AU2018244647A1

AU2018244647A1 - Security documents and methods of manufacture therefor

Info

Publication number: AU2018244647A1
Application number: AU2018244647A
Authority: AU
Inventors: Alan KEEN
Original assignee: De la Rue International Ltd
Current assignee: De la Rue International Ltd
Priority date: 2017-03-28
Filing date: 2018-03-28
Publication date: 2019-09-19
Also published as: GB201704963D0; GB2562868A; GB201804974D0; WO2018178662A1; MX2019010734A; EP3600905A1

Abstract

Disclosed herein is a security document comprising: an at least semi- transparent substrate (302, 402) having opposed first and second sides; a first print working (304, 404) in contact with or above a first side of the substrate; and at least one opacifying layer (306, 406) disposed in contact with or above the first side of the substrate so that it at least partially overlays the first print working; wherein any opacifying layer that is disposed across 50% or more of the substrate is disposed in contact with or above the first side of the substrate, such that when the security document is viewed from the second side of the substrate, at least a portion of the first print working is visible against the background of the said at least one opacifying layer disposed in contact with or above the first side of the substrate.

Description

SECURITY DOCUMENTS AND METHODS OF MANUFACTURE THEREFOR

Field

Embodiments of the present invention relate generally to security documents for securing value or proving identity such as banknotes, cheques, passports, identity cards, driver’s licences, and the like. More particularly, an improved security document structure and manufacturing method are provided which offer a quick, efficient and accurate means of producing security documents.

Background

Historically, security documents such as banknotes, cheques, passports, identification documents, certificates and licences have been manufactured using paper, card or the like. Typically, these documents have been constructed by printing on both sides of a single layer of a paper or card substrate.

These documents are frequently the target of counterfeiters and persons wishing to make fraudulent copies thereof and/or changes to any data contained therein. Typically such documents are provided with a number of visible security devices for checking the authenticity of the object. Examples of such security devices include complex printed patterns, security inks and structural features, such as holograms, lenticular devices and moire interference devices. Common to all such devices is that the visual effect exhibited by the device is extremely difficult, or impossible, to copy using available reproduction techniques such as photocopying.

More recently, multi-layer security documents have been introduced, often incorporating polymer substrates. Such multi-layered security documents are known, for example, from PCT/GB2016/052999, PCT/GB2016/052997, and WO 98/13211. Here, double-sided security documents that comprise a transparent polymer substrate are disclosed, to both sides of the substrate are applied a

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PCT/GB2018/050813 plurality of print workings, transparent and opacifying layers, and security devices.

As will be readily seen from these examples, multi-layered security documents have allowed the development of security documents and security devices with increasingly complicated visual appearances and internal structures. This has resulted in a corresponding increase in the complexity of manufacturing multilayered security documents.

In particular, known methods of manufacturing multi-layer documents are slow, expensive and require large, complex machinery. Furthermore, it is often difficult to register the separate layers, print workings and security devices to one another within a multi-layer document.

There is a need for security documents which may be manufactured easily, quickly and accurately.

Statement of invention

According to a first aspect of the invention there is provided a security document comprising: an at least semi-transparent substrate having opposed first and second sides; a first print working in contact with or above a first side of the substrate; and at least one opacifying layer disposed in contact with or above the first side of the substrate so that it at least partially overlays the first print working; wherein any opacifying layer that is disposed across 50% or more of the substrate is disposed in contact with or above the first side of the substrate, such that when the security document is viewed from the second side of the substrate, at least a portion of the first print working is visible against the background of the said at least one opacifying layer disposed in contact with or above the first side of the substrate.

Thus, no opacifying layers which are disposed across the majority of the surface of the substrate are applied in contact with or above the second side of the

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PCT/GB2018/050813 substrate. It shall be understood that the phrase ‘any opacifying layer that is disposed across 50% or more of the surface of the substrate’ refers to any opacifying layer which extends over, covers or obscures 50% or more of the surface area of a side of the substrate. Where the opacifying layers form a discontinuous pattern, graphic or indicia of regions of an at least semitransparent material or coating, it is understood that this refers to the cumulative coverage or area over which the opacifying layer is applied.

For instance, there may be no opacifying layers disposed in contact with or above the second side of the substrate. Alternatively, security document embodiments may comprise opacifying layers disposed in contact with or above the second side of the substrate wherein the opacifying layer does not cover the majority (i.e. 50% or more) of the substrate. In preferred embodiments, any opacifying layer that is disposed across 50% or more of the security document is disposed in contact with or above the first side of the substrate

By ‘visible’ it is understood that the respective feature is visible to the naked eye. As such, the print working may absorb, refract, scatter reflect or emit visible light. Consequently, the visible first print working discussed above provides a significant visual impact and is readily observed from at least the second side of the device.

Furthermore, the term visible is not intended to relate to materials or features which do not impose a significant visual impact on the appearance of the finished security document. Consequently, the terms visible print workings and/or visible layers used herein are not intended to cover substantially transparent and/or colourless print workings or layers. Although these workings or layers may have a minor effect on transmitted and reflected light, they are not easily observed by the naked eye within the finished security document and are therefore considered to be non-visible.

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In alternative embodiments the print workings may comprise luminescent, phosphorescent or iridescent inks, or inks that are visible in at least a portion of the ultraviolet (UV) or infrared (IR) ranges.

Herein, it is understood that the phrase ‘above a side of the substrate’ indicates that a print working, layer or other feature is located above that side of the substrate when the side is facing up. There may be one or more intermediate layers between the print working and the substrate.

In conventional methods of manufacturing security documents an opacifying layer which extends across substantially the whole document is applied to each side of the document’s substrate. Each of the opacifying layers is then printed with one or more print workings which will be visible against the background of the respective underlying opacifying layer. This is sometimes referred to as ‘double sided printing’.

Using these conventional double sided printing techniques it is difficult to register the opacifying layers and print workings which are applied to the opposing sides of a security device. Specifically, inconsistencies caused by rotating the substrate, or between the relative positions of the machinery used to apply the layers and print workings to the opposing sides of the substrate, mean that it is difficult to achieve an accurate correspondence between the components on the opposing sides of the device. Therefore, it is difficult to register the visual appearances of the opposing sides of the document.

Accordingly, the inventors have recognised that documents where a first print working is applied above or in contact with an at least semi-transparent substrate and overlaid by at least one opacifying layer offers significant benefits over these conventional printing processes.

In particular, workings and layers which are applied to the same side of a substrate may be much more easily registered to one another. Consequently, the first print working may be closely registered with the at least one opacifying

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PCT/GB2018/050813 layer which overlays it as they are both applied in contact with or above the first side of the substrate. Furthermore, any additional print workings or layers which are applied in contact with or above the first side of the substrate (e.g. over or above the first print working or the at least one opacifying layer) may also be closely registered to these components.

Consequently, in documents according to the present invention the workings and layers seen from each side of the document may be accurately registered. This allows the creation of documents with increasingly complex visual appearances which are more difficult for would-be counterfeiters to replicate.

Specifically, the inventors have found that a registration of no more than approximately 250 pm may be achieved between layers or print workings applied to opposing sides of a substrate. Whilst a registration to an accuracy of approximately 100 pm or better is possible between multiple layers and print workings applied to one side of the substrate.

Additionally, the security of documents created using the printing techniques discussed above is further improved because the first print working is protected by the substrate. By positioning any markings, indicia or personal information between the substrate and the at least one opacifying layer it becomes significantly more difficult for would-be counterfeiters to tamper or change any of these visual features. Whilst a similar effect might be produced in conventional double sided printing by providing additional protective layers, the “single sided” printing methods described above achieves this improvement in security without the need for any additional materials or machinery.

Finally, documents which have the same visual appearance as conventional security documents may be achieved with a reduced number of opacifying layers. Rather than applying a separate opacifying layer to each side of a document’s substrate, only one opacifying layer must be applied to the first side of the security document (although more than one opacifying layer may be applied to create documents which are more visually complex or more secure as

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PCT/GB2018/050813 discussed below). Consequently, there is a reduction in the materials, machinery and costs required to manufacture traditional security documents.

In further embodiments, all visible print workings are disposed in contact with or above the first side of the substrate.

Thus, security documents in accordance with these embodiments are manufactured using a single sided printing process, where all visible print workings are applied to or above a first side of the substrate, whereby at least the first print working is visible from the second side of the substrate.

In particular, from the second side of the substrate the first print working is visible through the at least semi-transparent substrate against the background of the at least one opacifying layers. Any regions of the first print working not overlaid by the at least one opacifying layer will be visible from the first side of the substrate.

As discussed above, in these embodiments all visible print workings are applied to or above a single side of the substrate of a security document only. This differs from conventional methods of manufacturing security documents, where double sided printing techniques are typically used. In these conventional techniques print workings are applied to both sides of the substrate of a security document.

The inventors have recognised that documents where all visible print workings are applied to a single side of the substrate offer a number of significant improvements over known double sided printed documents.

Firstly, applying all visible print workings to a single side of the substrate enables the production of documents which exhibit a more complex visual appearance and are more difficult to counterfeit. This is because using conventional double sided printing techniques it is difficult to register the layers and print workings applied to the opposing sides of a security device. Specifically, inconsistencies

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PCT/GB2018/050813 caused by rotating the substrate, or between the positioning of the two sets of machinery applying the print workings to the opposing sides of the substrate, mean that it is difficult to achieve an accurate correspondence between the components on the opposing sides of the device.

In contrast, single sided printing techniques, where visible print workings are only applied to or above one side of a substrate, do not require a change in the orientation in the substrate or the printing machinery. This allows a more accurate registration to be achieved between a documents layers and print workings. Specifically, the inventors have found that a registration accuracy of approximately 100 pm or better is possible between layers and print workings which are applied to one side of a substrate. Advantageously this increase in the registration accuracy allows the creation of security documents which have more complex visual appearances and are more difficult for would-be counterfeiters to imitate.

Furthermore, this “single sided printing” (i.e. applying all visible print workings to or above one side of the substrate) is quicker, easier and more efficient than double sided printing (where visible print workings are applied to both sides) as there is no need to either rotate a substrate during manufacture, or to provide machinery which can apply print workings or layers to both sides of the substrate without changing its orientation. As a result, single sided printing requires fewer, simpler machines and a more compact assembly line.

Alternatively, one or more print workings may be applied in contact with or above the second side of the substrate. When the document is viewed from the second side of the substrate these print workings will be visible against the first print working and the at least one opacifying layer. Such print workings may include printed opacifying layers which are disposed across less than 50% of the surface of the substrate.

In further embodiments, all visible layers (printed or otherwise provided) are disposed in contact with or above the first side of the substrate.

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Advantageously this allows a highly accurate registration to be achieved between all visible print workings and visible layers within the security document. This enables the design of security documents exhibiting increasingly sophisticated visual appearances and comprising complex security devices. Furthermore, by applying all visible layers and workings to a single side of the substrate of a document the manufacturing process is significantly simplified as there is no need to change the orientation of the document’s substrate during manufacture or any printing and assembly machinery.

Preferably, at least one second print working is disposed in contact with or above the opacifying layer furthest from the substrate.

As such, from the first side of the substrate at least a portion of the second print working may be visible against the background of the opacifying layer. As a result, the appearance of the second print working may visually contrast with the appearance of the opacifying layer, allowing any markings, patterns or indicia defined by the print working to be readily observed.

Advantageously, applying a second print working over the opacifying layer allows the creation of security documents with increasingly complex visual appearances. In particular, in regions of the device where the opacifying layer is applied the first print working will only be visible from the second side of the substrate, and the second print working (if present) will only be visible from the first side of the substrate.

In other words, by applying a first print working below the opacifying layer and a second print working above the opacifying layer, the visual appearances of the first and second sides of the device are decoupled in the regions of the device where the opacifying layer is provided. This allows different graphical designs to be visible from opposing sides of the security document. This is achieved with increased registration accuracy in comparison to known techniques, because all of the visible print workings are applied to one side of the document’s substrate.

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Alternatively, the visual appearance of both sides of the security document may be created using only the first print working and the opacifying layer, as discussed above.

Preferably, the substrate is formed of a substantially visually transparent and preferably colourless material.

Alternatively, the substrate may be semi-transparent or translucent, allowing light but not detailed shapes to be seen through it. In further embodiments the substrate may have a coloured tint or shade.

By transparent and translucent it is understood that at least some wavelengths of incident visible light will be transmitted through the material, i.e. that the material is optically clear. Hence, such layers reflect or absorb negligible amounts of visible wavelengths of light. Where the substrate material is translucent it is understood that the light may be optically scattered. In each case, preferably the first print working may be readily observed from the second side of the substrate.

Advantageously, the transparent or translucent material comprising the at least semi-transparent substrate will have an optical density no greater than 1, more preferably no greater than 0.6, still preferably less than or equal to 0.3 (optical density is a dimensionless quantity on a logarithmic scale; an optical density of 1 corresponds to 10% transmission). In further preferable embodiments, the substrate transmits more than 40% of incident light.

A colourless material will transmit light of all visible wavelengths equally. However, substrates with a coloured tint will be formed where the material of the substrate absorbs rather than transmits or reflects incident light of a specific wavelength or range of wavelengths corresponding to the colour that will be observed.

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The benefits of providing a substrate formed of a substantially visually transparent or colourless material is that the print workings and/or layers applied on one side of the substrate may be easily from the opposite side of the substrate. As a result, all of the visible workings or layers which are applied to the first side of the substrate below the opacifying layer(s) (including at least the first print working) may be observed from the second side of the substrate against the background of the opacifying layer(s) without any change to their visual appearance.

Preferably, the substrate comprises a plastic material, such as: polyethylene terephalate (PET), biaxially orientated polypropylene (BOPP), polycarbonate (PC), polyvinylchloride (PVC), polybutlylene terephalate (PBT), nylon or acrylic.

The benefits of plastics or polymers are that they are durable, waterproof, strong, tear resistant, and easily recyclable. In other embodiments, the substrate may be formed of alternative materials such as resin, paper or glass.

Furthermore, the use of transparent and colourless materials such as the plastics listed above allows for an increase in the range of security devices which can be incorporated within security documents. These may include windows, half-windows and Venetian blind style devices.

Preferably the substrate comprises a single layer. However, in alternative preferable embodiments the substrate is multi-layered.

A monolithic substrate comprising a single layer of material is quick, easy and cheap to manufacture. However, providing a multi-layered substrate allows for the creation of increasingly complex structures. In particular, a wide variety of layers with different visual or material properties may be incorporated into the substrate. For instance, a layer may be coloured or contain a visible or nonvisible additive such as a coloured or fluorescent additive, or it may be formed of a conductive material to form an anti-static layer. These layers may be held together by heat and/or adhesive.

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In further embodiments of the invention the substrate is formed of a conductive material. However, in equally preferable embodiments, the security document comprises a substantially transparent conductive layer, wherein the conductive layer is disposed in contact with or above the second side of the substrate.

By providing a substrate or layer which is formed of a conductive material, static electrical charge which might otherwise be built up upon the security document during manufacture or use is dissipated. By preventing the build up of static charge, the security documents will not stick together then they are manipulated (e.g. when counting banknotes) is reduced, the documents will not accumulate less dust, and sparks or electrical shocks are prevented. Furthermore, the resistivity of the substrate or conductive layer may be measured during manufacture and offers an easy means of testing quality assurance purposes.

Alternatively, where the substrate is multi-layered, it may comprise at least one conductive layer. Preferably the at least one conductive layer is the layer on the outside of the substrate, i.e. a side of the conductive layer is the side of the multi-layered substrate.

Preferably, the first and/or second print workings comprise at least one item of information comprising any of: indicia, alphanumeric text, a letter or number, a symbol, a portrait, a logo or another graphic.

In further preferable embodiments the first and/or second print workings include any of: security prints, guilloches, microtext, and repeating geometric patterns. Such complex workings are difficult for would-be counterfeiters to reproduce.

Preferably, the first and/or second print workings are formed by one of: gravure, flexographic, lithographic or intaglio printing. Gravure printing is considered to be particularly suitable for the implementations discussed herein given the high accuracy and good registration between workings that may be achieved using this method. Alternatively any other suitable printing method may be used.

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In preferred embodiments the first and/or second print workings comprise a plurality of component print workings, wherein preferably each of the plurality of component print workings is a different colour or tone. By applying the print workings using a series of component colour workings, i.e. RGB or CMYK workings a wide variety of different colours and different visual appearances may be achieved. Alternatively, the manufacture of the document may be simplified if a single working of a single colour or monotone is used.

Preferably, one or more opacifying layers comprise an opaque, translucent or semi-opaque material. In some embodiments multiple translucent or semiopaque opacifying layers may be applied over one another in order to create a combined layer which is sufficiently or substantially visually opaque.

By opaque or semi-opaque it is understood that each opacifying layer absorbs, scatters or reflects incident visible light. Where an opacifying layer is translucent it is understood that light transmitted through the opacifying layer is optically scattered. Advantageously, the opacifying layer preferably transmits less than 30% of incident visible light in a single pass, more preferably less than 20%, still preferably less than 10%, most preferably is substantially opaque.

In other words, each individual opacifying layer may have an optical density in the range 0.1 to 0.5, more preferably 0.1 to 0.4, most preferably 0.1 to 0.3 (as measured on a transmission densitometer, with an aperture area equivalent to that of a circle with a 1mm diameter - a suitable transmission densitometer is the MacBeth TD932).

The opacifying layers may or may not be of the same composition as one another - for example, in some preferred cases at least one of the opacifying layers will contain electrically conductive particles (desirable to reduce the effects of static charge), whereas others will not - but nonetheless, preferably, all of the opacifying layers are substantially the same colour as one another, most preferably a light and bright colour such as white (including off-white) or

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PCT/GB2018/050813 grey. In preferred implementations, the opacifying layers each have a brightness L* in CIE L*a*b* colour space of at least 70, preferably at least 80 and more preferably at least 90.

In regions of the document where the opacifying layers are applied the first print working will only be visible from the second side of the substrate, and the second print working (if present) will only be visible from the first side of the substrate. In other words, although the first and second print workings are applied to the same side of the substrate, the visual appearances of the first and second side of the document are decoupled by the opacifying layer or layers. Hence the use of at least one opacifying layer allows different graphical designs to be visible from opposing sides of the security document.

Preferably one or more opacifying layers comprise an ink or coating preferably comprising a white or grey pigment. However, in alternative preferred embodiments, one or more opacifying layers comprise a polymeric, non-fibrous, light-scattering material.

By using an ink comprising white or grey pigments or a polymeric, non-fibrous, light-scattering material, opacifying layers with a constant visual appearance and a light, neutral colour may be achieved. In both cases, the opacifying layer(s) may be printed onto the document in as a visible print working. Against the optically static background provided by any opacifying layers any further print workings or security devices will be easily observed. In other words, the print workings and security devices will be readily visible or stand out against these opacifying layers.

Preferably one or more opacifying layer are disposed across at least 50% of the substrate, preferably across at least 75% of the substrate, more preferably across at least 90% of the substrate, still more preferably across at least 95% of the substrate.

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In some cases, the one or more opacifying layers extend across the entirety of the substrate, such that the first print working is not visible from the first side of the device. Consequently, the first print working will not be visible from the first side of the device as it will be obscured by the opacifying layer, whilst the second print working will not be visible from the second side of the device. Advantageously, the appearance of each side of the security document will not be affected by any graphic designs or patterns applied to the reverse or opposing side.

In further preferred embodiments, any opacifying layer that is disposed across 75% or more of the substrate is disposed in contact with or above the first side of the substrate, preferably wherein any opacifying layer that is disposed across 90% or more of the surface of the substrate is disposed in contact with or above the first side of the substrate.

Preferably, any opacifying layer that is disposed across 75% or more of the security document is disposed in contact with or above the first side of the substrate, more preferably any opacifying layer that is disposed across 90% or more of the security document is disposed in contact with or above the first side of the substrate.

In particularly preferred embodiments, one or more opacifying layers define one or more transparent windows.

Preferably in these embodiments the one or more transparent windows are defined by the boundary of the one or more opacifying layers or by a region of substantially transparent material within the one or more opacifying layers.

Advantageously, a transparent window provides a visually verifiable security feature which cannot be reproduced by simple copying methods e.g. photocopying. However, additionally the provision of transparent windows within the opacifying layer allows the creation of complex security devices which are extremely difficult for would-be counterfeiters to imitate.

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In particularly preferred embodiments, within the at least one transparent window respective portions of the first and/or second print workings are visible from both sides of the security document. This allows the print workings to be arranged closely adjacent or overlapping one another.

Alternatively, the security document may have a first transparent window within which the first print working is visible from both sides of the document, and a second transparent window spaced from the first within which the second print working is visible from both sides of the document. In further embodiments exhibiting complex visual effects, the first and/or second print workings may be symmetric along at least one axis, and/or be registered to one another in the area of the document corresponding to a window.

Preferably the security document further comprises a transparent varnish layer, wherein the transparent varnish preferably comprises a matting additive. This varnish layer may be applied in contact with or above the first and/or second sides of the substrate. In alternative preferred embodiments, the transparent varnish layer is applied to one or more of the external (i.e. outermost) surfaces of the security document.

In further embodiments, a transparent varnish may also be applied in contact with or above one or more sides of the substrate. This varnish may comprise a matting additive to reduce the gloss of the security document, i.e. the varnish will reduce the amount of light reflected by the surfaces of the document’s layers. Additionally, the varnish may optimise that when the documents are stacked together they do not stick together. In other words, the varnish will help prevent the security documents from sticking together when stacked or manipulated.

In particularly preferred embodiments, the security document further comprises at least one security device, wherein all of the security devices are disposed in contact with or above the first side of the substrate, and wherein the at least one security device preferably comprise one or more of: microtext; fine line patterns;

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PCT/GB2018/050813 latent images; Venetian blind devices; lenticular devices; moire interference devices; moire magnification devices; holograms; diffractive gratings; watermarks; embossings; perforations; or the use of one or more colour-shifting, iridescent, luminescent or fluorescent inks.

Preferably, at least a portion of a first security device is visible from at least one side of the substrate within a transparent window defined by one or more opacifying layers. The transparent window may by defined by the boundary of the one or more opacifying layers or by a region of substantially transparent material within the layers.

For instance, a security device may be visible from both sides of the substrate within a transparent window in a single opacifying layer. Alternatively, the security device may be positioned between two opacifying layers, wherein only one of the opacifying layers defines a window. In such an embodiment the opacifying layers will form a ‘half-window’ and the security device will only be visible from the side of the substrate that corresponds to the opacifying layer which contains the transparent window.

In further embodiments the security device may be positioned between two opacifying layers without transparent windows. Accordingly, the security device may be obscured when viewed in reflection and may only be visible in transmission.

Alternatively or additionally, the security document may comprise at least one security article, wherein all of the security articles are disposed in contact with or above the first side of the substrate, and wherein the at least one security article preferably comprise a security thread, strip, foil, insert, transfer element, label or patch.

Preferably at least a portion of a first security article is visible from at least one side of the substrate within a transparent window defined by one or more opacifying layers. The transparent window may by defined by the boundary of

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PCT/GB2018/050813 the one or more opacifying layers or by a region of substantially transparent material within the layers.

For instance, a security article may be visible from both sides of the substrate within a transparent window in a single opacifying layer. Alternatively, the security article may be positioned between two opacifying layers, wherein only one of the opacifying layers defines a window. In such an embodiment the opacifying layers will form a ‘half-window’ and the security device will only be visible from the side of the substrate that corresponds to the opacifying layer which contains the transparent window.

In further embodiments the security device may be positioned between two opacifying layers without transparent windows. Accordingly, the security device may only be visible in transmission, may be machine readable or comprise a machine readable code (e.g. a magnetic strip or thread).

Advantageously, security devices and articles applied in contact with or above the first side of the substrate may be carefully registered with visible print workings and layers applied to the first side of the substrate and do not require the substrate to be rotated during manufacture. Additionally, locating security devices and articles within transparent windows documents with increasingly complex visual appearances may be created. Whilst it is difficult for would-be counterfeiters to tamper with these components as they may be are located between a substrate and an opacifying layer. Consequently, security documents in accordance with these embodiments offer significant security, registration accuracy and manufacturing efficiency benefits.

In alternative embodiments, the security device or security article may be placed within the substrate, or in contact with or above the second side of the substrate. This is preferably where a unitary or self-contained security device or security article is applied to the substrate as a preliminary step before any print workings or layers are applied, or to the security document a final step after all other workings or layers are formed, but this is not essential.

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Preferably the security document is a banknote, cheque, page or sheet of a passport, identity card, bank card, driver’s licence, certificate of authenticity, fiscal stamp or other document for securing value or personal identity.

In particularly preferred embodiments the security document is a finished document of value suitable to be issued to the public and/or used to identify the bearer or securing value. Alternatively, the assemblies and documents discussed herein may be used as a component in the manufacture of further security documents.

According to a second aspect of the invention there is provided a method of manufacturing a security document, a security document comprises an at least semi-transparent substrate having opposed first and second sides, the method comprising the steps of:

(a) printing a first print working in contact with or above a first side of the substrate; and (b) applying an opacifying layer in contact with or above the first side of the substrate so that it at least partially overlays the first print working;

wherein any opacifying layer that is disposed across 50% or more of the substrate is disposed in contact with or above the first side of the substrate of the substrate, such that, when the security document is viewed from the second side of the substrate, at least a portion of the first print working is visible against the background of the said at least one opacifying layer disposed in contact with or above the first side of the substrate.

In common with the first aspect of the invention, a security document with a document sided visual appearance is produced wherein all visible print workings are applied to one side of the substrate (i.e. a single sided printing technique is used). Specifically, a first print working is applied in contact with or above a first side of the at least semi-transparent substrate and an opacifying layer is applied

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PCT/GB2018/050813 in contact with or above a first side of the substrate such that it at least partially overlaps the first print working.

In the second aspect of the invention, the security document could be a security document in accordance with the first aspect of the invention, or any embodiment discussed above, but this is not essential.

In preferred embodiments, any opacifying layer that is disposed across 50% or more of the security document is disposed in contact with or above the first side of the substrate

As discussed above, by applying all visible print workings in contact with or above the first side of the substrate of the substrate significant benefits are realised over conventional double sided printing techniques. Specifically, methods in accordance with the invention achieve documents with a higher registration between their component visual workings and layers, thus enabling the production of more complicated documents which are more difficult to counterfeit. Further, single sided printing provides documents which are more difficult to forge because of the protection offered to the first print working by the substrate. Finally, the production of documents using single sided printing requires less machinery and is quicker, simpler and less costly than double sided printing.

In preferable embodiments the documents are manufactured using a web fed process or a sheet fed process, or a method that comprises web fed and sheet fed processes.

Web fed processes and systems, which use a continuous substrate running through the machines or presses, are very fast in comparison to sheet fed methods and are therefore particularly suitable for the production of high volumes of security documents. Whereas sheet fed process typically offer higher accuracy and the systems may be more easily adapted to produce a variety of security document sizes and formats.

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Web fed and sheet fed processes may be combined within a single manufacturing method. For instance, a continuous substrate may first be printed in a web fed process before it is divided into separate sheets for sheet fed printing. This allows efficient printing of security documents as print workings which do not require the higher accuracy provided by sheet printing may be quickly and efficiently printed using web fed printing processes, whilst print workings which must be highly accurate may be applied using sheet fed printing processes.

The division of the substrate web may be performed using the processes of “slitting” and “sheeting”, as described in the applicant’s publication WO2017/009616. In “slitting” the web is cut or divided longitudinally, i.e. in the direction of travel of the web. Whilst, in “sheeting” the web is cut or divided laterally, i.e. perpendicular to the direction of travel of the web. Preferably the web is first slit and then sheeted, however this is not essential. Each resulting substrate sheet may be divided further in order to achieve the finished security document either before or after any sheet printing process.

Preferably the security document further comprises a substantially transparent conductive layer, wherein the conductive layer is disposed in contact with or above the second side of the substrate, or is the exterior layer on the second side of a multi-layered substrate. In particularly preferred embodiments where the security document includes a conductive layer disposed in contact with or above the second side of the substrate, the substantially transparent conductive layer is applied to the substrate prior to the printing of the print workings or the application of the opacifying layer. In this way the combined substrateconductive layer assembly may be printed using a single-sided printing technique as discussed in reference to the substrates above.

Brief description of drawings

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Examples of security documents and methods for their manufacture will now be described with reference to the accompanying drawings, in which:Figure 1(a) depicts a conventional system for manufacturing a security document;

Figure 1(b) depicts another conventional system for manufacturing a security document;

Figure 1(c) depicts in cross-section a system configured to implement a method for manufacturing a security document in accordance with an embodiment of the present invention;

Figure 2(a) depicts another conventional system for manufacturing a security document;

Figure 2(b) depicts in cross section a system configured to implement a method for manufacturing a security document in accordance with an embodiment of the present invention;

Figure 3 depicts a first embodiment of a security document in cross-section;

Figure 4 depicts a second embodiment of a security document in cross-section; and

Figure 5 depicts a third embodiment of a security document in an exploded perspective view.

Detailed description

Figures 1(a), (b) and (c) illustrate schematically three system layouts 10, 20, 30 for manufacturing a security document. Figures 1(a) and 1(b) show systems configured to implement known double sided printing methods for manufacturing

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PCT/GB2018/050813 security documents where visible print workings are applied to both sides of a document’s substrate. Whilst Figure 1(c) illustrates schematically a system configured to implement a single sided printing method in accordance with the present invention where visible print workings are applied in contact with or above one side of the substrate only.

Figure 1(a) shows double sided printing technique where visible print workings are applied to both sides of a document’s substrate. A continuous horizontal web of substrate 12 moves in direction Di. The substrate has two opposing sides 12a, 12b. The first side 12a is the upper surface of the web, whilst the second side 12b is the lower surface of the web.

A plurality of print stations 14 are located in contact with or adjacent to the first side of the substrate web, whilst a plurality of print stations 16 (only one shown) are located in contact with or adjacent to the second side of the substrate web. At each print station 14, 16 one or more print workings or layers are applied to the surfaces of the substrate.

In the arrangement shown in Figure 1(a), two print stations 14 are located above the web, i.e. adjacent or over the first side 12a of the substrate 12, and are configured to apply one or more visible print workings to the first side 12a of the substrate. One print station 16 is located below the web, i.e. adjacent or over the second side 12b of the substrate 12, and is configured to apply one or more visible print workings to the second side 12b of the substrate.

The print stations 14, 16 apply visible print workings to the two opposing sides 12a, 12b of the substrate 12 in sequence. Alternatively, the print stations may be arranged such that they are able to simultaneously apply visible print workings or visible layers to the two opposing sides of a substrate simultaneously.

However, when using this process it is difficult to accurately locate or align the print station(s) located on one side of the web relative to the print station(s) on

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PCT/GB2018/050813 the opposing side of the web. Consequently, it is difficult to achieve an accurate, or close, registration between the print workings and layers applied to the opposing sides of the substrate.

Figure 1(b) shows a system capable of implementing an alternative double sided printing technique. Again, a continuous web of substrate 22 comprising two opposing sides 22a, 22b moves in direction Di. As shown, the length and width of the web extend in a horizontal plane, such that initially the first side 22a of the substrate is the upper surface of the web, whilst the second side 22b is the lower surface of the web.

The system comprises two pluralities 24, 26 of print stations which are located on the same side of the web. Print stations 24 apply print workings and/or layers to the first side 22a of the substrate 22. Print stations 26 apply print workings and/or layers to the second side 22b.

In more detail, the web first passes through print stations 24, which apply one or more visible print workings to the first side 22a of the substrate 22.

Once the required print workings and/or layers are applied to the first side of the substrate, the web is flipped or turned, as shown at section 28. Specifically, the substrate 22 is rotated by approximately 180° degrees around the direction of travel Di, such that the second side 22b of the substrate 22 faces upwards and the second side 22a faces downwards. This is typically performed by rollers (not shown) in contact with the web. Alternatively, the web may be turned as a whole between two separate print processes. In other words, after a substrate web passes entirely through a set of print stations which print on a first side of the web, the web may be rotated or flipped and fed through the same or different stations configured to print onto the second side of the substrate.

Following this change in orientation, one or more visible print workings are applied to the second side of the substrate 22b by print station 26.

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Hence, this process may be used to produce a security document where visible print workings and/or visible layers are applied to both sides 12a, 12b of the substrate 12. However, the rotation or flipping of the substrate web during the process results in inconsistencies in the location of the web. Therefore it is again difficult to achieve a consistently accurate, or close, registration between the print workings and layers applied to the opposing sides of the substrate.

In contrast, Figure 1(c) illustrates schematically a system arrangement capable of implementing a single sided printing process for the production of a security document where all visible print workings are applied to one side of the document’s substrate, according to the present invention

Once again, a continuous web of substrate 32 comprising two opposing sides 32a, 32b moves in direction Di. As shown, the length and width of the web extend in a horizontal plane, such that initially the first side 32a of the substrate is the upper surface of the web, whilst the second side 32b is the lower surface of the web. However, any orientation of the web is possible. The substrate 32 may be self-supporting, passing through the system without any supporting or carrier layers, however, this is not essential. If the substrate is not selfsupporting it may be formed on a carrier feed web.

A plurality of print stations 34 configured to apply at least one print workings and at least one opacifying layer to the substrate 32 are provided. All of these print stations are located on one side of the web. For instance, as shown in Figure 1(c), all print stations 34 may be located above a horizontal substrate web, so that they are all over or adjacent to the first side 32a of the substrate 32. The print stations may be configured to apply a variety of print workings or layers using any suitable application technique. For instance, each print station may comprise at least one gravure printer, flexographic printer, lithographic printer or intaglio printer.

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The workings and layers applied by the print stations 34 include a first print working and at least one opacifying layer. These are applied in contact with or above the first side of the substrate.

In further embodiments, the print stations 34 may apply a variety of further print workings and layers to the first side 32a of the substrate 32. These include a plurality of visible print workings and/or visible layers. However, notably no print workings or layers are applied to the second side 32b of the substrate 32. Consequently, no opacifying layers which are disposed across more than 50% of the substrate 32 are applied to the second side 32b of the substrate 32.

Advantageously, because all of the print stations 34 are located on the same side of the substrate web, and all print workings and layers are applied to the same side of the substrate (i.e. the first side 32a) there is no change in the orientation of the web between the print stations and a highly accurate registration may be achieved between the workings or layers applied. Furthermore, the system is simple and compact as there is no need to provide print stations on each side of the web, or any mechanism to flip or rotate the web.

Furthermore, as shown in Figure 1(c), all visible print workings are applied to only one side of a substrate in order to achieve a highly accurate registration between the visible print workings. However, in further embodiments additional non-visible print workings and/or layers may be applied in contact with or above the second side 32b of the substrate 32.

These “non-visible” print workings and layers are defined herein to be workings or layers that do not significantly impact the visual appearance of the visible workings and/or visible layers applied on or above the first side of the substrate in a final security document. In other words, the non-visible workings or layers must not substantially affect the visible light transmitted through the document.

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For instance, a print working above the first side of the substrate will still be visible from the second side of the substrate if a substantially visually transparent layer is applied in contact with or above the second side of the substrate. This is because negligible amounts of visible light are reflected or absorbed by this layer.

Although Figure 1(c) shows a web-fed process, in alternative embodiments of the invention the security documents are produced using sheet-fed printing methods. In such an embodiment, all print workings and/or layers are applied to one side of a sheet of substrate. This avoids the need to rotate or flip each sheet between the application of visible print workings or layers to the opposing sides of the substrate, as occurs in conventional double-sided sheet-fed printing of security documents.

In the conventional examples discussed in reference to Figures 1(a) and 1(b), all of the steps described are web-based processes, i.e. layers and print workings are applied to a web of the polymer substrate 12, e.g. in one in-line process. Typically a web with a large width (e.g. between 0.75 and 1.5 m) is supplied for this purpose. However, for some process steps it is desirable to reduce the width of the web, e.g. so that shorter (and hence less costly) processing tools can be used. It is also desirable to carry out certain process steps on individual sheets of the material, rather than on a continuous web. This is particularly the case for the first and second print workings as opposed to the opacifying coatings.

In particularly preferable embodiments of the present invention, security documents are produced using a combination of web fed and sheet fed process steps.

For instance, in some embodiments, at least a first print working and an opacifying layer are applied using web based processes. These print workings and opacifying layers are applied in contact with or above one side of a polymer substrate web with a large width (e.g. between 0.75 and 1.5 m). The web is then

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PCT/GB2018/050813 divided into sheets for sheet fed printing whereby at least a second print working is applied in contact with or above a side of the substrate.

Converting a web substrate to a sheet substrate (i.e. dividing the web into sheets) may involve slitting the initial web along its longitudinal direction so as to reduce its width, subsequent processing steps utilising processing tools of correspondingly shorter width compared with those of the preceding steps. The slit webs are then converted in sheets by cutting it along its cross direction at intervals spaced in the longitudinal direction. This process is sometimes referred to as “sheeting”. Each sheet will preferably be sized so as carry a plurality of the final security documents. Subsequent printing processes are performed using sheet-fed machinery.

Figure 2(a) depicts a comparative system 40 for manufacturing a security document.

The system 40 comprises a continuous web of substrate 42 comprising two opposing sides 42a, 42b which moves in direction Di. As shown, the length and width of the web extend in a horizontal plane, such that the first side 42a of the substrate is the upper surface of the web, whilst the second side 42b is the lower surface of the web.

The system further comprises two print stations 44, 46 positioned on opposing sides of the substrate. Print station 44 applies an opacifying layer 43 to the first side 42a of the substrate 42. Whilst print station 46 applies an opacifying layer 45 to the second side 42b of the substrate.

Alternatively, a similar assembly may be achieved by applying an opacifying layer to the first side of a substrate using a first print station, rotating the substrate web, and applying a second opacifying layer to the second side of the substrate using the first print station or an alternative print station located on the same side of the web as the first station.

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Subsequently, a first plurality of visible print workings are applied to or above the first opacifying layer 43 and a second plurality of visible print workings are applied to or above the second opacifying layer 45 (not shown). These steps are typically carried out using a sheet fed process. Consequently, a security document with two visually different sides is achieved as from the first side 42a of the substrate 42 a first plurality of print workings will be seen against the background of opacifying layer 43, whilst from the second side 42b of the substrate 42 a second plurality of print workings will be seen against the background of opacifying layer 45.

However, it is difficult to achieve an accurate registration between each plurality of print workings and its respective opacifying layer as these are applied in separate process steps. Good registration between the opacifying layers and the overlying print workings is particularly difficult to achieve if the print workings are applied after the substrate web has been divided into sheets i.e. using sheet fed print methods. It is also difficult using these conventional techniques to achieve an accurate registration between the print workings and opacifying layers applied to the opposing sides 42a, 42b of the substrate 42.

In contrast, Figure 2(b) depicts in cross section a system 50 configured to implement a method for manufacturing a security document in accordance with an embodiment of the present invention.

The system 50 comprises a continuous web of at least semi-transparent substrate 52 comprising two opposing sides 52a, 52b which moves in direction Di. As shown, the length and width of the web extend in a horizontal plane, such that the first side 52a of the substrate is the upper surface of the web, whilst the second side 52b is the lower surface of the web. However, any orientation of the web is possible. Preferably the substrate 52 is self-supporting. However, this is not essential. If the substrate is not self-supporting it may be formed on a carrier feed web.

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As shown, a first print station 54a applies a first visible print working to the first side of the substrate 52 (not shown). Subsequently, a second print station 54b applies an opacifying layer 53 to the first side 52a substrate 52, such that the opacifying layer 53 at least partially overlays the first print working.

When viewed from the second side 52b of the substrate 52, the first print working is visible through the at least semi-transparent substrate 52 against the background of the opacifying layer, 53. Furthermore, the first print working is registered to the opacifying layer 53 with a high accuracy and, being located between the substrate 52 and the opacifying layer 53 is protected from tampering.

Subsequently, further print workings may be applied in contact with or above either side 52a, 52b of the substrate 52 (not shown). This allows the creation of security documents with a similar visual appearance to those produced using the system 40 of Figure 2(a) but using a single opacifying layer (although in preferable embodiments multiple opacifying layers may be overlaid, this may be used to achieve a region of a security document exhibiting a substantially opaque visual appearance). Hence the materials, space and cost required to produce security documents may be reduced.

The application of the further print workings may be performed by either further web fed printing processes or using sheet fed processes following the division of the web into suitable sheets. The preparation of sheets for a sheet fed printing process may comprise one or more of “slitting” (where the web parallel to the direction of travel) or “sheeting” (where the web is cut perpendicular to the direction of travel). The resulting sheets may be divided further before or after printing in order to produce the final security documents as required.

In particularly preferred embodiments, the first print working and the opacifying layer 53 are applied by gravure printing technique using a web fed process, thus achieving a highly accurate registration between the first print working and at least one opacifying layer. Subsequently, the web is divided into sheets

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PCT/GB2018/050813 (typically by splitting and sheeting the web) and a second printed working is applied over the opacifying layer 53 using a sheet fed process by lithographic or intaglio printing techniques.

The properties of the layers and workings within the security documents according to the present invention will now be discussed with reference to Figures 3 to 5.

Figure 3 shows a cross section of a security document 300 in accordance with the present invention. The security document comprises an at least semitransparent substrate 302 with two opposing sides 302a, 302b, a visible printed working 304 applied in contact with a first side 302a of the substrate 302, and an opacifying layer 306 which covers more than 50% (i.e. the majority) of the substrate 302 is applied (e.g. printed) over the printed working 304. Indeed, it will be seen from Figure 3, that the opacifying layer 306 covers more than 50% (i.e. the majority) of the security document 300.

Security document 300 may be manufactured using the processes described in reference to Figure 2(b) or any other appropriate manufacturing method.

As the substrate is at least semi-transparent, the printed working 304 is visible through the substrate against the background of the opacifying layer 306 from the second side of the substrate. Whilst from the first side of the substrate 302 the opacifying layer will be seen.

The substrate 302 is preferably transparent and colourless such that the printed working 304 and opacifying layer 306 are readily visible from the second side 302a of the substrate 302. However, in alternative embodiments the substrate 302 may have a coloured tint (i.e. it may absorb visible light of a specific wavelength or range of wavelength) or be translucent (i.e. it will scatter visible light but not be opaque). Particularly suitable materials include polymer substrates such as: polyethylene terephalate (PET), biaxially orientated

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PCT/GB2018/050813 polypropylene (BOPP), polycarbonate (PC), polyvinylchloride (PVC), polybutlylene terephalate (PBT), nylon or acrylic.

As illustrated in Figure 3, the opacifying layer 306 extends across the whole of the substrate 302 and completely overlays the print working 304, obscuring the print working when the document is viewed from the first side 302a of the substrate. However, in alternative embodiments, security documents with more complex visual appearances may be formed if the opacifying layer only partially overlays the first print working. In such embodiments, any regions of the document without the opacifying layer will form a “window” where the print working 304 may be seen from both sides of the document as, from the first side of the substrate, it is not overlaid or obscured by the opacifying layer 306.

As will be seen in Figure 3, print working 304 is formed of an ink or other material deposited on the surface of the substrate 302. Such printing consumables may be applied using a variety of printing methods, including gravure, flexographic, lithographic or intaglio printing. Gravure printing is considered to be particularly suitable for the implementations discussed herein given the high accuracy and good registration between workings that may be achieved using this method.

The print working 302 may be formed into a wide variety of patterns, markings or graphics. For instance, the working may comprise indicia (i.e. a graphic mark, symbol or sign which conveys a easily distinguishable piece of visual information), alphanumeric text, symbols, a portrait, a logo or other graphics. Alternatively, or additionally the print working 302 may comprise a security print such as guilloches, microtext, or repeating geometric patterns.

Any asymmetric print workings or opacifying layers will appear different when viewed from the two sides of the security document. Specifically, any indicia, pattern or graphic within the print working or opacifying layer will appear in a correct orientation when viewed from one side of the security document but will be reversed or mirrored when seen from the opposing side.

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This will not affect the appearance of symmetric designs which will appear unchanged. However, asymmetric indicia, graphics or alphanumeric text will appear mirrored or reversed when viewed through the substrate

Therefore, if print working 304 or opacifying layer 306 are asymmetric, and intended to be viewed in a specific orientation from the second side of the security document 300 they must be applied or printed above the first side 302a of the substrate 302 in a reverse or mirrored orientation. For instance, any text or numbers which are meant to be read from the second side 302b of the substrate 302 must be printed in reverse onto or above the first side 302a of the substrate.

The opacifying layer 306 provides an at least semi-opaque background for the print working so that the print working 304 is readily visible against it. The layer is preferably a netural colour such as white or grey and may be formed by a layer of ink containing a white or grey pigment. However, alternatively it may be formed by applying a coating of such an opacifying ink applied to the surface(s) of a layer. In further embodiments, the opacifying layer is formed of a polymeric, non-fibrous, light-scattering material. Multiple opacifying layers or ink coatings may be required to reach a sufficient opacity to provide a suitable background for the print working 304 to be easily observed.

Figure 4 shows a cross section of a security document 400 in accordance with another embodiment the present invention which comprises a number of further layers.

Like security document 300, shown in Figure 3, the security document 400 of Figure 4 comprises an at least semi-transparent substrate 402 with two opposing sides 402a, 402b, a visible printed working 404 applied in contact with a first surface 402a of the substrate, and an opacifying layer 406 which covers at least 50% of the substrate is applied (e.g. printed) over the printed working 404.

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Equally, it will be seen from Figure 4, that the opacifying layer 406 covers more than 50% (i.e. the majority) of the security document 400.

These layers and workings may have any of the properties or features of the corresponding components described above in relation to Figures 1 to 3.

Security document 400 further comprises a second visible print working 408 and a transparent spacing layer 410 containing a magnetic strip 410a provided above the first side 402a of the substrate, and a pair of transparent conductive layers 412, 414 on the exterior sides of the security document. Hence, all visible print workings, layers and security devices within document 400 are provided in contact with or above the first side 402a of the substrate.

Second print working 408 is located above opacifying layer 406. As such, it will be visible from the first side of the substrate 402a against the background of the opacifying layer 406. It may share any of the properties or features described above in reference to the print workings of Figures 1 to 3.

The layers and print workings of security document 400 may be applied using any suitable technique, including gravure, flexographic, lithographic or intaglio printing. In particularly preferred embodiments, at least the first print working 404 and the opacifying layer 406 may be applied using web fed gravure printing. This achieves achieve highly accurate registration between the first print working 404 and any patterns or images, and/or the windows 406a, 406b within the opacifying layer 406. Subsequently the second print working may be applied using sheet fed processes by lithographic and/or intaglio printing processes.

As the opacifying layer 406 is provided between the first and second print workings 404, 408 it is not necessary to apply an opacifying layer in contact with or above the second side 402b of the substrate 402. In regions where the opacifying layer 406 is provided, the first print working 404 will be visible from the first side 402a of the substrate 402 and the second print working 408 will be visible from the second side 402b of the substrate 402. However, the opacifying

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PCT/GB2018/050813 layer 406 will obscure the first print working 404 when viewing from the first side 402a, and the second print working 408 when viewed from the second side 402b. In other words, the opacifying layer 406 which covers the majority of the substrate decouples the visual appearances of the two sides of the security document 400, such that the two sides of the document may exhibit different visual appearances seen against the shared background of the opacifying layer 406.

Two windows 406a, 406b are formed within the security document 400 by omitting the opacifying layer 406 in the corresponding regions of the document. In alternative embodiments, where the opacifying layer is a layer of opacifying ink, or transparent material coated with an opacifying ink, windows with similar visual appearances may be formed by omitting the opacifying coating or ink from the window regions.

The windows 406a and 406b allow the creation of documents with complex security devices which may not be easily reproduced.

In regions of the document 400 corresponding to window 406a, only the first print working 404 is provided. As such, only the first print working is visible in window 406a. Whilst the first and second print workings will be seen adjacent to one another within window 406b.

Alternatively, a security document may have a first transparent window within which the first print working is visible from both sides of the document, and a second transparent window spaced from the first within which the second print working is visible from both sides of the document. In further embodiments exhibiting increasingly complex visual effects, the first and/or second print workings may be symmetric along at least one axis, and/or be registered to one another in the area of the document corresponding to a window.

Magnetic strip 410a, located within spacing layer 410, is applied above the first side 402a of the substrate 402. As such, magnetic strip 410, or any other

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PCT/GB2018/050813 suitable security device or security article, may be carefully registered to the other layers applied in contact with or above the first side 402a of substrate 402.

For instance, suitable security devices may include: microtext; fine line patterns; latent images; Venetian blind devices; lenticular devices; moire interference devices; moire magnification devices; holograms; diffractive gratings; watermarks; embossings; perforations; or the use of colour-shifting, iridescent, luminescent or fluorescent ink within the first, second or further print workings. Whilst suitable security articles include: security threads, strips, foils, inserts, transfer elements, labels or patches.

The pair of conductive layers 412, 414 which are sometimes termed anti-static layers, act to reduce the build up of static electricity on the security document and protect the surface of the security document from damage. Preferably these layers are transparent so as not to affect the visual appearance of the security document’s internal layers.

In further preferred embodiments, the security document may comprise one or more substantially opaque layers formed of a plurality of opacifying layers, wherein each opacifying layer is at least semi-opaque.

Where an opaque layer is formed of a plurality of overlapping opacifying layers a variety of complex security features may be achieved by omitting portions or regions of the opacifying layers. Such features include “shadowmarks”, which resemble conventional watermarks, and the features described in the applicant’s publications PCT/GB2016/052999 and PCT/GB2016/052997.

Where a region of an opacifying layer is omitted (i.e. where a transparent gap defined by the boundaries of each opacifying layer or transparent material is provided within the opacifying layer) the combined substantially opaque layer will be less opaque when viewed in transmission as the gap in the opacifying layer allows an increased amount of light to be transmitted through the substantially opaque layer. Consequently, complex visual features may be constructed by

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PCT/GB2018/050813 omitting different regions within multiple opacifying sub-layers, wherein the omitted regions in different sub-layers have different boundaries. Preferably the omitted regions in the different opacifying layers at least partially overlap.

Preferably at least one opacifying layer within the security document comprises a conductive additive or be formed of a conductive material. Such conductive layers will prevent the build up of static electricity within the security document.

Figure 5 shows an exploded view of a security document 500 in accordance with a further embodiment of the present invention.

Security document 500 comprises a substrate 502 with two opposed sides 502a, 502b. All of the visible print workings and layers in the security document 500 are applied in contact with or above the first side 502a of the substrate. Specifically, over the first side 502a of the substrate 504 are provided (in order): a print working 504; three spacing layers 510, 516, 518; an opacifying layer 506 which is disposed across approximately 90% of the substrate; a further spacing layer 520 and a first transparent conductive layer 512. A second transparent conductive layer 514 is applied to the second side 502b of the substrate 502.

Within the opacifying layer two windows 506a, 506b are provided. A plurality of windows 510a, 510b, 510c, 516a, 516b, 516c, 518a, 518b, 518c (not shown), 518d, 520a, 520b, 520c (not shown), 520d are located in the spacing layers 512, 516, 518, 520 applied above the first side 502a of the substrate 502. A further plurality of windows 512a, 512b, 512c, 512d are located in the first conductive layer.

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These layers, workings and windows may have any of the properties or features of the corresponding components described above in relation to Figures 1 to 4. Furthermore, any of the optional features described above with reference to Figures 1 to 4 may also be incorporated within this embodiment as appropriate.

Windows 510a, 516a, 518a, 506a, 510a and 512a are registered, such that each window is aligned with the corresponding windows in the layers above and below it. Windows 510b, 516b, 518b, 506b, 510b and 512b are also registered, such that each window is aligned with the corresponding windows in the layers above and below it. Similarly, windows 510c, 516c, 518c, 510c and 512c, and windows 518d, 520d and 512d, are also registered so that the windows are aligned in a similar fashion.

The spacing layers 512, 516, 518, 520 are formed of a substantially transparent and colourless polymer layer. In alternative embodiments the spacing layers may be translucent or at least semi-transparent. In further embodiments the spacing layers may exhibit a coloured tint.

The first print working 504 is formed of three component print workings 504a, 504b, 504c. Each component print working 504a, 504b, 504c is formed in a single colour, in this case red, green and blue, such that by combining inks in all three workings a wide range of visible colours may be achieved. Alternatively, a variety of other component print workings may be used to create patterns, markings or graphics with alternative colour ranges. For instance, four component print workings corresponding to the CMYK colour components may be provided.

Each component working comprises asymmetric text 504a1, 504b1, 504c1 and an indicia 504a2, 504b2, 504c2. The text 504a1, 504b1, 504c1 and indicia 504a2, 504b2, 504c2 of each layer are registered so that each visual feature may exhibit a range of colour. A highly accurate registration between these components of the text and indicia is achieved by applying each of the visible

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PCT/GB2018/050813 component print workings 504a, 504b, 504c in contact with or above the first side 502a of the substrate 502. This allows the creation of security documents which exhibit highly detailed and visually complex coloured appearances.

As discussed above with reference to Figure 3, these visual features are applied above the first side 502a of the substrate 502 in a mirrored or reversed orientation. Therefore, when the document is viewed from the second side 502b of the substrate the text and the indicia appear in their correct orientation.

The location of the indicia corresponds to the lateral position of window 506a in the opacifying layer, windows 510a, 516a, 518a, 520a in spacing layers 510, 516, 518, 520 and window 512a in the first conductive layer 512 respectively. Hence, the indicia in first printed layer 504 will be visible within these windows from the first and the second sides 502a, 502b of the substrate 502.

The boundary of window 506a within the opacifying layer 506 exactly corresponds to the boundary of the indicia 504a2, 504b2, 504c2 printed within of the first print working 504. Consequently, from both sides of the device the indicia will be seen against the background of the opacifying layer 506. This visual appearance relies on highly accurate registration between the components of the security document. If the registration between the indicia 504a2, 504b2, 504c2 and the window 506a in the opacifying layer 506 is inaccurate, a “fringe” or lining of dissimilar optical appearance will be seen surrounding the edges of the indicia because the transparent window, opaque portions of the opacifying layer 506 and the colour component print workings 504a, 504b, 504c do not accurately register or correspond. Therefore, the window and indicia form a complex security device which is extremely difficult for would-be counterfeiters to reproduce.

The layers, print workings, security devices and security articles discussed above with reference to Figures 1 to 5 may be held together by heat, adhesive or any other suitable means.

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In further embodiments, a security document may comprise a plurality of further layers in any location. These layers may include: further print workings or opacifying layers (with the exception that any opacifying layer that covers 50% or more of the substrate must be applied in contact with or above the first side of the substrate); anti-static conductive layers; protective layers intended to prevent or mitigate damage to or tampering with the print workings; adhesive layers; a transparent varnish which may comprise a matting additive to reduce the gloss of the security document and/or to prevent the documents sticking together when they are stacked; and spacing layers separating the layers and/or workings discussed above.

The security document of the current invention may optionally be made machine readable by the introduction of detectable materials in any of the layers or by the introduction of separate machine-readable layers. Detectable materials that react to an external stimulus include but are not limited to fluorescent, phosphorescent, infrared absorbing, thermochromic, photochromic, magnetic, electrochromic, conductive and piezochromic materials. Preferably the document comprises one or more opacifying layers formed of an electrically conductive material, to provide anti-static properties.

These optional features apply to all aspects of the invention discussed above.

Claims

1. A security document comprising:

an at least semi-transparent substrate having opposed first and second sides;

a first print working in contact with or above a first side of the substrate; and at least one opacifying layer disposed in contact with or above the first side of the substrate so that it at least partially overlays the first print working; wherein any opacifying layer that is disposed across 50% or more of the substrate is disposed in contact with or above the first side of the substrate, such that when the security document is viewed from the second side of the substrate, at least a portion of the first print working is visible against the background of the said at least one opacifying layer disposed in contact with or above the first side of the substrate.

2. The security document of claim 1, wherein all visible print workings are disposed in contact with or above the first side of the substrate.

3. The security document of claim 1 or claim 2, wherein all visible layers are disposed in contact with or above the first side of the substrate.

4. The security document of any preceding claim, further comprising at least one second print working disposed in contact with or above the opacifying layer furthest from the substrate.

5. The security document of any preceding claim, wherein the substrate is formed of a substantially visually transparent and preferably colourless material.

6. The security document of any preceding claim, wherein the substrate comprises a plastic material, such as: polyethylene terephalate (PET), biaxially orientated polypropylene (BOPP), polycarbonate (PC), polyvinylchloride (PVC), polybutlylene terephalate (PBT), nylon or acrylic.

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7. The security document of any preceding claim, wherein the substrate comprises a single layer.

8. The security document of claims 1 to 6, wherein the substrate is multilayered.

9. The security document of any preceding claim, wherein the substrate is formed of a conductive material.

10. The security document of any preceding claim, further comprising a substantially transparent conductive layer, wherein the conductive layer is disposed in contact with or above the second side of the substrate.

11. The security document of any preceding claim, wherein the first and/or second print workings comprise at least one item of information comprising any of: indicia, alphanumeric text, a letter or number, a symbol, a portrait, a logo or another graphic.

12. The security document of any preceding claim, wherein the first and/or second print workings include any of: security prints, guilloches, microtext, or repeating geometric patterns.

13. The security document of any preceding claims, wherein the first and/or second print workings are formed by one of: gravure, flexographic, lithographic or intaglio printing.

14. The security document of any preceding claims, wherein the first and/or second print workings comprise a plurality of component print workings, wherein preferably each of the plurality of component print workings is a different colour or tone.

15. The security document of any preceding claim, wherein one or more opacifying layers comprise an opaque, translucent or semi-opaque material.

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16. The security document of any preceding claim, wherein one or more opacifying layers comprise an ink or coating preferably comprising a white or grey pigment.

17. The security document of any preceding claim, wherein one or more opacifying layers comprise a polymeric, non-fibrous, light-scattering material.

18. The security document of any preceding claim, wherein one or more opacifying layers are disposed across at least 50% of the substrate, preferably across at least 75% of the substrate, more preferably across at least 90% of the substrate, still more preferably across at least 95% of the substrate.

19. The security document of any preceding claim, wherein one or more opacifying layers extend across the entirety of the substrate, such that the first print working is not visible from the first side of the substrate.

20. The security document of any preceding claim, wherein any opacifying layers disposed across 75% or more of the substrate is disposed in contact with or above the first side of the substrate, preferably wherein any opacifying layer disposed across 90% or more of the substrate is disposed in contact with or above the first side of the substrate.

21. The security document of any preceding claim, wherein one or more opacifying layers define one or more transparent windows.

22. The security document of claim 21, wherein the one or more transparent windows are defined by the boundary of the one or more opacifying layers or by a region of substantially transparent material within the one or more opacifying layers.

23. The security document of claims 21 to 22, wherein within the one or more transparent windows respective portions of the first and/or second print workings are visible from both sides of the security document.

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24. The security document according to any preceding claim, further comprising a transparent varnish layer, wherein the transparent varnish preferably comprises a matting additive.

25. The security document according to any preceding claim, further comprising at least one security device, wherein all of the security devices are disposed in contact with or above the first side of the substrate, and wherein the at least one security devices preferably comprise one or more of: microtext; fine line patterns; latent images; Venetian blind devices; lenticular devices; moire interference devices; moire magnification devices; holograms; diffractive gratings; watermarks; embossings; perforations; or one or more colour-shifting, iridescent, luminescent or fluorescent inks.

26. The security document according to claim 25, wherein at least a portion of a first security device is visible from at least one side of the substrate within a transparent window defined by one or more opacifying layers.

27. The security document according to any preceding claim, further comprising at least one security article, wherein all of the security articles are disposed in contact with or above the first side of the substrate, and wherein the at least one security articles preferably comprise a security thread, strip, foil, insert, transfer element, label or patch.

28. The security document according to claim 27, wherein at least a portion of a first security article is visible from at least one side of the substrate within a transparent window defined by one or more opacifying layers.

29. The security document according to any preceding claim, wherein the security document is a banknote, cheque, page or sheet of a passport, identity card, bank card, driver’s licence, certificate of authenticity, fiscal stamp or other document for securing value or personal identity.

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30. A method of manufacturing a security document, wherein the security document comprises an at least semi-transparent substrate having opposed first and second sides, the method comprising the steps of:

printing a first print working in contact with or above a first side of the substrate; and applying at least one opacifying layer in contact with or above the first side of the substrate so that it at least partially overlays the first print working; wherein any opacifying layer that is disposed across 50% or more of the substrate are disposed in contact with or above the first side of the substrate of the substrate, such that, when the security document is viewed from the second side of the substrate, at least a portion of the first print working is visible against the background of the at least one opacifying layer disposed in contact with or above the first side of the substrate.

31. The method according to claim 30, wherein all visible print workings are disposed in contact with or above the first side of the substrate.

32. The method according to claim 30 or claim 31, wherein all visible layers are disposed in contact with or above the first side of the substrate.

33. The method according to claims 30 to 32 wherein the documents are manufactured using a web fed process or a sheet fed process, or a method that comprises web fed and sheet fed processes.

34. The method according to any of claims 30 to 33, further comprising printing at least one second print working in contact with or above the side of the opacifying layer furthest from the substrate.

35. The method according to any of claims 30 to 34, wherein the substrate is formed of a substantially visually transparent and preferably colourless material.

36. The method according to any of claims 30 to 35, wherein the substrate comprises a plastic material, such as: polyethylene terephalate (PET), biaxially

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PCT/GB2018/050813 orientated polypropylene (BOPP), polycarbonate (PC), polyvinylchloride (PVC), polybutlylene terephalate (PBT), nylon or acrylic.

37. The method according to any of claims 30 to 36, wherein the substrate comprises a single layer.

38. The method according to any of claims 30 to 37, wherein the substrate is multi-layered.

39. The method according to any of claims 30 to 38, wherein the substrate is formed of a conductive material.

40. The method according to any of claims 30 to 39, wherein the security document further comprises a substantially transparent conductive layer, wherein the conductive layer is disposed in contact with or above the second side of the substrate.

41. The method according to any of claims 30 to 40, further comprising the step of applying a substantially transparent conductive layer in contact with or above the second side of the substrate.

42. The method according to claim 41, wherein, when the conductive layer is disposed in contact with or above the second side of the substrate, the substantially transparent conductive layer is applied to the substrate prior to the printing of the print workings or the application of the opacifying layer.

43. The method according to any of claims 30 to 42, wherein the first and/or second print workings comprise at least one item of information comprising any of: indicia, alphanumeric text, a letter or number, a symbol, a portrait, a logo or another graphic.

44. The method according to any of claims 30 to 43, wherein the first and/or second print workings include any of: security prints, guilloches, microtext, or repeating geometric patterns.

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45. The method according to any of claims 30 to 44, wherein the first and/or second print workings are formed by one of: gravure, flexographic, lithographic or intaglio printing.

46. The method according to any of claims 30 to 45, wherein the first and/or second print workings comprise a plurality of component print workings, wherein preferably each of the plurality of component print workings is a different colour or tone.

47. The method according to any of claims 30 to 46, wherein one or more opacifying layers comprise an opaque, translucent or semi-opaque material.

48. The method according to any of claims 30 to 47, wherein one or more opacifying layers comprise an ink or coating preferably comprising a white or grey pigment.

49. The method according to any of claims 30 to 48, wherein one or more opacifying layers comprise a polymeric, non-fibrous, light-scattering material.

50. The method according to any of claims 30 to 49, wherein one or more opacifying layers are disposed across at least 50% of the substrate, preferably across at least 75% of the substrate, more preferably across at least 90% of the substrate, still more preferably across at least 95% of the substrate.

51. The method according to any of claims 30 to 50, wherein one or more opacifying layers extend across the entirety of the substrate, such that the first print working is not visible from the first side of the substrate.

52. The method according to any of claims 30 to 51, wherein any opacifying layer disposed across 75% or more of the substrate is disposed in contact with or above the first side of the substrate, preferably wherein any opacifying layer disposed across 90% or more of the substrate is disposed in contact with or above the first side of the substrate.

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53. The method according to any of claims 30 to 52 wherein one or more opacifying layers define one or more transparent windows.

54. The method according to claim 53, wherein the one or more transparent windows are defined by the boundary of the one or more opacifying layers or by a region of substantially transparent material within the one or more opacifying layers.

55. The method according to any of claims 53 to 54, wherein within the one or more transparent windows respective portions of the first and/or second print workings are visible from both sides of the security document.

56. The method according to any of claims 30 to 55, further comprising the step of applying a transparent varnish layer in contact with or above the first and/or second sides of the substrate, wherein the transparent varnish preferably comprises a matting additive.

57. The method according to any of claims 30 to 56, further comprising at least one security device, wherein all of the security devices are disposed in contact with or above the first side of the substrate, and wherein the at least one security device preferably comprise one or more of: microtext; fine line patterns; latent images; Venetian blind devices; lenticular devices; moire interference devices; moire magnification devices; holograms; diffractive gratings; watermarks; embossings; perforations; or one or more colour-shifting, iridescent, luminescent or fluorescent inks.

58. The method according to claim 57, wherein at least a portion of a first security device is visible from at least side of the substrate within a transparent window defined by one or more opacifying layers.

59. The method according to any of claims 30 to 58, further comprising at least one security article, wherein all of the security articles are disposed in contact with or above the first side of the substrate, and wherein the at least one security article preferably comprise a security thread, strip, foil, insert, transfer element, label or patch.

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60. The method according to claim 59, wherein at least a portion of the security article is visible from at least one side of the substrate within a transparent window defined by one or more opacifying layers.

61. The method according to any of claims 30 to 60, wherein the security document is a banknote, cheque, page or sheet of a passport, identity card, driver’s licence, certificate of authenticity, fiscal stamp or other document for securing value or personal identity.