Prior work on security fiber optimization discussed security fiber characteristics and combinations of diverse security fiber types together in one substrate. Planchettes are tiny disks that are like security fibers in many respects, except for their shape and size, and can themselves be optimized as distinct security substrates separate from the paper of the host document. Besides being easier to see, planchettes can be carriers for security fibers, and their surfaces are large enough to accept printed images. This provides options for customizing planchettes through graphic design strategies typically associated with static printed artwork. Further, most planchettes seem intended for reflected or UV light inspection, though they can be hard to inspect in reflected or UV light when embedded inside of (and concealed by) the document substrate. Accordingly, designing planchettes for transmitted light inspection may both overcome this limitation and facilitate new security roles for planchettes.
While the shape of a security fiber might be described as straight, curved, or wavy, planchettes have an edge contour that depends on how they are punched. Typical planchette shapes include round, hexagonal, and rectangular, as shown Figure 1. More exotic planchette contours could include multiple shapes joined together, sawtooth or irregular edge patterns, interior cutouts within planchettes (for example, an oval hole inside a triangular planchette), or many other possibilities. Not only would such planchettes need to be manufacturable themselves but would also have to be compatible with papermaking (or polymer extrusion) processes for the security substrates that contain them. Issuers and suppliers will come to different conclusions about what is possible and appropriate for their own document products.
Figure 1. Some possible planchette edge contours, including round (left) and hexagonal (center) planchettes and long, flat, rectangular security fibers that are large enough to be treated as planchettes (right). Triangular, pentagonal, or other shapes could also be conceived. More exotic shapes/contours that cannot be described just as polygons may be possible, depending on manufacturing capabilities.
Another important characteristic of planchettes is color, which can mean different things: the color of a planchette substrate in visible and/or ultraviolet (UV) light, the visible and/or UV color(s) of security fibers embedded in a planchette substrate, or the visible and/or UV color of printed images on a planchette surface. Paper planchettes with various visible, invisible, UV bright, and UV dull color responses are shown in Figures 2 through 4, though more combinations are clearly possible. Most likely, the colors in Figures 2 through 4 were created by incorporating pigment in the planchette substrate, but surface printing is another way to color planchettes and is discussed further below. Which method is chosen may affect color saturation and contrast in transmitted light if higher amounts of pigment inside a planchette substrate may block light better than a thin surface printing, or the intensity of a UV response is improved if the UV pigment is on the planchette surface, etc.
Figure 2. Round planchettes of various reflected light colors, including red, blue and yellow. Compare these visible colors to the UV responses of the same planchettes that are shown in Figure 3.
Figure 3. The same planchettes as in Figure 2 but illuminated in UV light. Planchettes may or may not respond to UV, and for those that do the UV response may or may not be the same as the visible light color. For example, the red planchette in the left image darkens in UV, but the red planchette in the right image glows blue, and in other documents red planchettes just glow red. Compare to Figure 2.
Figure 4. An invisible UV-responsive planchette. The planchette is invisible in reflected light (left) and it can be seen in oblique light (center) by those that know to look for it, but it really becomes visible only in UV. Invisible planchettes may be attractive from a design standpoint because they do not compete with visible art but offer limited security value because they require a UV light source for inspection. Compare to Figures 8 through 10.
Although out of scope in this paper, planchette “color” might also include specific infrared (IR) characteristics. This approach might apply in circumstances where visible planchettes could interfere with machine readability (in manufacturing quality control systems, passport readers, banknote processing equipment, etc.) but invisible planchettes with reflected or transmitted IR characteristics might not. Further, IR imaging might simply produce better captures than visible or UV light imaging for planchettes embedded inside the document substrate, where the planchette surfaces are concealed.
Composition and Security Fibers
Paper planchette substrates can also incorporate security fibers, but with significantly different design conventions and goals as compared to security fibers added directly to a security document substrate. First, security fiber density is typically low throughout macro security substrates, but fiber density in a planchette substrate must be very high to ensure that every planchette contains a cluster of fibers when punched. Second, planchettes containing multiple fibers together can be easier for document users to locate than a single isolated security fiber due to their larger size and better visibility. Third, because the fibers are clustered, each planchette becomes a training tool that helps document users identify how many different fiber types are present in the planchette. In contrast, in typical security document substrates, users may have to search to locate even a single security fiber; when one is found, users still don’t know whether other kinds of security fibers are also present throughout the substrate. Fourth, monochromatic security fibers added directly to security document substrates are randomly placed and unregistered. But security fibers within an individual planchette are collectively bounded by, and therefore registered to, the planchette edge, other fibers, and the tint color of the planchette substrate. A complete discussion of why this internal registration of several disparate color components is important exceeds the scope of this paper, but generally, it can help a planchette resist certain methods of simulation.
Some examples of planchettes containing security fibers are shown in visible light in Figure 5 and UV light in Figure 6. These examples show how a planchette substrate can itself be optimized as an independent security substrate, with multiple substrate color properties and various security fiber combinations. As noted, designers and manufacturers have tremendous flexibility to customize across these variables.
Figure 5. Planchettes containing high densities of blue security fibers (left), or a mix of red and blue security fibers (center and right). The planchette substrate itself is also tinted pink in the center and right images. Although both examples at the center and right contain red and blue fibers, the quantities and sizes of fibers are different. These examples illustrate how a planchette substrate can be optimized independently of the larger security document substrate that contains it. Compare to Figure 6.
Figure 6. The same planchettes as in Figure 5, illuminated with UV. Just as in visible light, the planchette substrate and any security fibers it contains are distinct elements and can be customized with different UV responses. The only UV response in this set is from the planchette substrate in the left image, which glows blue/white in UV, but other configurations of planchettes could incorporate other combinations of substrate and/or security fiber UV responses. Compare to Figure 5.
Figures 1 through 6 illustrate paper planchettes, but other planchette compositions can facilitate specific visual effects. For example, the plastic planchette in Figure 7 is iridescent, but metallic, color shifting, holographic, or other visual effects might also be possible. The planchette in Figure 7 is close to the substrate surface so the iridescent effect is easy to see, but planchettes may not be ideal carriers for exotic visual effects that cannot be seen if a planchette is embedded inside the document substrate.
Figure 7. A hexagonal planchette composed of iridescent material instead of paper. When tilted it produces a pearlescent effect that cannot be mimicked by CMYK, forcing many counterfeiters to undertake additional steps to simulate it. Metallic specular reflection, holographic, or other optical effects might also be possible, but tiny planchettes that are often covered by the substrate might not be optimal carriers for complex visual effects that are more easily added to other document components.
Compared to thin security fibers, the large size and flat shape of planchettes allow them to accept visible and/or UV-reactive printed images. For example, the planchette in Figure 8 was punched from a substrate containing visible artwork and shows only a small part of a larger design. The planchette substrate is the same visible color as the document substrate and is hard to see in reflected light but glows yellow in UV. Importantly, the contour of the planchette edge defines where both the dark surface print and the substrate UV response are bounded, ensuring that these two characteristics are both registered to the planchette edge and, by extension, each other. Again, this internal registration of two different effects produces resistance to certain counterfeiter simulation methods. This planchette is close to the surface of the document substrate, but the reflected light visibility of the dark print would be reduced if it were deeper in the substrate.
Figure 8. In reflected light, printed artwork on the surface of this planchette is visible but the planchette substrate cannot be seen because it is the same color as the document substrate. In oblique or UV light both the artwork and the planchette substrate are visible. Both the artwork and the UV response are registered to the planchette edge, and therefore to one another. Compare to Figures 9 and 10, which show the reverse example: UV printing on a UV-dull planchette surface.
Similarly, the flat rectangular security fiber in Figure 9 and the planchette in Figure 10 each contain UV-reactive microprinting. This combination (planchette + microprinting + UV response) stands out in many ways. It randomly distributes microprinting throughout the document, which is not possible with static surface art. Further, a high-resolution counterfeiting technology that is also compatible with UV printing would be required to simulate the fine UV microprinting details, as opposed to the low-resolution macro color of a planchette substrate tint. Finally, the microprinting placement on each fiber/planchette is unique in relation to the planchette edge even as the general microprinting pattern is recognizable between planchettes, as shown in Figure 11. Planchettes with both static (artwork design) and variable (artwork placement) elements are conceptually analogous to security fibers of the same color, but random positioning in different documents and the random placement can present similar security advantages.
Figure 9. A large, flat security fiber containing UV-reactive microprinting text. Compare to the invisible UV-reactive planchette substrate in Figure 4. Advantages of this format are that counterfeiting tiny microtext requires high resolution printing in addition to the UV ink, and the UV glow might help locate the fiber if it were embedded deep in the substrate. However, this could be a hard feature to inspect since it requires both magnification and UV light at the same time. Compare to Figures 4, 8 and 10.
Figure 10. UV-reactive microprinting like the example shown in Figure 9, as applied to the surface of a planchette instead of a security fiber. Compare to Figures 4, 8 and 9.
Figure 11. UV-reactive microprinting in three planchettes in the same passport, where the placement of the microprinting in relation to the planchette edge is different for each. That each planchette simultaneously shows similar art but different placement confers advantages against certain simulation strategies. Note the larger text in the right image; this may be an intentional variation within the larger microprinting pattern.
However, much like the invisible planchette in Figure 4, document users are challenged to locate or inspect the UV print in Figures 9 through 11 without UV light. Further, UV microprinting is a combination of two second level security features that is complicated to inspect because it requires the simultaneous use of both magnification and UV light. Finally, the legibility of UV microprinting could easily be obscured if a fiber or planchette is embedded too deep in the document substrate, limiting the accessibility of the feature. Despite these limitations, such a strategy may still provide value if it is inexpensive to implement.
Planchettes punched from tinted substrates like those in Figures 2 through 4 are monochromatic, and the printed images on the planchettes in Figures 8 through 11 are also monochromatic. However, multicolor effects could be achieved in non-tinted planchettes printed with multicolor artwork. Multicolor microprinting design was described in prior work and is extendable to planchette microprinting art, though planchette art embedded inside the document substrate can be hard to see. Accordingly, in planchette contexts, artwork concepts should not necessarily be limited to microprinting because bolder multicolor designs with less fine detail might be easier to inspect.
Figure 12 shows a mockup of hexagonal planchettes punched from a substrate printed with parallel stripes of red and blue offset artwork, designed such that each planchette accommodates about four stripes. Observe that each planchette shows the same general stripe pattern, but the placement of the stripes relative to the edge is unique for each planchette. Because such subtle placement variations are unlikely to confuse document users that are just looking for stripes, manufacturers have no need to achieve precise register between the stripes and the location of the edge punch, and the variation introduced by this imperfect registration also conveys advantages. Diversity of art placement within a planchette is analogous to the random distribution of security fibers in a substrate and helps interrupt certain planchette simulation methods.
Figure 12. A mockup of fine stripes printed on the surface of a substrate (left) and on hexagonal planchettes that could be punched from the substrate (right). Although the pattern is recognizably the same in each planchette, the specific placement of the stripes makes each planchette subtly unique. That the pattern is different for each planchette can offer advantages against certain types of planchette simulation attacks. Compare to Figures 13 and 17.
The mockup in Figure 13 shows the same color pattern as Figure 12 but with multicolor microprinting graphics instead of stripes. Figure 13 is superior to Figure 12 because simulating the microprinting details requires counterfeiters to use high-resolution printing processes. But it is also inferior because fine microprinting details could be more difficult for document users to check since planchettes are frequently concealed inside the document substrate. Issuers must determine their own priorities.
Figure 13. A mockup of microprinting printed on the surface of a substrate (left) and on hexagonal planchettes that could be punched from the substrate (right). As in Figure 12, each planchette is unique but also looks generally like the others. This microprinting could be added at low cost and would require both good resolution and good registration to simulate, but if such a planchette were enclosed inside the document substrate the microprinting detail could be masked. Compare to Figures 12 and 17.
Figures 12 and 13 are simplistic mockups intended only to illustrate general concepts and should be extrapolated to capture benefits and avoid limitations of different approaches to planchette graphics. Some examples include more than two visible and/or UV colors, use of visible inks that also feature UV responses, alternating stripes or other shapes with microprinting or other fine graphics, dividing the microprinting colors within words (or even individual characters) instead of between lines, establishing color contrast between ink and fiber colors, and a variety of other combinations and considerations.
A final but important distinction between offset artwork design for full documents as opposed to planchettes is how repeating and nonrepeating artwork is used. Artwork, including simultaneous offset artwork, should be nonrepeating in macro document designs to prevent step-and-repeat counterfeiting. In contrast, repeating artwork may be desirable in substrates from which planchettes will be punched because it ensures each planchette captures a tiny piece of the same artwork pattern regardless of the location from which it is punched in the macro design. Because the placement of the artwork relative to the planchette edges varies, each specific planchette features its own unique artwork placement, making the artwork nonrepeating across a population of planchettes even if the source artwork is repeating. If fully nonrepeating artwork were included in a planchette substrate, the artwork patterns on two different planchettes might look significantly different from one another and could confuse users. Possibly, a compromise between repeating and nonrepeating art could also be used for planchette artwork design where artwork variation is more subtle than in macro document designs.
Designing For Transmitted Light
As discussed in prior examples, a problem in planchette design is that planchettes may be located at any depth within the document substrate. In reflected light, the document substrate may conceal the color of a planchette substrate or the details of any visible printing or special visual effects on the planchette surface. The document substrate may also prevent incident UV from reaching planchette components like UV-reactive security fibers or UV-reactive artwork or may mask the visible fluorescence of these components. For example, Figure 14 shows how reflected light visibility of a planchette with a tinted substrate is dependent on its depth within the document substrate but transmitted light examination can make planchette colors generally more visible regardless of whether their surfaces are concealed.
Figure 14. Visible planchettes at different depths within the 3D structure of a paper substrate. The planchette at the lower right is deeper within the substrate than the two at the left, so it is barely visible in reflected and oblique light. In transmitted light, all three planchettes can be easily seen since all block light similarly regardless of their placement in the substrate. Planchettes are not typically optimized for transmitted light inspection, but this is an area with potential for further development.
In contrast, non-tinted planchette substrates containing no visible artwork are all but invisible in reflected and transmitted light, as shown in Figure 15.
Figure 15. The same invisible UV-reactive planchette shown in Figure 10, as it would be inspected without UV light. Without UV, this planchette is likely to be overlooked unless one already knows it is present and to check for it. Nonetheless, this example provides a mechanism to introduce randomly distributed artwork to documents that can be expanded beyond UV applications. Consider how the characteristics of this planchette affect user ergonomics and the utility of the feature.
Even non-tinted planchette substrates containing visible artwork may be hard to locate or inspect in reflected light if the visible artwork is on the reverse of the planchette, as shown in Figure 16.
Figure 16. Like Figure 8, this planchette contains printed artwork on its surface, but the planchette is upside down and the artwork is concealed as photographed in reflected light in the left image. In transmitted light, the artwork on the opposite side of the planchette can be seen as it blocks light. In reflected or transmitted light, the color of the planchette substrate is like the color of the document substrate, and blends in. Consider how these characteristics affect user ergonomics.
The planchettes in Figures 14 and 16 are more consistently visible in transmitted light than they are in reflected light. Accordingly, even though planchettes are not typically regarded as a transmitted light feature, planchette designs could be optimized specifically for transmitted light inspection to help overcome the limitations caused by planchette embedment inside the document substrate. As just one example, if simultaneous offset technology were used to print identical registered images on the front and back of planchette substrates, transmitted light contrast could be maximized.
Prior work has discussed simultaneous offset, which is the ability of certain security offset printing presses to apply images in register on opposite sides of a substrate. Some concepts from the simultaneous offset series,,,, could be adapted to planchette design, including the use of opaque white inks as shown in Figure 17 (or other specialty inks, like metallics) as just one of many possible examples. In the case of white ink artwork (text, stripes, etc.) printed on a planchette substrate of the same color as the document substrate, the planchette has no reflected light characteristics and would occupy a new niche in the security feature landscape: a native transmitted light feature featuring high-resolution printed images that is also randomly distributed throughout the document substrate. Consider how such a planchette could complement colored security fibers and planchettes and conventional transmitted light features such as watermarks and security threads.
Figure 17. A mockup of microprinting printed in opaque white ink, or another ink color that matches the substrate color in reflected light. In reflected light, the printed artwork shows low contrast with the substrate surface and is nearly invisible, but in transmitted light the ink blocks light. Whether microprinting is best for this application is debatable since tiny details may be lost due to substrate interference, but other art could be used. Consider combining this strategy with simultaneous offset.
Just as Figure 7 illustrated a polymer planchette with iridescent characteristics that allow it to be inspected by tilt in reflected light, polymer planchette substrates optimized for transmitted light inspection could be conceived. Suppose such a planchette substrate were composed of clear polymer, with opaque graphics in the style of security threads like the one shown in Figure 18. Clear polymer planchettes might also facilitate UV light inspection, where the visible response is the same color regardless of UV source placement. However, consider clear planchettes where the UV response changes depending on whether UV is incident on the front or back of the planchette. Figure 19 shows an example of this technique integrated into a clear window in a polycarbonate passport data page. The technique might be adapted to planchette design, though the thickness of a data page window and a planchette are very different, which could impact manufacturability.
Figure 18. A security thread as viewed in transmitted light (left), reflected ultraviolet light (center) and transmitted UV light (right). In transmitted light and transmitted UV light, metallized elements of the security thread block light and appear as dark text. In reflected ultraviolet light, the metallized text enclosed within the security thread cannot block light and is not visible. This security thread example might be extrapolated to planchettes that encompass reflected, UV and transmitted light inspection.
Figure 19. A transparent window in a polycarbonate passport data page as viewed in reflected light (left), reflected UV light (center) and transmitted UV light (right). The multilayer substrate construction is complex and includes multiple printed UV features and substrate layers that block UV light, resulting in different artwork depending on whether UV originates from the front or back. Consider whether this concept might be adapted from this thick multilayer window structure to a thin transparent planchette.
This paper has described several variables germane to the design of planchettes, including shape, visible, and UV substrate color, substrate composition and security fibers, visible and UV surface artwork, and designs for transmitted light inspection. Although each was explored in isolation through the examples in this paper, an idealized planchette design (or designs) could take all these factors into consideration simultaneously and combine them in ways that facilitate ergonomic inspection, prevent easy simulation, and respond to several methods of inspection, including reflected light, UV light, transmitted light, and magnification. The security substrate design concepts presented in prior work on combining security fibers are equally applicable to planchettes, such that multiple planchette types with different characteristics and intended for different modes of inspection could be combined in a single substrate.
Disclaimer: This document represents the opinions of its authors and not necessarily the opinions of the U.S. government. The technologies and strategies described may not be available, appropriate, or manufacturable for all document issuers. The examples shown do not imply anything about the quality of a document, its designer, its manufacturer, or the issuing authority. For informational purposes only.