Patent Description:
Lottery scratch-off or instant games have become a time-honored method of raising revenue for state and federal governments the world over. Indeed, the concept of hiding variable indicia information under a SOC has also been applied to numerous other products such as commercial contests, telephone card account numbers, gift cards, etc. The variable indicia are the letters, numbers, images or other indicia which determine whether a ticket is a winner typically by identically matching two or more of the particular letters, numbers, images or other indicia that are part of the variable indicia under the SOC. Literally, billions of scratch-off products are printed every year where the SOCs are used to ensure that the product has not been previously used, played, or modified.

Typically the variable indicia are printed using a specialized high-speed ink jet with a water-soluble dye imaged on top of display printed (e.g., flexographic, gravure, etc.) security layers that provide opacity, chemical barriers, and a higher contrast background for the ink jet variable indicia. The purpose is to ensure that the printed variable indicia cannot be read or decoded without first removing the associated SOC, thereby ensuring that a game or product is secure against picking out winners or extracting confidential information from unsold tickets or documents.

However, there are known methods (e.g., wicking, vapor, steam, alcohol soaks, etc.) for diffusing the ink jet variable indicia either through the substrate backing or the front SOC. When carefully applied, these methods can temporally reveal the previously hidden variable indicia, thereby enabling illicit people to determine if a given ticket is a winner or non-winner while leaving little or no trace and thereby only selling losing tickets to the public. The pick-out of winning variable indicia is made possible by a positive Signal-to-Noise (S/N) ratio of the diffused ink jet image through the substrate of SOC relative to the ticket's background ink noise.

In addition to diffusion, techniques have been developed for inducing fluorescence in the ink jet variable indicia dye. In these fluorescence attacks the dye is made to fluoresce with the ticket background not emitting any light or no light in the same wavelength as the fluorescing variable indicia ink jet image. Since the variable indicia emits fluorescent light in a wavelength different from the excitation source and the ticket background, there is a relatively high S/N ratio established between the fluorescence emissions of the variable indicia and the ticket's excitation light background. This relatively high S/N ratio allows for filtered (i.e., using a narrow band optical filter only allowing fluorescent wavelength light to pass) timed exposures with digital cameras that can successfully capture variable indicia images through an intact SOC that are not discernable by the human eye. This again allows for illicit pick-out of winning tickets with only losing tickets being sold to an unsuspecting public.

Similar to the above diffusion and fluorescence techniques, electrostatic charges have also been applied to instant tickets with intact SOCs creating a differential charge in the hidden ink jet variable indicia. At this point if an electrostatically sensitive powder (e.g., baby powder) is applied over the SOC, the powder will align in the two-dimensional shape of the (previously) hidden variable indicia yet again allowing for the underlying variable indicia to be viewed over an intact SOC and allowing winning tickets to be picked-out. When the charge is removed and the powder brushed away, no indication remains that the ticket's integrity was compromised. The electrostatic attack is based on establishing a positive S/N ratio of the ink jet variable indicia's charge relative to the ticket's background ink noise.

All of these variable indicia compromise practices have been mitigated with elaborate countermeasures meticulously developed in the instant ticket industry over decades. Most of these countermeasures rely on various printed (via a fixed plate - i.e., non-variable) chemical barriers to resist the aforementioned attacks. The general concept is to secure the variable ink jet indicia image and chemistry with the chemical barrier layer(s) reducing the variable indicia's S/N ratio to near unity or below relative to the ticket's background unless the SOC has been removed. However, these added barrier security layers have the disadvantage of added costs, reduced aesthetics, intermittent failures, as well as laborious testing and verification.

Additionally, there are known techniques for mechanically "lifting" the SOC and thereby viewing the variable indicia. The term "mechanical lift" refers to a process that uses a flat blade (e.g., X-Acto chisel blade #<NUM>) or other device to peel back a portion of the SOC to reveal previously hidden variable indicia. The lifted SOC is then glued back into place such that it is not obvious that the integrity of the coating has been breached. The industry has developed countermeasures to the previously described mechanical lift technique which involve changing the formulation of the SOC so that it is more difficult to remove and/or it flakes off or crumbles, rather than peeling off in one piece, thereby making "unassisted" SOC lifts more difficult. However, these techniques have done nothing to alleviate the vexing problem of "assisted" SOC lifts. Assisted lifts differ from unassisted lifts in that another medium or material is applied to the SOC (e.g., Krylon® acrylic clear spray) to strengthen it, thereby assisting anyone who is attempting a mechanical lift.

Document <CIT> discloses a security-enhanced document having indicia provided on a substrate and a scratch-off coating layer applied over the indicia, wherein the indicia are printed as pigmented particles and one or more opacity films are provided over or under the indicia.

Document <CIT> discloses a game card that includes a confusion pattern in the form of a substantially uniform printed layer located below a primer layer and a second confusion pattern in the form of a substantially uniform printed layer located on a release coat above play indicia.

Document <CIT> discloses a scratch-off document having an information layer on a front side, wherein the information layer comprises an indicia component and a noise component, together including a plurality of pile heights.

Document <CIT> discloses improving the security of a lottery ticket by printing electronic circuits or circuit elements on the ticket by using conductive or semiconductive ink.

Document <CIT> discloses a scratch game that has a substrate, a first grid printed on the substrate, a scratchable rub-off coating applied on the first grid and a second grid printed on the rub-off coating. The first grid comprises randomly selected information, such as numbers, each printed in a separate box that forms part of the first grid. The second grid comprises selected information, such as numbers identical to the numbers of the first grid, each printed in a separate box that forms part of the second grid.

It is therefore highly desirable to develop techniques and methodologies for ensuring the security and integrity of scratch-off tickets and documents that is less reliant on chemical barrier technology attenuating the variable indicia's S/N ratio under special (i.e., predefined attack) circumstances, offering a more robust and generic defense. Ideally, these more generic defense mechanisms would also provide added security against mechanical SOC lifts, both unassisted and assisted. Particularly, these security techniques should enhance the aesthetics of the ticket or document rather than detracting from its appearance.

The present invention provides a security-enhanced document according to claim <NUM> and a method for generating a security-enhanced document according to claim <NUM>.

Objects and advantages of the invention will be set forth in part in the following description, or may be apparent from this description, or may be learned through practice of the invention.

The invention relates to a security-enhanced document with a removable SOC, which may be an instant lottery ticket in certain embodiments. The document includes any manner of suitable substrate, with the variable indicia remaining unreadable via diffusion, fluorescence, pick-off or electrostatic attacks until the associated SOC layer is legitimately removed.

In a particular embodiment, the variable indicia is imaged using the same application technique and type of ink as the display portion or area (i.e., decorative portion, not covered by the SOC) of the document providing a common printed foundation for both the display and variable indicia portions, thereby greatly reducing the variable indicia's S/N ratio relative to the ticket's display background so long as the SOC remains intact. Unlike barrier chemistry countermeasures already known in the art, this embodiment has the advantage of reducing the variable indicia's S/N ratio relative to the document's background under virtually any circumstances, rather than only for specified attacks.

In another embodiment, the variable indicia are imaged using the same application technique and type of ink as the overprint portion or area (i.e., decorative portion, printed on top of the SOC) of the document providing common printed films for both the variable indicia and the SOC itself. Again, this greatly reduces the variable indicia's S/N ratio relative to the scratch-off area so long as the SOC remains intact. This embodiment also has the advantage of providing a countermeasure against unassisted and assisted mechanical SOC lifts.

In still another embodiment, the document's backing is imaged, that is has back printing, using the same application technique and type of ink as the variable indicia, reducing the variable indicia's S/N ratio to the document's backing when viewed from the rear. Of course, the common display, overprint, and backing applications relative to the variable indicia can be combined in various manners further reducing the variable indicia's S/N ratio relative to the document's background.

In all of these embodiments, the variable indicia may be imaged on a security ink film layer (e.g., blocking layer for opacity) or imaged directly on the document's substrate (assuming sufficient opacity can be achieved by other means). The essential concept of the invention is to utilize common materials and application techniques for both the document's variable indicia and other portions (i.e., display, overprint, and/or backing areas) so that tampering can be discerned.

Described are a number of printing mechanisms and methodologies that provide practical details for reliably producing secure variable indicia under a SOC that is immune to various pick-out techniques that focus on the differences between the variable indicia and the associated background. Although the examples provided herein are primarily related to instant tickets, it is clear that the same methods are applicable to any type of document (e.g., telephone card) where information is protected by a SOC.

Reference will now be made in detail to examples of the invention, one or more embodiments of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment, may be used with another embodiment to yield still a further embodiment. It is intended that the present invention encompasses these and other modifications and variations as come within the scope of the claims.

<FIG> depicts a representative example of the variable indicia and associated security ink stack typical of a traditional ink jet SOC secured document - i.e., an instant lottery ticket <NUM>. As shown in <FIG>, the variable printed variable indicia <NUM> are between lower security ink films <NUM> and <NUM> and upper security ink films <NUM>, <NUM> and <NUM> in an attempt to provide chemical barriers protecting the variable indicia <NUM> from diffusion, fluorescence, electrostatic, and other known attacks. The entire ink film stack is deposited on a paper, foil, or other substrate <NUM>. The lower security-ink film layers include layer <NUM> providing opacity and diffusion barriers, as well as a higher contrast (e.g., white or gray against a black or other dark color) background layer <NUM>, such that a human consumer can read the variable indicia <NUM>. The upper security ink film layers also isolate the variable indicia <NUM>, first with a release coating <NUM> that helps seal the variable indicia to the substrate <NUM> and also causes any ink films printed on top of the variable indicia <NUM> to scratch-off. The SOC comprises one or more layers, and typically several, so that the variable indicia <NUM> is not visible until the ticket is played by the SOC being legitimately scratched off. The SOC layer of exemplary ticket <NUM> comprises at least one upper opacity layer <NUM> is applied to help protect against candling and fluorescence attacks. On top of the opacity layer(s), at least one white ink film <NUM> is typically applied that provides a higher contrast background for overprint inks. Finally, decorative overprint ink areas or layers <NUM> and <NUM> are applied for both an attractive appearance of the SOC area, as well as sometimes providing additional security. In addition to the security ink stack and variable indicia of areas or layers <NUM> through <NUM> of ticket <NUM>, the ticket also has printed decorative display area layers <NUM> through <NUM> designed to make the ticket <NUM> more attractive and provide instructions for game play. The printing "layers" mentioned herein may be applied in any form and in any image, and for many of the layers, not edge to edge of the ticket or other document. Thus, "layers" as used herein is equivalent to "areas" or "portions" of printed images or other indicia. Typically, this display area printing is printed via an offset or flexographic (i.e., fixed printing plate) process where the four primary printing colors Cyan <NUM>, Magenta <NUM>, Yellow <NUM>, and black <NUM> (i.e., CMYK) are blended in varying intensity to mimic all colors perceived by a human. However, other printing processes and techniques may be used if desired.

Thus, a large number of security ink film layers (seven in the example of <FIG>) are required to protect and allow for only legitimate consumer readability of the variable indicia <NUM> of a traditional SOC protected document, such as an instant lottery ticket. Of course, the example of <FIG> is just one possible arrangement of a traditional SOC protected document with security ink films, with the goal of any security ink film coating arrangement being to provide barriers to outside attempts to detect the variable indicia without properly removing the SOC.

These security ink film barriers have been highly evolved to provide security countermeasures against various diffusion, fluorescence, electrostatic, and other attacks as they became known to the industry. Thus, the barriers are highly tuned to known attacks and not necessarily helpful against new attacks that utilize previously unknown agents or excitation wavelengths. The industry typically modifies these highly tuned and complex security barriers only when a new attack becomes known.

For example, <FIG> illustrates a diffusion attack on an instant ticket <NUM> where a solvent <NUM> that was selected to attack the chemistry of the ink jet variable indicia <NUM>, such that when the solvent <NUM> is gently applied by an eye dropper <NUM>, the solvent <NUM> penetrates through the decorative overprints <NUM> and <NUM>, the white ink film <NUM>, the upper opacity layer <NUM>, and the release coat <NUM> without disturbing their chemical bond to the ticket <NUM>, the ink stack (<NUM> through <NUM>), or the substrate <NUM>, thereby allowing those layers to appear intact and undisturbed. If the solvent <NUM> is properly selected it will saturate an area <NUM> of the variable indicia <NUM> and cause a small portion of the variable indicia to diffuse through the upper security layers and the overprints (<NUM> thru <NUM>) to reveal a faint ghost image <NUM> of the underlying variable indicia <NUM>. As is typical of these types of attacks, once the ticket <NUM> is allowed to dry, the ghost image <NUM> disappears leaving virtually no trace that the ticket <NUM> was compromised for pick-out of the variable indicia <NUM> via diffusion. This same type of diffusion attack can also be applied to traditional lottery tickets via the back of the substrate <NUM>.

This type of attack relies on the ink jet variable indicia <NUM> of a traditional lottery ticket <NUM> being of a separate chemical composition than the upper security ink layers (<NUM> through <NUM>), the lower security ink layers (<NUM> and <NUM>), and the display area print (<NUM> through <NUM>). This works because traditional lottery tickets typically employ an ink jet dye for printing the variable indicia <NUM> that is of a chemistry that is substantially different than the security ink layers (<NUM> through <NUM> and <NUM> through <NUM>), overprint areas <NUM> and109, and display areas <NUM> through <NUM>. This is because the variable indicia <NUM> are variable from ticket to ticket and the high volumes of scratch-off documents produced in a typical print run require the variable indicia to be printed at high speeds (e.g., <NUM> to <NUM> metres per minute - m/min (<NUM> to <NUM>,<NUM> Feet Per Minute - FPM)) and at as low a cost as possible to be economically feasible. When these considerations are combined with the variable indicia <NUM> and associated barcode and inventory control number (not shown) being the only variable data printed on a ticket <NUM>, it becomes the accepted state of the art to utilize different chemistry (e.g., water based dye) for the ink jet than the rest of the ticket <NUM>.

Known diffusion attacks (e.g., alcohol) have been mitigated by attempting to make the security barriers impervious to solvents <NUM> of the ink jet variable indicia <NUM>. The release coat <NUM> in particular has become of increasingly exotic nature both in terms of chemistry and application. The current state-of-the-art is to cure the release coat with an electron beam in a controlled atmosphere. However, the possibility always remains that a new solvent may be discovered that penetrates these coatings and thereby defeats the existing countermeasures. Alternatively, diffusion attacks may also be attempted in the opposite direction (i.e., through the back of the substrate <NUM> and the lower security coatings <NUM> and <NUM>) where the barrier seals may not be as sophisticated due to the high graphic adhesion requirements of the lower security coatings. The significant point is that so long as the materials and application of the ink jet variable indicia <NUM> remains different than the security ink layers <NUM> through <NUM> and <NUM> through <NUM>, the overprint areas <NUM> and <NUM>, and the display areas <NUM> through113 the possibility always remains to achieve a S/N ratio sufficient to discern the variable indicia <NUM> via a ghost image <NUM> without removing the SOC.

The same concept of differing materials and applications for the variable indicia relative to the rest of the document enabling security attacks without removing the SOC can be applied to fluorescence and electrostatic attacks. In the special case of electrostatic attacks, the differential charge in the hidden variable indicia generally can be neutralized using anti-static barriers typically comprising a conducting polymer (plastic) and a solvent made from deionized water and alcohol. When printing, the solvent evaporates, leaving behind an invisibly thin conducting film on the surface of the printed image that shields differential charge build-up, thereby providing a shield against all types of electrostatic attacks. However, since the variable indicia is applied by a different technique and uses different ink than the rest of the document, the possibility still remains that some charge differential may be utilized in the future using an unknown technique (e.g., higher voltage, differing polarity, etc.) that allows for the variable indicia to be read without removal of the SOC.

Fluorescence attacks are another matter; the large numbers of potential excitation wavelengths that may induce fluorescence in differing wavelength(s) are literally in the hundreds of thousands. Also, the long molecular chains of Volatile Organic Compound (VOC) dyes (typical of ink jet dye) tend to be susceptible to fluorescence over multiple excitation wavelengths. What is more, subtle variation in the chemistry of the ink used for the variable indicia may greatly alter its fluorescence characteristics, inadvertently causing emissions to occur with excitation wavelengths and fluorescence emission wavelengths previously thought to be secure. Given that the bandwidth of possible excitation and emission wavelengths is so large and the nature of fluorescence attacks allow for timed exposures over a narrow (i.e., fluorescence emission) bandwidth, it is extremely difficult to engineer reliable opacity blocking layers sufficient to ensure security over a large press run. The underlying problem is that timed exposures over a filtered narrow band centered about the fluorescence emission wavelength of the variable indicia allows for extremely small emissions of photons from the variable indicia fluorescence transmitted through the upper security layers to be collected over time, thereby allowing for a sufficient S/N ratio to identify the variable indicia of a document with the SOC intact.

For example, <FIG> illustrates one possible method to induce sufficient fluorescence in the variable indicia <NUM> of a traditional document or ticket <NUM> secured under SOC security layers <NUM> through <NUM> and the overprint layers <NUM> and <NUM> to ascertain the variable indicia information without damaging the SOC. In <FIG>, an excitation light source <NUM> generates excitation photons of a desired wavelength <NUM> (e.g., λ = <NUM> - blue light) of sufficient quantity and intensity to penetrate, albeit with attenuated photons <NUM>', the upper blocking SOC security layers <NUM> through <NUM>) and overprint areas <NUM> and <NUM>, thereby inducing fluorescence <NUM> in the traditional ink jet dye-based variable indicia <NUM>. Since the induced ink jet variable indicia fluorescence <NUM> is of a different and longer wavelength (e.g., λ > <NUM> - Infrared (IR) light), the lesser number of fluorescence photons <NUM>' that penetrate through the SOC security layers <NUM> through <NUM> and overprint areas <NUM> and <NUM> to radiate from the ticket or document's surface provide a large enough S/N ratio sufficient to produce an image <NUM> of the previously hidden variable indicia <NUM>, using a timed exposure camera where an optical filter <NUM> blocks the reflected excitation light source <NUM>", only allowing the longer wavelength fluorescent light <NUM>" to pass.

All of these previous types of attacks (i.e., diffusion, electrostatic, and fluorescence) exploit the different types or chemistries of ink and application techniques of the variable indicia <NUM> (typically ink jet dye) relative to the rest of the type or types of ink used (typically fixed plate applied ink) in the document or lottery ticket <NUM> to obtain sufficient S/N to ascertain the variable indicia without removing the SOC. However, any differences between the application and materials of the variable indicia and the display areas or overprint areas of a document or ticket are completely eliminated with the invention of utilizing the same variable digital imager and ink to print both the variable indicia and the overprint areas or the display areas, or all of the variable indicia and the overprint areas and the display areas. Imaging the SOC overprints and possibly the ticket back with identical imager techniques or materials can further enhance this commonality. Thus, by utilizing common, (also called homogenous) applications and materials over the entire document or ticket as well as the variable indicia eliminates any attempt to garner a positive S/N ratio of the variable indicia ink relative to the rest of the document's background ink noise by exploiting unique physical characteristics of the variable indicia.

<FIG> provides a preferred embodiment of an exploded top isometric view of a modified document with secure variable indicia according to the present invention, in the form of an exemplary lottery-type instant ticket <NUM>. The ticket includes a substrate <NUM> having lower security ink film stack layers <NUM> and <NUM> below the printed layer <NUM> with the variable indicia <NUM>' and the overprint areas <NUM> through <NUM> utilizing variable indicia homogenized with the ticket display areas and overprint areas. The embodiment of <FIG> illustrates the variable indicia <NUM>' and ticket display <NUM>" are printed as part of the same homogenous digital imager application on printed layer <NUM> on the lottery-type instant ticket <NUM>. For the purposes of this embodiment, the type of digital imager ink or material (e.g., toner based, thermal transfer, pigmented ink jet, dye based ink jet, etc.) and the method or technique of applying the homogenous variable indicia and display film layer <NUM> to the ticket <NUM> is irrelevant; the significant concept is that the variable indicia <NUM>' and display area <NUM>" are to be applied with the same application utilizing the same printing inks or dyes, whatever they are. Since the resulting homogenous film <NUM> covers both the variable indicia and the display area there can no longer be any positive S/N ratio derived from differences between the variable indicia <NUM>' and the display area <NUM>". Therefore, the underlying concept of diffusion, electrostatics, and fluorescence exploiting a positive S/N ratio of the variable indicia ink relative to the ticket background ink noise is no longer applicable. In other words, any attempt to extract any unique characteristic of the variable indicia will also extract the same characteristic from the display area noise with no positive S/N possible. This reduction of variable indicia <NUM>' signal relative to the ticket <NUM> background noise can be further enhanced by imaging the overprint area <NUM> with the same digital imaging process that was used to generate the variable indicia <NUM>' and the display area <NUM>" into a homogenized film layer <NUM>.

As its name implies, the overprint <NUM> is printed after the variable indicia on top of SOC layers <NUM>, <NUM>, and <NUM> and therefore cannot be imaged at the same time as the variable indicia <NUM>'. However, by digitally imaging the display <NUM> with the same process and materials as the variable indicia <NUM>', the same effect of eliminating any variable indicia signal to the remainder of the ticket <NUM> ink noise is achieved especially for attacks (e.g., fluorescence) that attempt to penetrate the SOC.

In an alternative embodiment, the display area <NUM>" can be imaged with the same application as the overprint area <NUM>, providing a homogeneous film encompassing the overprint area <NUM> and the display area <NUM>" with the variable indicia <NUM>' being imaged with the same process and materials, thereby ensuring no significant variable indicia <NUM>' signal relative to the background noise of the ticket's display <NUM> area" and the overprint area <NUM>. In certain applications this alternative embodiment may be preferred where it is desirable to ensure that the overprint area <NUM> graphics and display area <NUM>" seamlessly blend together and may therefore provide a countermeasure to unassisted and assisted SOC lifting techniques where the SOC is temporally "lifted" by mechanical means, which allow for the underlying variable indicia to be observed, and then the SOC rolled back into position with an adhesive, thereby making the ticket appear uncompromised. This alternative embodiment would provide a countermeasure to these unassisted and assisted SOC mechanical lift attacks by eliminating any clear demarcation between the overprint area <NUM> and display area <NUM>" with any mechanical lift attempt disrupting the homogenous overprint area <NUM> and display area <NUM>". This disruption in image effect can be enhanced by including fine lines and/or other micro-printing around the boundary between the overprint area <NUM> and display area <NUM>".

Returning to the homogeneous unified film variable indicia <NUM>' and display area <NUM>" embodiment of <FIG>, as shown in the figure, the configuration of the remaining ink security stack protecting the variable indicia <NUM>' can remain essentially the same as in the existing ticket <NUM> described in <FIG>. With the ticket <NUM> of <FIG>, the entire ink film stack is deposited on a paper, foil, or other substrate <NUM> and the lower security-ink film opacity layers <NUM> and a higher contrast (e.g., white or gray) background layer <NUM> such that a human consumer can read the variable indicia <NUM>' are used. The upper security ink film layers also isolate the variable indicia <NUM>', first with a release coating <NUM> that helps seal the variable indicia to the substrate and also causes any ink films printed on top of it to scratch-off. Next, at least one upper opacity layer <NUM> is applied to help protect against candling and fluorescence attacks. On top of the opacity layer(s), at least one white ink film <NUM> is typically applied that provides a higher contrast background for overprint inks with the overprint area <NUM> imaged both as an attractive appearance of the SOC area as well as possibly providing additional security.

As illustrated in the embodiment of ticket <NUM> shown in <FIG>, the lower security opacity layer <NUM> and higher contrast background layer <NUM>, either or both included within the back or bottom printed portion are not confined just to the variable indicia area <NUM>, but rather flood the entire ticket <NUM> substrate <NUM> from edge to edge. This flooding of the entire ticket <NUM> substrate <NUM> area allows for generic lower security printing plates or cylinders for any type of ticket design to be maintained from print run to print run. Thus, there would be no need to change the fixed printing plates or cylinders (e.g., flexographic, gravure, etc.) between printing different games. As is practiced in the existing art, these lower security areas are always customized to only cover the general variable indicia scratch-off area <NUM>' and not to flood the entire ticket - see lower security layers <NUM> and <NUM> of ticket <NUM> of <FIG>. This is primarily because the higher contrast background layer(s) <NUM> are not sufficiently opaque to provide a completely neutral (i.e., white) background over the black opacity layer <NUM>. Additionally, it is sometimes argued that the cost of inks for the lower security areas can be reduced by confining the lower security ink coverage to only the variable indicia scratch-off area(s).

The embodiment of ticket <NUM> of <FIG> overcomes the neutral background limitation by simply applying at least one thicker or denser or thicker and denser higher contrast background <NUM> layer to the substrate. This thicker and/or denser ink film deposit higher contrast background layer <NUM> becomes possible once it is realized that a generic flood coverage of the ticket <NUM> surface allows for more ink <NUM> to be applied to the substrate <NUM> than would normally be possible, since there is no longer any requirement to print lines or hold registration to a predefined demarcated area. Thus, for flexographic applications, the lower security ink films can be applied via anilox rollers with very low line screens and high Billion Cubic Microns (BCM) capacity, the only limiting factor being the ability to cure the ink film at press speeds. Additionally, since it is envisioned that the lower security ink film layers <NUM> and <NUM> of ticket <NUM> are not changed between print runs, it may become economically feasible to use printing technologies with a high cost of printing cylinder creation, but also a high potential capacity to deposit thick and/or dense ink films - e.g., gravure. The higher costs of ink coverage as well as the higher costs of printing cylinder production are more than compensated for by the reduced time and expense associated with reconfiguring a press from one print run to the next.

In another alternative embodiment, the upper blocking layer(s) <NUM> and white film layer(s) <NUM> could be configured for flood coverage similar to the lower security layers <NUM> and <NUM> of ticket <NUM> with even more reduction in press setup costs. However, the release layer <NUM> in all embodiments would be confined to the variable indicia scratch-off area <NUM>' to ensure that only the desired SOC areas of the ticket <NUM> scratch-off.

In addition to flood coverage, in yet another embodiment it may be possible to eliminate the lower security layers <NUM> and <NUM> entirely. In this embodiment, the nature of digital full-color imaging utilized for the variable indicia <NUM>' offers the potential to eliminate lower security layers <NUM> and <NUM>, since the imaged variable indicia <NUM>' is deposited as a continuous film <NUM>, preferably as part of the ticket display area <NUM>" and therefore, has a lower S/N ratio, since no special materials are utilized for the variable indicia.

In still another embodiment, the security layers of the ticket <NUM> may be applied via a digital imager. In this embodiment, the opacity layers <NUM> and <NUM> and white high contrast overprint areas or layers <NUM> and <NUM> would be ink jet imaged in the shape of the variable indicia scratch-off area, preferably with an Ultraviolet (UV) curing system. The UV curing system is preferred because direct energy curing typically leaves a thicker, more robust ink film deposit on the substrate utilizing direct energy curing, rather than convection curing.

When the homogenized embodiments of the ticket <NUM> of <FIG> and its alternatives are subjected to diffusion attack, no appreciable S/N ratio of the ticket variable indicia <NUM>' relative to the ticket background ink noise can be discerned. For example, <FIG> depicts the ticket <NUM> under a diffusion attack similar to <FIG>, where the eyedropper <NUM>' applies solvent <NUM>' selected to attack the ink of the variable indicia <NUM>'. However, in <FIG>, the area <NUM>' where the solvent <NUM>' is applied simultaneously attacks both the overprint area <NUM>, as well as the variable indicia <NUM>', resulting in a combined surface area <NUM>' that dissolves and combines both the overprint area <NUM> and variable indicia <NUM>'. This results in a blurred image that does not carry a sufficient S/N ratio of the variable indicia ink relative to the overprint area ink to discern the variable indicia. Additionally, by having the surface display area <NUM> printed in the same application and materials as the variable indicia <NUM>' any solvent sufficiently powerful to draw the variable indicia through the upper security layers <NUM>, <NUM>, and <NUM> would also irrevocably alter the display area <NUM>, such that the tampering by diffusion would be readily apparent and the ticket could no longer be sold as pristine.

The same principle applies when the homogenized embodiments of the ticket <NUM> of <FIG> are subjected to a fluorescence attack - i.e., no appreciable S/N ratio of the ticket variable indicia <NUM>' relative to the ticket background can be discerned. For example, <FIG> depicts the ticket <NUM> under a fluorescence attack similar to <FIG> where an excitation light source <NUM> attempts to project sufficient photons of the correct excitation wavelength <NUM> to induce fluorescence photons <NUM> in the variable indicia <NUM>' and after attenuation, photons <NUM> through the upper security layers and display area of the ink stack (<NUM>, <NUM>, <NUM>, and <NUM>). However, in <FIG> the fluorescence <NUM>"/<NUM>' from the overprint area <NUM> and the display <NUM>" completely saturate any fluorescence induced photons from the variable indicia <NUM>, resulting in a time exposure image that does not carry a sufficient S/N ratio of the variable indicia relative to the overprint area and/or the display area noise to discern the variable indicia. Again, the common shared application and materials of the variable indicia <NUM>' with the display area <NUM>" and the overprint area <NUM> results in a homogenous ticket <NUM> where the variable indicia cannot be picked-out due to insufficient S/N ratio.

In many, if not most instances in this invention, the homogenous integration of ink used in the variable indicia with the other printed portions of the document will be the identical ink, so that the S/N ratio of the ink used for the variable indicia will be the same as the background ink noise of the other printed portions. Typically, such inks may be any of a dye based ink, a pigment based ink or inks having other bases. Also in this invention, the inks of the variable indicia and the other portions can be applied using the same printing technique, such as ink jet printing, thermal transfer or xerography, for instance, for the same reason. However, it is important to understand that the identical ink chemistry need not be used and the identical printing technique need not be used for the variable indicia and the other printed portions of the document. Rather, what is important is that the inks and printing techniques used result in the variable indicia having a S/N ratio relative to the background ink noise of the document's at least one other printed portion, such that the variable indicia are unreadable with reference to the at least one other printed portion when the SOC remains intact. The S/N ratio need not be exactly zero, so long as the variable indicia cannot be read or otherwise discerned in view of or with reference to the background noise of at least one other printed portion of the document when the SOC is intact.

The invention also includes any method or system for making a secure document as described above. Thus, the method broadly comprises printing the variable indicia comprising ink having a S/N ratio relative to the background ink noise of the document's at least one other printed portion, such that the variable indicia are unreadable with reference to the at least one other printed portion when the scratch-off-coating remains intact.

Various types of printing presses and combinations of printing presses are available to make the secure document of the invention and according to the method of the invention.

<FIG> illustrates one embodiment of a printing press <NUM> capable of producing tickets <NUM> with homogenous integration of the variable indicia <NUM>', the display area <NUM>", the overprint area <NUM>, and/or the ticket back printing area (not shown). As shown in the embodiment of <FIG>, paper is fed into the press on a spool <NUM> to a seven-color digital imaging unit <NUM>. The seven-color unit <NUM> images a Lower Blocking Black (LBB) ink film layer <NUM> and two white high contrast overprint ink film layers <NUM> in the shape of the variable indicia scratch-off area, preferably with an UV based curing system. After the lower security LBB ink film layer <NUM> and the white high contrast ink film layers <NUM> are applied, a four-color process digital image is applied to image both the ticket variable indicia <NUM>' and display area <NUM>". Thus, the printed ticket will have a homogenized variable indicia <NUM>' and display area <NUM>". After printing the front variable indicia <NUM>' and display area <NUM>", the substrate <NUM> is flipped and the ticket back is imaged as a four-color process by a unit <NUM> with application and materials identical to that applied by the unit <NUM>. After the ticket back is printed, the substrate is flipped again and a release coat <NUM> is flexographic printed at a station <NUM> over the variable indicia <NUM>' to provide protection for the variable indicia as well as to ensure that any subsequent ink films deposited on the release coat <NUM> will scratch-off. Ideally, the release coat <NUM> is also direct energy cured with either UV or an electron beam. After the release coat is applied, a second seven-color unit <NUM> images an Upper Blocking Black (UBB) ink film layer <NUM> and two white high contrast overprint ink film layers <NUM> in the shape of the variable indicia scratch-off area preferably with an UV curing system. After the upper security UBB ink film layer <NUM> and white high contrast <NUM> ink film layers are applied, a four-color process digital image is applied to image the overprint area(s) <NUM>. Once the upper security layers <NUM> and <NUM> and overprint area <NUM> have been imaged, periodic perforations are stamped into the substrate by a unit <NUM> to allow strips of tickets to be packaged and torn off individually at the time of sale. The resulting fully imaged and perforated substrate is then collected via a take-up reel or fan-folder <NUM>. The embodiment of <FIG> has the advantage of rapid and low cost setups between press runs with the flexographic plate of the release coat at the station <NUM> being the only station that requires manual intervention.

Claim 1:
A security-enhanced document (<NUM>) comprising:
a substrate (<NUM>);
a lower security opacity layer (<NUM>) printed on the entire substrate (<NUM>);
a higher contrast background layer (<NUM>) printed on the entire lower security opacity layer (<NUM>);
variable indicia (<NUM>') comprising ink, the ink of the variable indicia being of a specific type and applied to the higher contrast background layer (<NUM>) using a specific application technique, the ink of the variable indicia causing a variable indicia signal (<NUM>) when measured;
a scratch-off-coating layer (<NUM>, <NUM>, <NUM>) applied over the variable indicia to maintain the variable indicia unreadable until the scratch-off-coating is removed by being scratched off; and
an other printed portion (<NUM>", <NUM>) causing a background noise signal (<NUM>", <NUM>) when measured, the other printed portion being printed using the same type of ink and the same application technique as the ink of the variable indicia, wherein the other printed portion comprises an overprint area comprising an area on top of the scratch-off-coating, and
wherein the ink of the variable indicia and the other printed portion being the same type of ink applied using the same application technique results in a ratio between the variable indicia signal and the background noise signal that is not appreciable,
wherein the other printed portion further comprises a display area (<NUM>") not covered by the scratch-off coating, printed on the higher contrast background layer (<NUM>), applied with the same application utilizing the same printing inks or dyes as the variable indicia (<NUM>'), thereby resulting in a homogeneous film (<NUM>).