Patentamt Europaisches || || 1 1| || || || 1 1| || || || || || (19) J European Patent Office

Office europeen des brevets (1 1 ) EP 0 536 855 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publicationation and mention (51) Int. CI.6: B42D 15/00, B41M3/14 of the grant of the patent: 11.12.1 996 Bulletin 1 996/50

(21) Application number: 92203692.6

(22) Date of filing: 24.02.1987

(54) Security strip for a security paper for currency & banknotes Sicherheitsstreifen fur ein Sicherheitspapier fur Wertpapiere und Banknoten Ruban de securite pour papier de securite pour papiers fiduciaires et billets de banque

(84) Designated Contracting States: (74) Representative: Williams, John Francis et al CH DE FR GB IT LI NL SE WILLIAMS, POWELL & ASSOCIATES 34 Tavistock Street (43) Date of publication of application: London WC2E 7PB (GB) 14.04.1993 Bulletin 1993/15 (56) References cited: (62) Application number of the earlier application in EP-A- 0 070 172 EP-A- 01 05 969 accordance with Art. 76 EPC: 87102596.1 EP-A- 0 181 770 DE-A- 1 446 851 GB-A- 237 828 GB-A- 1 486 079 (73) Proprietor: CRANE &CO.INC. GB-A-2103 669 US-A-4 552 617 Dalton Massachusetts 01226 (US) US-A-4 652 015

(72) Inventor: Crane, Timothy T. • DATABASE WPIL Week 8446, Derwent Windsor, Massachusetts 01226 (US) Publications Ltd., London, GB; AN 84282244 & AU-A-1 793 283 (AQUINO) • GB-A-J19963 (JULES GERNAERT)

CO LO LO CO CO CO Note: Within nine months from the publication of the mention of the grant of the European patent, give LO any person may notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in o a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. Q_ 99(1) European Patent Convention). LU Printed by Rank Xerox (UK) Business Services 2.13.9/3.4 1 EP 0 536 855 B1 2

Description to be visually accessed from one side of the security paper. BACKGROUND OF THE INVENTION All the aforementioned methods for incorporating security devices within the security paper allow for visi- Methods are currently available for deploying a thin s ble access to the presence of the security device by strip of clear material such as polyester film within paper means of the unaided eye. The Williams approach could during the papermaking process. If the film is used as a lead an observer to believe that a blurred line on the sur- security thread and is first micro-printed prior to dispen- face of the security paper, for example, is a sufficient sation during the papermaking process, the resulting indication of authenticity without requiring that the paper paper then contains a legible code that is legible in w be held up to transmitted light for actual verification. The transmitted light. With papers of the substance and earlier security device also caused the security paper to thickness used for currency and banknotes, the code is exhibit an increased thickness in the vicinity of the also visible under reflected light. The purpose of printed device compared to the thickness of the paper itself. security threads is to deter a potential forger since the This increased thickness or "bulge" line can be dupli- coded indicia on the thread is buried within the paper is cated by a skilled forger to lead the observer to believe and cannot be duplicated by surface printing tech- that a security device is actually present, without further niques. The authenticity of such a document can be examination. readily verified by comparing the appearance of the When an unprinted metallized plastic thread such security thread under reflected light against its appear- as described within the aforementioned patent to Wil- ance in transmitted light. It is the reflected light appear- 20 liams is used as a security thread, the optical and elec- ance that is most relied upon by the public when trical properties of the thread can be used for automatic handling currency and banknotes in general circulation. verification by determining optical variations across the The reflected light appearance, however, does not paper as well as by standard electronic metal detection directly reveal the presence of the printing that is com- techniques. It has been determined, however, that the pletely legible in transmitted light. In fact, the nondistinct 25 optical properties of such a metallized thread can be muted line of the security thread that is conspicuous at duplicated to some extent by means of a pale but the surface of the currency and banknotes becomes the opaque line printed on the surface of the paper in the distinctive feature in the eyes of the general public. vicinity of where the security thread would be located. A The inclusion of the security device within the body dull pencil line may also fool the unskilled observer as to of the security paper now requires sophisticated paper- 30 the presence of a buried security thread. making machinery which is not available to forgers. One For reliable verification, the currency or banknote method of incorporating the security device is described must be held up to a light source to reveal the coded within U.S. patent 3,880,706 to Williams, wherein the indicia on the security thread that make a security security device is sandwiched between two layers of thread virtually impossible to forge. The nondistinctive formed paper midway during the papermaking process. 35 line that is the visible surface manifestation of the An opaque item embedded within security paper is embedded security thread under reflected light is easily also described as early as the issue dates of U.S. pat- simulated also by a variety of printing processes. ents 210,089; 964,014; and 1,929,828. It is believed Earlier attempts at printing on plastic strips and that the two ply insertion approach disclosed within embedding the strips within the paper have not hereto- these patents deterred feasibility for use within currency 40 fore proved feasible since the ink used to form the paper, since the two ply papers could conceivably be printed information that was legible under transmitted replicated by laminating thin sheets of counterfeit paper light also allowed the information to become legible without requiring a sophisticated papermaking under reflected light. The public could then rely upon the machine. The simplicity in the configuration and design presence of the printed matter solely under reflected of the proposed security items were such that a forger 45 light, which printing is easily replicated by counterfeit could replicate them without a great deal of skill or means. expense. One way to ensure that the public does not come to Another method of incorporating the security device rely on such an easily simulated security thread charac- within the security paper comprises pressing the device teristic is to manufacture currency and banknote paper within the wet paper fibers while the fibers are unconsol- so containing a security thread that is virtually invisible idated and pliable as taught by U.S. patent 4,534,398 to under reflected light with no manifestation on the sur- Timothy Crane, which patent is incorporated herein for face of the currency or banknote that such a security purposes of reference. In this method the security thread is present. This two-fold test of authentication, device is visible from one surface of the security paper namely, legible under transmitted light and invisible for visual verification. 55 under reflected light, has heretofore not been met by U.S. patent 4,552,617 also in the name of Timothy any of the earlier noted devices. Crane describes a method of incorporating a security US-A-4,552,61 7 discloses a system for embedding device within security paper by dissolving the security into paper security indicia, which includes providing a device carrier substrate and allowing the security device soluble carrier substrate in strip form with micro-coded

2 3 EP 0 536 855 B1 4 information. The strip is inserted into the fibres used for type papermaking machine adapted for inserting forming paper during the paper-making process, such the security device from a continuous strip within that the strip dissolves to leave the micro-coded infor- the paper fibers; mation intact as security indicia within the paper. The Figure 4 is an enlarged top perspective view of a micro-printed indicia may be formed from ink, fluores- 5 part of an aluminized polyester security device strip cent pigments, dyes or metallised and metal oxide depicted in Figures 2 and 3 after a clear protective coated films. overcoat has been applied to the aluminized print; EP-A-0,181,770 discloses an optical interference Figure 5 is a top perspective view of an aluminized authenticating device which includes a polyester film polyester security device film with a clear protective substrate and at least two coatings thereon, one being 10 overcoat applied to the area where indicia is to be radiation absorbing so as to be selectively removed by retained and after an etchant solution has been an infrared laser beam after being deposited on the sub- applied producing a soluble aluminum salt in the strate by a method of vapour deposition. unprotected area; GB-A-2, 103,669 discloses a security device in the Figure 6 is a top perspective view of the security form of a diffractor grating structure applied to a dissolv- 15 device film of Figure 5 after the etchant solution has able carrier web. been applied and the soluble aluminum salt has The purpose of this invention therefore, is to pro- been removed; and vide a method for incorporating a security thread bear- Figure 7 is a side sectional view of the security ing printed information within security paper that is device of Figure 6 embedded within paper formed easily readable in transmitted light but virtually undetec- 20 within the papermaking machines depicted in Fig- table when it is viewed under reflected light. A further ures 2 and 3 according to the invention. purpose of this invention is to provide the printed infor- mation at a specific location within the security paper DESCRIPTION OF THE PREFERRED EMBODIMENT and to economically produce the paper at high speeds using modern manufacturing techniques. 25 The security paper of the invention finds application According to an aspect of the present invention, in the form of a banknote or currency such as the United there is provided a security strip as specified in claim 1 . States Federal Reserve note 1 0 depicted in Figure 1 as According to another aspect of the present inven- consisting of a rectangular sheet of paper 7 with a por- tion, there is provided a method of producing a security trait 6 of a former United States President along with a strip as specified in claim 5. 30 numerical designation 5 of the value of the note. A plas- The invention thus comprises the encoding of tic strip 1 1 is embedded within the paper in a manner to printed information onto a strip of clear plastic film which be described below in some detail. The strip extending is later incorporated within the paper during the paper- in the direction defined by the parallel dotted lines is not making process. The printed information can be visually readily visible on the surface of the paper under read or machine detected. The methods of detection 35 reflected illumination to the unaided eye. The strip itself include differences in transmission optical density, dif- has a planar configuration that is not discernible by ferences in capacitance, and variations in the electrical touch, unlike the security threads used within some current within a tuned resonance circuit. European currency, that slightly distorts the surface of The encoded information is confined within a nar- the paper and can actually be felt by gently rubbing the row band on the plastic film which can be accurately 40 paper between one's fingers. Although the security located within currency, banknote or security paper threads are difficult to spot in new currency under without interfering with the speed of modern paper man- reflected light, the presence of the earlier security ufacturing equipment. In one embodiment, the printed thread becomes manifested by the blurred outlines of information is a legible phrase, the letters of which are the thread apparently caused by repeated handling of comprised of vacuum metallized aluminum having a 45 the currency. A careless teller or cashier, for example, thickness of 3-4 urn (300-400 angstroms). could be fooled by a carefully drawn soft pencil line in the same location one would expect to detect the secu- BRIEF DESCRIPTION OF THE DRAWINGS rity thread. The planar configuration of the plastic strip 1 1 ensures that its presence remains undetected under Figure 1 is a plan view of a banknote incorporating so reflected light even after long periods of continued use. a security device according to the invention; When the bill is held up to a source of transmitted light Figure 1a is an enlarged plan view of the banknote or passed over a "light table" consisting of a transparent of Figure 1 depicting a legible phrase of the security or translucent surface over a strong source of light, the device viewed in transmitted light; security indicia 12 shown in Figure 1a becomes readily Figure 2 is a side view in partial section of a four- 55 visible. drenier papermaking machine with a funnel tube for The concept of embedding a security device within introducing the security device from a continuous the paper fibers of a fourdrenier papermaking machine strip within the paper fibers; is described within the aforementioned U.S. patent to Figure 3 is a side view in partial section of a cylinder Timothy Crane and one such fourdrenier machine is

3 5 EP 0 536 855 B1 6 depicted at 16 in Figure 2. Figure 6 with all the aluminium removed from the sur- The headbox 3 contains a slurry 15 consisting of a face of the polyester film 28 and exhibiting a planar pol- mixture of cellulosic fibers and fillers, all in a water vehi- yester surface 28A. The letters 31 remain intact on the cle illustrated by the dashed lines 8. The security strip surface after the dissolved metal is removed. Other 1 3 is fed continuously from a reel (not shown) through a s methods of applying the letters to the surface can also tube 14 into the slurry at the discharge outlet 2 of the be employed without departing from the scope of this headbox onto the fourdrenier wire 17. The fibers contin- invention as defined in the appended claims. Legible uously surround the security strip as the slurry proceeds printing or bar type optically readable codes can be along the wire becoming dewatered and consolidated directly hot stamped onto the polyester or applied via during the papermaking process. Once the paper has 10 selective metallization using a mask or template in the reached a final stage of dewatering, it is then passed vacuum metallizer. The security paper 25 shown in Fig- through heated rollers for pressing and drying into a ure 3 containing the security strip 13 embedded after final paper product. The position of the tube 1 4 relative heating and pressing is depicted at 25' in Figure 7. The to the lateral extent of the wire 1 7 accurately determines paper fibers 27 completely surround the security strip the predetermined location of the security strip within is and prevent visual access to the security strip from the finished paper product. either surface of the security paper. It is noted that the The concept of embedding a security device within thickness of the paper is uniform and there is no bulge the paper fibers of a cylinder mold papermaking in the vicinity of the paper containing the security strip. machine is also described within the aforementioned This is an important feature of the invention for the rea- patent to Timothy Crane and one such cylinder mold 20 sons discussed earlier. Although the metal letters 31 on machine is shown at 18 in Figure 3. The slurry 15 con- the plastic strip 1 1 are embedded within the paper fib- tains the same composition of paper fibers 26 in water ers, these letters are readily visible when light is trans- 27 as that described earlier with reference to the slurry mitted through the security paper from one surface and on Figure 2. The security strip is fed from a reel (not the security paper is viewed from the opposite surface shown) over a guide roll 1 9 onto the screen 22 of the 25 when the thickness of the metal is between 3-4 urn cylinder 20 after some of the paper fibers have been (300-400 angstroms) and the thickness of the paper is gathered on the screen as indicated generally at 26'. from 0.1-0.15 mm (4-6 thousandths of an inch). The consolidated paper fibers containing the security It has thus been shown that a planar plastic film strip is shown at 25 and is picked up from the cylinder by bearing either machine readable code or visually acces- a felt 23 traveling in the indicated direction over a guide 30 sible letters can be embedded at a predetermined loca- roll 24 onto a couch roll 21 and back in the opposite tion within the currency and banknote paper for direction to the heating and pressing stages of the authentication in transmitted light. The code is invisible papermaking process to form the finished security to the unaided eye under reflected light when viewed paper. from either surface. A length 30 of the security strip 1 3 is shown in Fig- 35 ure 4 to consist of a polyester film 28 overcoated with a Claims vacuum deposited aluminum layer 29 which defines a planar aluminum coated surface 29A. The letters 31 1. A security strip suitable for incorporation within a spelling "CRANE", are printed onto the aluminum sur- security paper, comprising a clear plastic strip face by means of a caustic resistant ink varnish. When 40 (11,28) having indicia (12), said indicia (12) being an acid soluble metal such as tin is deposited on the defined by metal deposits (31) on the strip (28) pro- polyester film, an acid resistive ink varnish is used to duced by a process involving selective metallization print the letters. The same length of security strip is by directly hot stamping onto the strip or using a shown at 30A in Figure 5 with the unprotected area of mask or template in a vacuum metalliser, or by met- the aluminum coated surface 29A covered with a plural- 45 allization and selective demetallisation by chemical ity of crosses 32 to indicate the aluminum metal that etching, or by other metallisation methods exclud- must be removed by contact with a caustic solution of ing directly printing metal inks onto the plastic sur- NaOH in water. The caustic resistant ink varnish pro- face. tects the metal surface under the varnish from contact with the caustic. Although the varnish is effective in pre- so 2. A security strip as claimed in claim 1 , wherein said venting the metal from becoming dissolved by the caus- metal deposit has a thickness of 3-4 urn (300 to 400 tic NaOH solution, it is noted that fine printing is best angstroms). protected from becoming dissolved by the NaOH solu- tion when the contact with the NaOH solution is as brief 3. A security strip as claimed in any preceding claim, as possible. The Sodium aluminate salt formed by 55 wherein said indicia are numeric characters, alpha- reacting the unprotected aluminium with the NaOH betic characters or bar codes. solution is gently washed away from the surface by application of a clear water rinse. 4. A security strip as claimed in any preceding claim The same length of security strip is shown at 30B in wherein said indicia are confined within a band

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along the strip which band is spaced at each edge Metallisierung und selektive Demetallisierung from the edges of the strip. durch chemisches Atzen, oder durch andere Metal- lisierungsmethoden ausschlieBlich des direkten 5. A method of producing a security strip suitable for Druckens von Metalltinten auf die Kunststoffoberf la- incorporation within a security paper, which strip 5 che umfaBt. comprises a clear plastic strip (1 1 ,28) having indicia (12), said indicia (12) being defined by metal Revendications deposits (31) on the strip (28), wherein said metal deposits are applied by a process involving selec- 1 . Un ruban de securite apte a etre incorpore a I'inte- tive metallisation by directly hot stamping onto the w rieur d'un papier de securite, comprenant une strip or using a mask or template in a vacuum met- bande de matiere plastique translucide (11, 28) alliser, or by metallisation and selective demetalli- portant des indicateurs (12), lesdits indicateurs (12) sation by chemical etching, or by other metallisation etant definis par des depots metalliques (31) sur la methods excluding directly printing metal inks onto bande (28) produits par un processus qui implique the plastic surface. is une metallisation selective par estampage direct a chaud sur la bande ou par utilisation d'un masque Patentanspruche ou d'un gabarit dans un dispositif de metallisation sous vide, ou par metallisation et demetallisation 1. Sicherheitsstreifen zur Einarbeitung in ein Sicher- selective par gravure chimique ou par d'autres pro- heitspapier, umfassend einen klaren Kunststoff- 20 cedes de metallisation, a I'exclusion d'une impres- streifen (1 1 , 28) mit Kennzeichnungen (12), welche sion directe d'encres metalliques sur la surface de Kennzeichnungen (12) durch Metallabscheidungen matiere plastique. (31) auf dem Streifen (28) definiert sind, die durch ein Verfahren erzeugt worden sind, welches eine 2. Un ruban de securite selon la revendication 1 , dans selektive Metallisierung umfaBt durch direktes 25 lequel I'epaisseur dudit depot metallique est de 3 a HeiBpragen auf den Streifen oder die Verwendung 4 urn (300 a 400 angstroems). einer Maske oder Schablone in einer Vakuum- Metallisiervorrichtung, oder durch Metallisierung 3. Un ruban de securite selon une revendication pre- und selektive Demetallisierung durch chemisches cedents quelconque dans lequel lesdits indicateurs Atzen, oder durch andere Metallisierungsmethoden 30 sont des caracteres numeriques, des caracteres ausschlieBlich des direkten Druckens von Metalltin- alphabetiques ou des codes a barres. ten auf die Kunststoffoberf lache. 4. Un ruban de securite selon une revendication pre- 2. Sicherheitsstreifen nach Anspruch 1, worin die cedents quelconque dans lequel lesdits indicateurs Metallabscheidung eine Dicke von 3 - 4 urn (300 bis 35 sont confines a I'interieur d'une bande le long dudit 400 Angstrom) aufweist. ruban, bande qui est espacee des bords du ruban a chaque bord. 3. Sicherheitsstreifen nach irgendeinem der vorherge- henden Anspriiche, worin die Kennzeichnungen 5. Un procede de production d'un ruban de securite numerische Schriftzeichen. alphabetische Schrift- 40 apte a etre incorpore a I'interieur d'un papier de zeichen oder Streifencodes umfassen. securite, ruban qui comprend une bande de matiere plastique translucide (1 1 , 28) portant des 4. Sicherheitsstreifen nach irgendeinem der vorherge- indicateurs (12), lesdits indicateurs (12) etant defi- henden Anspriiche, worin die Kennzeichnungen nis par des depots metalliques (31) sur la bande auf ein Band langs des Streifens begrenzt sind, 45 (28), lesdits depots metalliques etant appliques par welches Band an jedem Rand im Abstand von den un processus qui implique une metallisation selec- Randern des Streifens vorgesehen ist. tive par estampage direct a chaud sur la bande ou par utilisation d'un masque ou d'un gabarit dans un 5. Verfahren zur Herstellung eines Sicherheitsstrei- dispositif de metallisation sous vide, ou par metalli- fens zur Einarbeitung in ein Sicherheitspapier, wel- 50 sation et demetallisation selective par gravure chi- cher Streifen einen klaren Kunststoffstreifen (11, mique ou par d'autres precedes de metallisation, a 28) umfaBt mit Kennzeichnungen (12), welche I'exclusion d'une impression directe d'encres metal- Kennzeichnungen (12) durch Metallabscheidungen liques sur la surface de matiere plastique. (31) auf dem Streifen (28) definiert sind, welche Metallabscheidungen durch ein Verfahren aufge- 55 bracht werden. welches eine selektive Metallisie- rung durch direktes HeiBpragen auf den Streifen oder die Verwendung einer Maske oder Schablone in einer Vakuum-Metallisiervorrichtung, oder durch

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