SAFETY DEVICES AND THEIR MANUFACTURING METHOD

Abstract

A security device is described comprising: a substrate having first and second opposing surfaces; on the first surface of the substrate, a surface relief structure formed by one or more cured material(s), at least semi-transparent; and on the second surface of the substrate, a printed layer. In at least a first region of the security device in which at least a portion of the substrate is transparent or translucent, the surface relief structure and the printed layer are each defined according to a common image and aligned with each other, the surface relief structure exhibiting a first set of features of the common image and the printed layer exhibiting a second set of features of the common image.The common image is exhibited by the relief structure of the surface and the printing layer one in combination with the other and the relief structure of the surface provides tactility to the common image.

Description

SAFETY DEVICES AND THEIR MANUFACTURING METHOD CROSS REFERENCE TO RELATED APPLICATIONS The full content of each of the six international patent applications filed on September 10, 2021, on behalf of De La Rué International Limited and claiming priority over the following British patent applications (each filed on September 11, 2020), is hereby incorporated by reference: GB2014325.1, GB2014326.9, GB2014327.7, GB2014328.5, GB2014329.3, GB2014330.1 and GB2014331.9. FIELD OF INVENTION This invention relates to security devices such as those that can be used as a mark of authenticity associated with a valuable object, such as a security document including banknotes, passports, certificates, licenses, and the like. Methods for manufacturing security devices are also described. BACKGROUND OF THE INVENTION Valuables, and particularly valuable documents such as banknotes, checks, passports, identification documents, certificates, and licenses, are frequently targeted by counterfeiters and individuals who wish to create fraudulent copies and / or alter any data contained therein. Typically, such objects are provided with a number of visible security features to verify their authenticity. Examples include features based on one or more patterns such as microtext, fine line patterns, latent images, Venetian blind devices, lenticular devices, moiré interference devices, and moiré magnifying devices, each of which creates a secure visual effect. Other well-known security features include holograms, watermarks, engravings, perforations, and the use of color-changing or luminescent / fluorescent inks.All these devices share the common characteristic that the visual effect they produce is extremely difficult, or impossible, to replicate using readily available reproduction techniques such as photocopying. Security devices that exhibit invisible effects, such as magnetic materials, may also be employed. One type of security feature widely used on banknotes and other documents is intaglio printing. For example, many banknotes in circulation bear an image, such as a portrait or an architectural figure, applied using intaglio printing. Typically, all or part of the image is formed by a series of image elements, such as fine lines or dots, which can be individually distinguished under close inspection and / or magnification. The intaglio printing technique not only ensures high resolution and accurate image reproduction (preventing the production of passable counterfeits using readily available commercial printing techniques) but can also be used to impart a tactile quality to the image.This significantly increases the level of security, since potential counterfeiters may have access to high-precision printing systems that can reproduce the visual appearance of an intaglio print, but not its three-dimensional quality and, therefore, its haptics (feel). Furthermore, due to the nature of intaglio printing, it is difficult to produce images with more than one color, at least in a fully controllable way. Separately, in other classes of safety devices, it is known that molding curable materials (e.g., UV resins) can produce highly tactile effects. However, due to the nature of molding a single resin, the resulting feature will be either colorless or a single color. For enhanced safety, a multi-colored tactile experience would be preferable. BRIEF DESCRIPTION OF THE INVENTION The present invention provides a safety device, comprising: a substrate having a first and a second opposing surfaces; on the first substrate surface, a surface relief structure formed by one or more cured material(s), at least semi-transparent; and on the second substrate surface, a printing layer; wherein, in at least a first region of the security device in which at least a portion of the substrate is transparent or translucent, the surface relief structure and the printing layer are each defined according to a common image and aligned with each other, the surface relief structure exhibits a first set of features of the common image and the printing layer exhibits a second set of features of the common image such that the common image is exhibited by the surface relief structure and the printing layer one in combination with the other and the surface relief structure provides tactility to the common image. The present invention also provides a method of manufacturing a safety device, comprising, in any order or simultaneously: to form a surface relief structure on a first substrate surface from one or more at least semi-transparent curable material(s), and print a print layer on the second substrate surface, wherein, in at least a first region of the safety device in which at least a part of the substrate is transparent or translucent, the surface relief structure and the print layer are each defined according to a common image and aligned with each other, the surface relief structure exhibits a first set of features of the common image and the print layer exhibits a second set of features of the common image, such that the common image is exhibited by the surface relief structure and the print layer one in combination with the other and the surface relief structure provides tactility to the common image. The embodiments of the present invention therefore provide for the tactile etching of a curable material (e.g., a UV-curing resin) on one side of a substrate, which is combined with registered offset printing on the reverse. (The offset printing can be RGB for full-color images if required.) The term offset printing is used herein to refer to lithographic printing, in which the one or more colors to be printed are applied to an embossed printing plate. The ink(s) are then transferred to a blanket roller from which the print is applied to the substrate. However, although lithographic printing is preferred, other printing techniques can also be used to form the printing layer of the present invention, as described below. The present inventors have recognized that the high resolution and complex color rendering achievable in an image printed by lithography or another comparable printing technique cannot be reproduced by intaglio alone, and conversely, that the tactile quality of intaglio cannot be reproduced by lithography alone. By combining a relief structure of the cured surface with a printing layer to display an image in the manner defined above, the resulting security device possesses tactile quality and can simultaneously display any desired arrangement of one or more colors in a controllable and reproducible manner. Since the relief structure of the surface and the printing layer are located on opposite surfaces of the substrate, they can be applied with extremely high registration between them, meaning that their relative positions are the same in every copy of the security device produced.For example, the translational registration between the surface relief structure and the printing layer in the machine direction and / or in the transverse direction is preferably such that any registration error is too small to be seen with the naked eye, for example, no more than + / - 75 µm. The tilt registration between the surface relief structure and the printing layer is preferably 1 degree or less, more preferably 0.1 degrees or less, even more preferably 0.05 degrees or less, with the maximum preference being 0.02 degrees or less. At any lateral location on the substrate, the stages of forming the surface relief structure and printing the printing layer can be performed either sequentially (in any order, with or without intermediate steps) or simultaneously, as described below. The printing layer can be applied using a planographic printing technique (i.e., one that does not induce perceptible tactility), such as offset printing, which can therefore be selected to achieve the desired visual result (such as multiple colors) without the limitations imposed by the intaglio process, while the relief structure of the cured surface provides the desired tactility. This allows not only a greater degree of design freedom but also the creation of more complex security devices with a correspondingly higher level of security. It will be observed that the common image displayed by the security device is formed by the surface relief structure and the printing layer observed in combination (i.e., simultaneously—the surface relief structure is located between the printing layer and the observer, or the printing layer is located between the surface relief structure and the observer). In other words, the common image is a static, composite macro-image that arises due to the spatial arrangement of the surface relief and the printing layer; no synthetic magnification or other optically variable effect is generated by the surface relief. In at least part of the first region (where the common image is displayed), the substrate will be transparent or translucent to allow the combination to be observed in this way.Depending on the optical density of the substrate or any other overlapping layers present, the common image may be visible in reflected light or only in transmitted light. “Transparent” means that the substrate is substantially optically clear, i.e., it causes low or no optical scattering, although it may carry a visibly colored tint. “Translucent” means that some light is able to pass through the substrate, but it will be scattered. If the relevant part of the substrate is translucent, its optical density must be low enough so that both the surface relief structure and the printing layer can be seen simultaneously with the naked eye in transmitted light. Standard paper banknote substrates and standard polymer banknote substrates (with opacifying layers) meet this requirement.At least part of the first region could correspond to a window or half-window region of the substrate (i.e., an area of ​​lower optical density than the rest of the substrate), but this is not essential, as described below. In some embodiments, the substrate is transparent or translucent along the first region of the safety device. The entire substrate can also be transparent or translucent if desired. It should be noted that molding for tactile feedback differs from simple tactile printing due to the presence of a base layer that affects the color of the device (whether clear, tinted, or pigmented). In other words, the relief structure of the molded surface will comprise a continuous body of cured material (of one or more types) with a variable height profile. If, for example, it includes raised protrusions, these will be connected by a lower base layer. This would not be the case in a product with tactile protrusions formed by local printing of the material. The continuous nature of the molded relief structure must be considered in the design of the safety device to achieve the desired optical effect, as described below. The surface relief structure and the printing layer each exhibit a set of common image features (in other words, at least part of the common image). Common image features define the information content of the common image and can include any of: lines or edges that delimit objects in the image; the objects themselves; contour or shaded regions; shapes or parts thereof; alphanumeric characters or symbols, or parts thereof, etc. The nature of the features will depend on the image content. Examples will follow. The surface relief structure and the printing layer can contribute to the common image to varying relative extents, depending on the modality. In some preferred implementations, it may be desirable for each of the two security device components to display the entire common image; that is, for both the surface relief structure and the printing layer to define the same image for each other. In this case, the first and second sets of features are identical, and both the surface relief structure and the printing layer exhibit all the features of the common image. It will be noted that the surface relief structure and the printing layer will be in overlapping alignment so that the corresponding features have the same lateral position within the security device on both components. In other preferred embodiments, the first and second sets of features are distinct from each other, or the first and / or second sets of features are subsets of the common image features. In other words, the surface relief structure may exhibit a first part of the common image, and the print layer a second part, with these parts differing from each other and potentially separable, overlapping, or interleaved. Thus, in one example, the print layer may exhibit the complete common image, and the surface relief structure only a portion of it—or vice versa. Alternatively, each constituent may exhibit only a portion of the common image, with the complete image only becoming apparent when the two are combined.Preferably, one or more of the common image features are included in both the first and second sets of features and are displayed in both the surface relief structure and the print layer. Again, it will be noted that the surface relief structure and the print layer will be in overlapping alignment so that the corresponding features have the same lateral position within the security device in both components. The selection of the features to which the surface relief structure will contribute and those to which the printing layer will contribute could be decided in a variety of ways. In some cases, the division could be arbitrary. However, in the preferred examples, the first set of features consists of the features of the common image located in a first portion of it, and the second set of features of the common image consists of the features of the common image located in a second portion of it. The first and second portions are distinct from each other, preferably offset laterally from one another. The first and second portions are preferably each a single contiguous area of ​​the image. For example, the first portion could correspond to the entire lateral extent of the common image, while the second portion is only a sub-area of ​​it (or vice versa).Laterally displaced includes portions that are (only) partially overlapping or not overlapping at all (for example, the first and second portions may be separate or adjacent). For example, the surface relief structure could contribute one half of the common image, and the print layer the other half. These principles can be used to design security devices with visual and tactile effects that interact with each other in unexpected ways. For example, a user might expect the tactile region(s) of the device to match the visible features of the device. However, the device could be designed so that this is not the case, and there could be an intentional mismatch between the two components—for example, a selected visible sub-portion of the device could be configured without tactile feedback, or a tactile sub-portion could be located in a position without any visible contribution from the printing layer. These are memorable and distinctive features that would likely go unnoticed by potential counterfeiters. In still other configurations, the first set of features preferably corresponds to a first color component of the common image, and the second set of features preferably corresponds to at least a second color component of the common image. In this case, the overall extent of the two constituents may overlap considerably, but on a microscale, the configuration of each will vary to contribute the desired color(s) to each point of the common image. Preferably or: the first set of common image features, which is exhibited by the surface relief structure, preferably the entire surface relief structure, is located laterally in its entirety within the limits of the second set of common image features, which is exhibited by the printing layer; and / or the second set of common image features, which is exhibited by the printing layer, preferably the entire printing layer, is located laterally in its entirety within the limits of the second set of common image features, which is exhibited by the surface relief structure. Both of these options cover the scenario where the surface relief structure and the print layer share the same boundary. It should be noted that the surface relief structure and / or the print layer could extend beyond the common image (this applies to all modes), but in such cases, they will be configured differently outside the common image so that the common image remains distinct. Examples will be provided below. In other implementations, it may be preferable for the surface relief structure and / or the print layer not to exist outside the common image for greater visual distinction. In some implementations, the relief structure of the molded surface (or part of it) could be one or more unique volumes of material raised above the base layer, each defining a surface that varies in height optionally continuously, gradually, or in steps. However, in other cases, the relief structure of the surface may comprise multiple discrete raised portions. In preferred embodiments, the common image is defined, at least in part, by a series of distinct image elements, such as: The surface relief structure comprises a plurality of separate raised elements that form the image elements that define the first set of common image features; and / or the printing layer comprises a plurality of separate printing elements that form the image elements that define the second set of common image features. The formation of a common image from a series of image elements allows the security device to more closely mimic a conventional intaglio print, since intaglio images typically comprise in-line work figures or other halftone work. The image elements are visually distinguishable from one another, although this may require close inspection and / or low-level magnification to differentiate them. The image elements can be conveyed by either or both of the surface relief structure and the printing layer. If both, the corresponding image elements defined within each constituent will be in overlapping alignment. Preferably, the common image is a halftone image. The image elements vary throughout the series in terms of their size, shape, color, optical density, and / or spacing. To convey the common image, the series of image elements is preferably arranged on a regular grid. The image elements may advantageously be rectilinear or curvilinear line elements, dot elements, or elements that have the form of coded marks, preferably alphanumeric or typographic symbols (e.g., currency symbols such as , etc.). For example, the image elements could define a line work (e.g., similar to a conventional line print) or a screen of dots of image elements, such as a halftone screen. The image may comprise a guilloche pattern. Conveniently, the image is a portrait or an architectural figure. Preferably, the image is of a 3D object or scene.In the modes where the image is a halftone image, the image elements are preferably arranged in a regular grid, although in general the elements may or may not be arranged in a regular grid. As mentioned previously, the relief structure of the molded-cured surface will comprise a continuous body of cured material with a variable-height profile. The specific profile will depend on the desired image and / or tactility pattern. In preferred implementations, the surface relief structure includes a plurality of separate protrusions, joined together by a lower-height base layer. The protrusions may correspond, for example, to image elements of the common image just described. Advantageously, the base layer may extend (away from the common image) over a peripheral region surrounding the plurality of separate protrusions. Typically, any such peripheral region will be narrow, for example, extending between 0.01 mm and 5 mm away from the edge of the common image.In preferred examples, the ratio of the height of at least one protrusion to the height of the base layer joining the raised element to an adjacent protrusion is at least 10, preferably at least 20, and is preferably no greater than 400, preferably no greater than 200. In some embodiments, the ratio of the height of each protrusion to the height of the base layer is at least 10, preferably at least 20, and is preferably no greater than 400, preferably no greater than 200. This is especially the case when the protrusions are configured to form image elements, particularly multitonal images. The haptic effects of the security device can also be configured to interact with other tactile elements on the security document. For example, the described security device could be provided on a document substrate that also bears a conventional intaglio feature, which is arranged on the same substrate surface as the surface relief structure formed from cured material (for example, the two could be adjacent to each other). The overall appearance formed by the described security device and the intaglio printing in combination can be a complex haptic image, with the less complex images, tactility, and color provided by the intaglio feature, while the more complex images, tactility, and color are provided by the described security device.For example, the described device may present a common image in the form of a photographic portrait, while the intaglio printing may provide a patterned background (of relatively low complexity) surrounding the portrait background, for example, in the form of a structure of thick intaglio lines. As mentioned at the outset, some of the advantages of the invention are providing greater design freedom in terms of the color(s) displayed by the device and improved color placement. That is, instead of applying large blocks of each color (as in conventional intaglio printing), individual lines or dots in an image could each have a different color if desired. Possible implementations in preferred modalities include: Color combinations using a tinted or pigmented UV molding resin. The tinted resin can be combined with offset colors to produce 4, 5, or 6 colors. The tinted resin could be etched at different heights to increase / decrease the color intensity for better definition / color combination hi O7nn / C7n7 / B / vi The stock image can be of any type, including blocks of color / shapes, alphanumeric text, or macro images without fine detail. However, it is preferable for the stock image to be multi-tonal and / or multicolored, with the highest preference being a grayscale or full-color image. Such images can mimic or even improve upon the appearance of conventional intaglio prints. In many preferred implementations, at least one curable material is colorless (under standard white lighting, to the naked eye), and the print layer exhibits one or more visible colors. Ideally, the print layer is either RGB (red, green, blue) or CMYK (cyan, magenta, yellow, black). However, other color combinations, such as orange, green, and violet, can also be used. It should be understood that the print layer can be set in one or multiple print jobs (this applies to all modes). In other preferred implementations, at least one curable material carries a dye of a first color, and the print layer exhibits at least the first color and / or a (different) second color, preferably configured so that when viewed in combination, a multicolored version of the common image is visible. It should be noted that the surface relief structure could, if desired, be formed from multiple curable materials, each forming a different side portion of the structure, and these materials could carry different colored dyes to introduce a greater level of complexity. It is also possible for the print layer to exhibit more than two different colors. In a particularly preferred embodiment, the first color is one of red, green, and blue, and the printing layer displays the other two of red, green, and blue, so that when viewed in combination, a full-color version of the common image is visible. In another particularly preferred embodiment, the first color is one of cyan, magenta, yellow, and black, and the printing layer displays the other three of cyan, magenta, yellow, and black, so that when viewed in combination, a full-color version of the common image is visible. Advantageously, the printing layer exhibits two areas of different respective colors and an intermediate area in which the color gradually transitions between them, preferably in a way that is continuous even under magnification. This achieves a visual effect similar to the "rainbow" in conventional security lithographic printing, but with the added benefit of tactile sensitivity. The "rainbow" effect is not possible with conventional intaglio printing because the viscous nature of intaglio inks prevents them from intermixing, as does their placement within the recesses of the intaglio printing plate. Therefore, it has not previously been possible to produce a tactile image with rainbow colors, and this method thus provides a novel security effect that cannot be achieved by conventional means. The surface relief structure and the print layer could be configured to visually blend, exhibiting the same appearance regardless of the viewing side of the device (i.e., the surface relief structure side or the print layer side). However, in other preferred embodiments, it may be desirable to produce different appearances, one visible from each side. In this case, the common image will be displayed on at least one side of the device. For example, in a preferred embodiment, the at least one curable material carries a dye of at least one color, and the print layer has a visual opacity such that the color appearance of the common image differs when the security device is viewed from the surface relief structure side compared to when viewed from the print layer side.In other words, the printing layer is opaque enough to block the visibility of the surface relief structure through it, leading to the different appearance. The printing layer could be applied using standard visible-colored ink(s). To further enhance security, in other embodiments, the printing layer may comprise one or more substances sensitive to non-visible wavelength(s), preferably UV or IR. Optionally, the printing layer is invisible under white light. For example, the printing layer could comprise a pair of inks that appear to match under one lighting condition (e.g., white light) and different under another (e.g., UV light). Examples of suitable materials from which the printing layer can be formed are described in WO-A-2004 / U50376 and WO-A-2018 / 206936.In other examples, the printing layer may comprise substances that emit red, green, and blue light when illuminated by a corresponding excitation waveband, so that a full-color version of the common image is displayed. Examples of suitable substances are described in WO-A-2020 / 030893. The variation in height (and / or other dimensions / shape) of the cured material along the surface relief structure could be arbitrary or otherwise unrelated to the common image (the first set of features is primarily conveyed by the lateral configuration of the surface relief rather than its height). For example, the features The elements of the common image displayed by the surface relief structure could all be conveyed by raised protrusions of equal height, separated by a base layer. However, in preferred embodiments, the height, width, length, and / or geometry of the surface relief structure varies according to the common image. For example, this can be used to link the tactile sensation of the surface relief structure to certain parts of the common image or to emphasize a three-dimensional quality of the image. In one example, the common image could represent a three-dimensional object, such as a portrait of a person, with features corresponding to parts of the object closer to the observer corresponding to portions of the surface relief structure with greater height, and vice versa.The surface relief could comprise a single raised element of variable height, or multiple discrete elements that have different heights from each other and / or have a height that varies within an element. As mentioned previously, one or both components of the security device may be used to provide additional visual effects (preferably additional security effects) beyond those provided by the common image. For example, one or both components may extend beyond the common image if desired. Therefore, in some preferred embodiments, the security device further comprises a second region in which one or both of the surface relief structure and the printing layer are present. This second region is either laterally offset and does not overlap with the first region, or interlocked with the first region. In the second region, the surface relief structure and / or the printing layer have respective configurations different from their arrangements in the first region, so that the common image remains visibly distinct from the second region.For example, the surface relief structure and the impression layer do not preferentially exhibit matching aligned features in the second region. There is no common static image exhibited by the two constituents in the second region (unlike the first region). It should be noted that the surface relief structure and / or the printing layer may or may not be continuous between the first and second regions of the security device. For example, there may be a gap between the surface relief structure in the first region and that of the second region. However, the entire surface relief structure (in both regions) will be produced in the same pass and from the same molding tool, preferably from the same curable material. The first and second regions may ultimately be arranged in one and the same window region (or half-window) on a security document, or they may each be arranged in a different respective window region (or half-window). In the latter cases, the respective window regions (or half-windows) will be separated from each other by a less translucent area of ​​the security document. In preferred embodiments, the surface relief structure is present in the second region and forms any of: one or more optical elements such as focusing elements, facets, prisms, pyramids, or caustic elements (preferably an array of such optical elements); a tactile structure; or a matte structure. Advantageously, the printing layer is present in the second region and forms any of: a background print, a visually uniform area, a color-shifting layer, a printed color filter, or an image array such as a series of micro-images or an interlaced image. Providing the printing layer in the form of a color-shifting layer is particularly advantageous when the surface relief structure comprises an array of prisms and the color-shifting layer is configured to interact with the prism array.Examples of suitable color-change layers that can be printed include layers incorporating liquid crystals (e.g., a liquid crystal pigment), interference pigments (including magnetically oriented interference pigments), pearlescent pigments, or photonic pigments. It is particularly advantageous if, in the second region, the surface relief structure forms a series of focal points, and the printing layer forms a series of images located approximately on the focal plane of these focal points. The series of focal points and the series of images are then configured to cooperate with each other to generate an optically variable effect. In this way, an additional, optically variable security device can be applied to the substrate during the same manufacturing stages as the security device already described. Optically variable means that the device's appearance differs from different viewing angles, making it impossible to replicate by standard copying (e.g., photocopying or scanning). The invention also provides a plurality of substantially identical safety devices, each as described above, in each of which the respective surface relief structures and printing layers have the same position relative to each other. This is because the two constituents are precisely registered against each other during manufacturing. By “same position” it is understood that the relative position of the respective surface relief structures and printing layers varies by an amount less than, if at all, than can be detected by the naked eye between the safety devices. For example, the translational variation in the machine or transverse direction can be + / - 75 mm or less. The tilt variation is preferably 1 degree or less, more preferably 0.1 degrees or less, even more preferably 0.05 degrees or less, with the maximum preference being 0.0.2 degrees or less. The plurality of security devices will typically be produced sequentially on the same manufacturing line and according to the same design; for example, the plurality may include an entire batch of security devices or the entirety of a print run. The plurality may include at least 10 security devices, preferably at least 100. Each security device in the plurality may ultimately be located on a different security document. In preferred methods for manufacturing safety devices according to the invention, the formation of the surface relief structure and the printing of the printing layer are performed in register with each other. Again, preferably any registration error is smaller than what is visible to the naked eye. For example, the translational registration in the machine or transverse direction can be + / - 75 µm or less. The tilt registration is preferably 1 degree or less, more preferably 0.1 degrees or less, even more preferably 0.05 degrees or less, with the maximum preference being 0.02 degrees or less. This is preferably achieved by performing both stages in an in-line process on the same apparatus. The substrate could be processed in the form of a grid, but more preferably in the form of separate sheets when the two stages are performed.Ideally, the formation of the surface relief structure and the printing of the printing layer are simultaneous, occurring at the same position along the machine's direction. This achieves the highest level of registration between the two constituent parts of the security device, as there can be no slippage or distortion of the substrate after one stage and before the other (since there is no interval between them). Apparatus suitable for performing simultaneous mold curing and printing on opposite sides of a substrate is described in WO-A-2018 / 153840 and WO-A-2017 / 009616. The level of registration achievable through simultaneous molding and printing using the apparatus described therein cannot be attained on a rotary press or in two separate processes. The print layer can be applied using any selected printing technique that can achieve the desired resolution and number of colors. Typically, a planographic printing technique will be selected, i.e., one that does not engrave the substrate. In the preferred hi O7nn / C7n7 / B / vi modes, the print layer is printed using lithographic printing, but alternatively, other printing methods such as flexographic, screen printing, gravure, or micro-intaglio printing (none of which involve etching the substrate) could be used. It should be understood that the print layer could comprise multiple print jobs, set up sequentially or (preferably) simultaneously, for example, from a pickup roller or blanket. Each print job can potentially be formed from a different material (e.g., a different ink color). Preferably, the surface relief structure is formed by mold curing one or more at least semi-transparent curable materials onto the first substrate surface. In preferred embodiments, the surface relief structure is mold cured by: provide a molding tool that has a defined mold relief thereon that corresponds to the relief structure of the surface; apply one or more curable material(s) that are at least semi-transparent to the molding tool or substrate; to bring the molding tool and the substrate into contact with one or more at least semi-transparent curable materials between them, in order to form (i.e., shape) the at least semi-transparent curable materials into the relief structure of the surface; and during and / or after contact, to cure the at least semi-transparent curable materials to retain the relief structure of the surface. The curing method will depend on the type of curable material used. In the preferred examples, the material is radiation-curable (e.g., UV-curable), and the curing step(s) will involve irradiating the material with radiation of an appropriate wavelength to induce crosslinking of the material. In many preferred implementations, at least the semi-transparent curable material(s) is / are applied to the mold relief of the molding tool to substantially fill the recesses of the mold relief and form a layer of at least the semi-transparent curable material(s) over the raised areas of the relief structure. Substantially the entire body of curable material (including the portions within the recesses and the layer over the raised areas) will cure and transfer onto the substrate. In such implementations, there is no cleaning or scraping step that would otherwise remove the curable material(s) from the raised areas. However, in alternative examples, the curable material(s) may be applied only to the recesses of the relief structure of the molding tool, preferably through the use of a removable means such as a scraper, and the method further comprises, subsequent to the application of one or more cured materials to the relief structure and before joining the substrate and the molding tool, applying an additional layer of another curable material(s) to substantially the entire surface of the molding tool to improve the retention of the cured material(s) on the substrate. In such examples, the additional layer acts to improve the adhesion of the curable material(s) located only within the recesses of the relief structure of the molding tool to the substrate.Because the additional layer is applied substantially to the entire surface of the molding tool (i.e., over the filled recesses of the relief structure on the tool surface and the rises between them), the resulting surface relief structure comprises an integral base layer as described above. The curable material of the additional layer may be the same curable material or materials used to form the elements of the surface relief structure, or it may be a different curable material. The manufacturing method can be configured to provide the safety device with any of the preferred features described above. The present invention further provides a security document comprising a document substrate and a security device thereon, the security device conforming to any of the preceding claims, wherein the document substrate may or may not act as the security device substrate, the document substrate preferably comprising paper, polymer, cellulose, or a hybrid thereof. For example, WO-A-2020156655 describes a suitable substrate material formed from regenerated cellulose. It should be understood that the security document could therefore include a single substrate, which acts both as the document substrate (i.e., the self-supporting sheet forming the body of the document) and as the security device substrate (i.e., the one bearing the surface relief structure on one surface and the printing layer on the other).In this case, the document substrate must be transparent or translucent, at least in the location of the security device. The entire document substrate may be sufficiently translucent for this purpose, or it may include a window / half-window region for this reason. Alternatively, the security document could comprise two substrates: a document substrate and a security device substrate that carries the security device and is attached to or incorporated into the document substrate. In this case, the document substrate could be transparent, translucent, or opaque. The common image could be located anywhere on the security document—fully within or outside a window / half-window region (if one is provided), or partially within and partially outside a window / half-window region (if one is provided). In preferred embodiments, the first region of the security device is located at least partially within a window or half-window region of the document substrate, which has a lower optical density than the surrounding environment. In other preferred embodiments, the document substrate is translucent, and the first region of the security device is located at least partially within a non-windowed region of the document substrate.In cases where the security feature is not formed directly onto the document substrate, the security feature substrate is preferably affixed to or incorporated into the document substrate, preferably over a transparent or translucent region of the document substrate that is optionally formed as an opening. The appearance of the common image may differ in reflected versus transmitted light, and / or from any side of the security document. In preferred implementations, this may be influenced by the opacity of the security document at the location of the security feature. For example, parts of the same security feature may present different sets of appearances depending on whether they are located in a window (transparent) region, a half-window (highly) translucent region, or a windowless (less translucent or opaque) region.This can be used to create a more complex combination of appearances by providing several of these different arrangements in a security document. Therefore, preferably, the first region includes parts that are located respectively in at least two of: a window region of the document substrate, a half-window region of the document substrate, and a non-window region of the document substrate. Similarly, it may be advantageous to provide more than one security device of the type described above in a security document to achieve a more complex combined effect. Preferably, therefore, the security document comprises at least two security devices, each as described above, wherein the at least two security devices are located respectively at least partially in at least two of: a window region of the document substrate, a half-window region of the document substrate, and a non-window region of the document substrate. The document substrate can be of any type, including fibrous substrates such as hi O7nn / C7n7 / B / vi paper or cellulose (for example, as described in WO-A-2020156655) or non-fibrous substrates such as polymer (or a hybrid of both). In preferred examples, the document substrate comprises a core polymer substrate with at least one opacifying layer disposed on one or both surfaces of the core polymer substrate, optional gaps in one or more of the opacifying layers forming window or half-window regions of the document substrate. For example, the security document could be a polymer banknote. The opacifying layers are preferably made of non-fibrous materials, such as a binder coating containing light-scattering pigments, preferably white, off-white, or gray (such as TiCb). In some embodiments, the document substrate may also comprise an integral print mark, preferably located between at least one of the opacifying layers and the core polymer substrate. These print marks (unlike the print layer described above) are incorporated into the substrate during its production rather than during its subsequent processing into security documents. For example, the print mark may be applied during the same process by which the opacifying layers are applied, such as gravure printing. The print mark is integral to the document substrate. The integral print mark may not be related to the security device currently described.However, preferably, the integral print mark is defined according to the common image and aligns with the surface relief structure and the printing layer. The integral print mark exhibits a third set of characteristics of the common image, such that the common image is exhibited by the surface relief structure, the printing layer, and the integral print mark in combination with one another. In another embodiment, the print mark may exhibit another copy of the common image (or a version of it, for example, the same image but in a different color) but does not align with the security feature; for example, it could be located elsewhere on the security document. This allows for easy verification between the print mark and the security feature. Preferably, the security document is any of: a banknote, passport, identification document, ID card, bank card, driver's license, visa, stamp, check or certificate. The invention further provides a method for manufacturing a security document, comprising providing a document substrate and either forming a security device on the document substrate or forming a security device on a security device substrate, and then applying the security device substrate or incorporating the security device substrate into the document substrate, in each case by using the method described above for manufacturing the security device. The method can be configured to provide the security document with any of the preferred features described above. BRIEF DESCRIPTION OF THE FIGURES The following will describe examples of safety devices and safety documents according to the present invention, as well as methods for their manufacture, with reference to the accompanying Figures, in which: Figures 1(a) and 1(b) show a comparative example of a security document in plan view and cross section respectively, Figure 1(c) shows an enlarged detail of the cross section of Figure 1(b); Figures 2(a) and 2(b) show a first modality of a security document having a security device according to the invention, in plan view and cross section respectively; Figures 3(a), 3(b), 4(a) and 4(b) show additional modalities of safety devices according to the invention, each in cross-section and plan view; Figures 5(a) to 5(c) show three variants of an additional modality of a safety device according to the invention, each in cross-section and plan view; Figure 6(a) shows another modality of a safety device in cross section, with Figures 6(b), 6(c) and 6(d) representing three different variants of the print layer in plan view; Figure 7 shows an additional modality of a safety device according to the invention, in cross-section and plan view; Figure 8 schematically represents another example of a safety device according to the invention, in an exploded view; Figure 9(a) shows an additional embodiment of a safety device according to the invention in cross-section and plan view, Figure 9(b) shows an exploded view of the safety device; Figure 10(a) shows an additional embodiment of a safety device according to the invention in cross-section and plan view, Figure 10(b) shows an exploded view of the safety device; Figure 11 shows an additional embodiment of a safety device according to the invention in cross-section and plan view; Figures 12 to 14 show additional modes of safety devices according to the invention, each in cross-section and plan view; Figure 15(a) shows an additional embodiment of a safety device according to the invention in cross-section and plan view, Figures 15(b) and 15(c) show plan views of the surface relief structure and the printing layer, respectively; Figures 16(a), 16(b) and 16(c) show additional embodiments of safety devices according to the invention, each in (i) plan view and (ii) cross-section; Figures 17(a) to 17(d) show another embodiment of a safety device according to the invention, (17a) in plan view, (17b) in cross section, Figures 17(c) and 17(d) show enlarged details; Figures 18(a) to 18(e) and 19 to 24 show additional embodiments of safety devices according to the invention, each in cross-section and plan view; Figure 25 schematically represents another example of a safety device according to the invention, in an exploded view; Figure 26(a) shows an additional embodiment of a safety device according to the invention in cross-section and plan view, Figure 26(b) shows an exploded view of the safety device; Figure 27(a) shows an existing intermediate product during a process to make a modality of a safety device, in cross section and plan view, and Figure 27(b) shows the finished safety device, in cross section and plan view; Figures 28(a), 28(b), 28(c) and 28(d) show four additional modes of safety devices according to the present invention, in cross section; Figures 29(a), 29(b) and 29(c) show three additional modes of safety devices according to the present invention, each in cross-section and plan view; Figures 30(a), 30(b) and 30(c) show three additional modes of safety devices according to the present invention, in cross section; Figure 31 schematically represents another example of a safety device according to the invention, in an exploded view; Figures 32(a) to 32(g) show additional modes of safety devices according to the present invention; Figure 33 shows another modality of a safety device according to the present invention, in cross section; Figures 34(a), 34(b) and 34(c) show three types of security documents having security devices according to the present invention, in cross section; Figure 35(a) shows an embodiment of a safety device according to the present invention, in cross section, and Figure 35(b) shows (i) the appearance of the safety device as seen in the light reflected from the observer's position Oi, and (ii) the appearance of the safety device as seen in the transmitted light; Figure 36(a) shows an embodiment of a safety device according to the present invention, in cross section, and Figure 36(b) shows (i) the appearance of the safety device as seen in the light reflected from the observer's position Oi, and (ii) the appearance of the safety device as seen in the transmitted light; Figure 37(a) shows an embodiment of a security document having three security devices, each according to the present invention, in cross section; Figure 37(b) shows (i) the appearance of the security device as seen in light reflected from observer position Oj, and (ii) the appearance of the security device as seen in light transmitted from observer position Oi; and Figure 37(c) shows (i) the appearance of the security device as seen in light reflected from observer position O-2, and (ii) the appearance of the security device as seen in light transmitted from observer position O?; Figures 38(a), 38(b) and 38(c) show three variants of an additional embodiment of a safety device according to the present invention, in cross section, and Figure 38(d) shows (i) the appearance of the safety device in the light reflected from the observer's position Oi, and (ii) the appearance of the safety device in the transmitted light; Figure 39(a) schematically represents another example of a safety device according to the invention, in an exploded view, and Figure 39(b) shows (i) the appearance of the safety device in the light reflected from the observer's position Oi, and (ii) the appearance of the safety device in the transmitted light; Figure 40(a) shows an embodiment of a safety device according to the present invention, in cross section; Figure 40(b) shows (i) the appearance of the safety device as seen in the light reflected from the observer position Oi, (ii) the appearance of the safety device as seen in the light transmitted from the observer position O-i; and (iii) the appearance of the safety device as seen in the light reflected from the observer position O-2; Figure 41(a) schematically represents another example of a safety device according to the invention, in cross section, and Figure 41(b) shows (i) the appearance of the safety device in the light reflected from the observer's position Oi, and (ii) the appearance of the safety device in the transmitted light; Figure 42 shows an additional modality of a safety device according to the present invention, each in cross-section and plan view; Figures 43(a), 43(b), 43(c) and 43(d) show four additional modes of safety devices according to the present invention, each in cross-section and plan view; Figure 44(a) schematically represents another example of a safety device according to the invention, in an exploded view, and Figure 44(b) shows (i) the appearance of the safety device under a first lighting condition, and (ii) the appearance of the safety device under a second lighting condition; Figures 45(a), 45(b) and 45(c) show three additional modes of safety devices according to the present invention, each in cross-section and plan view; Figure 46(a) schematically represents an illustrative apparatus suitable for mold curing a surface relief structure in the embodiments of the invention, Figure 46(b) illustrates the formation of the surface relief structure in perspective view; Figures 47 and 48 schematically represent two illustrative apparatuses for use in the embodiments of the invention for forming the surface relief structure and the printing layer simultaneously; and Figure 49 schematically represents an additional example of apparatus for use in the embodiments of the invention. DETAILED DESCRIPTION OF THE FIGURES The following description will focus on security features formed directly onto document substrates ultimately used as the basis for security documents such as banknotes, passports, certificates, licenses, ID documents, and the like. In many cases, the security feature is depicted as being arranged in a window region of the document substrate. However, as will be explained with reference to Figures 32(a)–32(g), this is not essential, and the feature could alternatively or additionally be located in a half-window or windowless region (or any combination of such regions). Similarly, as will be explained with reference to Figures 34(a)–34(c), all forms of the security feature could alternatively be formed on a separate substrate to which a security document is applied (or incorporated).The security device could be formed on the separated substrate before and / or after it is joined to the security document substrate. For comparison, Figures 1(a)–1(c) show an example of a conventional security feature in the form of an intaglio print 110 on a security document 100. Figure 1(a) shows the security document 100 in plan view, and Figure 1(b) shows a schematic cross-section along line Q–Q’. It should be noted that, for simplicity, Figure 1(b) does not show the engraved nature of the substrate created by the intaglio print, which will be present in practice. This is shown in the enlarged detail of Figure 1(c). In this example, the intaglio print is shown formed on a document substrate 2 consisting of an inner core substrate 2a, which may be a polymer material such as BOPP, and outer opacifying layers 2b, such as white ink. This is a typical construction for a polymer banknote substrate.However, 110 intaglio prints can be formed on any document substrate, including paper substrates. As shown in Figure 1(a), the intaglio print 110 comprises an in-line working image of a kingfisher and a line of text reading “De La Rué” with a logo above it. The kingfisher image is multitonal and is composed of a series of image elements 112 in the form of separate inked lines of varying size and shape, configured as needed to convey the image characteristics. The image is formed in two colors: Ci (e.g., dark green) and Cz (e.g., orange). The intaglio process involves providing a printing plate on which all the lines defining the desired image elements are engraved. A first ink 114a of color Ci and a second ink 114b of color Cz are applied to respective regions of the printing plate corresponding to the areas where the two colors are required.The inks are forced into the engraved lines and cleaned from the intervening surfaces of the plate using a cleaning brush or similar tool. The printing plate is then pressed against a high-pressure printing roller onto a substrate 2, forcing the substrate 2 into the engraved lines, thereby etching the substrate. After separation, the inks 114a and 114b are transferred from the printing plate to the raised elements of the now-etched substrate 2. The raised elements and the inks carried on them form the image elements 112 of the intaglio print 110. The etched nature of the print 110 results in a tactile quality. While it is possible to create an intaglio print with more than one color, as illustrated in Figures 1(a)–1(c), design options are limited. Due to the composition of intaglio inks (which are very thick and paste-like) and the method of applying the ink to the intaglio plate, placing individual inks on the plate is very difficult. The high pressure required to force the thick ink paste into the recesses of the intaglio plate before printing makes the process difficult to control and limits the placement of individual inks to blocks (groups) of recesses rather than individual recesses. The ink will invariably disperse when forced into the recesses and will merge with the adjacent inks. The sweeping effect of cleaning the non-recessed areas of the plate as part of the intaglio process also contributes to merging.For these reasons, each color area either needs to be large enough so that the blended regions are a small part of the entire printed area (to appear as a single color to the viewer) or sufficiently separated from the other colors to minimize blending. As such, it is not possible to place different colors very close to one another or to arrange different colors at high resolution as would be required to display a full-color, photographic-quality image, for example. The number of colors that can be displayed in an image is also limited, since it is not possible to spatially combine the inks in the controlled manner necessary to provide the full color spectrum through additive or subtractive color mixing. Figures 2(a)-2(b) show a first embodiment of a security document 100 having a security device 10 according to the present invention. Again, in this example, the document substrate 2 is shown as a multilayer substrate having a polymer core substrate 2a, which is transparent (e.g., BOPP), and opacifying layers 2b on either side. The security device 10 is positioned in a window region 51 of the substrate where the opacifying layers 2b are absent on both sides. However, this is not essential, and the security device 10 could be formed on any type of substrate and (e.g.) in a window region 51 or a windowless region 50, provided there is sufficient transparency / translucency, as explained below. Other arrangements will also be exemplified below. The safety device 10 comprises a surface relief structure 20 and a printing layer 30 that overlap and register against each other. The surface relief structure 20 is formed from a body of cured material 20a having a variable height profile (parallel to the z-axis) yhi O7nn / C7n7 / B / vi, which is disposed on a first surface 3a of the substrate 2. The surface relief structure may comprise a single raised element or multiple discrete raised elements. In this example, the cured material 20a forming the surface relief structure 20 is transparent and colorless. The printing layer 30 is a flat print disposed on the second opposite surface 3b of the substrate 2. The printing layer 30 may be single-color or multi-color. In this example, it is formed from two materials 30a, 30b (e.g., inks) having different respective colors Ci and C2.In a first Ri region of the substrate, the surface relief structure 20 and the impression layer 30 are each configured so that in combination they exhibit a common image, i.e., a composite macro-image, which here is the same online working image of a kingfisher described in relation to Figures 1(a)-1(c). This image is composed of a series of separate image elements 11 that vary in size, shape, and / or spacing along the series to carry the multitonal image features (e.g., the kingfisher's head, beak, eye, body, number 50, etc.). The image elements 11 are preferably of such a size that they are individually distinguishable under close inspection or low magnification (e.g., at least 50 pm, more preferably at least 150 pm wide). In this example, both the relief structure of surface 20 and the print layer 30 are each configured to exhibit all the features of the common image. As such, each is configured to exhibit the entire desired series of image elements 11, and each is defined according to one and the same image. In the relief structure of surface 20, the image elements 11 are defined by the corresponding raised elements (protrusions) 21, and in the print layer 30, the image elements 11 are defined by the corresponding print elements 31. The two constituents (i.e., the relief structure of surface 10 and the print layer 30) are positioned relative to each other so that each raised element 21 aligns over one of the print elements 31.Therefore, when viewed in combination, the printing layer 30 gives color to the common image, while the relief structure of surface 20 provides tactility and contributes to its appearance (even when formed by a clear colorless material, the reflective surface of the relief structure of surface 20 will be apparent). It will be seen in Figure 2(b) that the raised elements 21 of the surface relief structure 20 are joined together by a base layer 29 of the same cured material 20a, which extends between each of the raised elements 21 and around the periphery of the surface relief structure 20 (typically for only a small distance, for example, from 0.01 mm to 5 mm). The base layer 29 is an artifact of the mold-curing process by which the surface relief structure 20 is formed. The height of the base layer 29 can be varied along the safety device 10 if desired. The modality of Figures 2(a)-2(b) results in a security device 10 that mimics the appearance and tactile feel of the intaglio print 110 described with reference to Figures 1(a)-1(c), although it is formed by a different method and has a different structure. However, since the print layer 20 can now be applied by a planographic printing process (such as offset), it can be formed at a higher resolution and display any number of colors with a much better achievable color placement than is possible in an intaglio print. This means that design freedom is considerably increased, allowing for a greater variety of visual effects and more complex designs (and thus a higher level of security), as will be described below. While many implementations may select a complex common image (such as the kingfisher shown in Figures 1(a) to 2(b), or a portrait, photograph, etc.), the technique described herein is equally suitable for displaying simpler images, such as geometric shapes, logos, alphanumeric text, typographic symbols, and the like. The common image may or may not comprise a series of separate image elements, as in the example above. Thus, Figure 3(a) illustrates one embodiment of a security device 10 in which the common image features the digit “5,” conveyed by a single continuous block in the required shape. The image is sized to be easily readable by the naked eye, for example, several millimeters wide.As before, the security device 10 comprises a surface relief structure 20 formed from a transparent curable material 20a on a substrate surface 3a 2, and a printing layer 30 formed from an ink 30a (e.g., red ink) on the opposite surface 3b. Both the surface relief structure 20 and the printing layer 30 are configured to exhibit the same feature, specifically, the digit 5, in overlapping alignment with each other. The surface relief structure 20 comprises a raised protrusion 28 having a lateral extension corresponding to the shape of the digit 5 ​​and surrounded by a base layer 29 extending around its periphery. The printing layer 30 likewise comprises a continuous area of ​​ink 30a having the same lateral extension as the raised protrusion 28 in the shape of the digit 5. In combination, the relief structure of surface 20 and the printing layer 30 thus display a common CI image in the form of a uniformly colored digit “5” (labeled with reference numeral 18 in Figure 3(a)) with a surrounding colorless peripheral region 19, corresponding to the base layer 29. Since there is an inherent limitation on the lateral size of individual intaglio elements (a limitation not found in the present invention), the resulting security device can be configured to have a different tactile feel than would be achieved through intaglio, e.g., a large, smooth, raised area. Alternatively, the security device can be designed to more closely mimic an intaglio print by using a series of separate image elements 11 to carry the image features. An example is shown in Figure 3(b), the modality of which is substantially as already described with reference to Figure 3(a). However, in this case, the common CI image is of the digit “10”, and each image feature (i.e., the 1” and the “0”) is formed from a series of separate in-line elements 11, 11’. In this example, the in-line elements 11 forming the “1” are narrower than the in-line elements forming the “0”, so the two features will appear with different color intensities (the “1” will appear lighter than the “0”). There are two surface relief structures 20, each formed from the same colorless cured material 20a, one corresponding to the digit 1” and the other to the digit 0”.Each relief structure on the surface comprises a series of raised elements 21 corresponding to the in-line elements 11, 11' and a base layer 29. On the opposite surface, two printing layers 30 are provided, formed from ink 30a and arranged as printing elements 31, 31' in alignment with the corresponding raised elements 21, 21'. The resulting common image will appear as the number 10” in a color determined by that of ink 30a, which is lighter in the “1” than in the 0. Upon close inspection, the presence of the in-line elements will be distinguishable. Each digit 1” and “0” has a peripheral border 19 corresponding to the base layer 29. Figures 4(a) and 4(b) show the corresponding modalities to those in Figures 3(a) and 3(b), respectively, except that here the printing layers 30 are each formed from two colors.Therefore, in the embodiment of Figure 4(a), the print layer 30 comprises two inks 38a and 38b in different respective colors Cj and C2. The first ink 38a is arranged to cover an area corresponding to the left half 18a of the digit “5” in the common image CI, and the second ink 38b is arranged to cover an area corresponding to the right half 18b of the digit “5”. The print layer 30 as a whole thus exhibits all the features of the common image (i.e., the complete digit “5”) as before, but in two colors. Similarly, in the example of Figure 4(b), the print elements 31a forming the digit “1” are provided in a first ink 38a of a first color Ci, while the print elements 31b forming the digit “0” are provided in a second ink 38b of a second color C2. Common images h 107nn / C7n7 / B / vi. The ICs displayed by the security devices in Figures 4(a) and 4(b) are therefore multicolored images. It will be appreciated that three or more different colors could easily be displayed by the appropriate provision of inks in the printing layer 30. In the preceding examples, the relief structure of surface 20 and the printing layer 30 have been matched in that the printing layer is arranged so that the ink is present in locations corresponding to the raised protrusions of the relief structure of surface 20, and not elsewhere. However, this is not essential, and different visual effects can be achieved by varying the relative lateral extents of the two constituent parts. The features of the common image that each carries must, of course, still be aligned. Figures 5(a) to 5(c) illustrate some examples. Figure 5(a) again shows the modality of Figure 3(b) to facilitate comparison with Figures 5(b) and 5(c). (It should be noted here that the details of substrate 2—which can take any shape as long as it is not opaque—are not shown.)Figure 5(b) shows a variant in which the print layer 30 is no longer provided as a series of print elements 31,31' but as two continuous areas of ink 38, the first in the shape of the digit 1” and the second in the shape of the digit 0. The result will be a common CI image showing the digit 10” with a solid color fill, although the image elements 11 will still be visible (at least at some viewing angles) due to the relief structure of the surface 20. As before, the digit will have a colorless border peripheral region 19. Figure 5(c) shows a further variant in which the two ink areas 38 extend laterally so that their outer limits coincide with those of the two areas of cured material, which include the peripheral region formed by the base layer 29. The common CI image displayed by the security device will now also exhibit a colored border peripheral region 19. It should be noted that while the print layer 30 can be configured to exactly match (or mirror) the molding structure, as in some of the previous modalities, this is not essential. Figures 6(a)–6(d) illustrate some options. Figure 6(a) shows an example of a safety device in cross-section, which could be a portion of any of the devices described above (e.g., a portion of the multi-tonal image shown in Figures 2(a)–2(b)). As shown in the plan view of Figure 6(b), in a first variant, the raised protrusions 21 of the relief structure of the cured surface 20 and the printed image elements 31 could be configured to match and align with each other.Alternatively, as shown in Figure 6(c), the printed image elements could comprise a series of dots or other elements 31a, which are arranged in a separated manner along the paths of the raised protrusions 21. Alternatively still, the printed elements 31 need not have the same orientation as the raised protrusions 21, but could have some other arrangement, such as the orthogonal line pattern shown in Figure 6(d). Whereas in the preceding embodiments the security device is represented as being located in a window region in substrate 2 and visible from both sides, this is not essential. In another embodiment, shown in Figure 7, there may be a subsequent print or another layer 70 applied over the print layer 30. The embodiment in Figure 7 is otherwise the same as the embodiment in Figure 3(b). This layer 70 could be, for example, an ink or other coating (e.g., a screen-printed white ink) or an applied feature such as a foil. This subsequent process could render the substrate semi-transparent or opaque in the area of ​​the security device. Such an additional layer 70 over the print layer 30 could be provided in any of the embodiments described herein. Figure 8 shows an additional embodiment of a security device in an exploded view to illustrate the two-dimensional configuration of each component. In Figure 8, an RGB (red, green, blue) image 30 is printed on one side of a transparent substrate 2, for example, by offset printing. This could be, for example, a window region of a polymer security document. On the other side of the transparent substrate, the same image is provided as a colorless relief structure 20, formed by mold curing. The relief structure is defined according to the same image, for example, by comparing the same image periphery and / or by replicating features within the image across different mold heights.The molding could be a single unit of cured material (optionally variable in height) or could comprise multiple separate elements, for example, dots or lines, to produce a more tactile sensation (although a base layer will typically still be present between them). When viewed through the molding, the user sees the full-color CI image, and the molding provides a tactile sensation to the image. The two components 20, 30 are in exact register with each other. Figures 9(a) and 9(b) represent a further modality based on the same concept as the modality in Figure 8, but in greater detail. As shown in Figure 9(a), a relief surface structure 20 formed from a cured material 20a is placed on a first surface 3a of a substrate 2, in a transparent portion thereof. A print layer 30 is provided on the opposite surface 3b, and here it is an RGB (red, green, blue) print formed from three corresponding inks 30a, 30b, and 30c. It should be noted that, while in the Figure the inks appear stacked on top of each other, giving the impression of height, this is purely for clarity of illustration, and in practice the print layer 30 will normally be substantially flat (an exception being where the print layer 30 is formed by micro-intaglio).More generally, print layer 30 can comprise any of: adjacent color blocks, overlapping color blocks, separate elements (as shown), or standard halftone image elements. The relief structure of surface 20 and print layer 30 are in overlapping alignment and are manufactured in alignment with each other. Both the relief structure of surface 20 and print layer 30 are configured to exhibit features of the same common CI image, which here is a full-color photographic portrait (e.g., of the security document owner). Therefore, print layer 30 will typically include the red, green, and blue components of the image (shown separately in Figure 9(b)), which can be applied in consecutive or simultaneous print jobs (having been first picked up on a blanket or offset roller). The relief structure of surface 20 conveys the common image features by providing one or more raised protrusions 22, which may or may not coincide with the arrangement of the inks in the printing layer (but the image features carried by each constituent will align). For example, the relief structure of surface 20 could include raised protrusions along an area bounded by the outline of the person's head, so that the area of ​​tactility matches the portrait. Alternatively, the nature of the surface relief could vary so that different features of the portrait correspond to areas of different tactility. For example, the surface relief structure could be configured so that an area corresponding to the person's hair feels rough compared to the area corresponding to their face, which feels relatively smooth.In another example, the height of the surface relief structure could be configured to vary according to the common image. For instance, features in the portrait that would be closest to the viewer in real life (such as the person's nose) could correspond to taller raised elements, or the surface relief structure could comprise a single raised element with a variable-height surface that is a 3D outline of the person's face. The surface relief structure 20 could additionally or alternatively be formed as a halftone version of the common image, i.e., it has a series of separate raised elements that vary in size, shape, or spacing along the series to produce a multitonal version 30 hi O7nn / C7n7 / B / vi of the image, which will be visible due to the reflective nature of the cured material 20a.A base layer 29 of lower height than the protrusion(s) 22 will be present as before and will form a colorless border region, which is not shown. The mode in Figures 10(a)–10(b) is substantially the same as the mode in Figures 9(a)–9(b), except that print layer 30 is a CMYK (cyan, magenta, yellow, black) print formed from four corresponding inks 30a, 30b, 30c, and 30d. Again, a full-color tactile photographic portrait is formed, like the common CI image. Of course, monochromatic (e.g., grayscale) images can also be formed, as shown in the mode in Figure 11. This is identical to the modes in Figures 9(a)–10(b), except that here print layer 30 is a monochromatic (e.g., grayscale) version of the photographic portrait, formed from a single ink 30a (e.g., black). In the embodiments presented so far, the relief structure of surface 20 and the print layer 30 each exhibit the entire common image CI, that is, the same set of features. However, this is not essential, and in other embodiments, each constituent may contribute a different set of features from the common image to the final appearance of the device. The feature sets may or may not include one or more features that are common to both. Figures 12 to 15(c) provide some examples where the two feature sets are different. The configuration in Figure 12 is a variant of the configurations already described with reference to Figures 3(a) and 4(a). The only difference lies in the configuration of print layer 30. In the configuration of Figure 12, print layer 30 is configured to display only the features that define the right half of the 5” digit in the common CI image. Print layer 30 is absent elsewhere. In the resulting security device 10, the common CI image therefore comprises a tactile 5” digit, the left half 18a of which is colorless, while the right half appears in the color of ink 30a. The entire 5” digit is legible due to the reflective nature of the surface of the cured material 20a. Similarly, the modality in Figure 13 is a variant of the modalities already described with reference to Figures 3(b) and 5(b), the only difference being the configuration of the print layer 30. In the modality of Figure 13, the print layer 30 is configured to display only the print elements 31, 31' corresponding to the right half of each of the digits “1” and 0, and is absent elsewhere. In the resulting security device 10, the common CI image therefore comprises tactile digits “1” and 0', of which the left halves are each colorless and the right halves are each colored by the ink 30a. The entirety of each digit is legible due to the reflective nature of the surface of the cured material 20a. In both of the preceding examples, the set of common image features exhibited by the relief structure of surface 20 is the entire set of features necessary to define the common image CI, whereas the set exhibited by the print layer 20 is a subset of those features. It is also possible for one of the constituents to exhibit common image features that the other does not. For example, in the modality of Figure 12, the relief structure of the surface could be modified so that it is present only to define the left half 18a of the digit “5” and is absent in the right half 18b. In the modality of Figure 13, the raised protrusions 21, 21' could similarly be present only where the print elements 31, 31' are absent. The modality in Figure 14 provides a further example. Here, the common image CI is an assembly of geometric shapes: a circle 15 within a solid filled square 16, within the outline of a larger square 17. The relief structure of surface 20 includes raised protrusions corresponding to the solid square feature 16 and central portions 17a of each side of the square outline feature 17. The print layer 30 comprises an outer square 37a of ink and a central inked circular area 37b.In combination, a complex design is formed as shown in the plan view, with circle 15 having the ink color 30a, solid square 16 being colorless but tactile, and the square outline 17 being colored throughout but tactile only in portions 17a and not in the corners 17b (it should be noted that portions 17a are not shown colored so that the presence of cured material 20a can be deduced from the figure, but they will be colored in practice). Thus, the common CI image is composed of features contributed by each of the constituents 20 and 30. The image is preferably designed to show the precise registration between the surface relief structure and the printing layer. In the modality of Figure 14, this is achieved particularly well by providing tactile portions 17a in the square outline 17, the incorrect placement of which would be easily pointed out. Another example of this principle is shown in Figures 15(a), 15(b), and 15(c). Plan views of the molded structure 20 and the print layer 30 are shown in Figures 15(b) and 15(c), respectively. In this case, the final common image CI is a circular design comprising a complex stained-glass-like arrangement with 12 petal-shaped areas arranged radially around a central cross composed of four inward-pointing arrows and 12 radial lines aligned with the centers of the petal shapes. The relief structure of surface 20 is configured with a series of raised areas 23, with the recesses between them providing the petal-shaped features of the common image and a central circular area. Print layer 30 consists of a set of 34 printed areas configured to display the radial lines and central cross feature.The registration between the two constituent parts is shown by the intricate nature of the common CI image and by the need to center the two parts precisely to achieve the expected alignment. While in many modalities it will be desirable for the tactile effect of the molded structure to match the visual configuration of the print layer, in other cases distinctive security effects could be achieved by intentionally including a partial mismatch. This is a subtle but striking and therefore memorable feature, which, nevertheless, might go unnoticed by potential counterfeiters. The clever placement of molded tactile / printed elements can promote further inspection of the device. For example, in the modality of Figures 2(a)-2(b), in the kingfisher image, the beak and back feathers could be tactile with molding (i.e., raised elements 21 present), while the eye and breast feathers lack molding (i.e., raised elements 21 absent) and are therefore not tactile.Here, the appearance of print layer 30 (which continues along both areas) suggests that they would feel the same, but a close inspection reveals that this is not the case. Figures 16(a), 16(b), and 16(c) show another example. Each figure shows (i) the device in plan view and (ii) in cross-section. The device in Figure 16(a) has matching molded structures 20 and printed elements 30, each carrying a repeating set of the digit 5. In this case, each digit 5 ​​will be both colored (by the printed layer 30) and tactile (as a result of the molded structure 20), as might be expected. In the configuration of Figure 16(b), a repeating series of identical digits 5 is again printed 30, and all but one of the images has a corresponding molded structure 20. Therefore, the non-tactile digit 5 ​​stands out on inspection. The reverse is also possible, as shown in Figure 16(c).Here, the device comprises a complete set of molded images (again, here in the form of the digit 5”), but now one of the digits is left unprinted and will therefore be less visually perceptible but detectable by feeling. The molded structure 20 can also be configured to provide more complex haptic (i.e., tactile) effects. An example is shown in Figures 17(a)–17(d). Here, the 33 hi O7nn / C7n7 / B / vi safety device is shown in plan view in Figure 17(a) and in cross-section in Figure 17(b). Two common images, CIi and CE, are formed, each appearing as a sign. The corresponding print layers 30i and 302 provide color to each image, and the aligned molded structures 20i and 202 provide tactility. However, the two molded structures 201 and 202 are different from each other, so the tactile sensation exhibited by the common image CIi is different from that of the common image CI2. This difference could take any form (e.g., level of roughness, directionality, etc.). In the present case, the two molded structures are shown in enlarged detail in Figures 17(c) and 17(d), respectively.Both molded structures 201 and 2U2 comprise a series of raised protrusions 21, with a tactile structure formed from facets 241, 242 on top of the protrusions 21. The facets 24i, 242 are asymmetric and oriented in opposite directions on the two structures. Therefore, a user running their finger across the device from left to right (as shown in the Figure) will find that image Ch feels relatively smooth and image CI2 relatively rough. However, when moving their finger across the device in the opposite direction, the relative sensations will be reversed. Other tactile elements that could be used include symmetric facets, prisms (symmetric or asymmetric), pyramids, cubic structures, cones, curves, and irregular structures. Figures 18(a), 18(b), 18(c), and 18(d) show four additional examples in which the common images comprise full-color photographic images (here, portraits). Both of these modes are variants of the mode described above with reference to Figures 9(a)–9(b), and thus the print layer 30 is an RGB image. However, the print layer 30 could alternatively be a CMYK image as described with reference to Figures 10(a)–10(b), or it could potentially comprise some other set of colors such as orange, green, and violet. In the mode of Figure 18(a), the security device 10 is the same as that shown in Figures 9(a)–9(b), except for the configuration of the relief structure of surface 20, which in Figure 18(a) exhibits features only from the right half of the common image.As a result, while the entire portrait 18 is visible in full color on the finished security device 10, only the right half 18b of it is tactile. The relief structure of surface 20 is absent on the left half 18a. In the configuration of Figure 18(b), the opposite occurs. Here, the security device 10 is the same as that shown in Figures 9(a)-9(b), except for the configuration of the print layer 30, which in Figure 18(b) exhibits only features of the right half of the common image. As a result, while the entire portrait 18 is tactile on the finished security device 10, only the right half 18b of it is visible in full color. The left half 18a will still be visible to some extent due to the reflective qualities of the cured material 20a.In the configuration of Figure 18(c), the relief structure of the cured surface 20 and the print layer 30 overlap only in a central region of the device. Therefore, the portrait 18 comprises three different areas: a first portion 18a in which only the print layer 30 is present; a second portion 18b in which both the print layer 30 and the relief structure of the cured surface 20 are present; and a third portion 18b in which only the relief structure of the cured surface 20 is present. As such, the first portion 18a will appear in full color but not tactile; the second portion 18b will be in full color and tactile; while the third portion 18c will be tactile but not in full color (the third portion 18c may still be visible in a grayscale / single-color form due to the reflective nature of the molding 20 and / or any colored tint it may have). Figure 18(d) shows another variation. Here, instead of being formed from multiple discrete raised elements, the relief structure of the cured surface 20 comprises a continuous surface of variable geometry (e.g., height, length, width, etc.). For example, the structure can provide a three-dimensional outline corresponding to the face of the person shown in image CI. In this case, the printing layer 30 provides the fine details of the image, while the molding 20 primarily serves to provide tactility. In Figure 18(e), the relief structure of surface 20 is configured to display all the details of a photographic portrait 18 that forms the main part of the common image CI, in this case through a set of separate raised elements of varying height. Furthermore, the relief structure of the surface comprises a protrusion 22a that forms a laterally rectangular border 17 framing the portrait. The print layer 30 displays only a subset of the features of the common image CI, specifically, a uniform area 38a of a first ink 30a corresponding to the face region 18' of the portrait 18, and a laterally rectangular line 38b in a second ink 30b corresponding to the border 17. The resulting common image comprises a tactile representation of the portrait 18' that is partially colored and partially uncolored, within a colored tactile border 17. The ability to control color placement with high precision not only allows for the display of full-color images, such as those exemplified above, but also other color effects. In conventional lithographic printing, multicolored effects are known to be produced by a process known as "rainbow," in which two inks of different colors are applied to the adjacent surface of the printing plate. When they meet, the inks blend together to produce intermediate colors that vary continuously in a spatial sense. The present invention can be used to create "rainbow" colored devices that are also tactile, which was previously not possible. Figures 19 and 20 show two examples, corresponding to those in Figures 3(a) and 3(b) respectively, except that here the printing layers 30 are each formed from multiple inks. In the configuration of Figure 19, the printing area 38, which is shaped like the digit “5”, is formed by at least two inks, such that a left portion has a first color Ci (e.g., red), a right portion has a second color C2 (e.g., blue), and an intermediate portion located between them has one or more intermediate colors C3 (e.g., purple). This is achieved through “rainbow” biographical printing by using two inks in the Ci and C2 colors, resulting in appropriate spatial mixing in the middle region.In this way, the transition from the first color Ci to the second color C2 through the intermediate colors C3 is truly continuous, in the sense that, even under magnification, no discrete changes from one color to another will be revealed. The same principles apply to the modality of Figure 20, with the only difference being that here the image is conveyed through a series of image elements 11, 11'. The corresponding print elements 31, 31' are formed by biographic printing in the appropriate colors to achieve the rainbow effect as before. It is also possible to provide more than two such rainbow effects on the same print layer 30. For example, in the modality of Figure 20, the digit 1 could be arranged to show a transition from red to blue, while the digit 0 could be arranged for the transition from green to yellow. In the examples so far, the cured material 20a from which the surface relief structure is formed has been transparent and colorless, so that it does not contribute to the common CI image color appearance. However, in more complex modalities, the cured material 20a can carry a colored tint. This can be used as an additional variable to create new visual effects, especially since the color density of the surface relief structure 20 can now vary depending on its height (elevated protrusions will typically have greater color intensity than lower portions, such as the base layer 29, due to the greater amount of tinted material 20a through which light passes). Some examples will be explained with reference to Figures 21 to 26(b), but it will be appreciated that the same principle can be applied to any of the other modalities described herein. Figures 21 and 22 show two modes, corresponding to those in Figures 3(a) and 3(b) respectively, except that here the relief structure of surface 20 is formed from a cured h 107nn / C7n7 / B / vi material 20a that is transparent (i.e., clear) but carries a colored tint (e.g., blue). As before, the printing layer 30 is formed with a single-color ink 30a (e.g., red). In the mode of Figure 21, the result is a common image Cl representing the digit “5” as a continuous area 18 in a color that arises from the mixture of the color of the material 20a and that of the ink 30a. For example, in the example, area 18 may appear purple, at least when viewed from the side of the safety device that carries the relief structure of surface 20. Area 18 is surrounded by a border region 19 that is only the color of material 20a (e.g., blue). Therefore, a common two-color image Cl is obtained.Similarly, in the modality of Figure 22, the image elements 11 and 1Γ that define the digits “1” and “0” now appear in the mixed color (e.g., purple) while the border 19 that surrounds them appears in the color of material 2üa (e.g., blue). If the ink 30a forming the printing layer 30 is sufficiently transparent, the appearance of the devices in Figures 21 and 22 will be virtually the same from either side of the substrate in reflected and transmitted light. However, more complex effects can be introduced by increasing the opacity of ink 30a. If ink 30a is sufficiently opaque, it will obscure the portions of the surface relief structure located behind it when the device is viewed from the side bearing the printing layer 30, resulting in a different color appearance. This variation can be applied to all the modes described herein. Thus, in the mode of Figure 21, if ink 30a is red and opaque, the common image appearance when viewed in reflection from the side of the surface relief structure will be as previously described (a purple “5” with a blue border surrounding it).However, when viewed in reflection from the other side, the standard image will show a red "5" with a blue border. In transmission, the 5 may appear very dark (for example, behind), surrounded by a blue border. While in many cases it will be convenient for the color of the cured material 20a to be different from that of the ink 30a, this is not essential, and different effects can be achieved if the colors are the same or similar. For example, Figure 23 shows a modality that is the same as that in Figure 21, except that the cured material 20a has a tint that is the same color as the ink 30a that forms the printing layer 30 (e.g., red). In this case, the resulting common image is multitonal rather than multicolor; the digit “5” (area 18) appears in a deeper shade of red than the boundary region 19, which is a lighter red. Even more complex effects can be achieved if the print layer 30 itself is formed in multiple colors. For example, Figure 24 shows a modality in which the security device 10 is the same as that described with reference to Figure 21 above, except that the print layer 30 now includes a peripheral border 38b around area 38a, in a second ink 30b of a different color from the ink 30a that forms area 38a. For example, area 38a might be red while the border 38b is yellow and the cured material 20a carries a blue tint. The resulting common image CI will comprise a digit-5 shaped area 18 having a color corresponding to a mixture of the colors of the cured material 20a and the first ink 30a (for example, purple). Surrounding the digit 5 ​​will be a border 19 formed from two different adjacent colors.The interior area 19a will be a color corresponding to a mixture of the colors of the cured material 20a and the second ink 30b (for example, green). The exterior area 19b will be a color corresponding only to the color of the cured material 20a (for example, blue). The same principles can be applied to security devices that display full-color images. Figure 25 shows an example that is otherwise the same as the modality in Figure 8, but in which the tactile molding 20 has a colored tint—in this case, blue. The image 30 on the opposite side is printed only in red and green. A full-color RGB version of the image will be seen when the combination is viewed through the blue tactile molding. The necessary variations in the level of blue in the molding can be achieved either by varying the height of the molding (higher parts of the molding will have a higher color density than lower parts, due to the increased amount of material present) and / or by providing elements (e.g., dots) of the tactile molding only where a blue contribution is required. Such raised elements will have a higher optical density than the base layer between them. Another modality employing this principle is shown in Figures 26(a) and 26(b). This modality is a variant of the modality in Figures 10(a)–10(b), which has a common CI image in the form of a full-color, tactile photographic portrait composed of CMYK channels. However, in this implementation, the print layer 30 is formed from three inks: 30b (yellow), 30c (magenta), and 30d (black), resulting in a “MYK” printed image lacking the cyan channel. The cyan contribution is made by the relief structure of surface 30, which is formed from a cured material 20a that has a cyan tint. As in the previous mode, the intensity of the cyan exhibited will vary along the relief structure of surface 20 according to its height profile - each of the protrusions 22 will appear with a relatively intense color while the lower areas, including the base layer 29, appear lighter or even colorless.It is also possible to form the surface relief structure 20 from two or more cured materials, which may have different optical characteristics (e.g., different visible colors). The two or more cured materials will typically be laterally offset from each other (preferably without overlap). If they are abutted to produce a continuous body of cured material, they will be considered to form one and the same surface relief structure, whereas if they are separated from each other, they will be separate surface relief structures. Either approach may be employed in the embodiments of the invention. Figures 27(a) and 27(b) show an example of the latter case. Figure 27(a) shows an intermediate stage in the manufacture of the eventual safety device 10 shown in Figure 27(b). The safety device 10 is similar to that described above with reference to Figure 5(b), with a common CI imagewhich displays the digits 1” and 0”, each defined by a series of Ha image elements, 11b. The relief structures on surface 20 are each formed from a different material with different respective colors. Figure 27(a) shows the two materials 20'a and 20'b being applied to the first surface 3a of substrate 2 in their uncured state. As will be described below with reference to Figures 46(a)-46(b), this can be achieved by printing the curable materials onto the substrate, preferably in alignment with each other (for example, by using a non-contact printing method such as inkjet printing), or by applying the two or more curable materials to the molding tool. The first curable material 20'a has a tint of a first color, for example, yellow, and the second curable material 20'b has a tint of a second color, for example, blue.The curable materials 20'a, 20'b are each formed into the desired surface relief structures to define raised elements 21, 21' corresponding to the image elements lia, 11b of the common image CI on the second surface 3b of the substrate 2, a printing layer 30 is provided comprising two areas 38 of ink 30a (e.g., red) in shapes corresponding to the digits 1 and 0 respectively.The resulting common image will comprise a digit 1 defined by image elements 1a having a color formed by a mixture of the colors of material 20a and ink 30a (e.g., orange), surrounded by a border 19a having a color corresponding to that of material 20a (e.g., yellow) and a digit 0” defined by image elements 11b in a color formed by a mixture of the colors of material 20b and ink 30a (e.g., purple) surrounded by a border 19b in a color corresponding to that of material 20b (e.g., blue). As illustrated in each of the preceding modalities, the relief structure of surface 39 hi oznn / cznz / B / vi and the print layer 30 are configured so that, in combination, they exhibit the common image CI along a first region Ri of the substrate. Optionally, the safety device may include a second region R2, which may be adjacent to the first region where the image is located. The molding structure and / or the print layer may extend (continuously or discontinuously from the first region) into the second region, but here the two components (if both are present) do not need to align with each other or be defined based on a common image (as is the case in the first region).For example, in the second region, the printing layer could take the form of microimages or another series of images, and the molding structure could take the form of a series of focusing elements, together forming an optically variable device. If the security device is ultimately placed in a window (or half-window) region of a security document, the first and second regions of the security device could both be in the same window (or half-window) region, or in different regions of this type. Therefore, it is possible that one or both of the relief structure of surface 20 and the print layer 30 may be present in other locations on substrate 2, such as in a second region R2 that is laterally displaced and does not overlap with the first region R1. In this second region R2, the configuration of the relief structure of surface 20 and / or the print layer 30 differs from that of the first region R1, so that the common CL image does not continue into the second region, and the two regions appear visibly distinct from each other. Figures 28(a) to 28(d) schematically illustrate some options in each case; the shape of the relief structure of surface 20 and that of the print layer 30 are not precisely represented and should only be taken as an indication of the lateral extent of each component.Figure 28(a) shows the same arrangement as in each of the previous modes: the surface relief structure 20 and the printing layer 30 are present only in the first region Ri and exhibit only the common image. In Figure 28(b), the surface relief structure is again present only in the first region Ri, but now the printing layer 30 extends into a second adjacent region R2. In the second region R2, the printing layer 30 will have a different appearance from its appearance in the first region Ri so that the common image remains clearly distinct. For example, in the second region R2, the printing layer 30 might provide a background to the common image, for example, in a contrasting color and / or as a uniform area.In the mode of Figure 28(c), the print layer 30 is only present in the first region Ri, while the relief structure of surface 20 extends into the second region R2. Again, the h 107nn / C7n7 / B / vi relief structure of surface 20 will have a different configuration in each region so that the common image can be detected by touch as distinct from the second region R2 due to its different tactility. Finally, in the mode of Figure 28(d), both the relief structure of surface 20 and the print layer 30 are present in the second region R2. Here, both will be configured differently from their respective arrangements in the first region Ri so that the common image remains distinct. Figures 29(a), 29(b), and 29(c) show some specific examples. In each case, the arrangement of the surface relief structure 20 and the print layer 30 in the first region Ri is the same as described with reference to Figures 9(a)–9(b), resulting in a common CI image in the form of a full-color, tactile RGB photographic image. In the configuration of Figure 29(a), the surface relief structure 20 is present only in the first region Ri and not in the second region R2. The print layer 30 extends across the second region R2 and is configured to present a relatively uniform background pattern 35. Therefore, the resulting security device 10 will have a background print in a second, non-tactile region R| surrounding the full-color tactile portrait. In the configuration of Figure 29(b), the print layer 30 is restricted to the first region R| and is absent in the second region R2.The relief structure of surface 20 continues into the second region R2 and here it is provided with a different tactile structure compared to that present in the first region Ri, for example, a set of parallel raised ridges 25. The resulting security device 10 displays the common image CI against a smooth background (in this case, colorless / transparent but more generally having the local appearance of substrate 2) that has a distinct tactile feel. In the modality of Figure 29(c), both the relief structure of surface 20 and the printing layer 30 are present in the second region R2 and have the characteristics just described, with the result that the CI portrait is surrounded by a tactile background area of ​​a different color in region R2. It is also possible to use the relief structure of surface 20 and / or the printing layer 30 to provide one or more additional security features in the second region R2. For example, the two constituents can be configured to form, in combination, an optically variable security device 40 in the second region, such as a moiré magnifier, a lenticular device, an integral imaging device, or a caustic device. Figures 30(a), 30(b), and 30(c) show two examples of this. In Figure 30(a), the first and second regions Rj and R2 are discrete and laterally offset from each other as before (in this case, adjacent to each other—although they could be separated or even placed in separate windows on the security document).In the first region Ri, the surface relief structure 20 and the impression layer 30 are configured to display a common tactile image according to any of the modalities described above. In the second region R2, the surface relief structure is configured to define a series of focusing elements 41, such as lenses. The series of focusing elements can have a one-dimensional periodicity (e.g., cylindrical elements) or a two-dimensional periodicity (e.g., spherical or aspherical elements). The impression layer 30 is configured to provide a series of images 42 and is substantially located in the focal plane of the series of focusing elements. In a moiré magnifying glass, the image series 42 will typically comprise a series of micro-images, and the hue and / or orientation of the image series 42 will not match those of the focusing element series 41, resulting in synthetically magnified images of the micro-images due to the moiré effect. In a lenticular device, the image series 42 will typically comprise a set of image elements, each of which is a section of an image to be displayed along the second region R?. Sections of various images will be interleaved. In this case, the hue and orientation of the image series 42 will typically match those of the focusing element series 41. At any viewing angle, the focusing element series directs light from the image elements—all derived from the same image—to the observer so that the complete image is displayed. Changing the viewing angle displays a different interleaved image.Therefore, the safety device 10 as a whole will display a static tactile common image CI in a first region Ri of the same (as before), alongside an optically variable device 40 in a second region R2. In a variant of this configuration, shown in Figure 30(b), the first and second regions Ri and R2 can be sandwiched between each other along the length of the safety device. This will give the visual impression that the static tactile common image is superimposed on an optically variable background. It should be noted that Figure 30(b) is highly schematic and that, in reality, the relative sizes of the lenses and the surface relief structure elements will typically be such that there are many lenses in each sandwiched portion of the optically variable device, between each portion of the common image. Figure 30(c) shows an additional embodiment in which the second region R2 contains a caustic device 45. Caustic devices are surface reliefs that project a caustic image CA when illuminated with light L. Various methods for designing a relief structure that will project a certain caustic image have been described in WO-A-2019 / 063778, WO-A-2019 / 063779, and WO-A-2020 / 070304, in each of which the caustic image is a “real” image that is viewed by projection onto a suitable surface, such as a wall or screen. Similarly, WO-A-2020 / 070299 describes techniques for forming a relief structure that generates a virtual caustic image, which does not require projection onto a surface but can be directly observed with the naked eye. In the example shown, the first region Ri and the second region Rz do not overlap; they are adjacent to each other.The first region Ri displays a common image formed by the surface relief 20 and the print layer 30, as in other modalities. The caustic device 45 in the second region Rz is formed as an extension of the same surface relief structure 20, achieved through appropriate molding tool settings. In most of the preceding examples, the first Ri region where the common image is displayed has been located in a transparent window region 51 of substrate 2. However, while arranging the feature in a window region as described above may be convenient in many cases, so that the image is clearly visible from both sides of the substrate, in other cases it may be preferable to form the security device on a substrate that is not transparent but only translucent. For example, the feature could be formed on a paper substrate. Alternatively, it could be located in a windowless area of ​​a polymer banknote where at least one opacifying layer 2b is present in the substrate. An example of this is shown in Figure 31. In any other case, the security device corresponds to that already described with reference to Figure 8 above.In this case, the displaced image will typically not be visible (or barely visible) in light reflected from the molding side. Tactility hints at an image, and when held up to the light, the displaced image is revealed. Of course, the configuration in Figure 25 could equally be applied to a windowless region in this way. It is also possible for part of the image to be in a windowed region and another part in a windowless region. Figures 32(a) to 32(g) provide some examples of possible configurations. In each case, substrate 2 is represented as a multilayer substrate comprising a transparent core substrate 2a of a polymer such as BOPP, with opacifying layers 2b disposed on each side. However, other forms of substrate 2 could be used instead. Regions of substrate 2 that have their standard baseline opacity level are called windowless regions 50. In the example shown, this corresponds to regions where both opacifying layers 2b on the two sides 43 The substrate layers 3a and 3b are uniformly present. Here, substrate 2 has its highest level of opacity. In the previous examples in Figures 2(a) to 30(c), the safety device 10 is positioned in a windowed region 51, i.e., where both opacifying layers 2b are absent, so substrate 2 is locally transparent (unless an additional layer, such as layer 70 in Figure 7, is applied). In the configuration of Figure 32(a), the safety device is positioned so that the first region Ri (or at least a portion of it) is located in a half-windowed region 52, i.e., where one of the opacifying layers 2b is absent and the other is present. Therefore, the half-windowed region 52 is translucent rather than transparent and has a lower opacity than the unwindowed region 50.In this example, the half-window region 52 is formed by locally omitting the opacifying layer 2b on the first substrate surface 3a so that the surface relief structure forms directly onto the transparent core substrate surface 2a (optionally via a primer or other surface treatment). The print layer 30 is arranged so that the retained opacifying layer 2b on the second surface 3b is located between the print layer 30 and the core substrate 2a. The reverse arrangement is also possible, as shown in Figure 32(b), where the half-window 52 is formed by retaining the opacifying layer on the first surface 3a and omitting it on the second surface 3b. The appearance of the security devices shown in Figures 32(a) and 32(b) will be similar or identical. In the embodiments of Figures 32(a) and 32(b), as well as those of Figures 2(a) to 30(c), the windowless region 50 of substrate 2 could be opaque if desired. All that is required is that at least part of the first Ri region (preferably all of it) be located in a transparent or translucent area of ​​substrate 2, such as the half-window 52 (or, indeed, the windowed regions 51 of previous embodiments). In other cases, when the security feature 10 is located in a windowless region 50, as shown in Figure 32(c), the standard baseline opacity level of substrate 2 must be sufficiently low so that the common image can be observed when the security feature 10 is viewed in transmitted light. Standard polymer banknote substrates and conventional paper banknote substrates typically satisfy this requirement. In still other examples, the safety device 10 could be partially arranged in a window or half-window region and partially in a windowless region. An example of this is shown in Figure 32(d). In this case, the windowless region 50 could be opaque or translucent. If desired, the window or half-window region could be designed to cooperate with the common image, for example, by interlacing with the common image, repeating common image elements, or having a contour that matches a feature of the common image. Similarly, the security device can be configured to interact with any watermark or pseudo-watermark feature provided on substrate 2. While, in the Figures, the opacifying layers 2b of a polymer-type document substrate 2 are shown for clarity as a single layer on each side of the core 2a, in practice they may each be composed of multiple layers. For example, it is typical to have multiple opacifying layers on each side of the core 2a; in many cases, there will be three layers on each side: specifically, a first white opacifying layer, a second conductive opacifying layer (which may be whitish), and then a third white opacifying layer.Each of the individual layers can be set with different extents, for example, in the form of parts of an image, resulting in an effect similar to a watermark that can be seen in transmitted light (and sometimes in reflection). Examples of such features can be found in WO-A-2017 / 055823. The security device described herein can be designed to display a combined effect with a watermark or a pseudo-watermark. Figure 32(e) shows a simple example. As shown in the cross-section of Figure 32(e)(i), the pseudo-watermark exhibits two tones—specifically, that of the bulk substrate 2 where all opacifying layers are present (region 55) and a more translucent tone where one or more (but not all) of the opacifying layers on each side of the core are absent (region 54). The relief structure of surface 20 and the printing layer 30 are each configured as in the modality of Figure 21. That is, they both define an image of the digit '5', with the relief structure of surface 20 formed from a cured material having a colored tint (e.g., blue) and the printing layer having one or more colors (e.g., red).When the device 10 is viewed under light reflected from the side of the relief structure of surface 20 (Observer O1), as shown in Figure 32(e)(ii), the image appears as the digit 5 ​​in the color of the curable material (e.g., blue) with a lighter border region formed by the base layer 29. Any contribution from the print layer 30 is substantially hidden by the substrate 2. When viewed under light reflected from the opposite side (Observer O2), only the print layer 30 is now visible, so the device appears as the digit “5” in the color(s) of the print layer, e.g., red, as shown in Figure 32(e)(iii). When the device is viewed in light transmitted from either side, as seen in Figure 32(e)(iv), the two components combine so that in region 54 where 45. 107nn / C7n7 / B / vi The watermark provides translucency to the substrate, and the image appears in a combined color, for example, purple. However, due to the placement of device 10 over the watermark, only a left portion of the image is visible. The right portion of the image is hidden by the relatively opaque region 55 of the substrate. It will be appreciated that while the modality has been illustrated by the use of a pseudo-watermark formed by the presence / absence of opacifying layers on a polymer document substrate, the same effects could be achieved with a conventional watermark formed on a fibrous substrate, for example, paper (where different levels of opacity are provided by varying the fiber density or the substrate thickness). It will also be appreciated that different regions of the security device could be located in different respective window (or half-window) regions of a security document and / or each of such window (or half-window) regions could bear a respective security device. For example, Figure 32(f) shows an embodiment of a security document 100 having three security devices 10 (each in accordance with any of the embodiments herein) arranged in separate corresponding window regions 51. The window regions 51 are separated from each other by windowless regions 50 in which the opacifying layer 2b is present. The surface relief structures 20 in each window 51 are preferably formed simultaneously in a common mold-curing process.That is, a single molding tool carries a surface relief that defines each of the surface relief structures 20 and their locations relative to one another, the shapes of which are transferred to the curable material in a processing step. The curable material itself may or may not extend between the window regions. Figure 32(g) shows another example, in which document 100 has two window regions 51, again separated by the non-windowed region(s). In this case, there is a single device 10, of which a first region Ri, displaying a common image, is located in one window region 51, and a second region R2, for example, in the form of an optically variable safety device, is located in the other window region 51.Again, the curable material that forms the relief of surface 20 may or may not extend between the window regions, and likewise the print layer 30 may or may not continue between the window regions. As previously stated, while at least part of the first region Ri (along which the common image is displayed) needs to be located in a region where the substrate between the surface relief structure and the print layer is transparent or translucent, it is not essential that the entire first region Ri be located in this way (although it may be preferable). The combination of the surface relief structure 20 and the print layer 30 may be necessary to complete only a portion of the common image CI. Figure 33 shows one modality of such an arrangement, in which the first region Rj, along which the surface relief structure 20 and the print layer 30 are configured to display the common image, includes both a windowless region 50 of the substrate 2 and a windowed region 51. The windowless region 50 can be either translucent or opaque. In all the embodiments described so far, as indicated at the beginning, it has been assumed that the security device is formed on a substrate 2 that also acts as a document substrate for the eventual security document 100. Suitable document substrates include polymer document substrates of the type already mentioned above and shown again in Figure 34(a), wherein the substrate 2 comprises a core substrate of a transparent polymeric material such as polypropylene (PP) (most preferably biaxially oriented PP (BOPP)), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), nylon, acrylic, cyclic olefin polymer (COP) or cyclic olefin copolymer (COC), or any combination thereof.The polymer substrate 2a can be monolithic, for example, formed from a single one of the materials mentioned above, or multilayer, for example, having multiple layers of the same polymer type (optionally with different orientations) or layers of different polymer types. As mentioned earlier, "transparent" means that the polymer substrate 2a is substantially visually clear, although it may contain a colored dye and / or another optically detectable substance, such as a fluorescent material. One or both surfaces of the polymer substrate 2a may be treated to improve the adhesion / retention of subsequently applied materials. For example, a primer layer may be applied to all or part of either surface of the polymer substrate 2a, e.g., by printing or coating. The primer layer is also preferably transparent and, again, could be tinted or carry another optically detectable material. Suitable primer layers include compositions comprising polyethylene imine, hydroxyl-terminated polymers, hydroxyl-terminated polyester-based copolymers, crosslinked or non-crosslinked hydroxylated acrylates, polyurethanes, and UV-cured anionic or cationic acrylates. Alternatively or in addition to applying a primer layer, the surface of the hi O7nn / C7n7 / B / vi polymer 2a substrate can be prepared for further processing by controlling its surface energy. Suitable techniques for this purpose include plasma or corona treatment. The opacifying layer(s) 2b each comprise a non-transparent material, the primary purpose of which is normally to provide a suitable background for the subsequent printing of graphics. Therefore, preferably, the opacifying layers comprise a non-fibrous polymeric material containing at least one light-scattering substance such as a pigment. The opacifying layers 2b are preferably light-colored, most preferably white or another light color such as off-white or gray, so that a subsequently applied graphics layer will contrast well with them. In preferred examples, the opacifying layers each have a brightness L* in the CIE L*a*b* color space of at least 70, preferably at least 80, and most preferably at least 90.For example, each opacifying layer may comprise a resin such as a polyurethane-based resin, a polyester-based resin, or an epoxy-based resin and an opacifying pigment such as titanium dioxide (TiCh), silica, zinc oxide, tin oxide, clays, or calcium carbonate. Two or more opacifying layers can be applied to each surface of the polymer substrate 2a to achieve the required opacity. The optical density of each layer alone can typically be approximately 0.2 to 0.5. Preferably, three or more layers are applied to each surface, overlapping each other. In a preferred embodiment, at least one of the opacifying layers (preferably one on each surface of the polymer substrate 2a) is made electrically conductive, for example, by adding a conductive pigment. This reduces the effect of static charges that might otherwise accumulate on the security document during handling. The opacifying layers 2b are preferably applied to the polymer substrate 2a before manufacturing the security device 10 described herein, using a printing process such as gravure printing, although in other cases the opacifying layers could be coated onto the substrate or applied by offset, flexography, lithography, or any other convenient method.Depending on the security document design, the opacifying layers may be omitted along the gaps on one or both surfaces of the polymer substrate to form window regions (which may be full windows, half windows, or a combination of both) as described above. This can be achieved through an appropriate pattern of the opacifying layers during the application process. In alternative constructions, the opacifying layers 2b could comprise preformed self-supporting layers (which optionally include openings to form windows later) that are then laminated to the polymer substrate 2a. In this case, the opacifying layers could be polymeric or of fibrous construction, such as paper, making the security document a “paper / polymer hybrid” construction. In other embodiments, as shown in Figure 34(b), the security device 10 could be formed on a conventional document substrate 2. Such substrates are typically fibrous in nature and comprise, for example, paper or regenerated cellulose (for example, as described in WO-A-2020156655). As before, the relief structure of surface 20 is disposed on a first surface 3a of the substrate 2, and the printing layer 30 is applied to the opposite surface 3b. It is also possible to form the security device 10 on a substrate other than the document substrate 2. For example, the security device 10 can be formed on its own substrate, resulting in a security article 1 such as a security thread, strip, foil, or patch. Before or after this occurs, the security article substrate can be attached to or incorporated into a security document 100. An example of this is shown in Figure 34(c), where the security device 10 is formed on a security device 2' substrate, such as a transparent polymer film (e.g., PET), either before or after the 2' substrate is attached to the security document 100. This 2' security device substrate will typically be thinner than a document substrate 2 (e.g., on the order of 30 to 50 microns thick rather than 100 microns or more).The embossed surface 20 is formed on a first surface 3'a of the substrate 2', and the printing layer 30 is formed on a second surface 3'b of the substrate 2'. In this example, the security article 1 is shown affixed to a first surface 3'a of the security document substrate 2 with the security device 10 (or at least a portion thereof) over a window region 51 of the document formed by an opening through the document substrate 2, as is typically the case when the document substrate 2 is paper or similar material. It is also possible to locate such a security article 1 with the security device 10 in a non-windowed region 50 of the document substrate 2, since the combination of the embossed surface 20 and the printing layer 30 may still be visible due to the transparent or translucent nature of the device substrate 2'.The security articles 1 can be applied alternatively to polymer-type document substrates, in window regions, half-window regions, and / or non-window regions thereof. When the substrate 2 on which the security device 10 is formed is translucent instead of transparent, the appearance of the common image CI will typically be different when viewed in reflected light versus transmitted light, and may also be different when viewed in reflected light from different sides. Figures 35(a)-35(b) illustrate this with reference to a simple modality in which the common image comprises a set of parallel straight lines in a rectangular area.As shown in Figure 35(a), the surface relief structure 20 is formed from a colorless cured material 20a and is applied to a first surface of the translucent substrate 2 (for example, in a windowless or half-windowed region of a paper or polymer substrate). The surface relief structure 20 comprises a set of raised in-line elements corresponding to the parallel lines of the image. On the opposite surface of the substrate 2, the printing layer 30 is applied and comprises a set of in-line elements, again corresponding to the parallel lines of the image, which are aligned with the raised elements of the surface relief structure 20. The ink 30a from which the printed lines are formed can be yellow, for example.As shown in Figure 35(b)(i), when the safety device is viewed in reflected light from the side where the observer Oi is located, only the surface relief structure will be visible, while the contribution of the printing layer 30 is substantially obscured by the substrate 2. Therefore, the common image CI appears as a colorless set of parallel lines made visible by the reflective nature of the cured material 20a. When the same device 10 is viewed in transmitted light (from either side), the printing layer 30 is visible, and therefore the common image now appears as a set of parallel yellow lines against a colorless background (or rather, the background will have the same color as that of the substrate 2). The common image will be tactile as a result of the surface relief structure. Figures 36(a)–36(b) show an additional modality that is the same as that in Figures 35(a)–35(b), except that here the cured material 20a forming the surface relief structure carries a colored tint, for example, blue. Therefore, when the safety device 10 is viewed in light reflected from the side where the observer Oi is located, only the surface relief structure will be visible, while the contribution of the printing layer 30 is substantially obscured by the substrate 2, as shown in Figure 36(b)(i). Thus, the common image CI may appear as a blue rectangle with an overlaid set of parallel lines made visible by the reflective nature of the cured material 20a, as shown.Alternatively, depending on the intensity of the blue tint in the cured material 20a and the relative heights of the raised elements and the base layer, the background area could appear a much lighter (or even colorless) color compared to the raised elements, resulting in the appearance of a set of parallel blue lines. When the same device 10 is viewed in transmitted light (from either side), the print layer 30 is visible, and the common image now appears as a set of parallel green lines against a rectangular blue background. Alternatively, if the blue tint in the base layer of the surface relief structure is very light, the background may appear substantially colorless. The color of the lines results from a mixture of the color of the cured material 20a and that of the ink 30a. The common image will be tactile as a result of the surface relief structure. The opacity level of substrate 2 can also be used to create different visual effects from the same security device configuration. This is illustrated with reference to the modality in Figures 37(a)–37(c), in which three copies of a security device with the same construction are provided on a security document 100. Security devices 10a, 10b, and 10c each comprise a surface relief structure 20 formed from a cured material 20a having a colored dye (e.g., blue) on a first surface of substrate 2, and an aligned print layer 30 on the opposite surface formed from an ink 30a (e.g., red). The only difference between the three security devices 10a, 10b, and 10c is their peripheral shape, which differs here to quickly identify the three devices. Security device 10a is circular, 10b is square, and 10c is triangular.As best shown in the cross-section of Figure 37(a), the circular security device 10a is located in a half-window region 52 of security document 100, in which one of the opacifying layers 2b is present, but not the other, so that the area is translucent. The square security device 10b is located in a (full) window region 51, in which both opacifying layers 2b are absent, making this area transparent. The triangular security device 10c is located in a windowless region 50 of security document 100, which is translucent (but less so than the half-window region 52). Figure 37(b) shows the appearance of the security document from the viewpoint of observer Oi in reflected light. The circular security device 10a in the half-window region 52 appears as a set of separate parallel blue lines against a background that has the same color as the substrate 2 (here it is assumed that the tint level and relative heights of the raised elements against the base layer are such that the base layer appears substantially colorless), since the contribution of the printing layer 30 is obscured by the substrate 2. The square security device 10b exhibits a set of purple in-line elements in a transparent window, resulting from a mixture of the blue raised elements in the surface relief 20 and the red printing elements 30.The triangular security device 10c exhibits a set of blue inline elements against a background that has the same appearance as substrate 2 and is therefore similar in appearance to security device 10a. When security document 100 is viewed in light transmitted from observer position Oi (Figure 37(b)(ii)), the three security devices 10a, 10b, and 10c appear to exhibit a set of purple lines caused by the mixed colors. Thus, the appearance of the security device group changes between reflective and transmissive viewing modes. Similarly, when the security document is viewed from the opposite side (observer O2), as shown in Figure 37(c)(i), the triangular security device 10c and the circular security device 10a each exhibit a set of reference lines (corresponding to the color of the printing layer 30) because the contributions of the surface relief structure are now hidden by the translucent nature of substrate 2 in these regions. The square security device 10b still appears as a set of purple lines in a transparent window. In transmitted light, as shown in Figure 37(c)(ii), each of the three security devices exhibits a set of purple lines, as before. In this way, complex effects can be achieved in which the security document exhibits at least three different color appearances, depending on the side from which the document is viewed and the viewing mode.It will be appreciated that while in this example three separate safety devices 10 have been used to illustrate the principle, the same can be applied to different laterally displaced parts of a single safety device 10. That is, each part of a safety device could be located in any of: a window region, a half-window region, and a windowless region, and preferably a mixture of such regions is provided. In an evolution of the invention, greater complexity can be achieved by additionally providing an integral print mark 60 on the substrate 2. The print marks are formed during the manufacture of a document substrate, rather than being applied to the substrate during subsequent processing. Typically, a print mark can be integrated into a multilayer polymer document substrate during the same process that applies the opacifying layer 2b to the core substrate 2a, for example, by gravure printing. Therefore, the integral print mark 60 will be in precise registration with the opacifying layers 2b and particularly with any of the window regions or half-window regions that 52 107nn / C7n7 / B / vi define. Such print marks may be incorporated into security devices of the type described herein (in addition to the print layer 30) by arranging the first region Ri to partially or totally overlap the print mark 60 or otherwise interact with it (for example, appearing to abut, surround, or interlock with the print mark). It will be appreciated that the degree of registration between the print mark 60 and the rest of the security device 10 may not be as precise as the registration between the surface relief structure 20 and the print layer 30, since it is formed in a separate, prior process (not in line with the application of the surface relief structure 20 and the print layer 30). Some examples of security devices 10 incorporating print marks 60 will now be described with reference to Figures 38(a) to 42. Figures 38(a), 38(b), and 38(c) are cross-sections through a simple embodiment of a security device 10 formed on a substrate 2 having a print mark 60, showing three possible arrangements of the print mark 60. In each example, the security device 10 comprises a surface relief structure 20 formed from a colorless cured material and a print layer 30 formed from a colored ink, e.g., yellow. The common image is that of a set of parallel lines in a rectangular area. In the embodiment of Figure 38(a), a print mark 60 in the form of a blue rectangle (formed by a semi-transparent blue-tinted ink) is located on the surface of the transparent core substrate 60 adjacent to the print layer 30, with an opacifying layer 2b located between them.Alternatively, as shown in Figure 38(b), the same print mark 60 could be located on the opposite surface of the transparent core substrate 2a. Alternatively still, the print mark 60 could be distributed between both surfaces of the core substrate 2a; for example, as shown in Figure 38(c), a first half 60a of the print mark could be located on one side of the core substrate 2a, and a second half 60b on the other. If the opacifying layers 2b have sufficient optical density, the safety devices 10 shown in Figures 38(a), 38(b), and 38(c) will all exhibit the same appearance, as shown in Figure 38(d).In light reflected from the viewpoint of observer Oi, the common image will appear as a colorless rectangle (having the same color as the opacifying layer 2b) with a set of lines on it made visible by the reflective nature of the cured material (Figure 38(d)(i)). In light transmitted from either side, the contributions made by the printing layer 30 and the printing mark 60 will now be visible as shown in Figure 38(d)(ii), resulting in the common image 53 hi O7nn / C7n7 / B / vi showing a blue rectangle with green lines superimposed on it. If the opacifying layers are more translucent, the device shown in Figure 38(a) will appear as shown in Figure 38(d) as before, but the devices in Figures 38(b) and 38(c) will exhibit a blue tint in the reflection in the areas where the print mark is on the observer side of the substrate.While in the preceding examples the integral print mark 60 has been located so that it is covered by at least one of the opacifying layers 2b, this is not essential, and the print mark 60 could be located on an outer surface of the substrate 2. The print mark is still considered integral with the substrate 2 since it is formed during the fabrication of the substrate 2 rather than during subsequent processing of the substrate into security documents. As before, the print mark 60 can be applied in line with the opacifying layers 2b, for example, through gravure printing. Figures 39(a)–39(b) illustrate one embodiment that uses this approach. Here, the security device is located in a half-window or windowless region of a polymer substrate where at least one opacifying layer 2b is present in the transparent core substrate 2a.The common CI image observed in transmitted light is a full-color photographic portrait (Figure 39(b)(i)). The image is formed in CMYK color channels (although RGB could alternatively be used). An integral print mark 60 is incorporated into an outer surface of substrate 2 during its manufacture and is configured to provide one of the color components of the portrait, for example, cyan. To form the security device, a surface relief structure defining the same portrait is applied to the same surface of substrate 2, over and aligned with the print mark 60. The surface relief structure is formed from a colorless cured material and provides tactility to the common image as before. On the opposite surface of the substrate, a print layer 30 comprising the magenta, black, and yellow components of the portrait is applied.When the security device is viewed in reflected light from observer Oi's position, the contribution of printing layer 30 is obscured by opacifying layer 2b, and therefore the common image appears as a monochromatic, multi-tonal version of the portrait in cyan. When the security device is viewed in transmitted light from any side, the full-color version of the image can be seen. Another example is shown in Figures 40(a)-40(b). Here, the security device 10 has a simpler design, with the common image comprising a set of parallel, separate lines in a rectangular area. The security device is formed in a windowless region of the substrate 2, which includes a print mark 60 on the outside of the second surface 3b thereof. Here, the print mark 60 is a blue rectangle. The print layer 30 is applied over the print mark 60 and comprises a set of in-line elements corresponding to those of the common image, printed in an ink such as yellow. A surface relief structure 20, formed in a colorless cured material, is applied to the opposite surface of the substrate 2 and defines a set of parallel, raised in-line elements.When the safety device 10 is viewed in reflected light from observer position O1, the common image appears as a colorless region (matching the appearance of substrate 2) with a set of overlapping lines, made visible by the reflective nature of the cured material. This is shown in Figure 40(b)(i). In transmitted light (Figure 40(b)(ii)), the contributions from print layer 30 and print mark 60 cause the common image to appear as a set of green lines against a blue rectangular area. The green color results from a mixture of the print mark color and the ink color that forms print layer 30. When the device is viewed in reflected light from observer position O2, the image appears as a set of yellow lines on a blue background (Figure 40(b)(iii)). In a variant of this embodiment, shown in Figures 41(a)-41(b), the same security device is now located in a transparent window region 51 of the substrate 2. The print mark 60 is also located in the transparent window. The appearance of the security device 10 will now be the same in reflected and transmitted light, and from either side of the device, comprising a set of green lines against a blue background. Figure 42 shows an additional embodiment similar to that in Figures 39(a)-39(b). In this case, the black component of the full-color portrait provides the print mark 60, although any or more of the components could be formed in this way. In this embodiment, the relief structure of surface 20 is configured to encapsulate the print mark 60, that is, to completely cover the print mark 60 and seal it from contact with the atmosphere or anything external. In this way, the print mark 60 is protected from external influences, and the service life of the security device is improved. In another example, a registered 'border' effect could be applied using this method around a hidden gravure printing mark (registration to the original mark as standard). For example, the molded tactile structure could define only an outline of the image, while the printing mark defines the entire image. Optionally, the substrate itself could carry a colored tint, for example, in one or more of the opacifying layers. This color will contribute to the overall appearance of the image in transmitted light and can therefore act as a color channel in a 'full color' image. In each of the preceding examples, the molded tactile structure could take several different forms depending on the desired tactility and / or how the structure contributes to the visible image. In some examples, the molded structure might comprise a series of screen elements, forming a halftone version of the image. In other cases, the molded UV resin might cover the entire image (sharing its periphery or matching certain features to reveal the registration) and might have a textured top surface. In still other cases, the molded structure might follow the contours of a 3D version of the image. In all the preceding modalities, the printing layer 30 was formed from one or more visibly colored materials (e.g., inks) so that the common image is visible to the naked eye under standard lighting conditions, e.g., white light. However, in all modalities, it is possible to form the printing layer 30 using one or more substances that are sensitive to stimuli such as wavelengths of non-visible light and / or that exhibit different behaviors outside the visible spectrum (which can be detected by suitable camera equipment). For example, one or more of the materials (e.g., inks) forming the printing layer 30 could be luminescent (e.g., fluorescent or phosphorescent) and / or could absorb certain non-visible wavelengths (such as IR).It is also possible to form the printing layer 30 from materials with other safe effects, such as optically variable inks, pearlescent inks, iridescent inks, metallic inks, electrically conductive inks, thermochromic inks, magnetic inks, etc. Figures 43(a) to 43(d) show some examples of security devices that use one or more inks that are luminescent in response to UV wavelengths. All of these modalities are tactile due to the presence of the surface relief structure 20, as before, which here is formed from a colorless cured material 20a. In the modality of Figure 43(a), the entire print layer 30 is formed from a material 30a that appears in a first color under standard visible illumination (e.g., white light) and luminescent in the same color under appropriate UV illumination. The common image is that of the digit “5”. For example, under standard visible illumination, the common image CIv may exhibit a yellow image of the digit “5”, and under non-visible (UV) illumination, the common image CIn will again be of a digit “5” that avoids yellow light.In the modality of Figure 43(b), the print layer 30 is formed from a material 30a that is colorless (invisible) under standard illumination, so under these conditions the common CIv image 56 is a colorless digit “5” that is made visible by the reflective nature of the cured material 20a. Under appropriate non-visible illumination (e.g., UV), the material 30a is luminescent in a selected color (e.g., yellow) so that the device now appears to display a colored digit 5. In the configuration shown in Figure 43(c), the print layer 30 is formed from a material 30a that, under standard illumination, has a visible color (e.g., green) and is luminescent with a different color (e.g., yellow) under non-visible illumination (e.g., UV). Therefore, under visible light, the common image CIV is a green 5” digit, while under UV light the device's appearance changes, and the common image CIn now appears as a yellow 5” digit. In more complex examples, two or more materials could be used to form the print layer 30, some sensitive to non-visible wavelengths and others not, or multiple sensitive materials that exhibit different color changes relative to each other.For example, in the configuration shown in Figure 43(d), the print layer 30 is divided into two halves by line ZZ. The left half of the print layer is formed from a first material 30a that is not UV-sensitive and appears in one first color (e.g., green) under visible light. The right half of the print layer 30 is formed from a second material 30b that appears substantially in the same first color (e.g., green) under visible light and emits light of a different second color (e.g., yellow) when illuminated under suitable non-visible light (e.g., UV). Therefore, under standard visible illumination, the common CIv image appears as a complete representation of the digit “5” in green (the two halves match each other in color).However, under appropriate non-visible illumination (e.g., UV), only the right half of the digit is visible and exhibits a color change, appearing yellow, thus revealing the pattern hidden within the printing layer 30. The opposite arrangement could also be provided, where in visible light the right and left hands of the '5' might appear different from each other (e.g., one is red and the other blue), while under UV illumination both areas might emit the same color (e.g., yellow). It is also possible to use two or more UV-sensitive materials that match under visible light and each exhibit different luminescent colors under UV illumination. Examples of suitable inks are described in WO-A-2004 / 050376 and WO-A2018 / 206936. Figures 44(a)-44(b) show an additional embodiment in which the printing layer 30 comprises substances 30a, 30b, and 30c that emit red, green, and blue light, respectively. The embodiment is otherwise the same as that of Figures 9(a)-9(b) above. Under illumination from a corresponding excitation waveband (e.g., UV), the device exhibits a full-color version of the common image. Examples of suitable substances are described in WO-A-2020 / 030893. The substances may be invisible under standard visible illumination. In this case, as shown in Figure 44(b)(i), in visible light the common CIv image will appear colorless and will be carried by the reflective nature of the relief structure of surface 20. Under UV illumination, the printing layer 30 will be excited, and the full-color RGB image will be displayed.In a variation of this example, print layer 30 could comprise three color components that combine to display a full-color image under standard visible light (as in Figures 44(a)-44(b)), but only one of the materials emits light under UV illumination. For example, all three components might appear red, green, and blue under white light, and only the green material might be fluorescent, for example, emitting yellow light under UV. Therefore, when the device is viewed under white light and the lighting conditions are then changed to UV, the image appears to change from full color to a single color. Figures 45(b) and 45(c) show two modes that use infrared (IR) absorbing materials in the print layer 30. For comparison, Figure 45(a) shows a mode in which the print layer 30 is a standard colored ink 30a that does not absorb the IR spectrum. When viewed with the naked eye under standard lighting, the common CIV image appears as the digit “5” in the color of material 30a, for example, yellow. The image is not visible in the IR spectrum. In the mode of Figure 45(b), the print layer 30 is formed from a material 30a that has a visible color, such as yellow, and is IR absorbing. When viewed with the naked eye under standard lighting, the common CIV image again appears as the digit “5” in the color of material 30a. When viewed through a suitable camera in the IR spectrum, the same digit “5” is now visible as an absorbing area. It is also possible to use a mixture of materials.Therefore, in the configuration shown in Figure 45(c), the left half of the print layer 30 is formed by a first material 30a, which is colored and non-IR absorbing, while the right half is formed by a second material 30b, which has the same visible color as the first material 30a but is IR absorbing. When viewed with the naked eye under standard illumination, the common CIV image reappears as the digit “5” in the color displayed by both materials 30a and 30b (e.g., yellow). When viewed through a suitable camera in the IR spectrum, the left half 18a of the digit “5” is no longer visible, while the right half 18b appears as an absorbing area. In all the preceding examples, the arrangement of the print layer on one side of the substrate and the relief structure on the other means that it is possible to apply both simultaneously. This achieves extremely high registration between the print layer and the relief structure because there is no movement of the substrate between the application of the two components: both are applied to opposite surfaces of the substrate in the same position along the substrate (in the direction along which the substrate moves through the manufacturing apparatus – the machine direction), at the same time. The substrate could be in the form of a sheet or a grid. The apparatus, materials, and methods suitable for forming the relief structures described herein are described in WO-A-2018 / 153840 and WO-A-2017 / 009616. In particular, the relief structures can be formed using the in-line molding devices detailed in WO-A-2018 / 153840 (for example, the one designated 80 in Figures 4(a) and 4(b) therein), by using an engraving tool 85 that carries a suitably designed micro-optical structure from which the desired relief structure shape can be molded. Similarly, the mold-curing apparatus and methods described in section 2.1 of WO-A-2017 / 009616 (for example, in Figures 4(a) to 8 therein) can also be used to form the relief structures currently described, by replacing the relief 225 carried by the molding tool 220 with an appropriate relief from which the desired shapes can be molded.In particular, it should be noted that, while WO-A-2017 / 009616 describes the use of the apparatus to form focusing elements, the same apparatus can be used to form any desired relief structure by appropriate reconfiguration of relief 225, including as provided for in the present description. Regardless of the molding apparatus used, the curable material(s) from which the relief structure is molded may be applied directly to the tool that carries the desired relief shape (e.g., engraving tool 85 in WOA-2018 / 153840 or molding tool 220 in WO-A-2017 / 009616), or the curable material(s) may be applied directly to the substrate on which the relief structure is to be formed and then brought into contact with the tool (e.g., by printing the tool onto the deposited curable material). Both options are described in the aforementioned documents. Preferably, the last option is used and the curable material(s) are applied to the substrate by screen printing as detailed in document WO-A-2018 / 153840, before forming the desired relief structure.If the first option is used, it should be noted that, preferably, the relief of the surface of the molding tool is not cleaned between the application of the curable material on it and its contact with the substrate, so that a base layer of curable material remains connecting the protrusions of the relief structure together on the substrate (the base layer will be much lower than the protrusions). Suitable curable materials are described in WO-A-2017 / 009616, section 2.1. UV-curable materials are preferred. Curing of the material(s) preferably takes place while the molding tool is in contact with the curable material against the substrate. In all the above modalities, the transparent curable material in which the surface relief structure 20 is formed can be of various different compositions. The curable material is preferably radiation-curable and may comprise a resin that can typically be of one of two types, specifically: a) Free radical curing resins, which are typically unsaturated resins or monomers, prepolymers, oligomers, etc. containing vinyl or acrylate unsaturation, for example, and which are crosslinked through the use of a photoinitiator activated by the radiation source employed, for example, UV. b) Cationic curing resins, in which ring opening (e.g., epoxy types) is effected by the use of photoinitiators or catalysts that generate ionic entities under the radiation source employed, e.g., UV. Ring opening is followed by intermolecular crosslinking. The radiation used for curing will typically be UV radiation, but it could include electron beam, visible, or even infrared or longer wavelength radiation, depending on the material, its absorbance, and the process used. Examples of suitable curable materials include UV-curable clear acrylic-based etching lacquers or those based on other compounds such as nitrocellulose. Suitable UV-curable lacquers include UVF-203 from Kingfisher Ink Limited and photopolymer N0A61, marketed by Norland Products, Inc., New Jersey. Due to the nature of the mold-cured process, the resulting relief structure will typically include a base layer of material on top of the substrate, connecting the relief protrusions at their base. In many cases, this base layer is integral with the relief structure and is formed by the same curable material(s), resulting from the shape of the mold relief and / or the manner in which the curable material is pressed between the substrate and the molding tool during processing. An example of such a base layer and its formation is described in WO-A-2017 / 009619, Figure 8. It is also possible to provide (alternatively or, furthermore) a base layer in the form of a pedestal layer, which is applied at an earlier stage. Apparatus and methods for providing such a pedestal layer are described in WO-A-2017 / 09620, Figures 8 to 12. An example of a suitable mold-curing process for forming surface relief structures 20 suitable for use in the safety devices described herein shall be described with reference to Figures 46(a) and 46(b) herein, which show the structure 20 only schematically. The process is shown applied to a support layer 201, comprising a transparent or translucent film, which may be the aforementioned substrate 2 or could be another substrate 2' subsequently applied to the substrate 2. Figure 46(a) depicts the apparatus from a side view, and Figure 46(b) shows the support layer in a perspective view; the manufacturing apparatus itself has been removed for clarity. A transparent curable material 205 is first applied to the support layer 201 using an application module 210a comprising a stamped printing cylinder 211 supplied with the curable material from a doctor blade chamber 213a via an intermediate roller 212. For example, the components shown could be part of a flexographic printing system. Other printing techniques, such as lithography, screen printing, or gravure, could also be used. Printing processes such as these are preferred, since the curable material 205 can then be deposited onto the support 201 only in selected regions 202 thereof, the size, shape, and location of which can be selected by controlling the printing process, for example, by appropriately setting the pattern on the cylinder 211.However, in other cases, a total coating method could be used, for example, if the surface relief structure is to be formed over the entire support 201. The curable material 205 is applied to the support 201 in an uncured (or at least not fully cured) state and can therefore be either fluid or a moldable solid. The support 201 is then conveyed to a molding module 220, which herein comprises a molding tool 221 in the form of a cylinder bearing a surface relief 225 that defines the shape of the relief structure of the surface to be molded in the curable material 205. As each region 202 of curable material 205 comes into contact with the cylinder 221, the curable material 205 fills a corresponding region of the relief structure, forming the surface of the curable material in the shape defined by the relief. The cylinder 221 can be configured so that the relief structure 225 is provided only in the regions corresponding to the shape and position of the first regions 202 of the curable material 205. Once formed into the correct surface relief structure, the curable material 205 is cured by exposure to the appropriate curing energy, such as R radiation from a source 222. This preferably takes place while the curable material is in contact with the surface relief 225, although if the material is already sufficiently viscous, this could be done after separation. In the example shown, the material is irradiated through the support layer 201, although the source 222 could alternatively be positioned above the support layer 201, for example, inside the cylinder 221 if the cylinder is formed from a suitable transparent material, such as quartz. Alternatively, the curable material 205 could be applied directly onto the molding tool 221 instead of onto the substrate 201. This can be done in a general manner or following a pattern. Typically, in methods where the curable material is applied directly to the molding tool 221, the curable material is applied to substantially fill the trenches 121, as well as to form a thin layer of curable material over substantially the entire surface of the molding tool 221 in the first region, i.e., over the relief features on the molding tool, as well as the raised areas. There is no cleaning / scraping stage. After the molding process, this thin layer of curable material forms the integral base layer of the surface relief structure. In alternative methods, the curable material 205 may be applied to the molding tool so that it is present only within the trenches 121, for example, by using a scraper or other removal means to remove material from the top of the raised areas.In such examples, a bonding layer is then applied over substantially the entire surface of the die-cut form 221, i.e., covering both the filled recessed areas of the trenches and the raised areas between them. The curable material of the bonding layer may or may not have the same composition as the curable material 205 in the trenches. In particularly preferred embodiments, the composition of the bonding layer may be selected to improve the adhesion between the first curable material 205 and the backing layer. The bonding layer is applied using a bonding layer application module. It is desirable that the bonding layer be applied continuously and homogeneously at the level of the mold; therefore, it is preferably applied in a metered manner using a combination of a groove die and a transfer roller. The bonding layer may be partially cured before the molding tool and the substrate come into contact. hi O7nn / C7n7 / B / viIn all embodiments of the invention, the printing layer 30 can be applied to the substrate using any convenient printing technique, but preferably one that does not engrave the substrate. Particularly preferred techniques are gravure, lithographic, flexographic, wet or dry offset, inkjet, or micro-intaglio printing. If the printing layer 30 is to comprise multiple printing jobs, these are preferably collected on a transfer roller or blanket before being applied together to the substrate. Preferably, when multiple inks are used, they are registered precisely with each other to such a degree that any registration error between them is too small to be perceptible to the naked eye. For example, the translational registration from color to color (i.e., in the machine direction x₀ in the transverse direction y) can be within + / - 5 µm.The tilt registration (i.e., rotational alignment) can be within 0.02 degrees. The shade registration (i.e., the degree of stretch of one color's coverage relative to another) can be within 0.01%. Such registration levels are not achievable with intaglio printing, and therefore color reproduction is significantly better with the present invention. Documents WO-A-2018 / 153840 and WO-A-2017 / 009616 also describe printing stations, which can be arranged downstream of the molding apparatus described above (but, alternatively, could be located upstream, or at the same point along the machine direction explained below). Printing stations such as these are suitable for applying any printing layer 30 to the opposite side of the substrate from which it bears the molded relief structure. The apparatus described in WO-A-2018 / 153840 can achieve particularly high registration between such molded relief structures and the printed elements. For example, in preferred methods, the relief structure and the print layer are preferably registered with each other with sufficient accuracy that any registration error is too small to be perceived by the naked eye. Preferably, translational registration (i.e., in the machine direction x₀ in the transverse direction y) is within 150 pm (+ / - 75 pm). Conveniently, tilt registration (i.e., rotational alignment) is within 1 degree (preferably less than 0.1, more preferably less than 0.05, and most preferably less than 0.02 degrees). Advantageously, tonal registration (i.e., the degree of stretch of one component relative to the other) is within 0.01%. The precise registration achieved will depend on the consumables used in the machine (substrate, inks, resin, printing plates) as well as the actual machine configuration. It is highly advantageous for the relief structure of surface 20 and the printing layer 30 hi oznn / cznz / B / vi to be applied to opposite surfaces of substrate 2 simultaneously. That is, in the same position along the transport path in the machine direction. This makes it possible to achieve the highest registration between the two components. Figure 7 of WO-A-2018 / 153840 shows a suitable apparatus for achieving this. Figure 47 shows a schematic example of this in the case where the relief structure of surface 20 and the printing layer 30 are applied to the first and second surfaces, respectively, of a document substrate 2 (which may be a halftone or a foil). However, the same principles can be applied to the construction of an item such as a security thread, in which case the substrate 2 will be replaced by some other film, typically thinner, transparent, or translucent. The relief structure of surface 20 and the printing layer 30 can be formed using any of the processes described above.For clarity, Figure 47 depicts only selected components of the apparatus used to form the relief structure of surface 20 and the printing layer 30, specifically, a molding tool 221 (e.g., as shown in Figures 46(a)-46(b)) and a common printing roller 302, which is supplied with three inks 30a, 30b, and 30c via inking rollers 303a, 303b, and 303c. No other process line components are shown. The curable material(s) can be applied to the substrate 2 upstream of the molding tool 221 or directly onto the molding tool 221. The molding tool 221 and the printing roller 302 are arranged on opposite sides of the transport path along which the substrate 2 is transported, to form a (low-pressure) contact zone through which the substrate 2 passes.At each location along the polymer substrate 2, its first surface 3a comes into contact with the molding tool 221 at the same time as its second surface 3b comes into contact with the printing roller 302. As a result, the relief structure of surface 20 and the printing layer 30 are formed at each point on the substrate simultaneously. This has the significant advantage that any deformation experienced by the substrate 2, as a result of changes in processing temperature or the like, will be exactly the same when the relief structure of surface 20 is applied to the polymer substrate 2 as when the printing layer 30 is applied. The substrate does not have time to expand or contract between the instant the relief structure of surface 20 is applied and the instant the printing layer 30 is applied, since they occur at the same time.As such, a very high degree of registration between the two components is automatically achieved. The arrangement shown in Figure 47 has the disadvantage that, since the contact zone 64 hi O7nn / C7n7 / B / vi between the molding tool 221 and the printing roller 302 constitutes the first point of contact between the substrate and the molding tool 221, the transparent curable material 205 from which the relief structure of surface 20 is formed will be substantially uncured when it enters the contact zone. As such, the pressure applied between the molding tool 221 and the printing roller 302 must be low to avoid damage to the relief structure of the molded surface 20. Figure 48 shows an improved arrangement in which the formation of the surface relief structure 20 and the application of the printing layer 30 can still be considered simultaneous because the curable material 205 is still in contact with the surface relief on the molding tool 221 at the contact zone between the molding tool 221 and the printing roller 302. The curable material(s) can be applied to the substrate 2 upstream of the molding tool 221 or directly onto the molding tool 221. The substrate is wrapped around a portion of the molding tool 221 from a first point on the roller 61, where the molding of the surface relief structure 20 begins, to the contact zone with the printing roller 302, at which point the surface relief structure 20 will be relatively well cured, preferably fully cured.As such, the pressure between the two components 221, 302 can be increased relative to that of the arrangement in Figure 47, since material 205 is relatively hard and less prone to damage. This improves the quality achieved in the printing layer 30 formation process. Another benefit of the arrangement shown is the increased wrapping length of substrate 2 around the printing roller 302, which also allows for extended curing. Substrate 2 remains in contact with the printing roller 302 from the contact zone location to the exit roller 62. Simultaneous application of the surface relief structure and the printing layer is preferred, but not essential. Figure 49 illustrates an illustrative arrangement for sequentially (rather than simultaneously) applying the two components 20, 30 to opposite sides of a substrate 2 (here in the form of a sheet). This can be described as forming the two components in-line in the same pass. The arrangement generally comprises a printing and molding module 410 for forming the surface relief and a printing station 420. The substrate enters the apparatus at arrow A and exits at arrow B. A curable material 205 is first applied to one side of the substrate sheet 2 as it passes through a contact zone formed by the screen printing cylinder 411a and the intermediate roller 412a.However, as described above, other printing techniques, such as lithographic, flexographic, offset, or inkjet printing, may also be used. The sheet 2 is then conveyed to the molding tool 421a in the form of a cylinder that defines the shape of the surface relief structure to be molded into the curable material 205. Once formed into the desired surface relief structure, the curable material 205 is cured by exposure to the appropriate curing energy, such as UV radiation from source 222. This preferably takes place while the curable material is in contact with the surface relief 225, although if the material is already sufficiently viscous, this could be done after separation. The substrate sheet 2, now bearing the relief structure of the cured surface 20, is conveyed to the printing station 420. In this example, the printing station 420 is a lithographic printing apparatus, comprising a stamped printing cylinder 302 selectively supplied with one or more inks 30a, 30b, 30c via the inking rollers 303a, 303b, 303c. The image is transferred from the printing cylinder 302 to a blanket roller 306 and then to the substrate 2 in a contact zone between the blanket roller 306 and an impression roller 305. The substrate 2, now bearing both the reliefs of surface 20 and the printing layer 30 on opposite sides, is conveyed out of the printing module 420 via arrow B. Suitable substrates on which the described devices can be formed are described in WO-A-2017 / 009616, section 1, and the apparatus / methods for applying opacifying layers to them are described in section 4, including the formation of window regions. Preferably, the opacifying layers are applied to the substrate before the formation of the described safety devices. For example, the sheet-like material supplied to the apparatus of WO-A-2018 / 153840 may comprise a polymer substrate of the type described in WO-A-2017 / 009616, already provided with one or more opacifying layers. The safety devices described herein may be arranged in a window region defined by the opacifying layers, or in a non-windowed region. Some preferred aspects of the invention are presented in the following clauses: Clause 1. A safety device comprising: a substrate having a first and a second opposing surfaces; on the first substrate surface, a surface relief structure formed from a cured, at least semi-transparent material; and on the second substrate surface, an impression layer; i O7nn / C7n7 / B / vi wherein, in at least a first region of the security device, the surface relief structure and the printing layer are each defined according to the same image and are aligned with each other, so that the surface relief structure provides tactility to the image. Clause 2. A security device in accordance with Clause 1, wherein the curable material is colorless and the printing layer defines a multicolor image, preferably a full-color image, with the highest preference being an RGB or CMYK image. Clause 3. A safety device according to Clause 1, wherein the curable material carries a dye of a first color and the printing layer defines an image in at least a second color so that, when viewed in combination, a multicolored version of the image is visible. Clause 4. A security device in accordance with Clause 3, wherein the first color is one of red, green and blue, and the printing layer defines the image in the other two of red, green and blue, so that when viewed in combination, a full-color RGB version of the image is observed. Clause 5. A safety device in accordance with any of the preceding Clauses, wherein the height of the surface relief structure varies according to the image. Clause 6. A security device in accordance with any of the preceding Clauses, wherein the security device further comprises a second region in which one or both of the surface relief structure and the printing layer are present. Clause 7. A safety device in accordance with any of the preceding Clauses, wherein the substrate is transparent in at least part, preferably the entire first region of the safety device. Clause 8. A method of manufacturing a security device, comprising forming a surface relief structure on a first surface of a transparent substrate by mold-curing a curable material that is at least semi-transparent thereon, and printing a print layer on the second surface of the transparent substrate, wherein the surface relief structure and the print layer are each defined according to the same image and aligned with each other, in this manner the surface relief structure provides tactility to the image. Clause 9. A method in accordance with Clause 8, wherein the formation of the surface relief structure and the printing of the printing layer are simultaneous, and take place in the same position along the machine direction, at the same time. i O7nn / C7n7 / B / vi Clause 10. A method in accordance with Clause 8 or 9, configured to provide the security device with any of the features of Clauses 1 to 7.

Claims

1. A safety device comprising: a substrate having first and second opposing surfaces; on the first surface of the substrate, a surface relief structure formed by one or more cured material(s), at least semi-transparent; and on the second surface of the substrate, a printing layer;wherein, in at least a first region of the security device in which at least a portion of the substrate is transparent or translucent, the surface relief structure and the printing layer are each defined according to a common image and aligned with each other, the surface relief structure exhibits a first set of features of the common image and the printing layer exhibits a second set of features of the common image, such that the common image is exhibited by the surface relief structure and the printing layer one in combination with the other and the surface relief structure provides tactility to the common image.

2. A safety device according to claim 1, wherein the first and second sets of features are the same to each other, the surface relief structure and the printing layer each exhibit all the features of the common image.

3. A safety device according to claim 1, wherein the first and second sets of features are different from each other, and the first set of features and / or the second set of features are a subset of the features of the common image.

4. A security device according to claim 3, wherein one or more of the common image features are included in both the first and second set of features and are exhibited in both the surface relief structure and the printing layer.

5. A safety device according to claim 3 or 4, wherein the first set of features consists of the common image features located in a first portion thereof and the second set of common image features consists of the common image features located in a second portion thereof, the first and second portions being different from each other, preferably laterally displaced from each other.

6. A safety device according to any of the preceding claims, wherein the first set of features corresponds to a first color component of the common image, and the second set of features corresponds to at least a second color component of the common image.

7. A security device according to any of the preceding claims, wherein either: the first set of common image features, exhibited by the surface relief structure, preferably the entire surface relief structure, is located laterally in its entirety within the limits of the second set of common image features, exhibited by the printing layer; and / or the second set of common image features, exhibited by the printing layer, preferably the entire printing layer, is located laterally in its entirety within the limits of the second set of common image features, exhibited by the surface relief structure.

8. A security device according to any of the preceding claims, wherein the common image is defined at least in part by a series of separate image elements, either: the surface relief structure comprises a plurality of separate raised elements forming the image elements that define the first set of features of the common image; and / or the printing layer comprises a plurality of separate printing elements forming the image elements that define the second set of features of the common image.

9. A safety device according to claim 8, wherein the common image is a halftone image, the image elements vary throughout the series in terms of their size, shape, color, optical density and / or separation to carry the common image, the series of hi O7nn / C7n7 / B / vi image elements is preferably arranged in a regular grid.

10. A security device according to claim 8 or 9, wherein the image elements are rectilinear or curvilinear line elements, point elements, or elements having the form of coded marks, preferably alphanumeric or typographic symbols.

11. A safety device according to any of the preceding claims, wherein the surface relief structure includes a plurality of separate protrusions, which are joined together by a lower base layer, the base layer preferably extending over a peripheral region surrounding the plurality of separate protrusions.

12. A security device according to any of the preceding claims, wherein the common image is a multi-tonal and / or multicolor image, preferably a grayscale image or a full-color image.

13. A safety device according to any of the preceding claims, wherein at least one curable material is colorless and the print layer exhibits one or more visible colors, the print layer with the highest preference being an RGB, CMYK or OGV (orange, green, violet) print layer.

14. A safety device according to any of claims 1 to 12, wherein at least one curable material carries a dye of a first color and the printing layer exhibits at least the first color and / or a second color, preferably configured so that when viewed in combination, a multicolored version of the common image is visible.

15. A security device according to claim 14, wherein the first color is one of red, green and blue, and the printing layer displays the other two of red, green and blue, so that when viewed in combination, a full-color version of the common image is visible.

16. A security device according to claim 14, wherein the first color is one of cyan, magenta, yellow and black and the printing layer exhibits the other three of cyan, magenta, yellow and black, so that when viewed in combination, a full-color version of the common image is visible.

17. A safety device according to any of the preceding claims, wherein the printing layer exhibits two areas of different respective colors and an intermediate area in which the color gradually transitions between the different respective colors.

18. A security device according to any of the preceding claims, wherein the at least one curable material carries a dye of at least one color and the printing layer has a visual opacity such that the appearance of the common image color is different when the security device is viewed from the relief structure side of the surface compared to when viewed from the printing layer side.

19. A safety device according to any of the preceding claims, wherein the printing layer comprises one or more substances that are sensitive to non-visible wavelength(s), preferably UV or IR, the printing layer being optionally invisible under white light illumination.

20. A security device according to claim 19, wherein the printing layer comprises substances that emit red, green, and blue light under illumination from a corresponding excitation waveband, so as to display a full-color version of the common image.

21. A safety device according to any of the preceding claims, wherein the height, width, length and / or geometry of the surface relief structure varies according to the common image.

22. A safety device according to any of the preceding claims, wherein the safety device further comprises a second region in which one or both of the surface relief structure and the printing layer are present, the second region being either laterally displaced and not overlapping with the first region, or interlocked with the first region. i O7nn / C7n7 / B / vi 23. A safety device according to claim 22, wherein in the second region the surface relief structure is present and forms any of: one or more optical elements such as focusing elements, facets, prisms, pyramids or caustic elements; a tactile structure or a matte structure.

24. A safety device according to claim 22 or 23, wherein in the second region the printing layer is present and forms any of: a background print, a visually uniform area, a color-changing layer, a printed color filter, and a series of images such as a series of micro-images or an interlaced image.

25. A safety device according to claims 23 and 24, wherein in the second region the relief structure of the surface forms a series of focusing elements and the printing layer forms a series of images located approximately in the focal plane of the focusing elements, and the series of focusing elements and the series of images are configured to cooperate with each other to generate an optically variable effect.

26. A safety device according to any of the preceding claims, wherein the substrate is transparent or translucent along the first region of the safety device.

27. A plurality of substantially identical safety devices, each according to any one of claims 1 to 26, in each of which the respective surface relief structures and printing layers have the same position relative to each other.

28. A security document comprising a document substrate and a security device thereon, the security device being in accordance with any of the preceding claims, wherein the document substrate may or may not act as the security device substrate, the document substrate preferably comprising paper, polymer, cellulose or a hybrid thereof.

29. A security document according to claim 28, wherein the first h I O7nn / C7n7 / B / YIAI region of the security device is located at least partly in a window or half-window region of the document substrate, which has a lower optical density than the surroundings thereof.

30. A security document according to claim 28 or 29, wherein the document substrate is translucent and the first region of the security device is located at least partly in a windowless region of the document substrate.

31. A security document according to any of claims 28 to 30, wherein the first region includes parts located respectively in at least two of: a window region of the document substrate, a half-window region of the document substrate, and a non-window region of the document substrate.

32. A security document according to any of claims 28 to 31 comprising at least two security devices, each according to any of claims 1 to 26, wherein the at least two security devices are located respectively at least partly in at least two of: a window region of the document substrate, a half-window region of the document substrate, and a non-window region of the document substrate.

33. A security document according to any of claims 28 to 32, wherein the document substrate comprises a core polymer substrate with at least one opacifying layer disposed on one or both surfaces of the core polymer substrate, optional gaps in one or more of the opacifying layers forming window or half-window regions of the document substrate.

34. A security document according to claim 33, wherein the document substrate further comprises an integral print mark, preferably located between at least one of the opacifying layers and the core polymer substrate, wherein optionally, the integral print mark is defined according to the common image and is aligned with the surface relief structure and the print layer, the integral print mark exhibiting a third set of features of the common image, such that the common image is exhibited by the surface relief structure, the print layer and the integral print mark in combination with each other.

35. A security document according to any of claims 28 to 34, wherein the security device substrate is affixed to or incorporated into the document substrate, preferably over a transparent or translucent region of the document substrate that is optionally formed as an opening.

36. A security document according to any of claims 28 to 35, wherein the security document is any of: a banknote, passport, identification document, identification card, bank card, driver's license, visa, stamp, check or certificate.

37. A method of manufacturing a safety device, comprising, in any order or simultaneously: forming a surface relief structure on a first substrate surface from one or more at least semi-transparent curable material(s);and printing a print layer on the second surface of the substrate, wherein, in at least a first region of the security device in which at least a portion of the substrate is transparent or translucent, the relief structure of the surface and the print layer are each defined according to a common image and aligned with each other, the relief structure of the surface exhibits a first set of features of the common image and the print layer exhibits a second set of features of the common image, such that the common image is exhibited by the relief structure of the surface and the print layer one in combination with the other and the relief structure of the surface provides tactility to the common image.

38. A method according to claim 37, wherein the formation of the surface relief structure and the printing of the printing layer are carried out in alignment with each other, the tilt registration between the surface relief structure and the printing layer is preferably 1 degree or less, more preferably 0.1 degrees or less, even more preferably 0.05 degrees or less, with the maximum preference 0.02 degrees or less.

39. A method according to claim 38, wherein the formation of the surface relief structure and the printing of the printing layer are simultaneous, and take place at the same position along the machine direction, at the same time.

40. A method according to any of claims 37 to 39, wherein the printing layer is printed by gravure printing, lithography, flexography, wet or dry offset, inkjet printing or micro-intaglio.

41. A method according to any of claims 37 to 40, wherein the formation of the surface relief structure comprises mold-curing one or more at least semi-transparent curable material(s) onto the first substrate surface by: providing a molding tool having a defined mold relief thereon corresponding to the surface relief structure; applying the at least semi-transparent curable material(s) to the molding tool or to the substrate; and bringing the molding tool and the substrate into contact with the at least semi-transparent curable material(s) between them, thereby forming the at least semi-transparent curable material(s) into the surface relief structure;and during and / or after contact, cure the one or more curable material(s) to at least semi-transparent to retain the surface relief structure.; 42. A method according to any claim 41, wherein at least the semi-transparent curable material(s) is / are applied to the relief of the molding tool to substantially fill the recesses of the mold relief and form a layer of at least the semi-transparent curable material(s) over the elevations of the relief structure.

43. A method according to any of claims 37 to 42, configured to provide the safety device with any of the features of claims 1 to 26.

44. A method of manufacturing a security document, comprising providing a document substrate or either forming a security device in the document substrate according to any of claims 37 to 42 or forming a security device in a security device substrate according to any of claims 37 to 42, and then applying the security device substrate or incorporating the security device substrate into the document substrate.

45. A method according to claim 44, configured to provide the security document with any of the features of claims 28 to 36.

Images