Patent Application
20200001638
The present invention relates to a method of forming a security document, in particular forming a security document containing personalised information.
To prevent counterfeiting and to enable authenticity to be checked, security documents are typically provided with one or more security devices which are difficult or impossible to replicate accurately with commonly available means such as photocopiers, scanners or commercial printers. “Personalised” security documents containing unique security devices add an extra layer of security; however, producing a large number of unique security devices which to embed in finished security documents is both expensive and time consuming.
One well known type of security device is one which uses a colour shifting element to produce an optically variable effect that is difficult to counterfeit. Such a colour shifting element generates a coloured appearance which changes dependent on the viewing angle. Examples of known colour shifting structures include photonic crystals, liquid crystals, interference pigments, pearlescent pigments, structured interference materials or thin film interference structures including Bragg stacks.
It is also known in the art that the optical effect produced by a colour shifting element can be modified by introducing a film comprising a surface relief over the colour shifting element, wherein the surface relief modifies the angle of light incident to, and reflected from, the colour shifting element so as to provide a different optical effect to the viewer. For example, such an additional “light control” layer may produce colour shifting effects which are visible closer to a normal angle of viewing with respect to the device, and may enable more colours to be viewed on tilting the device as compared to the colour shifting element in isolation.
As discussed, it is known in the art how to produce and control colour shifting elements for use in security devices. However, it is desirable to provide a new method of forming a security document which utilises the effects of colour shifting elements, but which also enables efficient personalisation of the security document.
In accordance with a first aspect of the present invention, there is provided a method of forming a security document, comprising: (i) providing a security document substrate, the security document substrate comprising a security device comprising a colour shifting element and a light control layer covering at least a part of the colour shifting element, wherein the light control layer has a surface structure comprising one or more elevations and depressions that modifies the angle of light from the colour shifting element to generate a first optical effect, and; (ii) selectively modifying a part of the light control layer so as to generate a second optical effect different from the first optical effect.
In addressing the problems discussed above in relation to providing personalisation of a security document, or providing a unique security document, we have realised that we can utilise the three-dimensional nature of the surface structure of a light control layer in order to control the characteristics of a security device comprising such a light control layer once it is already integrated into a security document substrate. For example, the method allows a number of security document substrates to be individually personalised by selectively modifying the light control layer of the integrated security device rather than having to individually produce a large number of different security devices which have to be subsequently integrated into security document substrates.
The expression “colour shifting element” is used to refer to any material which can selectively reflect or transmit incident light to create an optically variable effect, in particular an angularly dependent coloured reflection or transmission. Examples of such a colour shifting element include photonic crystals, liquid crystals, interference pigments, pearlescent pigments, structured interference materials or thin film interference structures including Bragg stacks.
In general the colour shifting element may be substantially opaque or partially transparent. A partially transparent colour shifting element (for example a layer of cholesteric liquid crystal material) transmits at least some of the light that is incident upon it as well as providing an optical effect in reflection. An example of a substantially opaque colour shifting element is an optically variable pigment. Optically variable pigments having a colour shift between two distinct colours, with the colour shift being dependent on the viewing angle, are well known. The production of these pigments, their use and their characteristic features are described in, inter-alia, U.S. Pat. Nos. 4,434,010, 5,059,245, 5,084,351, U.S. Pat. Nos. 5,135,812, 5,171,363, 5,571,624, EP-A-0341002, EP-A-0736073, EP-A-668329, EP-A-0741170 and EP-A-1114102. Optically variable pigments having a viewing angle-dependent shift of colour are based on a stack of superposed thin-film layers with different optical characteristics. The hue, the amount of colour-shifting and the chromaticity of such thin-film structures depend inter alia on the material constituting the layers, the sequence and the number of layers, the layer thickness, as well as on the production process. Generally, optically variable pigments comprise an opaque totally reflecting layer, a dielectric layer of a low refractive index material (i.e. with an index of refraction of 1.65 or less) deposited on top of the opaque layer and a semi-transparent partially reflecting layer applied on the dielectric layer.
The security device may be viewed in reflection or transmission. If the device (and therefore the security document) is intended to be viewed in reflection and comprises a partially transparent colour shifting element, it is preferable that the security device further comprises an absorbing element positioned on a distal side of the colour shifting element with respect to the light control layer (i.e. such that the colour shifting element is positioned between the light-absorbing element and the viewer) and operable to at least partially absorb light transmitted through the colour shifting element. This is because the colour shifting element will only reflect certain wavelengths of light. Therefore, the presence of a light-absorbing element under the colour shifting element absorbs light that is transmitted through the colour shifting element and ensures that light reflected from the colour shifting element dominates. In the case where a substantially opaque colour shifting element is used, such an absorbing element is not required.
The light control layer preferably comprises a microprismatic structure, wherein the microprismatic structure comprises a plurality of microprisms. Without the presence of the light control layer, light reflected from the colour shifting element would be refracted at the interface between the colour shifting element and the air, due to the difference in refractive indices between the two. The microprismatic structure of the light control layer means that the interface between the light control layer and the air is angled with respect to the colour shifting element, thereby modifying the angle of light from the colour shifting element, giving rise to the first optical effect that is different to the optical effect that would be exhibited by the colour shifting element in isolation. As an example, a cholesteric liquid crystal colour shifting material in isolation may provide a red to green colour shift effect when tilted. However, when a microprismatic light control layer is provided over such a light control element, a red to blue colour shift effect (with a green colour exhibited at an intermediary viewing angle between red and blue) is exhibited to the user as blue light reflected from the colour shifting material is no longer totally internally reflected (see
Here “tilting” is used to mean a change in viewing angle of the security document by tilting the document about an axis in the plane of the document. Typically the change in viewing angle is from a normal angle of viewing to a non-normal angle of viewing.
The microprismatic structure may comprise an array of linear microprisms. In one embodiment, the microprismatic structure comprises two or more arrays of linear micro prisms, wherein the long axes of one array are angularly offset from the axes of the other array. This provides a rotational optical effect as well as the colour shifting effect dependent on a tilt angle of the security document, wherein the rotational effect is dependent on the azimuthal angle of viewing with respect to the arrays of linear micro prisms. The optical effect due to the presence of a microprism array will be more readily observed when the device is viewed in an azimuthal direction perpendicular to the long axes of the array rather than in an azimuthal direction parallel to the long axes of the array.
Other forms of microprismatic structures are envisaged, for example structures comprising microprisms having an asymmetrical structure or a repeating faceted structure.
The microprismatic structures described above are referred to as one dimensional structures, as the modification of the light reflected from the colour shifting element is primarily observed in one rotational viewing direction with respect to an individual micro prism, typically perpendicular to the long axis of the microprism. However, a light control layer comprising a two dimensional structure is also envisaged wherein the optical effect due to the presence of the microprismatic structure is readily observed at two or more rotational viewing directions. Examples of such a two-dimensional microprismatic structure include corner cubes and pyramidal structures. The light control layer may alternatively comprise a lenticular array having a curved surface structure.
The pitch of the surface structure of the light control layer (e.g. the width of a microprism) is preferably in the range of 1-100 μm, more preferably 5-70 μm, and the height of the surface structure (e.g. the height of a microprism) is preferably in the range of 1-100 μm, more preferably 5-40 μm.
Step (ii) of the first aspect of the invention comprises selectively modifying a part of the light control layer so as to generate a second optical effect different from the first optical effect. As explained above, the presence of a light control layer covering at least a part of the colour shifting element provides a different optical effect to a viewer than if the colour shifting element were present in isolation.
The fact that the light control layer has a surface structure comprising one or more elevations and depressions allows for easy modification of the surface structure in order to provide personalisation to the security document. It is important to note that when the selective modification is carried out, it is the security document substrate as a whole that is being modified, as the security device is integrated within the security document substrate. For example, it is envisaged that a plurality of passport security page substrates may be provided. Each of the provided substrates comprises a security device with the same light control layer and therefore exhibits the (same) first optical effect. By selectively modifying the light control layers present on each substrate, each finished passport security page will comprise unique personalised information. The unique personalised information is revealed to the viewer due the second optical effect exhibited by the modified part of the light control layer being different to the first optical effect.
Preferably, at least at one viewing angle, the first optical effect exhibits a first colour, and the second optical effect exhibits a second colour different from the first colour. This means that the part(s) of the light control layer that were selectively modified exhibit a different colour from the non-modified parts(s) when the finished security document is tilted, and therefore the modified part(s) stand out to the user in a memorable manner. This difference in optical effect advantageously allows indicia to be introduced to the security device of the security document through the selective modification of the light control layer. Such indicia may include biometric data relating to a passport holder (for example an image of the passport holder) or a serial number in a security label.
The second optical effect may be the optical effect generated by the colour shifting element in the absence of a light control layer. In other words, the part(s) of the light control layer that are modified are effectively made “non-functional” such that they have negligible effect on the light from the colour shifting element. In the example above where the first optical effect is a red to blue colour shift, modifying a part of the light control layer such that the second optical effect is the optical effect generated by the colour shifting element in the absence of a light control layer would provide for a red to green colour shift in the modified “non-functional” part(s) of the light control layer. If the light control layer were to be modified in such a manner so as to define indicia, the finished security document, upon tilting, would exhibit green coloured indicia against a blue background.
If the light control layer is selectively modified such that the modified “non-functional” part(s) of the light control layer are on a scale that is not perceptible (i.e. resolvable) to the naked human eye (typically less than 150 μm, preferably less than 100 μm and even more preferably less than 70 μm), then the resulting optical effect exhibited to the viewer by the modified light control layer will be a combination of the first and second optical effects. This is typically experienced as a “mixing” of the colours produced by the first and second optical effects exhibited by adjacent modified and unmodified parts of the light control layer. Dependent on the ratio of the modified and non-modified part(s) of the light control, different colours may be seen upon tilting due to the combination of the first and second optical effects. Therefore modifying the light control layer of a security document substrate in such a manner advantageously provides an alternative or complimentary means of producing personalised, unique security document.
The selectively modifying may comprise introducing a material to a part of the light control layer. Typically, the material is introduced into at least one depression in the surface structure of the light control layer, for example into a region located between microprisms of a microprismatic structure. The introduction of a material to a part of the light control layer modifies the light control layer at that part and therefore modifies the effect that the light control layer has on light from the colour shifting element, creating a second optical effect. By adding material in such a manner, the second optical effect can be applied to an area of the security device relating to indicia, for example an image or a serial number.
Typically, the material added to the light control layer has a refractive index substantially the same as that of the light control layer. This enables regions of the light control layer to be “blanked out” and made non-functional such that the second optical effect is the same as the optical effect if there were no light control layer present. In other words, the optical effect generated by the “blanked out” regions is the same as the optical effect generated solely by the colour shifting element. In order that the modified part(s) of the light control layer provide the same optical effect as the colour shifting element in isolation, the material is added such that the light control layer at the modified part comprises a planar region having a planar surface substantially parallel with the colour shifting element. However, it is envisaged that material having a different refractive index may be added to the light control layer in order to generate different optical effects.
Preferably, the material is a printable resin, and can be selectively introduced to a part of the light control layer by digital printing. The digital printing may be ink jet printing or laser printing for example. This feature of the invention is particularly advantageous. For example, a passport manufacturer may be provided with a security document substrate with a security device comprising a colour shifting element and a light control layer already integrated into the security document substrate. The passport manufacturer may then personalise each passport by digitally printing, onto the light control layer of the security device, material that modifies the light control layer such that the printed areas containing material generate a second optical effect different from the “original” first optical effect. For example, biometric data relating to the owner of the passport may be printed onto the security device in order to personalise the passport.
This is particularly beneficial as the personalisation can be carried out as a final step in the production of the passport (or other security documents such as identity cards or driving licenses), rather than a security device manufacturer having to produce a large number of unique individualised security devices for subsequent integration into security documents.
Digital printing advantageously allows for high spatial accuracy in the modification of the light control layer, thereby providing the ability to create indicia with high levels of detail that are difficult to counterfeit and yet relatively straightforward to produce.
Examples of materials that may be added to the light control layer in order to selectively modify it include UV curable inkjet inks such as Mimaki® UV ink Clear 031-38U069C. Other suitable materials for UV curable inkjet include polyfunctional terminally unsaturated organic compounds including the polyesters of ethylenically unsaturated acids such as acrylic acid and methacrylic acid and a polyhydric alcohol. Examples of some of these polyfunctional compounds are the polyacrylates and polymethacrylates of trimethylolpropane, pentaerythritol, dipentaerythritol, ethylene glycol, triethylene glycol, propylene glycol, glycerin, sorbitol, neopentylglycol, 1,6-hexanediol and hydroxy-terminated polyesters, hydroxy-terminated epoxy resins, and hydroxy-terminated polyurethanes. Also included in this group of terminally unsaturated organic compounds are polyallyl and polyvinyl compounds such as diallyl phthalate and tetraallyloxyethane and divinyl adipate, butane divinyl ether and divinylbenzene.
In a further example, the material added to the light control layer may be a varnish, which may be a water based varnish or a UV curable varnish. The varnish may be typically applied by one of flexographic, lithographic or screen printing. Suitable UV curable materials may comprise a resin which may typically be of one of two types, namely:
a) Free radical cure resins, which are typically unsaturated resins or monomers, pre-polymers, oligomers and the like containing vinyl or acrylate unsaturation for example, and which cross-link through use of a photo initiator activated by the radiation source employed, for example UV radiation.
b) Cationic cure resins, in which ring opening (e.g. epoxy types) is effected using photo initiators or catalysts which generate ionic entities under the radiation source employed, for example UV radiation. The ring opening is followed by intermolecular cross-linking.
The radiation used to effect curing is typically UV radiation but could comprise electron beam, visible, or even infra-red or higher wavelength radiation, depending upon the material, its absorbance and the process used. Examples of suitable curable materials include UV curable acrylic based clear embossing lacquers or those based on other compounds such as nitro-cellulose. A suitable UV curable lacquer is the product UVF-203 from Kingfisher Ink Limited or photopolymer NOA61 available from Norland Products. Inc., New Jersey.
The curable material could be elastomeric and therefore of increased flexibility. An example of a suitable elastomeric curable material is aliphatic urethane acrylate (with suitable cross-linking additive such as polyaziridine).
Suitable water based varnishes include include vinyl resins such as UCAR™ VMCA Solution Vinyl Resin or UCAR™ VCMH Solution Vinyl Resin, both of which are supplied by The Dow Chemical Company and which are carboxy-functional terpolymers comprised of vinyl chloride, vinyl acetate and maleic acid. Varnishes including polyurethane resins are also suitable.
The invention may be particularly advantageous in the production of bank notes containing a security thread for example. In this case, the security thread acts as a security device, and may be produced as a “blank” security thread, where the light control layer covers the entirety of the colour shifting element such that the entirety of the security thread exhibits the same first optical effect. A bank note substrate having such a “blank” security thread integrated therein may be provided and the bank note substrate subsequently personalised by adding varnish in a pattern conforming to desired security indicia. This is particularly advantageous as the application of a varnish is typically the last step in bank note production. A further benefit is that it is conventionally difficult to ensure that any indicia on a bank note thread are in register with their respective window regions on the substrate. The present invention allows for simple registration of such indicia by simply applying varnish at the desired locations.
Alternatively or in addition to the addition of material to the light control layer, the selectively modifying may include removing at least a part of the light control layer such that no light control layer is present at that part of the security device. In a similar manner to the addition of material, removing at least a part of the light control layer modifies the optical effect produced by the modified part(s) of the security device. For example, at least one elevation of the surface structure of the light control layer may be removed such that, at that part of the security device, no light control layer is present, meaning the optical effect provided by part of the security document is the optical effect generated by the colour shifting element in isolation. In the case where the light control layer comprises a microprismatic structure, selected microprisms may be removed for example. By removing part(s) of the light control layer in accordance with desired indicia, the security document can be personalised in a similar manner to that described above in relation to the addition of material.
The selective modification may comprise deforming at least a part of the light control layer. Here the term “deforming” means changing the structure of the light control layer. Typically in this instance, at least one elevation of the surface of the light control layer is deformed so as to form a planar region of the light control layer such that the second optical effect at that region of the security document is the optical effect generated by the colour shifting element in the absence of a light control layer. The planar region is substantially parallel with the plane of the colour shifting element.
Typically, in the case where the selective modification of the light control layer includes removing or deforming at least a part of the light control layer, the light control layer is a heat transformable material, and in such a case, the removal or deformation of at least a part of the light control layer comprises applying heat energy to the heat transformable material. This is typically done using a radiation source such as a laser through a laser ablation process, or by applying heat energy through thermal conduction with an applied member such as a linear or rotary embossing die in a so-called “hot-embossing” process. Such an embossing die will comprise a surface relief corresponding to the desired modification of the light control layer.
In a similar manner to digital printing, the use of a laser or embossing die allows accurate and fast modification of the light control layer so as to define indicia, allowing for fast easy and efficient personalisation of security documents.
It is envisaged that the three forms of selectively modifying the light control layer described above (the addition of material, the removal of a part of the light control layer and the deforming of a part of the light control layer) may be applied either individually or in combination.
As described above, the selective modification may be carried out so as to define a pattern related to the security document. For increased security, this may be a pattern unique to the security document. As an example, the light control layer may be selectively modified so as to define biometric data related to the security document owner, such as finger print data or an image of the owner. This is particularly appealing in the field of passports where, for example, in a “post-processing” process, an image of the passport holder can be introduced into a security device integrated within a passport security page substrate by selectively modifying regions of the light control layer so as to define the image.
The method is particularly beneficial when a “blank” security device (i.e. where each security device comprises the same light control layer) is integrated into a number of security document substrates, and the selective modification of the device (which is already integrated into the security document substrate) is performed as one of the final steps in the production of the finished security document.
The light control layer typically comprises a polymer (examples of which have been outlined above in the discussion of materials that may be added to the light control layer), and may be formed by a number of different processes including embossing, extrusion and cast curing. In the case of a bank note thread for example, such a polymer light control layer may be formed by forming a layer of UV curable polymer over a colour shifting material and subsequently embossing and UV curing the polymer to form the desired surface structure. In the case of a security sheet for a passport, such a security sheet is typically formed from a laminar structure made up of a plurality of planar polymer layers. The colour shifting element may be introduced into the laminar structure either before the laminating process, or afterwards through the use of a “plug” as is known in the art. The light control layer may then be formed in the top surface of the security sheet substrate, for example by embossing. In such an instance, the colour shifting element and the light control layer form the security device integrated within the security page substrate.
As described above, a particularly advantageous implementation of the present invention is where the light control layer is selectively modified so as to define a pattern related to the security document. This may be biometric data related to the owner of the security document, or a serial number on a security label for example. The pattern may be unique to the security document. As will be appreciated, by supplying a security document substrate which already comprises a security device, and then selectively modifying the light control layer of the security device (and therefore modifying the security document substrate itself), the present invention allows for efficient production of unique security documents.
The light control layer may be selectively modified so as to define first and second regions of the light control layer, wherein the first and second regions provide different optical effects. Typically just regions will be exhibited as areas of different colour when the finished security document is tilted.
The method may further comprise the step of performing at least one finishing process, for example a cutting, stacking or batching process.
The present invention may be directed to a number of different security documents, including passports, banknotes, security labels, identification cards, driving licenses or any other documents of value. The present invention allows for efficient personalisation of such security documents with difficult to counterfeit, unique security devices.
In accordance with a second aspect of the invention, there is provided a security document formed by the method of the first aspect of the invention.
Preferably, the light control layer of the security document is selectively modified to define indicia unique to the security document. As described above, this may be biometric data related to a passport owner, where the biometric data is defined on a security page of the passport. As a further example, the security device may be a security thread integrated with the security document substrate, wherein the security document substrate has on at least one surface at least one windowed region in which the thread is exposed at the substrate surface, and at least one region in which the thread is not exposed, and wherein; the light control layer is selectively modified so as to define indicia on the security thread. This is particularly beneficial in banknote production, but may also be applied to other documents of value such as passports. The scenario where the security device is a security thread integrated within the security document substrate is a particularly advantageous example of the invention as subsequent selective modification of the light control layer on the security thread allows for ease of registration of indicia or motifs with the windowed region(s) on the substrate. This will be described in further detail in the detailed description below.
Examples of the present invention will now be described with reference to the attached drawings, in which:
When light strikes the colour shifting element 10, some of the light is reflected. The wavelength of the reflected light depends on the structure and composition of the colour shifting material 10 and the reflected light will appear coloured to the viewer 50. The wavelength of the reflected light is also dependent on the angle of incidence, which results in a colour change perceived by the viewer 50 as the colour shift layer is tilted relative to the viewer.
The optical effects of the colour shifting element 10 are illustrated schematically in
The colour shifting element 10 can be viewed either in reflection or transmission. In the case of viewing in reflection, it is desirable to place a dark absorbing layer (shown at 12) beneath the colour shifting element 10 in order to absorb the transmitted light. This is particularly beneficial if the colour shifting element is partially transparent to visible light (for example a cholesteric liquid crystal layer). If a substantially opaque colour shifting element (such as a printed ink comprising an optically variable pigment) is used, such an absorbing layer 12 is not required.
The light modification properties of the light control layer are most noticeable when the device is viewed in a direction perpendicular to the long axes of the microprisms of the light control layer.
Preferably the resin 30 has a refractive index substantially identical to that of the light control layer 20 such that the modified part of the light control layer 20 takes the form of an optically homogenous planar layer. This means that the light reflected from the colour shifting element 10 is not significantly refracted by the modified part of the light control layer 20 and the viewer 50 therefore perceives a colour shifting effect substantially the same as if the light control layer were not present at that part. For example, at the modified part of the light control layer, blue light from the colour shifting element will be totally internally reflected at the interface between the resin 30 and the air such that a red to green colour shift will be exhibited to the viewer rather than a red to blue colour shift. Therefore such a modified part of the light control layer may be described as “non-functional”.
The security page substrate 200 comprises opposing outer layers 201, 209 and a plurality of interior layers 203, 205 and 207. In this example, a colour shifting element 10 is provided on second interior layer 205 and an absorbing layer 12 is provided below and in register with the colour shifting element on third interior layer 207. Here “in register” means that the colour shifting element and absorbing element are substantially aligned in a direction normal to the layers (i.e. overlapping) and in the same relative positions in a plurality of security page substrates. A light control structure 220 is provided above and in register with the colour shifting element 10, and extends through the top outer layer 201 and first internal layer 203 such that the light control structure 220 is substantially adjacent the colour shifting element 10 and takes the form of a layer directly above the colour shifting element 10. In other examples, the light control structure and the colour shifting element may be spaced apart by one or more regions of transparent material (such as transparent polycarbonate) such that the colour shifting element is visible through the light control structure. In this example the light control structure 220 extends through the top outer layer 201 and the first internal layer 203. However, in other examples, the light control structure may extend through only the top outer layer, or through more than one internal layer depending on the construction of the security page substrate and positioning of the colour shifting element.
The colour shifting element 10 and absorbing layer 12 may be provided on their respective layers prior to the fusing step, or may be inserted as a “plug” into the substrate after the layers have been fused together, as is known in the art.
The light control structure 220 comprises a microprismatic structure comprising an array of linear symmetrical triangular microprisms 220a, 220b, 220c, 220d and 220e defining a series of elevations 226 and depressions 228. The long axes of the microprisms extend into the plane of the page. Typically, the light control structure 220 is formed by a hot embossing process, where the initially planar layers 201 and 203 are brought into intimate contact with a heated embossing cylinder or die, the surface of which comprises a series of elevations and depressions corresponding to the desired microprismatic structure.
Together, the colour shifting element 10 and the light control structure 220 define a security device embedded within the passport security page substrate 200.
Typically the opposing outer layers 201 and 209 are substantially transparent, as well as the first internal layer 203. Internal layers 205 and 207 are typically substantially opaque. The topmost outer layer 201 and the first internal layer 203 are substantially transparent such that the colour shifting element 10 is visible through the top of the passport security page substrate. However, first internal layer 203 may alternatively be substantially opaque and comprise a window region in register with the colour shifting element 10 such that the colour shifting element 10 is visible through the topmost outer layer 201.
As described with reference to
Advantageously, this allows the resin 302 to be introduced to the light control structure 220 so as to define indicia on the finished passport security page 210, wherein the indicia are viewable upon tilting of the passport page such that the different optical effects are exhibited. For example, in the case of a passport security page, the indicia may be biometric data related to the holder of the passport, such as a portrait of the passport holder, as schematically illustrated in
The above description therefore describes how a “blank” passport security page substrate 200 may be provided that is then personalised in order to generate a unique finished security page 210 containing personal biometric data in the form of a difficult to counterfeit security device 250. Here the term “blank” is used to describe the manner in which each passport security page comprises a “blank” security device comprising an unmodified light control layer. In other words, the security device in each blank security page substrate will exhibit the same colour shifting effect. However, as described above, upon modification of the blank substrate, a finished security page 210 is produced, including a unique security device.
It is envisaged that this modification of the security page substrate 200 may be one of the final processing steps in the production of the passport security page. Advantageously, being able to modify the security page substrate 200 as a single entity prevents the requirement for a plurality of separate individual security devices to be manufactured, logged, and inserted into the correct documents.
In the case of a security page substrate comprising a plurality of polycarbonate layers as described above, a portrait may be laser marked into one of the layers in a manner as is known in the art, and the light control layer subsequently modified in order to provide a portrait matching the laser marking that is visible upon tilting of the security page.
Therefore, in the modified regions 402, 404 of the light control structure 220, light reflected from the colour shifting element 20 will exhibit the same optical effect as if the light control layer were not present, i.e. a red to green colour shift.
Alternatively, instead of removing part(s) of the light control layer 20, the light control layer 20 may be selectively deformed in order to leave a planar region of light control layer substantially abutting the colour shifting element so as to effectively define a gap region 402, 404 as above.
This technique can be used to obtain the same effect as described above in relation to
Although the
Furthermore, it is envisaged that the modification of the light control structure 220 may comprise a combination of two or more of the introduction of a resin, the removal of at least a part of the light control layer and the deforming of at least a part of the light control structure.
The above description in relation to
A colour shifting element 10 is positioned on second interior layer 603 immediately below and in register with the light control structure 620. However, as described above, the colour shifting element and light control structure may be spaced apart by one or more layers comprising substantially transparent regions. An absorbing element 12 is located on third interior layer 604 immediately below and in register with the light control structure. Typically, layers 601, 602 and 607 are substantially transparent, with the remainder of the layers substantially opaque. However, as with the passport security page example, the first interior layer 602 may be substantially opaque and comprise a window region in register with the colour shifting element such that the colour shifting element 10 is visible through the light control structure 620.
Together, the colour shifting element 10 and the light control structure 620 define a security device embedded within the security laminate 600.
In the case of the security laminate 600, fourth interior layer 605 may comprise a tamper-evident element (not shown), and the fifth interior layer 606 may comprise an adhesive (not shown) such that, upon removal of outer layer 607, the security laminate 600 may be attached to an item of value.
Such modification is schematically illustrated in
The present invention is particularly beneficial for producing security labels, which are inherently difficult to secure. For example, a batch of “blank” security label substrates may be provided to a manufacturer who wishes to provide a secure security label to each manufactured product. Each “blank” security label substrate contains a colour shifting element and a light control structure defining a blank security device. The goods manufacturer may then use inkjet printing to print a unique security code onto the light control structure integrated within the security label substrate. Therefore, each finished security label will comprise a unique security code that is visible upon tilting due to the different optical effects exhibited to the viewer by the modified and unmodified parts of the light control structure, thereby adding a further element of security to the label in addition to the code (which typically would be printed in a conventional manner and easy to replicate).
The present invention also has particular application in bank note production.
In
A significant security benefit would be gained if indicia on a windowed security thread could be positioned in register with the windowed areas. To date, such registration capability remains impractical since current production processes do not permit threads to be registered to achieve these desired effects. Instead, an arbitrary offset occurs between the bridge positions and thread design, giving rise to ill-centred or incomplete images in the window. Not surprisingly attempts have been made to adjust the relative position of the thread to the window during the paper making process. Most notably trials have been undertaken to adjust the tension on the thread-feed during the paper making process. These have experimented with a closed loop feedback architecture, where a control signal is derived from an image capture system monitoring a selected window position. However, in practice, this approach has proved to be particularly difficult to implement, and little success has been achieved for anything other than particularly narrow threads. The desire to achieve registration between images upon threads and the windows of the substrate remains strong. Most broadly, the goal is to find a method to facilitate the arbitrary positioning of images and motifs relative to the thread window, or (if required) the positioning of arbitrary and differing designs in each window. Furthermore an additional challenge is faced in that, in practice, such a method would need to integrate readily with the normal established processes of security document production, not least since such processes are required to meet the most exacting of production standards. It is standard practice/known in the security industry that unprinted banknote paper can be supplied to State Print works/other commercial printers as a substrate to print on. This substrate regularly contains finished security threads. An advantage of the current invention described is that it allows the personalisation/finishing of the security thread by the banknote printer thus enabling the banknote printer to customise the security thread. The customisation may take place before or after the banknote paper is printed with the conventional banknote printing operations and in addition to the indicia being in register to the windows the indicia can also be register to the conventional banknote print design.
The present invention provides a solution to this problem, as will be explained below.
The light control layer 720 comprises a microprismatic structure comprising a plurality of linear microprisms 720a, 720b, 720c . . . defining a plurality of elevations (shown generally at 726) and depressions (shown generally at 728). The long axes of the microprisms extend into the plane of the paper.
There are a number of ways of manufacturing and applying the light control layer 720 to the thread 701. In a first method, an all over UV curable resin coating is applied to the colour shifting element 712. The colour shifting element 712, with the UV curable resin coating thereon, is then held in intimate contact with a production tool in the form of an embossing cylinder, wherein the microprismatic structure defined on the production tool is replicated in the resin. UV light is used at the point of contact to cure and harden the resin. Ideally, the production tool is transparent (e.g. made from quartz) and a UV light is positioned inside so that the resin is cured immediately after being cast.
Alternatively, the light control layer may be formed on a carrier layer using the method described above and then transferred with the carrier layer in a separate process such that the carrier layer is adjacent the colour shifting element 712. Alternatively the colour shifting element may be introduced and adhered to the light control layer formed in such a manner.
In an alternative method, the light control layer 720 is formed by coating the colour shifting element 712 with a thermoplastic embossing lacquer and then using an embossing tool to create the light control layer with the application of heat and pressure.
The bank note thread 701 illustrated in
A “blank” bank note substrate 700 is illustrated in
The final step in the production of a bank note is typically the application of a varnish over the entirety of the bank note. By “varnish” we mean a polymeric resin, which is typically clear. Advantageously therefore, the varnish in such a finishing step may be applied to the blank bank note substrate 700 in order to modify the light control layer 720 on the exposed areas of thread in the windowed regions 702. The varnish may be applied to the light control layer 720 in the same manner as described above in relation to
The use of varnish as described above takes advantage of a typical bank note production process. However, the light control layer may be modified by the use of digital printing as described in relation to
As will be appreciated by the person skilled in the art, a security thread may be used as a security device in security documents other than bank notes, for example in passports.
The examples above have each been described with a light control layer comprising a microprismatic structure comprising a plurality of linear microprisms.
Opposing end faces of an individual microprism are substantially parallel, and such a microprism is known as a “one-dimensional” microprism. The microprismatic structure 820 shown in
The optical effect exhibited by the light control layer is therefore anisotropic. If the device is rotated within its plane, the exhibited optical effect is seen most readily when the device is tilted with the viewing direction perpendicular to the long axes of the microprisms (i.e. along Y-Y′). If the device is rotated such that the viewing direction is parallel with the long axes of the microprisms (i.e. along X-X′), the effect is seen to a lesser extent.
A variety of different light control layers can be selectively modified according to the invention in order to provide a variety of memorable optical effects to a viewer that are difficult to counterfeit, as will be highlighted with reference to the following
Therefore, if a security device having a light control layer comprising a microprismatic structure having offset microprisms is provided within a security document substrate, selective modification of such a light control layer can provide a number of different effects upon tilting and rotation of the security document substrate. It is envisaged that light control layers having a plurality of regions offset from each other can be used, as shown in
The light control layer may comprises a series of multi-faceted microprisms (i.e. having more than two facets), as shown in the example light control layer 1220 of
To obtain more isotropy in the optical properties of the security device, a “two-dimensional” microprismatic structure may be used comprising microprisms that are not as rotationally dependent as the linear microprisms of
A security document substrate can be provided comprising a security device with a colour shifting element and a light control layer as described above in relation to
In the examples described above, the security device comprises a light control layer that covers substantially the entirety of the colour shifting element. However, it is envisaged that a security device integrated within a security document substrate may be provided where the light control layer covers only a part of the colour shifting element. This may allow for more efficient generation of indicia through modification of the light control layer if, for example, the uncovered part of the colour shifting element defines a large part of a desired indicia that is common to each of the subsequently personalised security documents.
An example method of creating a security document using the present invention can be summarised in the flow chart of
The colour shifting element and/or the complete security device can either be formed directly within the security document substrate (e.g. as part of a laminate layer of an identification substrate) or may be supplied as part of a security article, such as a security thread, strip or patch, which can then be applied to or incorporated into such a document.
At step 1602 a part of the blank security device is selectively modified. More specifically, a part of the light control layer of the security device is selectively modified. As described above, the selective modification may be performed by one or more of: introducing a material to the light control layer, removing a part of the light control layer, and deforming a part of the light control layer. The selective modification is typically performed in order to define indicia upon the security device that is visible upon tilting of the security device due to the differing optical effects provided by the modified and unmodified parts of the security device. It is envisaged that the security document manufacturer, upon receiving the plurality of security document substrates each comprising a blank security device, may selectively modify the security devices in order to provide a plurality of unique, personalised security documents. For example, the blank security devices may be selectively modified in order to define unique biometric data relating to the holder of each passport.
At step 1603 the process finished with the final “finishing” processes being applied to the security documents, including cutting, stacking and batching processes.
As described above, personalised security documents may be produced by selectively modifying a “blank” light control layer of a “blank” security device within a security document substrate. Examples of such substrates that may be selectively modified will now be described with reference to
The opacifying layers 2103a and 2103b are omitted across an area 2101 which forms a window within which the blank security device 100 is located. As shown best in the cross-section of
In
A further example is shown in
In the examples of
| Number | Date | Country | Kind |
|---|---|---|---|
| 1701795.5 | Feb 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2018/050279 | 1/31/2018 | WO | 00 |
