical strip extending in the direction defined by the parallel density, differences in capacitance, and variations in the dotted lines is not readily visible on the surface of the electrical current within a tuned resonance circuit. 40 paper under reflected illumination to the unaided eye. [0018] The encoded information is confined within a The strip itself has a planar configuration that is not dis- narrow band on the plastic film which can be accurately cernible by touch, unlike the security threads used located within currency, banknote or security paper within some European currency, that slightly distorts the without interfering with the speed of modern paper man- surface of the paper and can actually be felt by gently ufacturing equipment. In one embodiment, the printed 45 rubbing the paper between one's fingers. Although the information is a legible phrase, the letters of which are security threads are difficult to spot in new currency comprised of vacuum metallized aluminum having a under reflected light, the presence of the earlier security thickness of 0.03-0.04 µm (300-400 angstroms). thread becomes manifested by the blurred outlines of the thread apparently caused by repeated handling of BRIEF DESCRIPTION OF THE DRAWINGS 50 the currency. A careless teller or cashier, for example, could be fooled by a carefully drawn soft pencil line in [0019] the same location one would expect to detect the secu- rity thread. The planar configuration of the plastic strip Figure 1 is a plan view of a banknote incorporating 11 ensures that its presence remains undetected under a security device according to the invention; 55 reflected light even after long periods of continued use. Figure 1a is an enlarged plan view of the banknote When the bill is held up to a source of transmitted light of Figure 1 depicting a legible phrase of the security or passed over a "light table" consisting of a transparent device viewed in transmitted light; or translucent surface over a strong source of light, the

3 56EP 0 536 855 B2 security indicia 12 shown in Figure 1a becomes readily tic NaOH solution, it is noted that fine printing is best visible. protected from becoming dissolved by the NaOH solu- [0021] The concept of embedding a security device tion when the contact with the NaOH solution is as brief within the paper fibers of a fourdrenier papermaking as possible. The Sodium aluminate salt formed by machine is described within the aforementioned U.S. 5reacting the unprotected aluminium with the NaOH patent to Timothy Crane and one such fourdrenier solution is gently washed away from the surface by machine is depicted at 16 in Figure 2. application of a clear water rinse. [0022] The headbox 3 contains a slurry 15 consist- [0025] The same length of security strip is shown at ing of a mixture of cellulosic fibers and fillers, all in a 30B in Figure 6 with all the aluminium removed from the water vehicle illustrated by the dashed lines 8. The 10 surface of the polyester film 28 and exhibiting a planar security strip 13 is fed continuously from a reel (not polyester surface 28A. The letters 31 remain intact on shown) through a tube 14 into the slurry at the dis- the surface after the dissolved metal is removed. Other charge outlet 2 of the headbox onto the fourdrenier wire methods of applying the letters to the surface can also 17. The fibers continuously surround the security strip be employed without departing from the scope of this as the slurry proceeds along the wire becoming dewa- 15 invention as defined in the appended claims. Legible tered and consolidated during the papermaking proc- printing or bar type optically readable codes can be ess. Once the paper has reached a final stage of directly hot stamped onto the polyester or applied via dewatering, it is then passed through heated rollers for selective metallization using a mask or template in the pressing and drying into a final paper product. The posi- vacuum metallizer. The security paper 25 shown in Fig- tion of the tube 14 relative to the lateral extent of the 20 ure 3 containing the security strip 13 embedded after wire 17 accurately determines the predetermined loca- heating and pressing is depicted at 25' in Figure 7. The tion of the security strip within the finished paper prod- paper fibers 27 completely surround the security strip uct. and prevent visual access to the security strip from [0023] The concept of embedding a security device either surface of the security paper. It is noted that the within the paper fibers of a cylinder mold papermaking 25 thickness of the paper is uniform and there is no bulge machine is also described within the aforementioned in the vicinity of the paper containing the security strip. patent to Timothy Crane and one such cylinder mold This is an important feature of the invention for the rea- machine is shown at 18 in Figure 3. The slurry 15 con- sons discussed earlier. Although the metal letters 31 on tains the same composition of paper fibers 26 in water the plastic strip 11 are embedded within the paper fib- 27 as that described earlier with reference to the slurry 30 ers, these letters are readily visible when light is trans- on Figure 2. The security strip is fed from a reel (not mitted through the security paper from one surface and shown) over a guide roll 19 onto the screen 22 of the the security paper is viewed from the opposite surface cylinder 20 after some of the paper fibers have been when the thickness of the metal is between 0.03-0.04 gathered on the screen as indicated generally at 26'. µm (300-400 angstroms) and the thickness of the paper The consolidated paper fibers containing the security 35 is from 0.1-0.15 mm (4-6 thousandths of an inch). strip is shown at 25 and is picked up from the cylinder by [0026] It has thus been shown that a planar plastic a felt 23 traveling in the indicated direction over a guide film bearing either machine readable code or visually roll 24 onto a couch roll 21 and back in the opposite accessible letters can be embedded at a predetermined direction to the heating and pressing stages of the location within the currency and banknote paper for papermaking process to form the finished security 40 authentication in transmitted light. The code is invisible paper. to the unaided eye under reflected light when viewed [0024] A length 30 of the security strip 13 is shown from either surface. in Figure 4 to consist of a polyester film 28 overcoated with a vacuum deposited aluminum layer 29 which Claims defines a planar aluminum coated surface 29A. The let- 45 ters 31 spelling "CRANE", are printed onto the alumi- 1. A security strip suitable for incorporation within a num surface by means of a caustic resistant ink varnish. security paper, comprising a clear plastic strip (11, When an acid soluble metal such as tin is deposited on 28) having indicia (12) which are readable with the the polyester film, an acid resistive ink varnish is used to unaided eye, said indicia (12) being defined by print the letters. The same length of security strip is 50 metal deposits (31) on the strip (28) produced by a shown at 30A in Figure 5 with the unprotected area of process involving selective metallization by directly the aluminum coated surface 29A covered with a plural- hot stamping onto the strip or using a mask or tem- ity of crosses 32 to indicate the aluminum metal that plate in a vacuum metalliser, or by metallization and must be removed by contact with a caustic solution of selective demetallisation by chemical etching, or by NaOH in water. The caustic resistant ink varnish pro- 55 other metallization methods excluding directly print- tects the metal surface under the varnish from contact ing metal inks onto the plastic surface. with the caustic. Although the varnish is effective in pre- venting the metal from becoming dissolved by the caus- 2. A security strip as claims in claim 1, wherein said

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metal deposit has a thickness of 0.03-0.04 µm (300 5. Verfahren zur Herstellung eines Sicherheitsstrei- to 400 angstroms). fens zur Einarbeitung in ein Sicherheitspapier, wel- cher Streifen einen klaren Kunststoffstreifen (11, 3. A security strip as claimed in any preceding claim, 28) umfaßt mit Kennzeichnungen (12), welche mit wherein said indicia are numeric characters, alpha- 5dem unbewaffneten Auge lesbar sind, welche betic characters or bar codes. Kennzeichnungen (12) durch Metallabscheidungen (31) auf dem Streifen (28) definiert sind, welche 4. A security strip as claimed in any preceding claim, Metallabscheidungen durch ein Verfahren aufge- wherein said indicia are confined within a band bracht werden, welches eine selektive Metallisie- along the strip which band is spaced at each edge 10 rung durch direktes Heißprägen auf den Streifen from the edges of the strip. oder die Verwendung einer Maske oder Schablone in einer Vakuum-Metallisiervorrichtung, oder durch 5. A method of producing a security strip suitable for Metallisierung und selektive Demetallisierung incorporation within a security paper, which strip durch chemisches Ätzen, oder durch andere Metal- comprises a clear plastic strip (11, 28) having indi- 15 lisierungsmethoden ausschließlich des direkten cia (12) which are readable with the unaided eye, Druckens von Metalltinten auf die Kunststoffoberflä- said indicia (12) being defined by metal deposits che umfaßt. (31) on the strip (28), wherein said metal deposits are applied by a process involving selective metalli- Revendications zation by directly hot stamping onto the strip or 20 using a mask or template in a vacuum metalliser, or 1. Un ruban de sécurité apte à être incorporé à l'inté- by metallization and selective demetallisation by rieur d'un papier fiduciaire, comprenant une bande chemical etching, or by other metallization methods de matière plastique translucide (11, 28) portant excluding directly printing metal inks onto the plas- des indicateurs (12) qui sont lisibles à l'oeil nu sans tic surface. 25 assistance, lesdits indicateurs (12) étant définis par des dépôts métalliques (31) sur la bande (28) pro- Patentansprüche duits par un processus qui implique une métallisa- tion sélective par estampage direct à chaud sur la 1. Sicherheitsstreifen zur Einarbeitung in ein Sicher- bande ou par utilisation d'un masque ou d'un gaba- heitspapier, umfassend einen klaren Kunststoff- 30 rit dans un dispositif de métallisation sous vide, ou streifen (11, 28) mit Kennzeichnungen (12), welche par métallisation et démétallisation sélective par mit dem unbewaffneten Auge lesbar sind, welche gravure chimique ou par d'autres procédés de Kennzeichnungen (12) durch Metallabscheidungen métallisation, à l'exclusion d'une impression directe (31) auf dem Streifen (28) definiert sind, die durch d'encres métalliques sur la surface de matière plas- ein Verfahren erzeugt worden sind, welches eine 35 tique. selektive Metallisierung umfaßt durch direktes Heißprägen auf den Streifen oder die Verwendung 2. Un ruban de sécurité selon la revendication 1, dans einer Maske oder Schablone in einer Vakuum- lequel l'épaisseur dudit dépôt métallique est de Metallisiervorrichtung, oder durch Metallisierung 0,03 à 0,04 µm (300 à 400 angstroems). und selektive Demetallisierung durch chemisches 40 Ätzen, oder durch andere Metallisierungsmethoden 3. Un ruban de sécurité selon une revendication pré- ausschließlich des direkten Druckens von Metalltin- cédente quelconque dans lequel lesdits indicateurs ten auf die Kunststoffoberfläche. sont des caractères numériques, des caractères alphabétiques ou des codes à barres. 2. Sicherheitsstreifen nach Anspruch 1, worin die 45 Metallabscheidung eine Dicke von 0,03-0,04 µm 4. Un ruban de sécurité selon une revendication pré- (300 bis 400 Ångström) aufweist. cédente quelconque dans lequel lesdits indicateurs sont confinés à l'intérieur d'une bande le long dudit 3. Sicherheitsstreifen nach irgendeinem der vorherge- ruban, bande qui est espacée des bords du ruban à henden Ansprüche, worin die Kennzeichnungen 50 chaque bord. numerische Schriftzeichen, alphabetische Schrift- zeichen oder Streifencodes umfassen. 5. Un procédé de production d'un ruban de sécurité apte à être incorporé à l'intérieur d'un papier fidu- 4. Sicherheitsstreifen nach irgendeinem der vorherge- ciaire, ruban qui comprend une bande de matière henden Ansprüche, worin die Kennzeichnungen 55 plastique translucide (11, 28) portant des indica- auf ein Band längs des Streifens begrenzt sind, teurs (12) qui sont lisibles à l'oeil nu sans assis- welches Band an jedem Rand im Abstand von den tance, lesdits indicateurs (12) étant définis par des Rändern des Streifens vorgesehen ist. dépots métalliques (31) sur la bande (28), lesdits

5 91EP 0 536 855 B2 0 dépôts métalliques étant appliqués par un proces- sus qui implique une métallisation sélective par estampage direct à chaud sur la bande ou par utili- sation d'un masque ou d'un gabarit dans un dispo- sitif de métallisation sous vide, ou par métallisation 5 et démétallisation sélective par gravure chimique ou par d'autres procédés de métallisation, à l'exclu- sion d'une impression directe d'encres métalliques sur la surface de matière plastique. 10

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