By Josef Feldman and Mark Persinko, Functional Materials Inc.

Driven by growing international demand, card-based products continue to proliferate in a variety of forms. The concept that a card is not just a transaction medium, but also a piece of brand advertising, has been well established in the USA. Today, these marketing concepts are spreading all over the world.

The demand for more advertising impact in graphics, on-demand printing and security features combine to put very stringent technical demands on both the printing substrate and the inks or toners that decorate the surface. Today, there are no stock solutions for printing cards. PVC is still the substrate of choice but ABS, holographic polyester and biodegradable cards have found their place. Lithography and silk screen as ink application methods continue to dominate card production. On-demand printing based on xerography, ink jet and transfer printing are making strong inroads, particularly in the area of customization. In this paper we will highlight some of the impacts of current trends as they relate to inks, coatings and printing methods.

Interface Receptors

The importance of the interface between ink and substrate as well as between ink layers has been discussed at many ICMA symposia (Fig 1). This concept has now become fully integrated into the industry. PVC overlay has been supplied with an adhesive coating for a number of years. Now, we find it increasingly common for a base receptor coating or primer to be supplied with the core substrate. Current commercial products include customized coatings to receive thermal transfer printing; for example, for customized transfer printing of ID photos or bar codes, specialized coated stock that improves adhesion of xerographic toner and inks. Coated core stock is now also being supplied by both PVC and polyester producers. These coatings are also available for printers who can apply them in-line or offline. These coatings allow printers to stay with their current ink and foil formulations and adapt the substrate surface properties to compensate for deficiencies in the substrate or ink properties. The other approach to solving the problem of ink/toner on variable substrate is to customize the ink formulation for the particular substrate. This is a less desirable approach as it involves customizing many ink color formulations.

Impact Graphics

Twenty years ago printing a Gold Card was considered a difficult print job. Printers would not (could not) guarantee the shade of gold or that the color wouldn’t change on storage. With the mass market introduction of the Gold Card in the mid 1980’s by American Express, Visa and MasterCard—with it’s myriad of marketing features—came the demand for a viable method of printing these cards. The development of Gold Eagle® Pigment enabled the use of silk screen printing of a reproducible shade of gold that would not change color upon lamination or exposure to human use. The marketing success of the Gold Card is now history. It is a card with only five colors that consumers visually perceived as having added value, and the card issuers backed up with added value, but could be produced at a reasonable cost.

The high visual impact of the Gold Card spurred the demand for other lustrous colors and special effects. Today, high-end bank, affinity and casino cards are printed with high impact silk screen metallic and pearlescent effects.

Each year there is greater demand for cards with more pizzazz. This has resulted in a large increase in demand for metallic effects with large particle sizes (high brilliance), particularly in the platinum shades. The Platinum card, formerly a very exclusive look, has now become ubiquitous. Printing these larger particle sizes (Table 1) is not without difficulty. Typically one has to use coarse screens (125-160 mesh/in) in order to accommodate free passage of the large particles through the screens. The large screen openings deposit large globs of ink which must now uniformly flow together. The thicker ink layer must also be able to dry quickly. New water-based ink formulations, with good “runnability” and low volatile organic compounds (VOC) emissions to conform with a worldwide environmental movement, were developed to meet these requirements.

These new formulations also allow higher loading of pigment in the inks giving higher opacity and brightness. They also have very high cohesive strength, which in some cases eliminates the need for coated overlay or base primer coats.

Bright Metallics vs. High Resolution

An open dilemma in recent years has been the trend toward bright metallic effects which has forced the use of coarse screens thereby limiting the resolution of the printing. Particularly difficult were reverse-outs. Progress in this area has been made using a combination of a high resolution dark base color with a light pearlescent color on top. The base color is usually printed by lithography. The top pearlescent color, printed by silk screen, has the property that when it is over a dark background it turns from light bright pearlescent to a dark metallic shade. Thus by printing Silver Fox® Pigment over a dark, high resolution pattern one gets a metallic effect where the dark pattern is printed and a bright white over the unprinted areas. Indeed, printing a baseprint in halftones of various dark colorations can have some very great graphical impact.

New developments in water-based fine particle size metallic colors for both screen and anilox in-line applications now allow high brightness luster effects to be printed with high resolution.

Press Ready vs. Ink Mix Room

With the increasing volume of cards, there has been a strong movement toward press ready inks. Printers are always under time pressure in production.

With the ISO9000 emphasis on quality, the pressure is on the mix room to deliver consistent color matched inks.

An increase in demand for press ready inks has resulted. Shelf-life, stable, solvent-based and water-based press ready inks in a variety of metallic and pearlescent shades and particle sizes are now available.

Water-Based Systems

Water-based systems have come a long way. Today because of worldwide concern for VOC’s and the need for high cohesive strength materials in complex card body constructions, water-based adhesive tie layers and primers are widely used around the world. Water-based ink accounts for a major part of the US screen printing of cards and is spreading around the world as products requiring high impact graphics start to be marketed.

Lithography and Topcoating

UV lithographic inks are now a major part of the card market but formulations having good adhesion to a variety of substrates are still problematic. Full-bleed prints still require a coating or use of coated overlay for lamination. Where a coated overlay is not sufficient primers or treated substrates are used.

UV litho metallics still do not give the same lustre effect that solvent-based or water-based systems exhibit. There also continues to be issues with adhesion and cracking of cards on aging. This is particularly true with the thicker ink laydown of metallic UV silkscreen inks.

UV topcoats and press polishing of topcoats, which at one time showed promise of cutting into the overlay market, have lost some appeal. There really is no good substitute, at present, for lamination. With the desire for longer periods between reissue periods, lamination is here to stay for bank cards. However, gloss of UV coatings continue to improve and use of matte UV for GSM cards is well established.