While it is often said that the cornerstone of security print is intaglio, in this Technology Profile we  look at a very different print technique, digital print, which is generally viewed as a threat by traditional security printers, but which nevertheless offers considerable opportunities for suppliers and issuers alike - not only in the context of adding variable data for unique product identification purposes, but as a means of generating security features as well.

According to HP, 'digital printing is any printing technology that is capable of producing printed materials directly from a computer file'. Digital printing eliminates the mechanical steps used in conventional printing and does not require an intermediary medium such as film, or an intermediary machine, such as a plate maker. Non-impact printing such as laser, ink-jet and dye sublimation all fall into this category, as do ink-less technologies such as laser engraving and thermal imaging. Digital printers range from stand-alone and in-line coding and numbering systems through home and office equipment to large format multi-colour presses.

In terms of opportunities for security print, digital pre-press techniques are revolutionising the speed with which designs can be originated. Added to this, a new generation of software-generated security features is now being offered by prepress and digital giants that work on the basis that digital printers can make any print element unique - a particular attraction of such features being that they can be added in-line with minimal on-cost and no changes to existing processes.

Security and Traceability

Following on from this, and perhaps most importantly for product protection purposes, digital printing, as a print-on-demand technology, is ideally suited for personalisation (whether in the form of unique data or sequential serialisation) at any point during the production or distribution chain, thus offering the opportunity for value documents and goods to combine security with traceability. 

In terms of threats, however, the same technology - thanks to falling prices and advances in quality and capabilities - is lowering the bar to counterfeiting, and making the tools for the production of fake documents, packaging and labels available to a much wider pool of potential counterfeiters. In other words, counterfeiting is moving beyond the traditional, skilled criminals and is now within the reach of the everyday opportunists - presenting an explosion in fakes.

Hence the cynicism in some quarters to digital print as a bona fide tool in the creation of security documents and labels, which is based on the use of specialty secure paper stock and inks, coatings, complex and elaborate graphics and, most importantly, restricted print systems (intaglio and, to a lesser extent, offset) based on static printing plates.

Digital print technology is, by contrast, anything but scarce. It is ubiquitous and, even putting aside the proliferation of personal printers, the cost of industrial-sized digital printers is considerably less than that of other printing systems.

Limiting Factors

And there are other factors that limit its suitability for security print. Although the digital printers of today have come a long way from the black and white Docutech systems of old and are now widely used in commercial print, they still far from offering the speed, quality, resolution and colour fidelity that are so essential in the creation of security documents.

But digital print technology does, nevertheless, have certain advantages that make it a useful accessory. One is in the speed of origination and set-up, which is a fraction of that of traditional techniques (and indeed, the digital revolution is already playing its part in the pre-press phases of intaglio and offset production).

And, just as the security provided by the latter two rests on, among other factors, the ability to generate special effects through the manipulation of line structure, perfect registration and the combination of inks, so too can digital print be used to generate unique features both through the underlying software on its own and in conjunction with the inks and toners.

Flexibility is Key

Most importantly of all, however, is its flexibility - specifically in terms of its ability to individualise documents and labels with unique or sequential data. This has had a tremendous impact on the market for ID documents, where the ability to create different levels of corresponding biodata on each item is critical.

But it is also important for other sectors that require both security and serialisation. In addition to applying unique codes or features, when used in conjunction with the appropriate data capture and encryption technology, it can also be used to generate the codes in the first place and provide information within these relating to such key information as manufacturer, date, production facility and so on.

It is these characteristics of digital print - in particular the print-on-demand element, personalisation and its non-impact nature - that are complementary to the security generated by more traditional means.

Threefold Applications

The ways in which digital print brings added security to the printing process are essentially threefold. First is in origination. Second is in personalisation - both in the application and the generation of data. And third is the combination of software-generated features in combination with security features within the toners and inks. And some of the major player in digital print and security are involved in some, if not all, of these.

Regarding origination, security printers have long used customized high end design systems for the generation of features such as guilloches and vignettes on high security documents. But software programs are now available to create security patterns and images for more everyday items with a security requirement - including packaging and labels.

Agfa, for example, offers security software for these markets through its Apogee Secuseal 2.0. A successor to Secuseal 1.0, launched in 2007, this is a set of plug-ins for Adobe Illustrator^TM and is applicable to all standard design workflows, allowing designers to add security elements to any printed design. The plug-in modules, of which there are four, can create complex backgrounds or convert images into linework patterns which can be embedded directly into the printed design.

Software-Generated Features

Taking this a step further, Xerox offers a suite of printing solutions under the generic name of FreeFlow^TM. These specialty imaging text effects can only be printed with a FreeFlow digital front-end in combination with FreeFlow software - any other print server will print them as normal text. FreeFlow can deliver printed documents with microtext (down to 1 point in size), correlation marks that require a transparent decoder, Glossmark - a type of latent image visible only when the glossy surface is tilted, and UV or IR features that are created from a special combination of toners used in xerographic printers. Prints from a four-colour printer selectively expose the fluorescent properties found within white paper, making it possible to embed personalised printing, hidden marks or codes that show up under UV light.

Alternatively, the infrared-absorbing properties of the black element of toners can be used to create text that is masked by the other colours in the toner in ordinary light, but exposed under IR light. In both cases, it is not the inks themselves that have been modified to create these effects, but the digital imaging software.

Another development from Xerox- which falls within the realm of code generation as opposed to just application - is DataGlyph, comprising encoded machine readable data. Information is encoded into thousands of tiny, individual glyph elements, each consisting of a small 45° diagonal line, as short as 1/100th of an inch or less, depending on the resolution of the printing and scanning that is used. Each one represents a single binary 0 or 1, depending on whether it slopes to the left or right. Sequences of these can be used to encode numeric, textual or other information.

The individual glyphs are grouped together on the page, where they form unobtrusive, evenly textured gray areas, like half-toned pictures. The information to be put in the DataGlyphs is encoded as a sequence of individual glyphs, and these can be printed either directly by the encoding software (for instance, by computer laser printer) or via a conventional printing process, such as offset.

Unique Coding Technologies

This use of digital print technology to not only apply variable information, but to generate the codes in the first place in the first place, is evident in the offerings of many companies involved in this arena. Another example comes from Atlantic Zeiser, specialists in numbering systems for high security documents such as banknotes, tax stamps and ID documents.

The company's numbering technology was originally based on boxes for letterpress printing. In the early 1990s, it began introducing high speed inkjet numbering complete with camera verification systems which, with a run rate of 300 m per minute, were revolutionary at the time. Today, the company offers solutions that can print on a number of different substrates (unlike many other digital print systems), with a resolution of 600 dpi. It also develops its own speciality security inks for digital print.

In addition to providing high quality, high speed numbering technology, the company has moved into the development of digital security technologies. One product of this move is ProDNA - whereby the microstructure of the substrate (eg paper) is captured and converted into a code which is then stored on a database. The document can be read with a scanner, and the code verified against that stored in the database. Alternatively, if the code is converted to a 2D code and printed back onto the item, then - equipped with the correct scanner and software - the user can match without checking with the database, providing a digital form of 'self-verification'.

Another company utilizing the concept of taking a characteristic of the document or label to create a code is German press giant Heidelberg, with Linoprotect. Unlike Atlantic Zeiser's solution (known as fingerprinting because it uses features inherent to the substrate), the feature is added in the form of ultra-thin copper or metal threads that are recombined to generate a random pattern which is then applied to the packaging or document as a label. This pattern is analysed by the Linoprotect reading module, a special camera system, and a cryptographic key that is unique to each customer converts the pattern into an equally unique datamatrix code. This code is printed onto the packaging or document next to the label with its pattern of copper threads using a digital Linoprint drop-on-demand inkjet system.

From the user's point of view, the authenticity of the product can be checked using just a mobile phone camera or a scanner and special software that is freely available. The software compares the two Linoprotect security features on the product or packaging and immediately identifies whether or not the content of the data matrix code matches the pattern in the adjacent field.

Security via Print Media

And then there are the techniques for incorporating security features into toners, dyes or other print media. Print giant Xeikon, for example, offers a toner that lights up when exposed to UV light. In addition, the fifth colour station of the Xeikon 3300 press can be used for spot colors, as well as 'one-hit' opaque white and special security toners.

Dynic Corporation has incorporated microscopic markers into thermal transfer ribbon (TTR). This provides an additional layer of authentication to digitally printed indicia such as serialized alphanumeric codes or increasingly popular 2D barcodes. Many markers or taggants are not suitable for digital print because the particle size is too large. But not these taggants, which are the result of active involvement with ARmark, a US specialist in document protection. Its taggants have been successfully incorporated into paper, inks, and varnishes.

Another example is the Océ Jetstream, which can deliver six, fully variable security features on cheques. These print systems feature high-speed, four-color inkjet printing with magnetic ink character recognition (MICR) capability. They are used in applications such as direct marketing brochures, balance transfer programs, refund checks, reward certificates and coupons.

And another is Troy Group which, as a Gold Solutions Partner to HP, is the only company in the world authorized to enhance HP printers and consumables for use in secure printing workflows. Its speciality is the supply of toners for digital security print. Its MICR Toner Secure contains a hidden red security agent within the toner; chemical alteration causes red stain to appear. Any solvent that will remove the toner will release the active red agent which is embedded in the toner.

Most recently, Nipson, specialists in magnetography, have launched a fluorescent toner for their DIGIFlex and VaryPRESS presses that is designed to facilitate fraud prevention and detection. Kodak has also introduced fluorescence to a virtually invisible clear ink for its NEXPRESS digital colour presses that can be used to print barcodes and unobtrusive images that are read with special barcode readers. The ink is, says the company, designed to allow digital print service providers to enter the lucrative and growing secure document and track & trace markets.

While these examples refer, in the main, to companies that are applying their skills in digital print to the security arena, there are also many examples of security vendors harnessing digital technology themselves for niche applications. All point to the fact that many companies, large and small, have made significant investments in exploiting the opportunities offered by digital printing to raise security printing to new levels.