A Path to the Next Generation of U.S. Banknotes Keeping Them Real (2007) / Chapter Skim
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Appendix C Intermediate-Term Feature Descriptions
Appendix C Intermediate-Term Feature Descriptions
Pages 132-226
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From page 132... ...
• Key Development Risks and Issues -- A discussion of the durability challenges, feature aesthetics, anticipated social acceptability, and description of the key technical challenges that must be addressed during the first phase of the development process to demonstrate the feasibility of the feature idea,
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From page 133... ...
The features described in this appendix are as follows: • Color Image Saturation • Fiber-Infused Substrate • Fresnel Lens for Microprinting Self-Authentication • Grazing-Incidence Optical Patterns • High-Complexity Spatial Patterns • Hybrid Diffractive Optically Variable Devices • Metameric Ink Patterns • Microperforated Substrate • Nanocrystal Pigments • Nanoprint • Refractive Microoptic Arrays • See-Through Registration Feature • Subwavelength Optical Devices • Tactile Variant Substrate • Thermoresponsive Optically Variable Devices • Window
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From page 134... ...
The technique on which this proposed currency feature -- color image satura tion -- is based uses the saturation channel of color images to embed watermarking or other secure data. Color images are usually captured via red (R)
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From page 135... ...
It is expected that this feature would deter the opportunist and the petty criminal counterfeiter and that many professional criminal counterfeiters would be highly challenged in attempting to duplicate or simulate the feature. Furthermore, the would-be counterfeiter would have to reverse-engineer the authentication hardware and software.
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From page 136... ...
Key Development Risks and Issues Durability The durability of this feature should be high, since it is contained in a printed image and the image should be quite robust, as any printed feature would be. Therefore, durability is not an issue.
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From page 137... ...
This feature would only facilitate the authentication of the note, however, and would not be used as a tracking feature. Key Technical Challenges The first key technical challenge would be to make sure that the embedding of the required data in the saturation channel did not noticeably deteriorate the image being watermarked.
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From page 138... ...
Incremental Production Cost The cost of this feature should be very minimal, since it is just another printed feature on the currency. For the required color image, color inks and a more com plex printing process are involved, but the additional cost impact should be low to very low in the volumes of currency produced.
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From page 139... ...
As the substrate is manufactured, these fiber segments are mixed in before the paper is dried. When the finished substrate is illuminated with light, especially laser light, the fibers light up as the incident light emanates from the ends of the fibers.
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From page 140... ...
Furthermore, the costs associated with this technique would be quite low, since the cost of the materials is low, and it is their being embedded randomly that gives the technique value. Materials and Manufacturing Technology Options The manufacturing requirements for this feature would involve paper manu facturing and integrating the fiber fragments into the paper or other substrate material.
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From page 141... ...
Social Acceptability There should be no issues of social acceptability surrounding this feature. Key Technical Challenges The key technical challenge would be the incorporation of the fiber-infusing process into the substrate production process.
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From page 142... ...
Key Milestones The expected key milestones for Phase I would be as follows: • Place fiber fragments in paper substrates to determine the applicability of the technique and any operational or manufacturing difficulties that might arise. • Assess authentication techniques for a phased development of passive and active instrumentation methods over time.
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From page 143... ...
Required Capital Equipment Although there should be no capital costs for the BEP, there might be costs for the substrate manufacturer. Equipment that would prepare, add, and mix any fiber materials with the pulp would be required.
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From page 144... ...
This feature works by cutting a hole in the paper substrate and bonding a transparent Fresnel lens over the hole. The lens is fabricated from plastic and has a curved sawtooth profile, providing the refractive index variations of a lens without the bulk (see Figure C-2)
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From page 145... ...
Holes in paper substrates have been manufactured by De La Rue, Ltd., which has also bonded metal films across these holes. This company believes that plastic can be robustly applied across paper windows.
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From page 146... ...
Key Development Risks and Issues Durability The key durability issue is the attachment of the lens over a hole in the sub strate. Commercial banknote vendors have recently demonstrated the feasibility of attaching metallic foils over holes in paper substrates.
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The committee knows of no plastic films that have yet been adhered to a paper substrate. The manufacturing readiness level is currently low.
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From page 148... ...
The substrate would be delivered to the BEP with the lens already attached, and the BEP would continue to add microprinting using existing processes. Incremental Production Cost Microfabrication techniques should be able to provide this feature at a low incremental cost.
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From page 149... ...
For instance, the intaglio process could impress highly complex depressions into the currency substrate. Additionally, the substrate surface microscopic profile could be prepressed into the substrate material so as to minimize any negative impact on the FRN production process.
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From page 150... ...
But it is clear that anyone wanting to re-create this feature would be greatly challenged. Key Development Risks and Issues Durability This feature should have excellent durability if properly implemented.
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From page 151... ...
Properly designed, it might have characteristics that would enable visually challenged persons, since features for their benefit could also be placed on the note as part of the impression process. Key Technical Challenges The key technical challenges are the development of appropriate patterns and patterns that are compatible with tolerable analysis procedures.
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From page 152... ...
Estimate of Production Cost Compatibility with Current BEP Equipment and Processes The production cost for this feature should be quite low, since only the impres sion of the substrate before, during, or after printing is required. Producing this impression could be an additional step, but it is not much of a complication since the impression process is already known and operational via the intaglio printing already used.
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From page 153... ...
However, there is one key difference between currency production and the electronic imaging tools used by would-be counterfeiters. That difference is the analog versus digital production of the final result.
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From page 154... ...
C-4 the original currency production equipment. The basic intent with this feature is upper and lower to use patterns whose full spatial bandwidth cannot be reproduced completely by digital systems and hence will show a visible defect on such systems, regardless of the image processing used.
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From page 155... ...
There is the risk that digital imaging equipment will advance to the point that this feature would not have value, but if the intaglio printing process is of sufficiently high quality, as it appears to be, this is unlikely. This feature is compelling because of several salient characteristics.
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From page 156... ...
Capabilities such as line-width control, line-space control, edge raggedness of printed lines, and so on all enhance the usefulness of this feature as they are improved. Simulation Strategies Simulating this feature would be done by using the best digital scanning and printing equipment available.
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From page 157... ...
Key Technical Challenges The key technical challenge with this feature is the differential quality of the intaglio spatial bandwidth and that of current and expected digital printers. If the two processes were to come to parity, this feature would have less value than if the printing process of the authentic currency continued to exceed that of digital printers.
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From page 158... ...
The evalu ation would be partly conducted using already available production equipment, so the transition from prototype to production should be fairly swift since only the creation of the intaglio masters would be required for production use. Estimate of Production Cost Compatibility with Current BEP Equipment and Processes The effect on current BEP processes would be minimal, since the current pro cess would generate the feature required.
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From page 159... ...
Required Capital Equipment For a thorough evaluation of this feature's usefulness, access to high-quality digital reproduction equipment would be required. This feature could be in one or more colors and hence color digital reproduction equipment should be available.
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From page 160... ...
appear different depending on viewing angle, and at least one part of the device operates on the basis of diffractive effects. These elements consist of diffractive optically variable devices (DOVDs)
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From page 161... ...
The implementation of more sophisticated versions that include polarization-dependent effects, encrypted images, three-dimensional volume optical effects, and other features appears to be straightforward but less well developed for commercial applications. The nondiffractive components of h-DOVDs are also well established (for example, interference structures are used in optically variable inks, patterned reflective layers on holograms have been demonstrated, and so on)
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From page 162... ...
The additional features to create h-DOVDs could consist of conventional inks (for color images, moiré patterns, and so on) , vapor-deposited thin-film stacks (for interference filters)
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From page 163... ...
Key Development Risks and Issues Durability The durability of an h-DOVD is expected to be comparable with that of a DOVD or an optically variable image (OVI)
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From page 164... ...
Phase 1 Development Plan Maturity of the Technology The separate components of h-DOVDs have already been demonstrated for currency applications. Research and design are needed to define an optimized way to integrate these elements into a single currency feature that provides the desired level of overt and covert protection against counterfeiting and with acceptable manufacturing costs and aesthetics.
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From page 165... ...
2004. The growth of optically variable features on banknotes, in Optical Security and Counterfeit Deterrence Techniques V, R.L.
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From page 166... ...
The need to provide special inks or toners to simulate the real metameric inks would be a significant deterrent to most counterfeiters. Feature Motivation The idea of using inks that display metameric effects in visible light is compel ling, because most counterfeiters use digital printing systems such as color ink-jet or color laser printers to generate their illicit output.
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From page 167... ...
The cyan dye, for instance, is the same for all images. Unless users created their own special inks or toners in the case of electrophotographic laser printers, reproducing metameric inks would be very troublesome.
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From page 168... ...
While the metameric patterns would also be useful to machine readers that could detect detailed data such as their spectra, the main advantage here is that ordinary users with little additional equipment, using either environ mental illumination or inexpensive penlights, could verify the authenticity of a banknote, even in low-light conditions. The only limitation of this feature is that it would require two light sources so that the metameric effects could be seen by hu man observers with normal vision -- either using a penlight kind of device against ambient lighting or using two common light sources in the home or workplace.
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From page 169... ...
It is not expected that this would be a debilitating issue for this feature or its proper use. Key Technical Challenges The key technical issues to be addressed with respect to this feature would be the design of inks that stress many if not most electronic printers to the greatest extent possible.
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From page 170... ...
Key Milestones There are three milestones to pass in order to properly implement this feature: • Develop metameric inks with proper cost and durability as well as adequate metamerism in the expected user environments. • Develop and/or identify simple light sources, such as penlights with filters or LED penlights that could be distributed and used at point-of-sale loca tions, with which to quickly assess the authenticity of the currency.
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From page 171... ...
This feature would be very adaptable to the current BEP operations. Incremental Production Cost It is expected that the cost would be very low because a low volume of ink would likely be used per note.
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From page 172... ...
The pattern can be observed by means of transmitted light, either ambient light (holding the note up to a light) or, more dramatically, a light source (penlight, light table)
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From page 173... ...
Further, dirt that occludes the entire pattern of holes is not typical, again alerting the cash handler. Key Development Risks and Issues Durability Microperforation passes durability tests in other currency.
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From page 174... ...
Key Technical Challenges The key technical challenge for microperforation is that of adding the holes at an appropriate point in the process in order to prevent hole occlusion by subse quent manufacturing steps and to permit correct placement of the feature. Phase I Development Plan Maturity of the Technology It appears that this feature is technically mature, as it is in use in other currencies.
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From page 175... ...
Laser paper removal is also used in other low-cost products, such as greeting cards and cigarette papers. Required Capital Equipment Microperforation requires automated laser microperforation equipment sufficient for the production level required, as well as supporting infrastructure.
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From page 176... ...
Such features would be visible to the unaided eye and would be machine-readable -- the latter gathering data on the unique spectral properties of the inks. These materials might also be well suited for use in metameric inks, of the type described previously in this appendix (see the section "Metameric Ink Patterns")
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From page 177... ...
top middle and bottom Feature Motivation As described above, dispersions of semiconductor or metallic nanocrystals provide unique color and spectral characteristics in an ink format that could be used to form images on currency with complex color characteristics (measured with visible,
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From page 178... ...
In essence, the committee judged this feature highly because it exploits a new class of material to achieve wide-ranging optical properties in printed images or security strips. The extreme level of tunability provides the ability to define complex optical signatures that could be evaluated using suitable measurement apparatus.
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From page 179... ...
The committee expects that the durability, using properly supported matrices, could be as high as that of conventional inks that are currently used in currency applications. Aesthetics The nanocrystal ink feature would be aesthetically neutral.
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From page 180... ...
, the Nanoscale Science and Engineering Center at Rice University is carrying out investigations of toxicity issues with these and related classes of nanomaterials; these activities could be useful to the BEP in assessing any toxicity risk of these inks. Key Technical Challenges The key technical challenge is to demonstrate ink formulations that exploit the unique optical properties of the nanocrystals while at the same time enabling low-cost printing and high durability in nontoxic forms.
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From page 181... ...
Estimate of Production Cost Compatibility with Current BEP Equipment and Processes The nanocrystal ink formulations have the potential to be designed for compatibility with existing BEP printing systems. Incremental Production Cost The cost is estimated to be low to medium -- approximately similar to that of an OVI ink.
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From page 182... ...
Owing to the small dimensions of the patterns, nanoprint can be viewed directly only by means of specialized equipment such as scanning optical microscopes. These nanoprint features can be observed indirectly, however, by exploiting visible and/or machine-readable collective effects such as diffractive or moiré effects.
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From page 183... ...
The previously mentioned collective effects provide a strategy for the use of a nanoprint feature by the general public or by high-speed machine readers without the need for specialized microscopes. Materials and Manufacturing Technology Options Recent research in nanotechnology has produced several methods that can "print" structures and patterns with dimensions in the deep submicron and nano
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From page 184... ...
As a result, nanoprint would be most easily implemented in security strips or other structures that are separately processed and subsequently integrated into the paper. Simulation Strategies Nanoprint, of course, cannot be viewed directly with the unaided eye.
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From page 185... ...
Social Acceptability There are no known concerns regarding social acceptability with respect to nanoprint. Key Technical Challenges The key technical challenge is to produce the nanoprint feature at acceptable cost.
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From page 186... ...
The key assumption is that the basic manu facturing procedures can be scaled to achieve cost-effective operation for currency applications. Estimate of Production Cost Compatibility with Current BEP Equipment and Processes Nanoprint would be incorporated into the paper of the currency through security strips, plastic inserts, or related strategies.
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From page 187... ...
aPPendix c Required Capital Equipment A tool for performing the printing would be needed. The systems for integrating the feature into the paper would be similar to those used in diffractive optical elements or security strips.
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From page 188... ...
. The feature requires the integra tion of an additional material into a currency paper substrate (Bartz, 2002)
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From page 189... ...
Therefore, this type of feature will be technology blocking for all but the state-sponsored class of counterfeiter. Current state-of-the-art security document manufacturers introduced the first of this type of feature.6 These early features have many of the properties envisioned and are compatible with high-volume production methods that will likely lead to only a moderate cost increase over the holographic stripe and embedded security strip.
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From page 190... ...
, a scene height is one-tenth the element thickness. For currency applications, the array must be less than 100 µm thick to fit physically within the thickness of an FRN.
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From page 191... ...
. The embossing of plastic films, which are currently used to make holographic strips at high speed and low cost, has sufficient feature line-width capability for the small pitch lenses; however, improvements in three-dimensional replication accuracy, the shape accuracy, will be needed to produce high-quality very short focal length refractive lens arrays.
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From page 192... ...
Diffractive lenses typically have lower efficiency, which leads to less-distinct and dimmer images. Further informa tion on diffractive elements is presented in the section above, "Hybrid Diffractive Optically Variable Devices." In addition to the refractive and diffractive microoptic lenses described above, microstructures with size and shape on the order of the wavelength of light, 0.5 µm, can create numerous additional optical effects.
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From page 193... ...
The thin regions could be created by laminating the optical devices onto a plastic security strip such as that already used in U.S. currency.
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From page 194... ...
Key Development Risks and Issues Durability The plastic used and the adhesion of this material to the paper have been worked on during the creation of the embedded security strip. A thin plastic strip has been demonstrated; however, this device needs to be as thick as practicable to enhance the working of the device.
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From page 195... ...
Ultraviolet acrylic ink would likely add literally more headache at the BEP. Key Technical Challenges An advanced feature in this class should be close to that used by advertisers for catching and holding the consumer's attention.
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From page 196... ...
Challenges include efforts to do the following: • Add a color three-dimensional perception, which will require printing at micron line widths or integrating advanced microstructure optical devices. • Achieve robust integration of the microoptical device with the paper sub strate, enabling varying size, shape, and positioning of the windows.
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From page 197... ...
This would include a pigment and dye approach, or, alter nately, an interference filter stack; high printing resolution; and the integra tion of advanced dye or pigment with high-resolution offset printing. • Develop robust integration of a microoptic device with the paper substrate, including laminated plastic film optical elements to achieve the required durability.
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From page 198... ...
Incremental Production Cost From the BEP perspective, this material should have a mature product cost 1.5 to 2 times that of holographic strips and significantly higher than that of the cur rent security strip. The holographic strips in high-volume production cost $7/m2 to $9/m2 in 2004, which amounts to $6 to $7 per 1,000 FRNs.
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From page 199... ...
2002. Durability of optically variable devices on bank notes.
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From page 200... ...
2005. Using vacuum roll coaters to produce anti counterfeiting devices.
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From page 201... ...
See-through registration is a visual feature in transmitted light, and although it could be read by a machine, its contribution is to create an overt visual feature primarily for the public and secondarily for the cash handler and teller. A see-through registration feature can be found on many international currencies.
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From page 202... ...
Currently, the BEP has production processes in place that allow for the necessary degree of precise registration in spot colors, and therefore little to no cost would be incurred to implement this new feature. Materials and Manufacturing Technology Options The BEP already has the capability to control the precise location of the printed image on the substrate and, to the committee's knowledge, it appears that the BEP can obtain a level of precision that is necessary for creating the see-through registration feature.
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From page 203... ...
Key Development Risks and Issues Durability With the degradation of the note over its lifetime, the transparency of the FRN may be obscured by the accumulation of dirt, which would limit the effectiveness
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From page 204... ...
Key Technical Challenges The key technical challenge for the see-through registration feature would be the development of a design that took advantage of the nonpixelated, nondigitally addressable image-creation capability of the BEP using its offset spot-color print ing, with the possible inclusion of a substrate color. The design would have to include precision in alignment or registration of the front and back sides of the note that is beyond the capability of desktop systems now and for the next 5 to 10 years.
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From page 205... ...
Key Milestones The milestones for implementing this feature are the following: • Design a test see-through registration feature that is both pleasing to the eye and easy to authenticate and technologically challenging to the ink jet printer, assuming continued improvement in resolution and printing registration. • Test existing BEP printing equipment for precise registration and stability of colors.
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From page 206... ...
Accessed February 2007. Garcia, D.D.
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From page 207... ...
Subwavelength optical elements (SOEs) provide visible images that achieve colors, polarization contrast, and/or other optical effects through the use of structures, such as relief features or narrow conducting wires that have dimensions substantially smaller than the wavelength of light.
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From page 208... ...
Also, the manufac turing baseline and durability established by existing diffractive optically variable device (DOVD) currency features suggests technical feasibility for SOEs.
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From page 209... ...
. The effectiveness of the embossing approach could be reduced by including features in the SOE, such as patterns of isolated subwavelength metal lines, patterns of color, or other hybrid features (see the section above entitled "Hybrid Diffractive Optically Variable Devices")
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From page 210... ...
Social Acceptability The committee does not foresee any social acceptability issues with regard to this proposed feature. Key Technical Challenges The key technical question is whether the embossing-based fabrication ap proaches for SOEs, which are similar to those used for diffractive optical de vices, but require higher resolution, can be scaled up for low-cost manufacturing.
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From page 211... ...
The key assumption is that the basic manufacturing approaches and materials used for SOEs that operate in the infrared and near-infrared will be suitable for SOEs in the visible. Estimate of Production Cost Compatibility with Current BEP Equipment and Processes The SOEs could be integrated into a security strip or other component in a manner similar to that used for diffractive optical devices that are found in other currencies.
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From page 212... ...
Required Capital Equipment New capital equipment would be required. It would be similar to that used for diffractive optical devices but with enhanced resolution capabilities.
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From page 213... ...
Introducing a tactile feature would involve roughening a specific area on the note in such a way that would make it "readable" -- that is, easily detectable and discernible from the tactilely different areas on other denominations. One example of a tactile variant feature could be vertical strips (in the same direction as the existing plastic ribbon)
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From page 214... ...
A tactile variant feature on the FRN is an excellent way to enhance the uniqueness of the cotton and linen substrate, while also creating a first-of-its-kind tactile feature. This feature would be particularly important because for the first time it would allow the visually im paired and the blind to differentiate between the various denominations.
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From page 215... ...
Materials and Manufacturing Technology Options To create a tactile variant feature, a machine process would have to be created at the manufacturing facility of the substrate supplier. The machine would have an abrasive quality that would precisely roughen up the surface in specific areas.
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From page 216... ...
Key Technical Challenges The technical challenges for the tactile variant feature involve establishing the process by which the substrate becomes rough and understanding the manner in which the ink will respond to a substrate with varying levels of roughness. Adding roughened areas to FRNs needs to be done in a such a way that whole sheets of bills can still be printed.
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From page 217... ...
Development Schedule and Cost Estimate It is expected that the Phase I, and indeed perhaps the total development, of this feature could be completed within 2 to 3 years. Estimate of Production Cost Compatibility with Current BEP Equipment and Processes The roughening machine to create this feature would be used by and located at the supplier of the substrate.
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From page 218... ...
by touching it with a finger, for example, changes its appearance. In certain embodiments, such as those that involve liquid crystals, the colors can also change with viewing angle, and the properties of the reflected or transmitted light can depend on polarization.
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From page 219... ...
Durability represents the main challenge for currency applications. Feature Motivation The committee considered the concept of a TOVD feature to be valuable owing to its easily identifiable, unique, and highly visible responsive functionality, suitable for use by the general public even with little education provided on the nature of the feature.
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From page 220... ...
Specially designed materials, especially in the case of the LCs, could provide unique colors and temperature responses. Such a device could be formed into an element, such as a security strip, and then integrated with the paper prior to printing.
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From page 221... ...
Key Technical Challenges A key challenge would be the development of low-cost, high-volume manufacturing approaches for TOVD production. The extremely high levels of reliability and durability demanded by currency applications -- including in this instance the range of ambient temperatures in which a thermal device would have to operate effectively -- represent the main difficulty.
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From page 222... ...
The key assumption is that durability of a TOVD can be achieved by suitable packaging and integration approaches. Estimate of Production Cost Compatibility with Current BEP Equipment and Processes The cost of a liquid-crystal-based TOVD is expected to be relatively high com pared with that of other nonresponsive complex features such as diffractive optical devices.
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From page 223... ...
Required Capital Equipment Capital equipment used for existing TOVDs could be implemented directly, or in some variants, for currency applications. Liquid-crystal TOVDs would most easily be integrated through a security strip or on a plastic substrate that is integrated with the paper note, similar to a diffractive optical device.
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From page 224... ...
Materials and Manufacturing Technology Options Substrate-integration technology similar to that needed to implement windows is also needed for the Fresnel lens, hybrid diffractive optically variable device, microoptic array, and subwavelength optical element features discussed earlier in this appendix. In order to produce this feature so that it is challenging to the coun terfeiter, the window would have to be integrated into the substrate.
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From page 225... ...
Key Technical Challenges The key challenge is the development of the window design and production process that are respectively durable and inexpensive. Phase I Development Plan Maturity of the Technology The window feature is a low-technology feature that could be implemented in the short term once the durability and production cost issues were resolved.
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From page 226... ...
Development Schedule The committee believes that this feature could be fully developed within 2 years. Estimate of Production Costs Compatibility with Current BEP Equipment and Processes The window feature might require an additional processing step in the produc tion at the BEP, depending on whether the holes are produced prior to printing (by the substrate manufacturer)
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