WO2019058091A1

WO2019058091A1 - A method of manufacturing a security sheet

Info

Publication number: WO2019058091A1
Application number: PCT/GB2018/052116
Authority: WO
Inventors: Simon Quainton; Baljeet DHILLON
Original assignee: De La Rue International Limited
Priority date: 2017-09-21
Filing date: 2018-07-27
Publication date: 2019-03-28
Also published as: EP3684628A1; GB201715249D0; GB2566706B; GB2566706A

Abstract

The present invention provides a method of manufacturing a security sheet (10) including laser marking and a security sheet (10) marked by a laser.The security sheet (10) comprises a plastic substrate (11) having opposing first and second outer surfaces (12, 13), at least one mask (25) at least partially embedded in or located on the plastic substrate (11) and a laser markable region (30) located between the second outer surface (13) and the at least one mask(25). The method comprises directing a laser from the first outer surface(12) onto at least part of the at least one mask(25), which blocks the laser from the laser markable region(30),and adjacent to the at least one mask (25) and to the laser markable region(30). Therefore at least one mark (31) aligned with the at least one mask (25) is formed in the laser markable region(30).

Description

A METHOD OF MANUFACTURING A SECURITY SHEET

Technical Field

The present invention is directed towards a method of manufacturing a security sheet including laser marking and a security sheet marked by a laser.

Background

Security documents commonly comprise one or more security sheets on which information is provided. Exemplary security documents include cards, such as identity cards and driving licences, and booklets, such as passports, passbooks, identification documents, certificates, licences, cheque books and the like. The security sheet may be formed from a sheet comprising a plastic, which is typically polycarbonate. Plastic sheets are more durable than fibrous substrate security sheets and are resistant to delamination by a counterfeiter. During manufacture a number of thin plastic layers are laid over one another and laminated together, thereby forming a thicker plastic sheet.

The plastic security sheet usually contains personal data in the form of laser markings located within the thickness of the security sheet. A plastic security sheet may also comprise various other security features, such as antennas, UV responsive arrangements, optically variable features, windowed or transparent features, laser- perforations and tactile features. Forgers are known to adapt such security sheets by changing the personal data whilst maintaining the other security features. As the personal data is usually located beneath the surfaces of the security sheet, the forger will often try to abrade the material from one of the surfaces to reach the personal data. After changing the personal data the forger may add further plastic over the abraded area in an attempt to hide the adaptation.

Antennas are typically hidden under opaque regions of the security sheets since they are not considered aesthetically pleasing. However, WO-A-2017/006191 describes using an antenna to provide an overt security function by having the antenna visible through at least one transparent window of the security document. The antenna defines a visible security marking such as a word or logo and an image of the document holder can be juxtaposed or combined with the antenna. However, the arrangement of WO-A- 2017/006191 is generally directed to providing an additional security feature to deter counterfeiters (i.e. persons making entire fraudulent security sheets), rather than actually making the forgery or adaptation of the image of an authentic security sheet more difficult. Summary

An object of the present invention is to provide an improved security sheet that provides improved resistance to adaptation of the data thereon or to make any such forgery detectable. A further object is to provide an improved security feature that is hard to replicate and easy for a document inspector and/or holder to recognise. A further object is to provide an improved method of manufacture such a security document.

The present invention therefore provides a method of manufacturing a security sheet comprising a plastic substrate having opposing first and second outer surfaces, at least one mask at least partially embedded in or located on the plastic substrate and a laser markable region located between the second outer surface and the at least one mask, wherein the method comprises directing a laser from the first outer surface adjacent to the at least one mask and to the laser markable region, such that at least one mark aligned with the at least one mask is formed in the laser markable region. The method may comprise directing the laser onto at least part of the at least one mask, which blocks the laser from the laser markable region such that the at least one mark is aligned with the at least one mask.

The present invention also provides a security sheet comprising: a plastic substrate having opposing first and second outer surfaces; at least one mask at least partially embedded in or located on the plastic substrate; a laser markable region located between the second outer surface and the at least one mask; at least one mark in the laser markable region, aligned with the at least one mask. The at least one mark may be formed by a laser directed from the first outer surface and adjacent to the at least one mask to the laser markable region. The at least one mark may be formed by a laser directed from the first outer surface onto at least part of the at least one mask, which blocks the laser from the laser markable region.

A mark and an unmarked region under a mask are therefore in register and alignment with the mask. Any misalignment of the mark relative to the mask due to adaptation of the security sheet can be detected by a document inspector. As a result, the arrangement increases the difficulty of counterfeiting since the forger would need to try to have the new data exactly aligned with the mask. In particular, one or more edges of one or more mark(s) may be aligned with one or more edge(s) of one or more mask(s). The alignment may be along a direction normal to the first outer surface or at an acute angle to the first outer surface. Due to the blocking of the laser by the at least one mask, at least one unmarked region of the laser markable region may overlap the at least one mask and be adjacent to the at least one mark. Preferably the at least one mask comprises at least part of at least one RFID device and/or antenna, a region opaque to laser radiation, a vapour deposited metal pattern and/or a printed ink opaque pattern. Preferably the or each at least one mask comprises at least part of at least one antenna, since an antenna is typically unaffected by the laser directed upon it and is already present in the security sheet for providing biometric information. Furthermore, an antenna is typically relatively thin and thus insignificantly interrupts a continuous image, such as a portrait of a holder of the security sheet.

Preferably the at least one mask and at least one mark form at least one security element. Preferably the at least one security element defines at least one indicia, symbol, logo, image, alphanumeric character and/or machine readable code. Preferably the at least one security element forms at least part of personal data applied to the security sheet. The at least one security element preferable conveys covert or overt recognisable or intelligible information to a machine or human reader. As a result, at least one mask is an integral part of the at least one security element and the forger must have both in an aligned

arrangement or the forgery will be detectable.

Preferably the at least one mask is at least partially embedded in the plastic substrate and the at least one mark is formed by a laser directed from the first outer surface through the plastic substrate adjacent to the at least one mask to the laser markable region. Preferably the plastic substrate comprises at least one first transparent region extending between the first outer surface and at least part of the mask. Preferably the plastic substrate comprises at least one first substantially opaque region bounding or surrounding at least part of the perimeter of the at least one first transparent region to form at least one window at least partially overlying the at least one mark. Preferably the plastic substrate is formed from plurality of plastic layers laminated together.

Preferably the plastic substrate comprises at least one second transparent region and/or an opaque region extending between the second outer surface and at least part of the mask. Preferably the laser markable region is opaque or transparent. The security sheet preferably comprises a first laser markable region located between the second outer surface and the at least one mask; a second laser markable region located between the first outer surface and the at least one mask; at least one first mark in the first laser markable region, aligned with the at least one mask and formed by a laser directed from the first outer surface through the plastic substrate adjacent to the at least one mask; at least one unmarked region in the first laser markable region,

overlapping and aligned with the at least one mask and adjacent to the at least one first mark; and at least one second mark is formed in the second laser markable region.

Preferably the at least one first mark and at least one mask form at least one first security element and the at least one second mark forms at least one second security element, the first and second security elements being aligned with one another and/or having

substantially the same shape.

The present disclosure is further direction towards a security sheet formed by the aforementioned method and/or that of the present disclosure. The present disclosure is further directed towards a security document comprising the aforementioned security sheet, wherein the security document is a passport, identification document, identity card or driving licence. The present disclosure is further directed towards a plurality of such security documents, wherein personal data on the security sheet of each security document is different to personal data on the security sheet of other security documents.

Brief Description of the Drawings

By way of example only, embodiments of a method of manufacturing a security sheet and a security sheet in accordance with the present invention are now described with reference to, and as shown in, the accompanying drawings, in which:

FIGURE 1 A is a plan view of a security sheet in accordance with the present invention;

FIGURE 1 B is a cross-sectional side elevation of the security sheet of Figure 1A taken through section A-A;

FIGURE 1 C is a cross-sectional side elevation of a plurality of layers forming, after lamination, the security sheet of Figures 1A and 1 B through section A-A;

FIGURE 2A is a plan view of a first outer surface of a further embodiment of a security sheet in accordance with the present invention;

FIGURE 2B is a plan view of a second outer surface of the security sheet of Figure

2A; FIGURE 2C is a cross-sectional side elevation of the security sheet of Figures 1A and 1 B taken through section B-B;

FIGURE 2D is a cross-sectional side elevation of a plurality of layers forming, after lamination, the security sheet of Figures 2A to 2C through section B-B;

Detailed Description

Figures 1 A and 1 B illustrate a security sheet 10, in this case the data page for a passport, comprising a plastic substrate 1 1 having a first outer surface 12 and a second outer surface 13. Each of the first and second outer surfaces 12, 13 is preferably substantially flat and planar. The plastic substrate 1 1 is preferably formed from a laminar structure having a plurality of layers 14, 15, 16, 17, 18, 19, which are laminated into a substantially non-laminar or unitary structure. Figure 1 C illustrates the layers 14, 15, 16, 17, 18, 19 prior to lamination. The lamination may be by any known method, such as by fusing via the application of heat and pressure and/or by applying adhesive between the layers 14, 15, 16, 17, 18, 19.

The plastic from which the plastic substrate 1 1 and layers 14, 15, 16, 17, 18, 19 are formed may be a thermoplastic polymer such as polycarbonate, polyester, polyethylene, polypropylene or polyvinyl chloride. Polycarbonate is particularly suitable due to its high durability, its ease of manufacture and the ease with which security features can be incorporated within it. The plastic substrate 11 is preferably substantially rigid or at least semi-rigid, this preferably being a result of the thickness of its constituent layers 14, 15, 16, 17, 18, 19. Each of layer 14, 15, 16, 17, 18, 19 may be between approximately 0.05 mm thick and approximately 3 mm thick. The thickness of the plastic substrate 1 1 , which is the distance between the first and second outer surfaces 12, 13, is preferably at least approximately 150 μηι and more preferably at least approximately 300 μηι. In particular, the plastic substrate 1 1 may be between approximately 300 μηι and 1000 μηι thick and, for example, may be approximately 300 μηι thick or approximately 800 μηι thick. A mask 20 is at least partially and/or entirely embedded in the plastic substrate 1 1 between the first and second outer surfaces 12, 13. The mask 20 may comprise at least one mask region 25, 26, 27. The mask 20 is preferably embedded at least partially in or located on a mask layer 16 prior to lamination. Preferably the mask 20 is entirely embedded within the plastic substrate 1 1 as illustrated. ln the illustrated embodiment the mask 20 comprises at least part of a radio frequency identification (RFID) device 21 and, more particularly, an antenna 22 of an RFID device 21. The at least one mask region 25, 26, 27 of the antenna 22 preferably comprises at least two adjacent wire portions 25, 26, 27 (three are illustrated) separated by a gap 28, 29 (two are illustrated) between two adjacent wire portions 25, 26, 27. The at least two adjacent wire portions 25, 26, 27 are preferably formed by the same antenna 22 comprising a wire extending around a closed loop arrangement or coil multiple times as shown.

However, the at least two adjacent wire portions 25, 26, 27 may be formed by a plurality of antennas 22 having portions 25, 26, 27 located adjacent to one another.

The antenna 22 may be of any suitable form for a security sheet 10, particularly for an RFID device 21. For example, it may be configured to operate at low frequencies (for example 20-200 kHz), high frequencies (for example 2 to 30 MHz) or ultra-high frequencies (for example over 300 MHz). The antenna 22 may be located on or at least partially embedded in the mask layer 16 and may be at least one of: one or more copper wire(s), aluminium, etched aluminium, conducting silver paste, conducting inks, conducting pastes, conducting material, printed materials, electroplating, foils and the like. Suitable

embodiments are further disclosed in US-B-8348170. The antenna 22 is connected to a chip module 23 that preferably stores biometric information relating to the holder of the passport thereon. Preferably the RFID device 21 is passive and does not comprise an internal power supply. The antenna 22 is preferably configured to, upon interrogation by an RFID reader, supply power from the RFID reader to the chip module 23 and transmit biometric data from the chip module 23 to the RFID reader. The biometric data is preferably encoded on the chip module 23. In a preferred embodiment the RFID device 21 is configured in accordance with the standards set under Document 9303 ("Machine Readable Travel Documents") issued by the International Civil Aviation Organization (ICAO) and preferably that of the Seventh Edition (2015). The plastic substrate 1 1 preferably comprises at least one first transparent region

34 extending between the first outer surface 12 and at least part of the mask 20. The mask 20 is therefore at least partially visible through the at least one first transparent region 34 when viewed in reflected light incident upon the first outer surface 12 (e.g. from first and second positions 38, 39). The at least one first transparent region 34 may be formed during lamination from one or more entirely transparent first layers 14, 15 overlying the mask layer 16 as illustrated, in which the entire mask 20, antenna 22 and chip module 23 are visible from the first outer surface 12. Alternatively, the plastic substrate 11 may comprise at least one first substantially opaque region bounding or surrounding at least part of the perimeter of the at least one first transparent region 34 to form at least one window at least partially overlying the at least one mark 31. For example, the at least one first transparent region 34 may overlie just a portion of the antenna 22 and the rest of the antenna 22 and chip module 23 may be hidden from view from the first outer surface 12 by the first opaque region of the first layer(s) 14, 15.

A laser markable region 30 is located between the second outer surface 13 and the mask 20. The laser markable region 30 is configured for the formation of at least one mark 31 therein substantially permanently by a laser. In particular, the laser markable region 30 may be engravable by absorbing laser radiation to increase the temperature of localised areas and form a permanent discolouration, such as by melting, ablation or carbonation. The discolouration typically results in at least one black mark 31. Alternatively, the laser markable region 30 may be laser markable by bleaching.

The laser markable region 30 may be opaque or transparent. In the laser markable region 30 the plastic substrate 1 1 preferably comprises a laser markable additive for marking by the laser. For example, the laser markable region 30 may be formed from at least one laser markable layer 17 located adjacent to the mask layer 16 and comprising laser markable additive therein. The laser markable additive may comprise any suitable additive, such as at least one of titanium dioxide, mica, carbon, tin or antimony based oxides, copper based oxides, molybdenum based oxides and/or bismuth based oxides. As shown in further detail in Figure 1 B, the at least one mark 31 is aligned with and does not overlap or overlie the mask 20. At least one unmarked region 37 (i.e. at least one masked region) is located in the laser markable region 30, overlapping and aligned with the at least one mask region 25, 26, 27 of the mask 20 and adjacent to the at least one mark 31. In other words the at least one mark 31 , at least one unmarked region 37 and at least one mask region 25, 26, 27 of the mask 20 are in register with one another. At least one edge of the at least one mark 31 and at least one edge of at least one unmarked region 37 are directly aligned with or coincident with one another. The aligned edges of the at least one mark 31 and unmarked region 31 , 37 are directly aligned with the edge of the the at least one mask region 25, 26, 27 of the mask 20 along an axis normal to the planar first and second outer surface 12, 13 (i.e. a direction extending from position 38 to the first outer surface 12 and perpendicular to the first outer surface 12). Thus, when viewed from directly above the first outer surface 12 in reflected light incident thereupon as in Figure 1A or when viewed in cross-section as in Figure 1 B (e.g. from first position 38), the at least one unmarked region 37 is located in the laser markable region 30 directly underneath the at least one mask region 25, 26, 27 of the mask 20 whilst the at least one mark 31 is located in the laser markable region 30 directly adjacent to the mask 20 and at least one unmarked region 37. In the illustrated embodiment marks 31 extend under each of the gaps 28, 29 between the portions 25, 26, 27 of the antenna 22 and adjacent to the outer edges of the portions 25, 26, 27. The plastic substrate 1 1 preferably comprises at least one second transparent region 35 and/or a second opaque region 36 between the second outer surface 13 and at least part of the mask 20. In the illustrated embodiment an opaque region 36 is formed adjacent the laser markable region 30 by an opaque second layer 18 adjacent to the laser markable layer 17. A second transparent region 35 extends from the opaque region 36 to the second outer surface 13 and is formed by a transparent second layer 19 adjacent the opaque second layer 18. The opaque region 36 entirely blocks the mask 20 and RFID device 21 from view when the second outer surface 13 is view in reflected light incident thereupon. The opaque region 36 located behind the at least one mark 31 is preferred to improve the visibility of the at least one mark 31 from the first outer surface 12. In other embodiments, the plastic substrate 11 may comprise at least one second substantially opaque region 36 bounding or surrounding at least part of the perimeter of the at least one second transparent region 35 to form at least one window at least partially overlying the at least one mark 31. The at least one mark 31 and/or mask 20 may be visible in the at least one second transparent region 35 when the second outer surface 13 is view in reflected light incident thereupon.

The at least one mark 31 may form at least one security element 40 with at least part of the mask 20. The at least one security element 40 comprises recognisable information that can be interpreted or understood by a machine or human reader. The outer perimeter of the or each security element 40 is shaped as, or defines, at least one indicium, symbol, logo, image, alphanumeric character and/or machine readable code. The mask 20 may be differentiable from the at least one mark 31 when viewed in reflected light incident upon the first and/or second outer surface 12, 13 (e.g. from first and second positions 38, 39). This may be a result of the at least one mark 31 and mask 20 being formed of different materials or by different methods. However, preferably the shape of the outer perimeter of the at least one security element 40 cannot be completely formed or viewed in complete form without both the at least one mark 31 and at least part of the mask 20. For instance, in Figure 1 A the security element 40 forms a portrait image of the holder of the security sheet 10 and if the antenna 22 were to be removed the portrait image would be incomplete because it would comprise a series of blank lines extending directly across it.

Preferably the at least one security element 40 forms at least part of personal data 41 relating to and describing the personal details of the holder of the security sheet 10. The personal data 41 may also comprise at least one variable data element 42 applied to the security sheet 10. Fixed data 43, comprising at least one fixed data element 44, may also be applied to the security sheet 10. The at least one fixed and variable data element 42, 44 have an outer perimeter shaped as, or defining, at least one indicium, symbol, logo, image, alphanumeric character and/or machine readable code. Preferably the at least one fixed and variable data element 42, 44 are laser marked as illustrated, although they may be applied in any other suitable manner. For example, they may be applied by printing to one or more of the layers 14, 15, 16, 17, 18, 19 prior to lamination.

The personal data 41 is also known as "variable data" or "biographical data" and, typically, no two security sheets 10 issued by an issuing authority contain the same personal data 41. The fixed data 43 is, typically, the same across a plurality of security sheets 10. The Seventh Edition (2015) of Document 9303 ("Machine Readable Travel

Documents") issued by the International Civil Aviation Organization (ICAO) describes such biographical data and the personal and fixed data 41 , 43 may be implemented in accordance with the regulation set therein. In the illustrated embodiment the personal data 40 comprises the security element 40 forming the portrait image of the holder and a further plurality of variable data elements 42 conveying the name, nationality and date of birth of the holder (e.g. "A B C Smith, "British" and "10/02/1980). The fixed data 43 comprises a plurality of fixed data elements 44 conveying the text "Name", "Nationality" and "Date of Birth". The personal data 41 also typically includes a plurality of variable and fixed data elements 42, 44 forming a machine readable zone (not shown) containing machine readable data.

The security sheet 10 therefore comprises an effective security feature based upon the registration between the mask 20 and at least one mark 31. Should a forger abrade away the plastic substrate 1 1 from the second outer surface 13 underneath the at least one mark 31 , any replacement would need to be precisely aligned with the at least one mask region 25, 26, 27 of the mask 20. Any attempted further laser marking can also be difficult to perform due to the difficulties associated with adding suitable laser markable additives to the replacement film or material to cover the forged mark. Furthermore, any misaligned forgery could be easily detected. In particular, if the mask 20 or antenna 22 is viewed from a position at an acute angle to the plane of the security sheet 10 (e.g. from the second positions 39) it will appear out of register with the at least one mark 31 due to their differing depths (i.e. distances from the first and second outer surfaces 12, 13) in the security sheet 10. At an acute angle the at least one unmarked region 37 underneath the mask 30 would become visible. If the antenna 22 comprises multiple portions 25, 26, 27 then a forger would face the further difficulty of needing to register multiple marks 20 to the portions 25, 26, 27.

The security sheet 10 is generally manufactured by forming the laminar structure of the layers 14, 15, 16, 17, 18, 19, laminating them together to form the plastic substrate 1 1 and subsequently applying the personal data 41. The lamination is preferably a

substantially continuous and in-line method, similar to that of WO-A-2017/060684, WO-A- 2017/060688, WO-A-2015/104011 , US-B-6669813 and US-A-2011/0226408, although any suitable method may be implemented. The layers 14, 15, 16, 17, 18, 19 are also formed separately prior to being overlaid upon one another. They may be overlaid sequentially, but preferably they are mounted on feeding rolls or the like and brought together at

substantially the same time as, or just prior to, lamination.

If they form windows, the first and second transparent regions 34, 35 and at least one first and second opaque regions may also be formed as described in WO-A- 2017/060684 and WO-A-2017/060688. In particular, the transparent region(s) 30, 35 may be formed from a transparent insert located in a correspondingly shaped aperture in an opaque plastic layer. Preferably the aperture and insert are formed and brought together by a single punch tool in line.

During lamination a laminator fuses the layers 14, 15, 16, 17, 18, 19, having a mask 20 embedded therein and/or therebetween, together by the application of heat and pressure to form the plastic substrate 11. Preferably the laminator comprises continuous belts for drawing the layers 14, 15, 16, 17, 18, 19 between sequential heating and cooling devices. During the heating process each of the layers 14, 15, 16, 17, 18, 19 become at least softened or semi-molten (i.e. a liquid of relatively high viscosity) so that the plastic flows and mixes together across the interfaces between them, thereby forming the substantially unitary plastic substrate 1 1. In order to achieve such fusing the heating devices raise the temperature and pressure applied to the layers 14, 15, 16, 17, 18, 19 to reach the softening point of the plastic. Alternatively and/or in addition to fusing the layers 14, 15, 16, 17, 18, 19 together they may be adhered together by one or more regions of adhesive between them.

After the plastic substrate 1 1 has exited the laminator it is typically cut into a plurality of security sheets 10. The fixed data 43 may be applied before or after lamination. Each security sheet 10 itself may form a security document (e.g. a licence), or it may form part of a security document (e.g. in a passport). The security document may be of any suitable type having the security sheet 10, including banknotes, cards, such as identity cards, driving licences and the like, and booklets, such as passports, passbooks, identification documents, certificates, licences, cheque books and the like. In the case of booklets, the security sheet 10 may be attached therein by stitching one or more of the layers 14, 15, 16, 17, 18, 19 to a cover or one or more paper or polymer leaves. As is known in the art, one or more of the layers 14, 15, 16, 17, 18, 19 may extend from the rest of the layers 14, 15, 16, 17, 18, 19 to form a hinge or attachment portion to facilitate the stitching or other attachment method. In a particular preferred embodiment the hinge may comprise at least part of at least one mask layer 16 and/or at least one laser markable layer 17.

The at least one mark 31 is preferably applied to the plastic substrate 11 after lamination and may be applied before or after the security sheet 10 is incorporated into the security document. A laser 45 (i.e. laser radiation emitted by a laser device) is directed onto the first outer surface 12, from the first outer surface 12 and through the plastic substrate 1 1 into the laser markable region 30 to form the at least one mark 31 , for example by engraving (as discussed above). In particular, the laser 45 is directed through the at least one first transparent region 34, whether a window or covering the entire mask 20 and/or first outer surface 12. The laser 45 is also directed onto at least one mask region 25, 26, 27 of the mask 20, but the at least one mask region 25, 26, 27 partially blocks the laser markable region 30 from the laser 45, or prevents transmission of the laser from the first outer surface 12 to the laser markable region 30, such that the laser markable region 30 comprises at least one unmarked region 37 overlapping the at least one mask region 25, 26, 27. The laser 45 may be of any suitable type for marking, whether by bleaching, engraving or the like, the laser markable region 30. Thus wavelength and power of the laser 45 may be selected, as is known in the art, based upon the construction of the security sheet 11. Particular considerations include the type of laser markable additive and the thickness and/or materials of the layers 14, 15, 16, 17, 18, 19. Generally the

wavelength of the laser radiation is in the range from approximately 240 nm to

approximately 1 1000 nm. For example, the laser may be a DPSS (diode pulsed solid state) laser emitting radiation at a wavelength of approximately 532 nm, an Nd-YAG (neodymium- doped yttrium aluminium garnet) pulse laser having a wavelength of approximately 1064 nm, a fibre laser or a carbon dioxide continuous or COa laser with a wavelength of approximately 10600 nm.

Since the laser 45 is directed from the first outer surface 12 and passes over and adjacent to the mask 20, the at least one mark 31 and at least one unmarked region 37 will be registered or aligned with the mask 20 (particularly their edges). As discussed above, such accurate registration substantially increases the difficulty of forging the security sheet 10.

Various alternatives to those described above also fall within the scope of the present invention. The plastic substrate 11 may comprise a plurality of masks 20 and the at least one security element 40 may be formed from at least part of the plurality of the masks 20 and at least one mark 31. After laser marking, further layers could be applied over the plastic substrate 11.

The mask 20 may be located on and/or at least partially embedded in the plastic substrate 10 such that it is at least partially exposed at the first outer surface 12. Preferably the mask 20 is located over the first outer surface 12 and/or prevents the laser 45 from reaching the first outer surface 12. For example, the mask layer 16 may be located at and form the first outer surface 12 (i.e. there is no first transparent region 34 and/or first layers 14, 15) and the mask 20 may be located on and/or at least partially embedded in the surface of the mask layer 16. Alternatively, the mask 20 may be located on the surface of the laser markable region 30 or at least one laser markable layer 17, or on a transparent layer(s) located over the at least one laser markable layer 17 and forming the first outer surface 12. In particular, the mask 20 may comprise an antenna 22 printed and/or adhered to the first outer surface 12. The mask 20 may be at least partially exposed at the first outer surface 12 during normal use of the security sheet, although it may instead only be at least partially exposed at the first outer surface 12 during the formation of the at least one mark 31 and subsequently covered by further plastic layers. The laser 45 is directed onto the first outer surface 12 and it travels into the laser markable region 30 to form the at least one mark 31. Depending upon the arrangement of the mask 20, the laser 45 may travel through the mask layer 16, through the surface of the laser markable region or through any transparent layer(s) located over the at least one laser markable layer 17 prior to reaching the at least one laser markable layer 17. The laser 45 is also directed onto at least one mask region 25, 26, 27 of the mask 20, but the at least one mask region 25, 26, 27 partially blocks the laser markable region 30 from the laser 45 by at least partially preventing it from transmitted to the first outer surface 12 and/or through the plastic substrate 11 to the laser markable region 30.

The security sheet 10 may comprise a plurality of laser markable regions 30, 50, as illustrated in Figures 2A to 2D. The same reference numerals as in Figures 1A to 1 C have been used where appropriate to indicate corresponding features. The security sheet 10 comprises a second laser markable region 50 in addition to the first laser markable region 30 described in respect of Figures 1A to 1C. The second laser markable region 50 is located between the first outer surface 12 and the mask 20 and may be formed by a laser markable first layer 15 comprising a laser markable additive. The second laser markable region 50 may be separated from the first outer surface 12 by an at least partially transparent first layer 14 as illustrated or, alternatively, it may form the first outer surface 12.

The laser 45 is applied from the first outer surface 12 through the second laser markable region 50, onto and adjacent to the mask 20 and into the first laser markable region 30. Thus the laser simultaneously forms at least one second mark 51 in the second laser markable region 50 in addition to the at least one first mark 31 in the first laser markable region 30, which is formed as described in respect of Figures 1A to 1C. At least one first security element 40 is formed by the at least one first mark 31 and the mask 20. However, since the second laser markable region 50 is above the mask 20 the at least one second security element 52 is formed therein entirely by the at least one second mark 51. In order to achieve the simultaneous marking, the first laser markable regions 30 may have a higher sensitivity to laser marking than the second laser markable region 50. The different sensitivities may be achieved by differing quantities and/or types of laser markable additive in the first layer 15 and the laser markable layer 17. As a result, upon application of the laser, the at least one first mark 31 forms more quickly than the at least one second mark 51 and the formation of the at least one second mark 51 does not hinder the formation of the at least one first mark 31. The at least one first and second security elements 40 are registered to each other and have exactly the same shape. As a result, the difficulty of counterfeiting and forging the security sheet 10 is increased since the counterfeiter or forger needs to ensure that the first and second security elements 40, 52 are registered to each other in addition to the at least one first mark 31 being registered to the mask 20. Furthermore, the appearance and/or intensity of the first and second marks 31 , 51 may differ such that they are distinguishable from one another. Figures 2A to 2D also further illustrate the first and second security elements 40, 52 being visible in at least one window 53. In particular, the at least one first transparent region 34 extends from the first outer surface 12 and to the mask 20, but is at least partially surrounded or enclosed by a first opaque region 54. For example, the laser markable first layer 15 may be substantially opaque, forming the first opaque region 54, and comprise a transparent area or insert 55 located therein. The at least one second transparent region 35 extends from the second outer surface 13 to the mask 20, but is at least partially surrounded or enclosed by a second opaque region 36. For example, the second layer 18 may be substantially opaque, forming the second opaque region 36, and comprise a transparent area or insert 56 located therein. The first laser markable region 30 is also transparent.

As a result, when the first outer surface 12 is viewed in reflected light incident thereupon the second security element 52 is visible in the at least one window 53. When the second outer surface 13 is viewed in reflected light incident thereupon the first security element 40 is visible in the at least one window 53. A document inspector can therefore check both the first and second security elements 40, 52 for alignment.

In the above embodiments the laser 45 is focused along a direction normal to the plane of the security sheet 1 1 and its first and/or second outer surface 12, 13 (e.g. from the first position 38). The at least one (first) mark 31 and mask 20 are therefore aligned along the direction normal to the plane of the first outer surface 12. Thus misalignment between the at least one (first) mark 31 and mask 20 is visible when the first or second outer surface 12, 13 is viewed at an acute angle to the plane of the security sheet 10 (e.g. from the second position 39). However, the laser 45 may instead be focused along a direction at an acute angle to the plane of the security sheet and its first and/or second outer surface 12, 13 (e.g. from the second position 39). The at least one (first) mark 31 and mask 20 are therefore aligned along the direction at an acute angle to the plane of the first outer surface 12. As a result, the at least one (first) mark 31 and mask 20 will only appear aligned when the first or second outer surface 12, 13 is viewed at an acute angle to the plane of the security sheet 10 (e.g. from the second position 39).

Furthermore, Figures 1 B, 1C, 2C and 2D show merely exemplary arrangements of the layers 14, 15, 16, 17, 18, 19. For example, one or more at least partially transparent layers or regions could be located between any two of the layers 14, 15, 16, 17, 18, 19 (particularly between the mask 20 and the laser markable layer 17 or laser markable region 30). One or more of the layers 14, 15, 16, 17, 18, 19 may also comprise at least one further window, which may overlap the mask 20 and/or at least one mark 31 , 51. The security sheet 10 may comprise a plurality of laser markable regions 30 or layers 17 located between the mask 20 and the second outer surface 13, optionally with one or more transparent regions or layers between the laser markable regions 30 or layers 17.

In the aforementioned embodiments the mask 20 comprises the antenna 22, but it may instead comprise the chip module 24 or other part of the RFID device 21. The mask 20 may alternatively comprise any region or material opaque to the laser radiation. For example, the mask 20 may comprise a vapour deposited metal pattern and/or a printed ink opaque pattern.

The plastic substrate 1 1 and one or more layers 14, 15, 16, 17, 18, 19 may comprise at least one further security device embedded therein or located thereon.

Graphical information, colours and/or patterns may be printed on the outer surfaces of the layers 14, 15, 16, 17, 18, 19 prior to or after lamination. The at least one security device may, for example, comprise laser markings, printed ink, holograms, UV responsive features, optically variable features, windowed or transparent features, laser-perforations and the like. The at least one security device may be visible when viewed in reflected light by virtue of being located in the at least one first and/or second transparent region 34, 35. Alternatively the at least one security device may be covert, such as by being located in at least one first and/or second opaque region 36, such that it is not visible when viewed in reflected light.

Claims

CLAIMS:

1. A method of manufacturing a security sheet comprising a plastic substrate having opposing first and second outer surfaces, at least one mask at least partially embedded in or located on the plastic substrate and a laser markable region located between the second outer surface and the at least one mask, wherein the method comprises directing a laser from the first outer surface onto at least part of the at least one mask, which blocks the laser from the laser markable region, and adjacent to the at least one mask and to the laser markable region, such that at least one mark aligned with the at least one mask is formed in the laser markable region.

2. A method as claimed in claim 1 wherein the laser is emitted along a direction normal to the first outer surface such that the at least one mark and at least one mask are aligned along the direction normal to the first outer surface.

3. A method as claimed in claim 2 wherein the laser is emitted along a direction at an acute angle to the first outer surface such that the at least one mark and at least one mask are aligned along the direction at the acute angle to the first outer surface.

4. A method as claimed in any one of the preceding claims wherein the at least one mask comprises at least part of at least one RFID device and/or antenna, a region opaque to laser radiation, a vapour deposited metal pattern and/or a printed ink opaque pattern .

5. A method as claimed in claim 4 wherein the at least one mask comprises an antenna, wherein the antenna comprises:

at least two adjacent wire portions separated by a gap and the at least one mark overlaps the gap; and/or

at least one of aluminium, etched aluminium, conducting silver paste, copper wire(s), conducting inks, conducting pastes, conducting material, printed materials, electroplating and foils.

6. A method as claimed in any one of the preceding claims wherein the at least one mask and at least one mark form at least one security element.

7. A method as claimed in claim 6 wherein:

the at least one security element defines at least one indicia, symbol, logo, image, alphanumeric character and/or machine readable code; and/or the method comprise applying personal data to the security sheet and the at least one security element forms at least part of the personal data.

8. A method as claimed in any one of the preceding claims wherein the at least one mask is at least partially embedded in the plastic substrate and the method comprises directing the laser from the first outer surface through the plastic substrate adjacent to the at least one mask and to the laser markable region.

9. A method as claimed in any one of the preceding claims wherein the plastic substrate comprises at least one first transparent region extending between the first outer surface and at least part of the mask, the laser being directed through the at least one first transparent region.

10. A method as claimed in claim 9 wherein the plastic substrate comprises at least one first substantially opaque region bounding or surrounding at least part of the perimeter of the at least one first transparent region to form at least one window at least partially overlying the at least one mark.

1 1. A method as claimed in any one of the preceding claims wherein:

the plastic substrate comprises at least one second transparent region and/or an opaque region extending between the second outer surface and at least part of the mask; and/or

the laser markable region is opaque or transparent.

12. A method as claimed in any one of the preceding claims comprising forming the plastic substrate by laminating together a plurality of plastic layers and at least one mask embedded in, on and/or between the plurality of plastic layers.

13. A method as claimed in any one of claims 8 to 12 wherein the security sheet comprises:

a first laser markable region located between the second outer surface and the at least one mask; and

a second laser markable region located between the first outer surface and the at least one mask,

wherein the method comprises directing a laser from the first outer surface through the plastic substrate, through the second laser markable region, adjacent to the at least one mask and to the first laser markable region, such that at least one first mark is formed in the first laser markable region and at least one second mark is formed in the second laser markable region.

14. A method as claimed in claim 13 wherein the at least one first mark and at least one mask form at least one first security element and the at least one second mark forms at least one second security element, the first and second security elements being aligned with one another and/or having substantially the same shape.

15. A security sheet comprising:

a plastic substrate having opposing first and second outer surfaces;

at least one mask at least partially embedded in or located on the plastic substrate; a laser markable region located between the second outer surface and the at least one mask;

at least one mark in the laser markable region, aligned with the at least one mask and formed by a laser directed from the first outer surface onto at least part of the at least one mask, which blocks the laser from the laser markable region, and adjacent to the at least one mask to the laser markable region.

16. A security sheet as claimed in claim 15 wherein the at least one mask comprises at least part of at least one RFID device and/or antenna, a region opaque to laser radiation, a vapour deposited metal pattern and/or a printed ink opaque pattern.

17. A security sheet as claimed in claim 15 or claim 16 wherein:

the at least one mask is at least partially embedded in the plastic substrate and the at least one mark is formed by a laser directed from the first outer surface through the plastic substrate adjacent to the at least one mask to the laser markable region;

the laser markable region is opaque or transparent.

18. A security sheet as claimed in claim 17 further comprising:

a first laser markable region located between the second outer surface and the at least one mask; a second laser markable region located between the first outer surface and the at least one mask;

at least one first mark in the first laser markable region, aligned with the at least one mask and formed by a laser directed from the first outer surface through the plastic substrate adjacent to the at least one mask;

at least one unmarked region in the first laser markable region, overlapping and aligned with the at least one mask and adjacent to the at least one first mark; and

at least one second mark is formed in the second laser markable region.

19. A security document comprising the security sheet of any one of claims 15 to 18, wherein the security document is a passport, identification document, identity card or driving licence.

20. A plurality of security documents as claimed in claim 19, wherein personal data on the security sheet of each security document is different to personal data on the security sheet of other security documents.