Introduction
Part one of this series about optimizing microprinting described 2D font design and artwork customization for better resistance to artwork re-origination. Part two introduced novel color, registration and plate engraving depth strategies that can provide offset and intaglio microprinting with improved resistance to traditional offset counterfeiting to supplement the conventional role microprinting plays against digital simulation. Part three showed how microprinting inspection ergonomics can be facilitated through advantageous placement and design strategies. Now, part four considers optimization of microprinting in tactile and matte lamination plate artwork in plastic substrates, including translation of the novel color strategies from part two to use cases in colorless and inkless lamination plate applications.
Bonding of multiple thin polymer layers is necessary for manufacturing plastic security card substrates. This process is done by application of heat and pressure between two metal lamination plates and produces clear embossed tactile and/or matte security designs on the substrate surface (without consumables) if engraved or textured artwork is added to the lamination plates. Many conventional security design strategies typically associated with 2D printed artwork can be adapted for use in lamination plate feature graphics, including but not limited to the focus of this paper series: microprinting. Some examples include dynamic font size and placement of multiple microprinting types in the same location (Figure 1), partial or bisected characters (Figure 2), pattern-level customizations that complicate step-and-repeat counterfeiting processes (Figure 3) and intersection of microprinting with personalization data, such as bearer portrait images (Figure 4). However, inkless lamination plate features differ from printed artwork in some important ways, such as an absence of color and the addition of tactile feature height and matte surface roughness as potential new design variables.
Figure 1. Lamination plate feature containing microprinting text of variable size. The wavy offset microprinting line visible in the reflected and oblique light images is located directly under the plate feature microprinting and may be intended to facilitate simultaneous inspection. The gradual font size increase that can be seen in the coaxial light image raises the difficulty of copy/paste artwork replication. Additional steps to customize the font in different parts of the line are also options.
Figure 2. Lamination plate design containing incomplete tactile microtext characters. Individual characters are bisected at the edges of the microprinting that comprises the large clear tactile “MARYLAND” text in the coaxial image. This transforms the pattern from a purely text microprinting design into nonrepeating line art, increasing the complexity and labor needed to replicate it. Further customizations of the font or 2D microprinting pattern by warping or distortion are also possible.
Figure 3. Lamination plate feature containing a nonrepeating microprinting pattern. The baseline tilt differs depending on where a particular microprinting string is placed within the larger pattern, adding work to step-and-repeat counterfeiting processes. Additional 2D microprinting customizations can also include font-level customizations or pattern-level warps/distortions. The laser engraved expiration date resides underneath the tactile microprinting within the card body, contributing resistance to alteration
Figure 4. Lamination plate microprinting feature intersecting a laser engraved portrait image. As with the personal data text in Figure 3, laser engraved portrait images can be applied through lamination plate features to mark interior layers of a card body. Attempts to remove or alter the portrait risk damage to the plate feature, while inclusion of microprinting makes the plate feature both difficult to restore once damaged and hard to counterfeit using low-resolution simulation processes.
Tactile and Matte Features
Plate features can be generally divided into two groups: tactile and matte. Tactile plate features are embossed areas of the substrate surface produced from artwork engraved into a lamination plate. Matte features consist of light-scattering art produced from roughened areas of the lamination plate that contrast with the glossy specular reflectance of the substrate surface. Although both tactile and matte plate features can be checked in a limited way by touch, the subtle details that make a plate design hard to counterfeit can be inspected visually with the document tilted against a light, or with magnification, particularly in the case of lamination plate microprinting. A tactile plate feature is shown in Figure 5 and a matte plate feature is shown in Figures 6.
Figure 5. Lamination plate feature containing only tactile areas, with no matte art. As with many tactile features, this design is composed entirely of thin lines (including microprinting) without large block shapes. It is visible in either oblique or coaxial light in the figure graphics, though document users would typically inspect it by tilting against a light source, or with magnification. Compare to Figure 6.
Figure 6. Lamination plate feature containing only matte areas, with no tactile art. Unlike the tactile design in Figure 5, this matte design contains large bold shapes (including negative microprinting). It is more visible in coaxial light than oblique light in the figure graphics, through document users can inspect this feature easily by tilting against a light source, or with magnification. Compare to Figure 5.
Contemporary security documents often include plate features of both types adjacent to one another as shown in Figure 7.
Figure 7. Lamination plate feature containing a mix of tactile and matte areas. Because both tactile and matte features are applied in a single lamination step from one plate, there is little possibility of misregistration between tactile and matte graphics on the surface of a genuine document. However, counterfeiters attempting to simulate tactile and matte elements with two separate steps/processes must overcome difficult microscopic registration and resolution problems.
Because simulating a tactile feature can rely on different methods than simulating a matte feature, and security designs of higher graphical complexity can be made far more difficult to counterfeit than simple art, lamination plate microprinting optimization can benefit from more than just including both plate feature types. The following sections propose that intentional integration of tactile and matte artwork into comprehensive microprinting designs, where the two types cannot be attacked as independent elements, is the path to microprinting plate features that are more resistant to counterfeiting and simulation. Some design strategies for plate feature microprinting are presented below. Issuers should determine which, if any, such strategies are of potential utility given the capabilities of their own plate manufacturing and/or substrate lamination workflows.
Grayscale Analogy
Plate feature artwork elements are often regarded as either tactile or matte, as though tactile features were limited to only a single height and matte features to just a single surface texture. However, both types are more analogous to image grayscales and could be included to a greater or lesser extent in different areas of a lamination plate design. Just as different areas of a grayscale image encompass a range of values between white and black, tactile features could include a range of heights to be “more” or “less” tactile and matte features could include a range of surface textures to be “more” or “less” matte (or glossy).
Viewed this way, the height of tactile features and the reflectivity of matte features are additional variables for designers to customize alongside two-dimensional artwork. Some examples in issued documents include Figure 8, in which the oblique light image shows what appear to be different tactile heights in different areas of the design (even though on this card the tactile heights are uniform) and the coaxial image shows matte finishes placed on top of some tactile surfaces. Similarly, Figure 9 shows matte effects with different surface roughness that appear as different gray levels in the coaxial image and are also placed on top of tactile surfaces, as in Figure 8.
Figure 8. Lamination plate feature containing a mix of tactile and matte elements. Although the tactile elements are of similar height throughout, in oblique light the shadows make some tactile areas appear higher than others. If intentionally designed, tactile elements of multiple heights could be included to create different real textures. Additionally, comparing the oblique and coaxial images shows the matte shapes surrounding the center of the flower are on top of a raised tactile surface.
Figure 9. Lamination plate design containing multiple matte intensities, which appear as different gray levels in the vertical stripes in the coaxial light image. As in Figure 8, compare the oblique and coaxial images to see that the matte features are on top of raised tactile surfaces.
Importantly, the examples in Figures 8 and 9 contain no microprinting, but the mockups shown in Figures 10 through 15 illustrate how microprinting design can benefit by extension of these concepts. A basic microprinting mockup with characters of three discrete tactile heights and three discrete matte surfaces is illustrated in Figure 10 (though more than three would add greater complexity) and a mockup illustrating an alternate design strategy that extends a matte effect across both tactile and nontactile areas is shown in Figure 11. Building further on this foundation, customization of microprinting at the sub-character level can provide more advantages.
Figure 10. Mockup of lamination plate microprinting text containing tactile structures of varying height and matte surfaces of varying intensity. On the left, three discrete tactile heights are shown, and the right contains three discrete matte surfaces. More or fewer discrete levels might be possible, depending on an issuer’s lamination plate manufacturing capabilities and the degree of detail achievable through the lamination process itself.
Figure 11. Mockup illustrating a lamination plate microtext design in which placement of tactile and matte effects are incongruent, adding complexity and offering the potential for unconventional tilt visual effects. As with all prior mockups, issuers should assess manufacturability of such a design based on their own lamination plate production and lamination workflows. Compare to Figures 8 and 9, which also show examples of matte effects on top of tactile surfaces.
For example, the mockup in Figure 12 shows a plate feature microprinting design that incorporates the three discrete tactile heights and three matte levels in different locations within individual characters, each of which remains readable as text despite the internal partitioning. Figure 12 is a conceptual extension of the intaglio microprinting strategies introduced in part two of this series, in which each individual microtext character was subdivided into multiple color and depth elements that can force counterfeiters to demonstrate high registration in addition to high resolution. The internal composition of each character is dynamic, making step-and-repeat counterfeiting of the 3D tactile and matte effects impossible even though the 2D character shapes are static. Manufacturability of the design in Figure 12 is assumed for purposes of illustration, but not all platemaking or substrate manufacturing technologies can accommodate this level of detail. The exact size of the microprinted characters also remains intentionally undefined. Designers might consider including a mix of large and small text that could be inspected both with and without magnification, including text larger than conventional microprinting.
Figure 12. Mockup of lamination plate microprinting characters in which each character is comprised of a unique arrangement of different tactile and matte effects. This artwork is still recognizable as readable microtext, allowing it to fulfill its conventional role against low-resolution simulation methods. However, counterfeiters seeking to simulate tactile and matte effects with two different processes are also presented with a difficult microscopic registration challenge or the microprinting will be illegible.
Figures 12 presents counterfeiters with several problems. First, multiple tactile and matte effects must first be reverse engineered and then simulated, instead of just one of each. This complicates not only the physical/hardcopy counterfeiting steps but also the difficulty of imaging and analyzing surface contours in clear plastic. The already-challenging prepress task of copying a colorless, inkless lamination plate feature is made even harder as the 3D complexity of the genuine plate design increases, as suggested in prior work. Second, if a counterfeiter attempts to simulate the tactile and matte effects using two different technologies, output of the two steps would risk microscopic misregistration. If tactile and matte areas were out of register, legibility of the microtext in Figure 12 could be affected. Third, use of a counterfeiting process that cannot replicate tiny microprinting details would be risky, since the plate feature design is based on microprinting that cannot be simulated using low-resolution methods. That a counterfeiter would face these problems simultaneously makes simulation of the entire plate microprinting design more complicated than the individual elements alone.
Split Fountain Analogy
The concept in Figure 12 has two limitations. First, it contains only three discrete levels of tactile and matte effects, which constrains potential graphical complexity. Second, since the artwork customization occurs at a size even smaller than individual microtext characters and would produce no large macro trend visible to the naked eye across the full width of a card, the design in Figure 12 is inspectable only with magnification. Both limitations can be addressed by introducing macro-scale continuous tactility and matte transitions that are analogous to split fountains, a printed feature common in security documents of all types and familiar to many document users.
In printed artwork, a split fountain is a continuous transition between colors, created by partially blending two inks together on press, which can be inspected both with and without magnification depending on the design of the associated artwork. Although anchored by only two spot ink colors, the color transition between them shows a theoretically infinite number of blended hues. In the colorless, inkless environment of plate features, conceptual adaptations of split fountain visual effects could include a continuous transition from high to low tactility, from bold to subtle matte or other combinations encompassing continuums of values instead of the discrete height or matte levels introduced in Figures 10 through 12. The purpose is to create a microprinting plate design that 1) approximates an infinite number of discrete levels of tactility or matte to make reverse engineering difficult and protect the microprinting from simulation and 2) shows a macro effect observable without magnification that reminds users of a split fountain transition. This is relevant because a key problem with microprinting is the need to inspect it with magnification, which limits its utility.
The mockup in Figures 13 through 15 shows one possible way to address these goals. While the artwork in Figure 12 resists reverse engineering and step-and-repeat counterfeiting because the interior composition of each character is unique, in Figures 13 through 15 the locations of the tactile and matte components within every 2D character are the same throughout the pattern and it is only the tactile height and matte roughness that vary. This allows both variables to be gradually transitioned across the full width of the card body shown in Figure 14, creating two macro patterns reminiscent of grayscale split fountains that can be seen or touched without magnification. First, the matte interior of each character is bold at the upper left, more subtle towards the center and gradually bold again at the lower right. Second, the tactile outlines are taller at the top of the document and gradually shorten until the texture nearly vanishes at the bottom. The complete microprinting pattern would show the effects of both transitions simultaneously at a macro level, allowing inspection of the feature by touch and with tilt but without magnification, though inspection with magnification would provide additional value.
Figure 13. Mockup of lamination plate microprinting in which the placement of tactile and matte characteristics within the 2D artwork is the same for each character, with a tactile interior and matte outline. Differences between one character and the next are due solely to tactile height and/or matte roughness. This microtext design is just a precursor to Figures 13 and 14, which demonstrate how tactile and matte gradients can facilitate inspection of lamination plate microtext without magnification. 
Figure 14. Mockup showing the extension of the artwork in Figure 12 to a larger pattern extending across a full plastic card substrate. The 2D design of the microtext, including tactile and matte location, is identical throughout. But within each character the tactile height is varied vertically, and the matte roughness is varied horizontally, where gradual gradients within each create macro visual/tactile effects that can be inspected both with and without magnification. Compare to Figures 12 and 14.
Figure 15. Key to the four corners of card graphic shown in Figure 13, illustrating continuous variation of tactile height and matte intensity independently of one another. The top two images show the upper left and upper right corners of the card, with high tactile, and the bottom images show the lower left and lower right corners with low tactile. Similarly, matte is subtle on the left and bold on the right. The pattern looks different in each corner, though the 2D art is identical. Compare to Figures 12 and 13.
As in Figures 10 through 12, the absolute size of the text in Figures 13 through 15 is undefined. Issuers should consider the limits of their own manufacturing capabilities, and the advantages and disadvantages of using larger or smaller text (or both) in plate artwork. Additionally, the strategies in Figures 10 through 15 could all be integrated together into a single plate feature design in which the font and microprinting pattern are also optimized in 2D (as described in part one of this series) or extended beyond microprinting to other types of security artwork compatible with lamination plate features (guilloche patterns and security halftones, for example).
Conclusion
All lamination plate features in contemporary plastic security documents contribute resistance to counterfeiting because they are difficult to capture with conventional scanning and photographic technology, but opportunities for improved design remain. This paper has presented some novel strategies for microprinting plate features intended to inhibit counterfeiter reverse engineering, prevent step-and-repeat counterfeiting processes, and produce microprinting patterns that can be inspected both with and without magnification. A key idea is that tactile and matte effects are not simply present or absent, but that tactile height and matte intensity might be optimizable as additional design variables to create lamination plate features with increased complexity, given the necessary plate and substrate manufacturing capabilities. Further, parallels with grayscale images and split fountain transitions were drawn, to the conclusion that even inkless, colorless microprinting plate features can be designed to remind document users of familiar printed security features.
Joel Zlotnick is employed by the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory as a physical scientist. His current work involves research in security artwork and design techniques in security printing. He is an instructor on counterfeit detection at the US Department of State Foreign Service Institute.
Jordan Brough is employed by the Homeland Security Investigations Forensic Laboratory as a forensic document examiner, specialising in adversarial analysis and counterfeit deterrence. Jordan spends his time examining suspect documents and consulting with United States security document designers.
Troy Eberhardt is employed by the US Immigration & Customs Enforcement Homeland Security Investigations Forensic Laboratory. He supervises the Research and Development Section at the laboratory, which specialises in identifying and mitigating vulnerabilities within travel documents.
Tyra McConnell is a Forensic Document Examiner at the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory. She provides training on security documents and develops presentations and e-learning courses regarding counterfeit detection.
Elizabeth Gil is employed by the Homeland Security Investigations Forensic Laboratory as a forensic document examiner. Elizabeth divides her time between conducting examinations on travel and identification documents and testing security documents for vulnerabilities.
