Abstract:
A fibrous security substrate for use in producing documents includes at least one aperture extending therethrough and contains an elongate impermeable element at least partially embedded therein such that at least one edge thereof is exposed in the aperture.

Description:
This application is a 371 of PCT/GB03/02723, filed Jun. 25, 2003 which claims priority of United Kingdom Patent document 0214645.4, filed Jun. 25, 2002. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to improvements in methods of making fibrous substrates, and in particular to such substrates containing an elongate impermeable element which can be easily verified through an aperture in the substrate. 
     2. The Prior Art 
     It is generally known to include elongate security elements in security paper, as a security feature. Such elements can be threads, strips or ribbons of, for example, plastics film, metal foil, metallised plastic, metal wire. These security elements are included in the thickness of security paper to render imitation of documents produced from the paper more difficult. These elements help in the verification of security documents as they render the view of the documents in reflected light different from that in transmitted light. To increase the security provided by the inclusion of such an elongate element, it is also known to endow the element itself with one or more verifiable properties over and above its presence or absence. Such additional properties include magnetic properties, electrical conductivities, the ability to absorb x-rays and fluorescence. 
     As a further security feature, it has been found to be particularly advantageous to provide windows in one side of the surface of the paper, which expose such elongate elements at spaced locations. Examples of methods of manufacturing such paper incorporating security elements with or without windows are described below. It should be noted that references to “windowed thread paper” include windowed paper incorporating any elongate security element. 
     EP-A-0059056 describes a method of manufacture of windowed thread paper on a cylinder mould paper-making machine. The technique involves embossing the cylinder mould cover and bringing an impermeable elongate security element into contact with the raised regions of an embossed mould cover, prior to the contact entry point into a vat of aqueous stock. Where the impermeable security element makes intimate contact with the raised regions of the embossing, no fibre deposition can occur. After the paper is fully formed and couched from the cylinder mould cover, the water is extracted from the wet fibre mat and the paper is passed through a drying process. In the finished paper the contact points are present as exposed regions which ultimately form windows, visible in reflected light, on one side of a banknote paper. 
     WO-A-93/08327 describes a method of manufacturing windowed thread paper on a Fourdrinier paper-making machine. A rotating embedment means, with a modified profile for embossing, is used to drive an impermeable elongate security element into draining paper stock, on a Fourdrinier wire. The profile of the embedment means is such that raised portions are provided which remain in contact with the security element during the embedment process. Thus, paper fibres are prevented from collecting between the security element and embedment means, such that the security element is subsequently exposed in windowed regions of paper. 
     The aforementioned processes enable paper to be manufactured in which the security element is exposed in windows in one surface of the paper, or in windows in both surfaces at alternating positions, or to form apertures whereby the windows on the front of the document are in register with those on the back. In order for a user to confirm the security element is continuous and running within the paper they must view the paper in transmitted light. However, users frequently tear the paper in the region of the security element to determine its presence, rather than viewing it in transmission. As a result documents containing security elements are commonly prematurely and deliberately damaged. 
     The object of the present invention is to provide a security substrate incorporating an elongate security element in which the elongate element is very easily verifiable from both sides of the substrate in apertures which extend through the substrate. 
     SUMMARY OF THE INVENTION 
     The invention therefore provides a substrate having an elongate element partially embedded therein and at least one discrete aperture extending through the fibrous substrate exposing at least a part of the elongate element, wherein at least one edge of the elongate element is exposed in the aperture(s). 
     The invention also provides a method of making a fibrous substrate having an elongate element partially embedded therein, comprising the steps of providing drainage restriction areas on a porous support surface, depositing fibres on to the porous support surface around the drainage restriction areas to form a first layer, bringing the elongate element to lie in contact with the drainage restriction areas of the support surface, and depositing further paper fibres over the first layer to securely embed segments of the elongate element within the substrate between the drainage restriction areas, said drainage restriction areas being such as to substantially prevent the deposition of fibres thereon before and after the elongate element is laid thereover and to thereby form at least one discrete aperture extending through the fibrous substrate, wherein at least one edge of the elongate element is exposed in the aperture(s). 
    
    
     
       Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings. 
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a security document made from a substrate according to the present invention; 
         FIGS. 2 to 7  are cross-sectional side elevations of steps involved in the method of making a fibrous substrate according to the present invention; 
         FIGS. 8 ,  9 , and  11  to  13  are plan views of alternative embodiments of the substrate of  FIG. 1 ; 
         FIG. 10  is a cross sectional side elevation of the substrate of  FIG. 9 ; 
         FIG. 14  is a plan view of pages cut from the substrate of  FIG. 1  to be used to provide a booklet; 
         FIG. 15  is a plan view of a sheet of the substrate made by the present invention to be cut into smaller sheets; and therefor. 
         FIG. 16  is a plan view of a sheet cut from the subsrate of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The fibrous substrate  16  according to the present invention is illustrated in  FIG. 1  and comprises an elongate security element  13  partially embedded within the substrate  16 , having one or more apertures  17  extending through the substrate  16  exposing short lengths of the security element  13 . In other embodiments of the invention, for example as shown in  FIGS. 8 ,  9 ,  10  and  12 , the width and/or the positioning of the security element  13  is such that only one edge of the element  13  is exposed in the aperture(s)  17 . 
     The method of manufacturing a security substrate according to the present invention is illustrated firstly with reference to  FIGS. 2 to 7 . A porous support surface, for example in the form of a cylinder mould cover  10 , is produced in a known way. The mould cover  10  has a plurality of drainage restriction regions  12 . These can, for example, be provided by fixing a blinding material to the mould cover  10 . The blinding material is typically a metal which is welded to the cylinder mould cover  10  (see  FIG. 3 ). Other suitable blind materials are wax, polymer or any other material which can be securely attached to the cylinder mould cover  10  to prevent drainage of water from fibrous stock  11  and hence fibre deposition. These drainage restriction regions  12  define the shape of the apertures  17  formed in the final substrate  16 . 
     In a known manner, the cylinder mould cover  10  is rotated in a vat of fibrous stock  11  as illustrated in  FIG. 2 . As it rotates, an elongate security element  13  is brought into contact with the cylinder mould cover  10  below the level of the fibrous stock  11 . This means that a layer  14  of fibres has already been deposited onto the cylinder mould cover  10  to form, say, a 40 gsm sheet (see  FIGS. 4 and 5 ). Once the security element  13  is brought into contact with the drainage restriction regions  12 , further fibres  15  are deposited on top of the layer  14  to form the remainder of the substrate  16  to, typically, 80 to 90 gsm (see  FIGS. 5 and 6 ). It should of course be noted that in packaging applications the substrates used can have much higher grammages, for example in the order of 250 gsm. 
     The positioning of the security element  13 , with respect to the drainage restriction regions  12  must be determined in the context of whether the element  13  is to be wholly or partly exposed in the apertures  17  (i.e. one edge or both) and this may be affected by the width of the element  13  also. 
     The security element  13  may be impermeable, if it is to be exposed along both of its edges as shown in  FIG. 1 . However it may have a permeable portion  30 , as shown in  FIGS. 9 and 10 , if the element  13  is to have only one edge exposed and the element  13  is relatively wide as compared with the width of the aperture  17 . The permeable portion  30  helps to anchor the element  13  within the substrate  16 . Alternatively, a layer of adhesive may be provided on the element  13  instead of the permeable portion  30 , to assist in anchoring it within the substrate  16 . 
     The security element  13  preferably has-a width of at least 0.5 mm, and more preferably in the range of 0.5 mm to 6 mm, and more preferably in the range of 0.5 mm to 2 mm. 
     Thus, as mentioned above, a layer of fibres is laid down on the cylinder mould cover  10  prior to the introduction of the security element  13 . However, whilst the drainage restriction regions  12  would retain little or no covering of paper fibres before the elongate element  13  is brought into contact therewith, full coverage is obtained in the surrounding areas between the drainage restriction regions  12 . Equally, because of the impermeable nature of the elongate element  13  and the drainage restriction regions  12 , there is little or no covering of fibres retained over the area occupied by the drainage restriction regions  12 , after the element  13  has been brought into contact. During the formation of the apertures  17 , some fibres may deposit in the gaps on either side of the elongate element  13  which is narrower than the width of the drainage restriction regions  12  (designated by numeral  19  in  FIG. 6 ). However because of the drainage restriction regions  12 , the substrate  16  cannot properly form in the region  19 . If required, any such unwanted fibres may be removed during subsequent processing steps. 
     Thus, when the substrate  16  is removed from the cylinder mould cover  10  (see  FIG. 7 ), whilst the substrate  16  incorporates the elongate element  13 , the elongate element  13  is exposed in apertures  17  extending through the substrate corresponding to the drainage restriction regions  12 . Segments  18  of the elongate element  13 , between the apertures  17 , are wholly embedded within the substrate  16 . 
     In a modification of the present invention, the cylinder mould cover  10  is produced in a known way, using dies to form the wire by embossing to form one or more raised areas, which define the shape of the apertures  17  in the final substrate  16 . The peaks of the raised areas are then provided with drainage restriction regions  12  to form the apertures  17 . 
     One preferred material for the element  13  is a PET strip of, say, 50 microns thickness as this would help to maintain the “bulk” of the paper  16  over the windowed region. However, other materials such as OPP, PE or PET with other thicknesses may be used. Typically anything from 12 microns upwards can be used. 
     Alternative embodiments of the invention is illustrated in  FIGS. 11 and 12 , in which the apertures  17  are used in conjunction with traditional windows  25 , as described in EP-A-0059056, EP-A-0229645 and EP-A-0625431, in which neither edge of the security element  13  is exposed.  FIG. 11  shows both edges of the element  13  exposed in an aperture  17 , whilst  FIG. 12  shows only one of its edges exposed. 
     The elongate element  13  may be used as a display surface for indicia, for example de-metallised images, holographic images, colour-shifting areas, print or combinations of any or all of these which are highly visible in the apertures  17 . The element  13  may include different security features along its length, such that a different feature can be seen in consecutive apertures  17 . 
     When viewed from either side of the substrate  16 , the security element  13  itself can be seen in the apertures  17  as a transparent, shiny, coloured or metallised area which may bear indicia, information and/or imagery. More specific examples include the following:
         de-metallised security elements  13 , which may  comprise areas of substantially removed metal to take advantage of the transparency of the base film and provide a large area of transparency in the aperture  17 ;   holographic security elements  13 , which could comprise areas of full metal and half-tone screens to provide partial transparency and/or no metal. Under certain viewing conditions, with no metal, a holographic image is still visible in the aperture  17 . Coatings, such as ZnS, having a high refractive index may also be used instead of metal as the reflection enhancing layers. These coatings are essentially transparent;   security elements  13  with front to back print registration, in which features are printed which would clearly exhibit Moiré patterns from both front and back if a counterfeit were attempted. Alternatively, such patterns could be produced on a transparent film prior to insertion of the security element  13  into the paper as a security feature itself. The exact reproduction of such patterns are very difficult to mimic;   security elements  13  with different coloured print showing on the front to the back. The print may be on either side of the security element  13  or both on the same side, with one colour hidden by the other on one side but showing through on the other side;   security elements  13  comprising or having coatings of liquid crystal, colourshift, thermochromic, photochromic, and iridescent materials to exhibit colour changes within the apertures;   security elements  13  comprising or having coatins of luminescent or magnetic materials;   security embossing of a transparent film forming the base of the security element  13  with a security design (e.g. a latent images such as those disclosed in EP-A-433330) created during the printing process. These may be blind embossed to produce a tactile/visible feature or could include printing inks to further enhance visibility;   security elements  13  have, a matt coating of a similar; colour to the substrate, such that it is only visible in the apertures  17  or any windows  25 ;       

     The paper  16  described above can be cut and printed to make all forms of documents, including security documents such as banknotes, cheques, travellers cheques, identity cards, passports, bonds etc or non-security documents such as stationary, labels etc. 
     The positioning of the apertures  17 , and therefore the design of the drainage restriction regions  12 , can be such that when a continuous sheet of fibrous substrate  16  is finished and cut to form discrete sheets, each discrete sheet may have one or a plurality of apertures  17  therein. Within each aperture  17  the security element  13  can clearly be seen extending from one side to the other of the apertures  17  (in the machine direction of the paper). The apertures  17  may be circular as illustrated in the accompanying drawings, or any other shape, for example as shown in  FIG. 13 . The apertures  17  may also define characterising information, such as indicia, logos or the like. The shape of the apertures  17  may also relate to information elsewhere on the document, such as print and/or security devices. 
     Where sheets made from the substrate  16  are intended to be used in the form of a booklet, for example as pages of a passport, the sheets may be cut to include a single aperture  17  on each sheet, but at staggered positions. When the sheets are bound together in the booklet, flicking through the pages at a reasonable speed would give the impression of an aperture moving and therefore provides a simple form of verification. This is illustrated in  FIG. 14  with three pages  20 ,  21  and  22 , which will be bound together along the left hand edges. Any missing pages would clearly show the aperture movement out of sequence and therefore provide an anti-tamper feature. 
     The security element  13  may also be used as part of a self authenticating feature, such as those described in EP-A-0930979 or EP-A-0256176. 
     The substrate  16  may also be cut in a manner which provides half an aperture  17  along one or more edges of a discrete sheet cut from the substrate  16 . As shown in  FIG. 15  substrate  16  can be cut into two separate discrete sheets  23 ,  24  along the line XX. As this cutting line passes through the aperture  17  and elongate element  13 , a notch will be left in the edge of each of the sheets  23 ,  24  in which an end of the elongate element  13  is exposed, as shown in  FIG. 16 .