EP1965986A2

EP1965986A2 - Improvements in security substrates

Info

Publication number: EP1965986A2
Application number: EP06820536A
Authority: EP
Inventors: Simon Marchant; David Bray; Paul Howland
Original assignee: De la Rue International Ltd
Current assignee: De la Rue International Ltd
Priority date: 2005-12-20
Filing date: 2006-12-15
Publication date: 2008-09-10
Anticipated expiration: 2026-12-15
Also published as: GB0625089D0; GB0525886D0; GB2433469B; CA2629287A1; RU2393099C2; EP1965986B1; WO2007071939A2; WO2007071939A3; GB2433469A; RU2008129777A

Abstract

The present invention relates to improvements in security substrates having security features. The security substrate comprises a fibrous base substrate and a fibrous tape incorporated therewith. The fibrous tape has at least one aperture wherein the shape of the at least one aperture is indistinct when the security substrate is viewed in reflected light, but is distinct when the security substrate is viewed in transmitted light.

Description

IMPROVEMENTS IN SECURITY SUBSTRATES

The present invention relates to improvements in security substrates having security features. More specifically the present invention relates to a fibrous substrate, such as paper, comprising an integral fibrous tape which has visible apertures in the form of holes and/or perforations. When the tape is incorporated into the base substrate it, and therefore the finished substrate, has a different appearance when viewed in reflection compared to its appearance when viewed in transmission.

It is generally known to include elongate elements in paper or other substrates, usually as a security feature. Such elements can be threads, strips or ribbons of, for example, plastics film, metal foil, metallised plastic, metal wire. These elongate elements are included in the thickness of the substrate to render imitation of documents produced therefrom more difficult. These elements help in the verification of the 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, fluorescence, optically variable effects and thermochromic behaviour.

As a further security feature, it has been found to be particularly advantageous to provide windows in one side of the surface of the substrate, which expose such elongate elements at spaced locations. Examples of methods of manufacturing 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 to form raised regions and bringing an impermeable elongate security element into contact with the raised regions of the mould cover, prior to the contact entry point into a vat of aqueous paper stock. Where the impermeable security element makes intimate contact with the raised regions of the embossing, no fibre deposition can occur and windows are formed in the surface of the paper. After the paper is fully formed and couched from the cylinder mould cover, water is extracted from the wet fibre mat and the paper is passed through a drying process. In the finished paper the regions of the security element which are exposed in the windows are visible in reflected light on one side of the paper, which is commonly used for mainly banknotes.

EP-A-0229645 describes a method using two cylinder moulds to produce two separate plys of paper, with a security thread introduced in between the two layers. The option of incorporating holes in both layers by, for example, incorporating drainage restriction devices on the mould covers is disclosed in the specification. The resulting holes can be registered to produce windows on each side of the thread. This method has a major drawback in that the two cylinder moulds need to be exactly the same diameter and linked by a registration system which renders production of the paper extremely expensive. This document also fails to teach how to actually achieve registration.

Based on the desire to be able to display as much information or indicia as possible in the exposed regions, it has also been recognised that it would be highly advantageous to be able to expose the elongate element on both sides of the paper, or other substrate, in which it is embedded. EP-A-0059056 suggests that this could be achieved by using sufficiently large impervious projections on the cylinder mould. The disadvantage with the method described in this specification is that the holes produced by the drainage limiting devices need to be covered up and this means that rather wide threads have to be used, which increases the cost of the paper. Another disadvantage of this method is that the windows on each side necessarily coincide.

EP-A-1630285 describes an alternative method for manufacturing a paper substrate incorporating an elongate impermeable element which is exposed in windows in both surfaces of the substrate. This method involves a modification to the cylinder mould papermachine with the requirement of an additional moving belt under the conventional cylinder mould. Such a modification is non- ideal and increases the cost and complexity of the process.

GB2397582 describes a further alternative method for manufacturing a paper substrate incorporating an elongate impermeable element which is exposed in windows on both -A-

surfaces of the substrate. In this method the security element comprises a plurality of wide regions separated by narrow regions, the wide regions being of a width which obstruct the deposition of fibres. The elongate element is brought into contact with a cylinder mould cover having window forming means such that the narrow regions form windows in the conventional manner as in EP-A-0059056 and the wide regions, by virtue of obstructing deposition, form windows in the opposing surface. The main limitation with this method is that the profile of the elongate element has to be tessellated. This tessellated profile increases the expense for producing the elongate element as single elements have to be produced using die-stamping or laser cutting rather than simply slitting from a wide web.

The use of perforations in secure documents is known in the prior art. WO97/18092 describes a security document having a pattern of fine perforations that are visible when the document is viewed in transmitted light, whilst they are invisible when viewed in reflected light. In this and other prior art examples the whole document is perforated typically in a final processing step such as mechanical punching or laser cutting.

It is therefore an object of the present invention to provide an improved security substrate wherein apertures, such as perforations or holes, are formed in a first fibrous tape which is then integrated into the main fibrous substrate such that the final substrate has a different appearance when viewed in reflection compared to its appearance when viewed in transmission. The invention therefore comprises a security substrate and a fibrous tape incorporated therewith, said fibrous tape having at least one aperture wherein the shape of the at least one aperture is indistinct when the substrate is viewed in reflected light, but is distinct when the substrate is viewed in transmitted light.

Preferably fibres from the base substrate form inside the at least one aperture and form a fibrous layer on the surface of the tape around a perimeter of the aperture. The fibres thereby disguise the perimeter.

The invention also provides a method of forming a security substrate comprising the steps of forming a fibrous tape, said fibrous tape having at least one aperture therein, forming a fibrous base substrate and integrating the fibrous tape in the base substrate during the formation of the base substrate.

It is a further object of the present invention to provide an improved method of manufacturing fibrous security substrates which enable the incorporation of an elongate impermeable element which is exposed at windows in both surfaces of the fibrous security substrate.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a plan view of a security substrate according to the present invention; Figure 2 is a plan view of a small section of the substrate of Figure 1;

Figure 3a is a cross-section of the fibrous substrate of Figure 2 on the line II-II;

Figures 3b and 3c are equivalent cross-sections to that of Figure 3a for alternative embodiments of the substrate;

Figure 4 is a plan view of a web of substrate from which the fibrous tapes for the security substrate of Figure 1 are formed;

Figure 5 is a flow chart illustrating the steps of the preferred method of manufacturing the substrate of Figure 1;

Figures 6a, βb and 6c are schematic representations of parts of a cylinder mould machines for use in the manufacture of the substrate of Figure 1;

Figure 7 is a plan view of an alternative security substrate to that of Figure 1;

Figure 8 is a plan view of a further alternative security substrate viewed in reflected light;

Figure 9 is a plan view of the security substrate of Figure 8S- viewed in transmitted light;

Figure 10 is a plan view of a further alternative security substrate according to the invention; Figure 11 is a cross-sectional side elevation of a further alternative security substrate according to the invention;

Figures 12 and 13 are plan views of further alternative security substrates according to the present invention.

Figure 14 is a schematic representation of parts of a cylinder mould machine for use in the manufacture of a further embodiment of the substrate of the present invention;

Figure 15 is cross sectional side elevation of a portion of the cylinder mould cover of the machine of Figure 14 on the line XV-XV;

Figure 16 is a cross sectional side elevation of a portion of a web of substrate produced on the machine of Figure 14 on the line XVI-XVI of Figures 17 and 18;

Figures 17 and 18 are plan views of the front and back of a security substrate of Figure 16;

Figures 19 and 20 are plan views of the front and back of an alternative substrate to that of Figure 16;

Figures 21 and 22 are front and rear elevations of a portion of tape for use in the substrate of the present invention; Figure 23 is a cross sectional side elevation of a section of the cylinder mould cover of the paper machine used to produce the tape of Figures 21 and 22; and

Figures 24 and 25 are plan views of the front and back of another alternative embodiment of a security substrate.

The security substrate 10 of the present invention comprises a fibrous base substrate 11 into which is integrated a fibrous tape 12, in which at least one aperture 13, in the form of one or more perforations and/or holes, has first been formed such that the fibres from the base substrate 11 interact with the aperture (s) 13.

Figure 1 illustrates a fibrous substrate 10 according to the present invention comprising an integrated fibrous tape 12 where the tape 12 is exposed at one of the surfaces 15 of the finished substrate 10. The tape 12 comprises an array of apertures 13 in the form of perforations which have been filled by fibres of the base substrate 11.

Figure 2 is an enlarged view of one of the perforations 13 showing how the fibres from the base substrate 11 extend beyond the perforation 13 of tape 12 and partially cover the surface of the tape 12 in the region 14 around the perimeter of the perforation 13.

Figure 3a illustrates a cross-section of the section of the fibrous substrate 10 shown in Figure 2. It is the interaction of the fibres of the base substrate 11 with the perforations 13 in the tape 12, characterised by the overlap area 14, that provides the unique optically variable effect. The fact that the fibres from the base substrate 11 slightly overlap the tape 12 means that, when viewed in reflection, the perforations 13 in the tape 12 are not distinct or clearly defined. Thus any image or identifying information formed by the perforations 13 in the tape 12 is blurred and not easily resolved with the naked eye. However on viewing in transmission, the perforations 13 are distinct and clearly defined along with any associated image or identifying information.

In the preferred method of producing the present invention, as illustrated in Figures 4 to 6, a first fibrous web 17 is produced comprising a number of tapes 12 aligned in parallel strips. The apertures 13 can be introduced into the tapes 12 during the papermaking process by preventing fibre deposition in localised areas by blinding or sealing the cylinder mould cover. Alternatively the tapes 12 can be perforated in a subsequent secondary process, for example by laser cutting or mechanical punching.

An optional adhesive coating can be applied to the first web 17 using a conventional size bath in which the web 17 is submerged in an adhesive resin. A conventional size press can also be used comprising of a pair of rolls, into the nip of which an adhesive is applied through which the dry or partially dry web is passed. Alternatively the adhesive may be applied to the first paper web 17, using conventional coating methods such as gravure coating. An alternative to using an adhesive coating is to add thermosoftening fibres to the furnish of the paper tapes 12 such that on heat activation during the drying of the base substrate 11 the fibres from the tape 12 fuse to the base substrate 11. The first fibrous web 17 is then slit along either side of the rows of apertures 13 along slitting lines 16 to produce a plurality of tapes 12.

The base substrate 11 and tape 12 are preferably made from cotton-based paper stock, but alternatively wood based pulp or synthetic fibres or a mix of natural and synthetic fibres can be used. Preferably the tape 12 is a low permeable fibrous tape and is produced using a cylinder mould paper machine to enable complex security features to be incorporated, although other papermaking processes could be used such as the Fourdrinier process. The permeability of a fibrous tape 12 can be adjusted by varying the mesh size of the cylinder mould cover 21. A conventional banknote low permeable paper substrate containing complex security features such as a watermark and a partially embedded polymeric security element would be formed on a fine mesh with a typical mesh size being 70 (warps per inch) by 48 (wefts per inch) (70/48) . Tapes 12 of varying permeability may be employed in the current invention with the only requirement being that the final perforated tape 12 has sufficient handling strength to be integrated into the base substrate 11. For the purpose of this invention a low permeable fibrous tape 12 is one which when placed against a paper forming mesh (for e.g. a cylinder mould cover) restricts drainage and inhibits fibre deposition. Typically the fibrous paper tape 12 suitable for use in the current invention will have a Bendtsen porosity in the range 0 to lOOmls/min.

If the tape 12 is not used to carry complex security features requiring a low permeability (for example 0 tolOO mls/min Bendtsen porosity) , then it is possible to use a more permeable tape 12. A permeable tape 12 can be produced by using a cylinder mould cover 21 with a coarse mesh size, for example a typical mesh size would be 20 (warps per inch) by 20 (wefts per inch) 20/20. Paper produced from a coarse mesh comprises a plurality of discrete areas having a lower fibre density than the rest of the web. Water can easily pass through the areas of lower fibre density resulting in a low permeable substrate. An added advantage of using a coarse mesh is that the tape 12 will have a very obvious wire mark, which is readily apparent when the final sheet is viewed in transmission thus providing additional security and aesthetic benefits. If a distinct wire mesh is not required, then permeable paper can be produced by using fibres especially selected and treated to give a paper with a high permeability.

Other methods may be used to make high permeability paper including the use of electrotypes to produce small regions of reduced grammage paper. Another method is to apply waterjets through a cylinder rotating on the formed, but still wet, paper mat. The cylinder is partially blinded by a patterned stencil. Where the pattern is open, water passes through the cylinder and displaces the paper fibres causing low, or even zero, grammage regions that are more porous than the adjacent regions. Such methods could result in specific regions of the tape 12 having high permeability compared to other parts of the tape 12.

A web of the base substrate 11 is preferably produced using a cylinder-mould process, as shown in Figure 6a. A cylinder-mould papermachine comprises a vat 18 containing a suspension of paper fibres 19 in which dips the major portion of a cylinder 20 arranged on a horizontal axis. The surface of the cylinder 20 comprises a cylinder mould cover 21 formed from a wire mesh. Liquid is drawn through the mesh as the cylinder 20 is rotated causing paper fibres 19 to deposit on the mesh and form a web of the fibrous substrate 11 that is couched from the cylinder 20 by a couch roll 22 and conveyed away.

The above-mentioned optically variable effect of the present invention arises because fibres 19 from the base substrate 11 are not completely constrained to the apertures 13 in the tape and overlap the tape 12 forming a fibrous surface layer around the perimeter of the apertures 13. The degree and pattern of overlap is unique to each aperture 13 but the result is to blur the appearance of the original apertures 13 in reflected light. The presence of the overlapping fibres can be identified with the naked eye and provides an additional security benefit. The position at which the tape 12 contacts the cylinder mould 20 during the manufacture of the base substrate 11 controls the formation of the fibrous surface layer around the perimeter of the apertures 13 in the tape 12.

In a preferred embodiment the tape 12 is fed into the vat 18 at a point such that the cylinder mould cover 21 has already acquired a substantial coating of fibres 19 before the tape 12 makes contact, as shown in Figure 6a. In the case of a low permeable tape once the tape 12 has made contact with the formed substrate 11 little or no further fibres 19 deposit over the tape 12, however fibres 19 continue to deposit adjacent to the tape 12 and also fill up the perforations 13 within the tape 12 resulting in the tape 12 being exposed on the back surface 15 of the security- substrate 10. The back surface 15 is the one facing away from the cylinder mould cover 21 during formation of the substrate 10. The front surface 23 is the one which is facing the cylinder mould cover 21.

Referring to Figure 3a, the thickness (y) of the tape 12 is preferably between 20-70% of the thickness (z) of the base substrate 11 and more preferably between 40-70% of the thickness (z) of the base substrate 11. The thickness (x) in Figure 3a is the thickness of fibres of the base substrate 11 that have been deposited on the cylinder mould cover 21 before the tape 12 contacts the cylinder mould cover 21. The thickness (x) is preferably between 20-70% of the thickness (z) base substrate and more preferably between 30-50% of the thickness (z) of the base substrate 11. In order for fibres 19 to fill the perforations 13 in the tape 12 and overlap the tape 12 forming a fibrous surface layer around the perimeter of the perforations 13, the point at which the tape 12 contacts the mould cover 21 is controlled such that the combined thickness (x) of the fibres and the tape thickness (y) is preferably less than the final thickness (z) of the base substrate 11.

The incorporation of the tape 12 in the base substrate 11 as described in relation to Figure βa is such that there is a substantial coating of fibres 19 on the front surface 16 of the tape 12 which improves the durability of the final security substrate 10. In an alternative embodiment a low permeable fibrous tape 12 is brought into contact with the cylinder mould cover 21 before it enters the vat 18 as shown in Figure βb. As in the previous embodiment the fibres 19 from the base substrate 11 fill up the perforations 13 within the tape 12 and overlap the tape 12 forming a fibrous layer on the surface of the tape 12 around the perimeter of the perforations 13. The difference in this embodiment is that there is, in addition to the tape 12 being exposed on the back surface 15 of the security substrate 10, negligible fibre coverage on the opposite front surface 23 resulting in the tape 12 being exposed on both sides of the security substrate 10. In this embodiment, and with reference to Figure 3a, the thickness (x) is approximately equal to zero.

In an alternative embodiment illustrated in Figure 6c a low permeable fibrous tape 12, comprising one or more perforations 13, is incorporated into the base substrate 11 in the same manner as that described for elongate elements in EP-A-00059056. The technique involves embossing the cylinder mould cover 21 to form raised regions 40 and bringing the tape 12 into contact with the raised regions 40 of the mould cover 21, prior to the contact entry point into a vat of aqueous paper stock 19. Where the low permeable tape 12 makes intimate contact with the raised regions 40 of the embossing, no fibre deposition can occur and windows 32 are formed in the front surface 23 of the base substrate 11. After the finished substrate 10 is fully formed and couched from the cylinder mould cover 21, water is extracted from the wet fibre mat and the finished substrate 10 is passed through a drying process. In the finished substrate 10 the regions of the tape 12 which are exposed in the windows 32 are visible in reflected light when viewed from the front surface 23 of the substrate 10.

Figure 3b illustrates an equivalent cross-section to that shown in Figure 3a of a region of the finished substrate 10 where a perforation 13 in the tape 12 was in contact with a raised region 40 on the cylinder mould 21. In this case the fibres 19 from the base substrate 11 fill up the perforation 13 within the tape 12 and overlap the tape 12 forming a fibrous layer of thickness (w) on the surface of the tape 12 around the perimeter of the perforations 13. In the raised regions the tape 12 contacts the cylinder mould cover 21 before entering the vat and is therefore exposed on both sides of the security substrate 10, and with reference to Figure 3a, the thickness (x) is approximately equal to zero.

Figure 3c shows the equivalent cross-section to Figure 3b for the case where a perforation 13 in the tape 12 is coincident with gap 42 between two raised regions 40 on the cylinder mould cover. The fibres 19 which form underneath the tape 12 inhibit the drainage through the perforation 13 such that the thickness (w) of the overlapping surface layer is reduced compared to the case where the perforations 13 are in contact with the raised regions 40.

The difference in the thickness (w) of the overlapping surface layer, illustrated in Figures 3b and 3c, results in the appearance of the perforation 13 in the tape 12 varying depending on whether it coincides with a raised region 40 on the cylinder mould cover 21 during its incorporation into the base substrate 11. When the back surface 15 of 'the substrate 10 is viewed in reflection the aperture/ perforation 13 is more disguised and less readily apparent in the regions originally in contact with the raised regions 40 of the cylinder mould cover 21 compared to the regions that were coincident with the gaps 42 between the raised regions 40. This provides an additional optically variable effect, when viewed in reflection, that increases the difficulty for a potential counterfeiter. In one embodiment the tape 12 may comprise a large aperture which both partly coincides with the raised regions 40 and gaps 42 on the cylinder mould cover 21. In this case the appearance of a single aperture in reflection will vary across its length.

An additional paper layer may be applied to the back surface 15 of the security substrate 10 to cover the exposed back surface of the tape 12. The additional layer can be applied by a separate lamination process or produced parallel to the production of the main substrate on a short former and brought together in the wet section of the paper machine. When the security substrate 10 is viewed in reflection the additional paper layer will further disguise the presence of the perforations 13 in the paper tape 12.

There is no width restriction to the tape 12 of the present invention, but preferably the width of the tape 12 is in the range 5-50mm and more preferably 10-30mm.

The at least one aperture 13 of the tape 12 of the present invention may comprise a variety of forms. The tape 12 may comprise one large aperture 13 shaped in the form of an identifying image or an array of smaller perforations 13 arranged to form an identifying image. The only size requirement of the apertures/ perforations/holes is that they are visible to the naked eye. Preferably the mean diameter of the apertures 13 would fall in the range l-50mm and more preferably 5-30rnm.

As mentioned above, the apertures 13 may be formed during the papermaking process of the tape 12. WO-A-0039391 describes a method of making single ply paper with fibre free regions by blinding one or more selected areas of a cylinder mould cover, and then depositing a layer of paper fibres onto the cylinder mould cover around the blinded areas. The blinded areas are impermeable which substantially prevents the deposition of fibres. A similar method is described in WO-A-03054297. The blinded areas can be created by attaching a suitably shaped metallic or polymeric element to the cylinder mould cover.

Alternatively the aperture (s) 13 can be created by perforating the tape 12 once it has been fully formed and prior to incorporating it into the base substrate 11.

Examples of suitable methods for perforating the tape 12 include stamping, die-cutting, grinding, laser cutting, and water jet cutting.

It is not essential for the tapes 12 to have a linear edge and the edge of the tape 12 could have a curved or geometric pattern cut e.g by a laser.

Experimental work has shown that where the edge of the tape 12 has a thinner fibrous layer than the main body of the tape 12 a higher level of adhesion to the base substrate 11 is observed than for a tape 12 with a uniform thickness. This is because when the tape 12 is rewetted on insertion into the vat 18 during the production of the base substrate 11, the fibres in the thin fibrous layer of the tape 12 have an increased freedom of movement compared to a thicker layer and can entangle and bond more efficiently with the fibres of the base substrate 11.

A preferred method of manufacturing a tape 12 with a thin fibrous edge is to attach continuous thin wires circumferentially around the cylinder mould cover 21 to mark the edge of each tape 12. The wire will result in a significant decrease in drainage and fibre deposition forming a light line in the substrate along the edge of each tape 12. The substrate is significantly thinner along these lines 16 and can be torn by a suitable roller and rewind arrangement. The tearing action, as opposed to a slitting action, results in a frayed fibrous edge which further enhances the bonding of the tape edge into the base substrate 11.

In a further embodiment the tape 12 can be given different aesthetic properties to the base substrate 11. For example the tape 12 could be formed from red coloured fibres resulting in a coloured perforated tape 12. Alternatively the tape 12 could have a higher or lower opacity than the base substrate 11. In yet a further example the tape 12 could be fully or partly formed from phosphorescent or fluorescent fibres. In alternative embodiments the tape 12 may be coloured by a conventional printing process prior to insertion into the base substrate 11. A conventional printing process enables a design to be applied to the tape 12 rather than an all-over colouring.

In addition to the patterned array of apertures or perforations 13, the tape 12 may comprise additional security features using the same methods as for a normal banknote substrate. Such features may include multitonal watermarks, single tone watermarks commonly known as electrotypes, polymeric elongated elements including embedded and partially embedded threads and fibres, silks or planchettes with associated functional properties. The functional properties can include UV excitable fluorescent or phosphorescent emissions, magnetic properties and IR excitable visible emissions.

Multitonal watermarks can be formed in the tape 12 by embossing the wire mesh of the cylinder mould cover 21 attached to the cylinder mould 20. When the cover 21 is embossed with a detailed image, the fibres 19 deposit with a lesser or greater thickness on the raised and depressed elements of the embossing to form a fully three-dimensional watermark in the paper. An alternative security feature is a single tone light element, commonly known as an electrotype watermark. This is created by attaching a metallic electrotype or a polymeric sealing compounds to the cylinder mould cover 21, resulting in a significant decrease in drainage and fibre deposition forming a light mark in the paper.

In a further embodiment of the present invention the tape 12 may comprise an elongated security element or thread. The inclusion of elongate elements or security threads into security paper is well known and has been widely described within patent literature. Such threads may be wholly or partially embedded in the tape 12. It is usual to refer to partially embedded threads as being windowed, as the thread surfaces at regular intervals on the substrate surface like a series of windows. A number of methods for producing security papers with so-called windowed threads have been described one of which is described in EP-A-59056. Paper is still regularly produced by the method described within EP-A-0059056 and sold commercially under the trade name Stardust^®.

In a further embodiment of the present invention a fibrous tape 12 has an elongate element partially embedded therein and at least one discrete aperture extending through the fibrous tape 12 exposing at least a part of the elongate element, wherein at least one edge of the elongate element is exposed in the aperture (s) 13. A method for producing such a paper web, with an elongate element exposed in an aperture, is disclosed in WO-A-04001130.

A further advantage of the proposed invention is that the production of the tape 12 is solely concerned with the generation of the security features. This allows fibres of a specific type or characteristic to be used in order to optimise the security feature. This is particularly useful for a perforated or holed tape 12 incorporating a watermark where short fibres lead to improved watermark definition. However short fibres result in degradation in strength and durability but the proposed method enables the fibres in the base substrate 11 to be optimised for strength and durability. It is well-known in the papermaking art that the doublefold and tensile strength properties are generally improved by the addition of longer fibres or synthetic fibres and therefore for example the strength of the base substrate 11 could be optimised by using synthetic PVOH fibres as described in EP-A-873448B1. The resultant final substrate will contain a higher quality security feature and exhibit a higher strength and durability compared to when the security feature is incorporated into the substrate during the production of the final document.

The tape 12 may go undergo a number of optional processing steps prior to being incorporated into the base substrate 11. In order to provide additional security, images may be printed onto the tape 12 using conventional security printing techniques such as gravure, screen printing, litho, intaglio etc. The surface of the tape 12 could be modified by embossing or applying tactile inks such that in the final document the tape 12 can be identified by touch.

In order to ensure that the tape 12 is fully bonded to the base substrate 11, a heat sealable or water soluble adhesive can be applied to one or both sides of the tape 12 by standard coating or printing processes. In the preferred embodiment where the tape 12 is to be incorporated into the base substrate 11 such that it surfaces on the back surface 15 of the finished security substrate 10, the adhesive may be applied only over the edge of the tape 12 on the side that surfaces to adhere the fibres from the base substrate 11 that overlap the edge of the tape 12. An additional benefit of the apertures 13 in a low permeable tape 12 is that it increases the adhesion of the tape 12 to the base substrate 11 due to the fact there are substrate fibres present on both sides of the tape 12. Without the apertures 13 the fibres from the base substrate 11 would only be attached to one surface of the tape 12, i.e. the surface that is not exposed on the back 23 of the security substrate 10. However with the apertures 13 present, the fibres from the base substrate 11 fill the apertures 13 and become attached to the tape 12 on the opposite side of the tape 12. A preferred embodiment to enhance adhesion between a low permeable tape 12 and a fibrous base substrate 11 comprises a series of apertures along one or both long edges of the tape 12 (Figure 13) . Alternatively there could be a series of apertures along the middle of the tape (Figure 1) , or an array of apertures covering the whole surface of the tape 12. Experimental work has shown that the adhesion of the tape 12 to the base substrate 11 is optimised if the apertures are of a size in the range 0.5 - 2mm wide by 0.5 to 4mm long and the space between the apertures is in the range 1 - 3mm.

In addition to the incorporation of the tape 12 the base substrate 11 may also comprise traditional banknote security features for example multitonal watermarks, single tone watermarks, embedded or partially embedded polymeric threads and fibres, silks or planchettes with associated functional properties. The functional properties can include UV excitable fluorescent or phosphorescent emissions, magnetic properties and IR excitable visible emissions. The security features are incorporated using conventional techniques in the same manner as described for the tape 12. Optionally the position of the tape 12 is registered to security features in the base substrate 11. The holes or perforations 13 in the tape 12 could be registered to the security features on the base substrate 11 such as watermarks, or electrotypes. For example the tape 12 could be positioned directly under the watermark or adjacent to a watermark such that the image observed due to the holes or perforations is linked to or completes the image of the watermark.

Figures 7 to 13 show a number of alternative embodiments of the present invention. Figure 7 shows an example of a security substrate 10 of the present invention comprising a low permeable paper tape 12 in which the tape 12 comprises a first security feature provided by a plurality of apertures 13 in the shape of stars, which provide identifying information, and a further security feature in the form of a traditional multi-tonal watermark 26. As described above, the fibres from the base substrate 11 are viewed through the apertures 13 in the tape 12. In one embodiment the tape 12, is made from a different coloured furnish to the base substrate 11. For example if the base substrate 11 is substantially white and the tape 12 is a shade of blue, then on viewing the base substrate 11 in reflection, from the exposed tape 12 side, a blue strip will be observed comprising white stars. However because the white fibres from the base substrate 11, fill the star- shaped apertures 13 of the tape 12 and form a surface layer around the perimeter of the apertures 13 the edge of the stars are not distinct and appear blurred and poorly defined when viewed in reflection. The fact that the presence of the white fibres around each star can be identified with the naked eye against the blue background of the tape provides an additional security benefit. A counterfeiter simply printing white stars on a blue background cannot replicate this blurred fibrous edge. In contrast on viewing the document in transmission a sharp image of the stars can be clearly seen against the background of the coloured tape 12. The fact that the tape 12 is of a different colour to the base substrate 11 provides additional security and substantially increases the contrast for the patterned apertures 13 when viewed in transmissive light. Alternatively the tape 12 can be made from the same colour furnish as the base substrate 11 but differ in another visible characteristic such as opacity or density and in this case the identifying information formed from the outline of the perforations 13 will be virtually invisible in reflected light but easily distinguishable in transmitted light.

In a further embodiment illustrated in Figures 8 and 9, the low permeable paper tape 12 comprises an array of small circular perforations 13 arranged to form the numeral 5. In this example a paper tape 12 is made from a paper furnish with a lower opacity than the base substrate 11. The perforations 13 are formed during the paper making process for the tape 12 by blinding the cylinder mould cover on which the paper fibres are deposited. The patterned paper tape 12 is subsequently incorporated into the base substrate 11 as described above. The fibres from the base substrate 11 form in the perforations 13 of the tape 12 and slightly overlap the perimeter of the perforations 13 such that when viewed in reflection the perforated regions are not distinct or clearly defined and a virtually imperceptible "blurred" image of the number 5 is present (Figure 8) . However on viewing in transmission the presence of the tape 12 is immediately noticeable due to the difference in opacity with the base substrate 11 and the perforations 13 of the tape 12 are distinct and clearly defined within the tape 12 as sharp circles defining the numeral 5 (Figure 9) .

Figure 10 shows an example of a security substrate 10 comprising a permeable tape 12, preferably of paper, produced by using a coarse wire mesh. The tape 12 is made from substantially the same furnish as the base substrate 11 and is therefore difficult to see in reflection, but in transmission the tape 12 is characterised by an obvious wire mark which clearly distinguishes it from the base substrate 11. In addition holes 13 in the shape of numerals ^λλl" and ^λλ5" have been produced in the tape 12, prior to its incorporation into the base substrate 11, by laser cutting. As with previous examples the identifying information provided by the holes 13 is not clearly resolved in reflected light, but is sharp and easily apparent in transmitted light.

In an alternative embodiment of a security substrate 10 comprising a permeable tape 12, the permeable tape 12 is impregnated with a transparentising resin or varnish. The varnish can be applied during the production of the tape 12 or as a separate printing or coating process. The transparentising of permeable paper sheet by impregnation with a resin is well known in the prior art, see for example US-A-2021141, GB-A-1489084, US-A-5118526 and US-A-4513056. The paper tape 12 is then perforated in the form of an identifying image and incorporated into the base substrate 11 as described with reference to Figure βa. The impregnated resin reduces the permeability of the paper tape 12 such that when incorporated in to the substrate 11 very few fibres deposit over the tape 12, however the fibres 19 continue to deposit adjacent to the tape 12 and fill the perforations 13 in the tape 12 and overlap the tape 12 forming a fibrous surface layer around the perimeter of the perforations 13. The perforations 13 in the tape 12 thus appear indistinct in reflected light, but sharp and easily apparent in transmitted light. Furthermore in this embodiment the paper tape 12 appears lighter than the base substrate 11 because of the transparentising effect of the impregnated resin.

Figure 11 shows a cross-section of a security substrate 10 comprising a perforated low permeable tape 12 which is of a different colour to the base substrate 11. For example the base substrate 11 is white and the tape 12 is blue. The base substrate 11 comprises a traditional multitonal watermark 30 characterised by a region of irregular thickness in the top surface of the substrate 11. The tape 12 is registered in the cross direction with the watermark 30 such that it is positioned directly under and surfaces on the opposite side of the substrate 11 to the watermark 30. When viewed in transmission the colour of the tape 12 highlights the watermark 30 and draws the eye of the authenticator to the watermark 30. Security is further enhanced by the fact that the position and content of the perforations 13 correlate with the design of the watermark 30 or alternatively the design of the perforations 13 can complete the image of the watermark 30. In this example the watermark 30 is in the form of a large star and the perforations 13 are in the form of small stars positioned above and below the watermark (Figure 12) .

In Figure 13 the security substrate 10 comprises a perforated low permeable tape 12, which contains a partially embedded security element in the form of a thread 31 that is exposed in windows 32. The tape 12 is incorporated into the base substrate 11 as described with reference to Figure 6a with the tape 12 oriented such that the exposed windows face away from the mould cover. As the tape 12 surfaces on the back surface 15 of the substrate 10 the windows 32 are not covered by the fibres of the base substrate 11 and the optical characteristics of a traditional windowed thread are maintained.

The tape 12 in Figure 13 is of a different colour to the base substrate 11. When the substrate 10 is viewed in reflection, from the same side as the surfacing tape 12, a coloured stripe is observed in the middle of which is a windowing polymeric thread 31. In reflection the perforations 13 in the form of the letters "NHM" are blurred and difficult to resolve, but when viewed in transmission the thread 31 is observed as a uniform dark strip and the perforations 13 become readily apparent. The colour of the tape 12 provides additional security as well as attracting the attention of the general public to the security thread 31.

In a further embodiment (not illustrated) the perforated tape 12 incorporates a partially embedded polymeric thread 31 which is registered in the cross direction to a security feature in the base substrate 11. For example the tape 12 in Figure 13 could be positioned directly under a multitonal watermark 30 in the base substrate 11. In this case security can be further enhanced by correlating the design of the watermark 30 with either the design of the perforations 13, shape of the windows 32 or the optical information displayed in the windows 32. For example the polymeric thread 31 could be used to display a holographic design such that the hologram observed in the windows 32 is of the same design as the watermark 30. On viewing the substrate 10 in reflection from the side of the exposed tape 12 a series of windows 32 will be observed with a repeating holographic image, and when viewed in transmission a watermark 30 of the same image will be observed directly behind the windowed thread 31 providing the authenticator with a clear link between the two security features .

In a further embodiment of the present invention the tape 12, made from a low permeable paper, comprising one or more apertures 13 is incorporated into the base substrate 11 in combination with a conventional elongate impermeable element 31 such that the elongate impermeable element 31 contacts the cylinder mould cover 21 through the apertures 13 in the tape 12 and thereby the regions 43 of the elongate impermeable element 31 coincident with the apertures 13 in the tape 12 surface on the front side 23 of the finished substrate 10 in windows 32. The regions 44 of the elongate polymeric element 31 not coincident with the apertures 13 in the tape and positioned on the surface of the tape 12 away from the mould cover 21 will surface on the back side 15 of the base substrate 11 as no fibres will deposit over the low permeable paper tape 12. In this manner the elongate impermeable element 31 is exposed in one or more windows 32 on both the front and backside 23,15 of the finished substrate 10.

Figures 14 to 18 illustrate one embodiment of the proposed invention which enables the incorporation of an elongate impermeable element 31 such that it is exposed at windows 32 in both surfaces 23,15 of the finished substrate 10. A fibrous tape 12 made from a low permeable paper comprises a series of apertures 13 positioned along the tape 12. The apertures 13 may be formed during the paper making process for the tape 12 by blinding the cylinder mould cover 21 on which the paper fibres 19 are deposited. Alternatively the apertures may be formed by perforating the tape 12 once it has been fully formed and prior to incorporating it into the base substrate 11. Examples of suitable methods for perforating the tape 12 include stamping, die-cutting, grinding and laser cutting, water jet cutting and laser cutting.

The tape 12 is incorporated into the base substrate 11 as shown in Figure 14. In this example the tape 12 and the base substrate 11 are made from the same furnish. The tape 12 is combined with an elongate impermeable element 31 immediately before the tape 12 contacts the cylinder mould 20. The elongate impermeable element 31 and tape 12 are brought together such that the elongate element 31 contacts the tape 12 on the side of the tape 12 away from the cylinder mould cover 21. The elongate impermeable element 31 is positioned such that it lies across one or more of the apertures 13 in the tape 12. The combined structure is then brought into contact with the cylinder mould cover 21 (Figure 15) prior to the cylinder mould 20 entering the liquid in the vat 18 with the result that the tape 12 is exposed on the front surface 23 of the finished security substrate 10 (Figure 16) . Furthermore the regions 43 of the elongate impermeable element 31 lying across the apertures 13 in the tape also contacts the cylinder mould cover 21 and likewise are exposed on the front surface 23 of the finished security substrate 10. In the case of a well consolidated low permeable tape 12 the restricted drainage results in few or no fibres 19 being deposited on the back surface 15 of the tape 12, although fibres 19 will continue to accumulate adjacent to the tape 12, with the result that the tape 12 is substantially exposed on the back surface 15 of the finished security substrate 10. Fibres forming the base substrate will continue to form in the apertures 13 in the tape 12 and overlap the tape 12 forming a fibrous layer on the surface of the tape 12 around the perimeter of the apertures 13.

If the elongate impermeable element 31 is sufficiently narrow not to interfere with fibre deposition then fibres 19 will also form over regions 43 of the impermeable elongate element 31 such that it is only exposed on the front side of the final substrate 10. This results in the elongate impermeable element 31 being exposed in alternate windows 32 on the front and back 23,15 of the finished substrate 10 as shown in Figure 17 (front) and Figure 18 (back) . In order to allow fibre deposition the impermeable elongate element 31 will preferably have a width less than 3mm, and more preferably less than 2mm. Alternatively if the elongate element 31 is sufficiently large to interfere with fibre deposition as it is too wide to be bridged by the fibres, regions 43 of the impermeable element 31 will be exposed on both the front and back surface 23,15 of the final substrate 11 (Figures 19 and 20) . In this case the impermeable elongate element 31 preferably has a width greater than 3mm and even more preferably greater than 6mm.

For the embodiments with reference to Figures 14 to 20 the tape 12 and the elongate impermeable element 31 may be delivered into the papermachine in a number of ways. In one method the tape 12 and the elongate impermeable element 31 will be delivered on separate rolls with guide reels being used to ensure they are brought into contact at the correct point. Alternatively the tape 12 and the elongate impermeable element 31 may be brought into contact in a separate step prior to the papermaking process and delivered into the papermachine from the same roll . Although not essential an adhesive layer can be used to bond the tape 12 to the elongate impermeable element 31, this adhesive bond could be formed prior to entry into the papermachine, for example using an adhesive lamination process, or during the papermaking process using a moisture or heat activated adhesive.

In a preferred embodiment the elongate impermeable element 31 is incorporated into the fibrous tape 12 during its fabrication. This can be achieved using the method of making fibrous substrates described in WO-A-04001130. The tape 12, illustrated in Figures 21 and 22 viewed from the front surface 45 and back surface 46, comprises a partially embedded elongate impermeable element 31 and one or more holes 13 which expose both surfaces of regions 47 of the elongate impermeable element 31. The tape 12 also comprises traditional windows 32, as described in EP-A-0059056, in which only one surface of regions 48 of the security element 31 are exposed.

The method of manufacturing the low permeable tape 12 illustrated in Figures 21 and 22 is shown in Figure 23. A porous support surface, for example in the form of a cylinder mould cover 21, is produced in a known way. The mould cover 21 has a plurality of drainage restriction regions 49. These can, for example, be provided by fixing a blinding material to the cylinder mould cover 21. The blinding material is typically a metal which is welded; to the cylinder mould cover 21. Other suitable blind materials are wax, polymer or any other material which can be securely attached to the cylinder mould cover 21 to prevent drainage of water from the fibrous stock 19 and hence fibre deposition. These drainage restriction regions 49 define the shape of the holes 13 formed in the tape 12.

The cylinder mould cover 21 also comprises embossed raised regions 40 which are used to generate the conventional windows 32. The elongate impermeable element 31 is brought into contact with both the raised regions 40 and drainage restriction regions 49 on the mould cover 21 prior to the contact entry point into a vat of aqueous paper stock 19. Where the elongate impermeable element 31 makes intimate contact with the raised regions 40 of the embossing, no fibre deposition can occur and windows 32 are formed in the front surface 45 of the paper tape 12 that was in contact with the mould cover 21. Assuming the impermeable elongate element 31 is not sufficiently wide to prevent fibre deposition, fibres will be deposited over the impermeable element 31 in contact with the raised regions 40 such that it will not be exposed on the back surface 45 of the paper tape 12. In the drainage restriction regions 49 there is little or no covering of fibres. However in the gaps 42, which are flat freely draining regions, full fibre coverage is obtained. Thus when the substrate used to form the paper tape 12 is removed from the cylinder mould 21 the elongate impermeable element 31 is exposed from both sides of the tape 12 in the holes 13 corresponding to the drainage restriction regions 49 and exposed from one surface of the paper tape 12 in the windows 32 corresponding to the raised embossed regions 40. In the regions between the windows 32 and the holes the elongate element 31 is wholly embedded within the tape 12.

The low permeable tape 12, illustrated in Figures 21 and 22, is then incorporated into the base substrate 11 as described with reference to Figure 6b, prior to the cylinder mould 20 entering the liquid in the vat 18, with the conventional windows 32 facing away from the mould cover 21. The tape 12 is exposed on the front surface 23 of the finished security substrate 10. Furthermore the regions 47 of the elongate element 31 lying across the holes 13 in the tape 12 also contacts the cylinder mould 20 and likewise are exposed on the front surface 23 of the finished security substrate 10 (Figure 24) . If the elongate impermeable element 31 is sufficiently narrow not to interfere with fibre deposition then fibres 19 will also from over regions 47 of the impermeable elongate element 40 such that it is only exposed on the front side 23 of the final substrate 10. Fibres forming the base substrate 11 will continue to form in the holes 13 in the tape 12. As the tape 12 is of low permeability it is also exposed on the back surface 15 of the finished security substrate 10 and therefore the conventional windows 32 are not covered by the fibres of the base substrate 11 and therefore regions 48 of the elongate impermeable element 31 are exposed on the back surface 15 (Figure 25) .

The method, for the incorporation of an elongate impermeable element 31 into a base substrate 11 such that it windows on both surfaces 15,23 described in the various embodiments in Figures 14 to 24, allows total control of the degree and position of exposure of the elongate impermeable element 31 within the security substrate 10. For example the elongate impermeable element 31 can be exposed on both surfaces 15,23 of the final substrate 10 in an alternating manner (Figures 15 to 18), or coincident manner (Figure 19), or where the elongate impermeable element 31 can be exposed in a plurality of windows 32 on one surface and only a single window 13 on the second surface (Figures 24 and 25) .

Thus, substrates 10 made according to the present invention are advantageous in that the apertures 13 in the paper tape 12 provides a security feature that is indistinct when the substrate 10 is viewed in reflected light but is distinct when the substrate 10 is viewed in transmitted light. Furthermore the aperture 13 has a second function which is to increase the exposure of the impermeable elongate element 31, not just on one but both surfaces of the substrate, which means that it can be used to its best extent. This is important because such elongate impermeable elements can be expensive to provide.

The elongate impermeable elements 31 are preferably made of clear polyester although other materials may be used, such as polyethylene or polypropylene, and may have a constant or variable width. The elongate impermeable elements typically have a layer of adhesive, which help the embedment within the tape and/or final substrate.

The elongate elements can contain a wide variety of known security features which may include the following:-

a metallic layer, indicia or designs, which appear dark, when the substrate is viewed in transmitted light, compared to the lighter, partly light- transmitting, substrate. When viewed in reflected light, the shiny metallic parts will be clearly seen in the windows;

de-metallised indicia or designs, which may comprise areas of substantially removed metal to take advantage of the transparency of the base film and provide a large area of transparent window;

holographic or diffractive designs, which may comprise areas of full metal and half-tone screens to provide partial transparency and/or no metal;

front to back print registration, in which features are printed which would clearly exhibit Moire 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 element into the paper as a security feature itself. The exact reproduction of such patterns are very difficult to mimic;

luminescent, iridescent, thermochrornic, liquid crystal or magnetic materials;

designs or indicia created by printed inks;

dichroic materials which can have different colours when viewed in transmission and refection, for example as described in GB-A-1552853. These materials are particularly useful where the windows on the front and back of the substrate coincide to form an aperture (as shown in Figure 16) ;

thin film interference devices, as described in EP-A-227423 or liquid crystal polymer films or liquid crystal pigmented inks, such as described in EP-A-435029 or EP-A-863815.

The elongate impermeable elements may be oriented, which means that each side of the element may carry different information, materials or optical effects. Examples include:- - holographic or diffractive materials on a first side of the element, with a thin film interference device on a second side;

- liquid crystal film over a black or dark background on a first side and plain metal on a second side;

different coloured metals on each side, e.g. aluminium on the first side and another metal on the second side. Alternatively one or more coloured transparent lacquers over a metal layer could be used to create a variety of colours;

a magnetic micrometallised thread, such as described in GB-A-2375078;

repeating indicia or security features located in either window or bridge regions on one or both sides of the substrate.

Many other options are available and with such a large exposed area of the element available, it is possible to combine many security or decorative features together on one element.

Following the incorporation of the paper tape 12, the security substrate 10 undergoes further standard security printing processes to create a secure document, including one or all of the following; wet or dry lithographic printing, intaglio printing, letterpress printing, flexographic printing, screen printing, and/or gravure printing. The printed designs are preferably printed both on the substrate 11 and the exposed regions of the paper tape 12. The printed images can subsequently be correlated and registered to images and designs produced by the apertures 13 in the paper tape 12.

The printed image on the exposed regions of the paper tape can be designed such that when the secure substrate 10 is viewed in reflection the printed image disguises the presence of the apertures 13 in the paper tape 12.

The disguising pattern can either be an integrated design or a stand-alone discreet design. The disguising pattern can either be regular or irregular and may consist of one or more of lines, dots, squares, or other small shapes. Preferred designs are those which contain distinctive images or patterns. Other preferred designs are those which have an additional distinct visual element, e.g. indicia within the disguising pattern.

It is also of benefit if the disguising pattern contains distinctive images or patterns itself. This is because of perceptual organisation when the eye views an image, whereby the brain tends to process images on the basis of grouping and, for example, will not clearly perceive the identifying image below.

The security substrate 10 of the present invention is particularly suitable for many types of security documents, include passport, banknotes, tickets of value and authenticity, share certificates and the like.

Claims

CIAIMS :

1. A security substrate comprising a fibrous base substrate and a fibrous tape incorporated therewith, said fibrous tape having at least one aperture wherein the shape of the at least one aperture is indistinct when the security substrate is viewed in reflected light, but is distinct when the security substrate is viewed in transmitted light.

2. A security substrate as claimed in claim 1 in which fibres of the base substrate form a fibrous layer on the surface of the tape around a perimeter of the aperture.

3. A security substrate as claimed in claim 1 or claim 2 in which the at least one aperture comprises a plurality of apertures in the fibrous tape.

4. A security substrate as claimed in any one of the preceding claims in which the fibrous tape incorporates a security feature.

5. A security substrate as claimed in claim 4 in which the security feature is a watermark.

6. A security substrate as claimed in claim 4 in which the security feature is a security element comprising an impermeable plastic substrate.

7. A security substrate as claimed in any one of the preceding claims in which the fibrous tape has a low permeability in the range of 0 to 100 mls/mins Bentdsen porosity.

8. A security substrate as claimed in any one of the preceding claims in which the at least one aperture in the fibrous tape provides identifying information.

9. A security substrate as claimed in any one of the preceding claims in which the at least one aperture in the fibrous tape is of a size visible to the naked eye.

10. A security substrate as claimed in any one of the preceding claims in which the at least one aperture in the fibrous tape has a width in the range lmm to 50mm.

11. A security substrate as claimed in claim 10 in which the at least one aperture in the fibrous tape has a width in the range of 5mm to 30mm.

12. A security substrate as claimed in any one of the preceding claims in which the fibrous tape has a linear edge.

13. A security substrate as claimed in any one of claims 1 to 11 in which the fibrous tape has a non-linear edge.

14. A security substrate as claimed in any one of the preceding claims in which edges of the fibrous tape are thinner than the main body of the tape.

15. A security substrate as claimed in any one of the preceding claims in which the fibrous tape has the same visual appearance as that of the base substrate in reflected light.

16. A security substrate as claimed in anyone of claims 1 to 14 in which the fibrous tape has a different colour to that of the base substrate in reflected light.

17. A security substrate as claimed in any one of preceding claims in which the fibrous tape has a different opacity from that of the base substrate.

18. A security substrate as claimed in any one of the preceding claims in which the fibrous tape is wholly or partially formed from phosphorescent or fluorescent fibres.

19. A security substrate as claimed in any one of the preceding claims in which the base substrate incorporates one or more security features.

20. A security substrate as claimed in claim 19 in which the one or more security features in the base substrate comprise watermarks, security elements and the like.

21. A security substrate as claimed in any one of claims 19 to 20 in which the at least one aperture is registered to a security feature in/on the base substrate.

22. A security substrate as claimed in any one of claims 6 to 21 in which the at least one aperture exposes both sides of at least one portion of a security element being a security feature of the fibrous tape or of the base substrate.

23. A security substrate as claimed in any one of claims 6 to 22 in which the tape further comprises windows in which only one surface of at least one portion of a security element being a security feature of the fibrous tape or of the base substrate is exposed.

24. A security substrate as claimed in any one of claims 6 to 23 in which a security element being a security feature of the fibrous tape or of the base substrate includes more security features .

25. A security substrate as claimed in any one of the preceding claims in which the thickness of the fibrous tape lies in the range of 20 to 70% of the thickness of the base substrate.

26. A security substrate as claimed in claim 25 in which the thickness of the fibrous tape lies in the range of 40 to 70% of the thickness of the base substrate.

27. A security substrate as claimed in any one of the preceding claims in which the depth of fibres covering one side of the fibrous tape lies in the range of 20 to 70% of the thickness of the substrate.

28. A security substrate as claimed in claim 27 in which the depth of fibres covering the one side of the fibrous tape lies in the range of 30 to 50% of the thickness of the base substrate.

29. A security substrate as claimed in claim 27 or claim 28in which the combined thickness of the fibres covering the one side of the fibrous tape and the tape thickness is less than the thickness of the base substrate.

30. A security document made from the security substrate of any one of the preceding claims.

31. A security document as claimed in claim 30 comprising a banknote, document of value, share certificate, passport or the like.

32. A method of forming a security substrate as claimed in any one of the claims 1 to 29 comprising the steps of forming a fibrous tape having at least one aperture therein, forming a fibrous base substrate and integrating the fibrous tape in the base substrate during the formation of the base substrate.

33. A method as claimed in claim 32 in which the base substrate and/or fibrous tape are formed on a cylinder mould papermaking machine.

34. A method as claimed in claim 33 in which the fibrous tape is brought into contact with a cylinder mould cover of the cylinder mould machine after a layer of fibres has already been deposited on the cylinder mould cover.

35. A method as claimed in claim 33 in which the fibrous tape is brought into contact with a cylinder mould cover of the cylinder mould machine mould before a layer of fibres has been deposited.

36. A method as claimed in claim 32 in which the fibrous tape and/or base substrate are formed on a Fourdrinier paper making machine.

37. A method as claimed in any one of claims 32 to 36 in which at least one aperture is formed during the manufacturing of the tape.

38. A method as claimed in any one of claims 32 to 36 in at least one aperture is created after the tape has been fully formed and prior to incorporating into the base substrates.

39. A method as claimed in any one of claims 32 to 38 in which a plurality of tapes are formed from a web of tape substrate, a plurality of wires being attached to a support surface on which the tape substrate is being formed to decrease drainage and fibre deposition and form a light line defining edges of the tapes such the tapes are separable from each other by a tearing action along these lines, said tapes having a frayed fibrous edge.

40. A method as claimed in any one of claims 32 to 39 further comprising the step of incorporating a security element into the base substrate adjacent the tape.

41. A method as claimed in claim 40 in which the tape includes at least one aperture through which the security element contacts a support surface of a papermaking machine during the formation of the base substrate.

42. A method as claimed in claim 40 or claim 41 in which the tape and security element are combined prior to incorporation in the base substrate.

43. A method as claimed in any one of claims 40 to 42 in which the tape and security element are bonded prior to incorporation within the base substrate.

44. A method as claimed in any one of claims 40 to 43 in which the security element is incorporated into the fibrous tape during its fabrication said tape including at least one hole which exposes both sides of at least one portion of the security element.

45. A method as claimed in claim 44 in which the tape further comprises windows in which only one surface of at least one portion of the security element is exposed.

46. A method as claimed in any one of claims 40 to 45 in which the security element includes more security features.

47. A security substrate formed by any one of the method claims 32 to 46.

48. A security document made from a security substrate of claim 47.

49. A security document as claimed in claim 48 comprising a banknote, document of value, share certificate, passport or the like.

50. A security substrate substantially as hereinbefore described with reference to and as shown in the accompanying drawings .

51. A method manufacturing a security substrate substantially as hereinbefore described with reference to and as shown in the accompanying drawings .