FIELD OF THE INVENTION

[0001 ] The present invention relates to an arrangement and method for mitigating tear propagation in a document, such as a banknote.

BACKGROUND OF THE INVENTION

[0002] Polymer-based documents, such as banknotes, have high tear initiation strength and high durability for general use and wear. Polymer-based banknotes are normally very difficult to tear manually. However, due to the nature of polymer materials which are non-fibrous and crystalline, polymer-based documents exhibit a low tear propagation resistance after a tear has been initiated. When a tear has been initiated on a polymer banknote, for example as a small nick created by a pair of scissors, the tear can readily propagate through the banknote.

[0003] Depending on the location of the initiated tear point, a tear in the banknote can easily split the banknote into half. These damaged notes are an inconvenience to a user and need to be removed from circulation, adding costs to the central bank.

[0004] Further, torn banknotes can disrupt the operation of banknote processing machines. A tear in a banknote can further propagate through the banknote when the banknote is being processed by banknote processing machines, to an extent where the banknote may be torn into pieces. As a result, the banknote processing machine could be jammed by torn pieces of the banknote, causing downtime and possible need for machine repairs.

[0005] It is desirable to provide a document having an improved durability in which propagation of any tears in the document are inhibited or mitigated, or to at least provide a useful choice. SUMMARY OF THE INVENTION

[0006] A first aspect of the present invention provides a polymeric-based document comprising a substrate and at least one tear-arresting gap in the substrate, wherein the at least one tear-arresting gap mitigates propagation of a tear in the substrate through the tear-arresting gap.

[0007] In an embodiment, the tear arresting gap inhibits propagation of a tear when the tear reaches the tear arresting gap. Propagation of a tear may be substantially terminated at the tear arresting gap or the tear arresting gap slows down the propagation, dissipating energy, before the tear is arrested close by, potentially at another tear arresting gap. Thereby, tear arresting gaps in the document effectively contains or localises the propagation of tear in the document and prevents the tear from further propagating in the document.

[0008] In an embodiment, the at least one tear-arresting gap is a hole that extends completely through the substrate, and more preferably a microperforation.

[0009] The use of small holes and microperforations as security elements in banknotes has previously been proposed, for example in WO 2004/01 1274 A1 and WO 2013/143007 A1. However, the use of small holes and cavities specifically for the purpose of inhibiting or terminating the propagation of a tear through the holes or cavities is not disclosed in either of these documents.

[0010] The at least one tear-arresting gap may be formed by laser ablation, that is removal of part of the material of the substrate by the use of a laser. If the at least one tear-arresting gap is formed by laser ablation, the tear-arresting gap may have a ‘melt pool’ around the tear-arresting gap. A‘melt pool’ is an area around a tear- arresting gap created by the laser beam that melts the material of the substrate in the borders or edges of the tear-arresting gap. That is, the gap created by the laser may have some of the material ablated by the laser and some of the material melted. The melted material tends to be around the edge or border of the hole and creating the‘melt-pool’. The melt-pool edge distance of the at least one tear-arresting gap, that is the distance from the edge of the tear-arresting gap to the edge of the melt pool, is preferably less than about 0.5 mm in some embodiments. In another embodiment, the at least one tear-arresting gap may be formed in the substrate by boring, piercing, or punching. However, these processes are less desirable due to the risk of creating‘nicks’ or tears in the document. Furthermore, boring, piercing or punching can also create material from the document to protrude at the edges of the perforation. When many such documents are stacked on top of one another, this creates an uneven‘profile’ of the stacked documents, which is generally undesirable and, in some cases, unacceptable in further processing steps. In a further embodiment, the at least one tear-arresting gap may be pre-formed in the substrate.

[0011 ] The at least one tear-arresting gap may be a through-hole. Where a tear- arresting gap is a through-hole, the tear-arresting gap extends completely through the substrate. Alternatively, the at least one tear-arresting gap may only partially extend through the substrate. Where a tear-arresting gap partially extends through the substrate, the tear-arresting gap may form a dimple or a recess in the substrate. In a further alternative embodiment, the tear-arresting gap may be a cavity formed within the substrate. For example, the cavity may be an air bubble.

[0012] In an embodiment, the document comprises a plurality of tear-arresting gaps. A plurality of tear-arresting gaps may comprise a combination of one or more through-holes, holes that partially extend through the substrate, and/or one or more cavities formed within the substrate.

[0013] The at least one tear-arresting gap preferably has a maximum width. The maximum width of a tear-arresting gap corresponds to a dimension of the tear- arresting gap where the width of the tear-arresting gap across the substrate is the greatest. For example, the maximum width may be a diameter where the tear- arresting gap is substantially circular. Preferably, the maximum width of the at least one tear-arresting gap falls substantially within the range from about 20 pm to about 200 pm. More preferably, the maximum width falls substantially within the range from about 50 pm to about 100 pm. Larger widths are also acceptable where the gaps can be perceived by the human eye. For example, the maximum width of the tear-arresting gaps could be greater than 200 pm. Preferably, the maximum width of the tear-arresting gap along a depth of the tear-arresting gap is substantially constant. Alternatively, the maximum width of the tear-arresting gap along the depth of the tear-arresting gap may vary. For example, the maximum width of the tear- arresting gap along the depth of the tear-arresting gap may be increasing or decreasing from a surface of the substrate.

[0014] The at least one tear-arresting gap is preferably positioned at least about 2 mm from an edge of the substrate. More preferably, the at least one tear-arresting gap is positioned at least about 10 mm from the edge of the substrate, and even more preferably, at least about 20 mm from the edge of the substrate.

[0015] In a preferred embodiment, the document comprises a plurality of tear- arresting gaps in the substrate and a distance between adjacent tear-arresting gaps is at least about 0.2 mm. Preferably, the distance between adjacent tear-arresting gaps is at least about 1 mm, and more preferably the distance between adjacent tear-arresting gaps is at least 2 mm. In an embodiment, the tear-arresting gaps are provided periodically in the substrate. In an alternative embodiment, the tear- arresting gaps are provided aperiodically or randomly in the substrate.

[0016] The document preferably includes three or more tear-arresting gaps arranged in close proximity to each other in the substrate. Three or more of the tear- arresting gaps may be arranged in a straight line. In an alternative or additional embodiment, three or more of the tear-arresting gaps may be arranged in a curved, sinusoidal, or zig-zag pattern. Alternatively or additionally, the tear-arresting gaps may have a random distribution in the substrate.

[0017] In one embodiment, the document comprises a plurality of tear-arresting gaps in the substrate, and the shapes and/or sizes of the tear-arresting gaps in the substrate are the same. In another embodiment, the shapes and/or sizes of the tear- arresting gaps in the substrate may be different.

[0018] Three or more adjacent tear-arresting gaps in the substrate may have a size that increases or decreases in a direction from an edge of the substrate. In an alternative embodiment, the sizes of the tear-arresting gaps in the substrate may vary in a random manner. [0019] In one embodiment, the at least one tear-arresting gap is substantially circular in a plane of the substrate. In an alternative embodiment, the at least one tear-arresting gap is substantially elliptical in a plane of the substrate. The plane is on or through the substrate and is parallel to a surface of the substrate. When a plurality of tear-arresting gaps is provided, the document may include a combination of different shaped tear-arresting gaps, such as substantially circular and elliptical tear-arresting gaps. Other shapes for the tear-arresting gap are envisaged in the specification. Shapes which have curved edges are preferable for the tear-arresting gaps. Tear arresting gaps with curved edges dissipate tear energy more effectively than gaps which have abrupt or sharp corners. In an additional or alternative embodiment, a diameter or width of the tear-arresting gap through the substrate increases or decreases from a surface of the substrate. In that embodiment, the tear-arresting gap may be conical or frustoconical, or may have a trapezoidal shape.

[0020] The at least one tear-arresting gap may extend in a direction substantially parallel to a normal to a surface of the substrate. In an alternative embodiment, the at least one tear-arresting gap may extend at an angle to a normal to a surface of the substrate. When a plurality of tear-arresting gaps is provided, the tear-arresting gaps may include a combination of tear-arresting gaps that extend at different angles relative to a normal to a surface of the substrate. Preferably, the at least one tear- arresting gap extends at an angle from about 0° to about 80°, and more preferably from about 0° to about 60°, to the normal to the surface of the substrate.

[0021 ] In one embodiment, the substrate may be formed from a composite material including at least one layer of paper and at least one layer of polymeric material.

[0022] In an embodiment, the substrate is overcoated with a coating and the at least one tear arresting gap is provided in the substrate after the substrate is overcoated with the coating such that the coating is also provided with gaps. The coating is preferably an opacifying layer or a transparent coating, such as a transparent varnish. The coating may comprise a polyethylene melt coat, an acrylic emulsion, a PVDC emulsion, and/or a rubber emulsion. [0023] In an embodiment, an area of the substrate with the at least one tear- arresting gap is overcoated with a coating. The coating is preferably an opacifying layer. Alternatively, the coating is transparent, such as a transparent varnish, as often used as a finishing step in banknote printing. The coating may comprise a polyethylene melt coat, an acrylic emulsion, a PVDC emulsion, and/or a rubber emulsion. In this manner, through holes in the substrate can be made into‘dimples’, as the coating will naturally fill the hole.

[0024] A second aspect of the present invention provides the use of at least one tear-arresting gap in a polymeric based document to mitigate propagation of a tear in the document through the at least one tear-arresting gap.

[0025] A third aspect of the present invention provides a method of

manufacturing a polymeric-based document comprising:

providing a substrate

providing at least one tear-arresting gap in the substrate, wherein the at least one tear-arresting gap mitigates propagation of a tear in the substrate through the tear-arresting gap.

[0026] The method preferably comprises providing the at least one tear-arresting gap in the substrate by laser ablation, in which part of the material of the substrate is removed by the use of a laser. If the at least one tear-arresting gap is formed by laser ablation, the method comprises forming a‘melt-pool’ around the tear-arresting gap. The method preferably comprises providing the at least one tear-arresting gap in the substrate by laser ablation with a melt-pool edge distance, that is the distance from the edge of tear-arresting gap to the edge of the melt-pool of less than about 0.5 mm. In another embodiment, the method comprises providing the at least one tear-arresting gap by boring, piercing, or punching. However, these processes are less desirable due to the risk of creating‘nicks’ or tears in the document.

Furthermore, boring, piercing or punching can also create material from the document to protrude at the edges of the perforation. When many such documents are stacked on top of one another, this creates an uneven‘profile’ of the stacked documents, which is generally undesirable and, in some cases, unacceptable in further process steps. [0027] In an embodiment, the method comprises overcoating an area of the substrate with a coating and then providing the at least one tear-arresting gap in the substrate after the substrate is overcoated with the coating, such that the coating is also provided with at least one gaps corresponding to the tear arresting gap in the substrate. The coating is preferably an opacifying layer. Alternatively, the coating is a transparent coating, such as a transparent varnish.

[0028] In a further embodiment, the method comprises pre-forming the at least one tear-arresting gap in the substrate.

[0029] In this embodiment, the method may comprise overcoating an area of the substrate with the at least one tear-arresting gap with a coating. The coating is preferably an opacifying layer. Alternatively, the coating is transparent, such as a transparent varnish, as often used as a finishing step in banknote printing. The coating may comprise a polyethylene melt coat, an acrylic emulsion, a PVDC emulsion, and/or a rubber emulsion. In this manner, through holes in the substrate can be made into‘dimples’, as the coating will naturally fill the gap.

[0030] In a fourth aspect, the present invention provides a polymeric-based document when manufactured by the method according to the third aspect of the invention described above.

[0031 ] Embodiments of the second, third, and fourth aspects of the present invention are similar to the embodiments previously described with reference to the first aspect.

[0032] As used herein, the terms‘comprises’,‘comprising’, and grammatical variations thereof are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0033] As used herein, the term‘and/or’ means‘and’,‘or’ or both. Document or Token

[0034] As used herein, the terms‘document’ and‘token’ includes all types of documents and tokens of value and identification documents including, but not limited to the following: security documents, items of currency such as banknotes, credit cards, cheques, passports, identity cards, securities and share certificates, driver’s licenses, deeds of title, travel documents such as airline and train tickets, entrance cards and tickets, birth, death and marriage certificates, and academic transcripts.

[0035] The invention is particularly, but not exclusively, applicable to documents or tokens such as banknotes or identification documents such as identity cards or passports formed from a substrate to which one or more layers of printing are applied. The diffraction gratings and optically variable devices described herein may also have application in other products, such as packaging.

Substrate

[0036] As used herein, the term‘substrate’ refers to the base material from which the document or token is formed. The base material may be paper or other fibrous material such as cellulose; a plastic or polymeric material including but not limited to polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET), biaxially-oriented polypropylene (BOPP); or a composite material of two or more materials, such as a laminate of paper and at least one plastic material, or of two or more polymeric materials.

Opacifying layers

[0037] One or more opacifying layers may be applied to a transparent substrate to increase the opacity of the document. An opacifying layer is such that LT < Lo, where Lo is the amount of light incident on the document, and LT is the amount of light transmitted through the document. An opacifying layer may comprise any one or more of a variety of opacifying coatings. For example, the opacifying coatings may comprise a pigment, such as titanium dioxide, dispersed within a binder or carrier of heat-activated cross-linkable polymeric material. Alternatively, a substrate of transparent plastic material could be sandwiched between opacifying layers of paper or other partially or substantially opaque material to which indicia may be

subsequently printed or otherwise applied.

[0038] Where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0039] The invention consists in the foregoing and also envisages constructions of which the following gives examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Embodiments of the present invention will now be described by way of non-limiting example with reference to the accompanying figures, in which:

[0041 ] Figure 1 shows a schematic plan view of a document according to an embodiment of the present invention;

[0042] Figure 2 shows a schematic plan view of laser ablated tear-arresting holes in a substrate according to an embodiment of the present invention;

[0043] Figures 3A and 3B show schematic plan views of a substrate with different arrangements of tear-arresting holes in the substrate according to an embodiment of the present invention;

[0044] Figures 4A and 4B show schematic plan views of a substrate with different configurations of the tear-arresting holes in the substrate according to another embodiment of the present invention; and

[0045] Figures 5A to 5C show schematic sectional views of a substrate with different angles of the tear-arresting holes in the substrate according to a further embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0046] Referring to Figure 1 , a polymeric-based document 100 comprises a substrate 120 and a plurality of tear-arresting gaps, which in this embodiment are tear arresting holes 140 in the substrate 120. The substrate 140 is preferably a transparent substrate formed from a plastic or polymeric material, such as a polypropylene film, and more preferably a transparent biaxially oriented

polypropylene (BOPP) film. BOPP films inherently have a high durability and high tear initiation strength, but can exhibit a low tear propagation resistance, after a tear has been initiated.

[0047] The substrate 120 with the tear-arresting holes may be overcoated with a coating, such as an opacifying layer (not shown), such that the tear-arresting holes are not readily visible. Depending on the configuration or arrangement of the holes, the tear-arresting holes 140 may only be visible when the document is viewed at certain lighting conditions.

[0048] The tear-arresting holes 140 mitigate propagation of a tear in the substrate 120 through the tear-arresting holes 140. In other words, the tear-arresting holes 140 are configured or arranged to terminate a propagation of a tear that propagates in the substrate 120 towards any one of the tear-arresting holes. When a tear propagates towards and reaches at a respective one of the tear-arresting holes 140, the tear does not propagate any further in the substrate 120. Thereby, the tear in the substrate 120 that propagates towards the tear-arresting hole 140 is arrested by the tear-arresting hole 140. The tear-arresting holes 140 are configured or arranged to mitigate or inhibit tear propagation in the substrate 120.

[0049] The tear-arresting holes 140 in the substrate 120 may be provided by laser ablation of material of the substrate 120. Referring to Figures 2A and 2B, each of the laser ablated holes 140 can have a‘melt-pool’ 160. A‘melt pool’ is an area around a tear-arresting hole created by the laser beam that melts the material of the substrate in the borders or edges of the tear-arresting hole. Preferably, each of the tear-arresting holes 120 has a melt-pool edge distance d, which is a distance from an edge of the tear arresting hole 140 to an edge of the melt-pool 160, of less than about 0.5 mm. Alternatively, each of the tear-arresting holes 140 can be provided by laser ablation without a melt-pool. According to other embodiments of the invention, the substrate may be provided with a combination of at least one tear-arresting hole with a melt-pool and at least one tear-arresting hole without a melt-pool. The substrate may be laser ablated such that the tear-arresting gap has a varying diameter or width through the substrate.

[0050] Each of the tear-arresting gaps is a tear arresting holes 140, which is a through-hole that extends completely through the substrate 120 of the document 100 as shown in Figures 5A to 5C. However, in alternative or additional embodiments of the present invention, the tear-arresting gaps may only partially extend through the substrate, such that the tear-arresting gap substantially forms a dimple or a recess in the substrate. In yet further alternative or additional embodiments, the tear-arresting gaps may be a cavity formed within the substrate (i.e. the cavity may be an air bubble or pocket of air in the substrate). According to embodiments of the invention, the tear-arresting gaps can comprise a combination of one or more through-holes, holes that partially extend through the substrate, and/or cavities formed within the substrate.

[0051 ] The tear-arresting holes 140 have a maximum width, in this case - a diameter of the holes, falls substantially within the range from about 20 pm to about 200 pm. Preferably, the diameter of the tear-arresting holes falls substantially within the range from about 50 pm to about 100 pm. According to embodiments of the invention, one or more of the tear-arresting holes in a substrate can have a maximum width that is different from a maximum width of other tear-arresting holes in the substrate. According to still further embodiments of the invention, the holes can have a width that can be perceived or is resolvable by the human eye. By way of example, the width of the holes could be greater than 200 pm.

[0052] The tear-arresting holes 140 are positioned at least about 2 mm from an edge of the substrate 120. Preferably, each tear-arresting hole is positioned at least about 10 mm from the edge of the substrate. More preferably, each tear-arresting hole is positioned at least about 20 mm from the edge of the substrate. According to embodiments of the invention, one or more tear arresting holes in a substrate can have a distance to an edge of the substrate that is different from a distance of other tear-arresting holes to the edge of the substrate.

[0053] A distance between adjacent tear-arresting holes 140 is at least about 0.2 mm. Preferably, the distance between adjacent tear-arresting holes is at least about 1 mm, and more preferably at least about 2 mm. The tear-arresting holes are provided periodically in the substrate, where the distance between the tear-arresting holes is constant. According to embodiments of the invention, a distance between some of the tear-arresting holes in a substrate may be constant, while a distance between other tear-arresting holes in the substrate may be random.

[0054] The document 100 comprises three or more tear-arresting holes 140 arranged in close proximity to each other in the substrate 120 that are arranged in a straight line as shown in Figure 3A. However, the tear-arresting holes 140 can be arranged in a curved, sinusoidal, zig-zag (as shown in Figure 3B) or random distribution in the substrate 120.

[0055] The size of each tear-arresting hole 140 in the substrate 120 may be the same. In other embodiments, the tear-arresting holes 140 in the substrate 120 of the document 100 have an increasing or decreasing size from a first hole, as shown in Figures 4A and 4B. In an alternative embodiment, the sizes of the tear-arresting holes in the substrate vary in a random manner.

[0056] The tear-arresting holes 140 can be straight through the substrate 120 of the document 100 or could be at an angle relative to the substrate 120. As shown in Figure 5A, a depth through each of tear-arresting hole 140 can substantially parallel to a normal to a surface of the substrate 120. When the substrate 120 with the tear- arresting holes 140 is covered by a coating, the holes in this configuration will be visible when the document 100 is viewed from the front with a light source positioned directly behind the tear-arresting hole 140 with the viewing and illumination directions are generally normal to a surface of the substrate 120.

[0057] According to an alternative embodiment, as shown in Figures 5B and 5C, a depth through each of the tear-arresting holes 140 is at an angle to a normal to a surface of the substrate 120 of the document 100. Preferably, each tear-arresting hole 140 is at an angle from about 0° to about 80°, and preferably between about 0° to about 60°, to the normal to the surface of the substrate 120. When the substrate 120 with the tear-arresting holes 140 is covered by a coating, the tear-arresting holes 140 in this configuration would not be visible when the viewing and illumination directions of the document 100 are normal to the surface of the substrate 120. In contrast to the configuration shown in Figure 5A, the tear-arresting holes 140 in the configuration shown in Figures 5B and 5C will only be visible when the document 100 is tilted relative to the illumination and viewing directions.

[0058] In the configuration shown in Figures 5A to 5C, the opening area of a tear- arresting hole 140 on a top surface of the substrate is shown to be the same as the opening area of the tear-arresting hole on an opposite bottom surface of the substrate. In other configurations (not shown), a tear-arresting hole may have an opening area on one surface of the substrate that is different (smaller or larger) from an opening area of the hole on the opposite surface of the substrate. By way of example, a diameter or width of the tear-arresting gap through the substrate increases or decreases from a surface of the substrate the tear-arresting gap. In that example, the gap may be conical or frustoconical, or have a substantially trapezoidal shape.

[0059] A substrate 120 having a plurality of tear-arresting holes 140 can have a combination of holes with different angles through the substrate. For example, the substrate may have tear-arresting holes 140 shown in Figure 5A, tear-arresting holes 140 shown in Figure 5B and/or tear-arresting holes 140 shown in Figure 5C. In this configuration, not all of the tear-arresting holes will be visible to a viewer at any one viewing angle of the document.

[0060] Where the document is a banknote that is provided with a security feature, embodiments of the present invention will have negligible or only minimal impact on the security feature used to authenticate banknotes. The tear-arresting holes can be configured or arranged such that the tear-arresting holes will not be visible unless the document is viewed from a particular angle. The holes may be part of an existing design in the artwork on the document, so as not to be obtrusive and so as to not compromise the ability to authenticate the document. [0061 ] The present invention additionally provides a method of manufacturing a polymeric-based document comprising: providing a substrate and providing tear- arresting holes in the substrate, wherein the tear-arresting holes inhibit or mitigate the propagation of a tear through any one of the tear arresting holes. The holes are configured or arranged to terminate a propagation of a tear that propagates in the substrate towards the any one of the tear-arresting holes. Embodiments of the present invention provide minimal impact and require no major changes to existing banknote production processes, except for the additional step of producing the tear- arresting holes.

[0062] Preferred embodiments of the invention have been described by way of example only and modifications may be made thereto without departing from the scope of the invention.

[0063] Other modifications and embodiments include those described in the Summary of the Invention section.