GB2586576A

GB2586576A - A security sheet

Info

Publication number: GB2586576A
Application number: GB1908252.8A
Authority: GB
Inventors: Bobat Shireen; Sugdon Matthew; Husmann Christoph
Original assignee: De la Rue International Ltd
Current assignee: De la Rue International Ltd
Priority date: 2019-06-10
Filing date: 2019-06-10
Publication date: 2021-03-03
Anticipated expiration: 2039-06-10
Also published as: GB201908252D0; EP3980272C0; AU2020292766A1; EP3980272A1; CA3139793A1; EP3980272B1; GB2586576B; WO2020249601A1

Abstract

A security sheet 11 comprises a data sheet 15 for displaying data 16 and an attachment layer 17 for attaching the data sheet into a security document 10; the data sheet 15 comprises an outer surface, at least one transparent region 40 extending from the outer surface and a camouflage pattern 42; the attachment layer 17comprises a connection portion 60 at least partially embedded in the at least one transparent region 40; the camouflage pattern 42 at least partially overlaps the at least one transparent region 40 and connection portion 60. The camouflage pattern 42 is for interfering with the visibility of the connection portion 60 when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface.

Description

A SECURITY SHEET

Technical Field

The present invention is directed towards a security sheet for displaying data. The present invention is further directed towards a security document comprising such a security sheet and a method of manufacturing such security sheets and documents.

Background

Security documents and booklets, such as passports, passbooks, identification documents, certificates, licences, cheque books and the like, commonly comprise one or more security sheets on which information is provided. A passport booklet typically comprises a cover, a plurality of internal visa pages and at least one security sheet displaying the personal data of the passport holder. Typically the visa pages are made from paper and are sewn together along a stitch line coincident with the fold of the document. The security sheet may be formed from a plastic, typically polycarbonate, and during its manufacture a number of thin plastic layers are laid over one another and laminated together, thereby forming a thicker plastic body. As this plastic body is typically rigid and unable to bend without plastic deformation it is generally not attached at the stitch line or otherwise the booklet may not be able to bend effectively about the fold.

The plastic body may therefore be attached about the fold using a flexible hinge layer embedded in and extending from the plastic body. Usually steps are taken to ensure that the plastic body is resistant to delamination by forgers attempting to adapt the personal data. Furthermore, the attachments of the flexible hinge layer to the plastic body and about the stitch line need to be sufficiently durable and resistant to delamination to endure for the lifetime of the security booklet, which is often 10 years or more in the case of passports.

EP-B1-1592565 and EP-B2-1502765 disclose arrangements of flexible hinge layers in plastic bodies.

The plastic body typically comprises a transparent layer in which personal data and other security features are visible. As it is considered unattractive, the flexible layer is typically embedded within or under an opaque region in the plastic body such that it is not substantially visible in reflected light. However, as a result, if the plastic body has been replaced by a forger then any resulting damage to the flexible layer is not easily identifiable.

Summary

Objects of the present invention include further improving the ability to identify any tampering of the security sheet resulting in damage to the portion of the flexible layer located in the data sheet (referred to as the connection portion). A further object is to obscure the flexible layer from view without requiring its embedding in or under an opaque region of the plastic body. A further object is providing an improved security sheet with increased resistance to delamination by a forger and improved durability. A further object is to provide a strong and durable attachment between the security sheet and the rest of a security document. A further object is to provide a security sheet that is harder for a counterfeiter to replicate. Further objects include providing an improved method of manufacture of such a security sheet and a security document comprising such a security sheet.

The present invention therefore provides a security sheet, a security document and a method in accordance with the claims. Due to the camouflage pattern interfering with its visibility or appearance, the connection portion is not immediately visible to the naked eye and thus the aesthetics of the security sheet are improved. However, any damage to the connection portion resulting from tampering with the security sheet can still be identified by careful viewing with the naked eye through the camouflage pattern and at least one transparent region when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface.

In preferred embodiments the attachment layer comprises an attachment portion and the connection portion comprises connection wefts extending from the attachment portion. Such connection wefts may have a regular weft spatial repetition that, without the camouflage pattern, would otherwise be easily distinguishable to the naked eye through the transparent region. However, in alternative embodiments the connection portion may comprise a textile of interlaced wefts and warps, rather than only the connection wefts, such that the entire attachment layer is an interlaced textile. Alternatively, the connection wefts need not form part of a textile and instead may comprise strips, a film and/or other elongate bodies extending from the attachment portion, which may itself comprise a textile, solid film or the like.

In the present disclosure "interfere with the visibility of the connection portion" means that the camouflage pattern interferes with the ability of the naked eye to identify or distinguish the connection portion in the at least one transparent region. In particular, the camouflage pattern may: (a) cover at least part of the connection portion (preferably at least part of connection wefts of the connection portion) such that at least part of the connection portion is substantially hidden from view by the camouflage pattern when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface; and/or (b) confuse the naked eye by increasing the difficulty of distinguishing between at least part of the connection portion (preferably at least part of connection wefts of the connection portion) and the camouflage pattern, or directing the naked eye to the camouflage pattern rather than the connection portion, when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface.

The camouflage pattern preferably comprises at least one pattern element overlapping and covering at least part of the connection portion. The camouflage pattern may be discontinuous and at least one unmarked area (i.e. where pattern element(s) do not overlap transparent region(s)) is located adjacent to and between pattern elements and/or between the at least one pattern element and the edge of the data sheet. The connection portion may be at least partially visible, preferably upon close inspection only, in the at least one transparent region and/or through the camouflage pattern, such as between pattern elements in the unmarked area(s), when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface. Thus the camouflage pattern does not block the entire connection portion from view and is not a continuous opaque layer extending across and entirely hiding the connection portion.

The at least one pattern element may have the shape of a line, dot, circle, square, two-dimensional geometric shape (such as polygons, ellipses or circles) and/or a graphical design. Preferably the at least one pattern element has a substantially distinctive shape compared to the structure of the connection portion (e.g. the connection wefts) behind it such that the naked eye predominantly focuses upon and perceives the at least one pattern element rather than the connection portion. The at least one pattern element may therefore have a shape that conveys intelligible information to a reader. The at least one pattern element may have the shape of a symbol (e.g. a flag, national emblem or coat of arms), logo, graphical representation of an animal and/or plant (e.g. a flower or insect), pictogram, alphanumeric character, grapheme, personal data (e.g. name, photograph or serial number) or code. However, such an effect may also be achieved by the arrangement of pattern elements of the camouflage pattern forming a distinctive shape, such as in a fine line pattern (i.e. interlacing curved lines) or a Guilloche (i.e. a fine line pattern formable on a geometric lathe or the equivalent in a computer program).

The maximum width (i.e. the furthest distance between points of the pattern element) of at least one of, or all of, the or each pattern elements may be at least approximately 0.1 mm, approximately 0.5 mm, approximately 1 mm, approximately 3 mm and/or less than approximately 10 mm, approximately 8 mm, approximately 6 mm, approximately 4 mm or approximately 1 mm. The maximum widths of the unmarked areas between adjacent pattern elements may be in the range of approximately 0.01 mm to 4 mm. The at least one pattern element is preferably sufficiently wide and oriented to cover a substantial portion of the connection portion and the average width of the at least one pattern element is preferably at least the average width of each connection weft. In particular, each pattern element preferably extends across at least two connection wefts, more preferably at least five connection wefts and yet more preferably at least eight connection wefts. In the case of the at least one pattern element comprising at least one line, the line width is preferably in the range of approximately 0.05 mm to approximately 0.2 mm, more preferably in the range of 0.1 mm to 0.15 mm, and the average width of the unmarked areas between pattern elements is in the range of 0.15 mm to 0.25 mm.

Preferably the camouflage pattern comprises an array of pattern elements. In an array, the pattern elements may all have the same shape and/or sizes or may have a plurality of different shapes and/or sizes. In the latter embodiment the sizes and/or shapes of the pattern elements may vary stochastically across the array or regularly across the array. The orientation of the pattern elements may also vary across the array. The pattern elements of the array may have stochastic placement, with irregular element spatial repetition between adjacent pattern elements, or regular placement, with regular element spatial repetition or regular variances in element spatial repetition between adjacent pattern elements. The camouflage pattern may comprise pattern elements having a mixture of stochastic and regular placement. In the present disclosure the element spatial repetition of the camouflage pattern is considered the distance between centres of adjacent pattern elements. If such a measurement is not suitable (e.g. in the case of the pattern elements comprising interlaced lines), the element spatial repetition is the distance between corresponding repeating features of the camouflage pattern, such as where lines cross. The element spatial repetition of the camouflage pattern may be based upon (e.g. by being multiples of), optionally substantially the same as, dimensions of the structure of the connection portion in order to increase the confusion of the naked eye and reduce the visibility of the connection portion. Alternatively, depending upon the construction of the camouflage pattern, the element spatial repetition may be stochastic when compared to the dimensions of the structure of the connection portion and still reduce the visibility of the connection portion.

In a particularly preferred embodiment the connection portion comprises the connection wefts and the camouflage pattern comprises an array of pattern elements. The element spatial repetition may be based upon the widths of spacings between, and the weft spatial repetition of, the connection wefts, which assists in interfering with the visibility of the connections wefts. The element spatial repetition is preferably at least 50% or at least 75% of the width of the spacings and is preferably up to 125%, 150% or 200% of the width of the spacings. In addition, the average width of each of the pattern elements is preferably at least the average width of each connection wefts such that the pattern elements substantially cover the underlying connection wefts. The element spatial repetition is preferably constant across the camouflage pattern, particularly when the width of the spacings between connection wefts and weft spatial repetition is substantially the same across the connection portion. However, the element spatial repetition may vary in correspondence with a variation in the width of the spacings and weft spatial repetition.

The camouflage pattern area, which is the area defined within the outermost boundaries of the pattern element(s), may extend across at least part of the width, preferably the entire width, of the data sheet and connection portion. The camouflage pattern may extend from an inner edge of the data sheet and may cover at least part of, and preferably all of, the length of the connection portion in the data sheet. The camouflage pattern area may extend over at least approximately 25%, at least approximately 50%, at least approximately 75% or all of the connection portion area, which is the area defined by the outer boundaries of the connection portion. The camouflage pattern may extend over less than approximately 95%, less than approximately 75% or less than approximately 50 % of the connection portion area.

The area covered by the pattern element(s) may extend over at least approximately 25%, at least approximately 50%, at least approximately 75%, at least approximately 90% or all of the camouflage pattern area and/or may extend over less than approximately 95%, less than approximately 75% or less than approximately 50 % of the camouflage pattern area. In a particular embodiment the camouflage pattern comprises a continuous, single, pattern element (i.e. with an area of 100% of the camouflage pattern area), which is preferably matter by having a higher surface roughness than the outer surface beyond the camouflage pattern.

In order to cover the connection portion, at least one pattern element of the camouflage pattern may overlie at least part of the connection portion and have a lower opacity and/or exhibit less specular reflection than the non-camouflaged region of the outer surface, which is the area of the outer surface outside of the camouflage pattern. The contrast (e.g. differences in transparency, refractive index, level of gloss, lightness, hue and/or saturation) perceived by the human eye between the camouflage pattern and connection portion may be less than the contrast between the rest of the transparent region and the connection portion. The connection portion may be substantially transparent or translucent and may be substantially clear or colourless. The connection portion may appear to have a substantially similar visible colour to that of the camouflage pattern. In the present disclosure, the term "visible colour" means a colour which can be seen by the naked human eye under reflected visible light. In the present disclosure "visible light" refers to light having a wavelength within the visible spectrum, which is approximately 400 to 750nm. It is most preferable that the visible light is white light, i.e. contains substantially all the visible wavelengths in more or less even proportion. The term colour includes achromatic hues such as black, grey, white, silver etc., as well as chromatics such as red, blue, yellow, green, brown etc. "Similar visible colours" may also be referred to as the "same visible colours" and are those which do not present a clear contrast to one another that is visible to the naked human eye in reflected light even without a close inspection. For example, in preferred embodiments, two visible colours will be considered substantially similar or the same if the Euclidean distance 4Eab between them in CIELAB colour space (i.e. the CIE 1976 L"a"b" colour space) is less than 5, more and preferably less than 3. The value of LiE",-,b is measured using the formula: AE:, = AIR4L")2 + (Act02 + (Ab')21 Where 4L', 4a. and ib" are the distance between the two colours along the L", a* and b* axes respectively (see "Digital Color Imaging Handbook" (1.7.2 ed.) by G. Sharma (2003), CRC Press, ISBN 0-8493-0900-X, pages 30 to 32). The colour difference 4E:th can be measured using any commercial spectrophotometer, such as those available from Hunterlab of Reston, Virginia, USA.

Preferably at least part of the camouflage pattern comprises a matt camouflage region. In particular, the matt camouflage region exhibits less gloss, or less specular reflection (and/or more diffuse reflection) of visible light incident upon it, than at least the majority of the non-camouflaged region of the outer surface. The matt camouflage region may still be partially transparent, but substantially reduces the visibility of and hides the connection portion below it. The matt camouflage region may be formed, for example, from at least one matt pattern element comprising a continuous matt surface or from interference effects from arrays of pattern elements (e.g. fine line patterns). The matt camouflage region and/or at least one matt pattern element may exhibit less specular gloss than at least the majority of the non-camouflaged region of the outer surface as measured under the standard ASTM D523-14(2018), Standard Test Method for Specular Gloss. The result is that the matt camouflage region and/or at least one pattern element is clearly visible as a matt area in an otherwise glossy outer surface. Such matt areas have been found to be particularly effective in interfering with the visibility of the connection wefts.

In addition or alternatively, at least part of the camouflage pattern comprises a gloss camouflage region, which has a similar gloss to at least the majority of the non-camouflaged region of the outer surface. For example, at least one gloss pattern element may have a substantially gloss continuous surface, which may result in the connection portion being visible through the at least one gloss pattern element upon close inspection. In particular preferred embodiments at least one pattern element comprises a matt pattern region and at least one unmarked area comprises a gloss pattern region, which may result in the overall appearance of the camouflage pattern being matt or less glossy compared to the non-camouflaged region. Particularly preferable camouflage effects can be achieved by having matt or gloss pattern elements within other gloss or matt pattern elements respectively.

In preferred embodiments the camouflage pattern comprises embossing(s) in the outer surface and the embossing may matt and/or gloss camouflaged regions. The embossing(s) may comprise a relief structure, which may be carved, moulded, stamped, engraved or otherwise formed in the data sheet. The relief structure may be a variation in thickness of the data sheet, particularly a variation in height at the outer surface, relative to the thickness of the data sheet outside of the camouflage pattern. The variation in thickness may be at least 0.001 mm, more preferably at least 0.015 mm, and may be up to 0.04 mm, more preferably 0.025 mm. Such a relief structure reduces the visibility of the connection portion due to optical effects, particular, refraction and reflection, at the edges of the pattern element(s). Furthermore, in an embossing matt pattern element(s) may be formed by embossing area(s) of pattern element(s) to have a higher surface roughness compared to the outer surface of the data sheet outside of the camouflage pattern. Gloss pattern element(s) may be formed by ensuring that the surface roughness of such areas is substantially the same as that of the outer surface of the data sheet outside of the camouflage pattern. Particularly preferable camouflage effects can be achieved by having pattern elements within other pattern elements, each of different heights compared to the outer surface outside of the camouflage pattern.

The camouflage pattern may be formed by at least partially by the application of printed ink, by laser marking, by laser ablation, by chemical etching and/or by any other suitable means. In the case of printed ink the at least one pattern element may be opaque, but the unmarked areas between pattern elements is transparent such that the entire camouflage pattern is not opaque. In a particular example the camouflage pattern comprises pattern elements formed by at least two of embossing, printing, laser marking, laser ablation, chemical etching and the like.

The camouflage pattern can either be a stand-alone discreet design on the data page or a design integrated with additional patterns on the data page. The camouflage pattern may form part of an embossing or print extending around the periphery of the data page to frame or provide a border to the data contained thereon. The camouflage pattern may extend across the data page beyond the boundaries of the connection portion and may occupy at least 50% of the area of the outer surface of the data page.

The distal pattern edge of the camouflage pattern, which is the edge of the camouflage pattern furthest from an inner edge of the data page, may be irregular rather than straight. The connection portion, and preferably the connection wefts thereof, may extend beyond the distal pattern edge of the camouflage pattern such that they are partially visible in the data page. By virtue of the distal pattern edge having an irregular shape, such as by comprising a sinusoid, curve(s) and/or plurality of straight lines, the visible ends of the connection portion are camouflaged since the naked eye may have difficulty in immediately distinguishing between the connection portion and distal pattern edge of the camouflage pattern.

The data sheet may comprise at least one opaque region and the at least one transparent region and the connection portion may extend at least partially over the at least one opaque region. The data sheet may be formed from at least a plurality of body layers and the connection portion may be attached between two adjacent body layers. The at least one transparent region may be formed from at least one transparent body layer and the at least one opaque region may be formed from at least one opaque body layer. The connection portion may be attached at or adjacent to the outer surface of the data sheet. At least one strip may be located over at least a portion of the connection portion and attached to the data sheet. The camouflage pattern may extending at least partially over the at least one strip and at least part of the connection portion not overlapping the at least one strip. In particular, the at least part of the connection portion not overlapping the at least one strip may not be embedded particularly far into the at least one transparent region as there is no strip overlying it and, as a result, may be more visible when the outer surface is viewed without a camouflage pattern. By applying the camouflage pattern over it the at least part of the connection portion not overlapping the at least one strip is more difficult to identify by the naked eye. If the camouflage pattern is embossed then preferably the depth of the embossing is selected so as to hide any discontinuities left at the outer surface by the portions of the connection wefts not covered by the strip. In particular, the depth of the embossing may be at least the depth from the outer surface to the connection wefts.

The present invention further provides a security sheet comprising: a data sheet for displaying data comprising an outer surface, at least one transparent region extending from the outer surface and a patterned region; and an attachment layer for attaching the data sheet into a security document and comprising a connection portion at least partially embedded in the at least one transparent region, wherein the patterned region at least partially overlaps the at least one transparent region and connection portion. The patterned region may be a camouflage pattern and the patterned region may interfere with the appearance of the connection portion when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface.

Brief Description of the Drawings

By way of example only, embodiments of a security sheet, a security document and a method of manufacture in accordance with the present invention are now described with reference to, and as shown in, the accompanying drawings, in which: Figure 1 is a perspective view of a security document, particularly a passport, according to the present invention in an open configuration; Figure 2 is a schematic cross-sectional side elevation of a fold area of the security document of Figure 1 in an exploded configuration; -10 -Figure 3 is a schematic plan view of an embodiment of a security sheet according to the present invention; Figure 4 is a schematic plan view of the security sheet of Figure 3 with a camouflage pattern hidden from view; Figures 5A is a cross-sectional side elevation of an embodiment of a laminar structure for forming the security sheet of Figure 3; Figures 5B is a cross-sectional side elevation of the security sheet of Figure 3; Figure 6A is a schematic plan view of a camouflage pattern of the security sheet of Figure 3; and Figures 6B to 6D are schematic plan views of alternative camouflage patterns for the security sheet of Figure 3.

Detailed Description

Figures 1 and 2 illustrate a security document 10 in accordance with the present invention. The security document 10 may be of any suitable type, but may comprise a security booklet, such as a passport as illustrated, a passbook, an identification document, a certificate, a licence, a cheque book or the like. The security document 10 comprises a security sheet 11, in this case a data page, foldable about and preferably attached along a fold 12 to a plurality of leaves 13. The plurality of leaves 13 may comprise a fibrous substrate, for example paper and/or cotton and may form visa pages. The security document 10 also comprises a cover 14, which is foldable about and attached to the fold 12 and/or is adhered to an outer leaf (not shown) located on the outside of the leaves 13 and security sheet 11. The attachment is preferably stitching through the security sheet 11, leaves 13 and/or cover 14 at the fold 12, although other attachment means such as adhesion may be used and the attachment means may be offset from the fold 12.

The security sheet 11 is illustrated in further detail in Figures 3 to 5B. The security sheet 11 comprises a data sheet 15, which preferably comprises plastic, comprising data 16 and an attachment layer 17 attached to the data sheet 15. The data sheet 15 extends across a width from an inner edge 22, located proximate the fold 12, to an outer edge 23, distal to the fold 12. The data sheet 15 extends across a thickness between substantially planar first and second outer surfaces 28, 29. The data sheet 15 may comprise at least one of a thermoplastic polymer, polycarbonate, polybutylene terephthalate, polyester, polyethylene, polypropylene, polyvinyl chloride, a co-polymer comprised of any of the previous thermoplastic polymers, a fibrous substrate and the like. The thickness of the data sheet 15 may be at least approximately 150 pm and may be between approximately 300 pm and approximately 1000 pm thick. The data 16 may comprise personal or variable data 20, which specifically relates to the holder of the security sheet 11 and is different between a plurality of security documents 10, and fixed or non-variable data 21, which is typically the same across a plurality of security documents 10 and security sheets 11. The data 16 may comprise, for example, printed ink, laser marking or laser ablation. The data 16 may at least partially overlap the attachment layer 17.

The attachment layer 17 comprises a connection portion 60 extending from an attachment portion 26. The attachment layer 17 may comprise a substantially elongate sheet or body as illustrated. The connection portion 60 at least partially extends across the data sheet 15 and is at least partially located in or on and attached to the data sheet 15 such that the attachment layer 17 extends from the inner edge 22 of the data sheet 15. The attachment portion 26 is located at least partially, preferably entirely, outside of the data sheet 15 and is attached in the security document 10 along the fold 12 or otherwise as discussed above. The attachment portion 26 is preferably flexible, substantially resistant to plastic deformation and tear resistant.

The attachment layer 17 may at least partially comprise a textile comprising interlaced or overlapping wefts 30 and warps 31 and the textile may be knitted or woven.

The warps 31 may extend substantially parallel to one another, the fold 12 and/or the inner edge 22 of the data sheet 15. The wefts 30 may extend substantially parallel to one another and/or may be substantially perpendicular to the warps 31, inner edge 22 of the data sheet 15 and/or the fold 12. The textile comprises yarns forming the wefts 30 and warps 31. The yarns are long, thin strand of materials for forming the textile by weaving, knitting, sewing or another interlacing method. For example, the yarns may comprise at least one of cotton, polyamide, polyester, viscose, glass, polypropylene, polyaramid, polyurethane, nylon, bonded nylon, polycotton and/or other suitable fibres. Each yarn may have a diameter in the range of from approximately 26 microns up to approximately 300 microns.

At least the attachment portion 26 comprises interlaced or overlapping wefts 30 and warps 31 and may be a knitted or woven textile. The connection portion 60 may comprise at least portions of wefts 30 of the textile, referred to as connection wefts 25. Each connection weft 25 may not be connected to another connection weft 25 outside of the attachment portion 26. The connection wefts 25 may comprise portions of the wefts 30 extending out of and forming the textile of the attachment portion 26 as shown in Figures 3 -12 -and 4 (Figure 4 is the same as Figure 3 except a camouflage pattern 42, discussed in further detail below, is hidden from view to improve the clarity of the structure of the connection wefts 25). The connection wefts 25 may extend at least partially across the attachment portion 26 and, as in Figures 3 and 4, may extend entirely across the attachment portion 26. Alternatively, the connection wefts 25 may be attached to a distal warp 63, which is the warp 31 of the attachment portion 26 distal to the fold 12, such that they substantially do not extend into or form the attachment portion 26 and comprise different wefts 30 to those of the attachment portion 26. There may be fewer connection wefts 25 than wefts 30 of the attachment portion 26 in number and/or per unit area (preferably per unit area on average) as in Figures 3 and 4.

The connection portion 60 is therefore firmly connected to the at least one body layer 18 by a frictional force applying a resistance to the attempted removal of the attachment layer 17 from the data sheet 15. The connection portion 60 and connection wefts 25 may be connected to the data sheet 15 only by friction and, for example, not by a mechanical, fusing, chemical or other locking mechanism. Due to the connection wefts 25 the contact surface area between the connection portion 60 and data sheet 15 is relatively large to improve the strength of the connection. Therefore, as shown in Figures 3 and 4, preferably the plurality of connection wefts 25 are separated from an adjacent connection weft 25 by a spacing 27. The at least one spacing 27 may have a width in the range of from approximately 18 microns up to approximately 500 microns. The weft spatial repetition, which is the average distance between the centre of adjacent connection wefts 25, is in the range of approximately 100 microns to approximately 1000 microns, more preferably approximately 300 microns to approximately 900 microns and yet more preferably approximately 600 microns to approximately 800 microns. The size of the at least one spacing 27 is selected to enable a suitably large volume of material of the data sheet 15 to flow, bond and/or fuse between the connection wefts 25 to provide resistance to delamination of the data sheet 15. The average width of at least one spacing 27 may be at least or greater than the average width of the connection wefts 25 adjacent to the at least one spacing 27. The width of the spacings 27 may also vary across the attachment layer 17. The attachment layer 17 preferably comprises at least five connection wefts 25, more preferably at least ten connection wefts 25, more preferably at least twenty connection wefts 25 and, yet more preferably, at least fifty connection wefts 25.

The security sheet 11 may be formed by the attachment together of the attachment layer 17 and at least one body layer 18 forming the data sheet 15. The connection of the at -13 -least one body layer 18 and attachment layer 17 may be by lamination, adhesion, welding and/or any other suitable method. The security sheet 11 may be formed by the lamination, adhesion or welding together of a laminar structure 19, an embodiment of which is illustrated in Figure 5A, comprising a plurality of body layers 18 and the attachment layer 17. During lamination or welding heat and/or pressure are applied to fuse or push the plurality of body layers 18 together and at least one body layer 18 is pushed through the at least one spacing 27 between the connection wefts 25. The lamination may be performed using any suitable method and may be a substantially in-line method, similar to that of WO-A-2017/060684 and WO-A-2017/060688, in which a plurality of security sheets 11 are formed continuously.

The connection portion 60, particularly the connection wefts 25, are at least partially embedded in the data sheet 15 and at least one body layer 18. Figures 5A and 5B illustrate a preferred embodiment in which the connection portion 60 is at least partially located on the first outer surface 28 of the at least one body layer 18 of the laminar structure 19 prior to lamination. During lamination at least part of the connection portion 60, particularly the connection wefts 25, is pressed into the first outer surface 28 of the at least one body layer 18. After lamination the connection portion 60 is at least partially attached at or adjacent to and overlapping the first outer surface 28 of the data sheet 15. Alternatively, before or after attachment of the plurality of body layers 18 to one another (for example by lamination, welding or adhesion), the connection portion 60 may be welded into or adhered to the first outer surface 28. In each method the material of the at least one body layer 18 flows or is pressed through the at least one spacing 27 to form the connection. The lamination or welding preferably presses the connection wefts 25 into the first outer surface 28 sufficiently deeply that substantially all of the connection wefts 25 are not exposed and are covered by the material of the at least one body layer 18.

As shown in Figures 3, 4 and 5A, at least one strip 50 may overlap at least part of the connection portion 60 and attached to or embedded within the data sheet 15 such that it forms part of the first outer surface 28 of the data sheet 15. The at least one strip 50 may only overlap the data sheet 15 over at least part of the connection portion 60. The at least one strip 50 assists in further securing the connection wefts 25 in the data sheet 15. The at least one strip 50 may extend across a portion of all of the connection wefts 25 as shown or may extend over a portion of less than all of the connection wefts 25. The at least one strip 50 may be located on the connection portion 60 prior to lamination and laminated together with the connection portion 60 and at least one body layer 18. Thus at least part of the -14 -connection wefts 25 may be attached between the at least one strip 50 and at least one body layer 18. The at least one strip 50 may sink into the at least one body layer 18 and around the connection wefts 25 such that it is substantially indistinguishable from the at least one body layer 18 as illustrated in Figure 5B. Alternatively, the connection wefts 25 and at least one body layer 18 are laminated together and the at least on strip 50 subsequently applied over at least a portion of the connection wefts 25 and attached in a further step.

The data sheet 15 comprises at least one transparent region 40 extending from the first outer surface 28 into the thickness of the data sheet 15. The at least one transparent region 40 may result from at least a portion of the at least one body layer 18, particularly the body layer 18 forming the first outer surface 28, and, if present, the at least one strip 50, being transparent. For example, as in Figures 3 to 5A, at least the body layer 18 forming the first outer surface 28 and the strip 50 are transparent. The connection portion 60 is at least partially embedded in the at least one transparent region 40 and the at least one transparent region 40 may extend over at least the connection portion 60. The data sheet 15 may comprise at least one opaque region 41, formed for example by at least one of the inner body layers 18 in Figure 5A being opaque, extending at least partially between the first and second outer surfaces 28, 29. The at least one transparent region 40 and connection portion 60 at least partially extend over the at least one opaque region 41 and the connection portion 60 is at least partially located between the first outer surface 28 and the at least one opaque region 41. The at least one transparent region 40 and/or at least one opaque region 41 may be referred to as at least one transparent layer and/or at least one opaque layer respectively. The at least one opaque region 41 may not be present and/or may comprise at least one transparent window therethrough such that the connection portion 60 is at least partially visible from the second outer surface 29.

The data sheet 15 comprises a camouflage pattern 42 at least partially overlapping the at least one transparent region 40 and connection portion 60, as shown in Figures 3 and 5B. The camouflage pattern 42 at least partially interferes with the visibility of the connection portion 60 when the first outer surface 28 is viewed by the naked eye in reflected visible light incident upon the first outer surface 28. Figure 6A illustrates the camouflage pattern 42 of Figure 3 alone. The camouflage pattern 42 is located at and overlies the first outer surface 28 and comprises a plurality of pattern elements 44 overlapping the connection portion 60, particularly connection wefts 25 thereof. The connection portion 60 is visible through unmarked areas 45 between the pattern elements -15 - 44. As shown in Figure 3, the camouflage pattern 42 may extend across the entire width of the data sheet 15, entirely along the data sheet 15 parallel to the fold 12 and over all of the connection wefts 25. The camouflage pattern 42 may extend from the inner edge 22 of the data sheet 15 and covers part of the length of the connection portion 60 (i.e. the direction perpendicular to the fold 12) in the data sheet 15. Thus the camouflage pattern 42 overlaps the strip 50 and may overlap at least part of, preferably all of, the region of the connection portion 60 that does not overlap the strip 50.

In Figure 3 a camouflage pattern area is defined by the area within the boundaries of the camouflage pattern 42 (i.e. bounded on three sides by the edge of the data sheet 15 and by a distal pattern edge 47, which is the edge of the camouflage pattern 42 further from the inner edge 22 of the data sheet 15). A connection portion area is the area defined by the connection wefts 25 and the spacings 27 between them, including the spacings 27 between the connection wefts 25 and edges of the data sheet 15 parallel to the connection wefts 25. The camouflage pattern area overlies over 75% of the connection portion area.

In Figure 6A the camouflage pattern 42 comprises a Guilloche 70 formed from pattern elements 44 comprising an array of lines 72. Areas between certain lines 72 form further pattern elements 44 by comprising substantially continuous areas of colour in the shape of polygons or rhombuses 71, which form a repeating geometric pattern. The width of the lines 72 is in the range of 0.1 mm to 0.15 mm, which is particularly effective if the weft spatial repetition is in the range of approximately 0.3 mm to approximately 0.9 mm (more preferably 0.6 mm to 0.8 mm). The maximum widths of the rhombuses 71 is in the range of approximately 1 mm to 3 mm. The element spatial repetition 46 between adjacent pattern elements 44 is illustrated in Figure 6A as the distance between the crossover points of the lines 72 or the distance between the centres of the rhombuses 71. The element spatial repetition 46 is constant across the camouflage pattern 42 and in this embodiment the width of the spacings 27 and weft spatial repetition is substantially the same across the connection portion 60. The element spatial repetition 46 is not the same as the weft spatial repetition, but due to the coverage of the pattern elements 44 and their repeating nature this difference assists in interfering with the appearance of the connections wefts 25. In addition, the average width of the rhombuses 71 is greater than the average width of each connection wefts 25 such that the rhombuses 71 substantially cover portions of the underlying connection wefts 25.

-16 -In the embodiment of Figures 3, and 5B and 6A the camouflage pattern 42 comprises a mixture of matt and gloss camouflage regions. The matt camouflage regions have a lower gloss than the area of the first outer surface 28 outside of the camouflage pattern 42, which is referred to as the non-camouflaged region 78. The gloss camouflage regions having a similar gloss to the non-camouflaged region 78. In particular, matt camouflage regions may be formed due to the pattern elements 44 forming the rhombuses 71 being matt. The camouflage pattern 42 is formed by an embossing in the first outer surface 28. The embossing may be formed during the process of attaching together the at least one body layer 18, attachment layer 17 and, if present, strip 50. In particular, the embossing may be formed during a lamination process in which an embossed plate is applied to the first and/or second outer surface 28, 29 of the at least one body layer 18 and, if present, strip 50. The embossed plate may be applied under heat and pressure such that the at least one body layer 18 and, if present, strip 50 at least partially soften to enable the relief structure to form about a corresponding relief structure or mould of the embossed plate. The areas of the plate corresponding to the matt pattern elements 44 of the rhombuses 71 have a higher surface roughness than the areas corresponding to the unmarked areas 45 in order to form the matt surfaces. Such a high surface roughness may be achieved by forming a series of small, closely spaced dots (e.g. which are only identifiable under x10 magnification). The combination of the matt camouflage regions resulting from the embossing and the gloss camouflage regions resulting from the unmarked areas 45 (between the rhombuses 71 the lines 72) has been found to be particularly effective in disrupting the visibility of the connection wefts 25. It will be appreciated that the definition of the matt and gloss camouflage regions depends upon the area of the camouflage pattern 42 considered. For example, the entire area of the camouflage pattern 42 of Figure 3 is overall a matt camouflage region because of the effects of the lines 72 and rhombuses 71. However, the rhombuses 71 themselves are matt camouflage regions and the unmarked areas 45 are gloss camouflage regions.

The distal pattern edge 47 in Figure 3 and 6A is sinusoidal (i.e. irregular) and does not extend sufficiently far across the data sheet 15 such that the connection wefts 25 as visible beyond the distal pattern edge 47. The sinusoidal distal pattern edge 47 edge increases the difficulty of distinguishing these visible portions of the connection wefts 25.

Figures 6B to 6D illustrate further embodiments of suitable camouflage patterns 42 and are applied in a similar manner to the embodiment of Figures 3 to 6A unless otherwise stated. In Figure 6B the camouflage pattern 42 comprises pattern elements 44 in the shape -17 -of lines together forming a fine line pattern. The lines are preferably embossed into the data sheet 15. The fine line pattern, by virtue of the arrangement of the lines, form distinctive shapes in the forms of stars. The naked eye is drawn to the stars and the fine line pattern regularly covers parts of the connection wefts 25 such that their visibility is reduced. In addition, optical effects at the lines interferes with the ability for the human eye to distinguish the underlying connection wefts 25 such that the entire camouflage pattern 42 forms a matt region. The width of the lines 72 is in the range of 0.1 mm to 0.15 mm, which is particularly effective if the weft spatial repetition is in the range of approximately 0.3 mm to approximately 0.9 mm (more preferably 0.6 mm to 0.8 mm). The average width of the unmarked areas 45 is in the range of 0.15 mm to 0.25 mm, although a lower spacing 27 would be preferable in order to increase the area of the connection wefts 25 covered by the pattern elements 44. The distal pattern edge 47 is irregular and comprises a plurality of straight lines.

In Figures 6C and 6D the camouflage pattern 42 comprises pattern elements 44 graphically representation of animals (dragonflies 73 and fish 74) and plants (flowers 75) that draw the naked eye away from the underlying connection wefts 25. The pattern elements 44 are sized and oriented to extend across a plurality of connection wefts 25. In a preferred embodiment in which the weft spatial repetition is in the range of approximately 0.3 mm to approximately 0.9 mm (more preferably 0.6 mm to 0.8 mm), the maximum width of each dragonfly is in the range of approximately 3.5 mm to approximately 5.5 mm (extending across up to nine connection wefts 25), the maximum width of each fish 74 is in the range of approximately 4 mm to approximately 6 mm (extending across up to ten connection wefts 25) and the maximum width of each flower 75 is in the range of 1 mm to 2 mm (extending across up to four connection wefts 25). The element spatial repetition 46 is irregular, due to the width of the unmarked areas 45 varying across the camouflage pattern 42, such that the visibility of the regular weft spatial repetition is disrupted by the irregular element spatial repetition 46. For example, the maximum widths of the unmarked areas 45 between adjacent pattern elements 44 may be in the range of approximately 0.01 mm to 4 mm. In Figures 6C and 6D the distal pattern edge 47 is discontinuous and irregular and may be defined by a plurality lines drawn between the outermost points of the pattern elements 44.

In Figure 6C the pattern elements 44 have gloss surfaces within their perimeters that are of a similar gloss to the non-camouflaged region 78. Thus the connection wefts 25 may be visible through the pattern elements 44, but their visibility is reduced by virtue of -18 -optical effects at the lines defining the perimeters of the pattern elements 44. The pattern elements 44 are preferably embossed into the data sheet 15 in a similar manner to the embodiment of Figures 3 to 6A. For example, in the relief structure the areas of the plate corresponding to the gloss surfaces within the lines defining the perimeters of the pattern elements 44 have a similar low surface roughness to the areas corresponding to the unmarked areas 45 and the non-camouflaged region 78.

In Figure 6D some of the pattern elements 44, particularly those forming the animals 73, 74, comprise matt surfaces in a similar manner to the embodiment of Figures 3 to 6A. The rest of the pattern elements 44 comprise gloss surfaces in a similar manner to the embodiment of Figure 6C. This combination of matt and gloss pattern elements 44 has been found to be particularly effective in disrupting the visibility of the connection wefts 25.

The camouflage patterns 42 of Figures 6A to 6D exhibit different gloss to that of the non-camouflaged region 78. For example, the non-camouflaged region 78 may have an average gloss in the range of approximately 90 to 100 gloss units when measured in an aperture of 4.5 mm diameter at a measurement angle of 60° using a Novo-Curve Glossmeter available from Rhopoint Instruments Limited in the United Kingdom, which measures the gloss according to ASTM D523 and ISO 2813. Under the same conditions the average gloss value of the camouflage patterns 42 is in the range of approximately 60 to 85 gloss units. Thus the difference in gloss values is in the range of approximately to 5 to 40 gloss units, which results in a relatively low contrast between the camouflage pattern 42 and the non-camouflaged region 78.

Various alternatives to the embodiments discussed above fall within the scope of the present invention. The data sheet 15 may comprise a plurality of camouflage patterns 42. The camouflage patterns 42 may be below the first outer surface 28, such as by being located on one of the body layers 18 prior to lamination. Furthermore, the references above to features being at, adjacent to or on the first outer surface 28 are merely for nomenclature purposes and instead the features may be at the second outer surface 29. Furthermore, the connection wefts 25, strip 50 and at least one transparent region 40 may be partially located on both of the first and second outer surfaces 28, 29.

The connection portion 60 may comprise a different material to the surrounding material of the data sheet 15 such that a discrete boundary or frictional contact surface is formed between them. The connection portion 60 may thus comprise a material of a higher -19 -melting point to that of adjacent body layers 18 and, during lamination or welding, the connection portion 60 does not melt or fuse to the body layers 18. However, alternatively or in addition, the connection portion 60 may be at least partially bonded to the data sheet 15 by fusing, adhesion and/or the like with the body layers 18 to further improve the strength of the connection.

Rather than the connection portion 60 being attached at the first and/or second outer surface 28, 29 of at least one body layer 18 it may be attached between adjacent body layers 18. In the laminar structure 19 the connection portion 60 may be at least partially located between two adjacent body layers 18 prior to lamination or other attachment. The adjacent body layers 18 are attached or fused to one another to form the data sheet 15 and the connection portion 60 is located substantially within the data sheet 15. During lamination or welding the material of the two adjacent body layers 18 between which the connection portion 60 is located flows or is pressed through the at least one spacing 27. As a result, material of the data sheet 15 at least partially fills at least one spacing 27 between at least two adjacent connection wefts 25, which are therefore embedded in the data sheet 15. Preferably every spacing 27 between adjacent connection wefts 25 is filled with material of the data sheet 15 to ensure a strong connection.

Claims

-20 -CLAIMS: 1. A security sheet comprising: a data sheet for displaying data comprising an outer surface, at least one transparent region extending from the outer surface and a camouflage pattern; and an attachment layer for attaching the data sheet into a security document and comprising a connection portion at least partially embedded in the at least one transparent region, wherein the camouflage pattern at least partially overlaps the at least one transparent region and connection portion and the patterned region is for interfering with the visibility of the connection portion when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface.
2. A security sheet as claimed in claim 1 wherein the connection portion is at least partially visible through the camouflage pattern when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface.
3. A security sheet as claimed in any one of the preceding claims wherein the camouflage pattern extends over at least 25% of the connection portion.
4. A security sheet as claimed in any one of the preceding claims wherein the camouflage pattern overlaps the at least one transparent region by overlying the outer surface or being at least partially embedded in the at least one transparent region.
5. A security sheet as claimed in any one of the preceding claims wherein the camouflage pattern comprises at least one pattern element overlapping the connection portion.
6. A security sheet as claimed in claim 5 wherein the area of the at least one pattern element occupies at least 25% of the area of the camouflage pattern.
7. A security sheet as claimed in claim 5 or claim 6 wherein at least one pattern element has a shape that conveys intelligible information to a reader.
8. A security sheet as claimed in any one of claims 5 to 7 wherein the at least one pattern element comprises a line, dot, circle, square, two-dimensional geometric shape, a graphical design, a symbol, logo, graphical representation of an animal and/or plant, pictogram, alphanumeric character, grapheme, personal data and/or code.
-21 - 9. A security sheet as claimed in any one of claims 5 to 8 wherein the camouflage pattern comprises an array of pattern elements having stochastic and/or regular placement.
10. A security sheet as claimed in claim 9 wherein the pattern elements have the same shape and/or sizes or a plurality of different shapes and/or sizes.
11. A security sheet as claimed in claim 9 or claim 10 wherein an element spatial repetition of the pattern elements is based upon dimensions of the structure of the connection portion.
12. A security sheet as claimed in any one of the preceding claims wherein the attachment layer comprises an attachment portion and the connection portion comprises connection wefts extending from the attachment portion.
13. A security sheet as claimed in claims 11 and 12 wherein a repetition spacing between adjacent pattern elements is in the range of 50% to 150% of the distance between adjacent connection wefts overlapping the adjacent pattern elements.
14. A security sheet as claimed in claim 9 or claim 10 wherein the average width of the at least one pattern element is preferably at least the average width of each connection weft.
15. A security sheet as claimed in any one of the preceding claims wherein the camouflage pattern comprises at least one matt camouflage region that exhibits less gloss than at least the majority of the area of the outer surface outside of the camouflage pattern.
16. A security sheet as claimed in any one of the preceding claims wherein the camouflage pattern comprises at least one gloss camouflage region that exhibits similar gloss to at least the majority of the area of the outer surface outside of the camouflage pattern.
17. A security sheet as claimed in claims 15 and 16 wherein the camouflage pattern comprises at least one pattern element forming the at least one matt camouflage region and at least one pattern element, and/or at least one unmarked area between adjacent pattern elements, forming the at least one gloss camouflage region.
-22 - 17. A security sheet as claimed in any one of the preceding claims wherein the contrast perceived by the human eye between the camouflage pattern and connection portion is less than the contrast between the transparent region and the connection portion and/or wherein the camouflage pattern and connection portion have substantially the same visible colour.
19. A security sheet as claimed in any one of the preceding claims wherein the camouflage pattern comprises an embossing in the outer surface, print, laser marking, laser ablation and/or chemical etching.
20. A security sheet as claimed in any one of the preceding claims wherein the camouflage pattern comprises distal pattern edge, which is the edge of the camouflage pattern furthest from an inner edge of the data page, and the distal pattern edge is irregular.
21. A security sheet as claimed in any one of the preceding claims comprising at least one opaque region overlapping the at least one transparent region, wherein the connection portion is located in or adjacent to at least one transparent region between the at least one opaque region and the outer surface.
22. A security document comprising the security sheet of any one of the preceding claims and at least one further leaf attached to the attachment layer.
23. A method of forming a security sheet comprising: locating an attachment layer to overlap at least one body layer, wherein: the at least one body layer comprises an outer surface and at least one transparent region extending from the outer surface; and the attachment layer is for attaching the security sheet into a security document and comprises a connection portion; attaching the connection portion to the at least one body layer such that the connection portion is at least partially embedded in the at least one transparent region and the at least one body layer forms a data sheet for displaying data; and applying a camouflage pattern to the data sheet to at least partially overlap the at least one transparent region and connection portion, wherein the patterned region is for interfering with the visibility of the connection portion when the outer surface is viewed by the naked eye in reflected visible light incident upon the outer surface.
-23 - 24. A method as claimed in claim 23 wherein applying the camouflage pattern comprises forming an embossing in the outer surface, applying a print to the at least one body layer and/or laser marking, laser ablating and/or chemically etching the at least one body layer and/or data sheet.
25. A method as claimed in claim 23 or claim 24 further comprising: at least partially locating the connection portion between adjacent body layers of the at least one body layer and attaching the adjacent body layers to one another through the connection portion; and/or locating the connection portion to at least partially overlie the outer surface and attaching the connection portion into the outer surface.
26. A method as claimed in any one of claims 23 to 25 comprising: locating the connection portion to at least partially overlie the outer surface; attaching the connection portion into the outer surface; locating at least one strip over at least a portion of the connection portion and outer surface; and attaching the at least one strip to the outer surface.