by Carrie A. Napper, innovation engineer, Klöckner Pentaplast
Credit cards, gift cards, identification and transportation cards, and even hotel key cards are all a vital part of everyday transactions often overlooked in regards to material selection and product performance requirements. Each subsegment has differing requirements in respect to interlaminate strength, printability, durability, etc. And, within each of these subsegment product types, the various manufacturers producing these cards operate slightly differently in terms of equipment, individual process parameters and end-use customer demands.
Can you share a brief overview of construction and the individual steps a basic card will go through?
A standard bank card can be exposed to some or all of the following manufacturing process steps, depending on card design:
Artwork > Pre-Press (proofing, films, plates, screens) > Printing > Sheet Collation > Lamination > Shear Cutting > Punching > Individual Cards > Inspection > Hologram > Signature Panel > Cavity Milling/Chip Embedding > Personalization > Fulfillment
Some of these primary steps are carried out with sublayers of a card prior to a finished, laminated specimen being available in card form. Looking below at the individual sub layers of the example construction will demonstrate how the “pieces” all come together in the lamination step to produce the finished card form.
What types of materials are used in card manufacturing?
Primarily PVC, in various colors and thicknesses, is commonly used. Polyesters of both clear and metallized natures are used for aesthetics and durability enhancements. Polycarbonate, although an expensive option, has been proven to provide some of the best durability offerings. Adhesive layers can range from solvent to water-based, hot melt, urethane, acrylic and numerous combinations thereof. Ink layers and graphics can be composed of UV cure, waterless, conventional and hybrid ink sets.
What types of special effects or materials are used to enhance card features?
Specialty products – such as IR-blocking inks and films, color shift inks and pigments, UV and IR fluorescent inks and pigments, UV screen reflective inks, haptic coatings for touch and feel effect, glitter, pearlescent/metallic inks, and even scents and fragrances – have all been entertained to augment card designs. One of the most popular approaches comes in the form of a metallized PET, with various hologram patterns and designs for that added bling to catch consumers’ eyes.
What is the preferred method of printing in the card industry?
Digital printing is becoming more prominent in the card market due to the shorter run applications with multiple images and customizable graphics. The ability to have every card with a different print pattern isn’t feasible with the more traditional screen printing or offset litho press operations. While screen printing is more economical for large-volume runs of full-bleed color passes, the offset printing process allows the desired image to be transferred from printing plates to the offset cylinder and finally onto the plastic sheets that make up the card structure. The four-process colors of cyan, magenta, yellow and black are mixed in specified ratios to form the final card product with good color resolution. With reusable plates that are easy to produce, resulting in low cost, offset printing remains beneficial for card manufacturers.
With foil card applications being popular for added aesthetic effects, are there any concerns with printing directly to this type of polyester material?
The grades of polyesters selected can vary, but typically there is a pretreatment of sort on the material – whether it is an acrylic chemical treatment, corona or plasma treatment – or a more advanced formulated print-receptive coating that allows the ink to bind to the PET surface with adequate adhesion.
One easily overlooked factor with the introduction of holographic images is the production of the image itself. Some choose to generate the image through an analog process while others choose the digital route of creating a hologram. The digital process allows more control over the pixels, which results in a more brilliant and brighter image.
From a normal visual perspective, one cannot tell a difference – for the most part – between materials produced digitally versus those produced via analog methods. However, with various printing techniques, certain anomalies can occur. There are two main types of screen/litho printing:
- Conventional: uniform spacing in dots, but dots can vary in size
- Stochastic: random spacing in dot and various sizes
With conventional litho printing techniques in combination with a digital hologram, occasionally an effect called moiré can occur. Moiré patterns appear in printing when two or more dots or sets of lines are superimposed at two unique angles, overlapping, negatively interfering with the image. This often creates a visual perception that degrades the quality and resolution of target images. Examples below show two single colors/images overlapped to create a negative effect interfering with the final desired image.
Two approaches can be taken to minimize this effect: First, adjusting the screen angles of the print screens by a small amount can move print dots enough from the interfering cross grain to reduce the visibility of the moiré effect. A second solution could be changing from a conventional print type to a stochastic print with random ink dot spacing.
Customer fitness-for-use qualifications need to be performed to include every process of card manufacturing when introducing a new card material, construction, coating or ink. With many intricate facets and variables of the individual materials and overall card constructions, final product performance in the field can vary.
Carrie Napper is an innovation engineer for Klöckner Pentaplast, a global leader in rigid and flexible packaging, printing and specialty solutions, serving the pharmaceutical, medical device, food, beverage and card markets, among others. With a broad portfolio of packaging, films and services powered by innovation, Klöckner plays an integral role in the customer value chain by marketing and protecting product integrity, safety, consumer health and brand reputation. To learn more about the Klöckner products and markets, visit www.kpfilms.com.