Applications for print security

Whatever quantity of a product is produced, it will be necessary in the majority of cases to mark the merchandise in a way that provides recognition of its manufacturer, a list of ingredients or content, the volume, quantity or weight, health or safety requirements, nutritional information and provide suggestions as to how best to use, consume or handle the goods.

Most consumer-related labels and packaging will also be required to carry a barcode . or even barcodes . and to meet all the relevant labeling regulations that often differ from country to country.     

Obviously the requirement for small quantities of labels and packaging will require different treatment to those that call for millions or even billions of containers or decals.

Furthermore, the constraints provided by the physical characteristics of the product will have an effect on the containers used.

Liquids will require bottles in PET or glass; powders or many food and DIY goods will demand flexible packaging or cartons and compacted goods and components will call for direct labeling as well as secondary packaging materials. In many cases the product may be in a bottle or tray, inside a carton or carton sleeve, and also contain a leaflet or usage instructions in the pack . all needing to match with the same bar code or security-related information.

In the pharmaceutical market there will be a requirement for blister packs, while for the protection and display of hardware, tools, batteries, cabling, etc., it will be essential to supply such items in clam shells.

These wide variations in labeling and packaging requirements from industry to industry are by no means meant to be exhaustive. They are provided as an indication of the wide envelope of services and solutions now available to brand owners world-wide. As packaging and labeling become more intelligent in future, this complexity is only liable to broaden even further.

During the last couple of decades printing processes have advanced enormously. We now have many new processes such as digital electro-photographic printing using both liquid and dry toner, both solvent and water-based inkjet and lasers for direct product marking that supply our growing need for personalization, low print runs and systems that can mark three dimensional products using inkless technology.

At this point it may be apposite to take stock of the industry and the traditional print processes available, together with a brief look at how some of the latest technology can be integrated and drawn into a seamless process that can deliver labels and packaging that addresses all of the complex security requirements of the modern brand owner. It should also be mentioned that in some added-value printing sectors, such as self-adhesive label printing, that combinations of printing processes may be used in the same machine to create a production line that encompasses, say, screen process, offset litho, hot-foil printing and UV flexo varnish.

Combination process printing such as this may also help to deter counterfeiters because of the high cost of press investment and the skill required to operate such equipment and integrate the various operations necessary to meet brand owner demand.

LITHOGRAPHY

Also known as offset printing, lithography is a process widely used for printing glue applied labels and also for the production of cartons and swing tags. Originally a sheet fed process it now encompasses reel fed (continuous web feed) for the production of labels on the roll and for in-mold labeling and also for printing metal sheets for later conversion into closures, boxes and lidded tin containers.

The printing plates are wrapped around a plate cylinder which delivers the inked impression to a rubber blanket roller and this is offset onto the surface of the material being printed, thus the reference to ‘offset’. Fine lines and excellent screen quality conspire to provide a superior image and offset-litho machines can carry a number of colors which can be duplexed on suitable machinery if close face and reverse register is required.   

Plate making is relatively simple. Thin sheets of light sensitive aluminum plate are exposed through an original film which is created from a computer imaging origination process. The printed image is separated from the non-print area through the clever use of ink (oil based) and water. The image to be printed obtains ink from ink rollers, while the non-printing area attracts a water-based film (called a ‘fountain solution’), keeping the non-printing areas ink-free.

Advantages of offset litho printing (for security applications)

The process delivers a consistently high image quality which can carry both fine line-work (which is an important tool for deterring replication and copy attacks) and covert HIT images within the structure of background screens.

Many wine and spirit labels are printed using this method as are health and beauty aids and personal care labels and packs.

Offset printing produces sharp and clean images and type more easily than letterpress printing because the rubber (offset) blanket conforms to the texture of the printing surface. The production of printing plates is a relatively quick and easy process especially if computer to plate technology is installed.

Properly developed plates running in conjunction with optimized inks and fountain solution may exceed run lengths of a million impressions and since each impression will deliver a high number of individual label or carton pieces it is possible to produce high quantities of quality product relatively cheaply.

Disadvantages of offset printing (for security applications) when compared to other printing methods include:

Because only a thin film of ink is applied during the process there is a slightly inferior image quality compared to that of gravure printing.

There is said to be a propensity for anodized aluminum printing plates to become sensitive (due to chemical oxidation) and print in non-image/background areas when developed plates are not cared for properly.

The time and cost associated with producing plates and printing press setup makes smaller quantity printing jobs largely impractical. As a result, smaller printing jobs are now moving to digital offset machines.

LETTERPRESS

Modern letterpress printing uses photo-sensitive polymer plates on which a raised image (ink) carrying area is carried. Plates are produced by photographic and direct image platemaking techniques.

Polymer plates are flexible and can be used in flatbed short run machinery (sheets) or longer run web fed rotary presses where each cylinder print unit applies a different color to the web material. It is also necessary to dry the ink on faster running machinery with the assistance of ultra-violet light curing systems to prevent ink set-off and to ensure each color is cured before the next is laid down.

Letterpress printing is still relatively common in older roll-label presses, but with UV flexo mainly superseding its letterpress counterpart in recent years. Presses tend to be narrow-web, that is to say 200mm (7.5”), 250mm (10”), 360mm (14”), 400 mm (16”) or 450mm (18”).

The process was historically the most popular for printing labels and cartons but some would argue that the process is not as good at delivering quality illustrations in line or half tone format as its competitors.

There are two distinct versions of web-fed letterpress machinery in use in the label and packaging industry.

These are termed semi-rotary intermittent and full rotary. Both processes are web fed but the former process feeds the web intermittently, briefly stopping to allow for die-cutting.

Common impression and stack type letterpress machines are still used in certain markets and applications.

Advantages of letterpress (for security applications)

The process still dominates the print industry in many parts of the emerging and developing world so is readily available to global brand owners that print locally.

In semi-rotary presses waste is reduced both in set-up and running the press since there is a straight though web-path which also allows for register to be maintained more easily. It is also cheaper to produce cutting tools for semi-rotary presses than full rotary machines.

Cutting can be carried out online as can the application of metalized foil which cannot be achieved with litho presses.

Some would argue that there is less skill required to run these presses when compared with other machinery such as litho and gravure.

Disadvantages of letterpress (for security applications) when compared to other printing methods include:

Full rotary letterpress is achieved from standard sets of print cylinders. In order to offer a range of sizes it is necessary to have a wide stock of cylinders and tooling available. This is an expensive investment.

The ink carrying ability and coverage with letterpress is not as good as gravure, neither is the final quality. Dot gain can be a problem too as letterpress plates age and wear. Therefore printing covert security images that require both consistent and accurate dot formation and size is a constraint.

The process is also said to underperform where large areas of a single color are being applied so that uneven coverage results in areas of wash-out.  

Finally letterpress has limitations if optically variable inks are a requirement. The process is not able to carry enough ink weight to enable the dynamic color changes required in brand protection applications.   

FLEXO AND UV FLEXO

There are a few differences between letterpress which uses a raised printing surface and flexo which also delivers print from a elevated surface. The main difference is in the plates, the ink, and in ink metering in order to allow reproduction to take place.

For letterpress printing, viscous drying oil based ink is used whilst the flexo process uses water-based or very fine solvent based ink. For flexographic printing a softer, more flexible plate is used and this meshes with an ink metering system that delivers ink via an engraved anilox roller that carries the ink in thousands of small engraved cells. 

Narrow web flexo is by far the most popular process worldwide for the production of self-adhesive labels. Some estimates put the percentage of installed flexo label presses in the USA at about 75-80% with Europe carrying around 55% of label capacity devoted to flexography.

The process is also popular for the production of wrap-around film labels, shrink sleeves and the printing of flexible packaging, sachets, pot lids, pouches and cartons.

Added to this, it is possible to apply scratch-off panels in order to provide some degree of customer interaction with the label or pack surface. (Such panels when removed by scratching reveal on-pack promotional games, authenticity checks and other consumer interactivity benefits).

The flexo process has been further refined with the introduction of thicker inks that carry more weight (opacity) through deeper cell volumes in the anilox roller and the ability to cure the ink using UV and LED drying systems. Lower dot gain is a benefit delivered by this system as is higher gloss and improved contrast on printed images.

Advantages of flexo and UV flexo (for security applications)

From the plate making to the mounting process, to the transference of the image, flexography is as its name suggests: a versatile and adaptable means of handling large scale reproduction of images and text.

Flexo printing methods involve quick drying in a wide variety of ink types. Depending on the application and surface to be printed upon, users have the choice of five different kinds of ink. Solvent based solutions are ideal for sleeves, flexibles and other commercial uses, while water-based inks work well for more porous materials like carton board.

However self-adhesive constructions and paper/board tend to dominate in this printing technology, where UV flexo is now largely the process of choice.

The process is ideal for printing clear and matt varnishes and especially varnishes that carry a pale optically variable or pearlescent pigment as an overt security device.

Quick evaporation of inks in flexography makes it a safe alternative for flexible food packaging.

Indeed it is important to note that any printer supplying to the food, drink and pharmaceutical sectors of the market is required to employ high standards of hygiene. Not only must staff follow these standards but equipment and the print floor must also comply with strict hygiene standards to ensure that pharmaceuticals and other items for human consumption are not contaminated with harmful substances.

This requirement applies to raw material suppliers too. Inks that comply with food or drug contact regulations may also be required.

Disadvantages of flexo and UV flexo (for security applications)

For long runs of flexible packaging materials gravure printing is considered more economical and is said to offer a higher quality than flexographic alternatives.

Some also say that flexographic printing cannot offer such complexity in artwork and design construction as gravure printing and that the density of color is also not as good. The development of High Density (HD) flexo has gone a long way to overcoming these challenges.

The set up costs for flexography get more expensive the higher the number of colors being printed and long web paths mean some material waste during make ready when compared with digital printing.

SCREEN PRINTING

The image carrier for screen printing is a nylon or metal mesh; either in the form of a cylinder for rotary printing or a flat screen to link-in with say an intermittent letterpress machine. Indeed screen printing is more evident in the labels and packaging market as a combination process system than as a standalone in its own right.

Printing is delivered through photographically exposing the mesh to an image of the label required (color separated of course) and this either leaves holes in the mesh where ink can pass or blocks holes to act as a barrier to ink transfer. In this way the process delivers a ‘screen’ of ink to the substrate.

Today the process is used to print labels (commonly in combination with offset) for high added-value cosmetics and toiletries packaging, as well as pharmaceutical applications such as blister packs. It is possible using this process to achieve a highly controllable coating of ink to the substrate allowing for large areas of color to be applied without ‘wash-out’.

Ultra-thick ink films may also be used to achieve raised effects and/or enable Braille printing.

The process is highly suitable for the application of high quality optically variable inks since the ink weight applied can be varied in order to deliver very pronounced color shifting effects. It can also print a high quality white opaque image, a process other label printing techniques find difficult to deliver.

Advantages of screen printing (for security applications)  

The major advantage of screen printing is its ability to produce large areas of perfect color and if spot colors are used or specific pantone shades are required, it can be difficult for counterfeiters to copy these exactly using other processes. The ability of the screen process to deliver truly optically variable image (OVI’s) effects is also a great strength. It should also be noted that screen printing is able to place a light color over a darker color without discernable loss of quality.

Also the process is flexible enough to be integrated into other print processes (combination presses) as part of a hybrid machine that can deliver a high number of individual colors, say CMYK plus a spot color and an optically variable effect (OVI’s).

The process is ideal for converting stock metalized materials that are used to create cost effective holographic effects as part of the label or carton construction. In these applications a metalized material can be printed with a number of screen colors without any show through. This delivers an eye catching label that carries (a relatively low level) of overt security.

Generally screen inks have a high resistance to fading and can be used with confidence in applications where sensitivity to UV light or where rough handling are important factors. (i.e. labels for use with chemicals, insecticides, paints and other outdoor applications such as power tools).

Disadvantages of screen printing (for security applications)

Flat screen printing is relatively slow and the process as a whole uses a great deal of ink. In security applications where OVI’s are being used to create color change effects the costs can be high if large areas of ink are used for this purpose.

The process is not really suitable or cost effective where quantities over a few hundred thousand are required – unless the label or carton is particularly small.

Screen printing is relatively low in resolution so cannot be used for fine lines, masking hidden images or micro-printing. If these features are required then it is best to consider using a combination machine to print these features first and then overprint with screen in selected areas as a final operation.

GRAVURE PRINTING

This is by and large a simpler printing process than flexo or litho as printing takes place directly from the inked image carrying area (which is cylindrical) and no offset rollers are required to carry the ink to the substrate.

Gravure is not widely used in the narrow web label industry (other than in some coating applications) since it requires low viscosity inks that carry a high solvent content in order to dry them quickly. The solvent is highly flammable and requires a complex and expensive removal process in order to remove the risks of fire and explosion.

The process requires engraved print cylinders that absorb the ink in small cells and cavities that are reproduced used a photo etching process.

Today, these cylinders are covered with print sleeves but previously heavily engraved print cylinders where used which were directly engraved and therefore very costly. 

Consequently the gravure process is more responsive to wide web long run work such as that found in flexible packaging, shrink sleeves and very large quantities of glue applied labels for consumer goods such as those found in the beauty and personal care markets, beer and beverages too.

In these applications, where high numbers of colors are required above the basic CMYK gamut gravure excels, especially if metallic inks are specified. With gravure printing metallic inks carry a high shine and are often difficult to distinguish from metal foil.

This is a prime benefit when such attributes are called for because foil is expensive to apply to small areas and wastage is expensive factor to consider. Metallic inks are also an effective deterrent against copier and scanner attacks since they cannot be replicated photographically.

Because of the ability of the process to deliver controllable depths of ink, the method is also useful to carry thermochromic inks that change color with temperature as well as scented inks and even holographic/pearlescent effect inks that display a prismatic light scattering image when viewed at different angles.

Finally gravure offers photographic quality graphics and the ability to transfer fine detail and skin tones to the substrate. This is because high resolutions are high (up to 1000 LPI) and dot gain is low. 

Advantages of gravure (for security applications)

In security related printing applications, gravure is seen as a process of choice for long runs where there is little likelihood of copy change and the cylinders can be re-used again and again. The ability of the process to carry high resolution images is also an important factor as well as the capability to deliver photochromic and optically variable inks and coatings.

The process is also highly suitable for the transfer of scratch off inks for security applications where covert coding is required. Highly secure scratch off coatings can be achieved using a layer by layer approach where two or more cylinders are used to build up a coating of scratch-off latex. This is why gravure is the process of choice in security applications such as instant lottery tickets.

It is possible to add gravure stations to existing flexo presses if there is a demand for mirror like metallic or other features such as photochromic reactive areas on a label or pack.

Disadvantages of gravure (for security applications)

Where highly solvent inks are required the expense of making the print hall and environment safe from the risk of explosions is a deterrent when compared to other much safer processes. There are also environmental considerations too.

With gravure there is also a costly upfront investment in sleeves which are more expensive to engrave than polymer or litho plates. Most converters find it more cost effective to sub-contract the engraving process and thereby lose flexibility and control in situations where a quick turn-round (or security) is called for.

With many label and carton applications calling for smaller and smaller quantities as brand owners prefer to change designs more frequently and apply just in time stockholdings, gravure is at a disadvantage because it skews in favor of long runs and no-change repeats.

INTAGLIO PRINTING

Associated mainly with high security printing applications such as banknotes, some high value postage stamps (where they are still used), excise stamps and passports, intaglio printing is rarely used outside these fields.

This is because the process is highly controlled by the central banks that print and issue currency at state level and a few independent, long established high security print houses that produce currency on behalf of states that do not have their own dedicated banknote production capabilities.

Intaglio produces a raised tactile print surface from an engraved cylinder like gravure. Indeed both processes are very similar as they deliver very high print quality with low dot gain and when the tactility is added to the process, an overt security feature that involves ‘feeling’ the raised print is provided.

The process tends to use deeper engraving and more viscous inks than gravure in order to deliver this raised effect and to enhance sharpness and tactility further the image is forced into the substrate with a great amount of pressure. Both a doctor blade and a wiping paper are used to remove surplus ink from the engraved print cylinder in order to deliver exact amounts of ink cleanly to the substrate.

It is usual for printers of banknotes to overlay the intaglio print on a foundation of litho background screens. It is also possible to print an intaglio image over the top of foiled security holograms providing a very secure combined security device.

It is conceivable to produce pressure sensitive labels using intaglio but the pressures involved in releasing the ink from such deep recesses in the plate can cause problems with unwanted adhesive egress. That said there are a few label suppliers in North America and security printers in Western Europe that can offer security labels and seals that take advantage of this process.

Advantages of intaglio (for security applications)

Because of its ability to carry high levels of ink, intaglio is ideal for delivering security features such as optically variable inks and latent images. The depth of the ink combined with the shape of the fine line engraving can deliver an effect that allows a latent (hidden) image to be viewed when tilted to light.

Intaglio is also able to produce microscopic lines of type because of the pressures involved, as well as ‘blind’ embossing at the same pass. Intaglio is also capable of delivering excellent split-duct screens.

The main benefit of the process is its relative scarceness, which may be why it is attractive as a process for securing certificates of authenticity and a few very high security applications such as swing tickets for designer goods.

For high volume products such as passports, postage stamps and banknotes where designs may remain unchanged for many years the run-on (repeat) costs associated with platemaking are economic as the plates last for millions of cycles.

Disadvantages of intaglio (for security applications)

The main drawback is that set up costs and origination/engraving require a high initial investment so that small, and even what would be large qualities for other print applications such as flexo, are uneconomic for intaglio.

Because of the high resolutions involved and the depth of engraving it can be a lengthy process creating plates. Since the call for intaglio in the product security sector of the market is so low equipment can be left idle for long periods between jobs.

The process is pretty well confined to a relatively small number of suppliers of machinery, and because of economies of scale the print machines and associated pre-press processes are expensive too.

DIGITAL PRINTING        

Over the past 20 or so years, full color digital printing has evolved to become a major contender in the label and packaging markets where the toner based technologies successfully compete with offset and combination presses in the higher-end markets, and with inkjet challenging flexography in material runs up to around 5,000 linear feet or so.

However this restriction is often invalid when considering digital print for security related applications. 

This is because digital is the only print technology capable of adding secure serialization in visible and digital watermarked format, to labels and packaging.

Granted that numbering boxes can be used to apply serial numbers that can be used to track and trace product in conventional print applications, the fact that this process carries no security and can be easily compromised adds to the attraction that digital offers; the ability to provide personalization, customer interaction and security in the same combined process (see Figure 6.9).

There are almost as many print technologies now available in digital format as there are conventional print techniques. Ink based digital offset (HP), toner based systems (Xeikon – now owned by Flint Group), inkjet printing and heat fusion all conspire to offer attractive options for brand protection applications.

Today, we also find digital present in hybrid presses so that the benefits of conventional and digital print can be combined into a process that embraces the attributes of each technology allowing for high resolution color and graphics to be displayed alongside customer centric functions such as interactivity and authentication. This also includes the ability for a brand owner to enjoy total asset visibility (track & trace) throughout the entire supply chain.

Advantages of digital printing (for security applications) 

The major advantage of digital is that no printing plates are required, so set up is easy with little wastage and the ease of entry it offers into what had previously been a relatively protected market that required high degrees of skill and dexterity to run a printing press.

This means that there is no requirement to invest in a variety of print cylinders because the image produced can be of variable length and no plate gaps are called for. However, there may be a requirement for some additional investment in enhanced pre-press, digital front-end, color management and workflow stages. Good color management is seen as crucial to the success of digital printing.

The introduction of extra colors (beyond CMYK) to the digital tool box means that the color gamut has been further enhanced to compete with conventional print. Add to this, the increases in resolution that have been achieved, now make the process almost comparable quality wise with other traditional forms of printing such as litho, flexography and letterpress.

Of course, the most important ability of digital has been previously mentioned. This is its capacity to provide variable print and graphics, sequential codes and numbers, batch and date codes, personalization, and deliver individual copies of a common design across a range of substrates including pressure sensitive, flexible substrates, metal, carton board and paper.

Disadvantages of digital printing (for security applications)

The main disadvantage of digital is that it runs at lower speeds when compared to flexography and other methods of analogue printing, although running speeds are now significantly improving on the latest generations of digital presses up to 50, 60 or more meters per minute).

However, the speed can be slowed in high resolution jobs by the requirement to print variable images or produce complex jobs where information is called from digital files and then placed within selected print areas on the substrate.

There has historically been a very high cost associated with the acquisition of digital print presses and also a high cost related to consumables.

Furthermore, finishing operations such as waste stripping, die-cutting and foiling until recently needed to be carried out off-line. New developments in automated digital finishing and in laser die-cutting, however, are now enabling increasing numbers of digital presses, particularly the higher-speed inkjet machines, to run with in-line laser die-cutting and digital finishing solutions.

The cost of investing in inkjet is has also come down dramatically in the past few years, with some stand-alone 4-color process inkjet presses now available for purchase for as little as Euro 40,000 (US$ 45,000).

To overcome some disadvantages – such as a restriction on the types of security ink available (i.e. optically variable and photochromics) and its inability to print solid lines – digital in security applications is better confined to combination printing processes where the benefits of both processes combine their better attributes which enhance security further.   

A BRIEF LOOK AT ‘NEAR FUTURE’ PRINT PROCESSES AND THEIR POSSIBLE IMPACT ON SECURITY RELATED LABELS AND PACKAGING

One of the most promising upcoming print processes that is related to smart and security labeling and packaging applications is printed electronics.

This encompasses the production of printed circuits and organic electronics that can be used as various sensors to alert consumers visually to some risks associated with product safety such as unauthorized opening, temperature sensing and authenticity checks.

Printed components can now include simple memory, sensors, logic, displays and the batteries to power these components.

As time progresses it is expected that such technology will find applications in pharmaceutical, food and drink and other packaging-related sectors where tampering and product status such as temperature and humidity control are important factors in product safety.

Whilst smart labels and security applications still only account for one percent of the total packaging and labeling markets they carry forecast growth rates of 15 per cent.

Developers and producers of such innovate products rightly expect better returns on capital invested than they can achieve from mainstream applications alone.

Important to note:

Most of the advantages and disadvantages in the various printing systems listed above are subjective inasmuch as many press manufacturers will argue that their own processes are better than those of their competitors. What is clear however is that there are no known single print processes that are suitable to serve the needs and demands of all the brand protection applications out there, and across every sector of the marketplace.