AU2017101588A4 - See-through security device - Google Patents

Abstract

The invention is directed to a method of producing a security device and a security document including the security device. The method includes creating a region of reduced opacity in a polymer substrate, forming a first visual feature on a first side of the substrate, forming a second visual feature on a second side of the substrate opposite the first side, wherein at least a portion of the first visual feature or the second visual feature overlaps with the region of reduced opacity, and wherein when the substrate is viewed in transmission, the first and second visual features complement one another to form a complete image or a portion of a complete image. Figure 1A Figure 1B Figure 1C

Description

See-Through Security Device Technical Field [0001] The invention described herein relates to a method of producing a security feature and a security document including the security feature. In particular, the security feature includes a see-through device, although the scope of the invention may not necessarily be limited thereto.

Background of Invention [0002] See-through security features or see-through devices are spatially related image-elements in substantially seamless front-to-back register on opposite sides of a security document, such as a bank note. When the security document is held against the light (i.e. viewed in transmission), the register of the front and back image elements is revealed.

[0003] In some cases, see-through devices can be difficult to identify and therefore not easily recognised by the general public as a security feature.

[0004] Embodiments of the invention may overcome or ameliorate the disadvantage or problem described above, or which at least provides the consumer with a useful choice.

Summary of Invention [0005] According to one aspect of the invention, there is provided a method of producing a security device, the method including creating a region of reduced opacity in a polymer substrate, forming a first visual feature on a first side of the substrate, forming a second visual feature on a second side of the substrate opposite the first side, wherein at least a portion of the first visual feature or the second visual feature overlaps with the region of reduced opacity, and wherein when the substrate is viewed in transmission, the first and second visual features complement one another to form a complete image or a portion of a complete image.

[0006] Advantageously, the region of reduced opacity allows the complete image (e.g. a see-through device) to become more easily identified, even if the opacity of the substrate outside the region of reduced opacity is relatively high.

[0007] The region of reduced opacity may be created in a variety of different ways. The method for reducing opacity may depend on the nature and type of substrate used. For polymer substrates having a plurality of opacifying layers, the step of creating a region of reduced opacity may include varying a number of opacifying layers in the region. The number of opacifying layers may differ across the region such that the degree of opacity differs across the region. In particular, the opacity may be comparatively lower in some portions of the region, and the opacity may be comparatively higher in some portions of the region. The region may include portions of reduced opacity. In some embodiments, the region may include portions of increased opacity.

[0008] In some embodiments, the step of creating a region of reduced opacity may include reducing a number of opacifying layers in the region. The number of opacifying layers may be reduced evenly across the region. Alternatively, the number of opacifying layers may differ across the region whilst maintaining an overall reduction in a total number of opacifying layers in the region.

[0009] The method may include applying a plurality of opacification layers to a translucent or transparent base substrate so as to create opacified substrate with a degree of opacity, and wherein the step of creating a region of reduced opacity includes varying the density of at least one of the opacifying layers. In one embodiment, each opacifying layer may be printed onto the base substrate using ink and for at least one of the opacifying layers, the amount of ink used in the region of reduced opacity may be less than the amount of ink used outside the region. In one example, the opacifying layers are applied using gravure printing and the amount or density of ink used for a given opacifying layer may be expressed in lines per cm. An opacifying layer may be applied having areas of 100 lines/cm corresponding to a region of reduced opacity, and areas of 50 lines/cm in areas outside the region.

[0010] In some embodiments, the step of creating a region of reduced opacity may include varying the thickness of the substrate in the region. In some embodiments, the step of creating a region of reduced opacity may include reducing the density of the substrate in the region. Any suitable process may be used to reduce the thickness and/or density of the substrate. For example, processing including embossing, etching, engraving and the like, and/or a combination thereof. In some embodiments, the region of reduced opacity may define a shadow image. In some embodiments, the first and second visual features combined with the region of the reduced opacity may define a complete image. In particular, the first and second visual features may define a see-through device which defines a first incomplete image. The shadow image in the region of reduced opacity may define a second incomplete image. The first incomplete image may complement the second incomplete image to form one complete image.

[0011 ] According to a further aspect of the invention, there is provided a method of producing a security device, the method including reducing opacity of a first region of a polymer substrate, forming a see-through device in a second region of the substrate, wherein the first region at least partially overlaps with the second region.

[0012] According to another aspect of the invention, there is provided a method of producing a security device, the method including providing a translucent or transparent base substrate, applying opacifying layers to opposite sides of the transparent base substrate so as to create an opacified substrate having a degree of opacity across the substrate, wherein at least one of the opacifying layers defines one or more openings so as to create a region of reduced opacity in the opacified substrate, forming a first visual feature on a first side of the substrate, forming a second visual feature on a second side of the substrate opposite the first side, wherein at least a portion of the first visual feature or the second visual feature overlaps with the region of reduced opacity, and wherein when the substrate is viewed in transmission, the first and second visual features complement one another to form a complete image or a portion of a complete image.

[0013] According to yet another aspect of the invention, there is provided a security document including a region of reduced opacity in a polymer substrate, a first visual feature on a first side of the substrate, a second visual feature on a second side of the substrate opposite the first side, wherein at least a portion of the first visual feature or the second visual feature overlaps with the region of reduced opacity, and wherein when the substrate is viewed in transmission, the first and second visual features complement one another to form a complete image or a portion of a complete image.

[0014] Opacity may be measured using any suitable instrument. In one example, a Photovolt 577 contrast ratio meter may be used. In this example, a portion of the substrate outside the region may have an opacity value of about 77.5 or greater as measured by the Photovolt 577 contrast ratio meter and the region of reduced opacity may have an opacity value of 2 to 9 lower than that outside the region.

[0015] According to another aspect of the invention, there is provided a polymer based security document including a region of reduced opacity, and a see-through device, wherein the region at least partially overlaps with the see-through device.

[0016] The first region may define a shadow image. The shadow image may complement the see-through device to create a complete image.

[0017] The shadow image may be created by creating one or more openings in one or more opacifying layers of an opacified substrate. The one or more openings may be of any suitable size/shape and positioned in any suitable location in each layer. In one embodiment, the one or more openings may be the same shape and size and location. In other embodiments, the one or more openings may each have a different shape, size and location on the corresponding layer so as to create a shadow image of varying opacity. The opacity of a shadow image can be varied in this manner to create a high definition shadow image. The shadow image may complement a see-through device to create a complete image. The complete image may incorporate two or more security features.

[0018] According to yet another aspect of the invention, there is provided a method of producing a substrate, the method including creating a first region of reduced opacity in a polymer substrate, providing a second region on the substrate for locating a see-through device, wherein the first region overlaps with the see-through device.

[0019] In order that the invention may be more readily understood and put into practice, one or more preferred embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings.

[0020] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristic described herein may be combined in any suitable manner in one or more combinations.

Security Document or Token [0021 ] As used herein, the term security documents and tokens includes all types of documents and tokens of value and identification documents including, but not limited to the following: items of currency such as banknotes and coins, credit cards, cheques, passports, identity cards, securities and share certificates, driver's licenses, deeds of title, travel documents such as airline and train tickets, entrance cards and tickets, birth, death and marriage certificates, and academic transcripts.

[0022] The invention is particularly, but not exclusively, applicable to security documents or tokens such as banknotes or identification documents such as identity cards or passports formed from a substrate to which one or more layers of printing are applied.

Substrate [0023] As used herein, the term substrate refers to the base material from which the security document or token is formed. The base material may be a plastic or polymeric material including but not limited to polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET); or a composite material of two or more materials, such as a laminate of paper and at least one plastic material, or of two or more polymeric materials.

[0024] The use of plastic or polymeric materials in the manufacture of security documents pioneered in Australia has been very successful because polymeric banknotes are more durable than their paper counterparts and can also incorporate new security devices and features. One particularly successful security feature in polymeric banknotes produced for Australia and other countries has been a transparent area or "window".

Transparent Windows and Half Windows [0025] As used herein, the term window refers to a transparent or translucent area in the security document compared to the substantially opaque region to which printing is applied. The window may be fully transparent so that it allows the transmission of light substantially unaffected, or it may be partly transparent or translucent partially allowing the transmission of light but without allowing objects to be seen clearly through the window area.

[0026] A window area may be formed in a polymeric security document which has at least one layer of transparent polymeric material and one or more opacifying layers applied to at least one side of a transparent polymeric substrate, by omitting at least one opacifying layer in the region forming the window area. If opacifying layers are applied to both sides of a transparent substrate a fully transparent window may be formed by omitting the opacifying layers on both sides of the transparent substrate in the window area.

[0027] A partly transparent or translucent area, sometimes referred to as a "half window", may be formed in a polymeric security document which has opacifying layers on both sides by omitting the opacifying layers on one side only of the security document in the window area so that the "half-window" is not fully transparent, but allows some light to pass through without allowing objects to be viewed clearly through the half-window.

[0028] Alternatively, it is possible for the substrate to be formed from an substantially opaque material, such as paper or fibrous material, with an insert of transparent plastics material inserted into a cut-out, or recess in the paper or fibrous substrate to form a transparent window or a translucent half-window area.

[0029] The term "window" used herein encompasses fully transparent windows, translucent windows and "half windows".

Opacifying layers [0030] One or more opacifying layers may be applied to a transparent substrate to increase the opacity of the security document. An opacifying layer is such that LT < L0, where L0 is the amount of light incident on the document, and LT is the amount of light transmitted through the document. An opacifying layer may comprise any one or more of a variety of opacifying coatings. For example, the opacifying coatings may comprise a pigment, such as titanium dioxide, dispersed within a binder or carrier of heat-activated or oxidising cross-linkable polymeric material. Alternatively, a substrate of transparent plastic material could be sandwiched between opacifying layers of paper or other partially or substantially opaque material to which indicia may be subsequently printed or otherwise applied.

Security Device or Feature [0031] As used herein, the term security device or feature includes any one of a large number of security devices, elements or features intended to protect the security document or token from counterfeiting, copying, alteration or tampering. Security devices or features may be provided in or on the substrate of the security document or in or on one or more layers applied to the base substrate, and may take a wide variety of forms, such as security threads embedded in layers of the security document; security inks such as fluorescent, luminescent and phosphorescent inks, metallic inks, iridescent inks, photochromic, thermochromic, hydrochromic or piezochromic inks; printed and embossed features, including relief structures; interference layers; liquid crystal devices; lenses and lenticular structures; optically variable devices (OVDs) such as diffractive devices including diffraction gratings, holograms and diffractive optical elements (DOEs). Diffractive Optical Elements (DOEs) As used herein, the term diffractive optical element refers to a numerical type diffractive optical element (DOE). Numerical-type diffractive optical elements (DOEs) rely on the mapping of complex data that reconstruct in the far field (or reconstruction plane) a two-dimensional intensity pattern. Thus, when substantially collimated light, e.g. from a point light source or a laser, is incident upon the DOE, an interference pattern is generated that produces a projected image in the reconstruction plane that is visible when a suitable viewing surface is located in the reconstruction plane, or when the DOE is viewed in transmission at the reconstruction plane. The transformation between the two planes can be approximated by a fast Fourier transform (FFT). Thus, complex data including amplitude and phase information has to be physically encoded in the micro structure of the DOE. This DOE data can be calculated by performing an inverse FFT transformation of the desired reconstruction (i.e. the desired intensity pattern in the far field).

Region [0032] A region, as used herein, corresponds to an area of a surface of a security document or a substrate. For example, a first region located on a first side of a substrate is a different region to a second region located on a second side of the same substrate, even when the two regions are opposite one another. Two regions can be: opposite, wherein each region is located in the same area of the security document or substrate but on opposite surfaces; partially opposite, wherein one region includes a portion opposite all or a portion of the other region; and nonopposite, wherein the regions are entirely not opposite each other.

[0033] The foregoing embodiments are intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions as will readily occur to those skilled in the art.

[0034] Accordingly, it is to be understood that the scope of the invention is not to be limited to the exact construction and operation described and illustrated, but only by the following claims which are intended to include all suitable modifications and equivalents permitted by the applicable law.

Brief Description of Drawings [0035] Figures 1A to 1C illustrate a see-through device for printing on a security document.

[0036] Figure 2A is a cross sectional view of a security document embodying a see-through device in accordance with the prior art.

[0037] Figures 2B to 2F are cross sectional views of security documents embodying a see-through device according to embodiments of the invention.

[0038] Figures 3A to 3C are cross sectional views of security documents embodying a see-through device according to further embodiments of the invention.

[0039] Figure 4A is a plan view of the security document of Figure 2A embodying a see-through device.

[0040] Figure 4B is a plan view of the security documents shown in Figures 2B, 2C and 2D embodying a see-through device.

[0041] Figure 4C is a plan view of the security document shown in Figure 2E embodying a see-through device.

[0042] Figure 4D is a plan view of the security document shown in Figure 2F embodying a see-through device.

[0043] Figures 5A and 5B are plan views of security documents according to further embodiments of the invention.

[0044] Figure 6A is a plan view of a security document including a shadow image.

[0045] Figure 6B is a plan view of a security document including the shadow image as shown in Figure 6A and further including a see-through device complementing the shadow image to form a complete image according to a further embodiment of the invention.

[0046] Figure 6C is a plan view of a security document including a shadow image similar to the one shown in Figure 6A in which the shadow image includes regions of varying opacity and further including a see-through device complementing the shadow image to form a complete image according to yet another embodiment of the invention.

[0047] Figure 7 is a flow diagram illustrating a method of producing a security device according to an embodiment of the invention.

Detailed Description [0048] An example see-through device 104 in a banknote is illustrated in Figures 1A to 1C. Figures 1A and 1B respectively illustrate complementary images 100, 102 printed on opposite sides of a banknote in registration. In particular, an incomplete part of a bug 100 is printed on one side; and a complementary incomplete part of a bug 102 is printed on a reverse side. The complete image of the bug 104 as illustrated in Figure 1C can be reconstructed by placing the banknote in transmission. Special printing equipment, such as a Simultan printing press can be used to create the related image-elements in precise registration on opposite sides of the security document using offset printing.

[0049] As shown in Figure 2A, the cross sectional view of a security document 200a illustrates a see-through device 202 in which visual features 204 on one side of a substrate 208a is printed in registration with visual features 206 on an opposite side of the substrate 208a. A shown in Figure 4A, when the security document 200a is held against the light (i.e. viewed in transmission), the visual features 206 on a reverse side of the substrate 208a shows through (in suitable illumination conditions) and a complete image of the see-through device 202 including visual features 204, 206 can be seen.

[0050] Figure 2A and 4A illustrate a known security document 200a embodying a see-through device 202, which can often be difficult to identify, particularly if the opacity of the substrate 208a is high.

[0051 ] Figure 2A illustrates a polymer substrate 208a including a transparent base substrate 210 to which a plurality of opacifying layers 212 have been applied. Each of the opacifying layers 212 is printed using coloured ink to increase the opacity of the opacified substrate 208a. Any suitable coloured ink may be used. In one embodiment, the opacifying layers 212 are printed using white ink. The opacity of substrate 208a increases with application with each additional pacification layer 212. Figure 2A illustrates that the substrate 208a has two opacifying layers 212 on one side of the substrate 208a and three opacifying layers 212 on a reverse/opposite side of the substrate 208a. In other embodiments, an opacified substrate can have any suitable number of opacifying layers on each side of the substrate.

[0052] The opacity of a substrate 208a can be measured using special instrumentation such as a Photovolt 577 Contrast Ratio Meter. Typically, for banknotes, a minimum level of opacity will be required to prevent images printed on one side of the banknote from undesirably showing to the opposite side. For example, Guardian® banknotes typically have a minimum opacity value of 77.5 as measured by a Photovolt 577 Contrast Ratio Meter. High opacity substrates may have an opacity value of roughly 90 to 95.

[0053] The opacity of each opacifying layer may change depending on the type, colour and amount of ink used for each layer. In one example, a particular type of white ink is used and the following opacity values as shown in Table 1 below were obtained using a Photovolt 577 Contrast Ratio Meter.

Table 1: Opacity values for polymer substrate having opacifying layers applied using white ink.

[0054] As shown in Table 1 above, the opacity of the sample of clear polymer substrate is 2.7. The opacity of a polymer substrate having a single opacifying layer may range from 53 to 60.7 depending on the thickness of ink applied in the opacifying layer. Similarly, the opacity of a polymer substrate having two opacifying layers may range from 65.1 to 71.7; the opacity of a polymer substrate having three opacifying layers may range from 70.1 to 77.7; the opacity of a polymer substrate having four opacifying layers may range from 74.4 to 81.7; the opacity of a polymer substrate having five opacifying layers may range from 77.2 to 84.5. Higher or lower opacity values may be achieved at differing ink thicknesses.

[0055] In accordance with an embodiment of the invention, the opacity for a region of reduced opacity 214 of a five-layerd substrate with an opacity of 85 may range from 60 to 83 as measured by a Photovolt 577 Contrast Ratio Meter. Moreover, the region of reduced opacity 214 may provide a reduction in opacity of roughly between 2 to 35 when compared to the opacity of a surrounding region of the substrate.

[0056] As shown in Figure 2B, a region of reduced opacity 214 is created in security document 200b according to one embodiment of the invention. In this embodiment, the region of reduced opacity 214 is created by defining an opening in an outermost opacifying layer 212 on one side of the substrate 208b (also known as ‘reversing out’ an opacifying layer of the substrate). Now referring to Figure 4B, which illustrates a plan view of the security document 200b. As the see-through device 202 is printed in the region of reduced opacity 214, when the security document 200b is viewed in transmission, the see-through device 202 is easier to identify when compared to the security document 200a as shown in Figures 2A and 4A, under the same illumination conditions.

[0057] Figures 2C and 2D illustrate security documents 200c, 200d according to further embodiments of the invention. In Figure 2C, an opening is defined in an inner opacifying layer 212 on one side of the substrate 208c to create the region of reduced opacity 214. In Figure 2D, an opening is defined in an outermost opacifying layer 212 on a reverse side of the substrate 208d. Similar to the security document 200b in Figure 2B, as the total number of opacifying layers 212 in the region 214 of substrates 208c, 208d is also reduced from five to four, the same opacity reduction affect can be achieved as illustrated in Figure 4B, thereby allowing the see-through device 202 printed within the region 214 to be more easily identified. The opacity value in the region 214 of Figure 4B may be reduced by roughly 2 to 3 as measured by a Photovolt 577 Contrast Ratio Meter.

[0058] Figures 2E and 2F illustrate that the opacity in the region 214 can be further reduced by defining an opening in more than one opacifying layer 212. For example, an opening is defined in each of two outermost opacifying layers 212 of the substrate 208e in Figure 2E. Figure 4C illustrates that as the see-through device 202 is printed in the region 214 in which opacity is further reduced, the device 202 is even more easily identified when the substrate 208e is viewed in transmission.

[0059] In the security document 200f as shown in Figure 2F, an opening is defined on an outermost opacifying layer 212 on one side of the substrate 208f and two outermost opacifying layers 212 on a reverse side of the substrate 208f, creating a region 214 in which opacity is further reduced. Figure 4D illustrates that as the see-through device 202 is printed in the region 214 in which opacity is further reduced, the device 202 can be even more easily identified when the substrate 208f is viewed in transmission.

[0060] In the security document 200g as shown in Figure 3A, the region of reduced opacity 214 can include varying degrees of opacity, for example to create a shadow image as further described below with reference to Figures 6A to 6C. Elaborating further, in the region of reduced opacity 214, an outermost upper opacifying layer 212 defines an opening, an intermediate underside opacifying layer 212’ also defines an opening substantially aligned with the opening in the outermost upper layer 212, and an outermost underside opacifying layer 212” defines three openings each having a different size and position relative to those in the other layers 212, 212’. In this manner, a high definition shadow image 216 can be created by varying opacity within the region 214 by defining openings of different sizes, shapes and positions in each opacifying layer 212. In the embodiment in Figure 3A, the see-through device 202 is positioned in a portion of the region 214 having the lowest opacity so as to facilitate identification.

[0061] In the security document 200h as shown in Figure 3B, the region of reduced opacity 214 includes two separate portions 218a, 218b in which the opacity of the substrate 208h is reduced. In particular, an outermost opacifying layer 212 defines two openings 218a, 218b and visual features 206 of the see-through device 202 are located entirely within the respective openings 218a, 218b. Visual features 204 on an opposite side of the substrate 208h may partially overlap with the openings 218a, 218b. Therefore in security document 200h, the see-through device 202 partially overlaps with the region of reduced opacity 214. The opacity value in the region 214 of Figure 3B may be reduced by roughly 2 to 3 as measured by a Photovolt 577 Contrast Ratio Meter.

[0062] In the security document 200i as shown in Figure 3C, the region of reduced opacity 214 is similar to that of security document 200d as shown in Figure 2D. However, at least portion 220 of visual features 206 of the see-through device 202 is located outside the region 214 of reduced opacity. A portion of visual features 204 may also be located outside region 214. The opacity value in the region 214 of Figure 3C may be reduced by roughly 2 to 3 as measured by a Photovolt 577 Contrast Ratio Meter.

[0063] Figures 2B to 3C only illustrate some of the non-exhaustive example embodiments of security documents 200 of the present invention. Many other different ways to create one or more regions of reduced opacity 214, shadow images and relative positions between the see-through device(s) 202 and the region(s) 214 are possible without departing from the scope of the present invention.

[0064] The security document 500a in Figure 5A further illustrates that the see-through device 202 may not be positioned entirely with the region of reduced opacity 502. Indeed, the see-through device 202 is partially within the region of reduce opacity 502. In other words, portions of the see-through device 202 of security document 500a overlap with the region of reduced opacity 502.

[0065] The security document 500b in Figure 5B further illustrates that the region of reduce opacity 504 includes two portions 504a, 504b. Visual features 206 on a reverse side of the security document 500b are formed within respective portions 504a, 504b whilst visual features 204 are outside the region of reduced opacity 504.

In other embodiments, portions of the visual features 206 may be formed within the region of reduce opacity 504 whilst some portions of the visual feature 206 may be formed outside the region 504.

[0066] In the embodiments described with reference to Figures 5A and 5B, the improved ability to identify the see-through device 202 can still be achieved. In addition, the region of reduced opacity 504 may complement the design of the see-through device 202.

[0067] Figures 6B to 6C illustrate a security document 600 according to an embodiment of the invention in which the region of reduced opacity 602 defines a shadow image and complements a see-through device to form a complete image.

[0068] Figure 6A illustrates that the region of reduced opacity can define a shadow image 602. In the example of Figure 6A, the shadow image 602 includes multistorey buildings. For example, the shape of an opening in one or more opacification layers defines the features of the shadow image 602.

[0069] As shown in Figure 6B, a see-through device 608 includes visual features 604 formed on a front side of the security document 600b and complementary visual features 606 on a reverse side of the security document 600b. In transmission, it can be seen that the visual features 604, 606 are formed in substantially perfect registration to provide a portion of a complete image (i.e. the windows of a building in the shadow image 602). The see-through device 608 is also formed in registration with the shadow image 602 to complement one another so as to form a complete image. The complete image in Figure 6B includes a shadow image 602 of multistorey buildings and the windows of one of the buildings are represented by the see-through device 608.

[0070] The security document 600c as illustrated in Figure 6C further includes an additional region of reduced opacity 610 which overlaps with the shadow image 602. In particular, the additional region of reduced opacity 610 defines one of the buildings in the shadow image 602 encompassing the see-through device 608. The opacity of region 610 is lower than that of the shadow image 602 further facilitating the identification of the see-through device 608.

[0071] A method 700 of producing a see-through device 608 on a security document (e.g. security document 600c as shown in Figure 6C) according to an embodiment of the invention will now be described with reference to Figure 7.

[0072] At step 702, a design for a security document 600c is created. For banknotes, the design will typically include a variety of different visual features including different security devices such as shadow images and see-through devices.

[0073] At step 704, the visual features and security devices are divided into two categories - substrate-based security features and printed visual features (including printed security features). For instance, a shadow image is a substrate based security feature as it is created by defining one or more openings in opacifying layers 212 of the substrate 208; and a see-through device 608 is a printed security feature which is printed onto the substrate 208 after it is formed, for example using offset printing.

[0074] The substrate-based security features are formed as part of the substrate manufacturing process as described in method steps 708 to 714, and the printed visual features are printed onto the formed substrate as part of a separate printing process carried out using security printer(s) as described in method steps 706 and 716 to 720. The substrate manufacturing equipment and the security printing equipment may be located in the same facility, or at different facilities.

[0075] At step 706, the printing plates and/or rollers at the security printing facility are designed and prepared based on the security document design created in step 702. In embodiments where the visual features are printed in layers, the design for each printing layer is determined and the printing plates and/or rollers are prepared accordingly. For example, Simultan printing equipment is prepared according to the design of the see-through device 608. In some embodiments, other printing equipment such as intaglio printing equipment may be used to create the see-through device 608. In some embodiments, a commercial offset press may be used.

[0076] At step 708, the opacifying layers 212 are designed at the substrate manufacturing facility. In particular, the shape, size and location of the one or more openings in the opacifying layers 212 required to define a shadow image 602 (which may include additional regions of further reduced opacity 610) are determined.

[0077] At step 710, the transparent base substrate is produced. Typically, the transparent base substrate is produced in reels.

[0078] At step 712, the opacifying layers 212 designed in step 708 are applied to the transparent base substrate to create an opacified substrate defining the shadow images 602.

[0079] At step 714, the opacified substrate defining the shadow images 602 is cut into a plurality of sheets for further processing at the security printer(s).

[0080] At step 716, the see-through device 608 is printed on both sides of each sheet of opacified substrate such that at least a portion of the see-through device 608 overlaps with one or more of the shadow images 602 in the substrate. Other security devices and visual features are also printed onto each sheet of substrate.

[0081 ] At step 718, each sheet of substrate is cut into a plurality of security documents such as banknotes.

[0082] At step 720, the security documents undergo further processing, including piling, sorting and quality checking procedures, for example, to check whether the visual features 604, 606 are printed in substantially perfect registration. Security documents which do not pass the quality checking procedures are removed as spoilage.

[0083] The foregoing embodiments are intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions as will readily occur to those skilled in the art.

[0084] Accordingly, it is to be understood that the scope of the invention is not to be limited to the exact construction and operation described and illustrated, but only by the following claims which are intended to include all suitable modifications and equivalents permitted by the applicable law.

Claims (5)

1. The claims defining the invention are as follows:

   1. A method of producing a security device, the method including creating a region of reduced opacity in a polymer substrate, forming a first visual feature on a first side of the substrate, forming a second visual feature on a second side of the substrate opposite the first side, wherein at least a portion of the first visual feature or the second visual feature overlaps with the region of reduced opacity, and wherein when the substrate is viewed in transmission, the first and second visual features complement one another to form a complete image or a portion of a complete image.
2. 2. A method of claim 1, wherein the step of creating a region of reduced opacity includes reducing a number of opacifying layers in the region.
3. 3. A method according to any one of the preceding claims, wherein the region of reduced opacity defines a shadow image.
4. 4. A method according to any one of the preceding claims, wherein the first and second visual features combined with the region of the reduced opacity defines a complete image.
5. 5. A security document including a region of reduced opacity, a first visual feature on a first side of a polymer substrate, a second visual feature on a second side of the substrate opposite the first side, wherein at least a portion of the first visual feature or the second visual feature overlaps with the region of reduced opacity, and wherein when the substrate is viewed in transmission, the first and second visual features complement one another to form a complete image or a portion of a complete image.