IMPROVEMENTS IN OR RELATING TO SECURITY OF DOCUMENTS

Description

[0001] This invention relates to the manufacturing process for paper used in production of printed documents such as banknotes and further to banknotes provided with enhanced security features.

[0002] Any product which has an intrinsic value is open to abuse by counterfeiters who look to provide cheaper and often inferior products which seek to imitate the genuine product. Often telling the difference between a genuine product and a counterfeit one can only be done by a professional who is skilled at spotting small inconsistencies between the two products.

[0003] Counterfeiting is a particular problem in relation to printed documents such as passports and particularly currency and the development of ever more complex printing equipment means that as more complex security measures are applied to these products, counterfeiters are able to keep pace with the security developments and adapt their processes very quickly to copy any new features.

[0004] The circulation of counterfeit money in particular has a detrimental effect on society including the reduction in value of genuine money, a contribution to inflation due to more money, and indeed an unauthorised artificial increase in the money supply within the economy and losses due to companies not being reimbursed for counterfeit money which is detected and subsequently confiscated.

[0005] Traditionally, anti-counterfeiting measures have been introduced in the printing of banknotes beginning with the use of numbers on individual banknotes in order to make give the banknote a unique identifier and to make it more difficult to produce counterfeit notes.

[0006] However, as the number of banknotes in circulation grew, the use of serial numbers alone was no longer sufficient to provide a secure means of identifying counterfeit notes, particularly at a point of sale where it would not be possible to look up a list of bank note numbers to verify whether an individual note was genuine.

[0007] Over time, the security features have developed with ever more intricate processes as the skill of counterfeiters has grown. Some of the security features currently used in modern banknote printing include reflecting strips which comprise polymer strips with transparent and foil plated areas, security threads which can be incorporated into the banknote with sections provided above the upper surface and sections embedded in the banknote, colour changing features which appear different when viewed from different angles, holograms, the use of paint which glows under UV light and watermarks.

[0008] Watermarks are one of the main security features particularly used in the manufacture of banknotes. The process of forming a watermark is very complicated and many of the steps occur during the manufacturing process of the banknote paper itself while the paper stock comprises raw and wet cellulose. In general, darker areas in a watermark are formed by thicker layers within the cellulose.

[0009] Watermarks can be formed by impressing a metal stamp known as a dandy roll or cylinder mould onto the paper during manufacture. The dandy roll is a light cylinder or roller covered by a material similar to a screen that is embossed with a pattern or electrotype.

[0010] In known processes, such as, for example, described in US 1,571, 715 (Fearing), the dandy roll is impressed into the paper pulp and the pattern embossed on the outer surface of the dandy roll is transferred to the fibres of the paper pulp, compressing and reducing their thickness in that area. As the patterned portion of the page is thinner, it transmits more light through and therefore has a lighter appearance than the surrounding paper. Thus, when the resulting paper is held up before a light source, the watermark produced in the paper can be easily seen. US 2009/0301676 A1 (Rosset) discloses a multi layer paper having a watermark formed in each layer.

[0011] In a further known process, the dandy roll may be replaced by a cylinder roller which rotates within a vat of paper stock in the form of a slurry. The cylinder roller has areas of relief formed in the outer surface of the roller rather than having metal wires placed upon the surface. As the cylinder rotates, the slurry is picked up on the surface of the cylinder where it settles in the recessed areas of the surface from which it is dispensed as a wet slurry sheet. The sheet is pressed between the cylinder roller and the second roller as it is dispensed and a shaded watermark is created on the surface of the sheet of paper pulp as it passes through the rollers. Once dry, the paper sheet may be rolled again to produce a watermark of even thickness but with varying density and these watermarks are generally more clear and detailed than those formed by a dandy roll process.

[0012] When producing banknotes, cylinder rollers are typically used as very intricate patterns can be formed on the surface of the roller for example these can be etched or embossed into the surface of formed by building up a profile using electrotype on the surface of the roller. It is important to form as clear and well defined a watermark as possible in order to make the counterfeiting of the banknote as difficult as possible and this has become an important anti-counterfeiting measure.

[0013] In known production processes, after the watermark is applied as described above, the paper pulp sheet passes around one or more plain rollers as it is drawn off the watermark roller.

[0014] It is an object of the present invention to provide an improved manufacturing process for paper products which would result in improved security of documents, in particular banknotes or passports.

[0015] According to a first aspect of the present invention there is provided a method of manufacturing paper comprising the steps of forming a watermark in a primary surface of a layer of a paper substrate and forming a watermark in a secondary surface of said layer of the paper substrate.

[0016] Optionally the watermarks are formed in the primary and secondary surfaces of the layer of the paper substrate simultaneously.

[0017] Thus the primary and secondary surfaces are provided on opposite sides of a single layer of the paper substrate.

[0018] Preferably the layer of the paper substrate comprises a fibre mat.

[0019] Preferably also the fibre mat is formed from paper stock.

[0020] Advantageously the fibre mat is formed by a roller rotating within a vat of paper stock.

[0021] Preferably the layer of the paper substrate is formed by an expanding cylinder mould.

[0022] Conveniently a watermark is formed in the secondary surface of the layer of the paper substrate by passing the layer over the surface of a profiled roller.

[0023] Advantageously the watermark is formed in the secondary surface of the layer of the paper substrate by passing the layer over a short forming cylinder.

[0024] Alternatively the watermark is formed on the opposite side of the single layer of the paper substrate by passing the layer over a wading roll.

[0025] Conveniently the watermark formed in either the primary or secondary surfaces of the layer of the paper substrate may be changed by changing the outer profile of the roller over which the paper substrate passes.

[0026] The layer of the paper substrate may comprise a light weight paper layer.

[0027] The present invention provides a method of manufacturing paper and a banknote made in accordance with the method, as defined in the appended claims.

[0028] Embodiments of the present invention will now be described with reference to the accompanying figures in which:

Figure 1 is a schematic view of part of an apparatus 1 for manufacturing paper, and

Figure 2 is a part cross sectional view of the apparatus of Figure 1.

[0029] In particular, the apparatus relates to the stage in the manufacturing process in which watermarks are applied to the paper.

[0030] The apparatus comprises a vat 2 of paper stock or slurry within which a roller 3 is rotatably mounted. In the embodiment shown, roller 3 is an expanding cylinder mould. The expanding cylinder mould 3 is mounted on an axle 4 which extends through the cylinder and projects out of either end of the cylinder mould 3. A journal 5 is formed in the side of the vat 2 of paper stock within which the ends of the axle are received to allow the cylinder mould 3 to rotate within the vat 2. In the embodiment shown, the cylinder mould 3 is not totally immersed in the vat 2 of paper stock but the lower portion of the cylinder mould 3 sits within the paper stock slurry while the upper portion of the cylinders mould 3 is held above the level of the slurry.

[0031] The expanding cylinder mould 3 has a pattern provided on its outer surface. This may be formed by known techniques such as embossing, etching or by building up a pattern using electrotype on the surface of the roller in accordance with techniques known to the person skilled in the art.

[0032] A further roller 6 is mounted in the vat 2 adjacent the expanding cylinder mould 3. Such a roller 6 is typically known as a wading roll and functions to improve the formation and clarity of a watermark formed into a paper sheet or web by the expanding cylinder mould 3 or the formation and clarity of the paper sheet or web itself.

[0033] The outer surface of the wading roll 6 is adapted for imparting a watermark on the secondary side of the paper as it is drawn off the expanding cylinder mould 3. In the present embodiment, the wading roll 6 is formed with a cover 10 having the required profile or relief patter embossed therein to form a watermark as will be described below.

[0034] The wading roll 6 is mounted within a bracket 11 which acts to hold the wading roll 6 at the correction position adjacent the cylinder mould 3 and allows the position of the wading roll 6 to be adjusted if necessary.

[0035] A conveyor belt 7 is fixed in close proximity to the expanding cylinder mould 3. The conveyor belt 7 may comprise a felt loop which extends around a series of rollers 8, 9 to provide a relatively soft surface upon which a web of paper material can be deposited during manufacture.

[0036] In the embodiment illustrated, one end of the conveyor belt 7 is supported by a roller 8 which in this embodiment comprises a couch roll above and in close proximity to the expanding cylinder mould 3 and the other end of the conveyor belt 7 is supported at a remote point by two rollers 9. The position of the rollers 8,9 and the dimensions of the conveyor belt 7 may be determined by the location of the apparatus, for example within a machine housing warehouse or may be altered and adjusted by the user depending upon the requirements for the paper product being manufactured.

[0037] Control means (not shown) are provided for controlling the speed of operation of the conveyor belt.

[0038] Referring to the figure, the process for applying watermarks to a paper substrate during manufacture will now be described.

[0039] An expanding cylinder mould 3 having the required relief pattern provided on its outer surface is prepared in accordance with known techniques and is mounted within the vat 2 which contains a slurry of paper stock. The ends of the axle 4 of the cylinder mould 3 are received in the bearings 5 in the sides of the vat 2 such that the cylinder mould 3 can freely rotate within the vat 2. The level of the slurry of paper stock is monitored and adjusted to ensure that the outer surface of the cylinder mould 3 can be coated within the paper stock as the cylinder mould 3 rotates.

[0040] The cover 10 which is applied over the wading roll 6 has the required relief pattern provided on its outer surface is also prepared in accordance with known techniques and this is mounted over the wading roll 6 which is mounted in close proximity to the expanding cylinder mould 3.

[0041] The expanding cylinder mould 3 is rotated and the conveyor belt 7 is operated such that the conveyor belt 7 rotates around the rollers 8 and 9.

[0042] A layer or web of paper 12 is formed by the rotating expanding cylinder mould 3. As the cylinder mould 3 rotates in the direction of arrow A, a coating of paper stock flows over the surface of the cylinder mould 3 and is picked up from the vat 2 and settles in the recessed areas of the surface of the cylinder mould 3. The cylinder mould 3 is adapted to encourage water in the slurry to flow through the cover of the cylinder mould 3 from where it is discharged.

[0043] Furthermore, the wading roll 6, which may be driven or undriven, removes excess slurry from the surface of the cylinder mould 3 to improve the clarity and formation of the watermark in the side of the paper in contact with the cylinder mould 3 and at the same time contacts the other, opposite side of the layer of paper 12 and imparts a second watermark to the layer 12 such that during the forming process watermarks are formed on each side of the layer of paper 12.

[0044] The fibre mat that accumulates on the cylinder surface is then deposited from the recessed areas onto the conveyor belt 7 as a primary layer or web 12 of paper. The primary layer has a first watermark formed in one side from the pattern on the surface of the cylinder mould 3 and simultaneously a second watermark formed in the other, opposite side of the paper from the pattern on the surface of the wading roll 6.

[0045] The sheet of watermarked paper is drawn off the conveyor belt 7 at a selected point which in the embodiment described is before the conveyor belt 7 passes around the rollers 9 as it returns towards the watermarking cylinders 3, 6, from where it can be directed to further processing stations such as drying or pressing.

[0046] The manufacturing process described allows for the forming of watermarks in both sides of a single layer of paper during the same manufacturing process which provides an improved security measure for the manufacture of paper documents, and more particularly for the manufacture of paper for the use in printing banknotes or security documents such as passports.

[0047] By adjusting the starting relative rotational positions of the wading roll 6 and the expanding cylinder mould 3, the positions of the watermarks on the opposite sides of the layer of paper 12 which is manufactured can be controlled such that, as a further security measure, they may be made to overlap or line up in such a manner that a more complex image, or a complementary image is formed in a single pass through the processing apparatus. This provides a further security feature which makes counterfeiting of the banknotes more difficult but also renders the identification of counterfeit banknotes simpler thus giving greater security to the banknote in question.

[0048] The present invention allows watermarks to be imparted to both sides of a single layer or web of paper and uses existing equipment in the production of improved security documents without undue cost.

[0049] It is further intended that a range of interchangeable wading rolls or covers may be supplied, each with a different pattern formed on or into the surface of wading roll or the cover of the cylinder or roll such that a variety of different watermarks may be imparted to the second side of the paper sheet depending upon which of the wading rolls is mounted into the paper forming apparatus.

[0050] It is a further advantage of the present invention that the wading roll is typically of a smaller diameter than the expanding cylinder mould and therefore changing out the wading roll to change the pattern of the watermark applied to the second surface of the paper sheet can be done at much less cost that changing the pattern of the expanding cylinder mould thereby allowing paper manufacturing firms to maintain a larger stock of watermarking cylinders than is currently possible which in turn allows for greater flexibility in providing combinations of watermarks to the first and second sides of the paper sheet as produced.

[0051] Furthermore, the watermarks applied through this process may be designed to provide improved durability to the paper product being produced. This is especially relevant in the manufacture of paper intended for the printing of currency and banknotes which are subjected to heavy handling through their lifetime where the banknotes are passed from person to person during commercial transactions or red into automated payment machines which can lead to damage to the edges of the banknote over time. However, application of the watermarks as described around the edges on both sides of the banknote during the production process may lead to improvements in the stability and durability of the banknote.

Claims

1. A method of manufacturing paper comprising the steps of
forming a watermark in a primary surface of a single layer (12) paper substrate characterised by the step of
forming a watermark in a secondary surface of said layer.

2. A method according to claim 1, wherein the watermarks are formed in the primary and secondary surfaces of the layer (12) of the paper substrate simultaneously.

3. A method according to any of claims 1 or 2, wherein the secondary surface is provided on the opposite side of the single layer (12) of the paper from the primary surface.

4. A method according to any of claims 1-3 wherein the layer (12) of the paper substrate comprises a fibre mat.

5. A method according to claim 4, wherein the fibre mat is formed from paper stock.

6. A method according to claim 5 wherein the fibre mat is formed by a roller (3) rotating within a vat (2) of paper stock.

7. A method according to any of the preceding claims wherein the layer (12) of the paper substrate is formed by an expanding cylinder mould.

8. A method according to any of the preceding claims, wherein a watermark is formed in the secondary surface of the layer (12) of the paper substrate by passing the layer (12) over the surface of a profiled roller (6).

9. A method according to claim 8 wherein the watermark is formed in the secondary surface of the layer (12) of the paper substrate by passing the layer (12) over a short forming cylinder.

10. A method according to claim 8, wherein the watermark is formed in the secondary surface of the layer (12) of the paper substrate by passing the layer (12) over a wading roll.

11. A method according to any of the preceding claims, wherein the watermark formed in the secondary surface of the layer of the paper substrate is changed by changing the outer profile of the profiled roller (6) over which the layer (12) of paper substrate passes.

12. A banknote comprising
a watermark in a primary surface of a single layer paper substrate characterised in that
the banknote comprises a watermark in a secondary surface of said layer.

Ansprüche

1. Ein Verfahren zum Herstellen von Papier, beinhaltend die Schritte des Bildens eines Wasserzeichens in einer primären Oberfläche eines Papiersubstrats mit einer einzigen Schicht (12), gekennzeichnet durch den folgenden Schritt:

Bilden eines Wasserzeichens in einer sekundären Oberfläche der Schicht.

2. Verfahren gemäß Anspruch 1, wobei die Wasserzeichen gleichzeitig in der primären und sekundären Oberfläche der Schicht (12) des Papiersubstrats gebildet werden.

3. Verfahren gemäß einem der Ansprüche 1 oder 2, wobei die sekundäre Oberfläche auf der der primären Oberfläche gegenüberliegenden Seite der einzigen Schicht (12) des Papiers bereitgestellt ist.

4. Verfahren gemäß einem der Ansprüche 1-3, wobei die Schicht (12) des Papiersubstrats eine Fasermatte beinhaltet.

5. Verfahren gemäß Anspruch 4, wobei die Fasermatte aus Rohpapier gebildet ist.

6. Verfahren gemäß Anspruch 5, wobei die Fasermatte mittels einer Walze (3), die sich innerhalb einer Wanne (2) mit Rohpapier dreht, gebildet wird.

7. Verfahren gemäß einem der vorhergehenden Ansprüche, wobei die Schicht (12) des Papiersubstrats mittels eines expandierenden Rundsiebzylinders gebildet wird.

8. Verfahren gemäß einem der vorhergehenden Ansprüche, wobei ein Wasserzeichen in der sekundären Oberfläche der Schicht (12) des Papiersubstrats gebildet wird, indem die Schicht (12) über die Oberfläche einer Profilwalze (6) geführt wird.

9. Verfahren gemäß Anspruch 8, wobei das Wasserzeichen in der sekundären Oberfläche der Schicht (12) des Papiersubstrats gebildet wird, indem die Schicht (12) über einen kurzen Formzylinder geführt wird.

10. Verfahren gemäß Anspruch 8, wobei das Wasserzeichen in der sekundären Oberfläche der Schicht (12) des Papiersubstrats gebildet wird, indem die Schicht (12) über eine "Wading Roll" geführt wird.

11. Verfahren gemäß einem der vorhergehenden Ansprüche, wobei das in der sekundären Oberfläche der Schicht des Papiersubstrats gebildete Wasserzeichen durch das Ändern des Außenprofils der Profilwalze (6), über welche die Schicht (12) des Papiersubstrats geführt wird, geändert wird.

12. Eine Banknote, beinhaltend:

ein Wasserzeichen in einer primären Oberfläche eines Papiersubstrats mit einer einzigen Schicht, dadurch gekennzeichnet, dass

die Banknote in einer sekundären Oberfläche der Schicht ein Wasserzeichen beinhaltet.

Revendications

1. Une méthode de fabrication de papier comprenant les étapes consistant à former un filigrane dans une surface primaire d'un substrat en papier à couche unique (12) caractérisée par l'étape consistant à
former un filigrane dans une surface secondaire de ladite couche.

2. Une méthode selon la revendication 1, dans laquelle les filigranes sont formés dans les surfaces primaire et secondaire de la couche (12) du substrat en papier de manière simultanée.

3. Une méthode selon n'importe lesquelles des revendications 1 ou 2, dans laquelle la surface secondaire est prévue sur le côté opposé de la couche unique (12) du papier à partir de la surface primaire.

4. Une méthode selon n'importe lesquelles des revendications 1 à 3, dans laquelle la couche (12) du substrat en papier comprend un matelas de fibres.

5. Une méthode selon la revendication 4, dans laquelle le matelas de fibres est formé à partir de papier avant transformation.

6. Une méthode selon la revendication 5, dans laquelle le matelas de fibres est formé à l'aide d'un rouleau (3) tournant au sein d'une cuve (2) de papier avant transformation.

7. Une méthode selon n'importe lesquelles des revendications précédentes, dans laquelle la couche (12) du substrat en papier est formée à l'aide d'une forme ronde expansible.

8. Une méthode selon n'importe lesquelles des revendications précédentes, dans laquelle un filigrane est formé dans la surface secondaire de la couche (12) du substrat en papier en faisant passer la couche (12) par-dessus la surface d'un rouleau profilé (6).

9. Une méthode selon la revendication 8, dans laquelle le filigrane est formé dans la surface secondaire de la couche (12) du substrat en papier en faisant passer la couche (12) par-dessus un cylindre formeur court.

10. Une méthode selon la revendication 8, dans laquelle le filigrane est formé dans la surface secondaire de la couche (12) du substrat en papier en faisant passer la couche (12) par-dessus un rouleau « wading roll ».

11. Une méthode selon n'importe lesquelles des revendications précédentes, dans laquelle le filigrane formé dans la surface secondaire de la couche du substrat en papier est changé en changeant le profil externe du rouleau profilé (6) par-dessus lequel la couche (12) de substrat en papier passe.

12. Un billet de banque comprenant
un filigrane dans une surface primaire d'un substrat en papier à couche unique caractérisé en ce
le billet de banque comprend un filigrane dans une surface secondaire de ladite couche.

Drawing